Low-temperature Selective CO Methanation over Unsupported Nickel Catalyst Covered by Silica Thin Layer

摘要

The catalytic performance of unsupported Ni catalyst covered by a silica thin layer with core-shell structure for selective CO methanation was investigated. The thin silica layer prepared with a silane coupling agent as the silica source effectively suppressed Ni-sintering even at quite low Si/Ni ratio. Due to the low Si/Ni ratio, the Ni surface area of the catalyst was increased by 20 % compared to the conventional unsupported Ni catalyst and outlet CO concentration reached less than 10 ppm even at low temperature (155 degrees C). The durability test revealed that outlet CO concentration was maintained at less than 10 ppm during operation for 3000 h over the developed catalyst even under severe conditions (SV 4800 h(-1), inlet CO concentration 0.5 %). Further improvement of the catalyst selectivity is necessary because the operating window for the developed catalyst, in which outlet CO concentration is less than 10 ppm and CH4 formation is less than 1 %, was almost the same as that for the conventional catalyst.