Highly active and selective Cs2.5H0.5PW12O40/SBA-15 composite material in the oxidation of cyclopentane-1,2-diol to glutaric acid by aqueous H2O2

In the present work, for the first time the Cs_2.5H_0.5PW₁₂O₄₀/SBA-15 catalysts were prepared as highly efficient catalysts for the direct production of glutaric acid (GAC) via selective oxidation of cyclopentane-1,2-diol by using aqueous hydrogen peroxide as the green oxidant. The yield of GAC is higher than 88%. The fresh catalyst and the recovered ones were all characterized by XRD, FT-IR, Raman and ³¹P MAS NMR to reveal the structure change during the reaction. XRD results revealed that the Cs_2.5H_0.5PW₁₂O₄₀/SBA-15 catalysts keep the crystalline structure of the as-prepared Cs_2.5H_0.5PW₁₂O₄₀. And it is found that the structure of the Cs_2.5H_0.5PW₁₂O₄₀/SBA-15 catalysts was retained after the reaction, as determined by Raman, FT-IR and ³¹P MAS NMR. The new Cs_2.5H_0.5PW₁₂O₄₀/SBA-15 catalyst can be easily recycled after reaction and can be reused six times, indicating its excellent stability.     

Effect of CsxH3?xPW12O40 addition on the catalytic performance of ZnFe2O4 in the oxidative dehydrogenation of n-butene to 1,3-butadiene

Oxidative dehydrogenation of n-butene to 1,3-butadiene over ZnFe₂O₄ catalyst mixed with Cs _x H_3−x PW₁₂O₄₀ heteropolyacid (HPA) was performed in a continuous flow fixed-bed reactor. The effect of Cs _x H_3−x PW₁₂O₄₀ addition on the catalytic performance of ZnFe₂O₄ was investigated. Cs _x H_3−x PW₁₂O₄₀ itself showed very low catalytic performance in the oxidative dehydrogenation of n-butene. However, addition of small amount of Cs _x H_3−x PW₁₂O₄₀ into ZnFe₂O₄ enhanced the catalytic performance of ZnFe₂O₄ catalyst. The catalytic performance of ZnFe₂O₄-Cs _x H_3−x PW₁₂O₄₀ mixed catalysts was closely related to the surface acidity of Cs _x H_3−x PW₁₂O₄₀. Among the catalysts tested, ZnFe₂O₄-Cs_2.5H_0.5 PW₁₂O₄₀ mixed catalyst showed the best catalytic performance. Strong acid strength and large surface acidity of Cs_2.5H_0.5PW₁₂O₄₀ was responsible for high catalytic performance of ZnFe₂O₄-Cs_2.5H_0.5PW₁₂O₄₀ mixed catalyst. Thus, Cs_2.5H_0.5PW₁₂O₄₀ could be utilized as an efficient promoter and diluent in formulating ZnFe₂O₄ catalyst for the oxidative dehydrogenation of n-butene.     

负载型Cs2.5H0.5PW12O40醚化催化剂的制备与催化性能

制备了负载型磷钨酸铯(Cs_2.5H_0.5PW₁₂O₄₀)催化剂，考察了载体种类、载体性质、制备方法和制备条件对催化剂性能的影响,对制备的催化剂进行了表征，并考察了负载型Cs_2.5H _0.5PW₁₂O₄₀作为醚化催化剂的催化活性.结果表明,大孔硅胶是Cs_2.5H_0.5PW₁₂O₄₀的适宜载体，硅胶的钠含量越低制备的Cs_2.5H_0.5PW₁₂O₄₀/SiO₂催化剂的活性越高.采用一步法和二步法制备的Cs_2.5H_0.5PW₁₂O₄₀/SiO₂催化剂均具有较强的酸性、催化活性以及良好的稳定性,可以替代液体酸和阳离子交换树脂,成为一种环境友好的固体酸催化剂.     

Catalytic synthesis of N-alkylacrylamide from acrylonitrile and 1-adamantanol with a novel solid heteropoly compound

Catalytic synthesis of N-adamantylacrylamide from acrylonitrile and 1-adamantanol has been studied over various solid and liquid acids. Solid acids such as Cs_2.5H_0.5PW₁₂O₄₀, Amberlyst 15, Nafion, and Nafion–SiO₂ composite gave yields higher than 97% at 373 K, and were superior in yield to liquid acids like p-toluenesulfonic acid, H₃PW₁₂O₄₀, and H₂SO₄. It was further demonstrated that Cs_2.5H_0.5PW₁₂O₄₀ exhibited the highest catalytic performance for this reaction in the presence of excess water. This revised version was published online in July 2006 with corrections to the Cover Date.     

Direct synthesis of hydrogen peroxide from hydrogen and oxygen over palladium-exchanged insoluble heteropolyacid catalysts

Palladium-exchanged insoluble heteropolyacid (Pd_0.15Cs_xH_2.7?xPW₁₂O₄₀) catalysts were prepared with a variation of cesium content (x = 2.0, 2.2, 2.5, and 2.7), and were applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. Pd_0.15Cs_xH_2.7?xPW₁₂O₄₀ showed high catalytic performance even in the absence of H₂SO₄ additive, indicating that Pd_0.15Cs_xH_2.7?xPW₁₂O₄₀ acted as an efficient catalyst and served as an alternate acid source in the reaction. The catalytic performance of Pd_0.15Cs_xH_2.7?xPW₁₂O₄₀ increased with increasing surface acidity of the catalyst. Among the catalysts tested, Pd_0.15Cs_2.5H_0.2PW₁₂O₄₀ catalyst with the largest surface acidity showed the highest yield for hydrogen peroxide.     

Catalytic decomposition of 2,3-dihydrobenzofuran to monomeric cyclic compounds over Pd/XCs2.5H0.5PW12O40/OMC (ordered mesoporous carbon) (X = 10–30 wt.%) catalysts

A series of Pd/XCs_2.5H_0.5PW₁₂O₄₀/OMC (ordered mesoporous carbon) (X = 10, 15, 20, 25, and 30 wt.%) catalysts with different Cs_2.5H_0.5PW₁₂O₄₀ contents (X, wt%) were prepared by a sequential incipient wetness impregnation method for use in the catalytic decomposition of 2,3-dihydrobenzofuran to monomeric cyclic compounds. 2,3-Dihydrobenzofuran was used as a lignin model compound for representing β-5 linkage of lignin. Acidity of Pd/XCs_2.5H_0.5PW₁₂O₄₀/OMC catalysts served as an important factor determining the catalytic performance in the reaction. Conversion of 2,3-dihydrobenzofuran and total yield for main products (2-ethylphenol and ethylcyclohexane) increased with increasing acidity of Pd/XCs_2.5H_0.5PW₁₂O₄₀/OMC catalysts.     

A Comparison of Catalytic Properties of Cs x H3−x PW12O40 Salts of Various Cesium Contents in Gas Phase and Liquid Phase Reactions

The cesium salts Cs _x H_3?x PW₁₂O₄₀ of Cs content x = 2 up to x = 3 were tested as the catalysts in the gas and liquid phase reactions. Dehydration of ethanol and transesterification of triglycerides with methanol were selected as the catalytic reactions. Apart from the standard preparation, the catalysts were prepared by two-stage procedure with methanol or water as a solvent. The Cs-salts were characterized by FT-IR, XRD, scanning electron microscopy and energy dispersive X-ray techniques. In turn, the influence of Cs-salts composition on the pH and conductivity of their aqueous colloidal solutions was investigated. The results obtained by the latter techniques were also characteristic for acidity of surface layer of colloidal particles because of surface layer-solution equilibrium. It has been shown that the secondary structure of acidic cesium salts existing in crystalline samples (solid solution of H₃PW₁₂O₄₀ in Cs₃PW₁₂O₄₀) changes after contacting with polar medium to the system consisting most probably of Cs₃PW₁₂O₄₀ core with epitaxial layer of heteropolyacid. This is result of the protons migration from bulk to surface layer of primary particles enhanced by polar medium. It strongly influences the surface acidity of primary particles as well as the activity of Cs-salts in transesterification of triglycerides with methanol. In such polar medium, Cs₂HPW₁₂O₄₀ salt becomes the most active catalyst, more active than Cs_2.5H_0.5PW₁₂O₄₀. An accumulation of partial glycerides and in particular glycerol on the surface of primary particles of Cs-salts resulted in relatively low maximum conversion of triglycerides, most probably due to partial blockage of the catalytic centers. This effect and the almost constant activity of Cs-salts under recycling use in the transesterification experiments are considered to be experimental evidences that methanolysis over Cs-salts was accomplished with the participation of surface protons.     

An inorganic/organic self-humidifying composite membranes for proton exchange membrane fuel cell application

With an aim to operate the proton exchange membrane fuel cells (PEMFCs) with dry reactants, an inorganic/organic self-humidifying membrane based on sulfonated polyether ether ketone (SPEEK) hybrid with Cs_2.5H_0.5PW₁₂O₄₀ supported Pt catalyst (Pt-Cs2.5 catalyst) has been investigated. The Pt-Cs2.5 catalysts incorporated in the SPEEK matrix provide the site for catalytic recombination of permeable H₂ and O₂ to form water, and meanwhile avoid short circuit through the whole membrane due to the insulated property of Cs_2.5H_0.5PW₁₂O₄₀ support. Furthermore, the Pt-Cs2.5 catalyst can adsorb the water and transfer proton inside the membrane for its hygroscopic and proton-conductive properties. The structure of the SPEEK/Pt-Cs2.5 composite membrane was characterized by XRD, FT-IR, SEM and EDS. Comparison of the physicochemical and electrochemical properties, such as ion exchange capacity (IEC), water uptake and proton conductivity between the plain SPEEK and SPEEK/Pt-Cs2.5 composite membrane were investigated. Additive stability measurements indicated that the Pt-Cs2.5 catalyst showed improved stability in the SPEEK matrix compared to the PTA particle in the SPEEK matrix. Single cell tests employing the SPEEK/Pt-Cs2.5 self-humidifying membrane and the plain SPEEK membrane under wet or dry operation conditions and primary 100 h fuel cell stability measurement were also conducted in the present study.     

Polyoxometalate as effective catalyst for the deep desulfurization of diesel oil

Aiming at the deep desulfurization of the diesel oil, a comparison of the catalytic effects of several Keggin type POMs, including H₃PW_xMo_12?xO₄₀ (x = 1, 3, 6), Cs_2.5H_0.5PW₁₂O₄₀, and H₃PW₁₂O₄₀, was made, using the solution of DBT in normal octane as simulated diesel oil, H₂O₂ as oxidant, and acetonitrile as extractant. H₃PW₆Mo₆O₄₀ was found to be the best catalyst, with a desulfurization efficiency of 99.79% or higher. Hence, it is promising for the deep desulfurization of actual ODS process. The role of the main factors affecting the process including temperature, O/S molar ratio, initial sulfur concentration, and catalyst dosage, was investigated, whereby the favourable operating conditions were recommended as T = 60 °C, O/S = 15, and a catalyst dosage of 6.93 g (H₃PW₆Mo₆O₄₀)/L (simulated diesel). With the aid of GC–MS analysis, sulfone species was confirmed to be the only product after reaction for 150 min. Furthermore, macro-kinetics of the process catalyzed by H₃PW₆Mo₆O₄₀ was studied, from which the reaction orders were found to be 1.02 to DBT and 0.38 to H₂O₂, and the activation energy of the reaction was found to be 43.3 kJ/mol. Moreover, the catalyst recovered demonstrated almost the same activity as the fresh.     

Catalytic decomposition of benzyl phenyl ether to aromatics over cesium-exchanged heteropolyacid catalyst

Cesium-exchanged Cs _x H_3.0−x PW₁₂O₄₀ (X=2.0–3.0) heteropolyacid catalysts were prepared and applied to the decomposition of benzyl phenyl ether to aromatics. Benzyl phenyl ether was chosen as a lignin model compound for representing α-O-4 bond in lignin. Phenol, benzene, and toluene were mainly produced by the decomposition of benzyl phenyl ether. Conversion of benzyl phenyl ether and total yield for main products (phenol, benzene, and toluene) were closely related to the surface acidity of Cs _x H_3.0−x PW₁₂O₄₀ (X=2.0–3.0) heteropolyacid catalyst. Conversion of benzyl phenyl ether and total yield for main products increased with increasing surface acidity of the catalyst. Among the catalysts tested, Cs_2.5H_0.5PW₁₂O₄₀ with the largest surface acidity showed the highest conversion of benzyl phenyl ether and total yield for main products.     

Production of middle distillate through hydrocracking of paraffin wax over Pd0.15CsxH2.7?xPW12O40 catalysts: Effect of cesium content and surface acidity

Palladium-exchanged heteropolyacid (Pd_0.15Cs _x H_2.7−x PW₁₂O₄₀) catalysts were prepared by an ion-exchange method with a variation of cesium content (x=2.0, 2.2, 2.5, and 2.7) for use in the production of middle distillate through hydrocracking of paraffin wax. Surface acidity of Pd_0.15Cs _x H_2.7−x PW₁₂O₄₀ catalysts determined by NH₃-TPD experiments showed a volcano-shaped trend with respect to cesium content. Surface acidity of the catalysts played an important role in determining the catalytic performance in the hydrocracking of paraffin wax. Conversion of paraffin wax increased with increasing surface acidity of the catalyst, while yield for middle distillate showed a volcano-shaped curve with respect to surface acidity of the catalyst. Among the catalysts tested, Pd_0.15Cs_2.7PW₁₂O₄₀ catalyst with moderate surface acidity showed the best catalytic performance.     

Biodiesel production from soybean oil catalyzed by multifunctionalized Ta2O5/SiO2-[H3PW12O40/R] (R = Me or Ph) hybrid catalyst

Mesoporous Ta₂O₅ materials functionalized with both alkyl group and a Keggin-type heteropoly acid, Ta₂O₅/SiO₂-[H₃PW₁₂O₄₀/R] (R = Me or Ph), was prepared by a single step sol–gel co-condensation method followed by a hydrothermal treatment in the presence of a triblock copolymer surfactant. The catalytic performance of the resulting multifunctionalized organic–inorganic hybrid materials was evaluated by a direct use of soybean oil for biodiesel production in the presence of 20 wt% myristic acid under atmosphere refluxing, and the influences of the catalyst preparation approaches, functional component loadings, and molar ratios of oil to methanol on the catalytic activity of the Ta₂O₅/SiO₂-[H₃PW₁₂O₄₀/R] were studied. In addition, the recyclability of the hybrid materials was evaluated via four catalytic runs. Finally, the network structures of the hybrid materials and the functions of the incorporated alkyl groups on the catalytic activity of the materials were put forward.     

A pronounced catalytic activity of heteropoly compounds supported on dealuminated USY for liquid-phase esterification of acetic acid with n-butanol

12-Phosphotungstic acid and its cesium salts supported on a dealuminated ultra-stable Y zeolite were prepared, and showed the high catalytic activity in the liquid-phase esterification of acetic acid with n-butanol. The supported Cs_2.5H_0.5PW₁₂O₄₀ catalyst gave a high conversion of n-butanol of 94.6% and a selectivity for n-butyl acetate of 100%, accompanying the high water-tolerance and catalytic reusability without regeneration.     

Cationic Polymerization Using Heteropolyacid Salt Catalysts

Acid catalysts are used in the production of several commercially important lubricant additives, including dispersants and antioxidants. While the use of conventional mineral and Lewis acids still dominate existing production, heterogeneous solid acid catalysts provide a future option for cost reduction and pollution prevention. The heteropolyacids discussed in this presentation are based on the parent phosphotungstic acid, H₃PW₁₂O₄₀, which has been studied for many years as solid acid catalysts especially by Japanese researchers. A particular class of heterpolyacid salts of the formula (M⁺)_2.5H_0.5PW₁₂O₄₀ exhibit enhanced catalytic activity, which is believed to be due to the formation of a phase with nano-sized crystallites, as has been reported by Misono and coworkers. This class of heteropolyacid salts has been successfully applied by Lubrizol researchers to the production of high-reactivity polyisobutylene, a polymer used in the production of dispersants for commercial lubricants. Most notably, the catalyst of the formula (NH₄ ⁺)_2.5H_0.5PW₁₂O₄₀ provides high conversion to the desired reactive vinylidene isomer and a unique polymer molecular weight distribution, which results in improved performance characteristics when compared to existing commercial AlCl₃ and BF₃ catalysts. Catalyst performance is effectively optimized by catalyst concentration in a slurry reactor, catalyst calcination temperature and loading on a silica support. This class of catalysts has also been successfully applied to a number of other acid-catalyzed processes for the production of additives, including for the antioxidant nonyl diphenylamine.     

Direct preparation of dichloropropanol from glycerol and hydrochloric acid gas in a solvent-free batch reactor: Effect of experimental conditions

Solvent-free direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas was carried out in a batch reactor with a variation of reaction conditions (agitation speed, reaction time, reaction temperature, and reaction pressure), amount of H₃PW₁₂O₄₀ catalyst, and amount of water absorbent (silica gel blue). The reaction was conducted at high agitation speed in order to avoid mass transfer limitation between glycerol and hydrochloric acid gas. In the direct preparation of DCP from glycerol and hydrochloric acid gas, DCP formation was increased with increasing reaction time, reaction temperature, and reaction pressure. Chlorination of glycerol occurred via the following consecutive reaction steps: glycerol→monochloropropanediol (MCPD)→dichloropropanol (DCP)→trichloropropane (TCP). Reaction rate decreased in the order of first-step reaction>second-step reaction>third-step reaction. The presence of H₃PW₁₂O₄₀ catalyst and water absorbent (silica gel blue) enhanced the formation of DCP. DCP formation was increased with increasing the amount of H₃PW₁₂O₄₀ catalyst and water absorbent (silica gel blue). Strong Brönsted acid site of H₃PW₁₂O₄₀ catalyst and water removal from the reaction system favorably served in improving DCP formation.     

Effect of reaction conditions on the catalytic performance of H3PW12O40 heteropolyacid catalyst in the direct preparation of dichloropropanol from glycerol in a liquid-phase batch reactor

Direct chlorination of glycerol to dichloropropanol (DCP) was conducted in a liquid-phase batch rector using homogeneous H₃PW₁₂O₄₀ heteropolyacid (HPA) catalyst. The effect of reaction conditions (reaction time, reaction pressure, reaction temperature, and catalyst amount) on the catalytic performance of H₃PW₁₂O₄₀ in the direct preparation of DCP from glycerol was examined. The optimum reaction pressure and reaction temperature were found to be 10 bar and 130 °C, respectively. The reaction temperature was more crucial than the reaction pressure in improving the selectivity to DCP. Selectivity to DCP increased with increasing reaction time and with increasing catalyst amount. Acid sites of H₃PW₁₂O₄₀ catalyst favorably devoted to the chlorination of glycerol. H₃PW₁₂O₄₀ served as an efficient catalyst in the direct preparation of DCP from glycerol under the mild reaction conditions.     

Micropore size distribution by argon porosimetry for cesium hydrogen salts of 12-tungstophosphoric acid

Micropore size distributions of Cs_2.1H_0.9PW₁₂O₄₀ and 0.5 wt% Pt-Cs_2.1H_0.9PW₁₂O₄₀ as well as H-ZSM-5, H-Y and AlPO₄-5 as standard porous materials were analyzed by Ar porosimetry, assuming cylindrical pores consisting of oxide ions. The calculated pore-widths of H-ZSM-5, HY and AlPO₄-5 were in agreement with the pore-opening sizes determined by XRD. The Ar porosimetry demonstrated that Cs_2.1H_0.9PW₁₂O₄₀ and 0.5 wt% Pt-Cs_2.1H_0.9PW₁₂O₄₀ possess only ultramicropores having widths of about 0.5 nm. Adsorption of various molecules revealed that the pore widths of these heteropoly compounds were in the range 0.43–0.59 nm, which is consistent with the results of the Ar porosimetry. In conclusion, nearly uniformly sized micropores are formed on both Cs_2.1H_0.9PW₁₂O₄₀ and 0.5 wt% Pt-Cs_2.1H_0.9PW₁₂O₄₀.     

In situ 13C MAS NMR Study on the Mechanism of Butane Isomerization Over Catalysts with Different Acid Strength

Reaction mechanism of skeletal isomerization of n-butane over sulfated zirconia (SZ), Cs_2.5H_0.5PW¹²O₄₀ (Cs_2.5) and H-form mordenite (H-MOR) catalysts was studied using ₁₃C MAS NMR with ₁₃C-labeled n-butane. The isomerization of n-butane over SZ type catalysts proceeds predominantly via a monomolecular mechanism below 333 K and gradually changes to a bimolecular alkylation-β-scission mechanism as the reaction temperature is increased to 423 K. Iron promoter in SZ catalyst facilitates the bimolecular process. The n-butane isomerization over Cs_2.5 also proceeds mainly via a monomolecular mechanism below 373 K. The bimolecular mechanism becomes significant as the reaction temperature is increased to 423 K. On both SZ and Cs_2.5 catalysts hydrogen inhibits the isomerization reaction, in particular the bimolecular process. In contrast, the n-butane isomerization over H-MOR with relatively moderate acid strength proceeds mainly via a bimolecular mechanism at 473 K. The kinetics of n-butane isomerization on SZ below 333 K and Cs_2.5 below 373 K are well represented by the Langmuir–Hinshelwood equation for a reversible first order surface reaction, further supporting that a monomolecular mechanism proceeds primarily on SZ and Cs_2.5 catalysts at early reaction stage. All results suggest that the stronger the acidity of the catalyst the lower the reaction temperature of n-butane isomerization and the more contribution of the monomolecular mechanism. The overall mechanism of 1−₁₃C-n-butane reaction on SZ, Cs_2.5 and H-MOR catalysts including ₁₃C scrambling and butane isomerization is proposed.     

Hydrogenolysis of Glycerol to Propanediol Over Ru: Polyoxometalate Bifunctional Catalyst

Ruthenium-doped (5 wt%) acidic heteropoly salt Cs_2.5H_0.5[PW₁₂O₄₀] (CsPW) is an active bifunctional catalyst for the one-pot hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) in liquid phase, providing 96% selectivity to 1,2-PDO at 21% glycerol conversion at 150 °C and an unprecedented low hydrogen pressure of 5 bar. Rhodium catalyst, 5%Rh/CsPW, although less active, shows considerable selectivity to 1,3-PDO (7.1%), with 1,2-PDO being the main product (65%).     

Sulfonated Beet Pulp as Solid Catalyst in One-Step Esterification of Industrial Palm Fatty Acid Distillate

In this research a new heterogeneous catalyst has been prepared for biodiesel production. The catalyst was prepared by sulfonating industrial sugar waste. Unlike homogeneous catalysts, which require further purification and separation from the biodiesel production reaction media, this inexpensive synthetic catalyst does not need to go through an additional separation process. This advantage consequently minimizes the total application costs. The catalyst was prepared by partially carbonizing sugar beet pulp at 400 °C. The carbonization product was then sulfonated with concentrated H₂SO₄ vapor in order to produce a solid catalyst. The prepared catalyst was used in the esterification reaction between palm fatty acid distillate (PFAD) and methanol. The effects of the temperature, methanol/PFAD ratio, reaction time and catalyst dosage on the efficiency of the production were individually investigated. The optimum biodiesel production occurred at 85 °C, a reaction time of 300 min, catalyst dosage of 3 g and methanol/PFAD ratio of 5:1 (mol/mol), lowering the acid value from 198 to 13.1 (mg KOH/g oil) or the equivalent, with a fatty acid methyl ester yield of around 92 %. The results suggest that the synthesized inexpensive catalyst is useful for biodiesel production from PFAD.