Modification strategies for enhancing anti-coking of Ni-, Co-based catalysts during ethanol steam reforming: A review

Producing hydrogen from ethanol steam reforming (ESR) is a carbon-neutral and environment-friendly method, which has been expected to gradually reduce excessive emission of environmental pollution and over-exploitation of fossil resources. Low-cost nickel (Ni) and cobalt (Co) are considered the most promising active metals for industrial ESR catalysts, with the challenge that carbon deposition on such catalysts causes active site loss which limits their application. In this review, comprehensive knowledge on the ESR reaction mechanism and carbon deposition process were summarized. Based on understanding of the reaction mechanism, an anti-coking strategy keeping a balance between C–C bond scission and oxidation of hydrocarbon species was proposed. Two aspects of this strategy, including (i) enhanced C–C bond scission capability of metal, (ii) promoting effects of support for protecting the activity of metal particles and removing surface carbon, were particularly described. The revelation between the intermediate reaction and modification strategy enables the successful design of new and stable catalysts for improving anti-coking ability. This review not only shed light to the development of high-performance industrial ESR catalysts, but also contribute an innovative perspective to understand anti-coking mechanism for steam reforming of CH3CHO, CH3COOH, CH3COCH3, and even crude bio-oil.