催化学报

催化学报 ›› 2017, Vol. 38 ›› Issue (1): 138-145.DOI: 10.1016/S1872-2067(16)62579-2

• 论文 • 上一篇    下一篇

磷改性纳米HZSM-5沸石水热稳定性及其对全馏分FCC汽油烯烃组分催化裂解反应的性能

赵云, 刘家旭, 熊光, 郭洪臣   

  1. 大连理工大学化工学院催化化学与工程系精细化工国家重点实验室
  • 收稿日期:2016-09-20 修回日期:2016-10-14 出版日期:2017-01-18 发布日期:2017-01-18
  • 通讯作者: Hongchen Guo,Tel./Fax.:+86-411-84986120;E-mail:hongchenguo@163.com
  • 基金资助:

    国家自然科学基金（21603023）和中国石油科技创新基金（2014D-5006-0501）.

Enhancing hydrothermal stability of nano-sized HZSM-5 zeolite by phosphorus modification for olefin catalytic cracking of full-range FCC gasoline

Yun Zhao, Jiaxu Liu, Guang Xiong, Hongchen Guo   

  1. Department of Catalytic Chemistry and Engineering & State Kay Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 110624, Liaoning, China
  • Received:2016-09-20 Revised:2016-10-14 Online:2017-01-18 Published:2017-01-18
  • Contact: Hongchen Guo,Tel./Fax.:+86-411-84986120;E-mail:hongchenguo@163.com
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21603023), and the PetroChina Innovation Foundation, China (2014D-5006-0501).

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摘要：

水热稳定性是决定沸石分子筛工业应用价值的重要影响因素.众所周知，沸石材料的水热稳定性主要受其拓扑机构及骨架硅铝组成的影响，但同时也受其晶粒尺寸的影响.纳米级HZSM-5沸石虽然具有优异的催化性能及抗积碳失活性能，但由于晶粒尺寸较小，导致其水热稳定性较差.如何提高纳米HZSM-5沸石的水热稳定性，使其能够在高苛刻度的水热环境下（如催化裂化过程，催化剂再生需在高于700℃的水热条件下进行）得到应用，是十分有意义的课题.已有研究表明，磷改性可以提高ZSM-5沸石的水热稳定性，但多集中于采用磷酸、磷酸氢二铵、磷酸二氢铵等无机磷化物进行改性，水热稳定性提高效果不能令人满意.我们研究组采用有机磷化合物磷酸三甲酯改性纳米HZSM-5沸石，在提高纳米HZSM-5沸石水热稳定性方面取得了较好的效果.采用X射线衍射（XRD）、氨气程序升温脱附（NH3-TPD）、氮气物理吸附、氨气吸附红外光谱等手段对改性沸石进行了表征.结果表明，采用磷酸三甲酯改性的纳米HZSM-5沸石水热稳定性得到明显提高，沸石经苛刻的高温水蒸气处理（800℃，4 h）后，在相对结晶度、孔结构、酸度的保留度方面具有较大提高，提高幅度明显高于无机磷化合物磷酸氢二铵改性的纳米HZSM-5沸石.
在上述研究基础上，我们采用固定床微反模拟流化床反应条件对磷改性纳米HZSM-5沸石上全馏分FCC汽油烯烃组分催化裂解反应进行了研究.结果表明，在反应温度540℃，剂/油比等于4，油剂接触时间约为4 s的条件下，全馏分FCC汽油在磷改性纳米HZSM-5沸石上经烯烃组分催化裂解反应后，油品烯烃含量（尤其是重烯烃）明显降低，生成了大量高附加值的C2-C4烯烃，同时油品中芳烃含量增加.与此同时，经烯烃组分裂解后的油品还呈现出辛烷值升高，硫含量降低的有利变化.可以看出，磷改性纳米HZSM-5沸石上全馏分FCC汽油烯烃组分催化裂解是解决FCC汽油烯烃含量高的一条有效途径，充分克服了现有FCC汽油加工工艺存在的一些缺陷，如S-zorb工艺功能单一、成本高；加氢脱硫工艺油品辛烷值损失大、氢耗高；以及OTA技术（本研究组之前的工作）烯烃转化率低、催化剂积碳失活快等缺陷.值得注意的是，磷酸三甲酯改性的纳米HZSM-5沸石在全馏分FCC汽油烯烃组分催化裂解反应性能方面，明显比磷酸二氢铵改性的纳米HZSM-5沸石表现优异.通过我们的研究可以认为，磷酸三甲酯改性将会为纳米HZSM-5沸石在高苛刻度水热条件下的应用提供更多的机会.

关键词: 水热稳定性, 纳米HZSM-5, 磷改性, 烯烃催化裂解, FCC汽油

Abstract:

In this study, phosphorus modification by trimethyl phosphate impregnation was employed to enhance the hydrothermal stability of nano-sized HZSM-5 zeolites. A parallel modification was studied by ammonium dihydrogen phosphate impregnation. The modified zeolites were subjected to steam treatment at 800℃ for 4 h (100% steam) and employed as catalysts for olefin catalytic cracking (OCC) of full-range fluid catalytic cracking (FCC) gasoline. X-ray diffraction, N2 physical adsorption and NH3 temperature-programmed desorption analysis indicated that, although signifi-cant improvements to the hydrothermal stability of nano-sized HZSM-5 zeolites can be observed when adopting both phosphorus modification strategies, impregnation with trimethyl phosphate displays further enhancement of the hydrothermal stability. This is because higher structural crys-tallinity is retained, larger specific surface areas/micropore volumes form, and there are greater numbers of surface acid sites. Reaction experiments conducted using a fixed-bed micro-reactor (catalyst/oil ratio=4, time on stream=4 s) showed OCC of full-range FCC gasoline-under a fluid-ized-bed reaction mode configuration-to be a viable solution for the olefin problem of FCC gaso-line. This reaction significantly decreased the olefin content in the full-range FCC gasoline feed, and specifically heavy-end olefins, by converting the olefins into value-added C2-C4 olefins and aromat-ics. At the same time, sulfide content of the gasoline decreased via a non-hydrodesulfurization pro-cess. Nano-sized HZSM-5 zeolites modified with trimethyl phosphate exhibited enhanced catalytic performance for OCC of full-range FCC gasoline.

Key words: Hydrothermal stability, Nano-sized HZSM-5, Phosphorus modification, Olefin catalytic cracking, FCC gasoline