Electrochemical CaC 2 -Mediated Conversion of Biochar to C 2 H 2 : High Carbon Efficiency and Low Contamination.

The carbon to CaC route is promising to provide a sustainable elementary unit, C H , for the organic synthesis industry, but the traditional thermal reaction process suffers from low carbon efficiency, harmful gas contamination, high temperature operation, and risky CO management. We herein report a high carbon efficiency (ca. 100 %) conversion of biochar to C H through an electrolytic synthesis of solid CaC in molten CaCl /KCl/CaO at 973 K. The main reactions are carbon reduction to CaC at the solid carbon cathode and oxygen evolution at an inert anode. Meanwhile, the electrolysis removes S and P from the solid cathode, avoiding the formation of CaS and Ca P in CaC and consequently eliminating H S and PH contamination in the finally produced C H .