Hydrogen Production Via Catalytic Partial Oxidation Of Methane On Lanthanum Oxide and Nickel-Lanthanum Oxide Catalysts

Lanthanum oxide (La2O3) has been of interest as a catalyst due to its lattice Oxygen content and relatively low cost. However, it has been known to promote complete oxidation, rendering it unusable for Hydrogen production through the catalytic partial oxidation (CPO) of methane. Although some previous studies have been carried out CPO of methane on La2O3, a detailed analysis of the promotion of complete combustion even in highly reducing atmospheres has not been fully documented.It was observed that when 5 wt% of Nickel was loaded on La2O3 catalyst (Ni/ La2O3), the Hydrogen selectivity increased to almost 8 times. In this paper, we report coking studies during long term tests on both La2O3 and Ni/ La2O3 catalysts.

La2O3, prepared by solution combustion method and Ni/La2O3, prepared by chemical reduction method, were used in granule form and were packed inside a quartz tube. Nitrogen was used as the carrier gas for methane and Oxygen. Operating conditions such as temperature, residence time and O/C ratio were first optimized so as to get maximum Hydrogen yield. The CPO reaction was carried out in a temperature range of 200-750°C.

Results indicate that both methane and Oxygen conversions increase with temperature. An optimum in methane conversion was observed with residence time, indicating a complex interaction between lattice Oxygen and coke formation. The decrease in conversion was thought to be because of coke deposition on the catalyst which has the capability of deactivating the catalytic activity. A long term durability test for 160 h was done for the reaction and amount of carbon deposited was quantified by conducting TGA analysis. The nature of the coke deposited was studied using FTIR and SEM. These results are part of a larger effort aimed at understanding the catalysis of La2O3 and Ni/La2O3 systems.