CO2 char gasification: A systematic review from 2014 to 2020

Abstract

Global efforts to mitigate climate change are based on forecasts of future warmer temperatures on the earth’s surface. Climate warming is caused by the positive radiative imbalances triggered by the accumulated Greenhouse Gases (GHG) emissions. The energy sector accounts for more than 75% of the CO2 emissions. Recycling CO2 to useful molecules is the most desirable path. However, the high thermodynamic stability of CO2 makes this path expensive. The forward Boudouard reaction also called char gasification (C + CO2→ 2CO) represents a possible method of recycling CO2. This reaction is highly endothermic at relatively low temperatures. The char for the reaction is necessary and available from pyrolysis of carbonaceous materials. Pyrolysis of typical carbonaceous material consist of initial fast devolatilization followed by relatively slow char gasification. Therefore, char gasification with CO2 reduction is the rate limiting step. This review is focused on the recent (2014–2020) literature involving acceleration of this important step. Pretreatment of char including the use of microwave heating may be a useful technique. The use, recovery and reuse of catalysts to enhance the rates of the forward Boudouard reaction at manageable temperatures is discussed. In situ imaging and management of the evolution of the char microstructure as a means of maintaining and enhancing the gasification rates has significant potential.