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New approaches to vibrational spectroscopy of zeolite catalysts: a perspective

《化学科学与工程前沿(英文)》 doi: 10.1007/s11705-024-2474-5

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Control of aluminum distribution in ZSM-5 zeolite for enhancement of its catalytic performance for propane

《化学科学与工程前沿(英文)》 2024年 第18卷 第8期 doi: 10.1007/s11705-024-2439-8

摘要: Regulation of aluminum distribution in zeolite framework is an effective method for improving its catalytic performance for propane aromatization. Herein, we found that recrystallization and post-realuminization of ZSM-5 cannot only create hollow structures to enhance the diffusion ability, but also adjust the content and position of paired aluminum species in its framework. Various characterizations results confirmed that increase of paired aluminum content and inducement of more aluminum atoms sited in the intersection cavity are beneficial to the formation of aromatic products in propane aromatization. As a result, the hollow-structured ZSM-5 zeolite with more paired aluminum (H-200-hollow) showed higher propane conversion and aromatics selectivity than other samples at the same conditions. The catalytic performance of H-200-hollow can be further improved by ion-exchanging with a small amount of Ga(III) species. The propane conversion and aromatics selectivity of Ga-200-hollow reached as high as 95% and 70%, respectively, at 540 °C and 1 atm.

关键词: propane aromatization     zeolite     aluminum distribution     recrystallization and post-realuminization    

Factors affecting the formation of zeolite seed layers and the effects of seed layers on the growth ofzeolite silicalite-1 membranes

ZHANG Xiongfu, WANG Jinqu, LIU Hai′ou, WANG Anjie

《化学科学与工程前沿(英文)》 2007年 第1卷 第2期   页码 172-177 doi: 10.1007/s11705-007-0032-6

摘要: The present study investigates the formation of silicalite-1 seed layers on a porous carbon support of 0.5 μm pore size and α-A1O supports with different pore sizes (0.1 μm and 4 μm) via the slip-casting technique. The effects of support property, seed size and solvent on the formation of seed layers were investigated in detail. The growth of silicalite-1 membranes on different seeded supports by hydrothermal synthesis was also evaluated. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterizations indicate that a continuous seed layer can be obtained on the smooth support of 0.1 μm pore size by using any seed of 100 nm, 600 nm or 2.2 μm in size, whereas, on the coarse supports with either 0.5 μm or 4 μm pore size, a continuous seed layer cannot be formed using the above seed sizes and the same seeding time. At a longer contact time, a seed layer can also be formed using 100 nm seed on the supports with larger pore size. However, the layer is not uniform and smooth. For a hydrophobic porous carbon support, seeding ethanol suspension, which has weak polarity, favors the formation of a continuous seed layer. The seed layers and membranes grown from the smaller seed are more uniform and continuous and possess smoother surfaces than those from the larger seed. The seed layer and respective grown membrane formed from nanosized seed (100 nm) are the most uniform and compact. With this method of seeded secondary synthesis of zeolite membranes, the quality of a membrane mainly depends on the quality of the seed layer.

关键词: silicalite-1     α-A1O     growth     seeding ethanol     quality    

Photocatalytic degradation of omethoate using NaY zeolite-supported TiO

Dishun ZHAO, Jialei WANG, Zhigang ZHANG, Juan ZHANG

《化学科学与工程前沿(英文)》 2009年 第3卷 第2期   页码 206-210 doi: 10.1007/s11705-009-0053-4

摘要: The degradation of omethoate was conducted using H O as oxidant, TiO supported on NaY zeolite as photocatalyst and a 300 W lamp as light source. The effect of the calcination temperature of the photocatalyst, the amount of TiO loaded on NaY zeolite, the photocatalyst amount, the pH value and the radiation time on the degradation ratio of omethoate were investigated. The results show that TiO /NaY zeolite photocatalyst prepared by sol-gel method had good photocatalysis. The photocatalytic optimum oxidation conditions of omethoate are as follows: the calcination temperature of the photocatalyst is 550°C,the amount of TiO loaded on NaY zeolite is 35.2 wt-%, the amount of photocatalyst is 5 g/L, pH=8 and the radiation time is 180 min. Under these conditions, the removal ratio of omethoate is up to 93%.

关键词: TiO2     NaY zeolite     photocatalytic degradation     omethoate    

Synthesis, physicochemical characterizations and catalytic performance of Pd/carbon-zeolite and Pd/carbon-CeO

Zeinab JAMALZADEH, Mohammad HAGHIGHI, Nazli ASGARI

《环境科学与工程前沿(英文)》 2013年 第7卷 第3期   页码 365-381 doi: 10.1007/s11783-013-0520-5

摘要: In this work, xylene removal from waste gas streams was investigated via catalytic oxidation over Pd/carbon-zeolite and Pd/carbon-CeO nanocatalysts. Activated carbon was obtained from pine cone chemically activated using ZnCl and modified by H PO . Natural zeolite of clinoptilolite was modified by acid treatment with HCl, while nano-ceria was synthesized via redox method. Mixed supports of carbon-zeolite and carbon-ceria were prepared and palladium was dispersed over them via impregnation method. The prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller surface area (BET), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric (TG) techniques. Characterization of nanocatalysts revealed a good morphology with an average particle size in a nano range, and confirmed the formation of nano-ceria with an average crystallite size below 60 nm. BET analysis indicated a considerable surface area for catalysts (~1000 m ·g ). FTIR patterns demonstrated that the surface groups of synthesized catalysts are in good agreement with the patterns of materials applied in catalyst synthesis. The performance of catalysts was assessed in a low-pressure catalytic oxidation pilot in the temperature range of 100°C–250°C. According to the reaction data, the synthesized catalysts have been shown to be so advantageous in the removal of volatile organic compounds (VOCs), representing high catalytic performance of 98% for the abatement of xylene at 250°C. Furthermore, a reaction network is proposed for catalytic oxidation of xylene over nanocatalysts.

关键词: Pd/carbon-CeO2     Pd/carbon-zeolite     pine cone     ZnCl2     catalytic oxidation     xylene    

Zeolite-encaged gold catalysts for the oxidative condensation of furfural

《化学科学与工程前沿(英文)》 2024年 第18卷 第8期 doi: 10.1007/s11705-024-2443-z

摘要: The oxidative condensation between renewable furfural and fatty alcohols is a crucial avenue for producing high-quality liquid fuels and valuable furan derivatives. The selectivity control in this reaction process remains a significant challenge. Herein, we report the strategy of confining well dispersed gold species within ZSM-5 structure to construct highly active Au@ZSM-5 zeolite catalysts for the oxidative condensation of furfural. Characterization results and spectroscopy analyses demonstrate the efficient encapsulation of isolated and cationic Au clusters in zeolite structure. Au@ZSM-5(K) catalyst shows remarkable performance with 69.7% furfural conversion and 90.2% furan-2-acrolein selectivity as well as good recycle stability. It is revealed that the microstructure of ZSM-5 zeolite can significantly promote oxidative condensation activity through confinement effects. This work presents an explicit example of constructing zeolite encaged noble metal catalysts toward targeted chemical transformations.

关键词: zeolite     encapsulation     gold     oxidative condensation     furfural    

Metal size effects over metal/zeolite bifunctional catalysts in the selective hydroalkylation of benzene

《化学科学与工程前沿(英文)》 2024年 第18卷 第4期 doi: 10.1007/s11705-024-2406-4

摘要: Bifunctional metal/zeolite materials are some of the most suitable catalysts for the direct hydroalkylation of benzene to cyclohexylbenzene. The overall catalytic performance of this reaction is strongly influenced by the hydrogenation, which is dependent on the metal sizes. Thus, systematically investigating the metal size effects in the hydroalkylation of benzene is essential. In this work, we successfully synthesized Ru and Pd nanoparticles on Sinopec Composition Materials No.1 zeolite with various metal sizes. We demonstrated the size-dependent catalytic activity of zeolite-supported Ru and Pd catalysts in the hydroalkylation of benzene, which can be attributed to the size-induced hydrogen spillover capability differences. Our work presents new insights into the hydroalkylation reaction and may open up a new avenue for the smart design of advanced metal/zeolite bi-functional catalysts.

关键词: size effects     bifunctional catalysts     metal/zeolite     hydroalkylation    

Catalytic fast pyrolysis of Kraft lignin with HZSM-5 zeolite for producing aromatic hydrocarbons

Xiangyu LI, Lu SU, Yujue WANG, Yanqing YU, Chengwen WANG, Xiaoliang LI, Zhihua WANG

《环境科学与工程前沿(英文)》 2012年 第6卷 第3期   页码 295-303 doi: 10.1007/s11783-012-0410-2

摘要: Catalytic fast pyrolysis (CFP) of Kraft lignins with HZSM-5 zeolite for producing aromatics was investigated using analytical pyrolysis methods. Two Kraft lignins were fast pyrolyzed in the absence and presence of HZSM-5 in a Curie-point pyrolyzer. Without the catalyst, fast pyrolysis of lignin predominantly produced phenols and guaiacols that were derived from the subunits of lignin. However, the presence of HZSM-5 changed the product distribution dramatically. As the SiO /Al O ratio of HZSM-5 decreased from 200 to 25 and the catalyst-to-lignin ratio increased from 1 to 20, the lignin-derived oxygenates progressively decreased to trace and the aromatics increased substantially. The aromatic yield increased considerably as the pyrolysis temperature increased from 500°C to 650°C, but then decreased with yet further increase of pyrolysis temperature. Under optimal reaction conditions, the aromatic yields were 2.0 wt.% and 5.2 wt.% for the two lignins that had effective hydrogen indexes of 0.08 and 0.35.

关键词: lignin     catalytic fast pyrolysis     HZSM-5     zeolite     aromatic hydrocarbon    

CuO/zeolite catalyzed oxidation of gaseous toluene under microwave heating

Longli BO, Jianbo LIAO, Yucai ZHANG, Xiaohui WANG, Quan YANG

《环境科学与工程前沿(英文)》 2013年 第7卷 第3期   页码 395-402 doi: 10.1007/s11783-012-0417-8

摘要: The development of a combined process of catalytic oxidation and microwave heating for treatment of toluene waste gas was described in this work. Toluene, a typical toxic volatile organic compound, was oxidized through a fixed bed reaction chamber containing zeolite-supported copper oxide (CuO/zeolite) catalyst mixed with silicon carbide (SiC), an excellent microwave-absorbing material. The target compound was efficiently degraded on the surface of the catalyst at high reaction temperature achieved by microwave-heated SiC. A set of experimental parameters, such as microwave power, air flow and the loading size of CuO etc., were investigated, respectively. The study demonstrated these parameters had critical impact on toluene degradation. Under optimal condition, 92% toluene was removed by this combined process, corresponding to an 80%–90% TOC removal rate. Furthermore, the catalyst was highly stable even after eight consecutive 6-h runs. At last, a hypothetical degradation pathway of toluene was proposed based on the experimental data obtained from gas chromatography-mass spectrum and Fourier transform infrared spectroscopy analyses.

关键词: microwave     catalytic oxidation     CuO/zeolite catalyst     silicon carbide (SiC)     toluene    

Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic

《结构与土木工程前沿(英文)》 2022年 第16卷 第1期   页码 86-98 doi: 10.1007/s11709-021-0793-x

摘要: One of the strategic materials used in earth-fill embankment dams and in modifying and preventing groundwater flow is plastic concrete (PlC). PlC is comprised of aggregates, water, cement, and bentonite. Natural zeolite (NZ) is a relatively abundant mineral resource and in this research, the microstructure, unconfined strength, triaxial behavior, and permeability of PlC made with 0%, 10%, 15%, 20%, and 25% replacement of cement by NZ were studied. Specimens of PIC-NZ were subjected to confined conditions and three different confining pressures of 200, 350, and 500 kPa were used to investigate their mechanical behavior and permeability. To study the effect of sulfate ions on the properties of PlC-NZ specimens, the specimens were cured in one of two different environments: normal condition and in the presence of sulfate ions. Results showed that increasing the zeolite content decreases the unconfined strength, elastic modulus, and peak strength of PlC-NZ specimens at the early ages of curing. However, at the later ages, increasing the zeolite content increases unconfined strength as well as the peak strength and elastic modulus. Specimens cured in the presence of sulfate ions indicated lower permeability, higher unconfined strength, elastic modulus, and peak strength due to having lower porosity.

关键词: plastic concrete     sulfate resistance     natural zeolite     triaxial compression test     SEM     permeability    

Biodiesel production from waste frying oil in sub- and supercritical methanol on a zeolite Y solid acid

Jorge MEDINA-VALTIERRA, Jorge RAMIREZ-ORTIZ

《化学科学与工程前沿(英文)》 2013年 第7卷 第4期   页码 401-407 doi: 10.1007/s11705-013-1354-1

摘要: Waste frying oil (WFO) is a very important feedstock for obtaining biodiesel at low cost and using WFO in transesterification reactions to produce biodiesel helps eliminate local environmental problems. In this study biodiesel was produced from WFO in sub- and super-critical methanol on a zeolite Y solid acid catalyst. The procedure was optimized using a design of experiments by varying the methanol to WFO molar ratio, the reaction temperature, and the amount of catalyst. Typical biodiesel yields varied from 83 to nearly 100% with methyl esters content ranging from 1.41–1.66 mol·L and typical dynamic viscosities of 22.1-8.2 cP. Gas chromatography was used to determine the molecular composition of the biodiesel. The reaction products contained over 82 wt-% methyl esters, 4.2 wt-% free acids, 13.5 wt-% monoglycerides, and 0.3 wt-% diglycerides. The transesterification of WFO with methanol around its critical temperature combined with a zeolite Y as an acid catalyst is an efficient approach for the production of biodiesel with acceptable yields.

关键词: biodiesel     methanol     critical temperature     waste frying oil     zeolite Y    

Effect of seawater salinity on the synthesis of zeolite from coal fly ash

Yanqing YU, Xiaoliang LI, Xiaolan ZOU, Xiaobin ZHU

《环境科学与工程前沿(英文)》 2014年 第8卷 第1期   页码 54-61 doi: 10.1007/s11783-013-0493-4

摘要: A novel method for the synthesis of zeolite was developed in this paper. The synthesis was carried out by hydrothermal activation after alkali fusion and coal fly ash (CFA) was used as raw material with seawater of different salinities. Seawater salinity was varied from 32 to 88 for zeolite crystallization during the hydrothermal process. The results show that seawater salinity plays an important role in zeolite synthesis with CFA during hydrothermal treatment. The products were a mixture of NaX zeolite and hydroxysodalite; seawater salinity more strongly affected the crystallization than the type and chemical composition of the zeolites. The yield of CFA transformed into zeolite gradually rose with the increase in salinity, reaching a transformation rate of 48%–62% as the salinity increased from 32 to 88, respectively. The proposed method allows for the efficient disposal of by-products; therefore, the application of seawater in zeolite synthesis presents promising economic and ecological benefits.

关键词: coal fly ash (CFA)     seawater salinity     zeolite synthesis    

The interaction of the structure-directing agent with the zeolite framework determines germanium distribution

《化学科学与工程前沿(英文)》 2024年 第18卷 第5期 doi: 10.1007/s11705-024-2417-1

摘要: We report results from computational modeling of the relative stability of germanosilicate SCM-15 structure due to different distribution of germanium heteroatoms in the double four-member rings (D4Rs) of the framework and the orientation of the structure directing agent (SDA) molecules in the as-synthesized zeolite. The calculated relative energies of the bare zeolite framework suggest that structures with germanium ions clustered in the same D4Rs, e.g., with large number of Ge–O–Ge contacts, are the most stable. The simulations of various orientations of the SDA in the pores of the germanosilicate zeolite show different stability order—the most stable models are the structures with germanium spread among all D4Rs. Thus, for SCM-15 the stabilization due to the presence of the SDA and their orientation, is thermodynamic factor directing both the formation of specific framework type and Ge distribution in the framework during the synthesis. The relative stability of bare structures with different germanium distribution is of minor importance. This differs from SCM-14 germanosilicate, reported earlier, for which the stability order is preserved in presence of SDA. Thus, even for zeolites with the same chemical composition and SDA, the characteristics of their framework lead to different energetic preference for germanium distribution.

关键词: zeolite     density functional theory     structure-directing agent     SCM-15    

Atomistic simulations for adsorption and separation of flue gas in MFI zeolite and MFI/MCM-41 micro/mesoporous

Shengchi ZHUO, Yongmin HUANG, Jun HU, Honglai LIU

《化学科学与工程前沿(英文)》 2011年 第5卷 第2期   页码 264-273 doi: 10.1007/s11705-010-1007-6

摘要: Adsorption of pure CO and N and separation of CO /N mixture in MFI zeolite and MFI/MCM-41 micro/mesoporous composite have been studied by using atomistic simulations. Fully atomistic models of MFI and MFI/MCM-41 are constructed and characterized. A bimodal pore size distribution is observed in MFI/MCM-41 from simulated small- and broad-angle X-ray diffraction patterns. The density of MFI/MCM-41 is lower than MFI, while its free volume and specific surface area are greater than MFI due to the presence of mesopores. CO is preferentially adsorbed than N , and thus, the loading and isosteric heat of CO are greater than N in both MFI and MFI/MCM-41. CO isotherm in MFI/MCM-41 is similar to that in MFI at low pressures, but resembles that in MCM-41 at high pressures. N shows similar amount of loading in MFI, MCM-41 and MFI/MCM-41. The selectivity of CO over N in the three adsorbents decreases in the order of MFI>MFI/MCM-41>MCM-41. With increasing pressure, the selectivity increases in MFI and MFI/MCM-41, but decreases in MCM-41. The self-diffusivity of CO and N in MFI decreases as loading increases, while in MFI/MCM-41, it first increases and then drops.

关键词: adsorption     diffusion     CO2     flue gas     zeolite     micro/mesoporous composite    

Hierarchical ZSM-5 zeolite with radial mesopores: Preparation, formation mechanism and application for

Darui Wang, Hongmin Sun, Wei Liu, Zhenhao Shen, Weimin Yang

《化学科学与工程前沿(英文)》 2020年 第14卷 第2期   页码 248-257 doi: 10.1007/s11705-019-1853-9

摘要: Hierarchical ZSM-5 zeolite with radial mesopores is controllably synthesized using piperidine in a NaOH solution. The piperidine molecules enter the zeolite micropores and protect the zeolite framework from extensive desilication. The areas containing fewer aluminum atoms contain fewer piperidine protectant molecules and so they dissolve first. Small amounts of mesopores are then gradually generated in areas with more aluminum atoms and more piperidine protectant. In this manner, radial mesopores are formed in the ZSM-5 zeolite with a maximal preservation of the micropores and active sites. The optimal hierarchical ZSM-5 zeolite, prepared with a molar ratio of piperidine to zeolite of 0.03, had a mesopore surface area of 136 m ·g and a solid yield of 80%. The incorporation of the radial mesopores results in micropores that are interconnected which shortened the average diffusion path length. Compared to the parent zeolite, the hierarchical ZSM-5 zeolite possesses more accessible acid sites and has a higher catalytic activity and a longer lifetime for the alkylation of benzene.

关键词: hierarchical ZSM-5 zeolite     protective desilication     piperidine     radial mesopores     benzene alkylation    

标题 作者 时间 类型 操作

New approaches to vibrational spectroscopy of zeolite catalysts: a perspective

期刊论文

Control of aluminum distribution in ZSM-5 zeolite for enhancement of its catalytic performance for propane

期刊论文

Factors affecting the formation of zeolite seed layers and the effects of seed layers on the growth ofzeolite silicalite-1 membranes

ZHANG Xiongfu, WANG Jinqu, LIU Hai′ou, WANG Anjie

期刊论文

Photocatalytic degradation of omethoate using NaY zeolite-supported TiO

Dishun ZHAO, Jialei WANG, Zhigang ZHANG, Juan ZHANG

期刊论文

Synthesis, physicochemical characterizations and catalytic performance of Pd/carbon-zeolite and Pd/carbon-CeO

Zeinab JAMALZADEH, Mohammad HAGHIGHI, Nazli ASGARI

期刊论文

Zeolite-encaged gold catalysts for the oxidative condensation of furfural

期刊论文

Metal size effects over metal/zeolite bifunctional catalysts in the selective hydroalkylation of benzene

期刊论文

Catalytic fast pyrolysis of Kraft lignin with HZSM-5 zeolite for producing aromatic hydrocarbons

Xiangyu LI, Lu SU, Yujue WANG, Yanqing YU, Chengwen WANG, Xiaoliang LI, Zhihua WANG

期刊论文

CuO/zeolite catalyzed oxidation of gaseous toluene under microwave heating

Longli BO, Jianbo LIAO, Yucai ZHANG, Xiaohui WANG, Quan YANG

期刊论文

Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic

期刊论文

Biodiesel production from waste frying oil in sub- and supercritical methanol on a zeolite Y solid acid

Jorge MEDINA-VALTIERRA, Jorge RAMIREZ-ORTIZ

期刊论文

Effect of seawater salinity on the synthesis of zeolite from coal fly ash

Yanqing YU, Xiaoliang LI, Xiaolan ZOU, Xiaobin ZHU

期刊论文

The interaction of the structure-directing agent with the zeolite framework determines germanium distribution

期刊论文

Atomistic simulations for adsorption and separation of flue gas in MFI zeolite and MFI/MCM-41 micro/mesoporous

Shengchi ZHUO, Yongmin HUANG, Jun HU, Honglai LIU

期刊论文

Hierarchical ZSM-5 zeolite with radial mesopores: Preparation, formation mechanism and application for

Darui Wang, Hongmin Sun, Wei Liu, Zhenhao Shen, Weimin Yang

期刊论文