Kinetic model for the ammoxidation of ethanol to acetonitrile

Abstract

A comprehensive kinetic study, based on V-based catalysts (Vanadium Pyro-Phosphate, VPP, VOx/TiO2 and VOx/ZrO2), was modeled to retrieve the surface reaction mechanism and kinetic parameters for the ammoxidation of ethanol to acetonitrile. In all the cases, the catalysts showed a moderate to good acetonitrile selectivity, that in turn resulted correlated primarily to the reaction temperature, while the byproducts distribution was more influenced by the thermodynamic stability of the reacting mixture.A large and comprehensive collection of data on ammoxidation of C2 substrates for acetonitrile production was analysed and 5 groups of experiments on VOx-based catalysts (operating in the temperature range 250–450 °C) were selected. The base reactant was ethanol and ammonia and oxygen were fed in optimal ratios of 1:3–1:4 mol/mol.A kinetic model was then derived applying the Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach to accepted catalytic oxidation mechanisms: for every catalytic material, eight to ten reactions with rates described by the Arrhenius formula were employed. Fixing the reaction orders according to the mechanistic assumption and adjusting only the kinetic and adsorption parameters, the calculated molar fractions of ethanol, ammonia, acetonitrile and ethylene resulted in good agreement with the extensive collection of experimental data available.