Oxidation of ethanol and acetaldehyde over alumina-supported catalysts

Abstract

Williamson, W. B.; Gandhi. H. S. SA€ 1980, 800843. Tittareili, P.; Iannibeiio, A.; Villa, P. L. J. SolM State Chem. 1981, 3 7 , 95.The oxidations of ethanol and acetaldehyde were studied in a laboratory flow reactor over alumina-supported catalysts containing 4 wt % Cu-2 wt % Cr, 0.1 wt % Pt, and 4 wt % Mn, respectively. Most experiments were carried out in feedstreams consisting of 0.1 vol % ethanol or 0.025 vol % acetaldehyde and 1 % O2 in nitrogen at a space velocity of 52 000 (volume feedHvolume catalyst)-' h-' (STP). All three catalysts were found to produce acetaldehyde, carbon monoxide, and carbon dioxide as the major carbon-contalnlng products of ethanol oxidation. CO, was the principal carbon-containing product in the oxidation of acetaldehyde. The steady-state yield of acetaldehyde obtained in the oxidation of ethanol was found to go through a maximum as the temperature was raised over each catalyst. The data suggest that some of the ethanol is oxidized consecutively to acetaldehyde and then to COP over these catalysts. In addition, over Pt, there is also evidence for the direct oxidation of ethanol to co,.The kinetics of the copper-catalyzed amination of long-chain aliphatic alcohols (octanol and decanol) by monomethylamine and dimethylamine have been investigated in both the gas and liquid phases at temperatures between 440 and 540 K. The Individual reactions leadlng to the production of stable intermediates and products are identified. The rate of dehydrogenation of the alcohol determines the overall rate of alcohol conversion to all products. The rate i s first order in alcohol in both the gas and liquid phases and inhibited by alcohol, water, and the reactant amine in the gas phase only. The selectivity is determined primarily by the rate of hydrogenation of an adsorbed intermediate and the rate of disproportionation of reactant and product amines. The selectivity of the amination reaction to the desired tertlary amine increases with increasing hydrogen pressure, and first increases and then decreases with increasing conversion of alcohol.

Impacto dos catalisadores automotivos no controle da qualidade do ar

“…O hidrogênio formado reduz os óxidos de nitrogênio, de acordo com a equação (40). Além dessas vantagens, o óxido de cério estabiliza a dispersão metálica 84 .…”

“…A exposição térmi-ca do catalisador de três vias pode levar à sinterização dos metais nobres e à diminuição da área superficial específica do suporte 9 . No caso de veículos movidos a álcool ou a álcool-gasolina, existe o problema adicional do controle das emissões de álcoois, aldeídos e áci-dos carboxílicos 40 . Assim sendo, esta área recebeu, nos últimos trinta anos, bastante atenção por parte da comunidade científica e continua aberta à investigação de novos materiais que venham atender às condições de redução dos metais nobres (menos disponíveis), redução na deterioração do catalisador (muito sensível a venenos, como compostos de enxofre, presentes na maioria dos combustíveis) e alta eficiência com misturas gasolina/etanol e com os aditivos presentes.…”

“…Outros estudos, conduzidos com catalisadores à base de cromo e cobre, platina e manganês suportados em alumina, mostraram que os principais produtos foram monóxido e dióxido de carbono (principalmente) e acetaldeído e, o catalisador contendo platina foi o mais ativo 40 . Este comportamento foi explicado admitindo-se que, no caso, dos catalisadores menos ativos, as espécies intermediárias eram mais estáveis que nos sistemas contendo platina.…”

On the promoting effect of the addition of CexZr1−xO2 to palladium based alumina catalysts for methanol deep oxidation

“…or metals (Pt, Pd, Rh, Ag, etc.) supported on g-alumina in deep oxidation of methanol [4][5][6][7]. Noble-metal-based catalysts are generally preferred for the deep methanol oxidation because of their superior specific activity and higher selectivity.…”

Reaction Mechanisms of Ethanol Deep Oxidation Over Platinum Catalyst

“…Irrespective of the type of catalyst, a significant amount of ethanal in the reaction products was always observed in a wide range of operative conditions, even if platinum based catalysts showed greater selectivity toward CO 2 (McCabe and Mitchell, 1983;Yu Yao, 1984;Gonzalez and Nagai, 1985).…”