Robert A. Ross

Reaction of carbon monoxide with nitrous oxide on vanadium pentoxide catalysts containing alkali metal sulfate additives

The kinetics of the catalyzed reaction between carbon monoxide and nitrous oxide to yield carbon dioxide and nitrogen from 673 to 773 K has been studied on vanadium pentoxide and on a series of vanadium pentoxide melts containing individually 9.09 mol% of the sulfates of lithium, sodium, potassium, rubidium, and cesium. The additive activity series was V2O5 (pure) < Li2SO4 < Na2SO4 < K2SO4 < Rb2SO4 < Cs2SO4 and exhibited a compensation effect which is associated with changes in surface oxygen mobility which influence catalytic site activity. A Langmuir-Hinshelwood treatment has been used to interpret the kinetic data and a mechanism is proposed which is related to the presence of two types of oxygen species on the catalyst surface, only one of which may be directly involved in the oxidation process of carbon monoxide.

The conversion of cellulose to fuel gases promoted by selected solid additives

Abstract Investigations of the gasification of cellulose fibres have been carried out from 300 to 650°C at atmospheric pressure. Particular emphasis was placed on analysis and yields of hydrogen and methane as a contribution towards the assessment of the process for fuel gas synthesis. To this end, attempts were made to modify reaction pathways by the addition of selected solid additives which might act to improve both quality and quantity of fuel gas yields. Potassium carbonate, zinc (II) chromite and iron (III) oxide were added in various concentrations with emphasis placed on work with the carbonate as both an impregnate and admixture. All additives increased total gas yields over that obtained from pure cellulose with the carbonate most effective and iron (III) oxide least. Thermogravimetric kinetic data, as well as the analytical balances determined for the gaseous products, have been used to develop a fairly general reaction scheme to explain the pyrolysis. Information regarding the nature and surface structure of the cellulose fibres was gathered from scanning electron microscopy with special attention devoted to the surface film formed during gasification in the presence of 5% potassium carbonate.

The effect of the oxygen content in a series of manganese oxide catalysts on their catalytic activity and selectivity in the decomposition of isopropyl alcohol

Abstract The catalytic decomposition of isopropyl alcohol vapor has been investigated from 35 to 280 °C in a flow reactor on manganese oxides of compositions varying from MnO to Mn 2 O 3 . The catalytic reaction products have been identified and the catalyst selectivity in dehydrogenation and dehydration calculated from the values of the reaction rates. The apparent activation energy for dehydration between 156 and 280 °C varies with the oxygen content in the catalyst series based on MnO, from 50 ± 2, stoichiometric MnO, to 56 ± 2 kcal mole −1 , MnO 1.3 . Two distinct apparent activation energy regions occur for the dehydrogenation reaction. Between 150 and 200 °C, the values lie from 5 to 8 kcal mole −1 while above 200 °C these become 26 to 28 ± 1 kcal mole −1 . Stoichiometric Mn 2 O 3 shows no dehydration activity and yields an apparent activation energy in dehydration of 15 ± 1 kcal mole −1 between 35 and 85 °C. In the discussion emphasis is placed on the role of the surface oxygen in the decomposition reactions and an interesting relationship established between the oxygen content of the catalyst and its activity in dehydrogenation.

The effect of heat treatment of chrysotile asbestos on the heats and entropies of adsorption of ammonia below monolayer coverage

Abstract The adsorption of ammonia at low coverages on chrysotile asbestos samples from California and Quebec has been studied using calorimetry at 273 and 298 K. The variation in the heats and entropies of adsorption with surface coverage was determined for surfaces heat treated at 150, 300, 500 and 700 °C. Adsorption capacities for ammonia at 30 kPa range from 2.5 μmol m−2 at 298 K (for Quebec asbestos heat treated at 700 °C) to 6.5 μmol m−2 at 273 K (for Californian material heat treated at 150 °C). Although the heat and entropy data are consistent with a mixed chemical-physical adsorption model, the chemical interactions appear to be weak and reversible. Trace surface impurities may contribute to the chemisorption effects at the lowest coverages.

Dehydration reactions of chrysotile asbestos below 500 °C

Abstract The thermal reactions of chrysotile asbestos samples from Black Lake, Quebec, and Coalinga, California, have been studied at temperatures below 500 °C using thermogravimetric analysis, temperature-programmed desorptio and IR spectroscopy. The desorption spectra show water as the main product with maxima at 260 and 320 °C. Isothermal weight loss data fit kinetic expressions which indicate that the loss of water from the chrysotiles can be described by a transport-controlled reaction based on radial diffusion out of a cylinder. The influence of the brucite impurity in the Quebec material has been interpreted in terms of solid-solid interactions with the chrysotile, and the sharp absorption bands detected in the IR spectra at 3700 and 3650 cm −1 are in good agreement with previous data for OH stretching vibrations.

Effects of water vapour and solid catalysts on the gasification of cellulose at elevated pressures

The gasification of cellulose was examined from 350 to 650°C in helium and helium/water vapour mixtures up to total pressures of 2500 kPa. Particular attention was paid to the effects on the [] molar ratio in the product gases of the selected additives--iron(III)oxide, zinc(II)chromite and potassium carbonate. The results are interpreted in terms of catalytic influences on key steps in the reaction sequence. Thus, the most effective additive in realising the highest gaseous fuel potential was potassium carbonate which may act as a catalyst for the carbon/steam reaction. Although the calorific value of the gases produced was not altered much by pressure, it did slightly affect the distribution of the product gases, probably by influencing the secondary reactions of tars. Scanning electron micrographs of the various solid samples are presented.