METHANOL-TO-GASOLINE VS. DME-TO-GASOLINE: Ⅱ. PROCESS COMPARISON AND ANALYSIS

摘要

Methanol can be converted into gasoline boiling range hydrocarbons over zeolite ZSM-5 catalyst using the Mobil MTG process. Methanol feed in the MTG process can be derived from coal or natural gas based syngas. The Mobil MTG process involves the conversion steps of syngas-to-methanol and methanol-to-gasoline. Dimethyl Ether (DME), a product of methanol dehydrocondensation, is an intermediate species in the methanol-to-gasoline conversion. Syngas can be directly converted to DME using the Liquid Phase Dimethyl Ether Synthesis (LP-DME) process developed at the University of Akron in conjunction with Electric Power Research Institute. This direct one-step conversion of syngas-to-DME can then be an ideal front end for further conversion to gasoline. This substitution (syngas-to-methanol by syngas-to-DME) is justified because DME results in an identical hydrocarbon distribution over the ZSM-5 catalyst as methanol. The DME-to-Gasoline (DTG) process thus involves the conversion steps of syngas-to-DME and DME-to gasoline. The UA/EPRI DTG process offers advantages over the Mobil MTG process in several areas. These include heat duty and heat of reaction, adiabatic temperature rise, hydrocarbon product yield and selectivity, syngas conversion, and overall process efficiency. The conceptual benefits of the DTG process have been demonstrated experimentally in a fluidized bed reactor system operative at the University of Akron. The salient features of the DTG process and process comparison to the Mobil MTG process are discussed in this paper.