Patent Application
20180133695
The present application claims priority of Indian patent application no. 1840/MUM/2015, “ADDITIVE COMPOSITION FOR MIXED METAL OXIDE CATALYSTS AND ITS USE IN HYDROCARBON CONVERSION PROCESSES”, filed on 8 May 2015, the whole content of which is hereby incorporated for reference.
The present invention relates to an additive composition which when added to mixed metal oxide catalysts increases the performance of the mixed metal oxide catalyst and requires lower usage of group VIII metals viz. Platinum group metals which are commonly used for increasing the life of the catalyst. The present invention also relates to a process for preparing the afore-mentioned additive composition. The present invention further relates to hydrocarbon conversion processes carried out using the mixed metal oxide catalysts which comprises the additive composition.
Chlorine doped alumina catalysts and Zeolites have been popular catalysts for several hydrocarbon reactions used in petroleum processes, specifically isomerization reactions. While Cl−/Al2O3 catalysts exhibit excellent activity and selectivity towards hydrocarbon reactions, they are highly sensitive to feed contaminants such as water (H2O), organic sulfur and organic nitrogen and hence require highly capital intensive feed pretreatment procedures for their usage. They further produce harmful hydrochloric acid downstream which needs to be treated adding to the process costs. Zeolites on the other hand do not require pre- or post-treatment but are significantly lower in terms of their activity. A tradeoff thus exists between the two catalysts and refiners are often left to choose between both the popular options either trading off in terms of performance or costs.
An optimal hydrocarbon conversion catalyst specifically for isomerization reactions possesses the following traits. It is important to satisfy all three criteria described below for superior performance.
Hino et al. (1980) in their seminal paper—“Synthesis of Solid superacid catalyst with acid strength of H0<−16.04”, J.C.S. Chem. Comm., 851-852, 573, 1980 explained the usage of anion modified Group III and Group IV oxides such as WO3/ZrO2 and SO42−/ZrO2 catalysts as strong acids which exhibit promising performance in hydrocarbon conversion processes such as isomerization. While these catalysts show moderate performance tradeoff in comparison to the Cl−/Al2O3 catalysts, they do not need the feed pretreatment and thus the tradeoff between costs and performance is to a lower extent for the refiner in comparison to the Zeolite catalysts. While several patents and papers have been published improving the design of the originally proposed catalyst by Hino et al. prolonged catalyst stability was not achieved which is essential for commercial petroleum applications. This prior art describes the usage of sulfated zirconia catalysts which at most satisfy two of the above attributes thus leading to non-optimal performance in hydrocarbon conversion processes such as isomerization.
More recently substantial research has been conducted to improve the stability and longevity of these anion modified acid catalysts and several patents have been filed exhibiting their advanced stability for petroleum processes such as isomerization, alkylation and transalkylation—U.S. Pat. Nos. 6,107,235 and 6,080,904 etc.
Further, the use of several dopant systems is reported to increase the stability of these catalyst compositions, for example, Russian patent document 2191627 discloses a method for the synthesis of sulfated zirconia catalyst loaded with noble metals such as platinum, palladium, ruthenium, osmium, iridium and the like on an zirconia support containing up to 20% of active components of silicon, titanium oxide, magnesium and alumina. The catalyst is further loaded with Nickel, Titanium, Germanium, Manganese, Cobalt, Bismuth, Iron, Vanadium, Cobalt, Zirconium and mixtures thereof. The catalyst as disclosed in the aforementioned patent is used for the isomerization reaction; however, the catalyst demonstrates very poor stability. The concentration of 2, 2-Dimethyl butane (2, 2-DMB) a key performance metric in the product stream decreases after 200 hours operation from 28% to 14%. This catalyst formulation also requires higher quantities of Platinum group (Group VIII) metals to maintain performance over extended periods of operation.
U.S. Pat. No. 3,032,599 disclosed one of the first usages of sulfated zirconia to isomerization and alkylation of hydrocarbons. The catalysts showed high initial activity but not prolonged performance due to low surface area. Furthermore, these powdery catalysts are for the most part unusable in industrial reactors due to pressure drop implications.
U.S. Pat. No. 3,132,110 discloses the use of sulfated zirconia catalyst, pure or preferably combined with alumina. The catalysts obtained herein are indeed excellent in terms of initial activity but do not show prolonged performance. Further, they need very high operating temperatures of over 370° C. which results in poor product yields. Also, these catalysts undergo accelerated deactivation due to coke deposition on the surface during operation.
U.S. Pat. No. 6,448,198 discloses the synthesis of high surface area and mesopore zirconia structures which when sulfated gives superior performance with isomerization reactions. However, these catalysts suffer with significant inhibition from feed contaminants such as organic sulfur and nitrogen. Their performance in terms of peak yield of the desired product 2, 2-DMB degrades from 27% to 12% in the presence of 5 ppm of either sulfur or nitrogen in the feed stream.
European patent application No. 1002579 discloses a layered catalyst having zirconium core component followed by Mn, Fe or Ni shell and a top layer consisting of noble metals. The catalyst was used for the isomerization reaction. However, the catalyst shows degradation in overall performance after 200 hours of operation. The concentration of 2, 2-DMB, a key performance product decreases from 28% to 20%.
Another Russian patent document 2171713 discloses a process for the preparation of a catalyst with 0.2 to 1% platinum or Palladium, 0.05 to 2.5% chlorine and 0.5 to 10% sulfate which are deposited on a mixture of aluminum and zirconium oxide. The major disadvantage of this catalyst is low stability for isomerization reaction and higher use of reactant hydrogen. A hydrogen to oil ratio of 5 to 10 is required to maintain stability of such a catalyst over extended operating periods.
U.S. Pat. No. 7,015,175 discloses a method for the synthesis of sulfated zirconium catalyst doped with high concentration (of at least 3%) of Lanthanide series elements. The performance of such a catalyst degrades substantially in the presence of organic sulfur or nitrogen based contaminants which are typically seen in the petroleum feed stream. The yield of 2, 2-DMB reduces from 28% to 14% with 5 ppm of sulfur in the feed stream. Also, the operating temperature as described in the patent is substantially high (˜170° C.) for optimal operation. Isomerization is an equilibrium reaction and high conversion is facilitated at low temperatures (˜130° C.).
Thus in order to overcome the limitations of the prior arts described above, the present invention provides a highly efficient additive composition which can be directly added to the mixed metal oxide catalysts. The additive composition increases the performance of the catalyst, favors low temperature operations, increases tolerance to feed contaminants and decelerates the catalyst growth for high product selectivity.
In one aspect the present invention provides an additive composition having the general formula:
AxByC(1-y)DzOm
In another aspect the present invention provides a process for preparing the afore-mentioned additive composition comprising:
Another aspect of the present invention is to provide mixed metal oxide catalysts comprising the afore-mentioned additive composition.
Yet another aspect of the present is to provide processes for converting hydrocarbons by contacting a feed with the afore-mentioned mixed metal oxide catalyst which comprises the additive composition.
Further scope and applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only, because various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The following detailed description of the invention will be better understood when read in conjunction with the appended drawings. For the purpose of assisting in the explanation of the invention, there are shown in the drawings embodiments which are presently preferred and considered illustrative. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown therein.
For the purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification are to be understood as being modified in all instances by the term “about”. It is noted that, unless otherwise stated, all percentages given in this specification and appended claims refer to percentages by weight of the total composition.
Thus, before describing the present invention in detail, it is to be understood that this invention is not limited to particularly exemplified systems or process parameters that may of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments of the invention only, and is not intended to limit the scope of the invention in any manner.
The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only, and in no way limits the scope and meaning of the invention or of any exemplified term. Likewise, the invention is not limited to various embodiments given in this specification.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the case of conflict, the present document, including definitions will control.
It must be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the content clearly dictates otherwise.
The terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.
As used herein, the terms “comprising” “including,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to.
In one aspect, the present invention provides an additive composition comprising mixed metal oxide having the general formula:
AxByC(1-y)DzOm
Element A is selected from the group consisting of Strontium, Magnesium, Barium or mixtures thereof. Elements B and C are selected from the group consisting of Cerium, Samarium, Ytterbium, Lanthanum, Neodymium, Yttrium or mixtures thereof. Preferably element A is Strontium, B is Cerium or Yttrium, C is Samarium or Ytterbium and D is Manganese or Ruthenium.
In an embodiment of the present invention, the mole percent of element A is in the range of 0.1<A<0.25; mole percent of elements B, C are in the range of 0.05<B, C<0.2; mole percent of element D is in the range of 0.1<D<0.35; and the valence charge of oxygen is such that the overall charge of the molecule is neutral.
In the most preferred embodiment, the additive composition has the general formula:
SrxByC(1-y)DzOm
wherein:
In another aspect, the present invention provides a process for preparing the afore-mentioned additive composition comprising:
In an embodiment of the present invention, the additive composition may be prepared by co-precipitation method or sequential precipitation method wherein suitable amounts of metal salt precursors such as but not limited to nitrate salts or acetate salts or chloride salts or sulfate salts are dissolved in water. The resultant mixture of metal cations is then precipitated using a precipitating agent. The precipitating agent may also act as a surfactant to create the desired crystal structure. Suitable precipitating agent may be selected from the group consisting of sodium hydroxide, sodium carbonate, oxalic acid, sodium oxalate, ammonium oxalate or mixtures thereof and may be added in an amount so as to obtain a final pH value of at least 9 or above.
The pH of solution of step (b) is adjusted between 9-12 using tetramethylammonium hydroxide (TMAOH). Additional TMAOH may be added to reestablish the pH of the solution. The resultant metal precipitant is filtered and washed using deionized water for three to four times. Finally, the metal precipitant is dried, processed and calcined at 500° C. for 4 hours.
The afore-mentioned process may optionally comprise adding an oxidizing agent or a surfactant to the mixture of step (a). Said oxidizing agent may be selected from the group consisting of hydrogen peroxide, chlorate, perchlorate, hypochlorite, nitric acid, sulfuric acid, potassium permanganate or mixtures thereof and may be added in an amount of 100% in excess of the moles of element D used in the additive composition. Said surfactant may be selected from the group consisting of polyvinyl alcohol (PVA), Triton X-100, Pluronic F127, Polyethylene glycol (PEG), sodium salt of polyacrylic acid (Na-PAA) or mixtures thereof and may be added in an amount of 50% in excess of the moles of element A used in the additive composition.
The additive composition may be partially calcined to start the formation of the desired crystals which when mixed with the mixed metal oxide catalyst such as the sulfated alumina zirconia catalyst will allow optimal crystal formation during final calcination procedure. In another embodiment of the present invention, the additive may not be fully calcined wherein X-ray diffraction does not reveal fully crystalline structures but only reveals partially crystalline and partially amorphous phases.
In another embodiment of the present invention, the additive composition may be prepared using the citric acid method. Said method includes dissolving suitable amounts of the different metal salts in water with 10% excess of molar amounts of citric acid. Optionally, all or a portion of the citric acid may be substituted with Ethylene diamine tetraacetic acid (EDTA) or a mixture of Polyvinyl alcohol (PVA) and sucrose. The mixture is stirred and heated until a viscous gel forms. The viscous gel is dried, processed, and calcined at 500° C. for 4 hours.
In another aspect, the present invention provides a mixed metal oxide catalyst comprising the afore-mentioned additive composition. Said mixed metal oxide catalyst is selected from the group consisting of Group III and Group IV of the periodic table.
In an embodiment of the present invention, the mixed metal oxide catalyst is selected from the group consisting of a sulfated or a tungsated metal oxide of Zirconium or Aluminum or mixtures thereof. Said mixed metal oxide catalyst may optionally consist of a hydrogenating metal selected from the group consisting of Manganese, Iron, Gallium, Copper, Cobalt or mixtures thereof.
The afore-mentioned mixed metal oxide catalyst may further comprise a Group VIII metal selected from the group consisting of Platinum, Palladium, Rhenium, Rhodium, Iridium, Ruthenium, Gold or mixtures thereof. In an embodiment of the present invention, about 0.1% to 5% of Group VIII metal may be present in the mixed metal oxide catalyst. Said Group VIII metal in small amounts may be added to the final mixed metal oxide catalyst by usual impregnation techniques known to those skilled in the art. One of the specific advantages of the additive composition of the present invention is to provide the optimal charge density on the surface catalyst to enable further ion doping. For example, most hydrocarbon processes require small quantities of Platinum group metals (PGM) to be further added to the final catalyst recipe to enhance long term performance. PGM is typically added to the catalyst by dry impregnation method which while cheaper does not give optimal control on the location of PGM on the surface of the catalyst leading to non-optimal performance. The additive composition described in the present invention when added to the catalyst will provide the interionic repulsive forces thus increasing the dispersion (or surface area) of the PGM metals on the surface, thus dramatically improving the PGM surface area. Larger PGM surface area results directly in increasing catalyst longevity and reactivity. Further, the additive also increases the metal support interactive forces thus decreasing the stronger binding forces of the PGM metals towards undesirable feed contaminants such as sulfur and nitrogen.
In an exemplary embodiment of the present invention, the additive composition may be directly added to sulfated zirconia catalysts as described in the open literatures titled 1) “Effect of isopropanol aging of Zr(OH)4 on n-hexane isomerization over Pt—SO42−/Al2O3—ZrO2, Catalysis Today, October 2009, 148 (1-2), p 70-74, 2) “Catalytic performance of Re/Ga2O3/WO3/ZrO2 catalyst for n-Hexane isomerization”, Chi. J. of. Catal. September 2009, 30(9), p 859-863).
The additive composition can be directly added to mixed metal oxide catalysts in varying ratios to the sulfated zirconia catalyst such as Pt—SO42−/Al2O3/ZrO2 catalysts to obtain the desired results.
In an embodiment of the present invention, the additive composition is added to the mixed metal oxide catalyst prior to calcination and about 0.5 to 25 weight percent of the additive composition is added to the mixed metal oxide catalyst. In order for the final catalyst to be active, the sulfated mixture of Al2O3 and ZrO2 in their hydroxide form should be intimately mixed with the additive composition in ratios of 2 to 25% so as to obtain maximum benefit.
The additive composition of the present invention may be synthesized separately from the mixed metal oxide catalyst (such as sulfated alumina zirconia catalyst). The synthesis of the sulfated alumina zirconia catalyst along with some transition metal additive may be done through the processes as described in the open literature titled 1) “Effect of isopropanol aging of Zr(OH)4 on n-hexane isomerization over Pt—SO42−/Al2O3—ZrO2, Catalysis Today, October 2009, 148 (1-2), p 70-74, and 2) “Catalytic performance of Re/Ga2O3/WO3/ZrO2 catalyst for n-Hexane isomerization”, Chi. J. of Catal., September 2009, 30(9), p 859-863. High surface area Zr(OH)4 and pseudo boehmite may be mulled together and extruded using sulfate ion additive such as sulfuric acid or ammonium sulfate followed by drying at 120° C. for several hours. In addition a transition metal ion may be added to increase the hydrogenation ability of the catalyst.
In an embodiment of the present invention, the additive composition synthesized will have at least two phases namely a spinel phase and a mullite phase or a fluorite phase oxide when characterized with Transmission Electron Microscopy (TEM) or Scanning Transmission Electron Microscopy (STEM)/Energy-dispersive X-ray Analyser (EDX) techniques. In another embodiment, the spinel phase and/or the fluorite phase and/or the mullite phase can include one or more metals.
In a further embodiment of the present invention, the mixed phase catalyst additive composition may include a composite having two or more constituent materials with different physical or chemical properties which remain separate and distinct at the macroscopic or microscopic scale within the finished structure. For example, two particles with different compositions remain separate in TEM (“Transmission Electron Microscopy”) while they do have common interface.
In a further aspect, the present invention provides a process for converting hydrocarbons by contacting a feed with the mixed metal oxide catalyst having the additive composition.
Said hydrocarbon conversion process may be selected from the group consisting of cracking, hydrocracking, aromatic alkylation, isoparaffin alkylation, isomerization, polymerization, reforming, hydrogenation, dehydrogenation, transalkylation or dealkylation, preferably, isomerization, alkylation or transalkylation.
The additive composition described in the present invention enhances the performance of mixed metal oxide catalysts towards hydrocarbon processing reactions such as but not limited to isomerization. The additive composition of the present invention specifically
The following examples are provided to better illustrate the claimed invention and are not to be interpreted in any way as limiting the scope of the invention. All specific materials, and methods described below, fall within the scope of the invention. These specific compositions, materials, and methods are not intended to limit the invention, but merely to illustrate specific embodiments falling within the scope of the invention. One skilled in the art may develop equivalent materials, and methods without the exercise of inventive capacity and without departing from the scope of the invention. It is the intention of the inventors that such variations are included within the scope of the invention.
Catalyst A was prepared using the well-established sulfated alumina zirconia synthesis route as known to those skilled in the art as shown in U.S. Pat. No. 6,448,198 B1. The corresponding references for the catalyst design have been provided for reference. Briefly, high surface area Zirconium hydroxide (Zr(OH)4) and pseudo-boehmite were co-mulled together to form an intimate mixture. They were then extruded into 1 mm diameter and 2 mm length extrudes. The extrudes were then exposed to 1M sulfuric acid (15 ml/gm of extrudes) and subsequently vacuum filtered to remove the excess sulfate ions. The extrudes were then calcined at 600° C. for 3 hours to form crystalline sulfated alumina zirconia catalyst. The catalyst had 0.24 ml/g pore volume at the end of the calcination. Platinum with 0.3 wt % was then incorporated into the catalyst by wet impregnation technique as known to those skilled in the art. This catalyst was designated catalyst A.
7 gm of catalyst A was loaded in a fixed bed reactor where it was calcined in air at 500° C. for 2 hours and subsequently reduced in Hydrogen for 1 hour. A reaction mixture containing the following composition was then flown on the catalyst at 30 bar and 135° C. for 200 hours. The result of the product sample drawn at 50 and 200 hours respectively is shown in Table 1.
Catalyst B was prepared using the popular metal doped sulfated zirconia catalyst synthesis route as known to those skilled in the art and also described in the patent, EP0532153B1. Briefly, high surface area zirconium hydroxide was prepared by rapidly mixing zirconium carbonate and ammonia solutions. After washing and sieving to desired size, Iron (Fe) and Manganese (Mn) nitrate solutions were added to the support material via incipient wetness impregnation method. The catalyst was subsequently dried and calcined at 725° C. for one hour. 0.3% Platinum was incorporated into the catalyst via incipient wetness impregnation method.
The testing procedure described in example 1 was used to evaluate catalyst B's performance. The results of which are detailed in Table 2.
Base catalyst was synthesized using the method described in the open literature (reference provided in the previous sections). Briefly, high surface zirconium hydroxide and pseudo boehmite were co-mulled together and impregnated with 1N H2SO4 by using 15 ml/gm of the support material. Excess acid was drained and the sulfated support was dried at 120° C. for several hours. Gallium was then introduced into the support by adding its corresponding nitrate salt to achieve 3% loading by incipient wetness technique. The mixture was then dried and is labeled Catalyst Z.
Additive for catalyst Z1 was first prepared by mixing nitrate salts of Strontium, Cerium, Samarium and Manganese. 25.5 gms of Mn(NO3)2 50% solution, 5 gms of Sr(NO3)2, 9.3 gms of Ce(NO3)3.6H2O 1.1 gms of Sm(NO3)3.6H2O were mixed together in desired amount of water. 13.4 gms of 35% H2O2 was added to the mixture while stirring. 2.4 gms of Oxalic acid was then added to the mixture. Finally 1 gm of Pluronic (F127) and 1 gm of PEG were added to final mixture and stirred for 1 hour. The pH of the final solution was brought to 10.5 using TMAOH. The product was filtered, washed and calcined at 500° C. The XRD profile of the product is shown in
The additive thus produced is added to catalyst Z shown in example 1 and extruded into 1 mm diameter and 2 mm length extrudes. The final catalyst formulation was calcined at 700° C. for 3 hours. 0.3 wt % Platinum was added to the calcined extrudes by incipient wetness impregnation method. The catalyst is labeled Z1 and the isomerization test results with the feed shown in comparative example 1 are shown in Table 2.
Additive for catalyst Z2 was first prepared by mixing nitrate salts of Strontium, Cerium, Ytterbium and Manganese. 25.5 gms of Mn(NO3)2 50% solution, 5 gms of Sr(NO3)2, 9.3 gms of Ce(NO3)3.6H2O 1.1 gms of Yb(NO3)3.6H2O were mixed together in desired amount of water. 13.4 gms of 35% H2O2 was added to the mixture while stirring. 2.4 gms of Oxalic acid was then added to the mixture. Finally 1 gm of Pluronic (F127) and 1 gm of PEG were added to final mixture and stirred for 1 hour. The pH of the final solution was brought to 10.5 using TMAOH. The product was filtered, washed and calcined at 500° C. The XRD profile of the product is shown in
The additive thus produced is added to catalyst Z shown in example 1 and extruded into 1 mm diameter and 2 mm length extrudes. The final catalyst formulation was calcined at 700° C. for 3 hours. 0.3 wt % Platinum was added to the calcined extrudes by incipient wetness impregnation method. The catalyst is labeled Z2 and the isomerization test results with the feed shown in comparative example 1 is shown in Table 2.
Additive for catalyst Z3 was first prepared by mixing nitrate salts of Strontium, Cerium, Ytterbium and Ruthenium. 17 gms of Ru(NO3)2, 5 gms of Sr(NO3)2, 9.3 gms of Ce(NO3)3.6H2O 1.1 gms of Yb(NO3)3.6H2O were mixed together in desired amount of water. 13.4 gms of 35% H2O2 was added to the mixture while stirring. 2.4 gms of Oxalic acid was then added to the mixture. Finally 1 gm of Pluronic (F127) and 1 gm of PEG were added to final mixture and stirred for 1 hour. The pH of the final solution was brought to 10.5 using TMAOH. The product was filtered, washed and calcined at 500° C. The XRD profile of the product is shown in
The additive thus produced is added to catalyst Z shown in example 1 and extruded into 1 mm diameter and 2 mm length extrudes. The final catalyst formulation was calcined at 700° C. for 3 hours. 0.3 wt % Platinum was added to the calcined extrudes by incipient wetness impregnation method. The catalyst is labeled Z2 and the isomerization test result with the feed shown in comparative example 1 is shown in Table 2.
The catalysts prepared with the invention described herein, namely catalysts Z1, Z2 and Z3 exhibit excellent performance characteristics in terms of product conversion, low temperature operation and high tolerance to feed contaminants.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1840/MUM/2015 | May 2015 | IN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IN2016/000061 | 3/4/2016 | WO | 00 |
