SBA-15的疏水改性及其对钴基催化剂费-托合成催化性能的影响

利用甲硅烷基化作用制得了不同疏水基团(甲基、二甲基和三甲基)改性SBA-15载体,采用等体积浸渍法制备了质量分数为5%的一系列负载型钴催化剂。结合BET、FT-IR、29Si CP MAS NMR、XRD和H2-TPR等表征手段,考察了SBA-15疏水改性对钴基催化剂物相结构、还原行为以及费-托合成催化性能的影响。催化剂在固定床反应器中在p=2.0 MPa,t=200~250℃,H2和CO体积比为2和GHSV=1 000 h-1的条件下进行评价。结果表明,相对于未改性SBA-15负载钴催化剂,疏水基团改性SBA-15负载钴催化剂的还原度增加,CO转化率提高;Co3O4晶粒粒径增大,难还原钴物种减少,CH4选择性降低,C5+烃选择性增加。

Hydrophobic modification of SBA-15 and its influence on the properties of cobalt-based catalysts for Fischer-Tropsch synthesis

SBA-15 supports modified by different hydrophobic reagents (methyltriethoxysilane, dimethyldiethoxysilane and chlorotrimethylsilane) were prepared before the impregnation of cobalt precursor. The effects of hydrophobic modification on the crystallite structure and the reduction behaviors were studied by BET, FT-IR, ²⁹Si CP MAS NMR, XRD, and H₂-TPR. Fischer-Tropsch (F-T) synthesis performances were evaluated in a fixed-bed reactor at 2.0 MPa, 200~250 ℃, H₂/CO (volume ratio)=2, and GHSV=1 000 h^-1. The result indicated that hydrophobic modification led to the increase in reduction degree of the supported cobalt, resulting in the increase of CO conversion of cobalt catalysts for F-T synthesis. Moreover, due to the increase of Co₃O₄ crystallite size and the decrease of un-reducible cobalt compound after hydrophobic modification, CH₄ selectivity decreased and C₅₊ selectivity increased.