Utilization of coal liquefaction solid residue waste as an effective additive for enhanced catalytic performance

Abstract

The co-liquefaction of lignite and heavy residues is regarded as a promising technique for upgrading inferior feedstock, but is limited in the long-term by several engineering challenges that must be overcome before commercialization, in particular to the excessive catalyst consumption and production of solid residue (SR) waste. Herein, the SR waste was transformed into a favorable catalytic additive via a simple activation method that simultaneously decreased the required hydrogenation-catalyst dosage and enabled the resulting hazardous wastes to be utilized. The inorganic minerals contained within coal had a positive influence on the hydro-conversion of the co-liquefaction system and the dispersion of SRs, which motivated us to exploit the enriched minerals in SRs by further activation treatments. The application of activated SRs as cheap additives resulted in an enhanced catalytic performance in co-liquefaction reactions, with a sharp decrease in the required hydrogenation catalyst dosage of nearly 60%. The exposure of iron sulfides in activated SRs following the partial removal of organic carbonaceous matter and silica-alumina minerals provided additional catalytic activity for promoting hydrogenation reactions and aromatic-aliphatic bond cleavages. Furthermore, the modified pore structure of activated SRs with a sharply increased surface area was beneficial for restricting coke deposition on the surface of hydrogenation catalysts and reacted coals, and thus improved the catalytic environment of reaction systems with a relatively economic catalyst dosage.