Metal Catalyst-Dependent Poisoning Effect of Organic Sulfur Species for the Hydroconversion of 5-Hydroxymethylfurfural

We disclose the mechanism of catalystpoisoning by organicsulfur species that are present in commercial 5-HMF feedstock duringits hydroconversion. The transformation of 5-hydroxymethylfurfural (HMF) intoring-saturatedfuranics is a vital step in carbohydrate valorization. In this work,we report on the remarkable catalyst poisoning effect of numeroussulfur species for HMF hydroconversion. The presence of minor amountsof dimethyl sulfoxide (DMSO) affects ring-saturated product selectivityfor the metal-catalyzed reactions using molecular hydrogen, whereasit fully deactivates catalytic transfer hydrogenation (CTH) in 2-propanol.The degree of poisoning correlates with the thermodynamic favorabilityof the metal sulfide formation. Reduced sulfur species (sulfide orthiol) are the ultimate metal poisoning agent. Their easy formationfrom more oxidized sulfur compounds explains the observed poisoningeffect for such species. Here, the metal's oxophilicity determinesthe catalysts' behavior in the presence of oxidized sulfurspecies by forming (or not) poisoning sulfur-metal interactions.To overcome the sulfur poisoning, we propose DMSO removal with organicsolvent extraction and catalyst oxidation post-treatment. These findingspinpoint the crucial, though overlooked, role of the biobased HMFpurity for reductive catalytic studies. We provide a deeper understandingof the noble metal poisoning by sulfur from different origins andoxidation states that may be present during HMF hydroconversion.