Farhang Abdollahi, Handan Tezel, and Stephen Aplin
Alternative energy, CO2 conversion, synthetic fuel, reverse water gas shift reaction
While most carbon capture and sequestration (CCS) proposals envision permanent underground storage for captured CO2, increasing attention is being paid to ways in which captured CO2 could be utilized as a raw material for the manufacture of subsequent chemicals. One such proposal is reacting CO2 with hydrogen (H2) to produce carbon monoxide (CO). This is the reverse water gas shift (RWGS) reaction, which produces CO and water. While CO2 is highly stable chemically, CO is highly reactive. This makes it a valuable raw material for manufacture of other chemicals, including liquid hydrocarbon fuels such as gasoline and diesel; this could be achieved via the well-known Fischer–Tropsch synthesis which uses synthesis gas, a mixture of H2 and CO, as its raw material. In this study, the RWGS reaction has been investigated via computer simulation in order to determine the best way to maximize the overall conversion of CO2 to CO, i.e., to force the RWGS reaction towards maximum CO production. The endothermic RWGS reaction generally requires very high temperatures (>700◦C) for high conversions. Such temperatures present challenges related to further carbon emission (depending on the source of heat energy) and materials stability. However, an integrated separation and recycling system, possibly incorporating a pressure swing adsorption (PSA) and/or membrane process, could separate and recycle unreacted CO2 and H2 gases back to the reactor inlet resulting in higher overall CO2 conversion compared with other methods suggested in the literature.
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