Selective hydrogenation of benzaldehyde to benzyl alcohol over Au/Al2O3

We provide the first evidence of exclusive benzyl alcohol production in the continuous gas phase hydrogenation of benzaldehyde (T = 393 K; P = 1 atm) over Au/Al2O3, where activity was largely maintained for up to 15 h on-stream. XRD and DRS UV–vis have established the presence of metallic Au post temperature programmed reduction to 473 K, with a surface area weighted mean Au particle size (from TEM analysis) of 7.9 nm. Under the same reaction conditions, Ni/Al2O3 and Pd/Al2O3 were non-selective, generating toluene as the principal product via hydrogenolysis of benzaldehyde and exhibiting an appreciable temporal loss of activity. The results establish Au/Al2O3 as a promising catalyst for the production of benzyl alcohol.

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► First evidence of exclusive benzyl alcohol production via continuous gas phase benzaldehyde hydrogenation over Au.
► 100% selectivity to benzyl alcohol over Au/Al2O3 under conditions where Ni/Al2O3 and Pd/Al2O3 promote toluene formation.
► Selective hydrogenation maintained over Au/Al2O3 with time on-stream but temporal loss of activity exhibited by Ni/Al2O3 and Pd/Al2O3.