2O 3, Pd–In 2O 3 and Pd–Ga 2O 3–In 2O 3 Catalysts: Influence of the Microstructure on the CO 2 Selectivity in Methanol Steam Reforming]]>

摘要

To focus on the influence of the intermetallic compound—oxide interface of Pd-based intermetallic phases in methanol steam reforming (MSR), a co-precipitation pathway has been followed to prepare and subsequently structurally and catalytically characterize a set of nanoparticulate Ga~(2)O~(3)- and In~(2)O~(3)-supported GaPd~(2)and InPd catalysts, respectively. To study the possible promoting effect of In~(2)O~(3), an In~(2)O~(3)-doped Ga~(2)O~(3)-supported GaPd~(2)catalyst has also been examined. While, upon reduction, the same intermetallic compounds are formed, the structure of especially the Ga~(2)O~(3)support is strikingly different: rhombohedral and spinel-like Ga~(2)O~(3)phases, as well as hexagonal GaInO~(3)and rhombohedral In~(2)O~(3)phases are observed locally on the materials prior to methanol steam reforming by high-resolution transmission electron microscopy. Overall, the structure, phase composition and morphology of the co-precipitated catalysts are much more complex as compared to the respective impregnated counterparts. However, this induces a beneficial effect in activity and CO~(2)selectivity in MSR. Both Ga~(2)O~(3)and In~(2)O~(3)catalysts show a much higher activity, and in the case of GaPd~(2)–Ga~(2)O~(3), a much higher CO~(2)selectivity. The promoting effect of In~(2)O~(3)is also directly detectable, as the CO~(2)selectivity of the co-precipitated supported Ga~(2)O~(3)–In~(2)O~(3)catalyst is much higher and comparable to the purely In~(2)O~(3)-supported material, despite the more complex structure and morphology. In all studied cases, no deactivation effects have been observed even after prolonged time-on-stream for 12?h, confirming the stability of the systems. Graphical Abstract The presence of a variety of distinct supported intermetallic InPd and GaPd~(2)particle phases is not detrimental to activity/selectivity in methanol steam reforming as long as the appropriate intermetallic phases are present and they exhibit optimized intermetallic-support phase boundary dimensions.