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Monolithic ruthenium catalysts (Ru/inorganic washcoat/cordierite) were evaluated for use in a monolith loop reactor process for hydrogenating glucose to sorbitol. Washcoat formulations included alumina, silica, titania, zirconia, and selected mixed oxides. Commercially attractive reaction rates were attained with several catalysts. Rates normalized to the amount of Ru were lower for monolithic catalysts than for Ru/C slurry catalyst benchmarks, most likely because of internal mass-transfer limitation. The concentrations of reaction byproducts (gluconic acid, ethylene glycol, and mannitol) were analyzed by high-performance liquid chromatography and are compared to slurry benchmarks. Selected monolithic catalysts exhibited a slow but steady activity decline in extended life testing (tens of runs); the deactivation mechanism has not yet been elucidated. With some further catalyst optimization, monolith catalysts can successfully replace the Raney nickel catalysts currently in use at the commercial scale, lower the overall catalyst cost, and reduce metal leaching into the reaction product.

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