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

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

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、29 Si 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益,H2和CO体积比为2和GHSV=1000 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；Co3 O4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。

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 Co3 O4 crystallite size and the decrease of un-reducible cobalt compound after hydrophobic modification, CH4 selectivity decreased and C5＋ selectivity increased.