CO2 reforming of methane to synthesis gas over sol-gel-made Ni/γ-Al2O3 catalysts from organometallic precursors

Abstract

Considerable interest is being lavished on CO2 reforming of methane to synthesis gas because it yields synthesis gas with a high CO/H2 ratio that is ideal for the synthesis of higher hydrocarbons and oxygenated derivatives. The catalytic activity and coking resistivity of three Ni-based catalysts for CO2 reforming of methane to synthesis gas were investigated in a continuous-flow microreactor under 1 atm. These catalysts were prepared by conventional impregnation of commercial γ-Al2O3 support (NiAlCO-IM), sol-gel-made γ-Al2O3 (NiAlSG-IM), and direct sol-gel processing from organometallic compounds (NiAlsG). The three catalysts had comparable activity but showed considerable variation in coking resistivity. NiAlSG-IM catalyst had excellent coking resistivity with no obvious coke even after 80 hr of reaction on stream, under thermodynamically severe conditions. A little coke deposited on NiAlSG. In comparison, fast and heavy coke deposition was detected on NiAlCO-IM catalyst and the reaction was sustained only about 3.5 hr accompanied with the plugging of reactor. NiAlSG-IM catalyst prepared from organometallic compounds had very high BET surface area and small metallic Ni particles. The small size of metallic Ni particles was a major inhibitor of coke formation. The critical size of Ni particles to inhibit coke deposition was suggested at ~ 10 nm. Prevention of coke formation may also be achieved with γ-Al2O3 support made from sol-gel processing of organometallic precursors.