六方氮化硼催化的乙烷丙烷共脱氢: 一种C-H键活化和机理研究的有效手段

doi:10.1016/S1872-2067(21)64042-1

摘要/Abstract

摘要：

乙烯、丙烯等低碳烯烃是化学工业重要的原料. 目前工业化的低碳烷烃脱氢制烯烃技术均为直接脱氢技术, 例如基于Pt-Sn催化剂的Oleflex工艺以及基于CrO_x的Catofin工艺. 相对于直接脱氢, 氧化脱氢具有不受热力学限制和避免积碳生成的优点. 然而, 传统的氧化脱氢催化剂(例如VO_x)难以抑制深度氧化副反应的发生, 因而使目标产物烯烃的收率受到抑制. 近年来, 六方氮化硼(h-BN)对低碳烷烃氧化脱氢过程表现出的高催化活性以及高烯烃选择性, 受到了国内外研究者的广泛关注. 同时, h-BN在烷烃反应级数以及表观活化能等方面表现出明显不同于其他烷烃脱氢催化剂的性质. 研究表明, 气相自由基反应对h-BN的催化活性具有重要贡献. 但是, 烷烃表观反应级数为2这一现象始终没有得到较好的解释. 本文针对该问题展开了探索.

本文以乙烷和丙烷的混合烷烃作为反应物, 研究h-BN催化的氧化脱氢过程. 结果表明, 丙烷的存在可以显著促进乙烷脱氢转化的速率, 在580 ºC下, 少量丙烷的引入可以使乙烷的转化率提高47%. 同时, 固定乙烷分压不变时, 乙烷氧化脱氢速率对丙烷分压的表观反应级数为1. 这说明烷烃表观的2级级数可以解耦为自由基引发剂和反应物两种角色. 原位红外光谱以及氧气反应级数的结果证明, 氧气主要通过表面吸附反应的形式与h-BN发生作用. 选取环氧丙烷作为指示分子, 采用程序升温氧化的实验方法对比丙烷和丙烯的性质, 结果发现丙烷生成的环氧丙烷约为丙烯的5倍, 说明由丙烷引发生成活性物种是h-BN体系中主要的夺氢氧化活性物种. 基于上述实验结果, 提出了基于气相自由基链反应的h-BN氧化脱氢机理, 并采用稳态近似推导了烷烃转化速率方程. 由速率方程拟合得到的动力学参数能够很好地匹配乙烷丙烷共氧化脱氢的实验结果, 可较好地解释本文以及先前工作中h-BN催化烷烃氧化脱氢中的实验现象. 综上, 本工作为硼基催化剂低碳烷烃氧化脱氢的机理认识提供了新的观点, 并发现乙烷丙烷共氧化脱氢是提升乙烷氧化脱氢性能的一种有效的新工艺.

关键词: 六方氮化硼, 氧化脱氢, 自由基链反应, 反应级数, C-H键活化

Abstract:

Hexagonal boron nitride (h-BN) is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes. Despite intense recent research effort, many aspects of the reaction mechanism, such as the observed supra-linear reaction order of alkanes, remain unresolved. In this work, we show that the introduction of a low concentration of propane in the feed of ethane oxidative dehydrogenation is able to enhance the C₂H₆ conversion by 47%, indicating a shared reaction intermediate in the activation of ethane and propane. The higher activity of propane makes it the dominant radical generator in the oxidative co-dehydrogenation of ethane and propane (ODEP). This unique feature of the ODEP renders propane an effective probe molecule to deconvolute the two roles of alkanes in the dehydrogenation chemistry, i.e., radical generator and substrate. Kinetic studies indicate that both the radical generation and the dehydrogenation pathways exhibit a first order kinetics toward the alkane partial pressure, leading to the observed second order kinetics of the overall oxidative dehydrogenation rate. With the steady-state approximation, a radical chain reaction mechanism capable of rationalizing observed reaction behaviors is proposed based on these insights. This work demonstrates the potential of ODEP as a strategy of both activating light alkanes in oxidative dehydrogenation on BN and mechanistic investigations.

Key words: Hexagonal boron nitride, Oxidative dehydrogenation, Radical chain reaction, Reaction order, C-H activation

田昊, 徐冰君. 六方氮化硼催化的乙烷丙烷共脱氢: 一种C-H键活化和机理研究的有效手段[J]. 催化学报, 2022, 43(8): 2173-2182.

Hao Tian, Bingjun Xu. Oxidative co-dehydrogenation of ethane and propane over h-BN as an effective means for C-H bond activation and mechanistic investigations[J]. Chinese Journal of Catalysis, 2022, 43(8): 2173-2182.

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https://www.cjcatal.com/CN/Y2022/V43/I8/2173

图/表 9

Fig. 1. ODE promoted by the addition of C3H8, 580 °C, pC2H6 = 0.25 atm, pO2 = 0.125 atm with N2 as balance, total gas flow = 40 mL·min-1. Red columns represent C2H6 conversion and blue columns represent the formation rate of C2H4.

Fig. 2. Catalytic performance of ODEP at 540 °C, (pC2H6 + pC3H8) = 0.25 atm, pO2 = 0.125 atm with N2 as balance, total gas flow = 40 mL·min-1. (a) product distribution and alkane conversion, carbon balances in the experiments are >98%. (b) Alkane conversion rates at different ratio of pC3H8/pC2H6.

Fig. 3. The influence of pC3H8 on the catalytic performance of ODEP and ODP with steam (pH2O = 1.8 kPa) at fixed pC2H6 = 0.25 atm at 520 °C. pO2 = 0.125 atm with N2 as balance, total gas flow = 40 mL·min-1. (a) Alkane conversion rates. (b) The reaction order of -rC3H8 with respect to pC3H8.

Fig. 4. Alkane conversion rates of ODEP with steam at 520 °C, (pC2H6 + pC3H8) = 0.25 atm, pO2 = 0.125 atm, pH2O = 1.8 kPa with N2 as balance, total gas flow = 40 mL·min-1.

Scheme 1. Radical chain reaction mechanism of ODH over BN. Green area: chain initiation; blue area: chain propagation; yellow area: chain termination.

Fig. 5. The MS signals in temperature programmed reaction. (a) On-line MS signals (m/z = 50-70 amu) of ODP over h-BN at different temperature. (b) The MS signals of temperature programmed reaction between C3H8 and O2 over h-BN. (c) The MS signals of temperature programmed reaction between C3H6 and O2 over h-BN. (d) The MS signal of propylene oxide (m/z = 58 amu) in temperature programmed reaction under C3H8 + O2 and C3H6 + O2. Temperature programmed reaction condition: pC3H8 or pC3H6 = 0.25 atm, pO2 = 0.125 atm with N2 as balance, total gas flow = 40 mL·min-1.

Fig. 6. Curve fitting to determine kinetic parameters of the “wet” ODEP at 520 °C. Fitted curves were obtained by global fitting of Eqs. (13)-(16) with alkane conversion rates measured with steam at 520 °C via minimizing the overall root of mean square error. The fitting results are shown in Table 1.

Table 1 Global fitting results of the “wet” ODEP at 520 °C.

k₂^’/mL·atm^-1	k₃^’/mL·atm^-1	k₄/mL·min^-1·atm^-1	k₅/mL·min^-1·atm^-1	Root of mean square error (RMSE)	R²
1.042	5.125	0.633	1.562	0.0204	0.9972

Fig. 7. The results of simulation with kinetic parameters obtained from global fitting and measured alkane conversion rate. Kinetic parameters (k3’, k4’, k6 and k7) are obtained by global fitting Eqs. (13)-(16) with data measured at 520 °C with steam. The solid red and blue points are measured at 520 °C and palkane = 0.25 atm with steam (pH2O = 1.8 kPa) and different ratio of pC3H8/pC2H6.

参考文献

[1]	J. J. H. B. Sattler, J. Ruiz-Martinez, E. Santillan-Jimenez, B. M. Weckhuysen, Chem. Rev., 2014, 114, 10613-10653.
[2]	C. Li, G. Wang, Chem. Soc. Rev., 2021, 50, 4359-4381.
[3]	Y. Dai, X. Gao, Q. Wang, X. Wan, C. Zhou, Y. Yang, Chem. Soc. Rev., 2021, 50, 5590-5630.
[4]	J. P. Lange, R. J. Schoonebeek, P. D. L. Mercera, F. W. van Breukelen, Appl. Catal. A, 2005, 283, 243-253.
[5]	C. A. Carrero, R. Schloegl, I. E. Wachs, R. Schomaecker, ACS Catal., 2014, 4, 3357-3380.
[6]	O. V. Buyevskaya, D. Müller, I. Pitsch, M. Baerns, Stud. Surf. Sci. Catal., 1998, 119, 671-676.
[7]	O. V. Buyevskaya, M. Baerns, Catal. Today, 1998, 42, 315-323.
[8]	J. T. Grant, C. A. Carrero, F. Goeltl, J. Venegas, P. Mueller, S. P. Burt, S. E. Specht, W. P. McDermott, A. Chieregato, I. Hermans, Science, 2016, 354, 1570-1573.
[9]	H. Zhou, X. Yi, Y. Hui, L. Wang, W. Chen, Y. Qin, M. Wang, J. Ma, X. Chu, Y. Wang, X. Hong, Z. Chen, X. Meng, H. Wang, Q. Zhu, L. Song, A. Zheng, F. S. Xiao, Science, 2021, 372, 76-80.
[10]	L. Shi, Y. Wang, B. Yan, W. Song, D. Shao, A. H. Lu, Chem. Commun., 2018, 54, 10936-10946.
[11]	W. P. McDermott, M. C. Cendejas, I. Hermans, Top. Catal., 2020, 63, 1700-1707.
[12]	J. M. Venegas, W. P. McDermott, I. Hermans, Acc. Chem. Res., 2018, 51, 2556-2564.
[13]	L. Wang, Y. Wang, R. Zhang, R. Ding, X. Chen, B. Lv, ACS Catal., 2020, 10, 6697-6706.
[14]	H. Fu, K. Huang, G. Yang, Y. Cao, H. Wang, F. Peng, X. Cai, H. Gao, Y. Liao, H. Yu, ACS Catal., 2021, 11, 8872-8880.
[15]	H. Yan, S. Alayoglu, W. Wu, Y. Zhang, E. Weitz, P. C. Stair, J. M. Notestein, ACS Catal., 2021, 11, 9370-9376.
[16]	Z. Liu, B. Yan, S. Meng, R. Liu, W.-D. Lu, J. Sheng, Y. Yi, A.-H. Lu, Angew. Chem. Int. Ed., 2021, 60, 19691-19695.
[17]	X. Zhang, R. You, Z. Wei, X. Jiang, J. Yang, Y. Pan, P. Wu, Q. Jia, Z. Bao, L. Bai, M. Jin, B. Sumpter, V. Fung, W. Huang, Z. Wu, Angew. Chem. Int. Ed., 2020, 59, 8042-8046.
[18]	Q. Zheng, Y. Cao, N. Huang, R. Zhang, Y. Zhou, Acta Phys.-Chim. Sin., 2021, 37, 2009063.
[19]	J. Sheng, W.-C. Li, Y.-R. Wang, W.-D. Lu, B. Yan, B. Qiu, X.-Q. Gao, S.-Q. Cheng, L. He, A.-H. Lu, J. Catal., 2021, 400, 265-273.
[20]	J. Tian, J. Tan, M. Xu, Z. Zhang, S. Wan, S. Wang, J. Lin, Y. Wang, Sci. Adv., 2019, 5, eaav8063.
[21]	K. Chen, A. Khodakov, J. Yang, A. T. Bell, E. Iglesia, J. Catal., 1999, 186, 325-333.
[22]	E. V. Kondratenko, M. Cherian, M. Baerns, D. Su, R. Schlögl, X. Wang, I. E. Wachs, J. Catal., 2005, 234, 131-142.
[23]	R. Grabowski, Catal. Rev. Sci. Eng., 2006, 48, 199-268.
[24]	R. Huang, B. Zhang, J. Wang, K.-H. Wu, W. Shi, Y. Zhang, Y. Liu, A. Zheng, R. Schlögl, D. S. Su, ChemCatChem, 2017, 9, 3293-3297.
[25]	L. Shi, D. Wang, A.-H. Lu, Chin. J. Catal., 2018, 39, 908-913.
[26]	J. Tian, J. Lin, M. Xu, S. Wan, J. Lin, Y. Wang, Chem. Eng. Sci., 2018, 186, 142-151.
[27]	J. M. Venegas, I. Hermans, Org. Process Res. Dev., 2018, 22, 1644-1652.
[28]	J. M. Venegas, Z. Zhang, T. O. Agbi, W. P. McDermott, A. Alexandrova, I. Hermans, Angew. Chem. Int. Ed., 2020, 59, 16527-16535.
[29]	Y. Zhou, J. Lin, L. Li, X. Pan, X. Sun, X. Wang, J. Catal., 2018, 365, 14-23.
[30]	J. A. Loiland, Z. Zhao, A. Patel, P. Hazin, Ind. Eng. Chem. Res., 2019, 58, 2170-2180.
[31]	R. T. Paine, C. K. Narula, Chem. Rev., 2002, 90, 73-91.
[32]	J. M. Venegas, J. T. Grant, W. P. McDermott, S. P. Burt, J. Micka, C. A. Carrero, I. Hermans, ChemCatChem, 2017, 9, 2118-2127.
[33]	B. Qiu, F. Jiang, W.-D. Lu, B. Yan, W.-C. Li, Z.-C. Zhao, A.-H. Lu, J. Catal., 2020, 385, 176-182.
[34]	P. Kraus, R. P. Lindstedt, J. Phys. Chem. C, 2021, 125, 5623-5634.
[35]	Z. Liu, D. Xu, M. Xia, W.-D. Lu, A.-H. Lu, D. Wang, J. Phys. Chem. Lett., 2021, 12, 8770-8776.
[36]	L. Shi, D. Wang, W. Song, D. Shao, W.-P. Zhang, A.-H. Lu, ChemCatChem, 2017, 9, 1788-1793.
[37]	H. Li, J. Zhang, P. Wu, S. Xun, W. Jiang, M. Zhang, W. Zhu, H. Li, J. Phys. Chem. C, 2019, 123, 2256-2266.
[38]	Z. Zhang, E. Jimenez-Izal, I. Hermans, A. N. Alexandrova, J. Phys. Chem. Lett., 2019, 10, 20-25.
[39]	A. M. Love, B. Thomas, S. E. Specht, M. P. Hanrahan, J. M. Venegas, S. P. Burt, J. T. Grant, M. C. Cendejas, W. P. McDermott, A. J. Rossini, I. Hermans, J. Am. Chem. Soc., 2019, 141, 182-190.
[40]	T. Sainsbury, A. Satti, P. May, Z. Wang, I. McGovern, Y. K. Gun’ko, J. Coleman, J. Am. Chem. Soc., 2012, 134, 18758-18771.
[41]	C. T. Stanton, N. L. Garland, H. H. Nelson, J. Phys. Chem., 1991, 95, 8741-8744.
[42]	U. C. Sridharan, T. G. DiGiuseppe, D. L. McFadden, P. Davidovits, J. Chem. Phys., 1979, 70, 5422-5426.
[43]	J. DeHaven, M. T. O’Connor, P. Davidovits, J. Chem. Phys., 1981, 75, 1746-1751.
[44]	T. R. Burkholder, L. Andrews, J. Chem. Phys., 1991, 95, 8697-8709.
[45]	L. Annamalai, Y. Liu, P. Deshlahra, ACS Catal., 2019, 9, 10324-10338.
[46]	S. W. Benson, J. Am. Chem. Soc., 1965, 87, 972-979.
[47]	S. W. Benson, P. S. Nangia, Acc. Chem. Res., 1979, 12, 223-228.
[48]	W. E. Wallace, NIST Chemistry WebBook, NIST Standard Reference Database, 2018, 69.
[49]	T. Hayashi, L.-B. Han, S. Tsubota, M. Haruta, Ind. Eng. Chem. Res., 1995, 34, 2298-2304.