Journal Article

Impregnated and Co-precipitated Pd-Ga 2 O 3 , Pd-In 2 O 3 and Pd-Ga 2 O 3 -In 2 O 3 Catalysts: Influence of the Microstructure on the CO 2 Selectivity in Methanol Steam Reforming

Rameshan, Christoph, Götsch, Thomas, Penner, Simon, Ploner, Kevin, Lorenz, Harald, Armbrüster, Marc, Kasatkin, Igor, Klötzer, Bernhard

2018

Overview

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 O - and In O -supported GaPd and InPd catalysts, respectively. To study the possible promoting effect of In O , an In O -doped Ga O -supported GaPd catalyst has also been examined. While, upon reduction, the same intermetallic compounds are formed, the structure of especially the Ga O support is strikingly different: rhombohedral and spinel-like Ga O phases, as well as hexagonal GaInO and rhombohedral In O 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 selectivity in MSR. Both Ga O and In O catalysts show a much higher activity, and in the case of GaPd -Ga O , a much higher CO selectivity. The promoting effect of In O is also directly detectable, as the CO selectivity of the co-precipitated supported Ga O -In O catalyst is much higher and comparable to the purely In O -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. The presence of a variety of distinct supported intermetallic InPd and GaPd 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.