Tungstophosphoric Acid Catalyst Research Articles

Kinetics of benzene alkylation with 1-dodecene over a supported tungstophosphoric acid catalyst

The prepared catalyst of tungstophosphoric acid supported on SiO 2 has shown high activity, good selectivity of producing linear alkylbenzene (LAB) and 2-phenyl isomer and sufficient catalytic stability. Kinetics of benzene alkylation with 1-dodecene over this catalyst was investigated in a fixed-bed reactor after eliminating the influence of internal and external transport. Rate models of formation of different isomers of LAB were derived based on some simplifying assumptions. Kinetic parameters were determined.

12-Tungstophosphoric acid/zirconia--a highly active stable solid acid--comparison with a tungstated zirconia catalyst.

A highly active and stable zirconia supported 12-tungstophosphoric acid catalyst is found to be 2-3 times more active in benzylation and acylation reactions than a tungstated zirconia catalyst.

Tungstophosphoric and tungstosilicic acids on carbon as acidic catalysts

Tungstophosphoric (TPA) and tungstosilicic acid (TSA) catalysts supported on carbon were studied. They were prepared by equilibrium and incipient wetness impregnation techniques. Solutions of TPA and TSA in 50% v/v ethanol–water were used to impregnate carbon at 20°C. The Fourier transform infrared and 31P nuclear magnetic resonance spectroscopies of TPA and TSA supported catalysts dried at 70°C showed that the species present were the undegraded [PW 12O 40] 3− and [SiW 12O 40] 4− anion, respectively. X-ray diffraction of the impregnated solids showed the same diffraction patterns as the supports, possibly owing to a high dispersion of non-crystalline species. The scanning electron microscopy with energy dispersive X-ray analysis of the supported acids showed a uniform distribution of TPA and TSA in the carbon particles with low heteropolyacid content. In the samples with high content or prepared by incipient wetness method small grains of TPA and TSA were found. These grains showed to be nearly inactive for isopropanol dehydration. The specific conversion of the catalysts for this reaction increases regularly with the increase of the adsorbed heteropolyacid content.

Methyl t-butyl ether decomposition in an inert membrane reactor composed of 12-tungstophosphoric acid catalyst and polyphenylene oxide membrane

The methyl t-buyl ether (MTBE) decomposition reaction was carried out in an inert membrane reactor and in a conventional fixed bed reactor to compare the reactor performance of the two reactors. The inert membrane reactor was composed of 12-tungstophosphoric acid (H 3PW 12O 40) catalyst and polyphenylene oxide membrane. The maximum attainable conversion of MTBE in the inert membrane reactor was always greater than that in the fixed bed reactor at temperatures ranging from 80 to 110°C. The selective permeation of methanol through the membrane caused chemical equilibrium shift toward the favourable direction. It was also revealed that the adsorption characteristics of MTBE into the bulk of the heteropoly acid catalyst also played an important role in the increase in MTBE conversion.

Methyl t-butyl ether decomposition in an inert membrane reactor composed of 12-tungstophosphoric acid catalyst and polyphenylene oxide membrane

The methyl t-butyl ether (MTBE) decomposition reaction was carried out in an inert membrane reactor and in a conventional fixed bed reactor to compare the reactor performance of the two reactors. The inert membrane reactor was composed of 12-tungstophosphoric acid (H 3PW 12O 40) catalyst and polyphenylene oxide membrane. The maximum attainable conversion of MTBE in the inert membrane reactor was always greater than that in the fixed bed reactor at temperatures ranging from 80 to 110° C. The selective permeation of methanol through the membrane caused chemical equilibrium shift toward the favourable direction. It was also revealed that the adsorption characteristics of MTBE into the bulk of the heteropoly acid catalyst also played an an important role in the increase in MTBE conversion.

水晶振動子を利用した微小重量測定技術によるヘテロポリ酸触媒内の拡散係数の測定

A piezoelectric quartz crystal microbalance was used to measure the diffusion coefficient of water in 12-tungstophosphoric acid catalyst. The catalyst was coated on the electrode surface of the quartz resonator and the time course of weight change caused by sorption/desorption could be followed in the nanogram range by measuring the frequency change. It was found that the diffusion rate increased with concentration of water absorbed and the response curve was successfully analyzed by assuming a diffusion coefficient as a function of concentration. This concentration dependency indicates that the diffusion process of water in a heteropoly acid is affected by the interaction with active sites. Isotope replacement studies using the same detection method revealed that the concentration dependency of diffusion coefficient disappeared. The obtained values of diffusion coefficients showed the same order as that by the unsteady method and lay in a reasonable order of magnitude.