Electrically Conducting Carbon Microparticles by Direct Carbonization of Spent Wood Pulping Liquor

Lignin is produced abundantly in wood pulping. Because it is currently mainly used for the generation of process energy and electrical energy by combustion, its isolation from processing liquor and subsequent purification for potential higher value uses is challenging. Therefore, the present study evaluates the feasibility of direct carbonization of spray-dried processing liquor from two relevant industrial pulping processes with the aim of obtaining electrically conducting carbon. Analysis of the carbonization process reveals significant differences in the thermal stability of spray-dried liquor from a sulfite pulping process compared to kraft liquor. As a result, kraft-derived carbon shows highly ordered graphitic structure and good electrical conductivity comparable to carbon black, whereas sulfite liquor derived carbon only shows modest conductivity.