Comparative study between Zn–Pd/C and Pd/ZnO catalysts for steam reforming of methanol Original Research Article

Catalytic activity and CO2 selectivity over carbon black-supported Pd with the addition of Zn (Zn–Pd/C) was comparable to those of Pd/ZnO in methanol steam reforming. From the characterization of fresh Zn–Pd/C after H2 reduction pretreatment by means of BET surface area, XRD, TEM and the measurement of CO adsorption, Pd–Zn alloy particles were detected on Zn–Pd/C. This is also supported by high CO2 selectivity in methanol steam reforming over Zn–Pd/C as well as Pd/ZnO. In addition, Zn–Pd/C exhibited higher stability than Pd/ZnO in methanol steam reforming. After the reaction for the life test, the formation of zinc carbonate hydroxide such as Zn4CO3(OH)6·H2O was clearly observed on Pd/ZnO. It is expected that the deactivation is caused by covering active Pd–Zn alloy particles with zinc carbonate hydroxide. Although this phenomenon can also occur on Zn–Pd/C, the deactivation rate was much lower than Pd/ZnO because the amount of free ZnO is much smaller on Zn–Pd/C.