Electrochemically assisted pyrolysis of rice straw in molten carbonates

Abstract

Abstract The pyrolysis of rice straw as a feedstock in molten carbonates pyrolysis (MCP) and electrochemically assisted molten carbonates pyrolysis (EMCP) systems was investigated in this study. Molten carbonates (MC) were utilized as both the heat transfer medium and the electrolyte in EMCP. The results suggested that EMCP helped to reduce the formation of tar and water, while promoting the formation of gases, especially CO2. The optimum reaction conditions were 600 mA/cm2 of current density in a particle size of 3 mm at 550 °C, with the maximum H2 and CH4 yields of 0.26 mol/100 g and 0.17 mol/100 g, and the yield of hydrocarbons peaked at 5.0%. EMCP system reinforced the reaction by accelerating the reaction rate rather than reducing the activation energy. The electrochemical process facilitated the conversion of the hydroxyl groups and a fraction of the carbonyl groups in the biomass to carboxyl groups, which then underwent decarboxylation to release CO2 in the MC medium. Because oxygen atoms were removed from the system as CO2, the water formation decreased. The EMCP system showed benefits in the synthesis of hydrogen and hydrocarbons, and opened a novel pathway for the deoxygenation of biomass in pyrolysis.