Hydrogen production by oxidative steam reforming of methanol over Ni/CeO_2-ZrO_2 catalysts

摘要

Single ZrO2 and mixed CeO_2-ZrO_2 oxides with different CeO__2-ZrO_2 ratios were prepared by the sol-gel method and the CeC>2 by precipitation. The prepared support were impregnated with an aqueous solution of NiCl_2-6H_2O at an appropriate concentration to yield 3 wt.% of nickel respectively in the catalysts. Catalytic materials were characterized by BET (N)_2 adsorption-desorption), SEM-EDS, XRD and TPR. The oxidative steam reforming of methanol (OSRM) reaction was investigated on these catalysts for H_2 production as a function of temperature. Depending of the CeO__2-ZrO_2 ratio; the catalysts composition has a significant influence on the surface area (BET), reduction properties and methanol conversion. XRD patterns of the Ni-base catalysts showed well defined diffraction peaks of the metallic Ni except on the Ni/CeO_2 catalyst, suggesting that on this sample all of the active phase was highly dispersed. Ni/Ceria-rich catalysts were vastly active for OSRM, giving a total CH_3OH conversion at 325 ℃ with GHSV = 0.3 × 10~5 h~(-1). They also showed close selectivity toward H_2, with high selectivity to CO_2 in all range of temperatures, this suggests that the reverse WGS reaction does not occur on these samples. It seems that the nickel is the phase mainly responsible of hydrogen production although the CeO__2-ZrO_2 support reduces the CO formation.