Valorization of Pyrolyzed Biomass Residues for the Transformation of Waste Cooking Oil into Green Diesel

This study aims to utilize biochars derived from residual biomass as supports for Ni-based catalysts. For the preparation of the biochars, byproducts of agro-industrial activities were used, such as espresso coffee residue (C) and rice husks (R). Sufficient quantities of the respective biochars (BioC and BioR) were prepared via pyrolysis at 850 & DEG;C of the aforementioned materials under limited oxygen conditions. The biochars were further treated with hot water (WBioC, WBioR), H3PO4 or H2SO4 solution (BioC-P, BioC-S, BioR-P, BioR-S), and NaOH solution (BioC-A and BioR-A), and the obtained solids were characterized using various physicochemical techniques. The biochars produced were microporous with high surface areas (367-938 m(2)g(-1)). The most promising biochars were selected as supports for the preparation of nickel catalysts (10 wt.% Ni) with high Ni dispersion (mean crystal size: 8.2-9.8 nm) and suitable acidity. The catalysts were evaluated in a high-pressure semi-batch reactor for the transformation of waste cooking oil (WCO) into green diesel. The 10Ni_BioC-P catalyst exhibited the best performance, resulting in a complete conversion of the WCO but a low hydrocarbon yield (7.5%). Yield improvement was achieved by promoting this catalyst with molybdenum. The addition of Mo increased the hydrocarbon yield by almost three times (19.5%).

Automated summary

This study aims to use biochars derived from residual biomass as supports for Ni-based catalysts. The biochars were prepared from espresso coffee residue (C) and rice husks (R) via pyrolysis, and were further treated with hot water, H3PO4 or H2SO4 solution, and NaOH solution. The obtained biochars had high surface areas and microporous structure. The most promising biochars were used as supports for Ni catalysts, and the addition of Mo significantly increased the hydrocarbon yield.