制备方法对Ni基甲烷化催化剂活性和抗硫性能的影响

Effect of Preparation Method on Activity and Sulfur Resistance of Nickel-based Methanation Catalysts

镍基催化剂由于活性高选择性好广泛应用于CO甲烷化反应,然而该催化剂极易硫中毒而导致失活,急需开发高效稳定和耐硫性能好的镍基催化剂。制备方法对于催化剂物化和织构性质有非常重要的影响,本文采用浸渍法和水解共沉淀法分别制备了NiO质量分数为20%的镍基催化剂,通过H2化学吸附、BET、XRD、H2-TPR、Raman及XPS等分析手段对催化剂进行详细表征;并采用固定床微反应装置对CO甲烷化反应的活性和抗硫性能进行系统评价。结果表明,共沉淀法制备的20Ni-Al2O3催化剂低温活性和抗硫性能均优于浸渍法制备的20Ni/Al2O3催化剂,在t=240℃、p=0.1 MPa和WHSV=20000 mL·g-1·h-1条件下,20Ni-Al2O3催化剂的CO转化率和CH4收率分别达到99%和97%以上,H2S脉冲注入量累计达1.5 mL时,CO转化率可达75%、CH4收率为61%。20Ni-Al2O3催化剂表面Ni的活性比表面积较大产生更多的活性位,导致其低温活性较高,对H2S的吸附量增加,减缓硫中毒,提高了催化剂的抗硫性能。

Nickel-based catalyst is widely used in CO methanation reaction owing to its high activity and selectivity.However,the catalyst is very prone to sulfur poisoning,leading to deactivation.It is urgent to develop nickel-based catalyst with high efficiency,stability,and good resistance.It is well known that different preparation methods have obvious influence on physicochemical and textural properties of the catalyst.In this paper,nickel-based catalyst with NiO content of 20%was prepared by wet impregnation and co-precipitation methods separately.The catalysts were characterized by means of H2 chemical adsorption,BET,XRD,H2-TPR,Raman Spectrometry,and XPS.The activity and sulfur resistance of the catalyst for CO methanation reaction were systematically evaluated in a fixed bed microreactor.The results show that the 20Ni-Al2O3 catalyst prepared by precipitation method exibited better activity and sulfur resistance than that prepared by impregnation(20Ni/Al2O3).Under the conditions of t=240℃,p=0.1 MPa,and WHSV=20000 mL·g-1·h-1,the CO conversion rate over 20Ni-Al2O3 catalyst was 99%,and the yield of CH4 was above 97%.CO conversion rate and the yield of CH4 were 75%and 61%when the accumulative amount of H2S pulse injection was 1.5 mL.The excellent activity and sulfur resistance of 20Ni-Al2O3 catalyst are due to the large specific surface area of Ni on catalyst surface generating more active sites,leading to its high low temperature activity.The increase of H2S adsorption capacity may effectively delay sulfur poisoning and improve sulfur resistance.