Acid Strength Controlled Reaction Pathways for the Catalytic Cracking of 1-Pentene to Propene over ZSM-5
Acid Strength Controlled Reaction Pathways for the Catalytic Cracking of 1-Pentene to Propene over ZSM-5
复制标题
ZSM-5 催化裂解 1-戊烯制丙烯的酸强度控制反应路径
DOI：
10.1021/cs501967r
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发表时间：
2015-07-01
期刊：
影响因子：
12.9
通讯作者：
He, Ming Y.
中科院分区：
文献类型：
--
作者：
Lin, Long F.;Zhao, Shu F.;He, Ming Y.
评价了酸强度对1-戊烯转化率的丙烯选择性的影响。对于1-戊烯的催化裂解，主要反应途径和丙烯/乙烯的摩尔比（P/E比）由酸强度控制，总酸中心的量合适。结果表明，P/E比随强酸中心数量的减少而增加，这是因为酸强度对各个反应途径的活化能有不同程度的影响。强酸性位点可促进途径1'（C-5（2-）-> C-2（2-）+ C-3（2-））和途径II'-1（C-6（2-）-> C-2（2-）+ C-4（2-）），而弱酸性位点偏好途径II ′（2C（5）（2-）-> C-10（+）-> C-4（2-）+ C-6（2-））和途径II ′-2（C-6（2-）-> 2C（3）（2-）），因为途径II'和II'-2经历了碳正离子中间体的一些能量上有利的途径（叔-仲、仲-仲）。通过改变ZSM-5分子筛上的酸强度分布，可以显著提高丙烯的选择性和P/E比，这对改进该工艺具有重要指导意义。此外，由于C4（2-）和C5（2-）催化裂化可同时生成戊烯和丁烯，我们还设计了丁烯和戊烯共转化的耦合工艺。该耦合工艺为C4和C5烯烃裂解制丙烯提供了一种很有前途的解决方案。
The influence of acid strength was evaluated toward the selectivity to propene on conversion of 1-pentene. For the catalytic cracking of 1-pentene, the main reaction pathways and the molar ratio of propene to ethene (P/E ratio) were controlled by acid strength with the appropriate amount of total acid sites. The results showed that the P/E ratio increased with decreasing amounts of strong acid sites, since the activation energies of individual reaction pathways were influenced by acid strength to a different extent. Strong acid sites could promote pathway 1' (C-5(2-) -> C-2(2-) + C-3(2-)) and pathway II'-1 (C-6(2-) -> C-2(2-) + C-4(2-)), while weak acid sites preferred pathway II' (2C(5)(2-) -> C-10(+) -> C-4(2-) + C-6(2-)) and pathway II'-2 (C-6(2-) -> 2C(3)(2-)), since pathways II' and II'-2 underwent some energetically favorable routes (tertiary-secondary, secondary-secondary) of carbenium ion intermediates. By manipulation of the acid strength distribution on ZSM-5, the P/E ratio and selectivity of propene could be significantly improved, suggesting that this can provide an important guideline for improving such a process. In addition, we also designed a coupled process combing butene and pentene coconversion, as pentene and butene could be produced during C-4(2-) and C-5(2-) catalytic cracking. The coupled process could offer a promising solution to gain high selectivity of propene from C-4 and C-5 olefin cracking.