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以ZSM-5分子筛为载体,通过等体积浸渍法制备了Co/ZSM-5系列催化剂,用于费托合成反应一步法制汽油馏分烃(C_5~C_(11)烷烃)。考察了不同硅铝比(Si O_2/Al_2O_3=25,38,50,80和200)的ZSM-5分子筛对Co/ZSM-5催化剂费托合成汽油馏分选择性的影响。采用氮气物理吸附-脱附、X射线衍射、氢气程序升温还原(H_2-TPR)和氨气程序升温脱附(NH_3-TPD)等手段对载体和催化剂进行了表征,并在高压固定床反应器上对催化剂的费托合成催化性能进行了测试。结果表明,对比Co/ZSM-5(Si O_2/Al_2O_3=25,38,50和80)催化剂,Co/ZSM-5(Si O_2/Al_2O_3=200)催化剂表现出最高的汽油馏分烃类选择性,高达52.8%,这主要归功于Co/ZSM-5(Si O_2/Al_2O_3=200)催化剂上较小钴颗粒尺寸、较优的还原性能以及适量弱酸位的协同作用。分子筛的酸性为催化剂的加氢裂解转化提供活性位,促进重质烃产物发生裂解和异构等二次反应,较小的钴颗粒尺寸和较优的还原性能有利于提高C_5~+烃选择性。
The ZSM-5 molecular sieve was used as a carrier to prepare Co / ZSM-5 series catalysts by the same volume impregnation method. The catalyst was used for Fischer-Tropsch synthesis of one-step gasoline paraffin (C_5 ~ C_11) alkanes. The effects of ZSM-5 molecular sieves with different Si / Al ratios (Si O 2 / Al 2 O 3 = 25, 38, 50, 80 and 200) on the selectivity of the Fischer- The supports and catalysts were characterized by physical adsorption-desorption of nitrogen, X-ray diffraction, temperature-programmed reduction of hydrogen (H 2 -TPR) and ammonia-temperature programmed desorption (NH 3 -TPD) On the catalyst Fischer-Tropsch synthesis catalytic properties were tested. The results show that the catalyst of Co / ZSM-5 (Si O 2 / Al 2 O 3 = 200) shows the highest hydrocarbon selectivity for gasoline fractions compared to Co / ZSM-5 catalysts, Si 2 O 3 / Al 2 O 3 = 25, Up to 52.8%, mainly due to the synergetic effect of the smaller cobalt particle size, the better reduction performance and the moderate amount of weak acid sites on the Co / ZSM-5 (Si O 2 / Al 2 O 3 = 200) catalyst. The acidity of the molecular sieve provides the active site for the hydrocracking of the catalyst to promote the secondary reaction such as cracking and isomerization of the heavy hydrocarbon product. The smaller cobalt particle size and the better reduction performance are beneficial to increase the C_5 ~ + hydrocarbon selectivity .