Effect of CeO_2 loading on the performance of Pd/γ-Al_2O_3 catalysts for one-step synthesis of dimethyl ether

摘要

A series of Pd-CeO_2/γ-Al_2O_3 catalysts which have a different CeO_2 loading were prepared by impregnation under microwave irradiation. Based on various characterizations, such as XRD, H2-TPR and CO-TPD, the effect of CeO_2 loading on catalytic performance and stability of Pd/γ-Al_2O_3 were examined for one-step dimethyl ether synthesis from syngas. The results show that there are two completely opposite effect on the CO conversation rate of Pd/γ-Al_2O_3 catalysts after adding CeO_2, namely that it can improve Pd dispersion at a suitable loading, hence the CO conversation rate will increase too. However, the surface area and total pore volume of Pd/γ-Al_2O_3 catalysts decrease by adding excessive CeO_2 and CO conversation rate will also reduce. When the CeO_2 loading achieve to 2%, catalysts can have relatively high catalytic stability and activity that the CO conversation rate and DME space-time yield can reach 64.7% and 27.82 mmol·ml~(-1)·h~(-1), respectively.