Dimethyl Ether Conversion into Light Olefins in a Slurry Reactor: Entrainment and Decomposition of Dispersion Liquid

Abstract

The synthesis of light C₂–C₄ olefins from dimethyl ether (DME) in a three-phase system (slurry reactor) over nanosized MFI-type zeolites suspended in liquids with various chemical compositions (paraffins, hydrocarbon and silicone oils, and polyhydric alcohol esters) was studied. It was found that the target reaction can be accompanied by the catalytic decomposition of a dispersion liquid and its mechanical entrainment, which destabilizes the catalytic process. These negative factors can be minimized with the use of polydimethylsiloxane (Syltherm 800) as a dispersion liquid and MFI zeolite modified with magnesium as a catalyst. The rate of catalytic destruction of this oligomeric molecule in the presence of Mg–MFI was minimal at temperatures of 300°C or lower. The synthesis of olefins from DME at a temperature of 300°C over the Mg–MFI catalyst suspended in Syltherm 800 occurred in a stable way with high performance (70–90% conversion and 46–59% selectivity for the target products). The reaction carried out with the partial reflux of liquid reaction products after the dehydration of condensate excluded the loss of dispersion liquid in the course of the catalytic process due to its mechanical entrainment from the reactor.