MOR分子筛中非骨架铝在OXZEO催化合成气转化中的作用

doi:10.1016/S1872-2067(24)60135-X

催化学报 ›› 2024, Vol. 67: 135-143.DOI: 10.1016/S1872-2067(24)60135-X

MOR分子筛中非骨架铝在OXZEO催化合成气转化中的作用

王浩迪^a^,^b, 焦峰^a^,^b(), 封景耀^a^,^b, 孙玉婷^a^,^b, 侯广进^a^,^b, 潘秀莲^a^,^b(), 包信和^a

^a中国科学院大连化学物理研究所, 催化国家重点实验室, 大连清洁能源国家实验室, 2011-能源材料化学合作创新中心, 辽宁大连 116023
^b中国科学院大学, 北京 100049

收稿日期:2024-07-30 接受日期:2024-09-06 出版日期:2024-11-30 发布日期:2024-11-30
通讯作者: 焦峰,潘秀莲
基金资助:
国家重点研发计划(2018YFA0704503);国家重点研发计划(2023YFB4103700);国家自然科学基金(22321002);国家自然科学基金(22272167);大连市科技创新基金(2022RY02);大连化物所创新研究基金(DICP I202424);辽宁省自然科学基金(2023-MS-003)

Role of extra-framework aluminum species within MOR zeolites for syngas conversion via OXZEO catalysis

Haodi Wang^a^,^b, Feng Jiao^a^,^b(), Jingyao Feng^a^,^b, Yuting Sun^a^,^b, Guangjin Hou^a^,^b, Xiulian Pan^a^,^b(), Xinhe Bao^a

^aState Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
^bUniversity of Chinese Academy of Sciences, Beijing 100049, China

Received:2024-07-30 Accepted:2024-09-06 Online:2024-11-30 Published:2024-11-30
Contact: Feng Jiao, Xiulian Pan
Supported by:
Ministry of Science and Technology of China(2018YFA0704503);Ministry of Science and Technology of China(2023YFB4103700);National Natural Science Foundation of China(22321002);National Natural Science Foundation of China(22272167);Dalian Science and Technology Innovation Fund(2022RY02);Innovation Research Fund of Dalian Institute of Chemical Physics(DICP I202424);Liaoning Natural Science Foundation(2023-MS-003)

摘要/Abstract

摘要：

丝光沸石(MOR)是一类重要的分子筛, 广泛应用于烃类异构化、裂解反应、二甲醚羰基化、合成气转化等各种催化过程. MOR的催化魅力主要得益于其独特的孔道结构以及可调节的酸位点分布. 尽管研究者们已经付出了巨大努力优化铝在骨架上的分布以提升催化性能, 但由于MOR骨架不稳定性, 铝物种很容易从骨架上脱除形成非骨架铝(EFAl)物种. 然而目前关于EFAl物种在合成气转化中的作用尚不知晓.

本文采取调整硅源和铝源前驱体的策略制备了八元环(8MR)和十二元环(12MR)孔道酸密度相当但EFAl含量不同的MOR分子筛, 与ZnAlO_x氧化物组成金属氧化物-分子筛(OXZEO)双功能催化剂并考察了它们在合成气转化中的催化作用. 结果表明, 当存在较少量的EFAl时(MOR-EFAl-1), 反应具有显著的诱导期, 同时副产物甲烷、C₂-C₄烷烃以及长碳链烃类(C₅₊)的选择性较高. 而在过量的EFAl物种(MOR-EFAl-3)存在时, 反应在初始阶段迅速失活, 并且甲烷、C₂-C₄烷烃的选择性也较高. 智能重量分析法、乙烯转化模型实验和热重分析结果表明, EFAl物种含量少的MOR其宽敞的12MR孔道会促进乙烯向C₅₊的二次转化, 最终导致碳物种在分子筛孔道内沉积. 然而, 过量的EFAl物种会使12MR孔道的空间受限, 从而导致严重的扩散限制. 总体而言, 只有存在适量的EFAl物种(MOR-EFAl-2)可以抑制乙烯的二次转化以及积碳物种的形成. 因此ZnAlO_x-MOR-EFAl-2双功能催化剂可以获得较好的乙烯选择性, 同时反应的稳定性也得到提高.

综上, 本文通过多种表征手段深入探讨了EFAl物种在合成气转化中的催化作用, 为设计更高效的分子筛催化剂提供了重要参考.

关键词: 合成气转化, 丝光沸石, 非骨架铝, 乙烯选择性, 扩散

Abstract:

The location of aluminum within the framework or extra-framework of zeolites is a critical factor in determining its catalytic performance. Despite extensive research on the identification and formation mechanism of extra-framework aluminum (EFAl), its impact on catalytic performance requires further investigation. Herein, mordenite (MOR) zeolites with comparable acid density within the 8MR and 12MR channels but different EFAl contents were prepared, and their catalytic roles were examined in syngas conversion. Intelligent gravimetric analysis, model experiment of ethylene conversion and thermogravimetric analysis demonstrate that the existence of EFAl species can inhibit the secondary conversion of ethylene to long chain hydrocarbons (i.e., C₅₊) as well as the over-accumulation of carbonaceous species. However, excessive EFAl species lead to rapid deactivation due to restricted space and thus severe diffusion limitation. MOR zeolite with a moderate amount of EFAl species achieves a superior ethylene selectivity and exhibits an enhanced stability in syngas conversion when combined with ZnAlO_x oxide. The insights gained in this work provide important guidance for the design of more efficient zeolite-based catalysts.

Key words: Syngas conversion, OR zeolite, Extra-framework aluminum, Ethylene selectivity, Diffusion

王浩迪, 焦峰, 封景耀, 孙玉婷, 侯广进, 潘秀莲, 包信和. MOR分子筛中非骨架铝在OXZEO催化合成气转化中的作用[J]. 催化学报, 2024, 67: 135-143.

Haodi Wang, Feng Jiao, Jingyao Feng, Yuting Sun, Guangjin Hou, Xiulian Pan, Xinhe Bao. Role of extra-framework aluminum species within MOR zeolites for syngas conversion via OXZEO catalysis[J]. Chinese Journal of Catalysis, 2024, 67: 135-143.

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链接本文: https://www.cjcatal.com/CN/10.1016/S1872-2067(24)60135-X

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图/表 6

Table 1 Analysis of the Al distribution in MOR zeolites.

Sample	Si/Al ^a	Al distribution^b (%)				Al content^b (μmol g^-1)
Sample	Si/Al ^a	EFAl	T₁	T₂+T₄	T₃	EFAl	12MR	8MR
MOR-EFAl-1	9.2	0.21	14.19	45.10	40.49	3.4	978.5	668.2
MOR-EFAl-2	6.2	23.61	10.77	36.54	29.08	562.1	1126.5	692.4
MOR-EFAl-3	4.6	37.84	13.80	24.17	24.20	1146.7	1150.4	733.2

Fig. 1. Identification of aluminum species within MOR. (a) Deconvoluted bands of FT-IR spectra corresponding to the hydroxyls in the EFAl (3660 cm-1), T1 sites (TF, 3620 cm-1), T2+T4 sites (HF, 3607 cm-1) and T3 sites (LF, 3587 cm-1). (b) 27Al MAS NMR spectra.

Fig. 2. Catalytic performance of ZnAlOx-MOR bifunctional catalysts in syngas conversion with time on stream. (a) CO conversion. (b) Hydrocarbon distribution and CO conversion at time on stream of 40 h. (c) Hydrocarbon distribution for MOR-EFAl-1. (d) Hydrocarbon distribution for MOR-EFAl-2. (e) Hydrocarbon distribution for MOR-EFAl-3. Reaction conditions: 375 °C, 2.5 MPa, H2/CO=1, ZnAlOx/MOR=1/1 (mass ratio), 1800 mL g-1 h-1.

Fig. 3. IGA analysis and ethylene conversion as a model reaction. (a) Uptake curves of ethane analyzed by IGA at 30 °C with the pressure increasing from 0 to 10 mbar. (b) Uptake curves of n-butane analyzed by IGA at 30 °C with the pressure increasing from 0 to 5 mbar, the inset is the initial adsorption rate curves. (c) The yield of C3+ and C5+ in ethylene conversion at TOS of 10 h. (d) The selectivity ratio of (C3= + C4=) to C5+ in ethylene conversion at TOS of 10 h. Reaction conditions: 375 °C, 2.5 MPa, 21600 mL g-1 h-1, 0.6% C2H4 + H2 + Ar.

Fig. 4. TGA and DTG profiles of used MOR zeolites in syngas reaction for 4 and 8 h. (a) MOR-EFAl-1; (b) MOR-EFAl-2; (c) MOR-EFAl-3. (d) Carbonaceous species amount calculated from the TGA curves. The range of 200 to 480 °C corresponds to carbonaceous species I, and the range of 480 to 900 °C to carbonaceous species II.

Scheme 1. Schematic diagram of the role of EFAl species within MOR zeolites for syngas conversion.

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MOR分子筛中非骨架铝在OXZEO催化合成气转化中的作用

Role of extra-framework aluminum species within MOR zeolites for syngas conversion via OXZEO catalysis

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