Hydrocarbon Reforming for Hydrogen Fuel Cells: A Study of Carbon Formation on Autothermal Reforming Catalysts. Final Report

摘要

The mechanism of carbon formation on nickel autothermal steam reforming catalysts has been studied by temperature-programming, thermogravimetric and electron microscopic techniques. Temperature-programmed surface reaction (TPSR) studies of carbon deposited on nickel reforming catalysts by the decomposition of C sub 2 H sub 4 and C sub 2 H sub 2 exhibit seven forms of carbon that are distinguished by their characteristic reactivity with H sub 2 and 3.0-vol % H sub 2 O/He. The relative population of the different carbon states depends primarily on the temperature during deposition. C sub 2 H sub 2 exposure populates the same carbon states as C sub 2 H sub 4 exposure but at approximately 100 exp 0 K lower deposition temperature. Similar carbon states were found on all nickel catalysts studies including Ni/ gamma -Al sub 2 O sub 3 and Ni/MgO-Al sub 2 O sub 3 leading to the conclusion that the support has little effect on carbon deposit formation and reactivity. The reactivity of the carbon states is not altered by exposure to steam in C sub 2 H sub 4 -H sub 2 O mixtures, but the amount of carbon deposited decreases to zero as H sub 2 O/C increases past a critical ratio.