Unraveling the Hydrogenolysis of Isosorbide to Diols and Triols Over a Silica‐Supported Rhodium Catalyst

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Abstract
Silica‐supported Rh catalyst (Rh/SiO 2 ) is an effective catalyst for the transformation of isosorbide to value‐added triols and diols; however, the underlying reaction pathways remain insufficiently understood. In this work, we examine the kinetics of isosorbide hydrogenolysis, along with hydrogenolysis of representative model compounds over an Rh/SiO 2 catalyst to clarify the substrate structure–reactivity relationships. Based on the dependence of substrate concentration and hydrogen pressure, the hydrogenolysis of C─O or C─C bonds is the rate‐determining step of isosorbide hydrogenolysis over Rh/SiO 2 . From comparisons of reactivity and selectivity using various model substrates, it is evident that the ring‐opening cleavage of the ether C─O─C bond is much more reactive than that of C─OH bond. Furthermore, an investigation combining product distribution tendency using 3‐hydroxy‐THF as a model substrate for isosorbide revealed that simultaneous cleavage of the C─O─C and the C─OH bonds also occurs. Two dominant pathways for the hydrogenolysis of isosorbide are as follows: (i) ring‐opening cleavage of the C─O─C bond alone and (ii) simultaneous cleavage of the C─O─C and the C─OH bonds, which can explain the formation of the main products (1,6‐hexanediol, 3,4‐hexanediol, and 1,2‐pentanediol) from isosorbide. These insights clarify the reaction behavior over Rh/SiO 2 , providing guidance for the rational design of catalysts for the hydrogenolysis of isosorbide and related biomass‐derived substrates.

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