MICROPOROUS AND MESOPOROUS MATERIALS
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2023
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IF 5.2
Shaoxiang Xu,Meihua Zhu,Pengming Huang,Shengao Zheng,Yujie Qiao,Yuan Liang,Xiangshu Chen,Hidetoshi Kita
Nano-size titanium silicalites is difficult to be separate from the reaction solution, lamellar and homogeneous Ti-MWW zeolites are successfully formed a dense zeolite layers on α-Al 2 O 3 pellets by secondary hydrothermal synthesis in this study. Seeded crystals concentration and titanium source have significantly influences on the morphology, thickness and titanium active sites of Ti-MWW zeolites. Doping NH 4 F in the precursor synthesis solution could conducive to prepare macroscopically and anatase-free Ti-MWW zeolites layer on the outside of α-Al 2 O 3 pellets, and the thickness of the Ti-MWW zeolites layer is ca. 1 mm. Besides, catalytic performance of the supported Ti-MWW zeolites are significantly improved by NH 4 F. A fixed-bed reactor with the supported Ti-MWW zeolites are applied to catalyze phenol hydroxylation with hydrogen peroxide efficiently, and reaction time and temperature, amount of the supported Ti-MWW zeolites have obvious effects on the phenol conversion and dihydroxybenzene selectivity. When the actual mass of Ti-MWW zeolites to volume of reaction solution is only 10 g/L, the relative phenol conversion and dihydroxybenzene selectivity are 46.45% and 92.72% at 65 °C after 3 h, respectively.
研究领域:
催化
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材料科学
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化学工程
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DOI
高影响因子
CATALYSIS LETTERS
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2019
·Vol. 150
·期 1
·209-221
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IF 2.372
Xu Songlin,Zhang Mingyi,Guo Shujuan,Li Mengru,Huang Qingming,Chen Xiaohui
Abstract Diffusion limitation caused by microporous molecular sieves has always been a bottleneck problem in liquid phase epoxidation. In this study, several different carbon sources were used as hard templates to prepare hierarchically porous zeolite Ti-MWW (cTi-MWW) successfully. Compared with conventional Ti-MWW, cTi-MWW has an additional hierarchically porous structure and abundant pore structure distribution. Especially, the cTi-MWW prepared with polyethylene glycol1540 (PEG) as the hard template not only has a multiple hierarchically porous structure, but also exhibits small crystal size and good hydrophobicity properties studied by TEM and in situ FT-IR. At the same time, the cTi-MWW prepared with PEG exhibits better activity than the conventional Ti-MWW in the selective epoxidation reaction of allyl alcohol (AAL) with H 2 O 2 as oxidant and the conversion is improved by 11% (Si/Ti = 20). And a higher efficiency and longer catalyst life in fixed-bed catalytic reactor were exhibited by using cTi-MWW PEG as catalyst. The physicochemical properties of cTi-MWW prepared with different hard templates were systematically studied by SEM, XPS, UV–Vis, XRD and N 2 absorption–desorption techniques. This method is effective for the synthesis of cTi-MWW and significant for the preparation of hierarchically porous zeolites in industrial production. Graphic Abstract A hierarchically porous zeolite Ti-MWW prepared with different hard templates successfully. With the hierarchically porous structure, which have better adsorption, diffusion, and reactivity in liquid phase epoxidation, thus improving the catalytic activity. Especially, the hierarchically porous zeolite Ti-MWW prepared with polyethylene glycol exhibits small crystal size and good hydrophobicity properties.
研究领域:
材料科学
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催化化学
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DOI
高影响因子
KOREAN JOURNAL OF CHEMICAL ENGINEERING
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2022
·Vol. 39
·期 1
·96-108
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IF 3.146
Zeng Xingye,Adesina Adeyemo,Li Ping,Wang Hanlu,Zhou Rujin
Ti-containing Mobil composition of matter-twenty-two (Ti-MWW) zeolite was prepared via a two-step post-synthesis process and then characterized by X-ray fluorescence, nitrogen adsorption-desorption isotherms, Fourier transform infrared absorption spectra, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectra. These results indicate that the textural properties of MWW were well preserved after acid treatment and incorporation of titanium. An adsorptive-oxidative desulfurization (AODS) system was successfully developed on the basis of a model oil containing dibenzothiophene (DBT) with the as-prepared Ti-MWW being the catalyst and adsorbent and cumene hydroperoxide (CHP) being the oxidant. The parameters influencing the desulfurization performance were systematically investigated. These parameters include the Ti-MWW dosage, the reaction temperature, the stirring speed, the molar ratio of CHP to DBT and the additions of olefins and aromatics to the system. The conversion rate of DBT reached 99.6% via the catalytic oxidation process and the turnover frequency was 40.1 h −1 . Meanwhile, the oxidation products of DBT were removed by Ti-MWW adsorption. The recycling and regeneration performance of Ti-MWW were also investigated, and the DBT conversion reached 99.5% using the regenerated Ti-MWW. This work provides useful information for the construction of solvent-free oxidative desulfurization systems using a zeolite.
研究领域:
化学工程
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环境科学
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催化材料
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产品关联
DOI
高影响因子
JOURNAL OF CATALYSIS
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2025
·
IF 6.5
Yuexia Wang,Jiaqi Xu,Xuan Lin,Chaosi Liu,Xinqing Lu,Yijing Gao,Francesco Pepe,Domenico Caputo,Weidong Zhu
Ti-MWW zeotypes, characterized by their unique dual pore architecture consisting of intralayer 10-membered ring (MR) pore channels and additional interlayer 10-MR pore channels that are interconnected to intracrystalline 12-MR supercages, exhibit a remarkably catalytic superiority in the selective oxidation of small and/or linear alkenes with hydrogen peroxide (H 2 O 2 ), surpassing other titanosilicate zeotypes in performance. However, a further improvement on their catalytic performance is still needed for the industrialization of alkene epoxidation over Ti-MWW. In the present work, the introduction of NH 4 + species into Ti-MWW was conducted via a facile but effective treatment of the as-synthesized zeotypes with NH 4 Cl, named N-Ti-MWW. The comprehensive characterization of N-Ti-MWW, derived from NH 4 + -exchanged Ti-MWW, coupled with Density Functional Theory (DFT) calculations, conclusively demonstrates that the integration of NH 4 + into Ti-MWW promotes the generation of -Ti-OOH hydroperoxo intermediates, resulting in a higher catalytic activity in alkene epoxidation in comparison to the parent one. Moreover, the solvolysis of epoxides is significantly suppressed on N-Ti-MWW, enabling the catalyst to display a superior selectivity towards the targeted epoxide, thereby improving its overall catalytic performance. Additionally, N-Ti-MWW is reusable, after the regeneration of the deactivated catalyst simply treated with NH 4 Cl. As a result, it is anticipated that N-Ti-MWW would be applicable in the industrial epoxidation of alkenes with H 2 O 2 .
研究领域:
化学工程
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材料科学
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产品关联
DOI
高影响因子
ACS Catalysis
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2013
·
IF 5.265
Wen-Juan Zhou,Raphael Wischert,Kai Xue,Yu-Ting Zheng,Belén Albela,Laurent Bonneviot,Jean-Marc Clacens,Floryan De Campo,Marc Pera-Titus,Peng Wu
Various types of Ti-containing zeolites, i.e., Ti-MWW, TS-1, Ti-MOR, and Ti-BEA, have been evaluated as candidates for the liquid-phase oxidation of cyclohexane using t-butyl hydroperoxide (TBHP, 7–8 wt %) as model oxidant. Ti-MWW zeolite displayed the highest activity for cyclohexanol and cyclohexanone (KA oil) with an overall selectivity higher than 90% at 80 °C, making this catalyst a candidate of choice for industrial KA oil production by deperoxidation of cyclohexyl hydroperoxide. The effect of the reaction temperature, reaction time, catalyst amount, and catalyst stability on Ti-MWW was surveyed in detail. The Ti-MWW catalyst showed a stable performance and could be recycled at least four times without detectable Ti leaching and loss of structural stability. The active sites for cyclohexane oxidation appeared to be located near external 12-ring cups in the Ti-MWW framework as suggested by a series of position-selective poisoning tests with tripropyl- and triphenylamine, impelling cyclohexane diffusion within the internal 10-ring channels. EPR experiments supported by DFT calculations suggested the coexistence of both Ti(IV)-OO• (peroxyl) and Ti(IV)-O• (oxyl) species generated through bimolecular pathways, implying simultaneously (SiO)3Ti(OOtBu) species and tBuOOH. The catalytic activity was strongly inhibited in the presence of alkenes, leading to the preferential formation of the epoxidation product with no detectable formation of radicals. Notably, this is the first time that oxyl species have been detected particularly with the help of DFT calculations. Predicted differences of g tensors between peroxyl and oxyl species at various hydration levels in the presence of cyclohexane were consistent with the EPR spectra.
研究领域:
催化化学
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材料科学
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产品关联
DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
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2021
·
IF 5.455
Kang Tang,Weilong Hou,Xiaoshu Wang,Wen Xu,Xinqing Lu,Rui Ma,Yanghe Fu,Weidong Zhu
The titanosilicate zeolite catalyzed epoxidation of propylene with hydrogen peroxide (H 2 O 2 , HP) to propylene oxide (PO), the so-called HPPO, is more eco-efficient, compared to the chlorohydrin process and the epoxidation using organic hydroperoxides. However, the zeolite catalysts used in the HPPO process are easily deactivated, because the main byproduct propylene glycol (PG) and other heavy byproducts with high boiling points, derived from the solvolysis of PO, are deposited inside the zeolite micropores. In the present work, trimethylsilylated Ti-MWW zeolites, named Si–Ti-MWW, were developed for the HPPO process. In combination with the results from extensive characterizations for the prepared zeolites, it is found that the trimethylsilylation merely occurs on the external surface of Ti-MWW crystals and can significantly enhance the hydrophobicity , but not alter the coordination states of the Ti species and textural properties of the zeolites. The catalytic properties of Ti-MWW and Si–Ti-MWW were compared in propylene epoxidation. The results show that the solvolysis of PO to the byproducts can be effectively inhibited over the hydrophobic zeolite surface, making Si–Ti-MWW exhibit a much higher selectivity for PO and a much better stability and reusability than the parent Ti-MWW in the HPPO process. The current study, therefore, provides a new approach to develop efficient catalysts for the HPPO process.
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
JOURNAL OF CATALYSIS
·
2023
·
IF 7.3
Yuexia Wang,Qibin Yao,Bowen Xu,Kehang Lin,Mengshan Deng,Xinqing Lu,Rui Ma,Yanghe Fu,Weidong Zhu
Although the oxidative hydration of ethylene with hydrogen peroxide (H 2 O 2 ) to ethylene glycol (EG) over Ti-MWW zeolites take advantages of step-saving and facile operation, both H 2 O 2 utilization efficiency and EG yield are relatively low, because some extra-framework octahedral Ti species are usually formed in the Ti-MWW zeolites synthesized by prevailing methods, which are detrimental to selective oxidation . In the present work, an acid-modulated isomorphous substitution method, i.e. , layered borosilicate MWW-type zeolite (ERB-1) treated with HNO 3 aqueous solution containing tetrabutyl orthotitanate (TBOT), is developed to synthesize a Ti-MWW zeolite without extra-framework octahedral Ti species under the optimized synthesis conditions. In combination with the results from extensive characterizations for the synthesized zeolites, it is found that in the zeolite prepared by the currently developed synthesis method there are more open Ti(OSi) 3 OH sites formed, resulting in the stronger Lewis acidity that is very helpful to EG production from the oxidative hydration of ethylene with H 2 O 2 , compared to the one synthesized by the prevailing method. Moreover, the developed catalyst is recyclable after the regeneration of the deactivated zeolite by calcination at high temperatures. Therefore, it is anticipated that the currently developed Ti-MWW might be industrially applicable in the one-pot synthesis of EG from ethylene with H 2 O 2 .
研究领域:
化学工程
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催化材料科学
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产品关联
DOI
高影响因子
JOURNAL OF CATALYSIS
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2022
·
IF 8.047
Yuan Liang,Shaoxiang Xu,Meihua Zhu,Jiamin Jiang,Jiao Zhang,Goubing Zhou,Na Hu,Xiangshu Chen,Hidetoshi Kita
In the absence of boric acid, the tubular Ti-MWW zeolite membranes are prepared with dual organic template agents and potassium carbonate by secondary hydrothermal synthesis. 12MR cage and 10 MR of the MWW zeolite topology structure is stabilized by TMAdaOH and HMI organic template agents, K + cations is a critical mineralization agent for preparing Ti-MWW zeolite membrane with bi-layer Ti-MWW zeolites layer in this work. Besides, ion-exchange could greatly improve the catalytic performance of the Ti-MWW zeolite membrane for phenol hydroxylation with H 2 O 2 , influences of ammonium salt, ion-exchange time and temperature on the micro-structure and catalytic performance are investigated. The upper network-like Ti-MWW zeolite layer could be dissolved and removed by ion-exchange with 0.5 M (NH 4 ) 2 SO 4 solution at 60 °C for 24 h, and the “lying” Ti-MWW zeolites layer is kept on the mullite support. On the other hand, ion-exchange could promote the transformation of hexacoordinated extra-framework titanium species to tetracoordinated state in the framework, part of K + cations of Ti-MWW zeolites are replaced with NH 4 + cations. Total flux and phenol conversion of the ion-exchanged Ti-MWW zeolite membrane are 14.89 kg·m −2 ·h −1 and 36.49 % for phenol hydroxylation by H 2 O 2 at 50 °C.
研究领域:
材料科学
·
催化化学
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DOI
高影响因子
CATALYSIS LETTERS
·
2022
·Vol. 153
·期 2
·348-363
·
IF 2.936
Chu Jidong,Ge Zhijin,Peng Jiahui,Hu Hui,Guo Shujuan,Chen Xiaohui
The efficient and economic heteroatom-implanting method for MWW-type zeolite has been the focus of attention and needs further exploration. Ti incorporated MWW zeolite was synthesized by sequential treatment of boron-containing zeolite precursor. The catalysts were applied to the epoxidation of 1-hexene. The implanting titanium process was conducted under a mild condition with Ti(SO 4 ) 2 /NH 4 HF 2 /HNO 3 solution, and the product Ti-MWW precursors have framework titanium alone, the novel method is named as refluxing and implanting titanium method which integrates acid treatment and titanium incorporation into one step and reduces the consumption of time of this process into 1 h. A density functional theory was conducted to explain the formation mechanism of interlayer-expanded structure of Ti-MWW zeolite. Subsequently, Ti-MWW precursors were treated in modified reagent solution to obtain larger pore structure, which increase the conversion of 1-hexene from 20.45 to 62.96%. The catalytic performance of Ti-MWW zeolite in this work are superior to Ti-MWW zeolite synthesized by traditional dry-gel conversion method the conversion of 1-hexene of which was 4.2%. This novel method is a promising approach for the synthesis of high catalytic performance heteroatomic zeolite. Graphical abstract
研究领域:
材料科学
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化学工程
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催化
·
无机化学
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DOI
高影响因子
JOURNAL OF CATALYSIS
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2022
·
IF 8.047
Wen Xu,Xiaoshu Wang,Weilong Hou,Kang Tang,Xinqing Lu,Yijing Gao,Rui Ma,Yanghe Fu,Weidong Zhu
Although the titanosilicate zeolite catalyzed one-pot oxidative hydration of ethylene with hydrogen peroxide (H 2 O 2 ) to ethylene glycol (EG) takes advantages of step-saving and facile operation, both H 2 O 2 utilization efficiency and EG yield are relatively low. In the present work, Sn-doped Ti-MWW zeolites, named Sn-Ti-MWW, were developed for this oxidative hydration, showing the much higher H 2 O 2 utilization efficiency and EG yield, compared to Ti-MWW. The extensive characterizations of Sn-Ti-MWW zeolites, in combination with Density Functional Theory (DFT) calculations, verify that the doping of Sn into Ti-MWW leads to the higher electropositivity of the Ti species, resulting in the stronger acidity of the zeolite, which is helpful to the H 2 O 2 utilization and EG production. In addition, although the catalyst deactivation is observed due to the deposition of the bulky byproducts onto the active sites and/or into the zeolite micropores, the simple calcination of the used catalyst readily restores its catalytic activity. Therefore, it is anticipated that the developed Sn-Ti-MWW catalyst might be applicable in the one-pot oxidative hydration of ethylene with H 2 O 2 to EG industrially.
研究领域:
化学工程
·
催化材料
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产品关联
DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2018
·
IF 3.649
Meihua Zhu,Yongsheng Liu,Yongkang Yao,Jiamin Jiang,Fei Zhang,Zhen Yang,Zhanghui Lu,Izumi Kumakiri,Xiangshu Chen,Hidetoshi Kita
A novel and dense tubular Ti-MWW zeolite membrane for the phenol hydroxylation was successfully prepared on mullite support by secondary hydrothermal synthesis . The ultraviolet–visible spectroscopy and fourier transform infrared spectrometer confirmed that the Ti species was thetetrahedrally coordinated state in zeolite framework. Plenty of pure phase sheet Ti-MWW zeolite crystals were fully covered on the support surface, the Ti/Si molar ratio and thickness of the Ti-MWW zeolite layer were 0.016 and 5 μm by X-ray photoelectron spectroscopy and scanning electron microscope characterization results, respectively. The membrane showed good catalytic performance for phenol hydroxylation under pervaporation condition at 323 K. The phenol conversion and dihydroxybenzene selectivity were 22.94% and 98.33%, respectively.
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DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2020
·
IF 4.551
Jiamin Jiang,Meihua Zhu,Yongsheng Liu,Yuqin Li,Tian Gui,Na Hu,Fei Zhang,Xiangshu Chen,Hidetoshi Kita
Influences of synthesis conditions on the growth and catalytic performance of the Ti-MWW zeolite membrane are investigated in this work. Medium crystallization time, crystallization temperature , molar ratios of the precursor synthesis gels (TiO 2 /SiO 2 , H 2 O/SiO 2 and B 2 O 3 /SiO 2 ) are crucial to prepare the compact and good catalytic performance Ti-MWW zeolite membranes. High crystallization temperature and long crystallization time cause a hetero zeolite phase membrane on the mullite support. Excessive titanium in the precursor synthesis gel could easily arise TiO 2 particles and non-framework TiO 6 species on the membrane surface , which are greatly decreased the catalytic performance of the Ti-MWW zeolite membrane. Dilute precursor synthesis gel is not favor for preparing dense Ti-MWW zeolite layer. The as-synthesized Ti-MWW zeolite membrane is applied as catalytic membrane reactor for phenol hydroxylation by pervaporation in this study, the phenol conversion and benzenediol selectivity are 41.42% and 98.33%.
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DOI
高影响因子
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