Acid strength controlled reaction pathways for the catalytic cracking of 1-butene to propene over ZSM-5

作者：Lin, Longfei; Qiu, Caifeng; Zhuo, Zuoxi; Zhang, Dawei; Zhao, Shufang; Wu, Haihong; Liu, Yueming^*; He, Mingyuan

来源：Journal of Catalysis, 2014, 309: 136-145.

DOI：10.1016/j.jcat.2013.09.011

• 1-Butene catalytic cracking
• ZSM-5
• Reaction pathways
• Acid strength
• Propene

The influence of the acid strength of P-modified and of HNO3-dealuminated HZSM-5 on the selectivity for the formation of propene was examined in the conversion of 1-butene. Under the appropriate amount of total acid sites, the reaction pathways of dimerization cracking of 1-butene, which involve the mole ratio of propene to ethene (P/E ratio) and conversion of butenes, could be controlled by acid strength distribution. The results showed that the P/E ratio increased with the decreased amount of strong acid sites. For the ZSM-5 with relatively large amount of strong acid sites, the butene conversion was improved via increasing reaction temperature. In contrast, the butene conversion decreased with the increased reaction temperature over ZSM-5 bearing small amount of strong acid sites. It was because the activation energies of different reaction pathways were influenced by acid strength to a different extent. Strong acid sites could promote the pathways I (2C(4)(=) -> C-8(I) -> 2C(4)(=)) and II (2C(4)(=) -> C-8(II) -> C-2(=) C-6(=)) favorably, while weak acid sites preferred the pathway III (2C(4)(=) -> C-8(III) -> C-3(=) C-5(=)) since pathway III underwent some energetically favorable forms (tertiary-secondary, secondary-secondary) of cracking (C-8(I), C-8(II), C-8(III), represent octyl carbenium ions). According to designing acid strength distribution on ZSM-5, P/E ratio and selectivity of propene could be significantly improved.

• 出版日期2014-1
• 单位华东师范大学