MICROPOROUS AND MESOPOROUS MATERIALS
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2015
·
IF 3.453
Tingting Lu,Ruren Xu,Wenfu Yan
The initial mixture containing fully hydrolysed tetraethyl orthosilicate (TEOS) and tetraethylammonium hydroxide (TEAOH) solution was treated either by heating at 80 °C or by freeze-drying. After adding an appropriate amount of concentrated hydrofluoric acid , the resulting mixture was crystallized at 150 °C. The heating treated mixture produced polymorph A-enriched zeolite beta while freeze-drying treated mixture gave only normal zeolite beta. The 13 C magic angle spinning nuclear magnetic resonance (MAS NMR) analysis and thermogravimetric analysis (TGA) indicated that a partial decomposition of TEAOH to generate triethylamine (TEA) occurred during the heating dehydration process, which was the only difference compared with the freeze-drying process. Together with the reduced TEAOH, different monoamines as a co-template directed the polymorph A-enriched zeolite beta with the freeze-drying process. Diamines as a co-template directed only the normal zeolite beta. The synthesis cost of polymorph A-enriched zeolite beta can be significantly reduced by lowering the usage of expensive TEAOH and using cheaper monoamines.
研究领域:
材料科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2017
·
IF 3.615
Guang Xiong,Xiyan Liu,Ruixue Zhao,Jiaxu Liu,Jinpeng Yin,Qingrun Meng,Zhendong Guo,Liping Liu
Nano-sized zeolite Beta aggregates with interparticle mesopores were synthesized by the aerosol-assisted method. The amorphous powders in the Na 2 O–Al 2 O 3 −SiO 2 system, which was obtained from an aerosol drying process, were used as the precursor. The zeolite was crystallized in a high concentration system with high alkalinity. This can not only improve the autoclave utilization and the crystallization rate, but also reduce the amount of both template and waste water. The obtained zeolite Beta is spherical nano-aggregates with interparticle mesopores. It shows high BET surface area and good Al species distribution. The study on crystallization process indicated that the precursor gradually dissolved under the strong alkaline condition and the nano-sized zeolite crystals were formed in the liquid phase as time prolonged. Therefore, the transformation mechanism mainly followed the liquid-phase mechanism. More importantly, the zeolite beta synthesized by aerosol-assisted method exhibited good catalytic activity and stability in the cracking reaction of 1,3,5-TIPB.
研究领域:
材料科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
ANALYTICA CHIMICA ACTA
·
2024
·
IF 5.7
Li Yang,Ru Liu,Chaodan Li,Boning Gu,Jiannong Ye,Li Chen,Qingcui Chu
Background With the rapid growth of the demand for optically pure compounds in the fields of biology, medicine and stereospecific synthesis, it is of great importance to develop efficient, economical, simple enantioseparation and analysis methods. Open tubular capillary electrochromatography (OT-CEC) has attracted much attention in the field of chiral separation , but its column capacity and the sensitivity of common-used optical detection are relatively low. Zeolite beta nanomaterial is both enantioselective and size-selective, providing suitable chiral microenvironment for chiral recognition, and amperometric detection (AD) avoids the low sensitivity caused by the short optical path in optical detection to some extent. Results Zeolite beta nanomaterials with different particle sizes (25, 50 and 200 nm) were synthesized, and the morphology and structure were characterized by scanning electron microscopy and X-ray diffraction. Then, a novel chiral OT column was prepared by one-step method using zeolite beta nanomaterial as chiral stationary phase, and its separation performance was characterized by miniaturized CEC with AD (mini-CEC-AD) device. Under the optimum conditions, six groups of chiral drugs achieved baseline separation. Norepinephrine enantiomers were used for evaluating the inter-day, intra-day and inter-column reproducibility of the prepared open-tubular column. The relative standard deviations of migration time, peak area, resolution and selectivity factor were within 8.7 %. The limits of detection for norepinephrine enantiomers were 0.18 μg mL −1 (S/N = 3), and the average recoveries were in range of 96.7–105.0 %. This developed method has been successfully applied to the analysis of impurity enantiomer in potassium dichromate (+)-norepinephrine injection sample. Significance Zeolite beta nanomaterial was used as the stationary phase to prepare chiral OT columns for the first time, and this one-step preparation method is simple and easy. The introduction of zeolite beta enriches the types of chiral stationary phase materials in electrochromatographic columns, and mini-OT-CEC-AD system provides an alternative for fast enantioseparation of chiral compounds.
研究领域:
分析化学
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药物化学
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生物医学
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产品关联
DOI
PubMed
高影响因子
RSC Advances
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2015
·Vol. 5
·期 105
·86620-86624
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IF 3.84
Tao Wang,Huiping Zhang,Ying Yan
A novel porous zeolite beta coating/PSSF composite was prepared by secondary growth method in fluoride media. The morphology of zeolite beta coating/PSSF composite was characterized by SEM and the structural and textual properties of composite were characterized by XRD and N2 adsorption/desorption isotherms on ASAP 2020, respectively. The thermal stability of composite was analyzed by thermogravimetry (TG) and differential scanning calorimetry (DSC). The results indicated that well-intergrown and continuous zeolite beta coating with highly crystallinity were successfully synthesized on the surface of paper-like stainless steel fibers support. The structures of zeolite beta coating/PSSF composite were three-dimensional network with large void volume and majority of microporous structure. The thickness of zeolite beta coating on stainless steel fibers is approximate 2 μm. The specific surface area (SBET) and the total pore volume of composite were 118 m2 g−1 and 0.067 cm3 g−1, respectively. The composite was stable at temperature up to 650 °C.
研究领域:
材料科学
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化学工程
✓ 已验证
DOI
高影响因子
LANGMUIR
·
2025
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IF 3.9
Gen Li,Yunqi Hu,Zhaojun Liu,Yanlei Sha,Chenyang Zhao,Honghai Liu,Xinye Fan,Pingyu Wan,Hongjuan Zhao,Hongtao Liu
The introduction of mesoporosity is of great importance because mass-transportation limitations within microporous systems hinder their catalytic performance. The direct formation of mesoporosity in zeolite is generally achieved through the use of an additional and expensive organic template, which limits its industrial applications. In this investigation, we reported a facile procedure for synthesizing zeolite Beta with micromesoporosity, in which tetraethylammonium hydroxide (TEAOH)/crystal seeds (CS) worked as the micropore-directing agents, assisted by simple citric acid (CA) containing hydroxyl carboxylic groups. The working mechanism of TEAOH/CS/CA was proposed on the basis of various characterization methods. Oxalic acid was employed as an additional template to further elucidate the formation mechanism of the mesopores. The formation mechanism is proposed that CA with hydroxyl carboxylic groups can interact with aluminosilicate and TEAOH simultaneously to form a semimicelle, leading to the final mesostructure. The resultant mesoporous material was tested in the esterification reaction of benzyl alcohol and acetic acid. Improved activity and selectivity were observed as a result of the introduction of intracrystalline mesopores, suggesting the superiority of the CA-assisted zeolite Beta. This novel procedure provides a simple procedure for obtaining zeolite Beta with hierarchical pores, which can enable the economic and environmentally friendly production of hierarchical zeolites for industrial applications.
研究领域:
材料科学
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催化
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化学合成
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多孔材料
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工业化学
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产品关联
DOI
PubMed
高影响因子
CHEMISTRY-A EUROPEAN JOURNAL
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2014
·Vol. 20
·期 45
·14744-14755
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IF 5.696
Jiao Chen,Weiming Hua,Yu Xiao,Qisheng Huo,Kake Zhu,Xinggui Zhou
The crystallization of zeolite beta in a dry gel system is found to follow the orientated attachment growth route, escorted with a temporal morphology change from bulky gel, through aggregation of the particulate to large zeolitic crystals. Modification of the precrystallized gel with organosilanes can be used to tune the morphology of the ultimate beta. When hexadecyltrimethoxysilane (HTS) is employed to modify precrystallized gel, a resumed secondary growth produces a hybrid mesocrystal of agglomerated nanozeolites. Combustive removal of organics leads to the formation of hierarchically porous zeolite beta of 100 to 160 nm, composed of nanocrystal building units ranging from 20 to 40 nm, with a noticeable micropore volume of 0.19 mL g −1 and a meso/macropore size between 5 and 80 nm. Conversely, when 1,8-bis(triethoxysilyl)octane (BTO) is utilized to modify the same precrystallized gel, assemblages of discrete beta nanozeolite of around 35 nm are generated. These assemblages construct a hierarchical zeolite beta with a micropore volume of 0.20 mL g −1 and auxiliary pores ranging from 5 to 100 nm. Both organosilanes bring about well-connected hierarchical pore networks. HTS has little effect on the Brønsted/Lewis acidity, whereas BTO causes a substantial reduction of strong Brønsted acid sites. The hierarchical beta zeolite-supported Pt catalyst exhibits improved catalytic performance for the hydroisomerization of n -heptane. Graphical Tailor-made zeolite beta : The orientated attachment growth of zeolite beta in a dry gel system can be developed into a method to fabricate hierarchically porous beta (see figure). The pore connectivity, particle size, and acid properties are tunable with the assistance of organosilane additives. The Pt supported on hierarchical beta outperforms the conventional counterpart in n -heptane hydroisomerization.
研究领域:
材料化学
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催化化学
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纳米材料科学
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多孔材料
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化学工程
✓ 已验证
DOI
高影响因子
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