RSC Advances
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2016
·Vol. 6
·期 103
·101365-101371
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IF 3.289
Guang Xiong,Jinpeng Yin,Jiaxu Liu,Xiyan Liu,Zhendong Guo,Liping Liu
Nano-sized ZSM-5 aggregates with interparticle mesopores was synthesized by an aerosol-assisted method. The amorphous aluminosilicate powder was used as a precursor, which was obtained by an aerosol process from an aqueous solution of the silicon and aluminium sources. The amorphous powder was crystallized in an autoclave with the structure-directing agent tetrapropylammonium hydroxide. No extra water was added in this step. The synthesis was performed in an extremely dense system, hence the amount of both template and waste water can be significantly reduced. The formation of the nanocrystalline MFI zeolite is mainly based on the liquid phase transformation in a supersaturation system. The nano-sized ZSM-5 aggregates were composed of nanocrystals with a size of 50–100 nm. Compared with the ZSM-5 zeolite synthesized by a conventional hydrothermal method, the nano-sized ZSM-5 aggregates exhibits a higher BET surface area, external surface area, and total pore volume and better Al species distribution. This nanocrystalline ZSM-5 zeolite shows a higher catalytic activity and stability in catalytic cracking of 1,3,5-triisopropylbenzene.
研究领域:
材料科学
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催化化学
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DOI
高影响因子
Journal of Inorganic and Organometallic Polymers and Materials
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2024
·
IF 3.9
Liu Hao,Wang Yanlin,Yuan Hong,Luo Wenbo
Nanoscale ZSM-5 zeolites (NZSM-5) having different crystal sizes and Si/tetrapropylammonium hydroxide (TPAOH) molar ratios were synthesized using a hydrothermal method. These materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N 2 adsorption–desorption. The results showed that each zeolite was highly crystalline regardless of the Si/TPAOH ratio and that the Brunauer–Emmett–Teller surface areas were in the range of 329−392 m 2 /g. The random aggregation of these nanoparticles resulted in the formation of numerous intergranular mesopores. These NZSM-5 zeolites were applied to the catalytic cracking of oleic acid to prepare light olefins and light aromatics using a laboratory-scale fixed bed reactor. The zeolite having a Si/TPAOH ratio of 10/5 showed the best catalytic activity and provided light olefins yield of 55% and selectivity of BTX in liquid phase products of 18%, respectively, at 500 °C. The small crystal size and abundant intergranular mesopores in this specimen resulted in shorter diffusion paths and an increase in the external specific surface area that both inhibited coke deposition and ensured accessible acid sites. Graphical Abstract
研究领域:
化学工程
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材料科学
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DOI
高影响因子
ADVANCED POWDER TECHNOLOGY
·
2024
·
IF 4.2
Hu Wen,Yuxin Li,Haitao Yin,Wei Wang,Zhengchao Jin,Shunyu Han,Nanzhe Jiang
The conversion of natural clay to crystalline zeolites has been the subject of considerable interest from both academic and industrial circles. We present an effective strategy for converting kaolin to ZSM-5 zeolite, addressing the issue of reduced mesopore formation in conventional nano-ZSM-5 aggregates due to close-packing. This strategy utilizes kaolin as the sole source of silicon and aluminum, and by decoupling the nucleation and growth of ZSM-5 crystals, loosely stacked nano-H-ZSM-5 aggregates with high crystallinity crystals can be synthesized in a solid-like system by employing a tiny amount of TPAOH (TPAOH/SiO 2 = 0.064). The resulting nano-H-ZSM-5 aggregates exhibited high specific surface area (405.66 m 2 /g), high mesopore volume (0.64 cm 3 /g), and superior catalytic activity. This strategy offers a novel approach to the cost-effective synthesis of nano-H-ZSM-5 aggregates suitable for industrial applications.
研究领域:
化学工程
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材料科学
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催化反应
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DOI
高影响因子
Catalysis Science & Technology
·
2017
·Vol. 7
·期 8
·1776-1791
·
IF 5.773
Yanming Jia,Junwen Wang,Kan Zhang,Shibin Liu,Guoliang Chen,Yufei Yang,Chuanmin Ding,Ping Liu
ZnSiF6-modified nano-sized HZSM-5 zeolites (NZ2, NZ3 and NZ4 catalysts) were prepared and investigated as catalysts for the conversion of methanol to aromatics. Moreover, the ZnNZ1 catalyst, prepared by ion exchange using zinc nitrate, was also introduced as a reference sample. The effects of modification on the framework, textural properties and acidity of the parent nano-sized HZSM-5 zeolite (NZ1) were investigated by XRD, FT-IR, 29Si MAS-NMR, SEM, N2 adsorption–desorption, ICP, NH3-TPD, infrared spectroscopy of adsorbed pyridine (Py-IR), UV-vis spectra, X-ray photoelectron spectroscopy (XPS) and n-butylamine and tert-butylamine titration. The results showed that the amount of total acid sites, especially the external surface acid sites of the NZ2, NZ3 and NZ4 catalysts, significantly decreased, which may largely be attributed to the passivation effect of SiF62− on the surface acidity of the parent NZ1 catalyst. Moreover, the amount of Lewis acid sites (L acid sites) increased, whereas the amount of Brønsted acid sites (B acid sites) obviously decreased with the introduction of zinc species. The emergence of new Zn-Lewis acid sites (⊖ZO⋯H⋯O–Zn⊕ species) was beneficial to improving the selectivity to BTX (benzene (B), toluene (T) and xylene (X)) due to their high activity for dehydroaromatization. The FT-IR spectra in the OH− vibration region and the 29Si MAS-NMR spectra show that the treatment of ZnSiF6 could effectively repair partial lattice defects of zeolite and could thus improve the catalyst stability. TG analysis of all the deactivated catalysts showed that the coke amount and the average rate of coke formation decreased over NZ2, NZ3 and NZ4 catalysts, and this may largely be ascribed to their lower surface acidity. The catalytic performance of these materials on the conversion of methanol to aromatics showed that the NZ3 catalyst had the highest selectivity to BTX of about 51.3% and the longest catalytic lifetime of about 234 h under the operating conditions of T = 425 °C, p = 0.1 MPa and WHSV = 0.8 h−1. The improvement in the selectivity to BTX and the catalyst lifetime of the NZ3 catalyst could be ascribed to the synergistic effect among the Zn-Lewis acid sites (⊖ZO⋯H⋯O–Zn⊕ species), external surface acidity and intact framework structure.
研究领域:
催化化学
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材料科学
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DOI
高影响因子
FUEL
·
2019
·
IF 5.128
Chengchao Liu,Yao Chen,Yanxi Zhao,Shuai Lyu,Liang Wei,Xin Li,Yuhua Zhang,Jinlin Li
ZSM-5 zeolite is usually used to modify the product selectivity for Fischer–Tropsch synthesis (FTS). Here, we prepared a nano-ZSM-5 zeolite with a particle size of 80 nm. This zeolite was used as a support to prepare bifunctional Co-based FTS catalysts by incipient wetness impregnation [using water as a solvent (W-Co/H-ZSM-5) or alcohol as a solvent (A-Co/H-ZSM-5)] and an ultrasound-assisted impregnation method (U-Co/H-ZSM-5). These catalysts were characterized by X-ray diffraction (XRD), N 2 -physical absorption, H 2 temperature-programmed reduction (H 2 -TPR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The FTS catalytic performances of all catalysts were compared in a fixed-bed reactor. Characterization data revealed that the U-Co/H-ZSM-5 catalyst had the best cobalt dispersion, resulting in the most stable CO conversion. Moreover, the nanoscale relationship between the activity and acid sites enhances the hydrocracking ability, increasing the liquid fuel selectivity from 49.7% to 67.8% (no C 20+ product was detected for U-Co/H-ZSM-5) for a reaction at 503 K. In addition, the CH 4 selectivity increases as the reaction temperature increases from 483 K to 513 K, which is beneficial for producing liquid fuel products (67.8%) at a reaction temperature of 503 K.
研究领域:
催化化学
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能源材料科学
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DOI
高影响因子
RSC Advances
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2020
·Vol. 10
·期 50
·29618-29626
·
IF 3.119
Yanming Jia,Qinghua Shi,Junwen Wang,Chuanmin Ding,Kan Zhang
Hierarchical nano-ZSM-5 zeolites (Z5-X) with different grain sizes were synthesized by varying amounts of 3-glycidoxypropyltrimethoxysilane (KH-560) in the hydrothermal synthesis strategy. Moreover, the conventional ZSM-5zeolite(Z5), which was prepared without KH-560, was used as the reference sample. The crystalline phases, morphologies, porous characteristics, Si/Al molar ratios and acidic properties of all fresh catalysts were characterized using the X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM), N2 adsorption–desorption, inductively coupled plasma atomic emission spectroscopy (ICP) and temperature programmed desorption of ammonia (NH3-TPD) techniques. Results show that the grain size and strong acid amount of zeolite decreased with the increasing amount of KH-560. The micropore surface areas and the corresponding volume of Z5-X changed less compared with Z5. Consequently, the high shape-selectivity of zeolite was preserved well under the addition of KH-560. However, the mesopore surface areas and the corresponding volume increased significantly with the increasing amount of KH-560. Benefiting from the abundant hierarchical structure, the Z5-X catalysts exhibited a larger coke capacity than the Z5 catalyst. The coke depositions of all the deactivated catalysts were characterized by the thermogravimetric technique (TG), and the results are indicative of the decreased average rate of coke deposition with an increasing amount of KH-560, which could result from the gradually reduced strong acid amount and the nano-sized crystallites. The catalytic performance of methanol-to-aromatics (MTA) indicates that the Z5-0.12 catalyst exhibited higher catalytic activity and selectivity of BTX as the reaction was prolonged, which could result from the synergistic effect among the proper strong acid amount, the smaller zeolite grain size, and the abundant hierarchical structure.
研究领域:
化学工程
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材料科学
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DOI
PubMed
高影响因子
CATALYSIS COMMUNICATIONS
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2012
·
IF 2.986
Linping Sun,Xinwen Guo,Guang Xiong,Xiangsheng Wang
The ethylation of coking benzene with ethanol over nano-sized ZSM-5 zeolites modified with Y 2 O 3 , La 2 O 3 and CeO 2 was investigated in a fixed-bed reactor. Nano-sized ZSM-5 zeolite modified with Y 2 O 3 was more stable than the other two samples during the reaction. The results from NH 3 -TPD, Py-IR, and TG-DTA show that the strong Brønsted acid sites were eliminated, consequently suppressing coke deposits during the reaction. Combined with the results from 1 H NMR and 129 Xe NMR spectra, it is concluded that the hydrated Yttrium ions with small size reached deep location in zeolite channel.
研究领域:
化学工程
·
催化科学
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DOI
高影响因子
CRYSTENGCOMM
·
2021
·Vol. 23
·期 15
·2793-2800
·
IF 3.545
Xueshuai Chen,Rongli Jiang,Yu Gao,Zihan Zhou,Xingwen Wang
In this work, nano-ZSM-5 zeolite with superior catalytic properties was synthesized from LAPONITE® as one of the Si sources by a dry gel conversion (DGC) method, and its crystallization mechanism was investigated as well. The properties of ZSM-5(Z-L) synthesized from LAPONITE® as one of the Si sources and ZSM-5(Z-T) synthesized from tetraethylorthosilicate (TEOS) as a single Si source have been compared. The results show that LAPONITE® is an important factor for the formation of nanocrystals with high crystallinity. It can not only act as the Mg and Si source for the zeolite synthesis but also exert a “confined space” effect to control ZSM-5 crystal growth. The Z-L sample with nanosized crystals can shorten the reactant and product diffusion path length, which seriously improves diffusion efficiency and results in longer catalytic stability. This work provides a novel and efficient route for synthesis of nano-ZSM-5 zeolite.
研究领域:
材料科学
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化学工程
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催化
·
纳米技术
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DOI
高影响因子
危险品化学品经营许可证（带存储）