ZnO is a CO ₂-selective steam reforming catalyst

Abstract

Graphical abstract

A surprisingly high CO ₂-selectivity (95–99.6%) of single-phase ZnO in methanol and formaldehyde steam reforming, which helps in gaining enhanced understanding of the catalytic performance of the unsupported and supported intermetallic compound ZnPd, has been observed.

Highlights

► ZnO is a CO ₂-selective methanol steam reforming catalyst. ► ZnO selectively catalyzes formaldehyde via steam reforming to CO ₂. ► A beneficial role of ZnO in oxidizing formyl-containing species is evident in ZnO supported systems.

Abstract

ZnO was tested as possible methanol and – since formaldehyde is one of the key intermediates in methanol conversion reactions – also as formaldehyde steam reforming catalyst. Catalytic experiments in a batch as well as a flow reactor resulted in highly selective steam reforming, though at low specific activities, of formaldehyde and methanol over ZnO toward CO ₂ (selectivity of 95–99.6%). Comparison of the behavior of ZnPd near-surface intermetallic phases, unsupported intermetallic ZnPd and supported ZnPd/ZnO catalysts reveals that formaldehyde is formed from methanol in parallel with CO ₂ on the former, while on unsupported intermetallic ZnPd and ZnO-supported ZnPd, it is efficiently reacted toward CO ₂, thus, a beneficial role of ZnO in oxidizing formaldehyde-derived intermediates toward CO ₂ is evident.