Excess of nio loading - key for catalyst activity decline prevention

Summary

The activity of co-precipitated NiO-Al₂O₃ catalyst for partial oxidation of methane in a steel flow reactor was investigated. The catalyst samples loaded with 5, 10 and 20 wt.% nickel before use were thermally treated at 400, 700 and 1100^oC.  The feed gas for catalytic oxidation was prepared by dilution of natural gas with air, and had approximately the following volume composition: CH₄: O₂: N₂ = 5: 2: 8. The reaction was carried out over 100 mg unreduced NiO-Al₂O₃ catalyst at gas flow rate of 50 cm³/min at 650^oC and atmospheric pressure. The catalyst activity with 5 and 10 wt.% of nickel was very similar, decreasing with enhance of previous heat treatment. Further nickel loading did not increase significantly the catalyst activity compared to low level nickel samples. However, high nickel content has a levelling effect on catalyst activity, suppressing the undesired effect of previous heat treatment at high temperature