Separation process for one-step production of dimethyl ether from synthesis gas

• Main Authors: Peng, Xiang-Dong, Diamond, Barry W, Tsao, Tsun-Chiu Robert, Bhatt, Bharat Lajjaram
• Format: Patent
• Language: English
• Published: 01.10.2002

The present invention relates to a separation process for the one-step production of dimethyl ether (DME) from synthesis gas (syngas), a mixture of hydrogen (H ) and carbon monoxide (CO). In the one-step syngas-to-DME process, syngas is converted in a single reactor (DME reactor) to methanol and DME over a catalyst system with methanol synthesis (2H +CO→CH OH), methanol dehydration (2CH OH→DME+H O), and water gas shift (H O+CO→CO +H ) activities. Due to a chemical synergy among these three reactions, the single pass syngas conversion in the DME reactor, or productivity, is significantly greater than that in a methanol synthesis reactor, wherein the methanol synthesis reaction primarily takes place. Since reactors for syngas conversion are expensive equipment for high-pressure operation at elevated temperatures, greater conversion or productivity means smaller DME reactors, associated equipment, and operation. This can reduce the cost in the syngas conversion part of the process, and possibly lead to a more economic process for DME production than the traditional two-step process, namely, methanol synthesis followed by methanol dehydration in two separate reactors. An improvement to the process for separating dimethyl ether (DME) from byproducts in a one-step catalytic conversion of synthesis gas (syngas), the improvement comprising using a scrubbing solvent comprising a mixture of dimethyl ether and methanol for the separation of dimethyl ether and carbon dioxide from the unconverted synthesis gas in a scrubbing column. Additional improvements include recycling of the scrubbing solution, multi-step processing of the liquid effluent from the scrubber, and methods of processing the methanol-water effluent of the flash column that is interposed between the DME reactor and the scrubber.