Solvent controlled catalysis: Synthesis of aldehyde, acid or ester by selective oxidation of benzyl alcohol with gold nanoparticles on alumina

• Benzyl alcohol oxidation was studied in different solvents and biphasic solvent.
• The Au/Al2O3 catalyst was prepared by direct-ion exchange.
• Benzaldehyde, benzoic acid or benzoic esters were selectively produced.
• Alkaline biphasic solvent enhanced the catalytic activity TOF value being 5200 h−1.

As shown herein, selectivity of aerobic oxidation of benzyl alcohol with gold nanoparticles dispersed on Al2O3 support is solvent-controlled. Using different solvents, the reaction was directed toward a variety of products: benzaldehyde, benzoic acid or benzoic esters were selectively produced from benzyl alcohol depending on the conditions. In toluene, benzaldehyde was produced with high selectivity, while quantitative conversion to benzoic acid was achieved in alkaline water. In methanol, methyl benzoate was produced with very high yield. Moreover, activity of the catalyst was dramatically improved without loss of selectivity in biphasic media; with a toluene/alkaline water system the highest TOF for benzoic acid synthesis was close to 5200 h−1, selectivity being 98%.

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