Analysis of Fundamental Reaction Rates in the Methanol-to-Olefins Process on ZSM-5 as a Basis for Reactor Design and Operation

Abstract

The paper reports on work aiming at collecting more insight into the methanol-to-olefins process and its product distribution and, more generally, into the behavior of carbenium ion elementary steps of methylation, olgomerization, and β scission on zeolite catalysts. The single-event concept for the rate coefficient, derived from transition-state theory and statistical thermodynamics, and the Evans−Polanyi relationship for the activation energy drastically reduced the number of parameters to be derived from the experimental data from 726 to 33. The number of single events and the heats of formation required for this approach were calculated from the reacting structures and ab initio molecular orbital calculations. The kinetic parameters were inserted into a reactor model to generate sets of rate and yield profiles in an isothermal fixed-bed reactor in the range of 380−480 °C. Finally, for commercial applications, a multibed adiabatic reactor concept was explored.