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Solid-state NMR for metal-containing zeolites: From active sites to reaction mechanism

Xingling Zhao, Jun Xu, Feng Deng

《化学科学与工程前沿（英文）》 2020年 第14卷 第2期   页码 159-187 doi: 10.1007/s11705-019-1885-1

摘要： Metal-containing zeolite catalysts have found a wide range of applications in heterogeneous catalysis. To understand the nature of metal active sites and the reaction mechanism over such catalysts is of great importance for the establishment of structure-activity relationship. The advanced solid-state NMR (SSNMR) spectroscopy is robust in the study of zeolites and zeolite-catalyzed reactions. In this review, we summarize recent developments and applications of SSNMR for exploring the structure and property of active sites in metal-containing zeolites. Moreover, detailed information on host-guest interactions in the relevant zeolite catalysis obtained by SSNMR is also discussed. Finally, we highlight the mechanistic understanding of catalytic reactions on metal-containing zeolites based on the observation of key surface species and active intermediates.

关键词： metal-containing zeolites     solid-state NMR     active site     host-guest interaction     reaction mechanism    

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Optimizing iodine capture performance by metal–organic framework containing with bipyridine units

《化学科学与工程前沿（英文）》 2023年 第17卷 第4期   页码 395-403 doi: 10.1007/s11705-022-2218-3

摘要： Radioactive iodine exhibits medical values in radiology, but its excessive emissions can cause environmental pollution. Thus, the capture of radioiodine poses significant engineering for the environment and medical radiology. The adsorptive capture of radioactive iodine by metal–organic frameworks (MOFs) has risen to prominence. In this work, a Th-based MOF (denoted as Th-BPYDC) was structurally designed and synthesized, consisting of [Th6(μ3-O)4(μ3-OH)4(H2O)6]12+ clusters, abundant bipyridine units, and large cavities that allowed guest molecules diffusion and transmission. Th-BPYDC exhibited the uptake capacities of 2.23 g·g−1 and 312.18 mg·g−1 towards I2 vapor and I2 dissolved in cyclohexane, respectively, surpassing its corresponding analogue Th-UiO-67. The bipyridine units boosted the adsorption performance, and Th-BPYDC showed good reusability with high stability. Our work thus opened a new way for the synthesis of MOFs to capture radioactive iodine.

关键词： metal–organic framework     iodine     adsorption     nuclear waste     environmental remediation    

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Crystalline porous materials: from zeolites to metal-organic frameworks (MOFs)

Zaiku Xie, Bao-Lian Su

《化学科学与工程前沿（英文）》 2020年 第14卷 第2期   页码 123-126 doi: 10.1007/s11705-020-1921-1

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Confinement effects in methanol to olefins catalysed by zeolites: A computational review

German Sastre

《化学科学与工程前沿（英文）》 2016年 第10卷 第1期   页码 76-89 doi: 10.1007/s11705-016-1557-3

摘要： Small pore zeolites, containing 8-rings as the largest, are widely employed as catalysts in the process of methanol-to-olefins (MTO). Reactants and products diffuse with constraints through 8-rings and this is one of the reaction bottlenecks related to zeolite micropore topology. Small pore zeolites and silicon-aluminophosphates(SAPOs) containing cavities, where olefins are mainly formed through the hydrocarbon pool (HP) mechanism, are frequently tested for MTO. Shape selectivity of transition states within the side-chain methylation will be reviewed as this is one of the controlling steps of the MTO process, with particular attention to the role of hexamethylbenzene (HMB) and heptamethylbenzenium cation (HeptaMB ), which are the most tipically detected reaction intermediates, common to the paring and side-chain routes within the HP mechanism. The relative stability of these and other species will be reviewed in terms of confinement effects in different cage-based zeolites. The role of the different alkylating agents, methanol, dimethyl ether (DME), and surface methoxy species (SMS) will also be reviewed from the computational viewpoint.

关键词： small pore zeolites     SAPOs     methanol-to-olefins     hydrocarbon pool mechanism     alkylation of polymethylbenzenes    

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Construction of defect-containing UiO-66/MoSe heterojunctions with superior photocatalytic performance

《化学科学与工程前沿（英文）》 2023年 第17卷 第4期   页码 449-459 doi: 10.1007/s11705-022-2226-3

摘要： Metal–organic frameworks are recognized as promising multifunctional materials, especially metal–organic framework-based photocatalysts, which are considered to be ideal photocatalytic materials. Herein, a new type of UiO-66/MoSe2 composite was prepared using the solvothermal method. The optimum composite was selected by adjusting the mass ratio of UiO-66 and MoSe2. X-ray diffraction analysis showed that the mass ratio influenced the crystal plane exposure rate of the composite, which may have affected its photocatalytic performance. The composite is composed of ultra-thin flower-like MoSe2 that wrapped around cubic UiO-66, a structure that increases the abundance of active sites for reactions and is more conducive to the separation of carriers. The photocatalytic properties of the composite were evaluated by measuring the degradation rate of Rhodamine B and the catalyst’s ability to reduce Cr(VI)-containing wastewater under visible light irradiation. Rhodamine B was decolorized completely in 120 min, and most of the Cr(VI) was reduced within 150 min. The photochemical mechanism of the complex was studied in detail. The existence of Mo6+ and oxygen vacancies, in addition to the Z-type heterojunction promote the separation of electrons and holes, which enhances the photocatalytic effect.

关键词： UiO-66/MoSe2     photocatalysis     dye-containing wastewater     heavy metal wastewater     oxygen vacancies    

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Coextraction of vanadium and manganese from high-manganese containing vanadium wastewater by a solvent

Zishuai Liu, Yimin Zhang, Zilin Dai, Jing Huang, Cong Liu

《化学科学与工程前沿（英文）》 2020年 第14卷 第5期   页码 902-912 doi: 10.1007/s11705-019-1887-z

摘要： High-manganese containing vanadium wastewater (HMVW) is commonly produced during the vanadium extraction process from vanadium titano-magnetite. HMVW cannot be reused and discharged directly, and is harmful to the environment and affect product quality due to heavy metals in the wastewater. The wastewater is usually treated by lime neutralization, but valuable metals (especially V and Mn) cannot be recovered. In this study, an efficient and environmentally friendly method was developed to recover valuable metals by using a solvent extraction-precipitation process. In the solvent extraction process, 98.15% of vanadium was recovered, and the V O product, with a purity of 98.60%, was obtained under optimal conditions. For the precipitation process, 91.05% of manganese was recovered as MnCO which meets the III grade standard of HG/T 2836-2011. Thermodynamic simulation analysis indicated that MnCO was selectively precipitated at pH 6.5 while Mg and Ca could hardly be precipitated. The results of X-ray diffraction and scanning electron microscopy demonstrated that the obtained V O and MnCO displayed a good degree of crystallinity. The treated wastewater can be returned for leaching, and resources (V and Mn) in the wastewater were utilized efficiently in an environmentally friendly way. Therefore, this study provides a novel method for the coextraction of V and Mn from HMVW.

关键词： high-manganese containing vanadium wastewater     solvent extraction     carbonate precipitation     vanadium titano-magnetite     valuable metal recovery    

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Multifunctional heteroatom zeolites: construction and applications

《化学科学与工程前沿（英文）》 2021年 第15卷 第6期   页码 1462-1486 doi: 10.1007/s11705-021-2099-x

摘要： Multifunctional heteroatom zeolites have drawn broad attentions due to the possible synergistic effects in the catalytic reactions. Remarkable achievements have been made on the synthesis, characterization and catalytic applications of multifunctional heteroatom zeolite, while a review on this important topic is still missing. Herein, current research status of multifunctional heteroatom zeolites is briefly summarized, aiming to boost further researches. First, the synthesis strategies toward heteroatom zeolites are introduced, including the direct synthesis and postsynthesis routes; then, the spectroscopic techniques to identify the existing states of heteroatom sites and the corresponding physiochemical properties are shown and compared; finally, the catalytic applications of multifunctional heteroatom zeolites in various chemical reactions, especially in one-step tandem reactions, are discussed.

关键词： zeolite     multifunctional active sites     heteroatom     characterization     catalysis    

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Hierarchically porous zeolites synthesized with carbon materials as templates

《化学科学与工程前沿（英文）》 2021年 第15卷 第6期   页码 1444-1461 doi: 10.1007/s11705-021-2090-6

摘要： Hierarchically porous zeolites are promising candidates in catalytic conversion of relatively bulky molecules, and their syntheses have attracted significant attention. From both industrial and scientific perspectives, different carbon materials have been widely employed as hard templates for the preparation of hierarchically porous zeolites during the past two decades. In this review, the progress in synthetic strategies using carbon materials as templates is comprehensively summarized. Depending on the affinity between the carbon templates and zeolite precursors, the substantial strategies for synthesizing hierarchical zeolites are introduced in direct templates and indirect templates. Direct templates methods, by which the carbon materials are directly mixed with precursors gel as hard templates, are first reviewed. Then, we discuss the indirect templates method (crystallization of carbon-silica composites), by which the carbon is produced by in situ pyrolysis of organic-inorganic precursors. In addition, the technique of encapsulating metal species into zeolites crystals with the assistance of carbon templates is also discussed. In the conclusion part, the factors affecting the synthesis of carbon-templated hierarchically porous zeolites are remarked. This review is expected to attract interest in the synthesis strategies of hierarchically porous zeolites, especially cost-effective and large-scale production methodologies, which are essential to the industrial application of hierarchical zeolites.

关键词： hierarchical zeolites     carbon materials     direct templates     indirect templates     carbon-silica composites    

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High-precision diffusion measurement of ethane and propane over SAPO-34 zeolites for methanol-to-olefin

Dali Cai, Yu Cui, Zhao Jia, Yao Wang, Fei Wei

《化学科学与工程前沿（英文）》 2018年 第12卷 第1期   页码 77-82 doi: 10.1007/s11705-017-1684-5

摘要： The methanol-to-olefin (MTO) process has attracted much attention and many problems including lifetime and selectivity of light olefins have all been connected to the diffusion problems in zeolite crystals. However, a quantitative study of diffusion problems in SAPO-34 zeolites is lacking. In this paper, we performed a high-precision diffusion measurement of the diffusion behavior of ethane and propane, which represent ethylene and propylene respectively, over SAPO-34. The diffusions of ethane and propane over fresh and coked SAPO-34 zeolites with different crystal sizes were carefully studied. Ethane and propane show different diffusion behavior in SAPO-34. The diffusion of ethane is almost not influenced by the crystal size and coke percentage, whereas that of propane is strongly affected. A slower diffusion velocity was observed in bigger crystals, and the diffusion velocity decline significantly with the coke percentage increasing. The diffusion coefficient was calculated with both the internal and surface diffusion models, and the results show that the surface diffusion plays a key role in the diffusion process of both ethane and propane. We believe that this work would be helpful for understanding the diffusion of different molecules in SAPO-34 zeolites, and may lay the foundation of MTO research.

关键词： diffusion measurement     methanol-to-olefin process    

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用于气体分离的含多孔材料的混合基质膜——从金属有机框架到离散分子笼 Review

杨子琪, 吴中杰, 白胜博, 应允攀, 杨昊, 赵丹

《工程（英文）》 2023年 第23卷 第4期   页码 40-55 doi: 10.1016/j.eng.2022.07.022

摘要：

混合基质膜（MMMs）将多孔材料与聚合物基质结合，因二者的互补性和协同作用，MMMs在气体分离研究领域得到了广泛关注。多孔材料的可调节性和多样性赋予了MMMs可扩展的功能和优异的分离性能。为了充分发挥MMMs的潜力，研究人员专注于多孔填料与聚合物基质的合理匹配，以提高MMMs的
界面相容性。在本文中，我们重点介绍了利用不同策略，将金属有机框架（MOFs）或金属有机笼（MOCs）与聚合物基质相结合，以制备MMMs的最新进展，并且进一步讨论了MMMs未来发展所面临的机遇和挑战，这将通过合理的材料设计和选择促进MMMs的发展。

关键词： 气体分离     金属-有机框架     金属-有机笼     混合基质膜     界面相容性    

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Mesoporous zeolites for biofuel upgrading and glycerol conversion

Jian Zhang, Liang Wang, Yanyan Ji, Fang Chen, Feng-Shou Xiao

《化学科学与工程前沿（英文）》 2018年 第12卷 第1期   页码 132-144 doi: 10.1007/s11705-017-1681-8

摘要： With the recent emphasis and development of sustainable chemistry, the conversion of biomass feedstocks into alternative fuels and fine chemicals over various heterogeneous catalysts has received much attention. In particular, owing to their uniform micropores, strong acidity, and stable and rigid frameworks, zeolites as catalysts or co-catalysts have exhibited excellent catalytic performances in many reactions, including hydrodesulfurization, Fischer-Tropsch synthesis, and hydrodeoxygenation. However, the relatively small sizes of the zeolite micropores strongly limit the conversion of bulky biomolecules. To overcome this issue, mesoporous zeolites with pores larger than those of biomolecules have been synthesized. As expected, these mesoporous zeolites have outperformed conventional zeolites with improved activities, better selectivities, and longer catalyst lives for the upgrading of pyrolysis oils, the transformation of lipids into biofuels, and the conversion of glycerol into acrolein and aromatic compounds. This review briefly summarizes recent works on the rational synthesis of mesoporous zeolites and their superior catalytic properties in biomass conversion.

关键词： biomass conversion     mesoporous zeolite     sustainable chemistry    

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Extractive desulfurization of model fuels with a nitrogen-containing heterocyclic ionic liquid

《化学科学与工程前沿（英文）》 2022年 第16卷 第12期   页码 1735-1742 doi: 10.1007/s11705-022-2167-x

摘要： A nitrogen-containing ionic liquid was synthesized using an aromatic nitrogen-containing heterocyclic and an amino acid, and applied to the extractive desulfurization process to remove benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiphene from a model fuel oil. Chemical characterizations and simulation using Gaussian 09 software confirmed the rationality of an ionic liquid structure. Classification of non-covalent interactions between the ionic liquid and the three sulfur-containing contaminants was studied by reduced density gradient analysis. The viscosity of the ionic liquid was adjusted by addition of polyethylene glycol. Under extraction conditions of the volume of ionic liquid to oil as 1:1 and temperature as room temperature, the desulfurization selectivity of ionic liquid followed the order of 4,6-dimethyldibenzothiphene (15 min) < benzothiophene (15 min) ≈ dibenzothiophene (10 min). Addition of p-xylene and cyclohexene to the fuel oil had little effect. The extractant remained stable and effective after multiple regeneration cycles.

关键词： extractive desulfurization     nitrogen-containing heterocyclic ionic liquid     reduced density gradient analysis     desulfurization selectivity    

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Mesoporous zeolites as efficient catalysts for oil refining and natural gas conversion

Jie ZHU, Xiangju MENG, Fengshou XIAO

《化学科学与工程前沿（英文）》 2013年 第7卷 第2期   页码 233-248 doi: 10.1007/s11705-013-1329-2

摘要： Zeolites have been regarded as one of the most important catalysts in petrochemical industry due to their excellent catalytic performance. However, the sole micropores in zeolites severely limit their applications in oil refining and natural gas conversion. To solve the problem, mesoporous zeolites have been prepared by introducing mesopores into the zeolite crystals in recent years, and thus have the advantages of both mesostructured materials (fast diffusion and accessible for bulky molecules) and microporous zeolite crystals (strong acidity and high hydrothermal stability). In this review, after giving a brief introduction to preparation, structure, and characterization of mesoporous zeolites, we systematically summarize catalytic applications of these mesoporous zeolites as efficient catalysts in oil refining and natural gas conversion including catalytic cracking of heavy oil, alkylation, isomerization, hydrogenation, hydrodesulfurization, methane dehydroaromatization, methanol dehydration to dimethyl ether, methanol to olefins, and methanol to hydrocarbons.

关键词： mesoporous zeolite     catalysis     oil refining     natural gas conversion    

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Fabrication of titanosilicate pillared MFI zeolites with tailored catalytic activity

Baoyu Liu, Qiaowen Mu, Jiajin Huang, Wei Tan, Jing Xiao

《化学科学与工程前沿（英文）》 2020年 第14卷 第5期   页码 772-782 doi: 10.1007/s11705-019-1859-3

摘要： Titanosilicate pillared MFI zeolite nanosheets were successfully synthesized by infiltrating the mixed tetraethyl orthosilicate (TEOS)/tetrabutyl orthotitanate (TBOT) solvent into the gallery space between adjacent MFI zeolite layers. The obtained zeolite catalysts were characterized using powder X-ray diffraction, N adsorption/desorption isotherms, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy techniques. The H O oxidation of dibenzothiophene (DBT) was used to evaluate the catalytic performance of the obtained titanosilicate pillared MFI zeolites. The conversion of DBT and selectivity of dibenzothiophene sulfone (DBTS) were most affected by the textural properties of the zeolites. This was attributed to the DBT and DBTS molecules being larger than micropores of the MFI zeolites. The conversion of DBT and yield of DBTS could be systematically tailored by tuning the molar ratio of the TEOS/TBOT solvent. These results implied that a balance between the meso- and microporosity of zeolites and tetrahedrally coordinated Ti(IV) active sites of titanosilicate pillars can be achieved for the preparation of desired catalysts during the oxidation of bulk S compounds.

关键词： MFI zeolite     catalysis     nanosheets     fabrication    

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The effect of hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios on its pore structure

Yuexin Hou, Xiaoyun Li, Minghui Sun, Chaofan Li, Syed ul Hasnain Bakhtiar, Kunhao Lei, Shen Yu, Zhao Wang, Zhiyi Hu, Lihua Chen, Bao-Lian Su

《化学科学与工程前沿（英文）》 2021年 第15卷 第2期   页码 269-278 doi: 10.1007/s11705-020-1948-3

摘要： Hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios (Hier-ZSM-5- , where = 50, 100, 150 and 200) were synthesized using an ordered mesoporous carbon-silica composite as hard template. Hier-ZSM-5- exhibits improved mass transport properties, excellent mechanical and hydrothermal stability, and higher catalytic activity than commercial bulk zeolites in the benzyl alcohol self-etherification reaction. Results show that a decrease in the Si/Al ratio in hierarchical single-crystal ZSM-5 zeolites leads to a significant increase in the acidity and the density of micropores, which increases the final catalytic conversion. The effect of porous hierarchy on the diffusion of active sites and the final catalytic activity was also studied by comparing the catalytic conversion after selectively designed poisoned acid sites. These poisoned Hier-ZSM-5- shows much higher catalytic conversion than the poisoned commercial ZSM-5 zeolite, which indicates that the numerous intracrystalline mesopores significantly reduce the diffusion path of the reactant, leading to the faster diffusion inside the zeolite to contact with the acid sites in the micropores predominating in ZSM-5 zeolites. This study can be extended to develop a series of hierarchical single-crystal zeolites with expected catalytic performance.

关键词： hierarchical zeolites     single crystalline     interconnected pores     improved diffusion performance     benzyl alcohol self-etherification reaction    

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标题 作者 时间 类型 操作

Solid-state NMR for metal-containing zeolites: From active sites to reaction mechanism

Xingling Zhao, Jun Xu, Feng Deng

期刊论文

Optimizing iodine capture performance by metal–organic framework containing with bipyridine units

期刊论文

Crystalline porous materials: from zeolites to metal-organic frameworks (MOFs)

Zaiku Xie, Bao-Lian Su

期刊论文

Confinement effects in methanol to olefins catalysed by zeolites: A computational review

German Sastre

期刊论文

Construction of defect-containing UiO-66/MoSe heterojunctions with superior photocatalytic performance

期刊论文

Coextraction of vanadium and manganese from high-manganese containing vanadium wastewater by a solvent

Zishuai Liu, Yimin Zhang, Zilin Dai, Jing Huang, Cong Liu

期刊论文

Multifunctional heteroatom zeolites: construction and applications

期刊论文

Hierarchically porous zeolites synthesized with carbon materials as templates

期刊论文

High-precision diffusion measurement of ethane and propane over SAPO-34 zeolites for methanol-to-olefin

Dali Cai, Yu Cui, Zhao Jia, Yao Wang, Fei Wei

期刊论文

用于气体分离的含多孔材料的混合基质膜——从金属有机框架到离散分子笼

杨子琪, 吴中杰, 白胜博, 应允攀, 杨昊, 赵丹

期刊论文

Mesoporous zeolites for biofuel upgrading and glycerol conversion

Jian Zhang, Liang Wang, Yanyan Ji, Fang Chen, Feng-Shou Xiao

期刊论文

Extractive desulfurization of model fuels with a nitrogen-containing heterocyclic ionic liquid

期刊论文

Mesoporous zeolites as efficient catalysts for oil refining and natural gas conversion

Jie ZHU, Xiangju MENG, Fengshou XIAO

期刊论文

Fabrication of titanosilicate pillared MFI zeolites with tailored catalytic activity

Baoyu Liu, Qiaowen Mu, Jiajin Huang, Wei Tan, Jing Xiao

期刊论文

The effect of hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios on its pore structure

Yuexin Hou, Xiaoyun Li, Minghui Sun, Chaofan Li, Syed ul Hasnain Bakhtiar, Kunhao Lei, Shen Yu, Zhao Wang, Zhiyi Hu, Lihua Chen, Bao-Lian Su

期刊论文