N.W. Cant

Hydrogen sulphide emission control by combined adsorption and catalytic combustion

Abstract The removal of low concentrations of hydrogen sulfide by adsorption and catalytic combustion has been studied. Concentration of hydrogen sulfide by adsorption from waste-gas streams is best effected by molecular sieve 13X, if the stream is dry, and by activated carbon, if the gas stream is moist. Low-temperature catalytic oxidation of hydrogen sulphide in moist gas streams can be effected over activated carbon. The reaction appears to involve ionized hydrogen sulfide, dissolved in water condensed in the pores of the carbon. At high temperatures, both supported platinum and palladium catalysts are found to be oxidation catalysts. Palladium is the best catalyst for methane oxidation but is partially deactivated in the presence of sulfur-containing gases. In contrast, platinum was more active for the same reaction in the presence of sulfur-containing gases. Both metals were found to promote the oxidation of hydrogen sulfide above ca. 150°C. The power rate laws describing the kinetics of reaction were determined.

Hydrogenolysis of alkyl formates over a copper chromite catalyst

Abstract Methanol may be produced by carbonylating alcohols in the presence of alkali metal to produce alkyl formates which are then hydrogenated to produce the original alcohol and methanol. As part of a study of methanol production by this route, the present investigation has been concerned with the hydrogenolysis of alkyl formates over copper chromite catalysts. Hydrogenolysis of a series of alkyl formates has been found to proceed at moderate temperatures and pressures but the methanol produced reacts with the original alkyl formate to produce methyl formate and the original alcohol. The latter transesterification reaction exhibits a rapid equilibrium, the position of which is little influenced by temperature. Preliminary studies of the effect of formate structure on hydrogenolysis and transesterification reactions have been carried out.

Characterization of copper chromite catalysts for methanol dehydrogenation

Abstract Copper chromite catalysts have been characterised by total and metal surface areas. X-ray powder diffraction, thermal gravimetric analysis and selective extraction of copper oxide in order to investigate the nature of the active catalyst for methanol dehydrogenation. After reduction in hydrogen at atmospheric pressure, the catalyst surface has been shown to consist essentially of copper metal crystallites supported on cuprous chromite. The mechanism of catalyst reduction has been identified.

Liquid phase hydrogenolysis of methyl formate in a semi batch reactor

The liquid phase hydrogenolysis of methyl formate has been studied in a three phase slurry reactor using a Girdler G-89 copper chromite catalyst. Measurements at 446 K show a very high selectivity to methanol. The reaction is first order in methyl formate, first order in hydrogen for pressures of 1.7 to 4.5 MPa and has an apparent activation energy of 62 kJ mol−1. Unlike the corresponding vapour phase process at atmospheric pressure, the liquid phase reaction shows no evidence of catalyst deactivation at 450 K and to conversions beyond 70%. However, inhibition, which is at least partially reversible, becomes apparent at 473 K when carbon monoxide is detectable as a by-product. Inhibition can be observed at lower temperatures if carbon monoxide is deliberately introduced at pressures above 0.1 MPa. The apparent reaction order in carbon monoxide is then −0.32.

Investigation of copper on silica catalysts prepared by an ion exchange method

Abstract The preparation of copper on silica catalysts by the ion exchange method has been found to yield ion-exchanged copper and small copper crystallites (diameter 1.4 – 2 nm). The importance of the copper crystallites depend mainly on the concentration and amount of impregnating solution trapped in the filter cake and the acidity and amount of the wash solution. Catalytic activity for the hydrolysis of acrylonitrile is found to depend on copper surface area. Fast deactivation during the early stages of reaction may depend on copper crystallite size. Slower deactivation as a result of copper oxidation is possible unless the solutions are deoxygenated.

Supported Rh Catalysts for the Indirect Partial Oxidation of Isooctane

The production of hydrogen from isooctane over three rhodium-based catalysts has been examined. The reaction entailed total oxidation of a proportion of the fuel followed by reforming of isooctane to produce hydrogen. Rhodium (1% wt) was impregnated on three different supports: alumina, ceria-alumina, and ceria-zirconia. No differences in catalytic activity were observed, but reaction yield changed with the support. Ceria-zirconia was found to be the preferred support since methanation did not occur over the catalyst.

Benzene Formation During the Oxidation of Cyclohexene in the Presence and Absence of Thiophene over a Supported Palladium Catalyst

The catalytic oxidations of cyclohexene and thiophene, singly and together, have been studied over a Pd/CeO2/Al2O3 monolith catalyst. On a freshly reduced sample, the oxidation of cyclohexene on its own commences below 100°C with benzene as the major product over a considerable temperature range, even when O2 is in large excess. Benzene is still produced when cyclohexene and thiophene are co-oxidised and the reaction exhibits oscillations, associated with accumulation and removal of sulfur, at high conversions. The oxidation of thiophene is self-poisoned to some degree and sulfur accumulated during it considerably reduces the activity of the catalyst for the subsequent oxidation of cyclohexene. However, the maximum yield of benzene remains high.

Low emission conversion of natural gas to hydrogen

The decomposition of methane to hydrogen and carbonaceous residues under conditions suitable for solar heating (ca. 750°C) has been studied. Although nickel and iron-containing catalysts provide decomposition at appropriate temperatures, deposition of carbon leads to deactivation. Regeneration is found to be slow. However, scrap material from a steel mill, containing iron as a major catalytic component, was found to give high yields of hydrogen. Carbon was deposited on the scrap material and the solid product is suitable for recirculation to a steel mill.