High-temperature methanation Ni/Al2O3 catalysts and reforming catalysts
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What is the mechanism behind the high-temperature resistance of methaneation Ni/Al2O3 catalysts (such as the JM and BASF catalysts used for coal methaneation)? Does it depend on the carrier, the Ni content, the interaction between the two, or some additive? There is one point that is not clear: Can an NG water vapor reforming catalyst, which can withstand temperatures of over 700°C and has a NiO content of around 15%, be used directly as a methanation catalyst? Of course, the operating conditions and gas composition must be considered. If the gas components mainly consist of CO, CO2, H2, and NG, are there any other issues with using a steam reforming catalyst for methanation? Happy New Year! Wishing all the heroes a prosperous new year.
Under normal catalyst compositions, the higher the Ni content, the better the high-temperature resistance. The reaction of methane reforming involves the production of CO+H2 at high temperatures; this reaction is endothermic and proceeds rapidly. It is limited by thermodynamic equilibrium, while in industrial applications it is constrained by heat transfer issues. Catalyst design requires certain properties such as thermal stability as well as physical and mechanical characteristics. Due to the fast reaction rates at high temperatures, catalyst activity is not a critical factor, nor is a high Ni loading necessary; instead, it is important to find a carrier that has sufficient strength and can stabilize the active components. The 15% reverse methanation reaction you mentioned is exothermic; at low temperatures (3–500 degrees), the equilibrium yield is good. Therefore, high catalyst activity becomes a key issue, and Ni must be used in high loadings. A preparation method that can produce small Ni microcrystals should be chosen, and a high metal surface area must be maintained even under conditions of large exothermic reactions to avoid sintering; the catalyst design must also be different, as well as the type of reactor. The Ni used in companies is 40-50%.
In my opinion, the heat resistance of a catalyst has little to do with the amount of active components present; what’s more important is the high-temperature resistance of the carrier and the role of key additives. Although reforming catalysts contain NI as an active component. But the selectivity is unknown
I believe the key is to ensure adequate distribution of the nickel active sites, so that nickel crystals do not aggregate at high temperatures.