Kinetic study of ethanol dehydrogenation to ethyl acetate promoted by a copper/copper-chromite based catalyst

A kinetic study of the ethanol dehydrogenation to ethyl acetate on a copper/copper-chromite catalyst has been performed. The used catalyst, in cylindrical pellets, contained also alumina as a support and barium chromate as a promoter. Support and promoter have the effect of increasing the activity, the selectivity and the stability of the catalyst, as shown in a previous work. The kinetic runs were carried out in a packed bed tubular reactor, alternatively filled with 2 or 50 g of catalyst, approximately isothermal, by feeding pure ethanol together with a mixture of nitrogen and hydrogen as carrier gas. Kinetic runs have been made by changing the temperature, in the range of 200-260 degrees C, the pressure between 10 and 30 bar and the space time from 1 to 100 g h mol(-1). We have verified, at first, that inter-phase and intra-phase mass transfer limitations were negligible in the adopted conditions. Then, a Langmuir-Hinshelwood-Hougen-Watson kinetic model has been used for interpreting all the experimental data collected. This model corresponds to a mechanism in which the first step is the dissociative adsorption of ethanol on the surface, giving an adsorbed ethoxy group. Then, two other consecutive steps give place to respectively acetaldehyde as intermediate and ethyl acetate. This kinetic model allows a satisfactory fitting of all the performed experimental runs with a standard error below 15% for the runs performed with 2 g of catalyst and less than 12% for the runs made with 50 g of catalyst. (C) 2012 Elsevier B. V. All rights reserved.