MICROPOROUS AND MESOPOROUS MATERIALS
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2018
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IF 3.649
Baoyu Liu,Zhipeng Chen,Jiajin Huang,Huiyong Chen,Yanxiong Fang
The MFI zeolites with nanosheet assemblies morphology were prepared by a seed-assisted strategy using specially designed bolaform surfactant [C 6 H 13 -N + (CH 3 ) 2 -C 6 H 12 -N + (CH 3 ) 2 -(CH 2 ) 12 -O-(p-C 6 H 4 ) 2 -O-(CH 2 ) 12 -N + (CH 3 ) 2 -C 6 H 12 -N + (CH 3 ) 2 -C 6 H 13 ] [Br − ] 4 (C 6-12-diphe ) as a structure-directing agent. The MFI zeolite nanosheet assemblies were composed of MFI nanosheets with randomly organized structure, exhibiting a narrow mesopore distribution. By tuning the Si/Al ratios of MFI zeolite nanosheet assemblies from 60 to 10, the morphology of resultant zeolites changed from nanosheet stacks to house-of-cards-like structures, and to nanosponges. In addition, the porosity and Brønsted acid/Lewis acid ratio exhibited a parabola-type dependence on the Si/Al ratios of obtained zeolites, indicating that meso-/microporosity and acidity of MFI nanosheet assemblies can be systematically tailored by changing the constituents of zeolites. Catalytic performance of MFI zeolite nanosheet assemblies was investigated in the benzylation of benzyl alcohol with mesitylene. The results revealed that MFI zeolite nanosheet assemblies exhibited extraordinary catalytic activity compared to conventional ZSM-5 zeolite. The conversion of benzyl alcohol and selectivity (1,3,5-trimethyl-2-benzylbenzene vs dibenzyl ether) of zeolite catalysts were linearly dependent on the Brønsted acid/Lewis acid ratio, and they exhibited a parabola-type dependence on the S ext /S BET , indicating that a balance between acidity and porosity of zeolites can be realized to modulate the catalytic properties of MFI zeolite nanosheet assemblies guided by C 6-12-diphe .
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Particuology
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2017
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IF 2.621
Rongjie Ling,Wu Chen,Jin Hou
Modified nanosized MFI (ZSM-5 and silicalite-1) zeolites were successfully synthesized by a hydrothermal method using aluminum isopropoxide and tetraethylorthosilicate as the raw materials. The synthetic zeolites were characterized by X-ray diffraction, energy dispersion spectroscopy, and scanning electron microscopy. The ZSM-5 and silicalite-1 zeolites exhibited ellipse-like and cubic columns, respectively. The K + ion-exchange equilibrium and ion-exchange capacity of the synthetic zeolites in seawater were investigated. The K + ion-exchange of synthetic zeolites was rapid and reached an ion-exchange balance in approximately 20 min. The K + ion-exchange capacity of ZSM-5 and silicalite-1 in seawater was 56.7 and 48.7 mg/g, respectively. The synthetic zeolites have high selectivity toward K + , and therefore, they can be used to selectively extract potassium from seawater.
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CRYSTAL GROWTH & DESIGN
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2024
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IF 3.2
Rui Wang,Ruilan Xu,Kaipeng Zhang,Lu Gan,Xintu Lin,Shangxi Zhang,Yong Peng
Preventing the appearance of fog on transparent glass is an important issue not only in our daily lives but also in scientific research and clinical diagnosis. A zeolite molecular sieve with MFI-type structure was identified as a very promising antifog material. In this work, MFI zeolite films with different microstructures were prepared by the solvothermal secondary growth method using diols including ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), and tetraethylene glycol (tEG) as solvents. The elimination mechanism of new MFI twin crystals was demonstrated based on scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) characterizations of the resulting films and the mother solutions. The twin-free MFI films with b-axis preferred channel orientation exhibited both higher light transmittance and lower haze compared with the a-&b-mix-oriented film. The employment of diol solvents facilitated the generation of a surface Si–OH group on the films, leading to the improvement of film hydrophilicity. By taking advantages of the high transparency and hydrophilicity, the b-oriented MFI films synthesized on glass substrate achieved good antifogging performance.
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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2024
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IF 3.8
Zhanbo Guo,Chao Feng,Zongnan Shen,Xun Deng,Xinrong Feng,Min Deng,Jie Liu,Wenju Jiang,Lin Yang,Lu Yao,Zhongde Dai
Membranes have been considered as promising alternatives for natural gas sweetening. Mixed matrix membranes (MMMs) possess superior gas separation performance and the potential to combine varieties of polymers and filler materials. In the current work, MMMs have been fabricated via employing Tröger’s base (TB) polymer and zeolites with three different morphologies. Simultaneously, CO2/CH4 and H2/CH4 separation performances of the obtained MMMs were comprehensively investigated. It is found out that the presence of the MFI-type zeolites significantly improved the gas permeability, but the selectivity was somehow reduced. Among the three different nanofillers, nanosheet zeolite-based MMMs presented the highest gas permeability; with 20 wt % nanosheet zeolites, both CO2 and H2 permeabilities were increased to 348.6 and 441.5 Barrer, which were improved by 522.0 and 256.2%, respectively. In addition, SEM, XRD, FTIR, and TGA were also employed to characterize the obtained MMMs.
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FUEL
·
2024
·
IF 6.7
Quanli Ke,Pengyun Pan,Mei Lu,Guonan Fang,Wei Zhang,Ruina Zhang,Guokai Cui,Xiaopo Niu,Feng Xiong,Ying Zhou,Bo Zhao,Hanfeng Lu
Herein, copper and manganese heteroatoms were incorporated into the siliceous MFI frameworks with high dispersity. When employed in the CO 2 /N 2 binary gas separation, a delicate trade-off for the CO 2 adsorption capacity, adsorption heat and moisture resistance could be realized on the heteroatom-incorporated MFI zeolites, especially the Cu-incorporated one. In order to confirm the role that heteroatoms played in CO 2 adsorption, the textural analyses were then conduced, which proved that the enhanced microporosity may be at the heart of the promoted CO 2 capacity. Next to that, the in situ DRIFTs spectra were continuously tracked during the dynamic adsorption process. Compared to the commercial aluminosilicate analogue, the MFI zeolites with Cu/Mn heteroatoms possesses weaker electrostatic field intensity, which in consequence resulted in their stronger moisture resistance, even in presence of humidity up to 90 RH%. As such, a bottom-up adjustment for the adsorption properties of zeolites in practical environment containing competitive moisture impurity was shown.
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FUEL
·
2024
·
IF 6.7
Kaiwei Wang,Fumin Wang,Yi Zhai,Xubin Zhang,Mingshuai Sun,Jinjin Zhang,Xiaolu Fan,Changhao Bing
The metal species embedded in specific positions within the zeolite framework and their unique microenvironment exhibit fascinating effects on catalytic performance. Herein, we incorporated tetrahedrally coordinated Co 2+ into the framework of hollow silicate-1 zeolite and investigated the influence of halogen anions (Cl - , Br - and F - ) in the synthesized gel on the distribution of cobalt species in the channels. The addition of an appropriate amount of inorganic ammonium salts and seeds was found to be a necessary condition for cobalt incorporated into the framework. Notably, the Cl - anions present in the synthesis gel can induce more cobalt species located at the intersection cavity of silicate-1 (β-type). Comprehensive characterization results indicate that the tetrahedrally coordinated Co 2+ in the intersecting cavities of hollow zeolite appears to exhibit more efficient styrene epoxidation performance. This work presents a simple and cost-effective method to synthesize hollow cobalt-based zeolite with adjustable metal distribution in channels. By regulating the spatial distribution of cobalt species with halogens, the CS-0.1–0.5-Cl catalyst enhanced activity and selectivity in the epoxidation reaction of styrene to styrene oxide. Specifically, at a temperature of 80 °C after a reaction time of 6 h, the catalyst demonstrated a styrene oxide yield of 42.47 % and a excellent styrene oxide selectivity of 82.29 %.
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APPLIED CATALYSIS B-ENVIRONMENTAL
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2025
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IF 21.1
Yanwei Sun,Guangyan Xu,Chang Liu,Yajie Pan,Yingjie Wang,Yunbo Yu,Hong He
Although palladium-based catalysts exhibit excellent methane oxidation activity, sulfur poisoning still leads to severe deactivation. To overcome this, we synthesized an oxide-zeolite (OXZEO) composite, Ce x /Pd@MFI, via combined hydrothermal treatment and ball milling . In the resulting architecture, PdO x active sites are spatially confined within the MFI framework, while CeO 2 nanoparticles uniformly decorate the external surface as protective species. The optimized Ce 3 /Pd@MFI catalyst demonstrated markedly enhanced sulfur resistance, achieving a T 50 —the temperature at which 50 % CH 4 conversion occurred—of 361 °C after sulfation with 100 ppm SO 2 . Moreover, Ce 3 /Pd@MFI maintained sulfur-resistant stability for 110 h, far surpassing Pd@MFI and Pd/Al 2 O 3 , which rapidly deactivated upon exposure to SO 2 for bare 1 h. Furthermore, we proposed a redox-atmosphere switching method to regenerate sulfated CeO 2 protective species, thereby enabling the Ce x /Pd@MFI catalysts to maintain durable sulfur tolerance. The broad applicability of the OXZEO design was further confirmed in CO oxidation : Ce 3 /Pd@MFI remained stable under high SO 2 concentrations during CO oxidation. This work establishes a paradigm for engineering sulfur-resistant palladium catalysts via synergistic spatial confinement and protective-site incorporation, offering critical insights for the development of robust emission-control catalysts in sulfur-rich environments.
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SEPARATION AND PURIFICATION TECHNOLOGY
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2026
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IF 9.1
Haotian Li,Junjie Zhou,Qifan Zhao,Yuchen Yan,Chenwei Wang,Kaijie Li,Haocheng Li,Hongfeng Yin,Youhao Xu
Isoprene is an important chemical raw material in the synthetic rubber and fine chemical industries. In this work, an MFI zeolite membrane reactor (ZMR) was designed for the one-step dehydrogenation of isopentane to isoprene. By selectively removing H 2 , the ZMR overcame thermodynamic equilibrium, thereby significantly enhancing conversion over a Pt-Sn/γ-Al 2 O 3 catalyst. The influence of reaction temperature, pressure, and weight hourly space velocity (WHSV) on the performance of the MFI ZMR was investigated. In a traditional packed-bed reactor, the isopentane conversion was 22.5%, and the isoprene yield was less than 2% at 400 °C, 100 kPa pressure, and a WHSV of 0.50 h −1 . In stark contrast, the isopentane conversion and isoprene yield in the MFI ZMR reached 38.7% and 16.0%, respectively. Furthermore, the MFI ZMR demonstrated stable operation during prolonged testing under optimized conditions. These results highlight the feasibility of the MFI ZMR in this study for the one-step production of isoprene from isopentane dehydrogenation.
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SEPARATION AND PURIFICATION TECHNOLOGY
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2026
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IF 9.1
Hanlu Wang,Guodong Zhang,Xingming Zhang,Shuisen He,Rujin Zhou,Xingye Zeng,Yanbin Jiang
The morphology and microstructure of zeolite membranes are crucial for improving their separation performance. This can be achieved by creating a thin and uniform seed layer, which can then be intergrown into a continuous and dense membrane. Herein, we show a simple vacuum-filtration method to provide closely packed MFI zeolite crystal seed layers on porous substrates (α-Al 2 O 3 ). Then, a continuous, dense, and twin free MFI zeolite membrane was rapidly prepared based on the pre-set crystal seed layer using the microwave-assisted secondary growth method. XRD confirmed the high crystallinity of the prepared MFI zeolite membranes, with a crystal preferred orientation (CPO) index of 0.91, demonstrating excellent b -axis orientation. In the pervaporation separation experiments of xylene isomers (PX/OX), the as-prepared membrane exhibited superior separation performance at 90 °C and 90 kPa. The permeation flux and separation factor were 1931.8 g m −2 h −1 and 4.74, respectively, which were significantly better than MFI zeolite membranes prepared by traditional hydrothermal methods. Quantum chemical calculations further revealed the screening mechanism, where PX was more likely to diffuse through the MFI channels due to its smaller molecular size and weaker adsorption energy. This work provides new insights for the development of energy-efficient and high-performance xylene isomer separation membrane materials.
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Journal of Energy Chemistry
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2022
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IF 13.599
Chenguang Wang,Chengyan Wen,Zheng Liang,Zhipeng Tian,Qian Jiang,Yuhe Liao,Xunzhu Jiang,Lungang Chen,Qiying Liu,Longlong Ma,Michiel Dusselier
Direct conversion of syngas to aromatics has great potential to decrease fossil fuel dependence. Here, a unique structured hybrid catalyst composed of Fe 3 O 4 nanoparticles intimately dispersed inside an acidic zeolite is developed. 1 to 4 nm sized Fe 3 O 4 nanoparticles end up evenly dispersed in an acidic and slightly mesoporous Al-ZSM-5 based on Fe 3 O 4 restructuring during co-hydrothermal synthesis using organosilane modification. A very high aromatic productivity of 214 mmol aromatics h −1 g Fe −1 can be obtained with a remarkable 62% aromatic selectivity in hydrocarbons. This catalyst has excellent sintering resistance ability and maintains stable aromatics production over 570 h. The synthetic insights that postulate a mechanism for the metastable oxide-zeolite reorganization during hydrothermal synthesis could serve as a generic route to sinter-resistant oxide-zeolite composite materials with uniform, well-dispersed oxide nanoparticles in close intimacy with - and partially confined in - a zeolite matrix.
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RSC Advances
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2022
·Vol. 12
·期 25
·16131-16140
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IF 4.036
Qiu-Ping He,Ying-Ying Wang,Peng-Fei Wang,Xiao-Ming Dou
Zeolite–polymer composite membranes have become promising and effective materials for the pervaporative separation of liquids, especially for isomeric mixtures. In this paper, silicalite-1/PDMS composite membranes have been used to investigate the separation of dichlorobenzene (DCB) isomers via pervaporation for the first time. Silicalite-1 zeolites modified by the silane coupling agent, NH3–C3H6–Si(OC2H5)3, have been incorporated into polydimethylsiloxane (PDMS). Then, the silicalite-1/PDMS composite membranes have been successfully prepared on porous polyvinylidene fluoride (PVDF) supports. The morphology and structure of the silicalite-1 zeolites and silicalite-1/PDMS composite membranes have been characterized by XRD, FTIR, SEM and BET techniques. The results show that the modified silicalite-1 zeolite particles have smaller pore sizes dispersed more uniformly in the active layers of the silicalite-1/PDMS composite membranes and present fewer aggregation and pinholes formed by the accumulation of zeolite particles. The silicalite-1/PDMS composite membranes are all dense and continuous with good homogeneity. To evaluate the pervaporative separation performance of the DCB isomers, the unmodified and modified silicalite-1/PDMS composite membranes have been further tested in single-isomer and binary-isomer systems at 60 °C. The modified silicalite-1/PDMS composite membranes present higher DCB isomer separation factors. The separation factors of the modified silicalite-1/PDMS composite membranes in the binary-isomer systems for p-/o-DCB and p-/m-DCB are 3.53 and 5.63, respectively. The permeate flux of p-DCB through the modified silicalite-1/PDMS composite membranes in the p-/o-DCB binary-isomer system is 116.7 g m−2 h−1 and in the p-/m-DCB binary-isomer system, it is 93.5 g m−2 h−1. The result provides a new approach towards the pervaporative separation of DCB isomers from their mixture for future industrialization applications.
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MICROPOROUS AND MESOPOROUS MATERIALS
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2020
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IF 4.551
Haoyang Zhang,Xiaotong Yang,Xiaojing Song,Xinyu Chang,Mingjun Jia
A series of tungsten-tin bimetallic MFI type zeolites (WSn-MFI) with different Sn and W contents were hydrothermally synthesized using tetrapropyl ammonium hydroxide (TPAOH) as a template and polypyrrolidone as a co-surfactant. Tetraethylorthosilicate (TEOS), ammonium tungstate hydrate and tin (IV) chloride pentahydrate were used as the Si, W and Sn sources, respectively. The resultant samples were characterized by various techniques, and were evaluated as catalysts for the epoxidation of cyclohexene with hydrogen peroxide. The results reveal that all the W–Sn bimetallic zeolites have the typical MFI structure, and their relative crystallinities and morphologies change somewhat with the variety of W and Sn contents. Both the isolated framework SnO 4 species and the extra-framework SnO 2 species could be detected in all WSn-MFI samples, while only trace amount of extra-framework W species are present inside the channels/cages of the bimetallic zeolites. Compared with the monometallic zeolites of W-MFI and Sn-MFI, the bimetallic WSn-MFI zeolites exhibit much higher catalytic activity for the epoxidation of cyclohexene. Of these, the sample named WSn-MFI-a could efficiently convert cyclohexene to the corresponding epoxide with a high yield of 79% under an optimized reaction condition. A synergistic effect between the W and Sn species should play critical role in improving the catalytic activity and the epoxide selectivity of the bimetallic zeolite catalysts.
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