Electrochemical production of syngas from CO2 at pressures up to 30 bar in electrolytes containing ionic liquid

Sofia Messias, Miguel M. Sousa, Manuel Nunes Da Ponte, Carmen M. Rangel, Tiago Pardal, Ana S. Reis MacHado

Research output: Contribution to journalArticle

Abstract

Electrochemical CO2 reduction in a reactor that can operate up to 100 bar and 80 °C, with a configuration similar to that of an alkaline electrolyser, for hydrogen production suitable to be used industrially is reported for the first time. The effect of pressure on the co-electrolysis of CO2 and water was studied. The successful scale-up from a previously reported batch process to electrodes of ca. 30 cm2 geometrical area (30-fold factor) that combines the use of pressure and an ionic liquid-based electrolyte is presented. Also for the first time, the potential of the system under study to achieve high conversions of CO2 to avoid a purification step of syngas from unreacted CO2 is shown. An inexpensive commercial foil of the common metal zinc was employed. A semi-continuous operation yielded syngas productivities in the range of 0.02-0.04 mmol cm-2 h-1 at ca. -1.2 V vs. QRE Ag/Ag+. When an electrolyte consisting of 90 wt% H2O and 10 wt% 1-ethyl-3-methylimidazolium trifluoromethanesulfonate was used, selectivities for CO in the range of 62% to 72% were obtained at 10 bar pressure, whereas selectivities of 82% were obtained at 30 bar pressure. H2/CO ratios in the range of 1/1 to 4/1 at 10 bar pressure suitable for the synthesis of a variety of fuels, such as hydrocarbons, methanol, methane and chemical building blocks, were observed. An energy efficiency of 44.6% was calculated for a H2/CO ratio of 2.2 suitable for the synthesis of methanol.

Original languageEnglish
Pages (from-to)1982-1990
Number of pages9
JournalReaction Chemistry and Engineering
Volume4
Issue number11
DOIs
Publication statusPublished - 1 Nov 2019

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