Catalytic Graphitization to Valorize Char By-products from Pinewood Liquefaction

Abstract Production of sustainable aviation fuels from abundant lignocellulosic biomass is facing technoeconomic viability challenges in addition to the valorization of by-products produced from their conversion techniques. Near-critical Integrated Liquefaction-Extraction is an emerging technique focused on obtaining hydrotreating compatible biocrude from lignocellulosic biomass. But, similar to other thermochemical routes, this process viability needs to be significantly improved by valorizing the char by-products produced. Some 15-35 wt.% of the lignocellulosic biomass is typically leftover as the biochar from these biofuel production routes, so converting them into valuable and in-demand materials can significantly improve the biocarbon utilization, and overall process economics. In this direction, converting this biochar into graphitic carbon is very promising as the need for low carbon-footprint sustainable synthetic graphite is imminent with the growing applications in electrochemical metallurgy, energy storage, lubrication, nuclear reactor moderation, refractory and other emerging needs especially for renewable energy infrastructure development. Presently, synthetic graphite is prepared from fossil oil, using a carbon intensive process, and the purification needs require strong and corrosive acids. Catalytic graphitization of the liquefaction char provided us with promising extent of graphitization. Catalytic graphitization was investigated here using Ni loading as the catalyst followed by thermal treatment, and acid washing for Ni recovery. Different Ni loadings were investigated to understand its impact on the process performance. X-ray diffraction (XRD) and Raman spectroscopy were utilized for characterization of the graphitic biocarbon produced while thermogravimetric analysis provided information on thermal stability and inorganic impurities.