Hydrogenolysis process for lignosulfonate depolymerization using synergistic catalysts of noble metal and metal chloride†
A novel hydrogenolysis process for lignosulfonate depolymerization was proposed using a noble metal catalyst cooperated with metal chloride in methanol. Hydrogenolysis performance was significantly affected by the catalysts, via a synergistic catalytic effect between the Lewis acid (metal chloride) and the noble metal. Reaction conditions were also optimized, with 8.6% aliphatic alcohols and 9.2% monomers obtained at 280 °C for 5 h over Pt/C cooperated with CrCl3. Analysis of the depolymerized products indicated that CrCl3 had a catalytic promoting effect on cleavage of β-O-4 bonds with the synergistic catalytic effect of Pt/C. Meanwhile, the noble metal catalysed saturation of the depolymerized products and suppressed them from condensing into residues. The sulfonic groups of lignosulfonate were cleaved and they did not cause Pt/C poisoning. The catalyst showed good recyclability, with no significant loss of catalytic activity after three runs.