Catalytic Decomposition of Natural Gas for COx-Free Hydrogen Production in a Structured Multilayer Reactor

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 (h1) on the reaction pattern was evaluated. A volcano shape relationship between H2 space time yield ðSTYH2 ; st p dm3 H2=kgNi=hÞ andNi loadingwith a maximumrange 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 h1), the prevailing formation of filamentous carbon (whisker-like) prolongs the catalyst lifetime, while at TR = 873 KandhighGHSV(>2000 h1) incapsulatingcarbonis formed,causing a suddendecline in catalytic activity.Apreliminary attempt to findoptimal operating conditions ensuring the highest values of H2 productivity is presented. The features of theMLRthat allowedCDNGreaction under a quasi-isothermal regime without any pressure drop, irrespective of operating conditions and the extent of carbon formation, are discussed.