p-Xylene is a major product dominating current chemical production in terms of volume and energy consumption. Due to the rapid growth in the global market of polyethylene terephthalate (PET, 6-8% per year), its replacement with a renewable feedstock is a highly sought goal, and there exist numerous ongoing research and development efforts to produce p-xylene from renewable biomass feedstocks. However, current synthetic methods lead to alkylated and oligomerized products, and low yields of p-xylene.
In a first general aspect, a catalyst includes a porous material, and phosphorus coupled to the porous material. The porous material can be a microporous material, a mesoporous material, or a micro-mesoporous material.
Implementations of the first general aspect include one or more of the following features.
In some implementations, the porous material is a molecular sieve framework that includes silicon and defines micropores bounded at least in part by 8-membered tetrahedral atom rings, 10-membered tetrahedral atom rings, 12-membered tetrahedral atom rings, or a combination thereof. The molecular sieve framework may include aluminum, and a ratio of silicon atoms to aluminum atoms in the molecular sieve framework may be at least 100:1, at least 300:1, at least 500:1, or at least 1000:1. A ratio of silicon atoms to phosphorus atoms may be in a range of 3:1 to 150:1. The molecular sieve framework may include zeolite beta (BEA), MFI, or self-pillared pentasil (SPP). In some cases, the porous material includes at least one zeolite selected from the group consisting of AFI, *BEA, CFI, CHA, CON, DDR, FAU, FER, GME, IFR, ISV, ITE, ITH, ITW, LTA, LTL, MAZ, MEI, MOR, MTF, MTW, MWW, OFF, RWR, SOD, STF, STO, STT, and TON. The porous material may include mesoporous silica, such as SBA-15. In certain cases, the porous material includes mesoporous graphitic carbon or a carbon molecular sieve.
In a second general aspect, dehydrating a reactant including a cyclic ether or an alcohol includes contacting the reactant with a catalyst, where the catalyst includes a phosphorus-containing porous material.
Implementations of the second general aspect may include one or more of the following features.
The reactant may be derived from biomass. In some implementations, the reactant is a cyclic ether, such as a furan. In one example, the cyclic ether is 2,5-dimethylfuran, and contacting the reactant with the catalyst includes contacting the 2, 5-dimethylfuran with ethylene in a nonaqueous solvent in the presence of the catalyst to yield a cycloadduct, and dehydrating the cycloadduct in the presence of the catalyst to yield a product including p-xylene. The yield of p-xylene may be at least 90%, at least 93%, at least 95%, at least 97%, or at least 99%. In some cases, the ethylene is formed by contacting ethanol with the catalyst to yield ethylene before contacting the 2, 5-dimethylfuran with the ethylene. In some implementations, the reactant is an alcohol. When the reactant is ethanol, contacting the ethanol with the catalyst yields a product including ethylene. When the reactant is isopropanol, contacting the isopropanol with the catalyst yields a product including propene. The catalyst may be a catalyst according to the first general aspect.
In a third general aspect, synthesizing a catalyst including phosphorus includes contacting a porous material with a phosphorus-containing compound to yield a wet porous material including phosphorus, removing water from the wet porous material including phosphorus to yield a dry porous material including phosphorus, and calcining the dry porous material including phosphorus to yield a catalyst including phosphorus coupled to the mesoporous material. The porous material may be a microporous material, a mesoporous material, or a micro-mesoporous material.
Implementations of the third general aspect may include one or more of the following features.
The porous material may be solvo-thermally synthesized in the presence of the phosphorus-containing compound to yield the wet porous material including phosphorus. The porous material may include a molecular sieve framework defining micropores bounded at least in part by 8-membered tetrahedral atom rings, 10-membered tetrahedral atom rings, 12-membered tetrahedral atom rings, or a combination thereof. Aluminum may be removed from the porous material before contacting the porous material with the phosphorus-containing compound.
In some implementations, the phosphorus-containing compound includes phosphoric acid. In certain implementations, the phosphorus-containing compound includes at least one of tetra(n-butyl) phosphonium hydroxide, tetramethyl phosphonium hydroxide, tetraethyl phosphonium hydroxide, and tetrapropyl phosphonium hydroxide. The porous material may include mesoporous silica, mesoporous graphitic carbon, or a carbon molecular sieve.
In a fourth general aspect, synthesizing p-xylene includes contacting, in the presence of a catalyst including a phosphorus-containing microporous, mesoporous, or micro-mesoporous material, biomass-derived 2,5-dimethylfuran with ethylene in a nonaqueous solvent to yield p-xylene.
In some implementations of the fourth general aspect, the contacting yields a cycloadduct, and dehydration of the cycloadduct may be catalyzed with the catalyst to yield the p-xylene.
In a fifth general aspect, synthesizing a catalyst including phosphorus includes solvo-thermally synthesizing a porous material in the presence of a phosphorus-containing compound to yield a wet porous material including phosphorus, removing water from the wet porous material including phosphorus to yield a dry porous material comprising phosphorus, and calcining the dry porous material including phosphorus to yield a catalyst including phosphorus coupled to the porous material. The porous material may be a microporous material, a mesoporous material, or a micro-mesoporous material.
Implementations of the fifth general aspect may include one or more of the following features.
In some implementations, the porous material includes a molecular sieve framework defining micropores bounded at least in part by 8-membered tetrahedral atom rings, 10-membered tetrahedral atom rings, 12-membered tetrahedral atom rings, or a combination thereof. The phosphorus-containing compound may include at least one of tetra(n-butyl) phosphonium hydroxide, tetramethyl phosphonium hydroxide, tetraethyl phosphonium hydroxide, and tetrapropyl phosphonium hydroxide.
Catalysts and processes described herein provide increased efficiency for the production of p-xylene from renewable biomass feedstocks, thereby increasing the economic feasibility of the production of p-xylene from biomass, such as cellulose.
Methods described herein include contacting a reactant with porous, phosphorus-containing catalyst to dehydrate the reactant. The reactant may be a cyclic ether (e.g., DMF) or an alcohol (e.g., ethanol or ispropanol). Contacting may occur in the presence of a nonaqueous solvent. Suitable reaction conditions include a temperature in a range between 200° C. and 400° C., or between 250° C. and 300° C.
Phosphorus-containing solid catalysts and methods for catalyzing tandem Diels-Alder cycloaddition and dehydration of biomass-derived DMF and ethylene to renewable p-xylene using phosphorus-containing solid catalysts are disclosed herein, along with methods of dehydrating alcohols with the phosphorus-containing solid catalysts to yield alkenes.
As disclosed herein, DMF and ethylene are contacted in a nonaqueous solvent in the presence of a phosphorus-containing solid catalyst that is essentially devoid of strong Brønsted acid character under conditions sufficient to produce p-xylene without catalyzing other by-product reactions, such as alkylation and oligomerization reactions. Examples of solid acid catalysts that are essentially devoid of Brønsted acid character include dealuminated Brønsted acidic aluminosilicate zeolites. Dealuminated Brønsted acidic aluminosilicate zeolites can have a Si/Al atomic ratio greater than 100, greater than 1,000, or greater than 10,000. Other examples of solid acid catalysts that are essentially devoid of Brønsted acid character include zeolites synthesized directly without addition of aluminum in the synthesis mixtures or under conditions that do not lead to aluminum incorporation. In some embodiments, an alcohol (e.g., ethanol) or is contacted with phosphorus-containing solid catalysts to yield an alkene (e.g., ethylene) without catalyzing other by-product reactions.
Suitable nonaqueous solvents include non-polar solvents (e.g., heptane), polar solvents (e.g., dioxane), polar aprotic solvents (e.g., tetrahydrofuran) and polar protic solvents (e.g., isopropanol).
Suitable phosphorus-containing catalysts include a porous inorganic material having phosphorus coupled to the porous material. As used herein, “porous material” generally includes microporous material, mesoporous material, and micro-mesoporous material, where “microprous material” refers to a material having pores with a diameter less than about 2 nm (micropores), “mesoporous material” refers to a material having pores with a diameter in a range of about 2 nm to about 50 nm (mesopores), and “micro-mesoporous material” (or “hierarchical material”) refers to a material having micropores and mesopores. Examples of suitable microporous materials include BEA, MFI, and microporous zeolites. Examples of suitable mesoporous materials include silica gel and BP2000. Examples of suitable micro-mesoporous materials include mesoporous zeolites and hierarchical zeolites, such as self-pillared pentasil (SPP). In some cases, the porous material is a nanomaterial, with at least one dimension in a range of 1 nm to 1000 nm, or 1 nm to 100 nm. The phosphorus coupled to the porous material may be covalently bonded to the mesoporous material, impregnated in the mesoporous material, or both.
In some embodiments, the mesoporous material is a molecular sieve framework including silicon and defining micropores bounded at least in part by 8-membered tetrahedral atom rings, 10-membered tetrahedral atom rings, 12-membered tetrahedral atom rings, or a combination thereof. The molecular sieve framework may include aluminum, and a ratio of silicon atoms to aluminum atoms in the molecular sieve framework is typically at least 100:1, at least 300:1, at least 500:1, or at least 1000:1. In some cases, a ratio of silicon atoms to phosphorus atoms in the molecular sieve framework is in a range of 1:1 to 1000:1 or 3:1 to 150:1. In some examples, the molecular sieve framework includes zeolite beta (BEA), MFI, or self-pillared pentasil (SPP). In some examples, the molecular sieve framework includes at least one zeolite selected from the group consisting of AFI, *BEA, CFI, CHA, CON, DDR, FAU, FER, GME, IFR, ISV, ITE, ITH, ITW, LTA, LTL, MAZ, MEI, MOR, MTF, MTW, MWW, OFF, RWR, SOD, STF, STO, STT, and TON.
In some embodiments, the porous material includes porous silica. The porous silica may be microporous silica, mesoporous silica, or micro-mesoporous silica. Suitable examples include surfactant templated mesoporous silica (e.g., SBA-15), silica nanoparticles, hierarchical (micro-mesoporous) single unit cell zeolites (e.g., SPP), and nanozeolites (e.g., zeolites having a particle size less than about 100 nm).
In some embodiments, the porous material includes mesoporous carbon material such as graphitic carbon or a carbon molecular sieve. Suitable examples include graphene, carbon nanotubes, disordered carbons, ordered mesoporous carbon, and BP-2000.
Synthesizing a phosphorus-containing porous material described herein includes contacting a porous material with a phosphorus-containing compound to yield a wet phosphorus-containing porous material, removing water from the wet phosphorus-containing porous material to yield a dry phosphorus-containing porous material, and calcining the dry phosphorus-containing porous material to yield a catalyst having phosphorus coupled to the porous material. As described herein, the porous material may include a molecular sieve framework defining micropores bounded at least in part by 8-membered tetrahedral atom rings, 10-membered tetrahedral atom rings, 12-membered tetrahedral atom rings, or a combination thereof. In some cases, aluminum is removed from the molecular sieve framework before the molecular sieve framework is contacted with the phosphorus-containing compound. Other suitable porous materials include micro-mesoporous nanosilica and mesoporous graphitic carbon and carbon molecular sieves.
In one example, the phosphorus-containing compound is phosphoric acid. In other examples, the phosphorus-containing compound is an organic structure-directing agent (OSDA), such as tetra(n-butyl) phosphonium hydroxide, tetramethyl phosphonium hydroxide, tetraethyl phosphonium hydroxide, tetrapropyl phosphonium hydroxide.
Synthetic methods include dehydrating an oxygen-containing compound by contacting the oxygen-containing compound with phosphorus-containing catalysts described herein.
In some embodiments, the oxygen-containing compound is a cyclic ether, such as DMF. Contacting DMF with ethylene in a nonaqueous solvent in the presence of the catalyst yields a cycloadduct, and the cycloadduct is dehydrated in the presence of the catalyst to yield a product including p-xylene. A yield of the p-xylene is typically at least 90%, at least 93%, at least 95%, at least 97%, or at least 99%. The total yield of by-products, such as hexanedione, alkylated aromatic chemicals, and oligomers is typically less than 10%, less than 7%, less than 5%, less than 3%, or less than 1%. In some cases, before contacting the DMF and the ethylene, ethanol is contacted with the catalyst to yield ethylene. The ethylene then undergoes Diels-Alder cycloaddition with the DMF.
In some embodiments, the oxygen-containing compound is an alcohol. Examples of suitable alcohols include butanol, ethanol, and propanol (e.g., isopropanol). Contacting the alcohol with the phosphorus-containing catalyst yields an alkene. For example, contacting butanol with the phosphorus-containing catalyst yields butane, contacting ethanol with the phosphorus-containing catalyst yields ethylene, and contacting propanol with the phosphorus-containing catalyst yields propene.
In some embodiments, the oxygen-containing compound is a weak acid, such as lactic acid, and contacting lactic acid with the phosphorus-containing catalyst yields acrylic acid.
Synthesis of p-Xylene
To improve p-xylene yield, two phosphorus-containing siliceous zeolites, zeolite Beta (BEA) and self-pillared pentasil (SPP) zeolite were tested. These phosphorus-containing siliceous zeolites are inactive for alkylation and oligomerization reactions. The phosphorus-containing zeolite catalysts are not only active for p-xylene production but also lead to high yields. Phosphorus-containing zeolites are highly active, selective and stable catalysts. Phosphorus-containing BEA zeolite (P-BEA) with 12 membered-ring (12 MR) structures and phosphorus-containing self-pillared pentasil (P-SPP) zeolite nanosheets with 10 membered-ring (10 MR) structures exhibit activities up to 97% yield of p-xylene at 99% conversion of DMF.
Phosphorus-containing zeolite Beta (P-BEA) was synthesized by a post-synthetic route, according to which P was incorporated within zeolite BEA by calcining dealuminated zeolite BEA after impregnation with phosphoric acid (H3PO4). The synthesis procedure includes the dealumination of Al-BEA (Zeolyst, CP814E, Si/Al=12.5) using nitric acid, the impregnation of H3PO4 on the dealuminated zeolite BEA and the incorporation of phosphorus within the zeolite by calcination. The crystal structure and morphology of the zeolite BEA were preserved after the incorporation of phosphorus, as evidenced by their XRD patterns (
Phosphorus-containing self-pillared pentasil (P-SPP) was synthesized by a direct synthesis method using tetrabutylphosponium hydroxide (TBPOH) as an organic structure-directing agent (OSDA). After crystallization, the formed SPP zeolite containing the OSDA was subjected to calcination, resulting in the decomposition of the OSDA and incorporation of phosphorus within the zeolite (Table 1). In contrast, the use of tetrabutylammonium hydroxide (TBAOH) as the OSDA leads to SPP zeolite free of phosphorus active sites. The crystallinity and morphology of P-SPP are similar to those of pure silica SPP displaying orthogonally connected single-unit cell lamellae of MFI, as evidenced by the XRD patterns, TEM images and argon adsorption isotherms (
To further illustrate the performance of the phosphorus-containing catalysts, the temporal profile of the yield to p-xylene with reaction time, carbon balance and by-products versus DMF conversion are shown in
To verify the heterogeneous nature of the phosphorus catalytic sites, catalyst removal and recycle tests were conducted. In the catalyst removal test, the reaction of DMF was performed after separating the spent P-BEA catalyst from the reaction mixture. As shown in
31P solid state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) was performed to gain an insight into the chemical interaction of phosphorus with the silicate frameworks of the phosphorus-containing catalysts. As shown in
The phosphorus-containing zeolite materials are also active and selective for alcohol dehydration reactions. The dehydration of ethanol on P-SPP has been compared to ZSM-5, an aluminum containing zeolite. As shown in Table 3, at 400° C., with a flow rate of 30 mL/min and ethanol concentration of 8.15×10-6 mol/mL, 100% conversion of ethanol was achieved. P-SPP exhibited 96% selectivity to ethylene with a carbon balance of 98%. However, ZSM-5 exhibited 50.7% selectivity to ethylene with many other olefins and aromatics (24.3% to propylene, 11.6% to butene, 0.6% to pentene, and 12.7% to aromatics). The carbon balance for ZSM-5 is 74%, indicating significant coke formation on the ZSM-5 catalysts. It is believed the high selectivity to ethylene and slow catalyst deactivation is due at least in part to the acid sites from the phosphorus species.
Phosphorus-containing carbons (phosphorus on BP2000 carbon) and phosphorus supported on the meso-microprous silicate SBA-15 can also be selective catalysts. Table 4 lists results obtained with BP-2000 and phosphorus on SBA-15.
The phosphorus-containing catalysts can also be used as catalysts for alcohol dehydration. Table 5 shows vapor phase isopropanol dehydration over several phosphorus-containing catalysts with P-MFI and P-SPP being among the more active catalysts. Reaction conditions for the dehydration reactions summarized in Table 5 were as follows: 130° C., 30 torr isopropanol, helium carrier gas (25 sccm), catalysts calcined in-situ at 550° C. with a ramp of 5° C./min, total system pressure of 1.1 bar.
Commercial zeolite Al-BEA (Zeolyst, CP814E, Si/Al=12.5) was dealuminated by treatment with 70 wt % nitric acid (HNO3, Fisher Scientific). Typically, 0.5 g of the Al-BEA was mixed with 25 mL of 70 wt % HNO3 in a TEFLON-lined stainless steel autoclave. The autoclave was then put into an 80° C. oven for 24 h under a static condition. The dealuminated zeolite BEA (DeAl-BEA) was washed extensively with deionized water and dried overnight at 100° C. Wet impregnation was performed by stirring DeAl-BEA and the appropriate amount of 85 wt % phosphoric acid (H3PO4, Sigma-Aldrich) in deionized water. The impregnated sample was dried 90° C. overnight, followed by calcination in a tube furnace with dry air to 600° C. for 25 min.
P-SPP was prepared by adding tetra(n-butyl) phosphonium hydroxide (TBPOH, 40 wt %, Sigma-Aldrich) as a structure-directing agent (SDA) dropwise into tetraethylorthosilicate (TEOS, 98%, Sigma-Aldrich) under stirring. To this mixture, deionized water was then added and stirred for 24 h. The mixture became a clear sol with composition 1 SiO2:0.3 TBPOH:10 H2O:4 EtOH. The sol was sealed in a TEFLON-lined stainless steel autoclave and heated for 3 days in an oven at 115° C. Si-SPP can be prepared with tetra(n-butyl)ammonium hydroxide solution (TBAOH, 40 wt %, Sigma-Aldrich) instead of TBPOH. After crystallization, the solid product was washed with deionized water by centrifugation and decanting of the supernatant. This process was repeated until the pH of the final supernatant was less than 9. Subsequently, the collected sample was dried at 90° C. overnight and calcined in a tube furnace at 550° C. for 12 h under dry air. Without further treatment P-SPP is directly synthesized. The phosphorus content can be adjusted by washing with water and/or by impregnation with phosphoric acid followed by calcination.
P-CELITE was prepared through an impregnation method. First, CELITE S (Diatomaceous silica, Sigma-Aldrich) was calcined at 500° C. for 5 h under air. Then, 1 g of the calcined CELITE was ion-exchanged with 100 mL of 0.2 M NH4NO3 solution at 60° C. for 20 h. The resulting product was filtered and washed by deionized water thoroughly, followed by drying overnight. The solid was calcined at 500° C. for 5 h under air. Thereafter, 1 g of the calcined powder was mixed with 4 mL of 0.75 M H3PO4 solution, and then dried at 90° C. overnight. The dried mixture was calcined at 500° C. for 5 h under air.
P-Al-BEA was prepared by impregnation of H3PO4 on zeolite Al-BEA (Zeolyst, CP814E, Si/Al=12.5), according to the same procedure described in the preparation of P-BEA.
Synthesis of siliceous BEA (Si-BEA)
Pure Si-BEA was synthesized as described in M. A. Camblor, A. Corma, S. Valencia, Spontaneous nucleation and growth of pure silica zeolite-beta free of connectivity defects, Chemical Communications, 2365-66 (1996). Typically, 8.72 g of tetraethylammonium hydroxide (TEAOH, 35 wt %, Alfa Aesar or SACHEM) was mixed in 1.24 g of deionized water. To this mixture, tetraethylorthosilicate (TEOS, 98%, Sigma-Aldrich) was added and stirred for 7 h at room temperature. Thereafter, 0.86 g of HF (48%, Sigma-Aldrich) was added, and the mixture became a white solid with composition 1 SiO2:0.54 TEAOH:0.54 HF:7.25 H2O. The resulting solid was sealed in a TEFLON-lined stainless steel autoclave, followed by crystallization for 2 days in an oven at 140° C. Subsequently, the solid product was extensively washed with deionized water by vacuum filtration. The collected sample was dried at 90° C. overnight and calcined in a tube furnace at 550° C. for 12 h under dry air.
Wet impregnation was performed by stirring the silica matrix of interest and the appropriate amount of 85 wt % phosphoric acid (H3PO4, Sigma-Aldrich) in deionized water. Three different silica materials were used: 1) silica gel (DAVISIL Grade 636, Sigma-Aldrich), 2) monodisperse silica nanoparticles with 35 nm size, synthesized as described in T. Yokoi, Y. Sakamoto, O. Terasaki, Y. Kubota, T. Okubo and T. Tatsumi, Periodic Arrangement of Silica Nanospheres Assisted by Amino Acids, Journal of the American Chemical Society, 128, 13664-13665 (2006), and 3) pure siliceous BEA zeolite (Si-BEA). The resulting impregnated sample was dried 90° C. overnight, followed by calcination in a tube furnace with dry air to 600° C. for 25 min.
Mesoporous SBA-15 was synthesized as described in Sayari, A.; Han, B.-H.; Yang, Y., Simple Synthesis Route to Monodispersed SBA-15 Silica Rods. J. Am. Chem. Soc. 2004, 126, 14348-14349. Pluronic P-123 was added to a well-mixed solution of deionized water and HCl. TEOS was then added to this solution with a composition of 1 SiO2:5.7 HCl:0.017 P-123:192.7 H2O. The solution was stirred for five minutes and then maintained at 308 K under static conditions for 20 h. Following this, the solution was maintained at elevated temperatures under static conditions for 24 h. The temperature during this step determined the microporosity and mesoporosity of the synthesized SBA-15 rods. Three SBA-15 samples were synthesized at temperatures of 308 K during this step, respectively. The product was collected by filtration and washed with deionized water followed by drying at 343 K for 10 h. To remove the surfactant, the sample was calcined at 823 K for 12 h with a ramping rate of 0.5 K/min under flowing dry air. Wet impregnation was performed by stirring 0.4 g of synthesized SBA-15 and the 18.2 mL of 85 wt % phosphoric acid (H3PO4, Sigma-Aldrich) in 3.33 mL of deionized water. The impregnated sample was dried 90° C. overnight, followed by calcination in a tube furnace with dry air to 600° C. for 25 min.
Wet impregnation was performed by stirring 0.4 g of carbon black, BP2000, and 18.2 mL of 85 wt % phosphoric acid (H3PO4, Sigma-Aldrich) in 3.33 mL of deionized water. The impregnated sample was dried at 90° C. overnight, followed by calcination in a tube furnace with helium flow to 600° C. for 30 min.
Powder X-ray diffraction (XRD) patterns of the samples were recorded on an XRD diffractometer (X'Pert Pro, PANalytical) operated at 45 kV of an acceleration voltage and 40 mA of a current using Cu Kα radiation. The data were collected over 4-40° of a 20 range. A scanning electron microscope (SEM, Magellan 400, FEI) was used to examine the morphology of the products. Prior to the SEM measurement, the samples were coated with platinum/palladium alloy. To take TEM images, aqueous suspensions of the zeolite samples were prepared. TEM specimens were made by placing droplets of the suspension onto the copper grid coated with ultra-thin carbon film and holey carbon film (Ted Pella Inc.), followed by air-drying at room temperature. TEM imaging was performed using a CCD camera on an FEI Tecnai G2 F30 TEM operating at 300 kV. Elemental analysis was performed on inductively coupled plasma optical emission spectroscopy (ICP-OES, iCap 6500 Dual view, Thermo Scientific) in Analytical Geochemistry Lab, Department of Earth Sciences in University of Minnesota. Argon adsorption-desorption isotherms were measured at 87 K by using an automated gas sorption analyzer (Autosorb iQ2, Quantachrome) after the samples were degassed at 300° C. under vacuum.
In order to quantify the concentration of Brønsted acid sites on a catalyst, isopropylamine temperature program decomposition (IPA-TPD) coupled with thermogravimetric analysis was performed on a TA instrument Q500, following a procedure developed by Gorte et al. (R. J. Gorte, What do we know about the acidity of solid acids?, Catalysis Letters, 62:1-13 (1999); W. E. Farneth, R. J. Gorte, Methods for Characterizing Zeolite Acidity, Chemical Reviews, 95:615-35 (1995)). Typically, 0.01 g of catalyst was first pretreated at 550° C. for 1 h by flowing He with a rate of 100 cm3 min−1 in order to remove the water and other impurities from the catalyst surface. After the sample cooled down to 120° C., IPA was dosed into the system under a He flow. When the sample was saturated with IPA, only He flowed into the system for 1 h to eliminate weakly adsorbed IPA on the catalyst. Subsequently, system temperature was increased to 700° C. with a ramping rate of 10° C. min−1. The total Brønsted acid site concentration was determined by the weight difference between 300° C. and 400° C., which is the temperature range where IPA decomposes into propylene and amine on the Brønsted acid sites.
Solid state NMR spectra were recorded using a Bruker DSX-500 spectrometer and a Bruker 4 mm MAS probe. The operating frequency is 202.5 MHz for 31P. Powder samples packed into 4 mm zirconia rotors were spun at ambient conditions. For MAS NMR experiments, a radiofrequency pulse of 4 μs-π/2 and strong 1H decoupling pulse with two pulse phase modulation (TPPM) were employed for signal averaging of 31P MAS NMR. Chemical shifts were externally referenced to concentrated H3PO4 for 31P NMR.
Diels-Alder Reaction and Dehydration of Dimethylfuran (DMF) with Ethylene
In a bench-top reactor (Parr), 50 mL of 1.35 M DMF (>98%, Alfa Aesar) in n-heptane (99%, Alfa Aesar) including 0.08 M n-tridecane (>98%, Alfa Aesar, internal standard) was mixed with the appropriate amount of a catalyst. The reactor was purged with nitrogen at room temperature under 1000 rpm of stirring. The catalyst acid concentration present in the system was defined as the total number of acid sites of the catalyst divided by the reactant volume. Subsequently, the mixture was heated to 250° C. by a 4848 temperature control unit (Parr). At 250° C., ethylene gas (Airgas) with 38 bar partial pressure was introduced into the system, and the reaction was allowed to proceed. During the entire reaction, the total pressure of the reactor was maintained at 62 bar. Time course of the reaction was monitored by taking samples (0.5 mL) for analysis at specified time intervals. The quantitative analysis of the sample was performed by Agilent 6890 gas chromatography (GC) equipped with a flame ionization detector and a Restek RTX-VMS capillary column (30.0 m length, 0.25 mm id, 1.4 μm film thickness). The products, DMF, p-xylene (>99%, Sigma-Aldrich) and 2,5-hexanedione (97%, Alfa Aesar) were identified by comparing the retention times of each standard chemical, and also cross-checked on a GC-MS system (7890B GC, Agilent). The alkylated products were quantified by using the response factor (RF) for 1-methyl-4-propylbenzene, while the oligomer contents were estimated using the additive RF of DMF and p-xylene. The concentration of cycloadduct, the intermediate produced from the Diels-Alder reaction of DMF and ethylene, was estimated by using the RF for p-xylene, following C. C. Chang et al., Lewis acid zeolites for tandem Diels-Alder cycloaddition and dehydration of biomass-derived dimethylfuran and ethylene to renewable p-xylene, Green Chem, 18:1368-76 (2016) and C. C. Chang, S. K. Green, C. L. Williams, P. J. Dauenhauer, W. Fan, Ultra-selective cycloaddition of dimethylfuran for renewable p-xylene with H-BEA, Green Chem, 16:585-88 (2014).
After 24 h of 1.35 M DMF reaction with ethylene at 250° C., the spent catalyst was removed from the reaction mixture by centrifugation. To this mixture, appropriate fresh DMF was added to ensure that DMF concentration was 1.35 M in n-heptane. Next, the DMF reaction proceeded, following the procedure described herein.
After 24 h of 1.35 M DMF reaction with ethylene at 250° C., the catalyst was separated from the reaction mixture, washed with n-heptane 3 times by centrifugation, and dried at 90° C. overnight. The dried solid was calcined in a tube furnace with dry air to 550° C. for 12 h. For the 1st recycling test, DMF was catalyzed by the mixed catalyst (fresh catalyst:spent catalyst=2:8, weight ratio). After 24 h of the reaction, the used catalyst was treated in the same way as the one for the 1st recycling test. For the 2nd recycling test, the fresh catalyst was mixed with the spent catalyst that was used in the 1st recycling test (fresh catalyst:spent catalyst=2:8, weight ratio). In the same manner, 3rd recycling test was also examined.
The ethanol dehydration reaction was carried out in a continuous flow fixed-bed quartz reactor of ½ in. O.D. coupled with a vertical heating jacket. Zeolite was placed in the middle of the reactor by a quartz frit. Prior to the reactions, the zeolite was activated at 550° C. under 30 mL/min air flow for 2 hrs. Thereafter, the reactor was cooled down to the reaction temperature with a constant He flow. Ethanol was introduced into the reactor by a liquid pump (Fisher, KDS100) with He as carrier flow. The gas line was heated to 80° C. to prevent condensation of ethanol. The reaction occurred at 1 atm for 10 min, and the products were collected using a 500 mL air bag (SKC, Tedlar). The products were identified using an Agilent 7890B GC coupled with FID detector.
This application claims the benefit of U.S. Application Ser. No. 62/402,238 entitled “USE OF PHOSPHORUS-CONTAINING SOLID CATALYSTS” filed Sep. 30, 2016; U.S. Application Ser. No. 62/410,919 entitled “METHODS OF FORMING ISOPRENE FROM 2-METHYL-1,4-BUTANEDIOL, DERIVATIVES OR COMBINATIONS THEREOF” filed Oct. 21, 2016; U.S. Application Ser. No. 62/410,922 entitled “METHODS OF FORMING DIENES FROM TETRAHYDROFURAN, DERIVATIVES OR COMBINATIONS THEREOF” filed Oct. 21, 2016; U.S. Application Ser. No. 62/414,302 entitled “PHOSPHORUS-CONTAINING SOLID CATALYSTS AND METHODS OF USE THEREOF” filed Oct. 28, 2016; U.S. Application Ser. No. 62/419,202 entitled “METHODS OF FORMING ISOPRENE FROM 2-METHYL-1,4-BUTANEDIOL, DERIVATIVES OR COMBINATIONS THEREOF” filed Nov. 8, 2016; and U.S. Application Ser. No. 62/419,247 entitled “METHODS OF FORMING DIENES FROM TETRAHYDROFURAN, DERIVATIVES, OR COMBINATIONS THEREOF” filed Nov. 8, 2016, all of which are incorporated by reference herein in their entirety.
This work was supported by the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under award number DE-SC0001004. The government has certain rights in the invention.
Filing Document | Filing Date | Country | Kind |
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PCT/US17/54558 | 9/29/2017 | WO | 00 |
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62419247 | Nov 2016 | US | |
62419202 | Nov 2016 | US | |
62414302 | Oct 2016 | US | |
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62402238 | Sep 2016 | US |