Enhancing Hydrogen Production in Methanol Steam Reforming Using PdZn-Based Catalysts: A Mini-review on CO Suppression

Abstract

Hydrogen (H 2 ) is widely recognized as an excellent fuel for decarbonizing the fuel industry. Among various methods for its production, methanol steam reforming has emerged as a highly cost-effective approach with the unique advantage of producing it with extremely low CO levels in a one-step process. H 2 and CO 2 are primary products, while CO is secondary, usually from Reverse Water Gas Shift (RWGS) and methanol decomposition. Because CO formation occurs at the expense of H 2 quantity and purity, its suppression is essential amid growing purity and quantity demands, e.g., large amounts of H 2 with a CO content of ≤50 ppm for H 2 fuel cells, in recent years. This paper provides an overview of CO suppression over PdZn-based catalysts, which are very reliable alternatives to Cu-based catalysts. It encompasses various aspects, including the factors influencing CO selectivity, different approaches employed for CO suppression, mechanistic insights into CO formation and suppression, and resulting technoeconomic-environmental implications. Additionally, it reports feasible strategies to further explore and hopefully enhance CO suppression over these catalysts with the ultimate goal of "ideal methanol steam reforming". By discussing these potential directions, the paper provides valuable insights for future research and development.