The structure and performance of (Ni4Fe)mAg(PrZr4)nOx catalyst for ethanol steam reforming

Abstract

Co-precipitation method is used to synthesize PrpZrqOx composite oxide support and impregnation method is adopted in preparing (Ni4Fe)mAgPrpZrqOx catalysts. X-ray power diffraction (XRD), Temperature programmed reduction (TPR) and Temperature programmed oxidation (TPO) are used to characterize the catalysts. The results indicate that not only the improvement of catalytic activity is remarkable, but also an excellent capacity of resistance to carbon deposition when Ag dropped into the Ni-Fe bimetallic catalysts. XRD spectrum of the fresh (Ni4Fe)mAg(PrZr4)nOx catalysts present characteristic diffraction peak of tetragonal crystal phase ZrO2, rhombohedral Fe2O3, hexagonal NiO and cubic Ag2O while no diffraction peak of praseodymium oxide appears because the doped praseodymium ions can enter the ZrO2 lattice. After 823K’s pretreatment by H2, the main active components are cubic Ni0 and cubic Ag0. TPR shows that the presence of Ag is of great benefit to the reduction of Fe2O3 and NiO: the peaks maximum due to the Fe2O3→Fe3O4 and NiO→Ni0 reduction of the Ag-containing sample are shifted by more than 150K to lower temperatures in comparison with Ni-Fe bimetallic metallic catalysts. (Ni4Fe)16Ag(PrZr4)64.8Ox catalyst shows its best catalytic activity in ethanol steam reforming. Under the following conditions, reaction temperature 773K, ethanol/water with molar ratio of 1:6, weight hourly space velocity (WHSV) of 11.8 h−1, the ethanol conversion rates are nearly 100% and the molar percentage of H2, CO, CH4, CO2 are 70.5%, 1.8%, 7.9%, and 19.6% respectively.