Synergistic use of carbon dioxide in catalytic pyrolysis of chlorella vulgaris over Ni and Co catalysts

Abstract

Recovering energy from microalgal biomass via pyrolysis offers an active precautious measure for global warming due to its superior carbon fixation capability. Hence, catalytic pyrolysis of chlorella vulgaris (C. vulgaris) over Co and Ni catalysts was done to recover energy as a form of syngas. To offer a more sustainable measure for syngas formation, possible use of CO2 as a reaction feedstock was examined. As such, functional effectiveness of CO2 on C. vulgaris pyrolysis was mainly scrutinized. From non-catalytic pyrolysis of C. vulgaris, CO2 turned into CO by its reduction and simultaneous oxidation of volatile pyrolysates produced from C. vulgaris pyrolysis. Such the effectiveness of CO2 also resulted in the more gaseous pyrogenic products (syngas and C1-2 hydrocarbons), but its effectiveness was restrictively initiated at ≥ 510 °C due to retarded reaction kinetics. To accelerate the reaction kinetics governing the formation of gaseous pyrogenic products, earth abundant and non-toxic metal Co and Ni catalysts were adopted for catalytic pyrolysis. The significant improvement of syngas production was achieved from Ni (5.6 times) and Co (2.6 times) catalysts, respectively, in reference to non-catalytic pyrolysis under the CO2 environment.