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Issue 7, 2017
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Process exploration and assessment for the production of methanol and dimethyl ether from carbon dioxide and water

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Abstract

A thermodynamic, model-based, study was carried out to assess the relative performance of methanol and dimethyl ether (DME) synthesis systems using CO- and CO2-based syngas feeds. The upstream production of a range of syngas feed compositions was simulated using CO2 and H2O as the sole chemical building blocks, a requirement motivated by the increasing constraints on permissible CO2 emissions and the successful adaptation by some industrial methanol plants to the direct utilisation of CO2. The objective was to establish whether the energy requirements and CO2 emissions associated with upstream conversion of CO2 to CO were justified by increased productivity in the methanol/DME systems. In the first part of the study, the performance of four systems was evaluated and compared in terms of energy efficiency and CO2 conversion: (1) methanol synthesis system, (2) direct DME synthesis system, (3) two-step DME synthesis system with an interposed syngas separation step between the methanol production reactor and methanol dehydration reactor and (4) two-step DME synthesis system with no separation step between the two reactors. Based on equilibrium yields at 250 °C and 50 bar, the direct DME synthesis system was found to exhibit the highest energy conversion efficiencies with both CO2- and CO-based syngas. Although this system demonstrated the lowest CO2 emissions per methanol equivalent product with a CO-based feed, the benefits were offset by emissions associated with the upstream conversion of H2O and CO2 to H2 and CO, evaluated in the second part of the study. It was determined that CO2 could be utilised directly in the direct DME synthesis route, whereas upstream conversion of CO2 to CO was necessary to achieve effective yields in the methanol/two-step DME systems. CO-based syngas production via high temperature co-electrolysis of H2O and CO2, or alternatively high temperature CO2 electrolysis coupled with the water–gas shift process, was identified as the best technology based on energy consumption and CO2 utilisation.

Graphical abstract: Process exploration and assessment for the production of methanol and dimethyl ether from carbon dioxide and water

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Publication details

The article was received on 19 Apr 2017, accepted on 20 Jun 2017 and first published on 08 Aug 2017


Article type: Paper
DOI: 10.1039/C7SE00206H
Citation: Sustainable Energy Fuels, 2017,1, 1541-1556
  • Open access: Creative Commons BY license
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    Process exploration and assessment for the production of methanol and dimethyl ether from carbon dioxide and water

    A. Hankin and N. Shah, Sustainable Energy Fuels, 2017, 1, 1541
    DOI: 10.1039/C7SE00206H

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