Promoting Effect of Zn on Pd/MoC Catalyst for the Hydrogen Production From Methanol Steam Reforming

In this work, a series of Zn-doped Pd/MoC catalysts with different Zn loadings were prepared and employed for the hydrogen production from methanol steam reforming (MSR) at low temperature. The catalysts prepared in this study were fully analyzed by different characterization technologies. The results showed that the addition of small amounts of Zn to Pd/MoC catalyst favored the formation of α-MoC_1-x phase and raised the Pd dispersion on the surface of MoC, which led to increased catalytic activity (in terms of methanol conversion and H₂ production rate) for MSR. By comparison, the ZnPd/MoC catalysts with high contents of Zn exhibited poor hydrogen production activity at the same reaction conditions. This could be attributed to the fact that the introduction of high contents of Zn into Pd/MoC catalyst decreased the formation of α-MoC_1-x phase and weakened the interaction between Pd particles and MoC. However, the ZnPd/MoC catalysts with high contents of Zn showed lower CO selectivity, attributable to the existence of more Pd-Zn alloy. The optimal 0.5ZnPd/MoC catalyst possessed the best catalytic activity for MSR at 160 °C. In addition, despite deactivation at the initial stage of reaction, the 0.5ZnPd/MoC catalyst exhibited a stable catalytic activity at 160 and 240 °C during 170 h of continuous running. From the results, this study provides a way to the rational design of catalysts with high activity and selectivity for MSR at low temperature.