具有镁铝尖晶石壳层镍基甲烷化催化剂制备及性能

Preparation of Ni-based methanation catalysts with magnesia-alumina spinel shell and their catalytic performances

通过用葡萄糖络合镁溶液浸渍球磨为纳米颗粒的拟薄水铝石的方法制得具有镁铝尖晶石壳层的Mg Al2O4@γ-Al2O3复合载体,然后以硝酸镍作为催化活性组分,镧、钴、锰的硝酸盐作为助剂,采用浸渍法制备了一系列具有镁铝尖晶石壳层的镍基催化剂。利用XRD和BET对催化剂进行了表征,并在固定床反应器中评价了催化剂的合成气甲烷化反应性能和长期稳定性,考察了镍含量、不同助剂等对催化剂结构和性能的影响。结果表明,制备Mg Al2O4@γ-Al2O3复合载体中,一定的镁含量会在γ-Al2O3颗粒表面形成Mg Al2O4壳层,镁含量太高时还会出现Mg O物相。在Ni O质量分数为7.5%~44.8%的范围内,催化剂表现出了很好的催化性能,添加镧助剂的催化剂具有更高的催化活性,其中11.2%Ni O-2.6%La2O3/Mg Al2O4@γ-Al2O3催化剂在常压和240℃条件下,CO转化率为98.9%,CH4选择性为97.0%,并且在260℃~700℃反应温度范围内,经过多次升、降反应温度和1150h的长期稳定性测试,表现出了很好的稳定性和耐热冲击性能。

A composite support MgAl2O4@-Al2O3 with a spinel MgAl2O4 shell was prepared by means of impregnating the milled pseudo-boehmite nano particles with the solution of glucose-magnesium complex, then it was used to prepare a series of Ni-based catalysts by impregnating it firstly with a nitrate solution of lanthanum, cobalt or manganese, then with a solution of nickel nitrate. The prepared catalysts were characterized by XRD and BET, and their catalytic performances and stability for syngas methanation reaction were evaluated in a fixed bed reactor. The effects of Ni content and promoters on the structure and performance of the catalysts were investigated. The results showed that in the eomposite support MgAl2O4@γ-Al2O3 a spinel MgALO4 shell around the γ-Al2O3 core could be formed when Mg content was suitable and the MgO phase could appear when Mg content was higher. The catalysts containing NiO from 7.5% to 44.8% by masss showed better catalytic performance, especially the catalyst 11.2%NlO-2.6% La203/MgAl2O4@γ-Al2O3 exhibited the best, over it the CO conversion and CHa selectivity could reach 98.9% and 97.0%, respeetively, under 240℃ and atmospheric pressure, and it showed good stability and heat shock resistance during the 1150 hours time-on-stream while reaction temperature rose and fell many times in the range of 260-700℃.