SYNTHESIS OF HYDROCARBONS FROM DIMETHYL ETHER: SELECTIVITIES TOWARDS LIGHT HYDROCARBONS

摘要

The depleting supplies of non-renewable petroleum reserves, as well as their escalating costs, have directed a great deal of research toward the synthesis of hydrocarbons from coal. Synthesis of methanol from coal-derived synthesis gas is a well established technology, and methanol has been used as a feedstock for the synthesis of gasoline range hydrocarbons and olefins commercially. However, an efficient hydrocarbon synthesis process has been developed at the University of Akron using dimethyl ether as the starting feedstock. This UA/EPRI's DTH (Dimethyl Ether to Hydrocarbons) process has significant advantages over its counterpart methanol conversion process in the areas of heat duties, hydrocarbon selectivities, product yield, and reactor size. Lower olefins are the intermediate products in the conversion of dimethyl ether to aromatic hydrocarbons. C_2-C_4 olefins and paraffins can be selectively produced by varying the operating parameters of the process, viz., temperature, pressure, DME concentration in the feed, space time, catalyst-to-inert packing ratio, etc. The present work focuses on the effect of key process variables on the dimethyl ether conversion to low molecular weight hydrocarbons in a fixed bed microreactor system over ZSM-5 type zeolite catalyst. Experimental results with respect to gaseous hydrocarbon product yields and selectivities have been examined in this study.