JOURNAL OF COLLOID AND INTERFACE SCIENCE
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2024
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IF 9.4
Yan Chen,Guojun Lv,Xuyang Zou,Shihao Su,Jiangzhang Wang,Chaoyi Zhou,Jialing Shen,Yangbin Shen,Zhongmin Liu
Dealuminated Beta zeolite has a large amount of silanol defects on its interface, which provides an ideal place for embedding metal species and creating metal active sites in a confined microenvironment. The confined metal sites as well as their surroundings are closely related to the reactant activation and transient state achievement. Hence, unraveling the confined metal sites is of great significance for the catalytic reaction process. Herein, niobium species were incorporated into the silanol defects over dealuminated Beta zeolite with a facile dry impregnation method, co-grinding the niobium precursor with dealuminated Beta zeolite support. The successful incorporation of niobium into the silanol defects for 30Nb-Beta zeolite was verified by DRIFT, 1 H MAS NMR, UV–Vis and UV-Raman characterizations. XAS characterization and DFT calculations further disclosed that the confined Nb species existed as (SiO) 2 Nb(OH)(=O), containing two Si−O−Nb bonds, one Nb=O bond as well as one Nb−OH bond. The synthesized 30Nb-Beta zeolite catalyst displayed a superior cyclohexene conversion of 51.1%, cyclohexene oxide selectivity of 83.1% as well as TOF value of 188.2 h −1 ascribed to the inherent electrophilicity of Nb(V) for confined (SiO) 2 Nb(OH)(=O) species as well as the low oxygen transfer energy barrier for Nb V −OOH species. Furthermore, the prepared 30Nb-Beta zeolite can be effectively employed to other cyclic alkene epoxidation reactions.
研究领域:
催化化学
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材料科学
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DOI
PubMed
高影响因子
CATALYSIS LETTERS
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2019
·Vol. 150
·期 5
·1445-1453
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IF 2.372
Ye Yuling,Yao Mengqin,Chen Honglin,Zhang Xiaoming
Abstract The silanol defects in ZSM-5 zeolite have been recognized as an important factor in catalytic activity. Here, ZSM-5 zeolites with different amounts of silanol defect sites were synthesized from synthetic gels containing fluoride medium and were applied as catalysts for trioxane synthesis. The results of XRD, SEM, NH 3 -TPD, Py-IR, OH-IR, 27 Al MAS NMR, 1 H MAS NMR, and TG indicated that all ZSM-5 zeolites showed similar crystal size, relative crystallinity, porosity, and the number of Brønsted acid sites. However, the silanol defects reduced obviously and the number of Lewis acid sites reduced correspondingly when a little NH 4 F was added in the synthesis gels and both of them decreased slightly with increase of F/Si ratio. Compared with ZSM-5 zeolite prepared in hydroxide medium, ZSM-5 zeolite prepared in fluoride medium displayed higher selectivity to trioxane and increased gradually with increase of F/Si ratio. Moreover, the lifetime of ZSM-5 zeolite prepared in fluoride medium was longer than that of prepared in hydroxide medium. Thus, ZSM-5 zeolite prepared in fluoride medium which contained the few silanol defects and low Lewis acid sites is an efficient catalyst for trioxane synthesis. Graphic Abstract
研究领域:
化学工程
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催化科学
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DOI
高影响因子
Surfaces and Interfaces
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2023
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IF 6.2
Lei Zhou,Xiangyu Xi,Haidong Li,Han Song,Qiong Mei,Yuankun Yang,Shu Chen,Qunwei Dai,Faqin Dong
Vanadium contamination has gained increasing attention around the world and it is urgent to develop feasible approach to tackle this growing pollution (e.g., vanadate). Herein, density functional theory (DFT) calculations combined with batch experiments were used to systematically evaluate the capacity of Mg(OH) 2 to adsorb vanadate , by investigating the impacts of different exposed facet and surface OH defect on the structure configurations, adsorption energy and the efficiency of vanadate adsorption. DFT calculations suggested that although the capacity of vanadate adsorption on the facets of Mg(OH) 2 would be obviously influenced by the formation of various coordination complex (e.g., monodentate, bidentate and tridentate) on each facet, the capacity for these facets of Mg(OH) 2 towards vanadate adsorption followed the order: (100) > (001). Moreover, such a vanadate adsorption was further enhanced by the presence of surface OH defect, owing to altered densities of states (DOS) of the adsorption site. Batch experiments verified the defect-rich Mg(OH) 2 was favorable to adsorb vanadate, and both (001) and (100) facet play the great roles. This molecular-level understanding of the facet-dependent and defect-enhanced adsorption behavior of Mg(OH) 2 toward vanadate provides a useful insight into designing and applying effective adsorbents for the removal of heavy metal oxyanions.
研究领域:
环境科学
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材料科学
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化学
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DOI
高影响因子
JOURNAL OF COLLOID AND INTERFACE SCIENCE
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2025
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IF 9.7
Meile Yue,Kankan Bu,Yahong,Zhang,Wei Shen,Hualong Xu,Zhen Huang
Propane dehydroaromatization (PDA) provides a promising route to produce valuable chemicals such as benzene, toluene and xylene via non-petroleum feedstocks, in which Ga-modified MFI zeolites demonstrate high activity but are susceptible to severe coke deposition. The defect-derived silanols (Si-OH) in zeolite formed during synthesis has emerged as a predominant factor, making the prolongation of the catalyst longevity a major challenge. Here, we developed a gallosilicate MFI zeolite with silanol-defect remediated (Ga-MFI-AHFS) through an ammonium hexafluorosilicate post-treatment, which exhibited an extraordinary activity and stability. Ga-MFI-AHFS exhibits a nearly unchanged propane conversion around 82.0 % with aromatics selectivity around 64.5 % compared to a 25.4 % conversion decline on the raw zeolite with defects exposed during the 20-h CO 2 assisted PDA reaction. The results of FTIR and MAS NMR showed a decreased content of silanol nests as well as the internal Si-OH groups, indicating the successful repair of silicon hydroxyl defects. The restored framework endows the Ga-MFI-AHFS zeolite with an excellent coking resistance, giving a much lower coking-rate of 5.8 × 10 −8 mol C /mol C-in-produced-Aromatics , which is one-sixth of that on Ga-MFI. This work developed a facile route to prepare Ga-MFI zeolite with suppressed silanol-defects, which could help to realize a stable dehydroaromatization of light alkanes.
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高影响因子
ACS Applied Materials & Interfaces
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2023
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IF 9.5
Wangying Xu,Tao Peng,Changjie Zhou,Deliang Zhu
Rare earth oxides (REOs) can be used as high-κ gate dielectrics that are at the core of electronic devices. However, a bottleneck remains with regard to obtaining high-performance REO dielectrics due to the serious hygroscopic issue and high defect states. Here, a general boronization strategy is reported to enhance the high-κ REO gate dielectric performance. Complementary characterization reveals that boronization is capable of reducing oxygen vacancies/hydroxyl defects in REOs and suppressing moisture absorption, leading to the improvement of leakage current, breakdown strength (up to 9 MV/cm), and capacitance–frequency stability. Furthermore, oxide transistors based on boronized REO dielectrics demonstrate state-of-the-art device characteristics with a high mobility of 40 cm2/V s, a current on/off ratio of 108, a subthreshold swing of 82 mV/dec, a hysteresis of 0.05 V, and superior bias stress stability.
研究领域:
材料科学
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半导体器件
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电子工程
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DOI
PubMed
高影响因子
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