乙醇蒸气预处理Cr基催化剂对丙烷脱氢性能的影响

doi:10.1016/S1872-2067(15)61042-7

摘要/Abstract

摘要：

丙烯是仅次于乙烯的重要有机化工基础原料, 广泛应用于生产聚丙烯、丙烯醛、丙烯酸、甘油、异丙醇、聚丙烯氰、丁辛醇等化工产品. 近年来, 随着市场经济的发展, 丙烯下游产品的需求量迅速上涨, 极大地促进了全球对丙烯的需求. 负载型氧化基催化剂因其良好的催化性能和低廉的生产成本而被广泛应用于低碳烷烃脱氢反应中, Catofin, Linde 及 FBD 工艺使用的就是 Cr₂O₃/γ-Al₂O₃催化剂. 丙烷脱氢过程中, 担载型氧化铬催化剂 Cr 物种的价态、配位结构及与载体之间的相互作用会影响其催化性能. 催化反应过程中, 丙烷分子吸附在 Cr-O 上进行活化反应, 因而研究清楚催化剂的活性物种是非常重要的. 综合文献, 一部分研究者认为 Cr⁶⁺为反应的活性中心, 在反应初期与丙烷接触立即被还原为活性比较弱的 Cr³⁺. 随着原位表征技术的发展, 一些研究者认为, 八面体配位结构的 Cr³⁺物种为催化反应的活性中心, 四面体配位结构的 Cr⁶⁺仅仅是 Cr³⁺活性物种的前驱体, 而且 Cr⁶⁺并没有被发现具有催化活性. 但何种 Cr 物种是脱氢活性中心, 至今仍没有一致结论, 这是值得继续关注和解决的问题. 同时, 浸渍法制备催化剂的过程中, 金属前驱体、浸渍溶剂、干燥时间、干燥温度及焙烧时间和温度等因素会影响所制备催化剂的催化活性. 我们采用等体积浸渍法制备催化剂, 并用饱和乙醇蒸气对其进行预处理, 以丙烷脱氢为探针反应研究了预处理对催化剂脱氢反应性能的影响, 采用 X射线衍射(XRD)、透射电镜(TEM)、程序升温还原(H₂-TPR)、X射线光电子能谱(XPS) 和紫外-可见光谱 (UV-Vis) 等表征手段, 揭示催化反应的活性中心及反应机理.
在无氧脱氢反应中, 经过乙醇蒸气预处理的催化剂 CrH-Et 催化活性稍高于原始催化剂 CrH. 在二氧化碳参与的反应中, 催化剂 CrH-Et 催化活性远远高于 CrH. 当 C₃H₈:CO₂:He = 1:5:4 时达到最佳效果, CrH-Et 的丙烷转化率为 41.4%, 丙烯选择性为 84.8%, 同样条件下 CrH 的催化活性和丙烯选择性分别为 28.0% 和 85.9%. 但是乙醇作为浸渍溶剂, 对催化剂并没有促进作用.
XRD 和 TEM 结果表明, Cr 均匀分散在载体表面, Cr 粒子簇的大小并不影响催化剂的催化活性. H₂-TPR, XPS 和 UV-Vis 结果说明, 经过乙醇蒸气预处理后催化剂中的 Cr⁶⁺被还原成低价 Cr, 因而可以证明 Cr⁶⁺不是催化剂的活性中心. Cr³⁺作为活性中心而存在, Cr⁶⁺仅作为活性组分的前驱体而存在. 而在反应过程中, Cr³⁺容易被反应中生成的 H₂还原成非活性组分. 相对于催化剂 CrH, 经过乙醇蒸气预处理的催化剂 (CrH-Et) 上部分还原后的低价 Cr 更容易被 CO₂重新氧化成 Cr⁶⁺. 即在反应过程中, CrH-Et 能保持相对 CrH 更多的活性组分, 因而保持更高的催化活性.

关键词: 丙烷, 脱氢, CrO_x/SiO₂催化剂, 乙醇蒸气预处理, 二氧化碳

Abstract:

The effects of ethanol vapor pretreatment on the performance of CrO_x/SiO₂ catalysts during the dehydrogenation of propane to propylene were studied with and without the presence of CO₂. The catalyst pretreated with ethanol vapor exhibited better catalytic activity than the pristine CrO_x/SiO₂, generating 41.4% propane conversion and 84.8% propylene selectivity. The various catalyst samples prepared were characterized by X-ray diffraction, transmission electron microscopy, temperature-programmed reduction, X-ray photoelectron spectroscopy and reflectance UV-Vis spectroscopy. The data show that coordinative Cr³⁺ species represent the active sites during the dehydrogenation of propane and that these species serve as precursors for the generation of Cr³⁺. Cr³⁺ is reduced during the reaction, leading to a decrease in catalytic activity. Following ethanol vapor pretreatment, the reduced CrO_x in the catalyst is readily re-oxidized to Cr⁶⁺ by CO₂. The pretreated catalyst thus exhibits high activity during the propane dehydrogenation reaction by maintaining the active Cr³⁺ states.

Key words: Propane, Dehydrogenation, CrO_x/SiO₂ catalyst, Ethanol vapor pretreatment, Carbon dioxide

李利娜, 朱文良, 石磊, 刘勇, 刘红超, 倪友明, 刘世平, 周慧, 刘中民. 乙醇蒸气预处理Cr基催化剂对丙烷脱氢性能的影响[J]. 催化学报, 2016, 37(3): 359-366.

Lina Li, Wenliang Zhu, Lei Shi, Yong Liu, Hongchao Liu, Youming Ni, Shiping Liu, Hui Zhou, Zhongmin Liu. The effect of ethanol on the performance of CrO_x/SiO₂ catalysts during propane dehydrogenation[J]. Chinese Journal of Catalysis, 2016, 37(3): 359-366.

×
扫码分享

导出引用管理器 EndNote|Ris|BibTeX

链接本文: https://www.cjcatal.com/CN/10.1016/S1872-2067(15)61042-7

https://www.cjcatal.com/CN/Y2016/V37/I3/359

参考文献

[1] M. M. Bettahar, G. Costentin, L. Savary, J. C. Lavalley, Appl. Catal. A, 1996, 145, 1-48.
[2] R. Grabowski, Catal. Rev. Sci. Eng., 2006, 48, 199-268.
[3] P. R. Pujado, B. V. Vora, Hydrocarbon Process., 1990, 69, 65-70.
[4] J. J. H. B. Sattler, J. Ruiz-Martinez, E. Santillan-Jimenez, B. M. Weckhuysen, Chem. Rev., 2014, 114, 10613-10653.
[5] B. Schimmoeller, Y. J. Jiang, S. E. Pratsinis, A. Baiker, J. Catal., 2010, 274, 64-75.
[6] F. Cavani, N. Ballarini, A. Cericola, Catal. Today, 2007, 127, 113-131.
[7] E. V. Kondratenko, A. Brückner, J. Catal., 2010, 274, 111-116.
[8] T. Kamegawa, J. Morishima, M. Matsuoka, J. M. Thomas, M. Anpo. J. Phys. Chem. C, 2007, 111, 1076-1078.
[9] Y. Sakurai, T. Suzaki, N. O. Ikenaga. T. Suzuki, Appl. Catal. A, 2000, 192, 281-288.
[10] I. Takahara, W. C. Chang, N. Mimura. M. Saito, Catal. Today, 1998, 45, 55-59.
[11] Y. Ohishi, T. Kawabata, T. Shishido, K. Takaki, Q. H. Zhang, Y. Wang, K. Takehira, J. Mol. Catal. A, 2005, 230, 49-58.
[12] X. Ge, H. Zou, J. Wang, J. Y. Shen, React. Kinet. Catal. Lett., 2005, 85, 253-260.
[13] P. Michorczyk, J. Ogonowski, P. Ku?trowski and L. Chmielarz, Appl. Catal. A, 2008, 349, 62-69.
[14] S. A. Al-Ghamdi, H. I. de Lasa, Fuel, 2014, 128, 120-140.
[15] E. V. Kondratenko, M. Yu. Sinev, Appl. Catal. A, 2007, 325, 353-361.
[16] B. Y. Jibril, S. Ahmed, Catal. Commun., 2006, 7, 990-996.
[17] M. Chen, J. Xu, Y. M. Liu, Y. Cao, H. Y. He, J. H. Zhuang, K. N. Fan, Catal. Lett., 2008, 124, 369-375.
[18] Y. J. Ren, F. Zhang, W. M. Hua, Y. H. Yue, Z. Gao, Catal. Today, 2009, 148, 316-322.
[19] O. V. Krylov, A. Kh. Mamedov, S. R. Mirzabekova, Ind. Eng. Chem. Res., 1995, 34, 474-482.
[20] C. Trionfetti, S. Crapanzano, I. V. Babich, K. Seshan, L. Lefferts, Catal. Today, 2009, 145, 19-26.
[21] T. Shishido, K. Shimamura, K. Teramura, T. Tanaka, Catal. Today, 2012, 185, 151-156.
[22] R. X. Wu, P. F. Xie, Y. H. Cheng, Y. H. Yue, S. Y. Gu, W. M. Yang, C. X. Miao, W. M. Hua, Z. Gao, Catal. Commun., 2013, 39, 20-23.
[23] D. Yun, J. Baek, Y. Choi, W. Kim, H. J. Lee, J. Yi, ChemCatChem, 2012, 4, 1952-1959.
[24] E. Heracleous, M. Machli, A. A. Lemonidou and I. A. Vasalos, J. Mol. Catal. A, 2005, 232, 29-39.
[25] F. E. Frey, W. F. Huppke, Ind. Eng. Chem., 1932, 25, 54-59.
[26] Y. Wang, Y. Ohishi, T. Shishido, Q. H. Zhang, W. Yang, Q. Guo, H. L. Wan, K. Takehira, J. Catal., 2003, 220, 347-357.
[27] P. Michorczyk, J. Ogonowski, K. Zeńczak, J. Mol. Catal. A, 2011, 349, 1-12.
[28] M. S. Kumar, N. Hammer, M. Ronning, A. Holmen, D. Chen, J. C. Walmsley, G. Öye, J. Catal., 2009, 261, 116-128.
[29] J. Baek, H. J. Yun, D. Yun, Y. Choi, J. Yi, ACS Catal., 2012, 2, 1893-1903.
[30] F. T. Zangeneh, S. Mehrazma, S. Sahebdelfar, Fuel Process. Technol., 2013, 109, 118-123.
[31] E. Skwarek, S. Khalameida, W. Janusz, V. Sydorchuk, N. Konovalova, V. Zazhigalov, J. Skubiszewska-Zi?ba, R. Leboda, J. Therm. Anal. Calorim., 2011, 106, 881-894.
[32] Yu. A. Agafonov, N. A. Gaidai and A. L. Lapidus, Russ. Chem. Bull., 2014, 63, 381-388.
[33] Y. N. Sun, Y. M. Wu, L. Tao, H. H. Shan, G. W. Wang and C. Y. Li, J. Mol. Catal. A, 2015, 397, 120-126.
[34] S. M. K. Airaksinen, A. O. I. Krause, Ind. Eng. Chem. Res., 2005, 44, 3862-3868.
[35] P. Michorczyk, J. Ogonowski, K. Zeńczak, J. Mol. Catal. A, 2011, 349, 1-12.
[36] A. Hakuli, M. E. Harlin, L. B. Backman, A. O. I. Krause, J. Catal., 1999, 184, 349-356.
[37] B. M. Weckhuysen, A. A. Verberckmoes, A. R. De Baets, R. A. Schoonheydt, J. Catal., 1997, 166, 160-171.
[38] M. S. Kumar, N. Hammer, M. Rönning, A. Holmen, D. Chen, J. C. Walmsley, G. Öye, J. Catal., 2009, 261, 116-128.
[39] K. Takehira, Y. Ohishi, T. Shishido, T. Kawabata, K. Takaki, Q. H. Zhang and Y. Wang, J. Catal., 2004, 224, 404-416.