多级孔ZSM-5和<i>β</i>分子筛催化裂解正庚烷增产烯烃

欧苏慧; 潘小燕; 郑一凡; 刘纪昌; 宋佳; 段泽康

doi:10.14135/j.cnki.1006-3080.20210309001

多级孔ZSM-5和β分子筛催化裂解正庚烷增产烯烃

doi: 10.14135/j.cnki.1006-3080.20210309001

1.
华东理工大学化工学院，上海 200237
2.
山东京博石油化工有限公司，山东博兴 256500

详细信息

作者简介:
欧苏慧（1995-），硕士生，主要研究方向为催化裂解制低碳烯烃。E-mail：837329595@qq.com

通讯作者:
刘纪昌，E-mail：liujc@ecust.edu.cn

中图分类号: TE624
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- 被引次数: 0
出版历程
- 收稿日期: 2021-03-09
- 网络出版日期: 2021-07-12
- 刊出日期: 2022-06-29

Catalytic Cracking of n-Heptane by Hierarchical ZSM-5 and β Zeolites to Increase Yield of Olefins

1.
School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
2.
Shandong Chambroad Petrochemicals Co. Ltd, Boxing 256500, Shandong, China

摘要

摘要: 采用溶剂挥发自组装法和取向连接生长法制备了多级孔结构的10元环ZSM（Zeolite Socony Mobil)-5分子筛和12元环β分子筛，并考察了其催化裂解正庚烷的性能。引入介孔后分子筛酸强度更低且扩散能力更强，能够有效减少氢转移的副反应发生，多级孔ZSM-5-HTS（其中HTS为十六烷基三甲氧基硅烷）分子筛与β-HTS分子筛可分别将低碳烯烃收率提高16.78%和21.63%。多级孔β-HTS分子筛在优化反应条件下，双烯收率为50.29%，比多级孔ZSM-5-HTS分子筛高10.37%，且丙烯选择性可达32.68%，丙烯选择性较高归因于其独特的三维12元环孔道结构和较好的介孔与微孔连通性。
- 正庚烷 /
- 烯烃 /
- 催化裂解 /
- 溶剂挥发自组装 /
- 多级孔分子筛 /
- β分子筛 /
- ZSM-5
Abstract: Hierarchical ZSM-5 and β zeolites were synthesized by solvent evaporation induced self-assembly and oriented attachment growth methods, respectively, and their catalytic properties in n-heptane cracking were assessed to determine the impact of hierarchical structure over catalysis. The catalytic cracking of n-heptane to generate light olefins was evaluated and the results demonstrated that high yields of light olefins could be attained on hierarchical zeolites, despite of lower conversions due to the reduction of acid site number. The hierarchical ZSM-5-HTS and β could increase the yield of light olefins by 16.78% and 21.63%, respectively. Hierarchical β-HTS zeolite outperformed hierarchical ZSM-5-HTS under identical operation conditions. Under optimized 680 ℃ and space velocity of 10 h⁻¹, the yield of light olefins by hierarchical β-HTS reached 50.29%, and simultaneously the highest propylene selectivity of 32.68% was achieved. The superior catalytic performance was attributed to a combined effect of reduced acid site density and enhanced diffusion property. The higher propylene selectivity was attributed to the unique large micropore size, better mesopore connectivity and decreased acid site density of hierarchical β-HTS.
- n-heptane /
- olefin /
- catalytic cracking /
- solvent evaporation induced self-assembly /
- hierarchical zeolite /
- β zeolite /
- ZSM-5

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图 1 多级孔β-HTS分子筛、普通β分子筛(a)和多级孔ZSM-5-HTS分子筛、普通ZSM-5分子筛(b)的XRD谱图

Figure 1. XRD patterns of hierarchical β-HTS zeolite, conventional β zeolite (a) and ZSM-5-HTS zeolite, conventional ZSM-5 zeolite (b)

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图 2 不同分子筛的SEM照片

Figure 2. SEM micrographs of different zeolites

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图 3 多级孔β-HTS分子筛、普通β分子筛(a)和多级孔ZSM-5-HTS分子筛、普通ZSM-5分子筛(b)的N₂吸附-脱附等温线

Figure 3. N₂ adsorption-desorption isotherms of hierarchical β-HTS, conventional β zeolite (a) and hierarchical ZSM-5-HTS, conventional ZSM-5 zeolite (b)

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图 4 多级孔β-HTS分子筛、传统β分子筛(a)和多级孔ZSM-5-HTS分子筛、传统ZSM-5分子筛(b)的孔径分布图

Figure 4. Pore-size distribution of hierarchical β-HTS, conventional β zeolite (a) and hierachical ZSM-5-HTS, conventional ZSM-5 zeolite (b)

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图 5 不同分子筛的NH₃-TPD谱图

Figure 5. NH₃-TPD spectra of different zeolites

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图 6 不同分子筛在200 ℃ (a, b)和350 ℃ (c, d)脱气后的吡啶红外光谱图

Figure 6. Py-IR spectra of different zeolites after desorbing at 200 ℃ (a, b) and 350 ℃(c, d)

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图 7 不同温度下正庚烷的转化率

Figure 7. Conversion of n-heptane at different temperature

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图 8 不同反应温度下低碳烯烃收率

Figure 8. Yield of light olefins at different temperatures

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图 9 不同分子筛得到催化产物中的烷烯比

Figure 9. $w\,{{\rm{C}}_{x}}{\rm{H}}{_{2x+2}} /w\,{{\rm{C}}_{x}}{\rm{H}}_{2x}$ obtained by different zeolites

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图 10 不同空速下正庚烷的转化率

Figure 10. Conversion of n-heptane at different WHSV

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图 11 不同空速下的低碳烯烃收率

Figure 11. Yield of light olefins at different WHSV

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图 12 不同分子筛在正庚烷裂解中的稳定性

Figure 12. Stability of different zeolites in n-heptane cracking

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图 13 正庚烷催化裂解反应进行20 h后的微孔和多级孔分子筛积碳量的热重曲线

Figure 13. TG of carbon deposition on microporous and hierarchical molecular sieves after n-heptane catalytic cracking reaction for 20 h

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表 1 不同分子筛的孔结构参数

Table 1. Pore structure parameters of different zeolites

Sample	n(Si)/n(Al)¹⁾	S_BET/(m²·g⁻¹)	S_mic/(m²·g⁻¹)	V_mic/(cm³·g⁻¹)	V_meso/(cm³·g⁻¹)	V_total/(cm³·g⁻¹)	D/nm
β-HTS	33.12	554.23	361.00	0.19	0.70	1.00	15.72
β	24.21	501.54	380.31	0.23	0.11	0.34	3.41
ZSM-5-HTS	39.04	377.00	251.54	0.13	0.27	0.40	8.24
ZSM-5	24.57	244.51	224.60	0.12	0.02	0.14	2.42
1) Determined by ICP-AES measurement; S_BET—BET Specific surface area; S_mic—Micropores specific surface area; V_mic—Microporous volume; V_meso—Mesopore volume; V_total—Total pore volume

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表 2 不同分子筛的酸性Py-IR结果

Table 2. Py-IR measurements of acidity for different zeolites

Samples	c/(10⁻⁴mol·g⁻¹)
Samples	T	TL	TB	SB	SL
ZSM-5	3.65	0.22	3.43	3.19	0.18
ZSM-5-HTS	3.40	2.13	1.27	1.09	0.85
β	4.39	3.31	1.08	0.84	1.26
β-HTS	1.59	1.09	0.50	0.43	0.23
T—Total acid; TL—Total L acid; TB—Total B acid; SL—Strong L acid; SB—Strong B acid

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