JOURNAL OF MEMBRANE SCIENCE
·
2017
·
IF 6.035
Li Peng,Xiaohan Xu,Xun Yao,Hua Liu,Xuehong Gu
A series of novel hierarchical ZSM-5 zeolite membranes with tunable mesopore sizes have been prepared successfully by using amphiphilic organosilane 3-[(trimethoxysilyl) propyl]octyldimethyl-ammonium chloride (TPOAC) as the mesogenous template and part of the Si source. The effects of several synthesis parameters, such as the TPOAC/SiO 2 ratio, synthesis temperature and crystallization time, on the microstructures and rejection performance of the hierarchical ZSM-5 zeolite membranes were systematically investigated. Multiple techniques, such as XRD , SEM, N 2 adsorption techniques, TEM, IR, 13 C MAS NMR and 29 Si MAS NMR were employed for the characterizations. The filtration of dextran in water shows that the membranes have molecular weight cutoff (MWCO) ranging from 9500 to 943,000, corresponding to the molecular size in the range of 4.5–37 nm. The sharp increase in the rejection of dextran with the increase of molecular weight indicated narrow pore size distribution of the membrane. These results show that the hierarchical mesoporous ZSM-5 zeolite membranes have a great potential for ultrafiltration with high performance.
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高影响因子
PETROLEUM SCIENCE AND TECHNOLOGY
·
2017
·
IF 0.655
Lanyu Xing,Zhenhao Wei,Zhenhao Wen,Xuedong Zhu
Hierarchical and conventional ZSM-5 zeolites were synthesized through steam-assisted crystallization approach using acid-treatment kaolin clay as the silica and aluminium sources. The samples were characterized by XRD, SEM, NH3-TPD, N2-physisorption and TG techniques. The results showed that hierarchical ZSM-5 had rich mesopores and bigger specific surface. In conversion of methanol to aromatics, hierarchical and conventional ZSM-5 zeolites showed higher selectivity for aromatics compared with commercial ZSM-5. Under the conditions of 450 °C, 0.15 MPa, the synthesized hierarchical ZSM-5 showed longest lifetime of 380 h, which was 2 and 6 times than those of conventional and commercial ZSM-5, respectively.
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高影响因子
MATERIALS CHEMISTRY AND PHYSICS
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2017
·
IF 2.084
Yisong Wang,Tao Du,Ziyang Qiu,Yanli Song,Shuai Che,Xin Fang
Mesoporous ZSM-5 zeolite as the adsorbent supporting material was synthesized from rice husk ash (RHA), and then impregnated with polyethylenimine (PEI) for amine functional modification. A series of adsorbents (ZSM-5-PEI-X) with different PEI loading ratios were characterized by XRD , FTIR , TGA/DTG, nitrogen adsorption-desorption, SEM and EDX techniques. The measurement of the adsorption capacity at different temperatures was indicated that ZSM-5-PEI-30 had the highest adsorption capacity at 120 °C (1.96 mmol/g). The experimental data were fitted by adsorption kinetic models and isotherm models, indicated that fractional-order model and the Dual-site langmuir model can be used to describe the adsorption mechanism and predict the adsorption performance. The high CO 2 adsorption selectivity and regeneration stability suggested that this adsorbent is a potential candidate in the adsorption and separation of CO 2 in industrial flue gas .
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BioEnergy Research
·
2013
·Vol. 6
·期 4
·1173-1182
·
IF 4.25
Shao Shanshan,Zhang Huiyan,Xiao Rui,Shen Dekui,Zheng Jian
The conversion of three major biomass derivates was conducted in a quartz tubular fixed bed reactor over a ZSM-5 catalyst. As the model compounds of polyols, saturated furans and unsaturated furans, ethylene glycol (EG), tetrahydrofuran (THF) and furan were pyrolyzed to find out the influence of chemical structure on the catalytic characteristics. The effect of pyrolysis temperature (400 ∼ 650 °C), weight hourly space velocity (2.9 ∼ 15.5 h −1 ) and partial pressure (2.12 ∼ 20.49 Torr) on the feed conversion, product yield and selectivity were investigated. The hydrogen to carbon effective ratio (H/C eff ) was referred to, to analyze the capacity of biomass derivates being converted to chemicals (olefins and aromatics). The results showed that the existence of rings and C=C had great effect on the catalytic characteristics. The conversion of furan was much lower (mainly less than 60 %) than that of EG and TH,F which were close to 100 %. It was also found that the chemical yield of THF was slightly more than that of EG, which can be attributed to its relative higher H/C eff of 1.5. Furan produced the highest coke yield, which was more than 15 %, whereas that of EG and THF was only around 5 %. The serious coking of furan led to the lowest chemical yield, which was less than 35 %. This study paves a way for the mechanism study on catalytic characteristics of biomass-derived feedstocks over zeolite catalysts.
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高影响因子
ACS Catalysis
·
2018
·
IF 11.384
Yuchao Chai,Sihang Liu,Zhi-Jian Zhao,Jinlong Gong,Weili Dai,Guangjun Wu,Naijia Guan,Landong Li
Metal nanoparticles encapsulated in zeolite have been recently developed as a special type of catalyst that shows significant advantages in activity, shape-selectivity, and stability over conventional supported catalysts. The selectivity modulation of encapsulated nanoparticle catalysis by the zeolite microenvironment is theoretically possible but not addressed yet. Here, we report the in situ encapsulation of sub-nanometric palladium species within MFI-type zeolites, which exhibit high activity and good stability in the hydroconversion of furfural as a model reaction of biomass upgrading. Remarkably, different products, e.g., furan, furfural alcohol, and 1,5-pentanediol, from furfural hydroconversion can be obtained when silicalite-1, Na-ZSM-5, and H-ZSM-5 are employed as hosts of palladium nanoparticles, respectively. Density functional theory calculations and spectroscopy investigations reveal that both the adsorption of furfural and the activation of hydrogen are significantly affected by the zeolite microenvironment, leading to different reaction pathways. Our work presents an elegant example of catalytic selectivity modulation of encapsulated metal nanoparticles by tuning the zeolite microenvironment.
研究领域:
催化
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材料科学
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化学工程
·
纳米技术
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高影响因子
FUEL
·
2024
·
IF 6.7
Renjie Ji,Defu Yin,Yao Chen,Like Ma,Fanglin Lv,Yuhao Zhang,Zhen Jia,Jingyun Zhang,Mingya Liu,Shitao Yu,Yue Liu
A core–shell catalyst mZSM-5@SO 4 2- /mSiO 2 composed of mZSM-5 core and SO 4 2- /mSiO 2 shell was prepared by the soft template method. Core-shell structure could promote the building of Brønsted -Lewis (B-L) acids interface and significantly improve the synergistic effect of B-L. In this paper, the Brønsted/Lewis (B/L) of mZSM-5@SO 4 2- /mSiO 2 was targeted regulating by innovatively introducing Brønsted acid (BA) sites into the shell. The optimal mZSM-5@SO 4 2- /mSiO 2 catalyst (B/L = 0.142) could achieve 72.1 % furfural yield at 140 ℃ for 1 h. In addition, 70.2 % furfural yield could be obtained after the catalyst was recycled and regenerated for 5 times. Combining In-situ IR and 13 C NMR, the reaction path was revealed in detail: xylose was first isomerized to xylulose and then dehydrated to furfural. This paper provides a research idea for the directional regulation of dual active sites of cascade reaction catalysts.
研究领域:
催化化学
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生物质转化
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高影响因子
FUEL
·
2012
·
IF 3.248
Tao He,Yuxin Wang,Pengjie Miao,Jianqing Li,Jinhu Wu,Yunming Fang
Deep hydrogenation of aromatics is an important reaction in modern oil refinery. The key of an aromatic hydrogenation unit is high active, sulfur resistant hydrogenation catalyst. In this paper, the catalytic performance of a newly developed hydrogenation catalyst, platinum supported on mesoporous ZSM-5 (Pt/MZ-5), was tested in naphthalene (model compound of light cycle oil) hydrogenation. Pt/ZSM-5 and Pt/Alumina were used as reference. In some experiments, dibenzothiophene (DBT) was added to test the sulfur tolerance of catalysts. In the absence of DBT, Pt/MZ-5 and Pt/Alumina showed much higher hydrogenation activities and decalin selectivity than Pt/ZSM-5. The selectivity to decalin exceeds 97% over Pt/MZ-5 at temperature range between 523 and 573 K. Furthermore, Pt/MZ-5 shows better sulfur resistance than that of Pt/Alumina. In the presence of 3000 ppm dibenzothiophene, the selectivity of decalin over Pt/MZ-5 was only slightly dropped to 89.4% at 573 K, which is much higher than that of Pt/Al 2 O 3 (51.4%). The excellent catalytic performance and sulfur tolerance of Pt/MZ-5 were attributed to the combination of high acidity and mesoporous structure in MZ-5.
研究领域:
催化化学
·
石油炼制工程
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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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高影响因子
Catalysis Science & Technology
·
2018
·Vol. 8
·期 17
·4338-4348
·
IF 5.365
Xiaoli Yang,Xiong Su,Binglian Liang,Yaru Zhang,Hongmin Duan,Junguo Ma,Yanqiang Huang,Tao Zhang
The oxide–zeolite process has been attracting widespread attention due to its promising performance in syngas conversion to hydrocarbons with high selectivity and stability. Here, a composite catalyst containing Zn–Cr oxide and ZSM-5 zeolite provides a competitive option in the one-step conversion of syngas into C5+ hydrocarbons. In order to figure out the influence of the pore structure and acidity of zeolite on the oxide–zeolite process, alkali treatments on ZSM-5 are carried out. The treated ZSM-5 shows increased selectivity for gasoline fractions. With a set of structural and morphological characterization techniques, the formation of a hierarchical porous structure is demonstrated, which is favorable for the diffusion of heavy products. Furthermore, an increase in the number of Lewis acid sites, acting as the main active sites for the polymerization, cyclization and aromatization reactions, also contributes to the promotion of C5+ hydrocarbon production. It must be noted, however, that a certain amount of Brønsted acid sites is necessary for the tandem transformation of CH3OCH3 intermediates, which may further affect the CO conversion.
研究领域:
催化化学
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材料科学
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高影响因子
GREEN CHEMISTRY
·
2025
·Vol. 27
·期 6
·1838-1857
·
IF 9.2
Li Yang,Bonan Liu,Yingying Zhao,Zijian Zhang,Hanyu Wu,Minyi He,Chao Tang,Jun Zhao,Yu Fan,Wangjing Ma
Modern chemists dream of a low-temperature bioethanol dehydration to ethylene process promoted by biomaterial-based catalysts, which would be without doubt an energy-saving, sustainable achievement in green chemistry. However, limitations on catalytic activity and competition from exothermic side reactions have always been an insurmountable gap. Herein, a microwave-assisted pathway employing biochar-based catalysts was designed to effectively dehydrate ethanol into ethylene at temperatures lower than 100 °C. Either biochar (BC) or phosphoric acid-modified derivate (HBC) was synthesized from bamboo powder through a simple one-step decomposition. ZSM-5/MOR composite zeolite was further introduced to form HBC-2-ZSM-5/MOR hybrid catalysts, which could effectively prevent the formation of diethyl-ether and enhance the production of ethylene. With a microwave input power and reaction temperature as low as 10 W and 82 °C, ethanol (WHSV = 2 h−1) could be completely converted on the HBC-2-ZSM-5/MOR (1.5) catalyst with almost 100% ethylene selectivity. Similar results were obtained in the conversion of bioethanol (model), Chinese liquor and beer, pointing to the wide applicability of this strategy. Investigation of the potential mechanism found that weak acidity, special structure and P-modification characteristics can effectively inhibit the formation of diethyl ether by-products, oligomerization and the coking process, which is conducive to promoting the selective conversion of ethanol to ethylene. This work has blazed another trail for low-temperature ethanol to ethylene by combining the advantage of microwave heating with precise tailoring of biochar-based catalysts, all for a better future life with green chemistry.
研究领域:
绿色化学
·
催化材料科学
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高影响因子
RSC Advances
·
2024
·Vol. 14
·期 10
·6502-6507
·
IF 3.9
Jiaqi Wang,Kaihong Liu,Jingjing Zhao,Xiuping Li,Bolin Yin,Bo Jiang,Hexing Li
Direct CO2 hydrogenation to value-added chemicals is a promising path toward realizing the “carbon-neutral” goal. However, controlling the selectivity of CO2 hydrogenation toward desired products (e.g., CO and CH4) using non-precious metal-based catalysts is important but challenging. It is imperative to explore catalysts with high activity and stability. Herein, boron-doped cobalt nanoparticles supported on H-ZSM-5 were devised for CO2 hydrogenation to produce CO in a gas–solid flow system. Our results demonstrate that boron doping not only increases the CO2 adsorption capability of the catalyst but also optimizes the electronic state of Co for CO desorption during hydrogenation process. As a result, the boron-doped cobalt catalysts displayed an enhanced CO selectivity of 94.5% and a CO2 conversion rate of 45.6%, which is much higher than that of Co-ZSM-5 without boron doping. This study shows that the strategic design of metal borides is important for controlling the selectivity of desired products in the CO2 hydrogenation reaction.
研究领域:
催化化学
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材料科学
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环境科学
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DOI
PubMed
高影响因子
DALTON TRANSACTIONS
·
2020
·Vol. 49
·期 21
·7258-7266
·
IF 4.174
Guanqun Zhang,Yaqi Fan,Ju Huang,Lijin Wang,Chengguang Yang,Meng Lyu,Haiming Liu,Yanhang Ma
The increasing demands for catalysts with improved accessibility to reactants call for a rational synthesis of nanosized zeolites. Herein we developed a facile approach for highly crystalline MFI-type (Silicalite-1 and ZSM-5) and beta zeolites with variable Si/Al ratios and high yield. This was achieved by kinetically decoupling the nucleation from the growth process of the zeolites in a highly concentrated gel system via a temperature-staged treatment. The carefully controlled low-water environment ensures only nucleation in stage I (aging), and hence the generation of abundant nuclei for the subsequent rapid crystallization within a self-confined space at stage II (growth). The method, without using expensive templates or additives, allows the syntheses of nanosized, well-isolated ZSM-5 (Si/Al = 100–∞, 36–88 nm, yield >85%) and Beta (Si/Al = 25–100, 21–66 nm, yield >95%). The ultra-small crystal size endows ZSM-5 zeolites with good catalytic activity, product selectivity and remarkably longer lifetime in methanol conversion reactions.
研究领域:
化学工程
·
材料科学
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PubMed
高影响因子
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