Investigation of the interactions for the 1-hexene oligomerization and the catalytic cracking reactions
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摘要: 分别以1,3,5-三异丙苯和正辛烷为不同分子尺寸催化裂解原料,以1-己烯为叠合原料,评估了合成的多级孔ZSM-5分子筛催化剂上催化裂化反应和烯烃叠合反应的耦合机制。模型化合物催化裂解反应结果表明,在合成的多级孔ZSM-5分子筛上不同尺寸分子裂解性能受到抑制,1,3,5-TIPB裂解能力下降,正辛烷裂解初始转化率由70%降低到20%。而多级孔ZSM-5分子筛的1-己烯叠合催化活性得到提升,高于工业ZSM-5分子筛,叠合产物以二聚物为主。分子筛中强酸酸量的降低可抑制催化裂化反应的进行,促进C6烯烃低聚为二聚物和三聚物(航空煤油的理想成分)的能力。因此,从抑制催化裂化的角度进行催化剂设计,可有效提高催化剂的烯烃叠合反应性能。Abstract: Using 1,3,5-triisopropylbenzene (1,3,5-TIPB) and n-octane as the catalytic cracking feedstocks and 1-hexene as the oligomerization feedstock, the coupling mechanism of catalytic cracking reaction and olefin oligomerization reaction over the synthesized hierarchical ZSM-5 zeolite catalyst was evaluated. The results of catalytic cracking reaction of model compounds showed that the catalytic cracking performance of molecules with different sizes was inhibited on the synthesized hierarchical ZSM-5 zeolite. The cracking activity of 1,3,5-TIPB decreased, and the initial activity of n-octane reduced from 70% to 20%. However, enhanced 1-hexene oligomerization activity was observed over the hierarchical ZSM-5 zeolite, with dimer as the main product. The reduction of the strong acid sites in the zeolite can inhibit the catalytic cracking reaction and promote the oligomerization of C6 olefin into dimer and trimer (ideal components of jet fuel). Therefore, the designing of the catalyst from the perspective of inhibiting the activity of catalytic cracking can effectively improve the oligomerization performance of the catalyst.
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Key words:
- ZSM-5 /
- catalytic cracking /
- olefins oligomerization /
- jet fuel
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表 1 不同分子筛的孔结构参数
Table 1 Pore structure parameters of the different zeolites
Sample SBET
/(m2·g−1)Smic
/(m2·g−1)Sext
/(m2·g−1)vmic
/(cm3·g−1)vmeso
/(cm3·g−1)ZSM-5 (66) 302 242 59 0.10 0.04 ZSM-5 (252) 419 317 102 0.13 0.10 Commerial ZSM-5 442 401 41 0.16 0.05 表 2 不同样品NH3-TPD和Py-FTIR分峰拟合
Table 2 Peak fitting results of NH3-TPD and Py-FTIR for different samples
Sample Weak acid Strong acid Total peaks area Acidity/(μmol·g−1)[a] t/℃ peaks area t/℃ peaks area Brønsted Lewis ZSM-5 (66) 234 550 346 150 1050 68.53 73.43 430 350 ZSM-5 (252) 243 283 348 70 533 44.77 161.07 425 180 Commerial ZSM-5 239 1877 343 472 4149 − − 445 1800 [a] : Brønsted, Lewis acid calculation results at 150 ℃ -
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