Demethylation-modified sodium lignosulfonate-templated Ru-Co nanoparticles for mild hydrogenation of lignin-derived diphenylmethanes to cyclic hydrocarbons

An aqueous Ru-Co bimetallic catalyst system was successfully constructed. • The activity of Ru-Co catalyst was enhanced via sodium lignosulfonate demethylation. • Dicyclohexylmethane and perhydrofluorene were produced under mild conditions. An aqueous bimetallic nanoparticle catalyst system (Ru-Co@DMSLS aq ) was successfully constructed by first modifying sodium lignosulfonate (SLS) via a Na 2 SO 3 -mediated, NaOH-catalyzed method to obtain demethylated SLS (DMSLS). 1 H NMR analysis revealed that the increased hydroxyl content in optimized DMSLS was the key factor enhancing the reduction ability toward metal ions in aqueous solution, thereby yielding Ru and Co nanoparticles with improved catalytic activity. With a precursor ratio of n (Ru 3 O(OAc) 7 )/ n (Co(OAc) 2 ) = 3/2, the resulting Ru-Co@DMSLS aq system featured uniformly dispersed nanoparticles and exhibited outstanding catalytic performance in the hydrogenation of diphenylmethane (DPM) and the hydrodeoxygenation (HDO) of o -hydroxydiphenylmethane ( o -HDPM). Under the conditions of 80 °C, 1.5 MPa H 2 , and 4 h, nearly complete conversion of DPM was achieved with 99.2% selectivity toward dicyclohexylmethane (DCHM). Additionally, a yield of 98.5% for perhydrofluorene (PHF) was attained at 90 °C, 1.5 MPa H 2 , and 4 h in the HDO of o -HDPM. The aqueous bimetallic system enabled favorable product-catalyst self-separation and could be reused five times. This work presents a feasible strategy for valorizing lignin derivatives into low-cost, efficient catalysts for biomass-related hydrogenation processes. Download: Download high-res image (269KB) Download: Download full-size image