Catalytic partial oxidation of ethane to acetic acid over Mo 1V 0.25Nb 0.12Pd 0.0005O x: reactor operation

Abstract

The operation of a fixed-bed and fluidized-bed reactor for the partial oxidation of ethane to acetic acid was simulated. For the fixed-bed reactor a two-dimensional homogenous model and for fluidized-bed reactor the bubble assemblage model was applied. A kinetic model was used for reactor simulation, which describes the primary oxidative dehydrogenation of ethane to ethylene, the formation of acetic acid via ethylene, as an intermediate as well as a direct formation of acetic acid from ethane. Carbon dioxide formation results from combustion of ethane, ethylene and acetic acid. Furthermore, the influence of water on the reaction pathway was taken into account in the kinetic model. For the fixed-bed reactor, the influence of inlet temperature was investigated in a temperature range from 500 to 525 K and at a total pressure of 16 bar . The range of temperature where the danger of run-away occurs depends on gas velocities and reactor diameters. Accordingly, for a reactor diameter of 0.025 m and a gas velocity of u STP =0.0045 m s −1 runaway must be expected above a temperature of the inlet feed of 520 K . In a fluidized-bed reactor, significant lower selectivities and space-time yields of acetic acid are achieved compared to the fixed-bed due to the slow mass transfer of oxygen between bubble and emulsion phase. However, yield and selectivity of acetic acid can be increased by applying small sized catalyst particles.