The Effect Of Additives On The Structure And Properties Of Catalyst For Syngas Methanation

The short of natural gas and the abundant of coal are fundamental realities of our country. Natural gas can be obtained by syngas methanation which derives from coal gasification. Methanation catalyst is the core part of the research.In this paper, the Ni-based catalysts NiO/γ-Al2O3were prepared using impregnation method with the shipping NiO/γ-Al2O3and pseudo-boehmite as the supporter respectively and the catalysts NiO/M/γ-Al2O3were prepared by added oxides of alkaline-earth metal, rare-earth metal and transition metal as additives. The as-prepared catalysts were characterized by XRD and BET. The metanation catalytic properties of catalysts were investigated at different temperatures or different pressures. Furthermore the long-running stability test of catalyst was also carried out.The catalysts NiO/γ-Al2O3(A) and NiO/γ-Al2O3(B) were prepared with shipping NiO/γ-Al2O3or pseudo-boehmite as the supporter respectively through impregnation method whose NiO contents were7.5%、11.2%、18.7%、26.1%、37.4%、44.8%respectively. All the samples characterized had mesoporous structure, but its pore size distributed irregularly. According to the results of the properties evaluation of the syngas methanation, methanation catalytic activity of18.7%NiO/γ-Al2O3(A) was relatively well, its CO conversion and CH4selectivity was100%and95%respectively. The methanation catalytic properties of11.2%NiO/γ-Al2O3(A) and18.7%NiO/γ-Al2O3(A) were investigated at temperature of400℃、500℃and650℃respectively and pressure of0.1MP、1.0MPa、2.0MPa and3.0MPa respectively, the results showed that CO conversion and CH4selectivity of18.7%NiO/γ-Al2O3(A) all reached100%when pressure was above2.0MPa and temperature was400℃or500℃.The catalysts NiO/M/γ-Al2O3(A) and NiO/M/γ-Al2O3(B) were prepared with shipping γ-Al2O3or pseudo-boehmite as the supporter respectively and being added oxides of alkaline-earth metal(Mg、Ca), rare-earth metal(La、Ce、 Sm) and transition metal(Fe、Co、Ti、Zr、Mn、Cu、Mo) as additives respectively through impregnation method. The methanation catalytic activity of the catalysts added with La2O3as additives were the best. When investigating the effect of additives loading on catalytic activity, the catalyst18.7%NiO/3.2%La2O3/γ-Al2O3(A) show the best properties whose CO conversion and CH4selectivity was100%and98%respectively. The results of investigating the effect of pressures and temperatures on catalytic activity showed that high temperature was bad to methanation but high pressure, CO conversion and CH4selectivity of18.7%NiO/3.2%La2O3/γ-Al2O3(A) were reached100%when pressure was above2.0MPa and temperature was400℃or500℃. Further, the average conversion of CO and selectivity of CH4of the catatyst was99.8%and97.2%during stability test for738h which showed good stability.