Reactive metal-support interaction in the Cu-In2O3 system: intermetallic compound formation and its consequences for CO2-selective methanol steam reforming

Kevin Ploner,Lukas Schlicker,Albert Gili,Aleksander Gurlo,Andrew Doran,Lei Zhang,Marc Armbrüster,Dagmar Obendorf,Johannes Bernardi,Bernhard Klötzer,Simon Penner

doi:10.1080/14686996.2019.1590127

Abstract

ABSTRACT The reactive metal-support interaction in the Cu-In2O3 system and its implications on the CO2 selectivity in methanol steam reforming (MSR) have been assessed using nanosized Cu particles on a powdered cubic In2O3 support. Reduction in hydrogen at 300 °C resulted in the formation of metallic Cu particles on In2O3. This system already represents a highly CO2-selective MSR catalyst with ~93% selectivity, but only 56% methanol conversion and a maximum H2 formation rate of 1.3 µmol gCu −1 s−1. After reduction at 400 °C, the system enters an In2O3-supported intermetallic compound state with Cu2In as the majority phase. Cu2In exhibits markedly different self-activating properties at equally pronounced CO2 selectivities between 92% and 94%. A methanol conversion improvement from roughly 64% to 84% accompanied by an increase in the maximum hydrogen formation rate from 1.8 to 3.8 µmol gCu −1 s−1 has been observed from the first to the fourth consecutive runs. The presented results directly show the prospective properties of a new class of Cu-based intermetallic materials, beneficially combining the MSR properties of the catalyst’s constituents Cu and In2O3. In essence, the results also open up the pathway to in-depth development of potentially CO2-selective bulk intermetallic Cu-In compounds with well-defined stoichiometry in MSR.

Highlights

Methanol steam reforming (MSR) remains one of the most important reactions in hydrogen economy to access large amounts of hydrogen that can subsequently be used as a renewable energy carrier [1]
For the diluted sample of 9.4 mg CuO/c-In2O3 with the same nominal copper content dissolved in 100 ml 7% HNO3, an average amount of 4.65 ppm Cu was found by DPP
We have shown that reactive metal-support interaction in the Cu-In2O3 system leads to the formation of an intermetallic Cu2In compound after reduction in hydrogen at 400 °C

Summary

Introduction

Methanol steam reforming (MSR) remains one of the most important reactions in hydrogen economy to access large amounts of hydrogen that can subsequently be used as a renewable energy carrier [1]. In2O3 is the archetypical beneficially acting oxide entity, as it is a highly CO2-selective (yet comparably inactive) catalytic material in MSR by itself [19] but has recently been reported to act as a superior catalyst for the methanol synthesis by CO2 hydrogenation [20]. As the removal of reaction-induced water is a key parameter in the efficient formation of intermetallic compounds, we will perform experiments under recirculating batch and quasi-flowing conditions This potentially enables us to access different oxide-supported single-phase intermetallic Cu-In compounds, whose catalytic properties can be assessed. An integral part of the characterization will be devoted to synchrotron-based in situ X-ray diffraction (XRD) measurements to follow the structural transitions in the course of reactive metal-support interaction

Experimental details

Catalytic measurements

Structural characterization

Results and discussion

Conclusions