APPLIED CLAY SCIENCE
·
2018
·
IF 3.641
Shun Wang,Peixin Du,Peng Yuan,Xuemin Zhong,Yaqi Liu,Dong Liu,Liangliang Deng
This work investigated changes in the chemical composition, structure and porosity of hollow spherical allophane under alkaline conditions, which are significant not only for understanding its fate in natural environment but also for its functional applications. Hollow spherical allophane with a silicon/aluminium (Si/Al) molar ratio of 0.77 was hydrothermally synthesised followed by treatment with dilute sodium hydroxide (NaOH) solutions with different concentrations (indicated by pH values). The allophane and its alkali-treated products were then characterized using a combination of techniques, such as Fourier-transform infrared spectroscopy, nuclear magnetic resonance and nitrogen physisorption analysis. Allophane showed a weak structural stability in alkaline conditions. At pH ≤ 11.0, the framework of allophane particles was almost intact; its polymerised silicates showed only slight dissolution. At a higher pH (> 11.0), desilication and dealumination enhanced, resulting in the destruction of the imogolite local structure (ImoLS) along the edges of defect pores and the formation of amorphous materials . Most of the defect pores increased in size, becoming accessible to nitrogen and the textural parameters of the micropores reached their maximum values at a pH of 12.5. However, the damage to some secondary pores and the collapse of some hollow spherules reduced total pore volume ( V total ). At a pH of 13.0, most of the hollow spherules were observed to have collapsed, resulting in remarkable decrease in the textural parameters. However, some unbroken and/or mildly broken allophane particles might remain, deduced from the relatively high BET specific surface area (SSA) and V total and the considerable proportion of micropores for Allo 13.0 . These results reveal the dissolution behaviour of allophane in alkaline conditions and the mechanism underlying this behaviour, providing essential insights into the mineral's potential applications.
研究领域:
土壤科学
·
矿物学
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产品关联
DOI
高影响因子
RSC Advances
·
2025
·Vol. 15
·期 11
·8696-8706
·
IF 4.6
Zijian Wang,Ming Ke,Zhaozheng Song
Mordenite is extensively utilized in the domains of adsorption and catalysis owing to its excellent selectivity, stability, and renewability. In this work, the effects of crystal seeds, the ratio of SiO2/Al2O3, crystallization temperature, silicon source, and structure directing agents on the morphologies of mordenite are investigated by utilizing hexamethyleneimine (HMI) as the OSDA. Results indicate that the transformation of rod-like and flake-like mordenites is mainly related to the increasing ratio of SiO2/Al2O3, and the formation of flake-like morphology is related to various conditions. On a macro level, the rod-like and flake-like zeolites are formed by transforming amorphous precursors into small crystals and growing them epitaxially. On a micro level, HMIH+ progressively displaces Na+ to balance the framework charge with the increasing ratio of SiO2/Al2O3. DFT calculation and nuclear magnetic resonance results confirm the specific guidance of HMI on the T2 and T4 sites of the rod-like and flake-like mordenites. The conclusion can serve as a reference for regulating the morphology and active sites of mordenite.
研究领域:
材料科学
·
催化与吸附领域
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产品关联
DOI
PubMed
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2023
·
IF 8.6
Ye Li,Yong Wang,Honghao Bai,Shishuai Li,Xiaomin Li,Xiaoqing Wang,Libo Li,Jinping Li,Jiangfeng Yang
The economically efficient separation of ethane (C 2 H 6 )/ethylene (C 2 H 4 ) presents challenges in the petrochemical industry, and the use of traditional adsorbents zeolite provides a reliable guarantee for maintaining the economic viability of adsorption separation technology. In this study, we investigate the impact of different silica-alumina ratios (SiO 2 /Al 2 O 3 = 40, 500, and 1500) of high silica zeolites ZSM-11 on the C 2 H 6 /C 2 H 4 separation performance to develop efficient C 2 H 6 selective adsorbents. The results show that the C 2 H 6 adsorption capacity and C 2 H 6 /C 2 H 4 selectivity of ZSM-11 increase as the silica-alumina ratios increases. The pure silica zeolite (ZSM-11(1500)) exhibits the highest adsorption capacity for C 2 H 6 (59.19 cm 3 /g) and the highest selectivity for C 2 H 6 /C 2 H 4 (2.04), which were superior to ultra-high silica sample (ZSM-11(500)) (55.06 cm 3 /g and 1.62, respectively) and high silica sample (ZSM-11(40)) (47.28 cm 3 /g and 1.23, respectively), at 273 K and 1 bar. The mixed gas breakthrough experiments results show that pure silica sample has outstanding C 2 H 6 /C 2 H 4 separation ability. The PSA simulation calculated data demonstrating promising potential for industrial applications. Importantly, this separation performance remains unaffected even in the presence of H 2 O.
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Molecular Catalysis
·
2017
·
IF 0
Shuang Chu,Li’na Yang,Xingcui Guo,Linlin Dong,Xiufang Chen,Yaru Li,Xindong Mu
The catalytic behavior of a series of MFI catalysts with different Si/Al ratio (25–300) in the direct aqueous-phase hydrolysis of α-cellulose was studied. The effects ultrasonic pretreatment time, ZnCl 2 content, zeolite pore structure and acid-basic properties on catalyst activity and products distribution were systematically investigated. The results indicated that HZSM-5 with lower Si/Al ratio was beneficial for production of glucose and LA from α-cellulose. Ultrasonic pretreatment could decrease the degree of crystallinity and polymerization of α-cellulose, enhance the accessibility of acid sites and ZnCl 2 to the loosened amorphous regions of α-cellulose in water, and improve the hydrolysis efficiency of α-cellulose. The desilicated ZSM-5 (HZSM-5-DS(0.2)) showed much higher catalytic activities as compared to commercial ZSM-5 and α-cellulose conversion reached 76.5% over HZSM-5-DS(0.2) at 200 °C. Catalytic conversion of α-cellulose consisted of at least three important parallel reactions under the present hydrothermal conditions and a plausible pathway was proposed. Effective control of these reactions would be helpful to further maximize the target product yield during the catalytic conversion of α-cellulose.
研究领域:
化学工程
·
生物质转化
✓ 已验证
DOI
MICROPOROUS AND MESOPOROUS MATERIALS
·
2017
·
IF 3.615
Chang Wang,Jiaqi Liu,Jiangfeng Yang,Jinping Li
Synthesis of ultra-high silica (SiO 2 /Al 2 O 3 > 1800) MFI type zeolite such as silicalite-1 is still considered to be luxury because of the long synthesis time (5–12 days). Here, this material with a highly uniform mesoporous (20 nm) structure was crystallized in a shorter time (20 h) using a crystal-seeds method when an appropriate amount of potassium fluoride was added. Characterization techniques including XRD , SEM, TEM and liquid nitrogen adsorption provided detailed information on the two kinds of porous structure silicalite-1. Due to the “smooth” adsorption surface of silicalite-1 containing few equilibrium ions, it is ideal for the separation of gas mixtures containing non-polar molecules with similar physical properties. Moreover, the CH 4 , N 2 , CO 2 and C 2 H 6 adsorption properties were also investigated. Microporous silicalite-1 has a high adsorption capacity for CH 4 , N 2 , CO 2 and C 2 H 6 and adsorption selectivity for CH 4 /N 2 , CO 2 /N 2 , CO 2 /CH 4 and C 2 H 6 /CH 4 . Although a lower adsorption capacity was observed for mesoporous silicalite-1, the pore size did not affect the outstanding adsorption selectivity, on the contrary, the selectivity of mesoporous silicalite-1 was improved.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
Catalysis Science & Technology
·
2016
·Vol. 6
·期 8
·2647-2652
·
IF 5.287
Hualei Hu,Jinghui Lyu,Jiayao Rui,Jie Cen,Qunfeng Zhang,Qingtao Wang,Wenwen Han,Xiaonian Li
Ethylbenzene is the major side product in benzene alkylation with methanol and it is difficult to be suppressed over hierarchical porous ZSM-5. Moreover, the separation of ethylbenzene from xylene still remains a great challenge. Our research indicated that ethylbenzene formation could be highly suppressed by changing the Si/Al ratio of the catalyst. Hierarchical porous ZSM-5 catalysts with different Si/Al ratios were prepared via reducing the amount of Al in the solvent evaporation assisted dry gel conversion method. In this method, tetra-n-propylammonium hydroxide was used as the direct agent to create micropores, and hexadecyltrimethoxysilane was added to create additional porosities by forming organic assemblies which occupied a certain space between zeolitic walls. The catalyst with a Si/Al ratio of 1800 could achieve high benzene conversion (59.5%) and high xylene selectivity (39.0%) as well as excellent suppression of ethylbenzene formation (<0.1%).
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
高影响因子
JOURNAL OF SOLID STATE CHEMISTRY
·
2022
·
IF 3.656
Jiale Zhu,Siyan Yan,Guohao Xu,Xuedong Zhu,Fan Yang
A variety of HZSM-5 zeolites with different b-axis thicknesses and SiO 2 /Al 2 O 3 were fabricated by simply modifying urea content and Al source feeding in the initial gel, respectively. Multiple characterization technologies including XRD , SEM, N 2 adsorption-desorption, NH 3 -TPD and Py-IR were employed to investigate physicochemical properties of these samples and the possible crystallization mechanism was proposed that adsorption of urea molecules on (010) facet was the key factor for fabricating thin-sheet HZSM-5 zeolites. The results of hexane cracking reaction revealed that the selectivities of light olefins reached 46.5% when controlling b-axis thickness to 340 nm, exceeding the control sample by 12.2%. Furthermore, the effect of SiO 2 /Al 2 O 3 under this b-axis thickness was also investigated and concluded that keeping SiO 2 /Al 2 O 3 to 200 could exhibit the optimum catalytic performance with the conversion of 95.5% and light olefins selectivities of 56.7%. The reaction conditions were optimized to be 600 °C at the N 2 flow rate of 25 mL/min and WHSV of 3 h −1 to arouse the best performance. Under this condition, the distribution of ethene and propene was quite close to that of thermodynamic equilibrium. Based on these results, the primary and secondary products were uncovered, and further the reaction pathway of hexane cracking was disclosed. This new strategy to synthesize sheet-like catalysts for enhancing the catalytic properties in hexane cracking also laid a solid foundation for the study of the catalysts on light oil cracking in industry.
研究领域:
化学工程
·
催化材料科学
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Nano Materials
·
2024
·
IF 5.3
Ling Pan,Song Ye,Ruihao Huang,Meiyan Wang,Peixuan Lin,Haoran Zhang,Deping Wang
Faujasite (FAU) zeolites with abundant exchangeable sites are ideal hosts for the intake of Ag+ and the stabilization of highly luminescent silver nanoclusters (Ag NCs), while theoretical calculations on the spectral characteristics, charge states, and electronic energies of Ag NCs that are confined inside FAU zeolite were seldom reported. In this research, the Na-type FAU zeolites with varying silicon-to-aluminum (Si/Al) ratios were first synthesized with the hydrothermal method and then applied as matrixes to stabilize Ag NCs to obtain tunable emissions. With the decrease in the Si/Al ratio, the Ag NCs show red-shifted emission from 515 to 548 nm and broadened photoluminescence of excitation (PLE) and photoluminescence (PL) spectral profile. The time-dependent density functional theory (TD-DFT) method was carried out to probe the effect of Al substitution on the charge states and the optical properties of Ag NCs confined inside the double-six ring (D6r) cavity. The simulated results of the absorption spectra and energy levels suggest that the S1 → S0 transition of the monovalent Ag3+ cluster is responsible for the visible emission, and the increased full width at half-maximum (fwhm) of the PLE and PL spectra in the low Si/Al ratio FAU zeolites is due to the inhomogeneous broadening brought by the increased isomer numbers of the Al-substituted neutral zeolite framework. It is noted that the peak of the simulated absorption spectra red-shifted with the decrease in the Si/Al ratio, which is consistent with the experimental observation. This research provided an effective method for the manipulation of Ag NC emission in FAU zeolites through framework cation substitution and meanwhile theoretically explained the Si/Al ratio dependence of tunable emission properties, which may benefit the design of zeolite-confined Ag NCs with desirable optical performances.
研究领域:
材料科学
·
化学
✓ 已验证
DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2022
·
IF 5.876
Yingshu Liu,Haiyang Tao,Xiong Yang,Xiaoyong Wu,Jinjuan Li,Chuanzhao Zhang,Ralph T. Yang,Ziyi Li
Adsorption is a promising technology for capturing nitrogen oxides (NO x ) from humid flue gases , for which as the preferred NO x adsorbent, zeolite with an appropriate silica to alumina (Si/Al) ratio provides the key step for success in practical applications. In this work, the effects of Si/Al ratio, temperature, relative humidity (RH), and feed gas (NO x -H 2 O(g)–CO 2 –O 2 -N 2 ) compositions on NO x sorption behavior on HZSM-5 zeolites were systematically investigated, based on a series of characterizations, fixed-bed adsorption and temperature programmed desorption (TPD) tests. The low-silica HZSM-5(25) showed the best performance (326.6 μmol/g and 39.2 μmol/g at dry and 90%RH) as compared to others with higher Si/Al ratios at each RH, in which the roll-up effect was positively correlated with the Si/Al ratios and humidity. O 2 enhanced NO x adsorption and reached an optimal adsorption capacity at the concentration of 14%, while CO 2 had little effect on NO x adsorption. The decrease in temperature increased NO x adsorption capacity on HZSM-5(25), benefitting from NO 2 physisorption as well as satisfactory NO oxidation within the active adsorbent structure. The facile thermal desorption of NO x and significant NO–NO 2 conversion on HZSM-5(25) was exhibited by bimodal TPD peaks at 343–353K and 533–543K respective for NO and NO 2 , in contrast to those on Silicalite-1. A potential “water-resistant” strategy via the enhancement of NO x adsorption competitiveness was revealed, providing a theoretical guideline for NO x adsorbent screening in industrial applications.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2021
·
IF 5.455
Jiayuan Wang,Mingquan Li,Yajie Fu,Cederick Cyril Amoo,Yujia Jiang,Ruiqin Yang,Xu Sun,Chuang Xing,Elton Maturura
Zeolites are vital industrial materials applied widely in the field of heterogeneous catalysis . Porous zeolites are essentially synthesized in the presence of soft or hard templates in processes such as hydrothermal, solvothermal, and ionothermal synthesis. Herein, we demonstrated a facile ambient pressure technique to synthesize NaY zeolite using a glass tube as a reactor and a fluid sealant to create a physical barrier between the reactor contents and the atmosphere. The synthesized zeolite Y was characterized by XRD , SEM, TEM , UV-Raman, N 2 sorption , MAS NMR, and XRF spectroscopy . In comparison to the traditional hydrothermal synthesis routes, the avoidance of high-pressure synthesis apparatus not only reduces safety risks but also significantly improves the yield of zeolite products with a crystallinity of 52% and Si/Al = 3.51. Furthermore, the process is leaner, efficient, and reduces costs. Optimum conditions realized for the synthesis of highly crystalline zeolite Y were 90 °C and 18 h crystallization temperature and period respectively, using 1-dodecanol as a sealant. Subsequently, PEG6000 emerged the best among organic templates investigated to improve porosity while maintaining high crystallinity of the zeolite.
研究领域:
材料科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
ANALYTICAL LETTERS
·
2024
·
IF 1.6
Qing Shan,Yangxue Luo,Xinlei Zhang,Zhanpeng Zhang,Wenbao Jia,Yongsheng Ling,Daqian Hei,Jiandong Zhang,Chao Shi,Jiehua Bao
The silicon-aluminum ratio of the molecular sieves is a crucial control index for the quality of synthetic molecular sieves. Here a fast, simple and reliable sample preparation method, referred to as pouring and curing method, is described for determining the silicon-aluminum ratio of high silicon molecular sieves by energy dispersive x-ray fluorescence (EDXRF). Resin is used as the carrier with the addition of a curing agent, so that the sample powder is embedded in the resin matrix. By measuring sixteen random positions of the same cured sample, the homogeneity of the sample was evaluated to ensure the stability of the results. A double logarithmic calibration curve of the analysis line ratio and the corresponding concentration ratio of silicon and aluminum was established according to the binary ratio method. The results by EDXRF and inductively coupled plasma-optical emission spectrometer (ICP-OES) were compared with a relative standard error from 2.934 to 6.777%. The good precision shows that the pouring and curing method is a suitable for measuring the silicon-aluminum ratio of molecular sieves.
研究领域:
材料科学
·
分析化学
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Materials & Interfaces
·
2021
·
IF 9.229
Yi Zhai,Xubin Zhang,Fumin Wang,Guojun Lv,Tao Jiang,Yuzhou Wu,Mengyue Li,Mengyao Li,Qing Zhang,Yongkui Liu
Development of economic strategy to synthesize hollow zeolite with widely tunable Si/Al ratios providing variable acidity is of great significance in industry. Here, a one-step and low-cost strategy without mesoporogen was successfully developed to synthesize single-crystal hollow ZSM-5 containing mesopores/macropores, with variable Si/Al ratios of about 14–∞ and 114–∞ at critical TPA+/SiO2 ratios of 0.05–0.1 and 0.05, respectively. This is the first time the usage of a large amount of TPAOH was avoided while breaking the traditional limitation of Si/Al ratio (25–50). The component of synthesis system and crystallization temperature acting as the vital roles in hollow structure has been confirmed by a series of characterization. Moreover, according to the investigation of the evolution process, a novel racing crystallization mechanism based on the competition relationship between surface crystallization and the internal dissolution rate was proposed for the first time. The racing crystallization mechanism and internal nonprotective aluminum become the crucial factors for synthesis. The prepared hollow ZSM-5 zeolites exhibit superior catalytic performance in the different acidity-catalyzed condensation involving large molecules between benzaldehyde and n-butyl alcohol as well as 2-hydroxyacetophenone, which is mainly attributed to the property acidity, more accessible active Al sites on the surface, and shorter diffusion path. By calculating, the effectiveness factor (η) of hollow zeolite is close to 1, further confirming its better mass transfer ability. The strategy has also been successfully extended to the synthesis of high-amount Fe-doped, Ga-doped, and B-doped hollow silicate-1.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）