Direct catalytic conversion of glycerol to liquid-fuel classes over Ir–Re supported on W-doped mesostructured silica

Glycerol was converted to liquid fuels through a one-pot process catalyzed by mesostructured Ir–Re–W/SiO2. The reaction was performed over 0.4 g of catalyst suspended in an aqueous solution of glycerol (4.72 mmol/ml) at 553 K under a hydrogen pressure of 6.0 MPa for 50 h. A hydrocarbon-enriched organic phase was self-separated from the aqueous solution after the reaction. The total yield of oil products was greater than 40%, and the selectivity toward hydrocarbons was approximately 90%. The conversion proceeds through a complicated mechanism that involves a CC coupling reaction and hydrodeoxygenation. Doped tungsten oxide species in a silica matrix are active acidic sites for acid-catalyzed dehydration. Supported iridium species are catalytic active sites for hydrodeoxygenation and CC coupling reactions. The evolution of their chemical states during the catalytic process was detected by X-ray photoelectron spectroscopy. Rhenium species are important co-catalysts for iridium species. These active catalytic species work together to achieve the direct conversion of glycerol in aqueous solution to liquid fuels under a hydrogen atmosphere.

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► Glycerol in aqueous solution was steadily converted to liquid fuel classes.
► The one-pot process was catalyzed by well-designed mesostructured Ir–Re–W/SiO2 catalysts.
► The tungstate species are active sites over the catalyst surface for acid-catalyzed dehydration.
► Ir species are involved in hydrodeoxygenation and coupling reaction for separate organic phase.
► The oxygen concentration of the oil products is related to the proportion of Re in the catalyst.