Study on catalyst for hydrogenation of methyl benzoate to benzaldehyde at low H₂/ester molar ratio

The effects of ZnO/MnO mass ratio and ZnO, MnO and K⁺ loading amount on the activity and selectivity of catalyst used for the hydrogenation of methyl benzoate to benzaldehyde at 1.5 molar ratio of H₂/Ester were studied. The results showed that the catalytic activity was higher when MnO/ZnO mass ratio was 1. The conversion was over 99% when the loading amount of activity component was 25%-30% and temperature was 440°C. Al₂O₃ carrier was no activity, but X-Ray Diffraction (XRD) analysis showed that Al₂O₃ carrier could distributed the activity components well in its surface and made the catalytic activity increasing. The suitable KC1 mass fraction was 3%. The activity and selectivity was 93.51% and 79.83% respectively, by using 3% KCl-25% MnO-ZnO/γ-Al₂O₃ catalyst for the hydrogenation of methyl benzoate to benzaldehyde under the atmospheric pressure, 420°C, resident time 250 (g·h)/mol and 1.5 H₂/Ester molar ratio. Conversion was only 22.60% and 18.96% when K-MnO/γ-Al₂O₃ and Li-ZnO/γ-Al₂O₃ catalysts reported in previous literatures were respectively used under the same reaction conditions. It was showed that the catalytic activities were greatly reduced when the catalysts reported in previous documents were used at low H₂/Ester molar ratio.