调节硅酸锌上的钴物种状态以最大限度地实现丙烷脱氢制丙烯

doi:10.1016/S1872-2067(24)60133-6

催化学报 ›› 2024, Vol. 66: 168-180.DOI: 10.1016/S1872-2067(24)60133-6

调节硅酸锌上的钴物种状态以最大限度地实现丙烷脱氢制丙烯

刘浩^a^,¹, 初秉宪^c^,¹, 陈天翔^d^,¹, 周杰^a, 董丽辉^c, 劳子桓^d, 李斌^c^,^*(), 何晓辉^a^,^e^,^*(), 纪红兵^a^,^b^,^*()

^a中山大学化学学院, 精细化工研究院, 生物有机合成化学教育部重点实验室, 广东广州 510275
^b浙江工业大学化工学院, 绿色石油加工与轻烃转化研究院, 绿色化工合成技术国家重点实验室育种基地, 浙江杭州 310014
^c广西大学化学化工学院, 广西石化资源加工与过程强化技术重点实验室, 广西南宁 530004
^d香港理工大学应用生物与化学技术系, 化学生物学与药物发现国家重点实验室, 香港红磡 999077
^e广东省热敏化学品合成与分离技术研究中心, 广东广州 510275

收稿日期:2024-06-14 接受日期:2024-08-31 出版日期:2024-11-18 发布日期:2024-11-10
通讯作者: *电子信箱: binli@gxu.edu.cn (李斌),hexiaohui@mail.sysu.edu.cn (何晓辉),jihb@mail.sysu.edu.cn (纪红兵).
作者简介:¹共同第一作者.
基金资助:
国家重点研发项目(2020YFA0210902);广东省自然科学杰出青年基金(2022B1515020035);国家自然科学基金(22078371);国家自然科学基金(U22A20428);国家自然科学基金(21938001);国家自然科学基金(22422815);山西省科技创新团队专项资金(202304051001007)

Modulation of the cobalt species state on zincosilicate to maximize propane dehydrogenation to propylene

Hao Liu^a^,¹, Bingxian Chu^c^,¹, Tianxiang Chen^d^,¹, Jie Zhou^a, Lihui Dong^c, Tsz Woon Benedict Lo^d, Bin Li^c^,^*(), Xiaohui He^a^,^e^,^*(), Hongbing Ji^a^,^b^,^*()

^aKey Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, Fine Chemical Industry Research Institute, School of Chemistry, IGCME, Sun Yat-sen University, Guangzhou 510275, Guangdong, China
^bState Key Laboratory Breeding Base of Green-Chemical Synthesis Technology, Institute of Green Petroleum Processing and Light Hydrocarbon Conversion, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, Zhejiang, China
^cGuangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, Guangxi, China
^dState Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hunghom, Hong Kong, China
^eGuangdong Technology Research Center for Synthesis and Separation of Thermosensitive Chemicals, Guangzhou 510275, Guangdong, China

Received:2024-06-14 Accepted:2024-08-31 Online:2024-11-18 Published:2024-11-10
Contact: *E-mail: binli@gxu.edu.cn (B. Li),hexiaohui@mail.sysu.edu.cn (X. He),jihb@mail.sysu.edu.cn (H. Ji).
About author:¹Contributed equally to this work.
Supported by:
National Key Research and Development Program Nanotechnology Specific Project(2020YFA0210902);Guangdong Natural Science Funds for Distinguished Young Scholar(2022B1515020035);National Natural Science Foundation of China(22078371);National Natural Science Foundation of China(U22A20428);National Natural Science Foundation of China(21938001);National Natural Science Foundation of China(22422815);Science and Technology Innovation Teams of Shanxi Province(202304051001007)

摘要/Abstract

摘要：

丙烷脱氢(PDH)具有原料单一、工艺流程短、收率高、投资成本低等优点, 有望成为未来丙烯扩产的主要方向. 在典型的PDH技术中, Oleflex^TM和Catofin^TM工艺分别使用了负载型PtSn/Al₂O₃和Cr₂O₃/Al₂O₃催化剂. 然而, 它们固有的缺点(主要由于铬对环境的毒性和铂的稀缺性)促使人们开发廉价高效的替代品. 含Co催化剂因能更好地激活C-H裂解, 尤其是以单个位点和簇的形式, 受到研究者的广泛关注. 通常, 沸石框架Co物种在烷烃脱氢反应中表现出较高的稳定性, 但由于活化温度较高, 更适用于乙烷脱氢(EDH), 在PDH中进一步权衡转化率-温度至关重要. 此外, 由于ZSM-5中框架Al的存在, 通常使得催化剂具有较高的酸度, 从而导致过于明显的副反应.

本文针对PDH反应催化剂在丙烷转化率和活化温度权衡、催化剂长期稳定性、丙烷选择性、活性位点及反应机理研究等问题, 对Co-沸石材料进行探索. 受益于沸石材料催化的优势, Co-沸石材料可能产生协同效应, 从而克服反应物由于载体的块状性质而无法充分接近活性位点的困难. 通过用离子交换(IE)将Co物种引入硅酸锌沸石中, 并进行直接H₂还原, 在此过程中, 它们与羟基介导的框架O(尤其是框架Zn相邻O)结合, 进而主要形成不饱和的单金属位点(Co-O₄). 硅酸锌沸石中Si-OH-Zn中的O比Si-OH对金属有更强的锚定作用, 并且与浸渍法(IWI)相比, 离子交换法(IE)可以更均匀、精确地定位到框架Zn附近, 从而在特定环(α和β)中形成类似框架的孤立Co物种. 该方法合成的催化剂中Co物种更倾向于T8位点锁定, 并以Co-O4的形式形成L酸、充当丙烷脱氢活性位点, 整体显示出较好的PDH性能. 优化后的2Co/Zn-4-IE (数字代表初始投料质量比)催化剂在25%丙烷气氛中于550 ºC进行丙烷脱氢时, 丙烷的初始转化率达到41.4%, 测试8.5 h后, 转化率保持在39.5%. 值得一提的是, Pt基催化剂在该反应条件下, 平衡转化值通常位于45%到50%之间, 而本文中2Co/Zn-4-IE催化剂的平衡转化值为49.7%. 特别考虑到以非贵金属作为活性位点, 该催化剂表现出较好的PDH性能, 但随着反应的继续进行, 或者在某些苛刻条件下反应时, Co物种会缓慢团聚并部分失活. 相对均一的Co物种分布有助于清楚地了解结构定义和催化过程. 在此基础上, 一系列原位光谱、球差电镜图和X射线吸收光谱等结果显示了Co物种的特定分布定位和配位, 而密度泛函理论计算, 包括投影态密度和晶体轨道汉密尔顿群证实了Co物种锚定的合理性, 以及特定的Co-O₄活性位点和相应的PDH反应途径.

综上, 本文为在PDH反应中开发Pt基、Cr基催化剂的替代品, 以及在其他温和条件下筛选用于某些反应的Co基催化剂提供了一定参考.

关键词: 硅酸锌沸石, 锚定效应, 微环境修饰, 孤立Co位点, 丙烷脱氢

Abstract:

Dispersing metals from nanoparticles into clusters or single atoms often exhibits unique properties such as the inhibition of structure-sensitive side reactions. Here, we reported the use of ion exchange (IE) methods and direct hydrogen reduction to achieve high dispersion of Co species on zincosilicate. The obtained 2Co/Zn-4-IE catalyst achieved an initial propane conversion of 41.4% at a temperature of 550 °C in a 25% propane and 75% nitrogen atmosphere for propane dehydrogenation. Visualization of the presence of Co species within specific rings (alpha-α, beta-β and delta-δ) was obtained by aberration-corrected scanning transmission electron microscopy. A series of Fourier transform infrared spectra confirmed the anchoring of Co by specific hydroxyl groups in zincosilicate and the specific coordination environment of Co and its presence in the rings essentially as a single site. The framework Zn for the modulation of the microenvironment and the presence of Co species as Lewis acid active sites (Co-O₄) was also supported by density functional theory calculations.

Key words: Zincosilicate zeolite, Anchoring effect, Microenvironment modification, Isolated Co site, Propane dehydrogenation

刘浩, 初秉宪, 陈天翔, 周杰, 董丽辉, 劳子桓, 李斌, 何晓辉, 纪红兵. 调节硅酸锌上的钴物种状态以最大限度地实现丙烷脱氢制丙烯[J]. 催化学报, 2024, 66: 168-180.

Hao Liu, Bingxian Chu, Tianxiang Chen, Jie Zhou, Lihui Dong, Tsz Woon Benedict Lo, Bin Li, Xiaohui He, Hongbing Ji. Modulation of the cobalt species state on zincosilicate to maximize propane dehydrogenation to propylene[J]. Chinese Journal of Catalysis, 2024, 66: 168-180.

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图/表 8

Fig. 1. Electron microscopy analyses of the 2Co/Zn-4-IE with a Co actual content of 1.0 wt% (after H2 reduction, 550 °C). (a,b) Low-resolution HAADF-STEM images. (c,e) AC-STEM images of the 2Co/Zn-4-IE framework are taken along the two main crystallographic axes. (d,f) Structure of the MFI-type framework. (g) AC-STEM image of 2Co/Zn-4-IE along the straight 10-MR channel (i.e., the [010] axis). (h-j) The rectangular regions in Fig. 1(g) are enlarged to reveal the different positions of Co species within the different rings (α, β, and γ). (k) AC-STEM images and elemental mappings for Si, O, Zn, and Co.

Fig. 2. (a-c) Co 2p and Zn 2p spectra of different samples (H2 represents the sample reduced in a H2 at 550 °C for 1 h; R represents the sample reacted in a 25% propane atmosphere at 550 °C for 8.5 h). Fits of the FT Co K-edge EXAFS spectra of 2Co/Zn-4-IE-H2 (d), 1Co/Zn-4-IWI-H2 (e) and 2Co/Zn-4-IE-R (f). Fits of the FT Zn K-edge EXAFS spectra of 2Co/Zn-4-IE-H2 (g), 1Co/Zn-4-IWI-H2 (h) and 2Co/Zn-4-IE-R (i).

Fig. 3. Co 2p spectra of 2Co/Zn-4-IE (a) and 1Co/Zn-4-IWI (b) (the sample were reduced in situ in H2 at 550 °C for 1 h). It is worth mentioning that in situ XPS was first collected at room temperature and then collected again after 1 h of in situ warming and reduction, allowing for a more realistic state of the Co species.

Fig. 4. (a-c) FT-IR spectra of Zn-4, 1Co/Zn-4-IWI and 2Co/Zn-4-IE are recorded after NO adsorption. (d) H2-TPR curves of 1Co/Zn-4-IWI and 2Co/Zn-4-IE. (e) FT-IR spectra of different samples. (f) UV-vis-NIR spectra of Zn-4, 2Co/Zn-4-IE and 2Co/Zn-4-IE-H2 (Zn-4 and 2Co/Zn-4-IE are dehydrated at 400 °C under vacuum). (g) Different rings of Co species present in zeolite channels (α,β,γ). (h) UV-vis-NIR spectra of (0.5-4)Co/Zn-4-IE (these samples are dehydrated at 400 °C under vacuum). (i) Rietveld refinement of SXRD data and the corresponding refined crystal structure of Co/Zn-4-IE-H2.

Fig. 5. FT-IR spectra of Zn-4 (a), 1Co/Zn-4-IWI (b) and 2Co/Zn-4-IE (c) are recorded after CD3CN adsorption and desorption at different temperatures. (d-g) Pyridine-adsorbed FT-IR spectra and corresponding numbers of acid sites at different temperatures. (h) NH3-TPD curves. (i) DRIFTS spectra of -OH groups.

Fig. 6. (a) PDH performance over various catalysts. (b) PDH performance of 2Co/Zn-4-IE under various WHSV. (c) PDH performance of 2Co/Zn-4-IE at different temperatures and reaction atmospheres, pure C3H8, WHSV=8.5 h-1 (unless otherwise specified). (d,e) PDH performance over 2Co/Zn-4-IE after 10 (350 °C for 4 h) or 6 (450 °C for 1 h) regeneration cycles. (f) Productivity of C3H6 versus deactivation rate for the catalysts in this work compared with other Co-based catalysts.

Fig. 7. (a) Optimized structure of 2Co/Zn-4-IE by DFT calculations with relative energy shown in eV. (Si: green; Zn: silvery; O: red; Co: blue). Lower energy indicates greater stability and a higher probability of existence. (b) PDOS analysis for the framework O atom surrounding Zn sites. (c) PDOS analysis for Co and surrounding O atom. (d) -COHP of O 2p-Co 3d interaction curves. (e) PDOS of Co, H and C atoms in *H + *C3H7 adsorbed on Co-Zn-CSU. (f) COHP on H 1s-Co 3d interaction and H 1s - C 2p interaction. Here, both H and C are in the methylene group of *C3H7.

Fig. 8. The calculated energy profiles along the minimum energy pathways and the optimized intermediates upon PDH reaction with the reduced 2Co/Zn-4-IE. blue, silvery, red, brown, green, and white spheres represent Co, Zn, O, C, Si, and H atoms, respectively.

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调节硅酸锌上的钴物种状态以最大限度地实现丙烷脱氢制丙烯

Modulation of the cobalt species state on zincosilicate to maximize propane dehydrogenation to propylene

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