Effect of calcination temperature on the performance of ZnCr based catalyst in isobutanol synthesis

The effect of calcination temperature on the performance of ZnCr based catalysts in isobutanol synthesis was investigated; the texture properties, bulk structure, reducibility and surface composition of the catalysts were characterized by BET, XRD, H₂-TPR and XPS. The results indicate that both the activity and product selectivity of the ZnCr catalyst are greatly influenced by its calcination temperature. The catalyst calcined at low temperature shows high selectivity to methanol and isobutanol, while the product distribution over the catalyst calcined at high temperature obeys the A-S-F equation. Calcination at 300℃ is insufficient to get a complete formation of non-stoicheiometric spinel Zn_xCr_2/3(1-x)O, while calcination at 400℃ gives the maximum amount of non-stoichiometric spinel Zn_xCr_2/3(1-x)O in the ZnCr based catalyst; however, further increasing the calcination temperature may cause the decomposition of certain non-stoicheiometric spinel Zn_xCr_2/3(1-x)O to ZnO and Cr₂O₃, which will reduce its catalytic activity in isobutanol synthesis. Such results suggest that non-stoicheiometric spinel Zn_xCr_2/3(1-x)O is possibly the active phase of the ZnCr based catalyst in isobutanol synthesis.