Catalytic decomposition of natural gas for COx-free hydrogen production in a structured multilayer reactor Original Research Article

Using a new structured multilayer reactor (MLR) that houses Ni based thin layer catalysts, catalytic decomposition of natural gas (CDNG) for making “COx-free” hydrogen in a TR range of 773–873 K was investigated. The influence of Ni loading (5–50 wt%), Ni particle size, TR, and GHSV (h−1) on the reaction pattern was evaluated. A volcano shape relationship between H2 space time yield image and Ni loading with a maximum range of 20–25 wt% was found. H2 productivity and catalyst lifetime are controlled by the nature of the coke formed on Ni active species. As such, TR and GHSV significantly affect both the kinetics and the mechanism of coking. At TR < 873 K and low GHSV (<2000 h−1), the prevailing formation of filamentous carbon (whisker-like) prolongs the catalyst lifetime, while at TR = 873 K and high GHSV (>2000 h−1) encapsulating carbon is formed, causing a sudden decline in catalytic activity. A preliminary attempt to find optimal operating conditions ensuring the highest values of H2 productivity is presented. The features of the MLR that allowed CDNG reaction under a quasi-isothermal regime without any pressure drop, irrespective of operating conditions and the extent of carbon formation, are discussed.