Insight into reaction path and mechanism of catalytic cracking of <i>n</i>-hexane in HZSM-5 zeolites

ZHAI Peng; ZHENG Jian; ZHANG Jin-yan; WANG Huan; QIN Yu-cai; LIU Hong-hai; SONG Li-juan

doi:10.1016/S1872-5813(21)60158-5

Volume 49 Issue 10

Oct. 2021

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Article Navigation > Journal of Fuel Chemistry and Technology > 2021 > 49(10): 1522-1530

ZHAI Peng, ZHENG Jian, ZHANG Jin-yan, WANG Huan, QIN Yu-cai, LIU Hong-hai, SONG Li-juan. Insight into reaction path and mechanism of catalytic cracking of n-hexane in HZSM-5 zeolites[J]. Journal of Fuel Chemistry and Technology, 2021, 49(10): 1522-1530. doi: 10.1016/S1872-5813(21)60158-5

Citation:

ZHAI Peng, ZHENG Jian, ZHANG Jin-yan, WANG Huan, QIN Yu-cai, LIU Hong-hai, SONG Li-juan. Insight into reaction path and mechanism of catalytic cracking of n-hexane in HZSM-5 zeolites[J]. Journal of Fuel Chemistry and Technology, 2021, 49(10): 1522-1530. doi: 10.1016/S1872-5813(21)60158-5

Citation:

ZHAI Peng, ZHENG Jian, ZHANG Jin-yan, WANG Huan, QIN Yu-cai, LIU Hong-hai, SONG Li-juan. Insight into reaction path and mechanism of catalytic cracking of n-hexane in HZSM-5 zeolites[J]. Journal of Fuel Chemistry and Technology, 2021, 49(10): 1522-1530. doi: 10.1016/S1872-5813(21)60158-5

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Insight into reaction path and mechanism of catalytic cracking of n-hexane in HZSM-5 zeolites

doi: 10.1016/S1872-5813(21)60158-5

ZHAI Peng^1
,,
ZHENG Jian²,
ZHANG Jin-yan¹,
WANG Huan^{1, 2},
QIN Yu-cai^{1
,
,},
LIU Hong-hai^{3
,
,},
SONG Li-juan^{1, 2}

1.
Key Laboratory of Petrochemical Catalytic Science and Technology, Liaoning Petrochemical University, Fushun 113001, China
2.
College of Chemistry and Chemical Engineering, China University of Petroleum (East China), Qingdao 266555, China
3.
PetroChina Petrochemical Research Institute Lanzhou Petrochemical Research Centre, Lanzhou 730060, China

Funds: The project was supported by National Natural Science Foundation of China (21902068, U20A20120), the Sponsored by CNPC Innovation Found (2020D-5007-0401), Scientific Research Project of Education Department of Liaoning Province (L2019035)

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Author Bio:
1064730774@qq.com
Corresponding author: Tel: 15841344639, 13893263271, E-mail: qycgryx@163.com; liuhonghai@petrochina.com.cn
Received Date: 2021-03-15
Rev Recd Date: 2021-04-10

Available Online: 2021-09-13

Publish Date: 2021-10-30

Abstract

Abstract

The n-hexane was used as a model compound to study the catalytic cracking behavior of light hydrocarbon in HZSM-5 zeolites, and the law of product selectivity of real acid-catalyzed reaction was investigated by analyzing the product distributions. The results showed that no pyrolysis reaction was found at 300 ℃. Only the acid catalytic reaction took place by the mechanism of carbocation, whose activity was positively correlated to the amount of Brønsted (B) acid sites. The selectivity of ethane, ethylene and propane was negatively correlated, while that of propylene was positively correlated with the Si/Al ratios and catalyst to oil ratios, suggesting that low acid density might be more favorable for monomolecular cracking reactions. It was worth nothing that the total selectivity of C₄ products was much higher than that of C₂ products. Combined with the quantum chemistry calculation results, it could be confirmed that the super-stability of ${{\rm{C}}_{{2}}}{\rm{H}}_{{5}}^ {{+}}$ carbenium ion from the monomolecular cracking of n-hexane made it difficult to produce ethylene and ethane through hydrogen transfer reaction. It’s easier to form a C₈ carbenium ion (${{\rm{C}}_{{8}}}{\rm{H}}_{{{19}}}^ {{+}}$) with another n-hexane molecule, and then to generate more C₄ products. These results revealed the nature of the low selectivity of ethylene in light hydrocarbon catalytic cracking products. It could be concluded that the product selectivity of catalytic cracking of light hydrocarbons could be modulated by controlling reaction paths depending on the catalyst acid properties and the catalyst to oil ratios. This work will provide important theoretical support for the catalyst design and process development of naphtha catalytic cracking.
- HZSM-5,
- catalytic cracking,
- Brønsted acid sites,
- selectivity,
- carbenium ion

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References(29)

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