Patent Application
20130058861
The present application is in the field of catalysts for the conversion of fuel-based (both fossil & biomass derived) feedstocks into hydrogen.
One of the advantages of hydrogen gas (H2) as an energy carrier is that it carries a high energy per unit mass (one kg of hydrogen has approximately the same energy content, as that of 1 gallon/2.7 kg of gasoline), thus potentially facilitating energy portability [1]. In addition, pure hydrogen is a non-polluting fuel, producing only water vapor at its point of use, so that pollutants will not be dispersed throughout a hydrogen energy economy but will primarily be localized where hydrogen and other elements of the energy system are produced. Hydrogen can be produced from a wide variety of primary energy sources and different production technologies or processes [2]. At present, nearly all of the worldwide production of hydrogen gas (H2) is from steam reforming of natural gas. This production amounts to approximately 40 billion standard cubic feet per day and is used primarily to manufacture fertilizer, remove sulfur and nitrogen from refined petroleum products, and to manufacture chemicals such as methanol [3]. Secondary uses are in petroleum refineries and in manufacturing processes for chemicals, and metals. Long-term prospects for a hydrogen economy would be significantly increased/improved by the development of processes that are efficient and economically viable on a small scale, so that reforming can be distributed, thereby minimizing the distribution and transportation of hydrogen. Currently there are numerous developmental and demonstration projects that focus on building a hydrogen infrastructure and refueling network for future automobile and other applications [4]. The long-term aim of such projects is to steer towards a zero-emission society. This can be conceived only, when a technology is developed which can deliver hydrogen on site and on demand, i.e., by adopting a decentralize approach to the H2 production problem. This ‘on-site’ production capability will overcome one of the main barriers towards the launching of the hydrogen economy because it addresses the problems related to H2 storage, transportation, and compression for transportation.
There are numerous reforming catalysts (commercial/developmental) available in the markets, which can reform a specific feed to produce hydrogen implying that these are feedstock specific. However, to date the inventors are not aware of any report of catalysts that can be used for the production of hydrogen which are feedstock flexible and/or process flexible. The feedstock referred to here can come from hydrocarbons or oxygenated hydrocarbons (i.e. fossil and biomass sources). In short, no catalyst has been developed for hydrogen production by a catalytic reforming process that is feedstock flexible and/or process flexible.
There is strong interest and advantage in developing novel, highly active, stable catalysts for H2 production from either biomass-derived or fossil fuels-derived sources and making use of any reforming process. The advantages of these catalysts are feedstock flexibility, process flexibility and sustainability.
The catalyst system of the present application makes it possible to easily switch between different feedstocks and processes, without having to change the catalyst. This application therefore relates to the development of a family of catalysts which can reform any hydrocarbon feedstock including short, medium, long chain hydrocarbons, and oxygenated hydrocarbons and mixtures thereof using one or the other of reforming processes such as CO2 reforming, steam reforming, steam-assisted CO2 reforming, partial oxidation, autothermal reforming and combinations thereof for the feedstock. The catalysts developed involves a support made as a solid solution of three or more metal oxides; among the three or more metal oxides, two oxides that are present are ceria and zirconia, while the third or more metal oxide is any metal oxide, including oxides of main group, transition and/or inner-transition metals.
The developed catalysts are made of low cost non-noble active metals supported on high surface area multi-component mixed oxide supports. The catalysts were synthesized using a chemically efficient and optimized synthesis route, thus making them analogous for comparison and further improvisation purposes. The preparation route imparts special characteristics to the catalysts, like thermal stability, high surface area, nanostructure, mesoporosity, complex pore structure, and high oxygen storage/buffer capacity. The presence of ceria in the support is a source of oxygen sink, which together with nano-crystallinity and high metal dispersion, lead to the avoidance of carbon deposition (or coking) during reaction. As a result, the catalysts exhibit excellent durability and adaptability. The selection of the catalyst components, their composition and the specific way the catalysts are synthesized constitutes some of the factors for their superior performance. The catalysts are robust, do not deactivate due to coking, and thus are durable and consequently have very long regeneration and replacement intervals. Also, the catalysts are highly active and can achieve high hydrogen yields. Consequently, the amount of catalyst needed per unit amount of hydrogen produced is small. This implies a reduction of the size of the reactor, which in turn reduces capital expenditure. To the best of the inventors knowledge, this is the first time that a stable catalyst system has been synthesized that can be used to catalyze the generation of hydrogen from any hydrocarbon and oxygenated hydrocarbon feedstock (i.e. is feedstock flexible); and can be employed in any reforming process such as CO2 reforming, steam reforming, steam-assisted CO2 reforming, partial oxidation, and auto thermal reforming (i.e. process flexible). In order to show the unique attributes of the developed catalysts and the contributions of these attributes towards catalyst performance, the developed catalysts were subjected to extensive characterization using state-of-the-art techniques including XPS, NREM, Raman, In situ IR/Operando spectroscopy, TPR, BET SA/PSD, PXRD, OSC, and TG/DSC. The Operando spectroscopy assisted in observing fundamental molecular level measurements of catalyst, reactants, and products under practical reaction conditions. The catalyst structure-activity relationships obtained were used to further improve and fine-tune the catalyst design to obtain the optimal catalyst formulation for industrial/commercial applications. Also, the catalysts were subjected to extended operation cycles under realistic and stimulated feed/operation conditions to test their endurance and performance.
In one aspect, the present application includes a catalyst support of the formula (I):
CeaZrbM1cM2dO2 (I)
wherein
a is about 0.40 to about 0.60;
b is about 0.20 to about 0.40;
c is about 0.05 to about 0.40;
d is 0 to about 0.20
a+b+c+d is about 1; and
M1 and M2 are independently selected from a main group metal, a transition metal and an inner transition metal.
In an embodiment of the present application the catalyst support of formula (I) is prepared using a surfactant assisted method. That is, precursor salts of each of Ce, Zr, M1 and M2 (if present) oxides are dissolved in an aqueous solution and this solution is combined with an aqueous solution comprising of an ionic surfactant. The resulting mixture is then treated with a base to form the support which precipitates from solution forming a slurry. The resulting slurry is hydrothermally aged for a suitable amount of time, then the precipitate is collected by any known means, such as filtration, and the resulting material is dried and calcined. In a further embodiment of the present application, the support of formula (I) is prepared using a surfactant assisted method where the molar ratio of the surfactant to metal oxide precursors is about 0.4 to about 0.6, or about 0.5 or is about 0.6 to about 1.5, or about 1.25.
The present application also includes a catalyst of the formula (II):
Y % Ni/CeaZrbM1cM2dO2 (II)
wherein
Y is about 0.1 to about 10;
a is about 0.40 to about 0.60;
b is about 0.20 to about 0.40;
c is about 0.05 to about 0.40;
d is 0 to about 0.20;
a+b+c+d is about 1; and
M1 and M2 are independently selected from a main group metal, a transition metal and an inner transition metal.
The present application further includes a process for the conversion of a fuel-based feedstock into hydrogen comprising (a) treating a catalyst of the formula (II) as defined above under conditions to reduce NiO to metallic Ni to provide a reduced catalyst; and (b) contacting a reactant comprising a fuel-based feedstock with the reduced catalyst under conditions for the conversion of the fuel-based feedstock into a product comprising hydrogen.
Other features and advantages of the present application will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the application, are given by way of illustration only, since various changes and modifications within the spirit and scope of the application will become apparent to those skilled in the art from this detailed description.
The embodiments of the application will now be described in greater detail with reference to the attached drawings in which:
a shows N2-Isotherms of Ce0.5Zr0.33M10.17M20.0O2 (M=Al, Ba, Ca, Hf, La, Pr, Sm, Sr, Tb & Y) supports prepared with surfactant/metal molar ratio=0.5 in one example of the present application.
b shows N2-Isotherms of 5Ni/Ce0.5Zr0.33M10.17M20.0O2 (M1=Al, Ba, Ca, Hf, La, Pr, Sm, Sr, Tb & Y) catalysts where the supports were prepared with surfactant/metal molar ratio=0.5 in one example of the present application.
c shows N2-Isotherms of Ce0.5Zr0.33M10.17M20.0O2 (M1=Gd & Mg) and Ce0.5Zr0.33Ca0.085Y0.085O2 supports and 5Ni/Ce0.5Zr0.33M10.17M20.0O2 (M1=Ca, Gd, La, Mg, & Y) and 5Ni/Ce0.5Zr0.33Ca0.085Y0.085O2 catalysts where the supports were prepared with surfactant/metal molar ratio=1.25 in one example of the present application.
a shows TPR patterns of Ce0.5Zr0.33M10.17M20.0O2 supports and 5Ni/Ce0.5Zr0.33M10.17M20.0O2 catalysts (M1=Al; Ca, Hf, La, Pr, Sm, Sr, Tb, & Y) where the supports were prepared with surfactant/metal molar ratio=0.5 in certain examples of the present application.
b shows TPR patterns of 5Ni/Ce0.5Zr0.33M10.17M20.0O2 catalysts (M1=Ca, Gd, La, Mg, & Y) where the supports were prepared with surfactant/metal molar ratio=1.25 in certain examples of the present application.
a shows X-ray Photoelectron spectra of Ce0.5Zr0.33M10.17M20.0O2 supports (M1=Ca, Hf, La, Pr, Sm, & Tb) where the supports were prepared with surfactant/metal molar ratio=6.5 in certain examples of the present application.
b shows X-ray Photoelectron spectra of 5Ni/Ce0.5Zr0.33M10.17M20.0O2 catalysts (M1=Ca, Hf, La, Pr, Sm, & Tb) where the supports were prepared with surfactant/metal molar ratio=0.5 in certain examples of the present application.
a shows performance evaluation of titled 5Ni/Ce0.5Zr0.33M10.17M20.0O2 (M1=Al, Ba, Ca, Hf, La, Pr, Sm, Sr, Tb, & Y) and 5Ni/Ce0.5Zr0.33M10.085M20.085O2 (M1=Ca, or La; M2=Y) catalysts, where the supports were prepared with CTAB/metal molar ratio=0.5, for a CO2 reforming of CH4 (T=800° C.; Feed Composition: CH4/CO2/N2=40/40/20 vol. %; Feed flow rate=100 sccm; W/FCH4=1.49 g cat. h/mol.CH4) in certain examples of the present application. The 5Ni/Ce0.6Zr0.4O2 catalysts where the supports were prepared with surfactant/metal molar ratio=0.5 & 1.25 are also included for comparison purposes.
b shows performance evaluation of titled 5Ni/Ce0.5Zr0.33M10.17M20.0O2 (M1=Ca, La, & Y) catalysts where the supports were prepared with CTAB/metal molar ratio=0.5 for a CO2 reforming of CH4 rich natural gas and biogas (T=900° C.; Feed Composition: CH4/CO2/N2=50/40/10 vol. %; Feed flow rate=100 sccm; W/FCH4=1.19 g cat. h/mol.CH4), in certain examples of the present application.
a shows Catalytic Partial Oxidation of Hexadecane (CPOx C16H34) over 5Ni/Ce0.5Zr0.33M10.17M20.0O2 (M1=Al, Ba, Ca, Hf, La, Pr, Sm, Sr, Tb, & Y); 5Ni/Ce0.5Zr0.33M10.085M20.085O2(M1=Ca, or La; M2=Y) catalysts, where the supports were prepared with surfactant/metal molar ratio=0.5, in certain examples of the present application. The 5Ni/Ce0.6Zr0.4O2 catalyst where the support was prepared with surfactant/metal molar ratio=0.5 is also included for comparison purposes.
b shows Catalytic Partial Oxidation of Hexadecane (CPOx C16H34) over 5Ni/Ce0.5Zr0.33M10.17M20.0O2; 5Ni/Ce0.55Zr0.37M10.08M20.0O2; 5Ni/Ce0.41Zr0.27M10.32M20.0O2 (M1=Ca & La); where the supports were prepared with surfactant/metal molar ratio=0.5, in certain examples of the present application.
a shows Catalytic Partial Oxidation of Synthetic Diesel (CPOx SD) over 5Ni/Ce0.5Zr0.33M10.17M20.0O2 (M1=Ca, La, & Y) catalysts, where the supports were prepared with surfactant/metal molar ratio=0.5; and over 5Ni/Ce0.5Zr0.33Ca0.085Y0.085O2 catalyst, where the support was prepared with surfactant/metal molar ratio=1.25, in certain examples of the present application.
b shows Catalytic Partial Oxidation of Synthetic Diesel (CPOx SD) over 5Ni/Ce0.5Zr0.33Ca0.17O2 and 5Ni/Ce0.5Zr0.33Ca0.085Y0.085O2 catalysts, where the supports were prepared with surfactant/metal molar ratios=0.5 & 1.25, in certain examples of the present application.
c shows extended time-on-stream (ToS) stability studied for Catalytic Partial Oxidation of Synthetic Diesel (CPOx SD) over 5Ni/Ce0.5Zr0.33Ca0.17O2 where the support were prepared with surfactant/metal molar ratio=0.5 and over 5Ni/Ce0.5Zr0.33Ca0.085Y0.085O2 catalyst, where the support was prepared with surfactant/metal molar ratio=1.25, in certain examples of the present application.
Unless otherwise indicated, the definitions and embodiments described in this and other sections are intended to be applicable to all embodiments and aspects of the disclosure herein described for which they are suitable as would be understood by a person skilled in the art.
The term “main group metal” as used herein a metal selected from the group, Li, Be, Na, Mg, Al, K, Ca, Ga, Ge, Rb, Sr, In, Sn, Sb, Cs, Ba, TI, Pb and Bi.
The term “transition metal” as used herein means a metal selected from the group Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au and Hg.
The term “inner transition metal” as used herein means a metal selected from the group Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th and Pa.
The term “metal oxide precursors” as used herein refers to any compound comprising the desired metal, M1 or M2, that is converted to a metal oxide under the conditions to form the supports and/or catalysts of the present application. Generally, the metal oxide precursors are salts of the desired metal, such as, but not limited to, nitrate salts, in any form.
The term “suitable” as used herein means that the selection of the particular compound or conditions would depend on the specific synthetic manipulation to be performed, and the identity of the molecule(s) to be transformed, but the selection would be well within the skill of a person trained in the art. All process steps described herein are to be conducted under conditions sufficient to provide the product shown. A person skilled in the art would understand that all reaction conditions, including, for example, reaction solvent, reaction time, reaction temperature, reaction pressure, reactant ratio and whether or not the reaction should be performed under an anhydrous or inert atmosphere, can be varied to optimize the yield of the desired product and it is within their skill to do so.
The terms “a,” “an,” or “the” as used herein not only include aspects with one member, but also includes aspects with more than one member. For example, an embodiment including “a metal” should be understood to present certain aspects with one metal or two or more additional different metals.
As used in this application, the singular forms “a”, “an” and “the” include plural references unless the content clearly dictates otherwise. For example, an embodiment including “a catalyst” should be understood to present certain aspects with one catalyst, or two or more additional catalysts.
In embodiments comprising an “additional” or “second” component, such as an additional or second catalyst, the second component as used herein is chemically different from the other components or first component. A “third” component is different from the other, first, and second components, and further enumerated or “additional” components are similarly different.
In understanding the scope of the present disclosure, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. The term “consisting” and its derivatives, as used herein, are intended to be closed terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The term “consisting essentially of”, as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and/or steps as well as those that do not materially affect the basic and novel characteristic(s) of features, elements, components, groups, integers, and/or steps.
Terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the term it modifies.
A series of ternary oxide and quaternary catalysts were prepared and evaluated for various reforming processes. Representative examples of these catalysts were found to be active and stable for all the reforming processes verifying the “feedstock and process flexible” nature of these catalysts. Thus, feedstock- and process-flexible reforming catalysts for hydrogen and/or syngas production have been developed.
Accordingly, the present application includes a catalyst support of the formula (I):
CeaZrbM1cM2dO2 (I)
wherein
a is about 0.40 to about 0.60;
b is about 0.20 to about 0.40;
c is about 0.05 to about 0.40;
d is 0 to about 0.20;
a+b+c+d is about 1; and
M1 and M2 are independently selected from a main group metal, a transition metal and an inner transition metal.
In an embodiment of the present application, a is about 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59 or 0.60.
In another embodiment of the present application, b is about 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39 or 0.40.
In another embodiment of the present application, c is about 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34 or 0.35, 0.36, 0.37, 0.38, 0.39 or 0.40.
In another embodiment of the present application, when d is 0, c is about 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.10, 0.105, 0.110, 0.115, 0.120, 0.125, 0.130, 0.135, 0.140, 0.145, 0.150, 0.155, 0.160, 0.165, 0.170, 0.175, 0.180, 0.185, 0.190, 0.195, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34 or 0.35, 0.36, 0.37, 0.38, 0.39 or 0.40.
In another embodiment of the present application, when d is greater than 0, c is about 0.05, 0.055, 0.060, 0.065, 0.070, 0.075, 0.080, 0.085, 0.090, 0.095, 0.100, 0.105, 0.110, 0.115, 0.120, 0.125, 0.130, 0.135, 0.140, 0.145, 0.150, 0.155, 0.160, 0.165, 0.170, 0.175, 0.180, 0.185, 0.190, 0.195 or 0.200.
In another embodiment d is about 0, 0.010, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.050, 0.055, 0.060, 0.065, 0.070, 0.075, 0.080, 0.085, 0.090, 0.095, 0.100, 0.105, 0.110, 0.115, 0.120, 0.125, 0.130, 0.135, 0.140, 0.145, 0.150, 0.155, 0.160, 0.165, 0.170, 0.175, 0.180, 0.185, 0.190, 0.195 or 0.200.
In a further embodiment, c and d are the same and are about 0.050, 0.055, 0.060, 0.065, 0.070, 0.075, 0.080, 0.085, 0.090, 0.095, 0.100, 0.105, 0.110, 0.115, 0.120, 0.125, 0.130, 0.135, 0.140, 0.145 or 0.150.
In an embodiment of the application, a is about 0.5, b is about 0.33, c is about 0.17 and d is 0.
In another embodiment of the application, a is about 0.55, b is about 0.37, c is about 0.08 and d is 0.
In another embodiment of the application, a is about 0.41, b is about 0.27, c is about 0.32 and d is 0.
In another embodiment of the application, a is about 0.5, b is about 0.33, c is about 0.085, and d is about 0.085.
In another embodiment of the application M1 and M2 are independently selected from the group Al, Ba, Ca, Gd, Hf, La, Mg, Pr, Sm, Sr, Tb and Y. In a further embodiment M1 and M2 are independently selected from the group Ca, La, Y, Gd and Mg.
In another embodiment of the application, when d is 0, M1 is selected from the group Al, Ba, Ca, Gd, Hf, La, Mg, Pr, Sm, Sr, Tb and Y. In a further embodiment, when d is 0, M1 is selected from the group Ca, La, Y, Gd and Mg.
In another embodiment of the application, when d is greater than 0, M1 and M2 are independently selected from the group Ca, La and Y, for example, in the following combinations CaY, LaY.
In an embodiment of the application, the catalyst supports of formula (I) comprise a cubic or pseudo cubic or tetragonal crystal lattice symmetry.
In an embodiment of the application the catalyst support further comprises an additional one or more different metal oxides selected from main group metals, transition metals or inner transition metals.
In an embodiment of the present application the catalyst support is prepared using a surfactant assisted method. That is, precursor salts of each of Ce, Zr, M1 and M2 (if present) oxides are dissolved in an aqueous solution and this solution is combined with an aqueous solution comprising an ionic surfactant. The resulting mixture is then treated with a base to form the support which precipitates from solution forming a slurry. The resulting slurry is hydrothermally aged for a suitable amount of time, then the precipitate is collected by any known means, such as filtration, and the resulting material is dried and calcined.
In an embodiment of the application the precursor salts of each of the Ce, Zr, M1 and M2 (if present) oxides are nitrate salts.
In an embodiment of the application, the surfactant assisted method, comprises: (i) combining aqueous solutions of precursor salts of each metal oxide, with an aqueous solution of at least one surfactant; (ii) stirring the combination for a suitable time; (iii) adding a suitable base to adjust the pH of the combined solutions to about 10 to about 13 to produce a slurry comprising precipitated support; (iv) allowing the slurry to age at elevated temperatures for a suitable time; (v) isolating the precipitated support from the slurry; (vi) optionally washing the isolated support to remove residual surfactant or solvent and (vii) drying and calcining the isolated support.
In an embodiment if the application, the solutions of metal oxide precursors and surfactant are combined and mixed at room temperature or at elevated temperatures, for example, at about 40° C. to about 80° C. In embodiments of the application, the combined solution is mixed for about 30 to 130 minutes.
In an embodiment of the application, the base used in the surfactant assisted method is aqueous ammonia. More particularly, the pH of the combined solution is adjusted to about 11 to about 12 by the addition of the base. Optionally, the pH of the slurry may be readjusted by the addition of a base after step (iv) above.
In an embodiment of the application, the slurry is aged hydrothermally in a sealed vessel by heating to a temperature of about 80 to about 100° C., suitably about 90° C. Further, in an embodiment of the application, the slurry is aged for about 1 day to about 10 days, suitably, about 3 days to about 6 days. In another embodiment of the invention, the slurry is cooled prior to isolation of the support.
In an embodiment of the application, the precipitated support is separated from the slurry in step (v) above by filtration.
In an embodiment of the application the filtered supports are oven-dried and then calcined. For example, the supports are dried at about 100° C. to about 140° C. for about 6 hours to about 24 hours and then calcined at about 600° C. to about 700° C. for about 1 to about 5 hours. Suitably drying and calcination are carried out in air.
In an embodiment of the application the ionic surfactant is a cationic, anionic, amphoteric or zwitterionic surfactant. In a further embodiment the ionic surfactant is a cationic surfactant. In a further embodiment, the molar ratio of surfactant to metal oxide precursors (surfactant/[Ce+Zr+M1+M2]) is about 0.4 to about 0.6. In a further embodiment, the molar ratio of surfactant to metal oxide precursors (surfactant/[Ce+Zr+M1+M2]) is about 0.6 to about 1.5.
In an embodiment of the application, the ionic surfactant is a cationic surfactant such as a tetraalkyl ammonium salt, in which the length of the alkyl group varies from C6 to C18, in which C6 represents an alkyl group containing six carbon atoms in the alkyl chain and C18 represents an alkyl group containing 18 carbon atoms in the alkyl chain. The alkyl chain is either straight or branched or optionally contains double or triple bonds. Suitably, the length of the alkyl group is C16, which is also known as cetyl or hexadecyl. In an embodiment of the application, the tetraalkylammonium salt is, for example, an alkyltrimethyl ammonium salt, such as an alkyltrimethyl ammonium chloride, bromide or hydroxide. In a further embodiment of the application, the tetraalkylammonium salt is cetyl trimethyl ammonium bromide (CTAB). In an embodiment of the application, the molar ratio of CTAB to metal oxide precursors (CTAB/[Ce+Zr+M1+M2]) is about 0.4 to about 0.6, suitably about 0.5. In an embodiment of the application, the molar ratio of CTAB to metal oxide precursors CTAB/[Ce+Zr+M1+M2]) is about 0.6 to about 1.5, suitably about 1.25.
In another embodiment of the application, the ionic surfactant is an anionic surfactant such as an alkyl sulfate salt (SDS), in which the length of the alkyl group varies from C6 to C18, in which C6 represents an alkyl group containing six carbon atoms in the alkyl chain and C18 represents an alkyl group containing 18 carbon atoms in the alkyl chain. The alkyl chain is either straight or branched or optionally contains double or triple bonds. Suitably, the length of the alkyl group is C12, which is also known as dodecyl. In an embodiment of the application, the alkyl sulfate salt is, for example, sodium dodecyl sulfate (SDS). In an embodiment of the application, the molar ratio of SDS to metal oxide precursors (SDS/[Ce+Zr+M1+M2]) is about 0.4 to about 0.6, suitably about 0.5. In an embodiment of the application, the molar ratio of SDS to metal oxide precursors (SDS/[Ce+Zr+M1+M2]) is about 0.6 to about 1.5, suitably about 1.25.
In a further embodiment the surfactant is an amphoteric surfactant such as cocamidopropyl betaine (CAPB). In an embodiment of the application, the molar ratio of CAPB to metal oxide precursors (CAPB/[Ce+Zr+M1+M2]) is about 0.4 to about 0.6, suitably about 0.5. In an embodiment of the application, the molar ratio of CAPB to metal oxide precursors (CAPB/[Ce+Zr+M1+M2]) is about 0.6 to about 1.5, suitably about 1.25.
In another embodiment of the application, the surfactant for preparing the support is oligomeric and includes co-polymers such as pluronics. These amphiphilic polymers comprise polypropylene oxide block (PO) which is surrounded by two hydrophilic polyethylene oxide blocks (EO). The general formula of the amphiphilic polymer is represented as (EO)a-(PO)b-(EO)c. There are a number of different pluronics which are available, each with a different molecular weight and a EO/PO molar ratio. In a specific embodiment of the application, the triblock copolymer Pluronic™ 123 (P-123) is used, which has the schematic structure of (EO)20-(PO)70-(EO)20.
In an embodiment of the application, the catalyst support of formula (I) is selected from:
Ce0.5Zr0.33M10.17M20.0O2,
wherein M1 is selected from La, Al, Ba, Ca, Hf, Pr, Sm, Sr, Tb, Gd, Mg and Y;
Ce0.55Zr0.37M10.08M20.0O2,
wherein M1 is selected from La and Ca; and
Ce0.41Zr0.27M10.32M20.0O2,
wherein M1 is selected from La and Ca;
In a further embodiment, the support is prepared using a surfactant assisted method where the molar ratio of the surfactant to metal oxide precursors is about 0.4 to about 0.6, or about 0.5 or is about 0.6 to about 1.5, or about 1.25.
In another embodiment, the catalyst support of formula (I) is selected from:
Ce0.5Zr0.33M10.085M20.085O2,
wherein M1 is selected from Ca, or La; and M2 is selected from Y;
In a further embodiment, the support for the above catalysts is prepared using a surfactant assisted method where the molar ratio of the surfactant to metal oxide precursors is about 0.4 to about 0.6, or about 0.5 or is about 0.6 to about 1.5, or about 1.25.
The present application also includes a catalyst of the formula (II):
Y % Ni/CeaZrbM1cM2dO2 (II)
wherein
Y is about 1.0 to about 10.0;
a is about 0.40 to about 0.60;
b is about 0.20 to about 0.40;
c is about 0.05 to about 0.40;
d is 0 to about 0.20;
a+b+c+d is about 1; and
M1 and M2 are independently selected from a main group metal, a transition metal and an inner transition metal.
In embodiment of the application, Y is about 1 to about 8, about 2 to about 7, about 3 to 6 or about 5. In another embodiment Y is about 5. The value Y, is the percent, by weight of the catalyst, of nickel present in the catalyst.
The CeaZrbM1cM2dO2 in the catalysts of formula (II) is the support of formula (I) as defined above and prepared using the surfactant assisted method, also described above. Accordingly, the embodiments for the values of a, b, c, d, M1 and M2 are as defined above.
In an embodiment of the application, the catalyst of formula (II) is selected from:
5% Ni/Ce0.5Zr0.33M10.17M20.0O2,
wherein M1 is selected from La, Al, Ba, Ca, Hf, Pr, Sm, Sr, Tb, Gd, Mg and Y;
5% Ni/Ce0.55Zr0.37M10.08M20.0O2,
wherein M1 is selected from La and Ca; and
5% Ni/Ce0.41Zr0.27M10.32M20.0O2,
wherein M1 is selected from La and Ca;
In a further embodiment, the support for the above catalysts is prepared using a surfactant assisted method where the molar ratio of the surfactant to metal oxide precursors is about 0.4 to about 0.6, or about 0.5 or is about 0.6 to about 1.5, or about 1.25.
In another embodiment, the catalyst of formula (II) is selected from:
5% Ni/Ce0.5Zr0.33M10.085M20.085O2,
wherein M1 is selected from Ca, & La; and M2 is selected from Y;
In a further embodiment, the support for the above catalysts is prepared using a surfactant assisted method where the molar ratio of the surfactant to metal oxide precursors is about 0.4 to about 0.6, or about 0.5 or is about 0.6 to about 1.5, or about 1.25.
In an embodiment of the application, the Ni is added to the support using a wet impregnation method. For example the supports of formula (I) are immersed in an aqueous solution of a Ni salt, such as Ni(NO3)2 and the resulting mixture stirred and slowly heated under conditions, for example in a hot water bath, to remove excess water (i.e. dried). In an embodiment, the dried catalysts are calcined, for example, at about 600° C. to about 700° C. for about 1 to about 5 hours. Suitably drying and calcined are carried out in air.
The present application further includes a process for the conversion of a fuel-based feedstock into hydrogen comprising (a) treating a catalysts of the formula (II) as defined above under conditions to reduce NiO to metallic Ni to provide a reduced catalyst; and (b) contacting a reactant comprising the fuel-based feedstock with the reduced catalyst under conditions for the conversion of the fuel-based feedstock into a product comprising hydrogen.
In an embodiment of the application the catalysts of the formula (II) are reduced in situ during the course of the process to reduce the NiO species to metallic Ni species. In a further embodiment, the conditions to reduce NiO to metallic Ni to provide a reduced catalyst comprise a temperature of about 650° C. to about 750° C., for example about 700° C., in flowing H2 (about 1% to about 10%, for example about 5%, with the balance being N2).
The fuel-based feedstock is, for example, but not limited to short chain, medium chain and long chain hydrocarbons (e.g., natural gas, gasoline, diesel), oxygenated hydrocarbons and their mixtures (e.g. glycerol, ethanol, biomass derived fuels) or biogas.
The conditions for the conversion of the reactant comprising fuel-based feedstock to product comprising H2 are any known reforming process for these feedstocks, including, but not limited to CO2 reforming of methane and other hydrocarbons, partial oxidation of gasoline, partial oxidation of diesel, partial oxidation of other hydrocarbons and their mixtures, autothermal reforming of diesel and other hydrocarbons, steam assisted CO2 reforming of methane and other hydrocarbons or their mixtures, steam reforming of methane or other hydrocarbons and their mixtures, gas phase steam reforming of oxygenated hydrocarbons and their mixtures, as well as a combination of these reforming processes.
In an embodiment, the reactant further comprises other reactants for performing the reforming reaction on the fuel-based feedstock to produce a product comprising hydrogen.
In an embodiment of the reaction, the product comprising hydrogen further comprises carbon dioxide, carbon monoxide and/or water. When the product comprises hydrogen and carbon monoxide, this mixture is known as syngas.
In an embodiment of the application, the reforming reaction is dry reforming of methane or other hydrocarbons and the reactant comprises the hydrocarbon(s) and carbon dioxide (CO2) and the conditions for the conversion of the fuel-based feedstock into a product comprising hydrogen comprise a temperature of about 700° C. to about 900° C. at a pressure of 1 atm. In an embodiment, the molar ratio of hydrocarbon(s) to CO2 is about 1:1, in another embodiment, the molar ration of hydrocarbon(s) to CO2 is about 1.25:1.
In an embodiment of the application, the reforming reaction is steam reforming of methane or other hydrocarbons and the reactant comprises the hydrocarbon(s), carbon dioxide and water and the conditions for the conversion of the fuel-based feedstock into a product comprising hydrogen comprise a temperature of about 700° C. to about 900° C. at a pressure of 1 atm. In an embodiment, the molar ratio of hydrocarbon(s) to CO2 to water is about 1:1:1.
In an embodiment of the application, the reforming reaction is partial oxidation of hexadecane or other hydrocarbons and the reactant comprises the hydrocarbon(s) and oxygen and the conditions for the conversion of the fuel-based feedstock into a product comprising hydrogen comprise a temperature of about 750° C. to about 950° C. at a pressure of 1 atm. In an embodiment, the molar ratio of O2/C (where C is the total moles of carbon in the hydrocarbon) is about 0.5.
In an embodiment of the application, the reforming reaction is partial oxidation of synthetic gasoline and the reactant comprises the gasoline and oxygen and the conditions for the conversion of the fuel-based feedstock into a product comprising hydrogen comprise a temperature of about 750° C. to about 950° C. at a pressure of 1 atm. In an embodiment, the molar ratio of O2/C is about 0.5.
In an embodiment of the application, the reforming reaction is partial oxidation of synthetic diesel and the reactant comprises the diesel and oxygen and the conditions for the conversion of the fuel-based feedstock into a product comprising hydrogen comprise a temperature of about 750° C. to about 950° C. at a pressure of 1 atm. In an embodiment, the molar ratio of O2/C is about 0.75.
In an embodiment of the application, the reforming reaction is steam reforming of a liquid mixture of oxygenated hydrocarbons and the reactant comprises the liquid mixture, and water and the conditions for the conversion of the fuel-based feedstock into a product comprising hydrogen comprise a temperature of about 500° C. to about 700° C. at a pressure of 1 atm. In an embodiment, the amount of water needed is calculated based on the stoichiometry required for reaction with the specific oxygenated hydrocarbons in the mixture. In another embodiment, two times the amount of water needed for the stoichiometric reaction with the specific oxygenated hydrocarbons in the mixture was used.
In an embodiment, the catalysts of formula (II) are mixed with an inert diluent, for example, but not limited to, α-Al2O3.
In an embodiment of the application, the process is performed as a continuous process where the reactant comprising fuel-based feedstock is in the form of a gaseous, liquid or vaporized input stream and the hydrogen product is comprised in an output stream that is optionally treated using known methods to separate and purify the hydrogen gas for use as a fuel or any other known purpose (such as a reactant in chemical synthesis). In this embodiment, the catalyst is packed or housed in a packed bed tubular reactor (PBTR) and the input stream is passed through the PBTR.
The following non-limiting examples are illustrative of the present application:
The synthetic route employed in the study, is based on a modification of a ‘surfactant assisted route’ used by Idem et al. [2006] for binary oxide supports [21], wherein nitrate salts of different metal ions were hydrolyzed together along with a surfactant (CTAB) under basic conditions, and subsequently aged hydrothermally under autogenous pressure at 90° C. for 60 h. The CTAB/[Ce+Zr] ratio of 1.25 was used in the previous report [21]. In most of the current work, the surfactant (CTAB) usage is significantly reduced by a factor of 2.5 for the purpose of minimizing wastes generated during catalyst making. This represents a much improved and optimized version of the previous recipe [21]. Binary oxide supports (Ce0.6Zr0.4O2) with CTAB/[Ce+Zr] molar ratios 0.5 and 1.25 were also prepared in the current study for comparison purposes. The two binary oxide supports prepared using two different CTAB/[Ce+Zr] ratios are abbreviated as CZ(1.25) and CZ(0.5) respectively. The third oxide in the ternary oxide support system (I) was used because the binary system, irrespective of CTAB/[Ce+Zr] ratio was unable to support the feed flexibility and process flexibility envisaged in the present application. The third and fourth oxides in the quarternary oxide support system (II) was used because the binary system, irrespective of CTAB/[Ce+Zr] ratio was unable to support the feed flexibility and process flexibility envisaged in the present application. A comparative analysis of their (binary oxides vs ternary oxides and quarternary oxides) relative performance and inherent structural/physico-chemical characteristics sheds light on the scientific basis for the superior behavior of ternary oxide and quarternary oxide catalysts over their binary oxide counterparts. All the preparations described below are normalized to yield 15 g catalysts per batch/preparation. The nominal compositions achieved in the ternary oxide supports were Ce0.5Zr0.33M10.17M20.0O2 (where M1=Al, Ba, Ca, Hf, La, Pr, Sm, Sr, Tb, & Y); Ce0.55Zr0.37M10.08M20.0O2 (where M1=Ca, & La); Ce0.41Zr0.27M10.32M20.0O2 (where M1=Ca, & La) with a CTAB/[Ce+Zr+M1+M2] molar ratio ˜0.5 and Ce0.5Zr0.33 M10.17M20.0O2 (where M1=Ca, Gd, La, Mg, & Y) with a CTAB/[Ce+Zr+M1+M2] molar ratio ˜1.25. The nominal compositions achieved in the quarternary oxide supports were Ce0.5Zr0.33M10.085M20.085O2 (M1=Ca or La; M2=Y) with a CTAB/[Ce+Zr+M1+M2] molar ratio ˜0.5 and Ce0.5Zr0.33M10.085M20.085O2 (M1=Ca; M2=Y) with a CTAB/[Ce+Zr+M1+M2] molar ratio ˜1.25. It is notable that all catalysts reported herein were prepared by analogous procedures, which was necessary to allow direct comparison of their catalytic properties.
a. Preparation of Ce0.5Zr0.33Al0.17O2 Catalyst Support
The Ce0.5Zr0.33Al0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20], and Aluminum nitrate nonahydrate [Al(NO3)3.9H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Al3+ cations to prepare the above catalyst. In a typical preparation, 22.8 g of Ce(NO3)3.6H20, 8.0 g of ZrO(NO3)2.xH20 and 6.3 g of Al(NO3)3.9H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 18.8 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Al] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Al3+ was achieved through the current preparation route.
b. Preparation of Ce0.5Zr0.33Ba0.17O2 Catalyst Support
The Ce0.5Zr0.33Ba0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Barium nitrate [Ba(NO3)2] precursors were employed as a source of Ce3+/4+, Zr4+, and Ba2+ cations to prepare the above catalyst. In a typical preparation, 21.5 g of Ce(NO3)3.6H20, 7.6 g of ZrO(NO3)2.xH20 and 4.14 g of Ba(NO3)2, were dissolved separately in deionized water and mixed together. In a separate beaker, 18.0 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Ba] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Ba2+ was achieved through the current preparation route.
c. Preparation of Ce0.5Zr0.33Ca0.17O2, Ce0.55Zr0.37Ca0.08O2, Ce0.41Zr0.27Ca0.32O2Catalyst Supports
The Ce0.5Zr0.33Ca0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Calcium nitrate tetrahydrate [Ca(NO3)2.4H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Ca2+ cations to prepare the above catalyst. In a typical preparation, 23.9 g of Ce(NO3)3.6H20, 8.5 g of ZrO(NO3)2.xH20 and 4.34 g of Ca(NO3)2.4H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 20.0 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Ca] was kept constant at ≅0.5. In order to prepare [CTAB]/[Ce+Zr+Ca]=1.25, 50 g of surfactant-CTAB was used. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Ca2+ was achieved through the current preparation route.
The Ce0.55Zr0.37Ca0.08O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Calcium nitrate tetrahydrate [Ca(NO3)2.4H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Ca2+ cations to prepare the above catalyst. In a typical preparation, 24.7 g of Ce(NO3)3.6H20, 8.9 g of ZrO(NO3)2.xH20 and 2.0 g of Ca(NO3)2.4H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 18.8 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Ca] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Ca2+ was achieved through the current preparation route.
The Ce0.41Zr0.27Ca0.32O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexa hydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Calcium nitrate tetrahydrate [Ca(NO3)2.4H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Ca2+ cations to prepare the above catalyst. In a typical preparation, 21.9 g of Ce(NO3)3.6H20, 7.7 g of ZrO(NO3)2.xH20 and 9.3 g of Ca(NO3)2.4H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 22.4 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Ca] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Ca2+ was achieved through the current preparation route.
d. Preparation of Ce0.5Zr0.33Gd0.17O2Catalyst Support
The Ce0.5Zr0.33Gd0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Gadolinium nitrate hexahydrate [Gd(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Gd3+ cations to prepare the above catalyst. In a typical preparation, 20.8 g of Ce(NO3)3.6H20, 7.3 g of ZrO(NO3)2.xH20 and 5.45 g of Gd(NO3)3.2H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 17.35 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Gd] was kept constant at ≅0.5. In order to prepare [CTAB]/[Ce+Zr+Gd]=1.25, 43.4 g of surfactant-CTAB was used. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Gd3+ was achieved through the current preparation route.
e. Preparation of Ce0.5Zr0.33Hf0.17O2 Catalyst Support
The Ce0.5Zr0.33Hf0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Hafnium oxynitrate [HfO(NO3)2.xH20] precursors were employed as a source of Ce3+/4+, Zr4+, and Hf4+ cations to prepare the above catalyst. In a typical preparation, 20.1 g of Ce(NO3)3.6H20, 7.1 g of ZrO(NO3)2.xH20 and 9.11 ml of HfO(NO3)2 solution, were dissolved separately in deionized water and mixed together. In a separate beaker, 16.8 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Hf] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Hf4+ was achieved through the current preparation route.
f. Preparation of Ce0.5Zr0.33La0.17O2, Ce0.55Zr0.37La0.08O2, Ce0.41Zr0.27La0.32O2 Catalyst Supports
The Ce0.5Zr0.33La0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Lanthanum nitrate hexahydrate [La(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, and La3+ cations to prepare the above catalyst. In a typical preparation, 21.1 g of Ce(NO3)3.6H20, 7.5 g of ZrO(NO3)2.xH20 and 7.0 g of La(NO3)3.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 17.7 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+La] was kept constant at ≅0.5. In order to prepare [CTAB]/[Ce+Zr+La]=1.25, 44.25 g of surfactant-CTAB was used. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & La3+ was achieved through the current preparation route.
The Ce0.55Zr0.37La0.08O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Lanthanum nitrate hexahydrate [La(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr44-, and La3+ cations to prepare the above catalyst. In a typical preparation, 23.4 g of Ce(NO3)3.6H20, 8.4 g of ZrO(NO3)2.xH20 and 3.4 g of La(NO3)3.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 17.8 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+La] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & La3+ was achieved through the current preparation route.
The Ce0.41Zr0.27La0.32O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Lanthanum nitrate hexahydrate [La(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, and La3+ cations to prepare the above catalyst. In a typical preparation, 17.15 g of Ce(NO3)3.6H20, 6.0 g of ZrO(NO3)2.xH20 and 7.0 g of La(NO3)3.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 13.4 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+La] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & La3+ was achieved through the current preparation route.
g. Preparation of Ce0.5Zr0.33Mg0.17O2 Catalyst Support
The Ce0.5Zr0.33Mg0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Magnesium nitrate hexahydrate [Mg(NO3)2.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Mg2+ cations to prepare the above catalyst. In a typical preparation, 24.7 g of Ce(NO3)3.6H20, 9.3 g of ZrO(NO3)2.xH20 and 4.6 g of Mg(NO3)2.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 20.3 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Mg] was kept constant at ≅0.5. In order to prepare [CTAB]/[Ce+Zr+Mg]=1.25, 50.8 g of surfactant-CTAB was used. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Mg2+ was achieved through the current preparation route.
h. Preparation of Ce0.5Zr0.33Pr0.17O2 Catalyst Support
The Ce0.5Zr0.33Pr0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Preseodymium nitrate hexahydrate [Pr(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Pr3+ cations to prepare the above catalyst. In a typical preparation, 21.1 g of Ce(NO3)3.6H20, 7.5 g of ZrO(NO3)2.xH20 and 7.0 g of Pr(NO3)3.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 17.7 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Pr] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4÷, & Pr3+ was achieved through the current preparation route.
i. Preparation of Ce0.5Zr0.33Sm0.17O2 Catalyst Support
The Ce0.5Zr0.33Sm0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Samarium nitrate hexahydrate [Sm(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Sm3+ cations to prepare the above catalyst. In a typical preparation, 20.85 g of Ce(NO3)3.6H20, 7.35 g of ZrO(NO3)2.xH20 and 7.05 g of Sm(NO3)3.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 17.5 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Sm] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Sm3+ was achieved through the current preparation route.
j. Preparation of Ce0.5Zr0.33Sr0.17O2 Catalyst Support
The Ce0.5Zr0.33Sr0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Strontium nitrate [Sr(NO3)2] precursors were employed as a source of Ce3+/4+, Zr4+, and Sr2+ cations to prepare the above catalyst. In a typical preparation, 22.8 g of Ce(NO3)3.6H20, 8.0 g of ZrO(NO3)2.xH20 and 3.555 g of Sr(NO3)2, were dissolved separately in deionized water and mixed together. In a separate beaker, 18.8 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Sr] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Sr2+ was achieved through the current preparation route.
k. Preparation of Ce0.5Zr0.33Tb0.17O2 Catalyst Support
The Ce0.5Zr0.33Tb0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Terbium nitrate hexahydrate [Tb(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Tb3+ cations to prepare the above catalyst. In a typical preparation, 20.6 g of Ce(NO3)3.6H20, 7.3 g of ZrO(NO3)2.xH20 and 5.43 g of Tb(NO3)3.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 17.5 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Tb] was kept constant at ≅0.5. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Tb3+ was achieved through the current preparation route.
l. Preparation of Ce0.5Zr0.33Y0.17O2 Catalyst Support
The Ce0.5Zr0.33Y0.17O2 ternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; and Yttrium nitrate hexahydrate [Y(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, and Y3+ cations to prepare the above catalyst. In a typical preparation, 22.3 g of Ce(NO3)3.6H20, 7.9 g of ZrO(NO3)2.xH20 and 6.54 g of Y(NO3)3.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 18.7 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Y] was kept constant at ≅0.5. In order to prepare [CTAB]/[Ce+Zr+Y]=1.25, 46.75 g of surfactant-CTAB was used. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, & Y3+ was achieved through the current preparation route.
m. Preparation of Ce0.5Zr0.33Ca0.085Y0.085O2 Catalyst Support
The Ce0.5Zr0.33Ca0.085Y0.085O2quarternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; Calcium nitrate tetrahydrate [Ca(NO3)2.4H20]; and Yttrium nitrate hexahydrate [Y(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, Ca2+ and Y3+ cations to prepare the above catalyst. In a typical preparation, 23.2 g of Ce(NO3)3.6H20, 8.2 g of ZrO(NO3)2.xH20, 2.0 g Ca(NO3)2.4H20 and 3.3 g of Y(NO3)3.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 19.5 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+Ca+Y] was kept constant at ≅0.5. In order to prepare [CTAB]/[Ce+Zr+Ca+Y]=1.25, 48.75 g of surfactant-CTAB was used. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, Ca2+& Y3+ was achieved through the current preparation route.
n. Preparation of Ce0.5Zr0.33La0.085Y0.085O2 Catalyst Support
The Ce0.5Zr0.33La0.085Y0.085O2quarternary metal oxide support was prepared by “surfactant assisted route” under basic conditions. Cerium (III) nitrate hexahydrate [Ce(NO3)3.6H20]; Zirconium oxynitrate [ZrO(NO3)2.xH20]; Lanthanum nitrate hexahydrate [La(NO3)3.6H20]; and Yttrium nitrate hexahydrate [Y(NO3)3.6H20] precursors were employed as a source of Ce3+/4+, Zr4+, La3+ and Y3+ cations to prepare the above catalyst. In a typical preparation, 21.9 g of Ce(NO3)3.6H20, 7.7 g of ZrO(NO3)2.xH20, 3.5 g La(NO3)3.6H20 and 3.1 g of Y(NO3)3.6H20, were dissolved separately in deionized water and mixed together. In a separate beaker, 18.3 g of surfactant-cetyl trimethylammonium bromide (CTAB) was dissolved in DI water at 60° C. The above two solutions were mixed together to obtain a resultant mixture solution. The molar ratio of [CTAB]/[Ce+Zr+La+Y] was kept constant at ≅0.5. In order to prepare [CTAB]/[Ce+Zr+La+Y]=1.25, 45.75 g of surfactant-CTAB was used. Aqueous ammonia (25 vol. %) was gradually added to the aforementioned mixture solutions under vigorous stirring until precipitation was complete (pH 11.8). The addition of ammonia induced the precipitation of gelatinous yellow-brown colloidal slurry. The slurry was stirred for 60 min in a glass reactor, subsequently transferred into pyrex glass bottles, sealed and aged “hydrothermally” in an air circulated oven for 5 days at 90° C. After which, the mixture was cooled and the resulting precipitate was filtered and washed repeatedly with warm DI water. The resulting cakes were oven-dried at 120° C. for 12 h and finally calcined at 650° C. for 3 h in air environment. Formation of a solid solution between Ce4+/3+, Zr4+, La3+& Y3+ was achieved through the current preparation route.
A nominal 5 wt. % Ni was loaded over the above-prepared supports (I) (refer to paragraph [00100]) by standard wet impregnation method. Similarly the binary oxide supports CZ(0.5) and CZ(1.25) were also impregnated by same procedure to yield corresponding catalysts i.e., NZC(0.5) and NCZ(1.25). In a typical impregnation 14.25 g of catalyst support (I) is immersed in 127.75 ml of 0.1 M Ni(NO3)2 solution. The mixture was subjected to slow heating under constant stirring in a hot water bath, so as to remove the excess water; the dried powders thus obtained were calcined at 650° C. in air for 3 h. The calcined catalysts are reduced in situ during the course of reaction in order to reduce the NiO species to metallic Ni species. The reduction is carried out at 700° C. in flowing 5% H2/bal.N2.
a. Surface Area and Pore Size Distribution Analysis
The BET surface area and pore size distribution analyses for all catalysts were obtained by N2 physisorption at liquid N2 temperature using a Micromeritics ASAP 2010 apparatus. Prior to analysis, all the samples were degassed for 6 h at 180° C. under vacuum. Pore size distribution and average pore volume were analyzed using the desorption branch of the N2-isotherm. Each sample was analyzed by N2 physisorption at least twice in order to establish repeatability. The error in these measurements was ≦1%.
b. XRD Measurements
Powder XRD patterns were recorded on a Bruker Discover diffractometer using nickel-filtered CuKα (0.154056 nm) as the radiation source. The intensity data were collected over a 2θ range of 10-90° with a step size of 0.02° using a counting time of 1 s per point. Crystalline phases were identified through comparison with the reference data from ICDD files [22].
c. TPR Measurements
H2-TPR of various catalyst samples was performed on a Quantachrome ChemBET 3000 unit equipped with a thermal conductivity detector (TCD). For all the samples (except pristine NiO) investigated by TPR, exactly same amount was analyzed, so as to make comparison possible. Prior to TPR measurements, the samples were degassed at 180° C. in an inert atmosphere (N2 UHP grade) for 2 h. The reducibility of the supports as well as that of catalysts prepared in the current study, were studied by TPR technique in the temperature range from ambient to 1050° C. at a heating rate of 15° C./min, using 5% H2/bal. N2 as the reactive gas (flow rate=45 sccm). The total reactive gas consumed during TPR analysis was measured. The H2 uptake as a function of TCD response vs. temperature was plotted. A few samples were analyzed by TPR at least twice in order to establish reproducibility. The error in Tmax values was found to be less than ±4° C.
d. Raman Analysis
The Raman analyses were performed on a Renishaw inVia Raman Microscope using a Ar+ laser (Spectra Physics) operating at 514.5 nm. The laser beam (10 mW at the laser) was focused onto a pelletized sample using a Leica 20×NPLAN objective (NA=0.40). The Raman spectra were acquired using a 10 s detector acquisition time, and the spectra were accumulated to achieve sufficient signal-to-noise intensities. The spectra were baseline corrected using the Renishaw Wire V3.1 software provided with the instrument. The wavenumbers obtained from spectra are accurate to within 2 cm−1.
e. XPS Measurements
The XPS measurements were performed on a Leybold MAX 200 X-ray Photoelectron Spectrometer using Al Kα (1487 eV) radiation as the excitation source. Charging of the catalyst samples was corrected by setting the binding energy of the adventitious carbon (C 1 s) at 285 eV [23,24]. The XPS analysis was performed at ambient temperature and at pressures typically on the order of <10−9 torr. Pass energies of 192 and 48 eV were used for survey scan and narrow scan measurements respectively. All binding energies quoted in this study were measured within a precision of ±0.1 eV. The quantitative surface atomic composition was determined by standard methods.
f. Oxygen Storage Properties (OSC)
The oxygen storage capacity (OSC) of the support powders was measured on a thermogravimetric analyzer under cyclic reductive and oxidative excursions. A known amount of sample (˜50 mg) was loaded into the TGA (Setaram TG/DSC111). The sample was subjected to reduction/oxidation cycles at 800° C. using the following gas mixtures 5% H2 in bal.N2 and 5% O2 in bal.N2, respectively. Prior to every experiment, the sample was heated to 800° C. in inert atmosphere (N2 UHP) at a ramp rate of 15° C./min and maintained at 800° C. for 1 h, after which the cyclic reduction/oxidation was carried out for 1 h each at 800° C. The flow rate of all the gas mixtures was maintained constant at 30 sccm. The weight loss during reduction cycle and weight gain during oxidation cycle was used to calculate the total OSC of the support powders. The OSC tests were repeated thrice on each sample, in order to establish concurrence and it was found to be precise within the limit of ±2% error.[24]. The OSC experiments were performed in a thermogravimetric analyzer (TGA), under cyclic reductive and oxidative excursions. The OSC experiments were carried out at 800° C., at which a known amount of sample is subjected to cyclic reduction and oxidation by switching the reactive gas from 5% H2/bal.N2 to 5% O2/bal.N2 respectively. The weight loss during reduction cycle and weight gained during oxidation cycle was monitored by TGA and used to calculate the total OSC of the powders. This technique of OSC evaluation is essentially similar to that described previously [25].
g. High Resolution Electron Microscopy (NREM)
The high resolution transmission electron microscopy (HRTEM) study was performed using a JEOL JEM-2100F field emission transmission electron microscope equipped with an ultra high resolution pole-piece (lattice resolution 0.1 nm). The images were acquired at with acceleration voltage of 200 kV. TEM specimens were prepared by placing microdrops of nano-particle solution onto a copper grid coated with carbon film (300 mesh, EMS).
h. Metallic Surface Area and Metal Dispersion Measurements
The metallic surface area and metal dispersion in the catalyst samples were estimated by hydrogen chemisorption at 35° C. using a Micromeritics ASAP 2010C instrument. Prior to analyses, the catalyst samples were dried at 120° C., and then reduced in situ in flowing H2 gas (UHP grade) at 700° C. for 3 h (in order to mimic the reduced state formed during the course of a typical catalytic run) followed by evacuation at 700° C. for 1 h before cooling down to 35° C. The metallic surface area (SNi) was calculated with the help of the following expression:
SNi=13.58×10−20 NM (m2/g-cat.)
Where NM is the number of hydrogen molecules adsorbed in the monolayer per gram of catalyst. The above expression was derived by considering the surface occupied per atom of nickel as 6.49 Å2 per atom (considering the density of nickel as 8.91 g/cm3 and a face-centered cubic lattice) and the adsorption stoichiometry as 2 surface nickel atoms per hydrogen molecule. The nickel dispersion (D %) was then calculated as the percentage of surface nickel atoms with respect to total nickel atoms in the catalysts [26]. The H2 chemisorption analysis was repeated for a few of the samples in order to check reproducibility. The error in these measurements was <1%.
Activity evaluation studies were carried out in a packed bed tubular reactor (PBTR) (½″ I.D.) made of Inconel 625. The reactor was placed vertically inside a programmable tubular furnace (Zesta Engineering), which was heated electrically. The selection of reduction temperature was based on the maximum Tmax obtained for Ni from TPR experiments. All the gases were regulated through precalibrated mass (gas) flow controllers with a digital readout unit (Aalborg Instruments). The catalyst bed temperature was measured by means of a sliding thermocouple dipped inside the catalyst bed. Prior to each run, the catalyst was activated in situ by reducing it at 700° C. for 2-3 h using a gas mixture of 5 vol. % H2 in N2 (flow rate=100 sccm). The catalyst pretreatment involved the partial reduction of nickel oxide (NiO) to metallic nickel species (Ni). The activity evaluation tests were performed at different temperatures depending on the feedstock utilized. The product reformate stream coming from the reactor was passed through a series of heat exchangers and ice cooled knockout trap to condense water and other liquids, after which, the product gases were analyzed with an online GC/TCD (Agilent 6390 N) equipped with Hayesep Q and Molecular Sieve A columns. The liquids were injected into the reactor system through a motorized syringe pump (Kd science).
The N2-physisorption isotherms of representative supports and catalysts developed in this study are presented in
A H2 chemisorption technique was employed to estimate the metallic surface area and metal dispersion of the active component (nickel); the observed findings are given in Table 2b. All of the catalyst formulations investigated in the current work, were prepared by a standard wet impregnation method and were loaded with the same amount of nickel, i.e., 5 wt %. During a chemisorption experiment, the sample was dried, reduced in hydrogen, evacuated, then cooled to the analysis temperature (35° C.), and finally evacuated before performing actual measurements. In a volumetric H2 chemisorption measurement, known amounts of hydrogen were dosed and subsequently adsorbed at different partial pressures, resulting in a chemisorption isotherm. This isotherm measurement was repeated after applying an evacuation step at the analysis temperature to remove weakly adsorbed species (back-sorption or a dual isotherm method). The difference between the two isotherms represents the chemically bonded reactive gas and is used to calculate the active metal surface area. This information is combined with information on metal loading to calculate the metal dispersion. The relative measurement of chemically bound hydrogen was used to distinguish all the catalyst formulations investigated in the current study. The results obtained thereof are shown in Table 2b.
To ascertain the composition and phase purity, the catalysts were examined by XRD. The X-ray powder diffraction patterns of a few representative catalyst supports developed in the present project are shown in
Representative TPR patterns of various ternary oxide supports and Ni-supported catalyst prepared with surfactant/metal molar ratio 0.5 are shown in
Raman Spectroscopy is capable of investigating the modifications taking place in the oxygen sublattice of the samples. Raman spectra of a few representative catalyst supports are collected in
In order to understand the nature of interactions between the different ions (Ce4+/3+, Zr4+, and Mn+), the various ternary oxide supports and corresponding catalysts (prepared with surfactant/metal molar ratio=0.5) were investigated by XPS technique. The representative photoelectron peaks are shown in
OSC is a measure of oxygen storage and release property, it is depicted in the following equations.
CeO2CeO2-x+½O2
Ce2+Ce3+
Cerium oxide, due to very low Ce3+/Ce4+ redox potential of the couple (E=1.7 eV), can regulate oxygen storage and release properties, depending on the ambient conditions, this remarkable feature is the most desired one for any redox catalytic process [41]. Primarily, ceria was recognized as a promising oxygen storage material, because it keeps a cubic crystal structure even during the alternate storage and release of oxygen and its volume change is small. However, OSC and thermal durability of pure CeO2 were both insufficient for high temperature applications. Addition of other metal ions (isovalent/aliovalent) into CeO2 lattice improves OSC by increasing the number of oxygen defects under reductive conditions [41]. In terms of the reaction rate, the oxygen storage and release reaction is primarily comprised of two reaction steps, namely, surface oxygen diffusion, and bulk oxygen diffusion [29]. In the case of ceria-zirconia solid solutions, surface oxygen and bulk diffusivities were found to correlate with the homogeneity of the Zr- and Ce-atoms distribution in the oxide framework as revealed by 18O/16O isotopic exchange method [42].
The OSC experiments were performed in a thermogravimetric analyzer (TGA), under cyclic reductive and oxidative excursions. The experimental schematic is shown in the
The redox and catalytic properties of ceria-based composite oxides are mainly dependent upon these main factors: particle size, phase modification, structural defects/distortion (lattice), and chemical nonstoichiometry. In general, reducing the particle size of a catalyst results in increasing surface area and changing its morphology, thus providing a larger number of more reactive edge sites. Especially when the particle size is decreased below 100 nm, the materials become nanophasic where the density of defects increases so that up to half (50%) of the atoms are situated in the cores of defects (grain boundaries, interphase boundaries, dislocations, etc.). The high density of defects in nanophase materials provides a large number of active sites for gas-solid catalysis, while the diffusivity through the nanometer sized interfacial boundaries promotes fast kinetics of the catalyst activation and reactions. Thus, there are several advantages for switching from conventional to nanosized materials. The preparation route adapted in this report, yield nanostructured materials, evidence of which came from the HREM imaging technique as described below [41].
To explore the structural features at the atomic level, HREM studies were performed on some selected representative samples. The TEM global view of Ce0.5Zr0.33La0.17O2 and Ce0.5Zr0.33Y0.17O2 supports are respectively shown in
a. Dry (CO2) Reforming of Methane
The screening tests performed on various ternary mixed oxide catalysts [as in formula (II)] and quaternary mixed oxide catalysts [as in formula (II)] developed in the present study, are presented in
The typical CO2 reforming of CH4 reaction is represented below:
CO2+CH4=2CO+2H2
The equations used for calculating conversion and selectivity are:
CH4 conversion %=(CH4)in−(CH4)out/(CH4)in×100
CO2 conversion %=(CO2)in−(CO2)out/(CO2)in×100
H2 selectivity %=(H2)out/2*[(CH4)in−(CH4)out]×100
b. Steam Assisted CO2 Reforming of Methane
A portfolio of ternary mixed oxide catalysts and quaternary mixed oxide catalysts [as in formula (II)] were screened for effectiveness in a steam assisted CO2 reforming of methane reaction and the results obtained thereof are presented in
The equations used for calculating conversion and selectivity are:
CH4 conversion %=(CH4)in−(CH4)out/(CH4)in×100
CO2 conversion %=(CO2)in−(CO2)out/(CO2)in×100
H2 selectivity %=(H2)out/[2*[(CH4)in−(CH4)out]]+[(H2O)in−(H2O)out]×100
c. Partial Oxidation of Hexadecane (CPOxC16)
The partial oxidation of hexadecane can be represented by the following equation:
C16H34+8O2=16CO+17H2
The equations used for calculating conversion and selectivity
Conversion (hexadecane) % ‘X’=Carbonin−Carbonout/Cin×100
Selectivity (H2) %=[(H2)out]/[(H2)theoretically expected×X]×100
Yield (H2) %=[(H2)out]/[(H2)theoretically expected]×100
d. Partial Oxidation of Synthetic Gasoline (CPOxSG)
A mixture of most commonly occurring fuel compounds were mixed together in order to obtain sulfur-free synthetic gasoline, more details are presented in Table 3. The average chemical formula of the synthetic mixture was C8.27H15.1. The reaction conditions employed for the above reaction were T=850° C.; P=1 atm.; O2/C molar ratio=0.5; pre-reduction temperature=700° C. for 2 h in 5% H2/bal.N2; catalyst=0.2 g; diluent α-Al2O3=7.6 g; sieve size=0.78 mm; /Dp=61.5; D/Dp=15.9; where L is the catalyst bed length, D is the diameter of the reactor and Dp is the average diameter of the catalyst particle. Based on the parametric screening results obtained for catalytic partial oxidation of hexadecane (C16H34), only the best catalysts for CPOx-C16H34 were tested in the present example. All the ternary catalysts tested in this example, were obtained from supports which were prepared by employing surfactant/metal molar ratio=0.5 and the quarternary catalyst tested for this example, was obtained from the support which was prepared by employing surfactant/metal molar ratio=1.25. The results obtained thereof are shown in
Partial oxidation of synthetic gasoline is presented in the following equation:
C8.27H15.1+8.27/2O2=8.27CO+7.55H2
The equations used for calculating conversion and selectivity
Conversion (Synthetic Gasoline) % ‘X’=Carbonin−Carbonout/Carbonin×100
Selectivity (H2) %=[(H2)out]/[(H2)theoretically expected×X]×100
Yield (H2) %=[(H2)out]/[(H2)theoretically expected]×100
f. Partial Oxidation of Synthetic Diesel (CPOxSD)
According to literature, petroleum-derived diesel is composed of about 75% saturated hydrocarbons (primarily paraffins including n-, iso- and cycloparaffins), and 25% aromatic hydrocarbons (including naphthalenes and alkylbenzenes). The average chemical formula for common diesel fuel is C12H23, ranging approximately from C10H2O to C15H28 [43]. Following the above information, various generic chemical compounds that are predominantly found in the commercial diesel were mixed together to prepare a known mixture of synthetic diesel. The compounds chosen represent different classes of compounds normally found in commercial diesel. Most of these compounds are members of the paraffinic, naphthenic, or aromatic class of hydrocarbons; each class has different chemical and physical properties. Further details of their physical properties and relative composition can be found in Table 4. The average density and average molecular weight of the mixture was found to be 0.8 g/ml and 190.16 g/mol respectively; the average chemical formula of the synthetic mixture was C13.55H27.2. Owing to the complex nature of the fuel, diesel reforming poses several unique technical challenges. The reaction conditions employed for the above reaction were T=900° C.; P=1 atm.; O2/C molar ratio=0.725; pre-reduction temperature=700° C. for 2 h in 5% H2/bal.N2; L/Dp=61.5; D/Dp=15.9 where L is the catalyst bed length, D is the diameter of the reactor and Dp is the average diameter of the catalyst particle. Based on the parametric screening results obtained for catalytic partial oxidation of hexadecane (C16H34), only the best catalysts for CPOx-C16H34 were tested in the current example. All the ternary catalysts tested for the current example, were obtained from supports which were prepared by employing surfactant/metal molar ratio=0.5 and the quaternary catalyst tested for the current application, was obtained from the support which was prepared by employing surfactant/metal molar ratio=1.25. The results obtained thereof over the “5Ni/Ce0.5Zr0.33M10.17M20.0O2 (M1=Ca, La, Y)” and 5Ni/Ce0.5Zr0.33M10.085M20.085O2 (M1=Ca; M2=Y) catalysts at W/FSD=10.57 g cat. h/mol. SD are shown in
Partial oxidation of synthetic diesel is presented in the following equation:
C13.55H27.2+13.55/2O2=13.55CO+13.6H2
The equations used for calculating conversion and selectivity are:
Conversion (Synthetic Diesel) % ‘X’=Carbonin−Carbonout/Carbonin×100
Selectivity (H2) %=[(H2)out]/[(H2)theoretically expected×X]×100
Yield (H2)%=[(H2)out]/[(H2)theoretically expected]×100
f. Steam Reforming of a Liquid Mixture of Oxygenated Hydrocarbons (Oxy-HCR)
As an example, the compounds chosen to prepare the oxygenated hydrocarbon mixture were butanol, propanol, ethanol, lactic acid, ethylene glycol and glycerol. An equimolar mixture of all the above six oxygenated hydrocarbons was prepared by mixing the individual compounds with water. The amount of water added was based on stoichiometry of the following equations (below).
C4H9OH+7H2O→4CO2+12H2
C3H7OH+5H2O→3CO2+9H2
C2H5OH+3H2O→2CO2+6H2
C3H6O3+3H2O→3CO2+6H2
C2H6O2+2H2O→2CO2+5H2
C3H8O3+3H2O→3CO2+7H2
The weighted average of the synthetic mixture can be represented as follows:
C2.8H7.3O1.9+3.7H2O→2.8CO2+7.35H2
The average molecular weight and density of the mixture was calculated as 71.2 and 1.0 respectively. The reaction conditions employed were: Reduction temperature=700° C. for 2 h in presence of 5% H2/bal.N2; Reaction temperature=700° C., 600° C., and 500° C.; steam/feed=2; Feed flow rate: 0.1 mL/min; W/FOxy-HC=8.58 g cat. h/mol. Oxy-HC; Catalyst amount: 0.25 g (0.78 mm particle size) mixed with 7.6 g of diluents (α-alumina of 0.78 mm particle size); L/Dp=61.5 (>50) and D/Dp=15.9 (>10); where L is the catalyst bed length, D is the diameter of the reactor and Dp is the average diameter of the catalyst particle. The following five catalysts: 5Ni/Ce0.5Zr0.33M10.17M20.0O2 (M1=Ca, Gd, La, Mg, & Y) (obtained from supports prepared with surfactant/metal molar ratio=1.25) were tested for their reforming efficiency and stability at 700° C., 600° C., and 500° C. using the above prepared oxygenated hydrocarbon mixture. The results obtained thereof are shown in
where, organicin is total moles of oxygenated hydrocarbon fed in and organicout is total moles of organic out and H2out is total moles of H2 out. Organicout and H2out were calculated based on the Tout, which, is total flow rate out.
In order to establish the uniqueness of the catalysts developed for feed-stock and process flexibility, relationships between their resultant catalytic activity and their inherent textural, physico-chemical, and surface characteristics were formulated and the resultant relationships were termed as structure-activity relationships (SARs). The SARs aid in understanding the catalytic phenomena involved in any given reforming process from the perspective of catalyst structure. Furthermore the SARs are useful determining the characteristics of the catalysts that contribute towards their unique performance. SARs also help better understand the surface reactivity, shape selectivity, and hydrodynamic properties and ultimately to establish the uniqueness of the given catalyst system [4].
The structure-activity relationship generated in the present study is summarized below. High OSC, high pore volume/surface area, and ease of reducibility combined with high surface nickel content, better nickel dispersion lead to improved catalyst performance. The incorporation of the third oxide and fourth oxide in the support formulation imparts to the ternary and quaternary systems unique characteristics that make them perform better as feedstock flexible and process flexible catalysts compared to binary oxide support systems. Furthermore, the correlation plots (
While the present application has been described with reference to what are presently considered to be the preferred examples, it is to be understood that the application is not limited to the disclosed examples. To the contrary, the application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
All publications, patents and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety. Where a term in the present application is found to be defined differently in a document incorporated herein by reference, the definition provided herein is to serve as the definition for the term.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA11/00224 | 3/4/2011 | WO | 00 | 11/9/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61311055 | Mar 2010 | US |
