Estimation of kinetic parameters for acetic acid conversion to ethanol

Abstract

In view of being a significant contributor to Greenhouse gases, India has decided to use ethanol as a substitute to conventional petroleum fuel, however the current feedstock molasses standalone would not be able to meet the mandated requirement. Catalytic hydrogenation of acetic acid to ethanol is a promising route, superior to homogeneous and heterogeneous catalytic processes. The process of ethanol production via catalytic hydrogenation is well suited for countries like India, with limitation in farm land and a demanding target to fulfill the need of fuel. Typicallynoblemetalbasedcatalystsareusedfortheprocess,ofwhichbimetalliccatalysts incorporated with Pt are the most effective. In the present work, SiO2 supported Co and Co-Pt catalysts have been prepared by impregnation method and their characterizations have been carried out by scanning electron microscopy, BET surface area, X-ray diffraction,thermogravimetricanalysisandtemperatureprogrammedreduction. Theactivity studies of these catalysts have been carried out in the temperature range of 240-320◦C, at pressure 20 bar, at fixed flow rates of acetic acid and hydrogen, in a fixed bed catalytic reactor. Activity of SiO2 supported 2.1%Pt-1.8%Sn catalyst have also been studied in the temperature range of 270-310◦C, varying pressure in the range of 1-20 bar, WHSV in the range of 2-4 and molar ratio of H2 to acetic acid in the range of 3-7. Reaction models that correlate these data involving Langmuir-Hinshelwood type catalytic sequence have been derived. Several rate expressions have been derived by assuming different elementary reactions as the rate determining steps. Once the expressions developed, experimental data obtained has been used to fit these expressions. The one having the closest fit has been consideredastherateexpressionforthereaction. DetailedMATLABbasedcodehasbeen developed to estimate the rate parameters. Finally, an attempt has been made to develop the fixed bed reactor model using the developed kinetics.