铁基微胶囊催化剂制备及在CO_2甲烷化反应中的性能研究

Preparation of Fe-based microcapsule catalysts and performances in CO_2 methanation reaction

以Fe_2O_3、CTAB、TEOS、氨水和氯钯酸铵为原料,采用浸渍法和溶胶-凝胶法制备了Fe_2O_3@SiO_2、Fe_2O_3@SiO_2-PdO、PdO-Fe_2O_3@SiO_2-1和PdO-Fe_2O_3@SiO_2-2微胶囊催化剂,在高压固定床反应装置上评价了催化活性。通过XRD、H_2-TPR、TEM和N_2物理吸附等方法对催化剂进行了表征。结果表明,无定型SiO_2均匀包覆在α-Fe_2O_3粒子上,制得了微米级胶囊催化剂,且具有介孔结构,比表面积较大,对CO_2甲烷化反应的催化性能明显改善,CH_4选择性大幅提高。与Fe@SiO_2-Pd相比,在Pd-Fe@SiO_2-1和Pd-Fe@SiO_2-2催化剂上,CH_4选择性大幅提高,充分体现了催化剂核内Pd与Fe间的协同催化作用。SiO_2膜太厚,不利于CO_2甲烷化反应,在膜厚度适中的Pd-Fe@SiO_2-1催化剂上,进行CO_2甲烷化反应,综合效果最好,CH_4选择性达76.2%。

Microcapsule catalysts of Fe2O3@SiO2,Fe2O3@SiO2-PdO,PdO-Fe2O3@SiO2-1 and PdOFe2O3@SiO2-2 were prepared by impregnation and sol-gel method using Fe2O3,CTAB,TEOS,aqua ammonia and ammonium palladic chloride as raw materials,and the activity of catalysts were evaluated on high pressure fixed bed reaction device. The catalysts were characterized by XRD,H2-TPR,TEM and N2 physical adsorption. The results show that the micron grade capsule catalysts with SiO2 coating on theα-Fe2O3 surface were obtained,and the catalyst had a mesoporous structure. The surface area of the microcapsule catalyst was larger,and its catalytic performance for the CO2 methanation reaction was significantly improved,and the selectivity of the CH4 was significantly increased. Compared with Fe@SiO2-Pd catalyst,CH4 selectivity was greatly enhanced on Pd-Fe@SiO2-1 and Pd-Fe@SiO2-2 catalysts. This fully demonstrated the synergistic catalysis between Pd and Fe in the catalyst nucleus. It was disadvantage for CO2 methanation reaction if the SiO2 membrane in the catalyst was too thick. The effects of the CO2 methanation reaction was the best,and CH4 selectivity reached 76. 2% on Pd-Fe@SiO2-1 catalyst with moderate thickness film.