Benzaldehyde reduction over Cu–Al–O bimetallic oxide catalyst. Influence of pH during hydrothermal synthesis on the structural and catalytic properties

•Cu–Al–O bimetallic oxide was prepared by varying the pH during synthesis.•The catalytic performance of Cu–Al–O in the reduction of benzaldehyde is studied.•The basic pH value during preparation has a strong influence on the system activity.•A high pH enhances both the reducibility of Cu2+ and the dispersion of Cu species.

The Cu–Al–O bimetallic oxide was prepared by varying the pH during synthesis. The samples were characterized by several techniques (BET, TGA, XRD, LRS, EDX and XPS). Their behavior during reduction by hydrogen was examined by in situ X-ray diffraction and by X-ray photoelectron spectroscopy. The catalysts were studied in the reduction of benzaldehyde in the 150–200 °C temperature range. The choice of pH value of the material preparation influenced strongly the textural and structural properties of the bimetallic system, as well as their reactivity. When the catalyst was prepared in highly basic medium (pH = 12), benzyl alcohol was obtained with high selectivity (96%) and at high conversion (78%), while toluene was the only product observed when preparation was carried out at pH = 8. The marked divergence in behavior from the two systems may be accounted for by their acid–base and reducibility properties, dispersion and environment of copper.

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