Deep Oxidation of Benzene on Pt/V2O5–TiO2 Catalysts

The combustion of benzene was studied on Pt supported on V₂O₅–TiO₂ samples containing different amounts of V₂O₅. Vanadium was highly dispersed as V⁴⁺ for low V₂O₅ loadings, forming a vanadia monolayer on titanium dioxide for a V₂O₅ concentration of about 5%wt. V₂O₅–TiO₂ samples were more active than V₂O₅ and TiO₂ single oxides, and the activity increased with the vanadia content. The platinum dispersion in Pt/V₂O₅–TiO₂ catalysts increased with the V₂O₅ loading but the activity for the deep oxidation of benzene exhibited an opposite trend. Benzene combustion was a structure sensitivity reaction promoted on larger metallic Pt crystallites which were preferentially formed when the V₂O₅ content in the sample was decreased.     

Efficient hydrogen supply through catalytic dehydrogenation of methylcyclohexane over Pt/metal oxide catalysts

This paper describes the results of experiments on dehydrogenation of methylcyclohexane over Pt supported on metal oxides (Pt/MO) and Pt supported on perovskite (Pt/Per) catalysts. The reaction is being considered as a means for delivery of hydrogen to fueling stations in the form of more easily transportable methylcyclohexane. Among Pt/MO catalysts, the best activity as determined by the hydrogen evolution rate was observed over Pt/La₂O₃ catalyst at 21.1 mmol/g_met/min. Perovskite-supported catalysts exhibited relatively higher activity and selectivity, with Pt/La_0.7Y_0.3NiO₃ giving the best performance. This Pt/Per catalyst had an activity of ca 45 mmol/g_met/min with nearly 100% selectivity towards dehydrogenation. The catalysts were characterized using XRD, CO-chemisorption and SEM-EDXA techniques. The present study reports catalysts that minimize the use of Pt and explores tailoring the properties of the perovskite structure.     

Synthesis and high performance of ceria supported nickel catalysts for hydrodechlorination reaction

Catalysts containing 10 wt% Ni supported on CeO₂ were prepared by two ways, namely, co-precipitation method using nickel nitrate precursor and impregnation method using nickel nitrate and nickel acetylacetonate as two separate precursors. The catalysts were characterized by pulse chemisorption of H₂, X-ray diffraction, and temperature programmed reduction (TPR) techniques and evaluated for the gas phase hydrodechlorination (HDC) of chlorobenzene to benzene in a fixed-bed down-flow glass reactor at 573 K under normal atmospheric pressure. The hydrogen uptake values were used to determine the catalyst properties of Ni/CeO₂ like dispersion, metal area, and particle size. Among the two preparatory routes, co-precipitation method gave better catalytic performance in terms of hydrogenation activity, benzene selectivity, and coking resistivity than impregnated Ni/CeO₂ catalysts. This may be attributed to high dispersion of smaller NiO crystallites and the appearance of the second reduction peak at a higher temperature (578 K) in TPR profile with co-precipitated Ni/CeO₂ catalyst. This indicates that a strong interaction may take place between the NiO crystallites and CeO₂ on the surface of co-precipitated Ni/CeO₂ catalyst. Contrary to general expectation that the large Ni particles are preferable for HDC reaction, it is observed that smaller metal particles with high dispersion, as in the case of co-precipitated Ni/CeO₂ catalyst, promotes better catalyst with longer life.     

Performance of a Multiprocessor-Based Parallel Stack Algorithm Speech Encoder

A parallel processor version of the stack algorithm is proposed that searches the code tree in parallel. The parallel stack algorithm is then implemented and tested using a loop architecture with four Intel 8086 microprocessors. The two versions of the stack algorithm, the uniprocessor and multiprocessor implementations, are then used to encode a voiced speech sound. The multiprocessor version simultaneously improves two conflicting performance measures, namely, the signal-to-noise ratio and node computation per processor, and may indeed lead to a real-time implementation of the stack algorithm.     

Eco-Friendly Vapor Phase Aerobic Selective Oxidation of Styrene to Benzaldehyde Over SBA-15 Supported Vanadium Modified Heteropolyacid Catalyst

Catalysis Letters - Selective oxidation of styrene to benzaldehyde was investigated over H4PMo11VO40 (HPMoV) supported on SBA-15 support in eco-friendly aerobic gas phase condition. A series...     

Catalytic dehydration of glycerol to acrolein over mesoporous MCM-41 supported heteropolyacid catalysts

Journal of Porous Materials - A series of vanadium substituted phosphomolybdic acid (VPMA) supported on mesoporous MCM-41 catalysts with varying VPMA content ranging from 10 to 50 wt% were...     

Effect of V2O5 Loading on Propane Combustion over Pt/V2O5–Al2O3 Catalysts

Propane combustion was studied on Pt(0.4%)/V₂O₅–Al₂O₃ catalysts containing up to 20% V₂O₅. The density, strength and nature of surface acid sites were determined by TPD of NH₃ and FTIR spectra of adsorbed pyridine. The sample acidity increased with the vanadium content, essentially because the addition of vanadium oxide generated Brønsted acid sites. The Pt dispersion as determined by H₂ chemisorption increased with increasing V₂O₅ loading. The sample activity for propane combustion was evaluated through both conversion versus temperature (light-off curves) and kinetically-controlled conversion versus time catalytic tests. The propane combustion turnover rate on Pt/V₂O₅–Al₂O₃ increased with the amount of vanadium, probably because the intrinsic Pt oxidation activity increases with the sample acidity.