溶液燃烧法制备的Ni基催化剂及其浆态床甲烷化催化性能

分别以硝酸铝、硝酸氧锆、硝酸镧和硝酸铈为载体前驱体,与硝酸镍和尿素配制水溶液,采用溶液燃烧法制备了Ni-Al₂O₃、Ni-ZrO₂、Ni-La₂O₃和Ni-CeO₂催化剂,研究了浆态床CO甲烷化催化性能,并进行了低温N₂吸附-脱附、XRD、SEM、TEM、H₂-TPR和H2化学吸附等表征分析.结果表明,以硝酸铝为前驱体制备Ni-Al₂O₃催化剂时燃烧火焰稳定且持续时间长,达23 s,样品比表面积(468 m²·g^-1)和金属Ni表面积(10 m²·g^-1)均较大、Ni粒径小(3~5 nm)且分散度高,CO甲烷化催化活性和稳定性好,CO转化率和CH₄选择性分别达到94%和95%,在100 h的甲烷化反应中未出现明显失活;以硝酸氧锆和硝酸镧为前驱体制备样品时未出现明显的燃烧火焰,持续时间仅为12 s和5 s,催化剂比表面积、金属表面积及催化活性均较低;以硝酸铈为前驱体制备样品时燃烧过程迅速而剧烈,样品比表面积(22 m²·g^-1)和金属Ni表面积(5 m²·g^-1)小、Ni粒径大且分散性差,甲烷化催化性能最差,CO转化率仅为41%,CH₄选择性仅为89%.

Solution Combustion Prepared Ni-Based Catalysts and Their Catalytic Performance for Slurry Methanation

Ni-Al₂O₃, Ni-ZrO₂, Ni-La₂O₃ and Ni-CeO₂ catalysts were prepared by solution combustion method using Al(NO₃)₃, ZrO(NO₃)₂, La(NO₃)₃ and Ce(NO₃)₃ (mixed with Ni(NO₃)₂ and urea in aqueous solution) as the support precursor, respectively. The CO methanation performances of catalysts were studied in slurry-bed reactor, and the catalysts were characterized by low temperature N₂ adsorption-desorption, XRD, SEM, TEM, H₂-TPR and H₂ chemsorption. The results show that the combustion preparation process of Ni-Al₂O₃ catalyst using Al(NO₃)₂ as the precursor is stable for long-duration(up to 23 s) and the catalyst has larger surface area (468 m²·g^-1) and metal surface area (10 m²·g^-1), smaller Ni particle (3~5 nm), excellent dispersion of Ni, and the catalyst has good catalytic performance, whose CO conversion and CH₄ selectivity are 94% and 95%, respectively, and no catalyst deactivation is observed in 100 h. The preparation process for catalysts using ZrO(NO₃)₂ and La(NO₃)₃ as precursors does not show obvious flame and burning time is also shorter (12 s and 5 s), the surface areas, metal surface areas and catalytic performances are lower than that of Ni-Al₂O₃ while that for the catalyst using Ce(NO₃)₂ as the precursor has high intensity combustion. The catalyst obtained from Ce(NO₃)₂ precursor shows lower surface area (22 m²·g^-1) and metal surface area (5 m²·g^-1), larger Ni particle and worse dispersion of Ni and the worst methanation catalytic performance with CO conversion and CH₄ selectivity of 41% and 89%, respectively.