R.D. Srivastava

Kinetics and mechanism of deactivation of PdAl2O3 catalyst in the gaseous phase decarbonylation of furfural

The kinetics of decarbonylation of furfural to furan as well as the kinetics and mechanism of deactivation by coking of PdAl2O3 catalyst have been examined. A statistically best-rate expression for the main reaction, developed on the basis of the surface reaction on two active sites, was determined from the experimental data. Deactivation occurred in parallel with the main reaction. The deactivation kinetic equation was governed by the reaction of two adjacent adsorbed furfural molecules resulting in the coke precursor.

Kinetics of vapor phase oxidation of methyl alcohol over supported V2O5K2SO4 catalyst

The kinetics of oxidation of methanol to formaldehyde over vanadium pentoxide-potassium sulfate catalyst supported on silica gel was investigated between 330 and 410 °C at atmospheric pressure. The catalyst, 10% V2O5, 20% K2SO4, and 70% silica gel, was found to be optimum in terms of conversion and selectivity to formaldehyde. The following rate expression, deduced assuming a steady state involving simultaneous reduction of catalyst by methanol and oxidation f the catalyst to the original state by gaseous oxygen, represents the experimental data satisfactorily : r = k1pM[1 + (k1pM2k2po20.5] The activation energies of the two steps were 14.7 and 17.5 kcal/mole, respectively.

Kinetics of oxidation of tetralin over supported NiO catalyst

The liquid-phase oxidation of tetralin in chlorobenzene at 45/sup 0/-85/sup 0/C over alumina-supported nickel oxide proceeded at a maximum rate on a 20% NiO catalyst that was calcined at 450/sup 0/C for 12 hr. The tetralin oxidation on this catalyst was 0.5 order in catalyst-tetralin ratio and first order in tetralin concentration and had an apparent activation energy of 11.8 kcal/mole. With increasing catalyst-tetralin ratio, the tetralin hydroperoxide concentration in the products decreased and the tetralyl alcohol and tetralone concentrations increased. The results were consistent with a reaction mechanism similar to the one proposed for cumene oxidation which implied that the catalytic activity of supported NiO is mainly due to its ability to decompose the hydroperoxide in the chain initiating radicals.

V2O5K2SO4-silica system: The structure and activity of silica-supported V2O5K2SO4 catalysts

Abstract Silica-supported V 2 O 5 K 2 SO 4 catalysts containing up to 70 wt% of the total active phase, calcined at 550 °C for 6 hr, have been studied by means of electron microscopy, DTA, TGA, X-ray, and BET studies. The correlation of measured physicochemical properties with the catalytic activity for methanol oxidation was investigated. X-Ray and electron microscope observations have indicated the presence of V 2 O 5 K 2 SO 4 in all the catalyst samples without any interaction between them. The results of the thermal analyses showed that K 2 SO 4 was not dissolved in the V 2 O 5 matrix. Electron microscopy indicated the presence of needle-type V 2 O 5 crystals. These needle structures, which depend on K 2 SO 4 concentration, appear to be more active for the methanol oxidation. The values of average pore radius and surface area simultaneously play an important role in the activity of the catalyst. Electron microscopy and X-ray analysis of a spent catalyst showed that the fundamental components of the fresh catalyst were completely retained. However, the needle structures and other large particles partially disintegrated during catalysis over extended runs.