Co-reporter:Xiaomei Yang;Jingjing Bian;Jianhao Huang;Weiwen Xin;Tianliang Lu;Chen Chen;Yunlai Su;Feng Wang;Jie Xu
Green Chemistry (1999-Present) 2017 vol. 19(Issue 3) pp:692-701
Publication Date(Web):2017/02/06
DOI:10.1039/C6GC02437H
Hierarchical Sn-Beta zeolite was prepared through a hydrothermal postsynthesis method, which employed no fluoride and only a small amount of tetraethyl ammonium hydroxide (TEAOH). The dual roles of TEAOH as a base and as a structure directing agent were discussed in detail, which were significantly affected by its concentration. At a TEAOH concentration of 0.2–0.4 mol L−1, hierarchical Sn-Beta zeolites with the most probable mesopore diameter of 7.8 nm were achieved. Other physicochemical properties of the hierarchical Sn-Beta including the content and state of Sn and the acidity were also characterized. The hierarchical Sn-Beta zeolite gave a higher yield of methyl lactate (58%) than the microporous Sn-Beta zeolite synthesized in fluoride medium (47%) due to the promoting effect of the hierarchical porosity on the conversion of glucose in methanol, which is an important and challenging process of a biorefinery. The hierarchical Sn-Beta zeolite is stable and can be recycled and reused five times without significant loss of activity and selectivity.
Co-reporter:Xiaomei Yang, Lin Wu, Zhen Wang, Jingjing Bian, Tianliang Lu, Lipeng Zhou, Chen Chen and Jie Xu
Catalysis Science & Technology 2016 vol. 6(Issue 6) pp:1757-1763
Publication Date(Web):19 Oct 2015
DOI:10.1039/C5CY01037C
Hierarchical Sn-USY zeolites were prepared by the post-synthesis method via dealumination of H-USY zeolite with nitric acid and solid-state ion-exchange with SnCl4. High concentration of nitric acid was favorable for removal of framework Al and the following Sn incorporation. The physicochemical properties of Sn-USY zeolites were characterized by various techniques. Sn was incorporated into the framework site which created Lewis acid sites. Meanwhile, the abundant mesopores generated by acid treatment were preserved after Sn incorporation. The prepared hierarchical Sn-USY zeolites were used to catalyze the conversion of 1,3-dihydroxyacetone (DHA) to methyl lactate (MLA) in methanol. It is found that the hierarchical Sn-USY zeolites are highly active and selective for this reaction. At ambient temperature (25–40 °C), DHA was completely transformed with more than 95% MLA yield. Moreover, the hierarchical Sn-USY zeolites are recyclable and reusable at least five times without significant loss of activity and selectivity.
Co-reporter:Xiaomei Yang, Tianliang Lu, Chen Chen, Lipeng Zhou, Feng Wang, Yunlai Su, Jie Xu
Microporous and Mesoporous Materials 2011 Volume 144(1–3) pp:176-182
Publication Date(Web):October 2011
DOI:10.1016/j.micromeso.2011.04.011
A facile method for the synthesis of hierarchical AlPO-n molecular sieves (AlPO-nH) templated by saccharides was reported. Saccharides including soluble starch, sucrose, cellulose, and glucose as templates were investigated. Among these saccharides, glucose was the best template to create mesopores. Using pseudoboehmite treated by KOH as Al source for AlPO-nH, the amount of mesopores was greatly increased. The synthesized AlPO-nH samples were characterized by XRD, N2 physisorption, FTIR, TG, SEM and TEM. It was confirmed that the incorporation of glucose in the crystals of AlPO-nH was through the interactions of glucoses with the surface negative charges. After crystallization, the glucose embedded in the crystals was removed by combustion, and then the hierarchical AlPO-n molecular sieves were obtained.Graphical abstractHighlights► Hierarchical AlPO-n molecular sieves (AlPO-nH), including AlPO-5 and AlPO-11, were synthesized using glucose as template. ► The incorporation of glucose into AlPO-nH was through the interactions with the surface negative charges. ► This method can also be extended conveniently to synthesize other hierarchical molecular sieves such as AlPO-n, SAPO-n and MeAPO-n.
Co-reporter:Xiaomei Yang;Ying Wang;Chaofeng Zhang;Tao Fang;Wei Zhang;Jie Xu
Journal of Physical Organic Chemistry 2011 Volume 24( Issue 8) pp:693-697
Publication Date(Web):
DOI:10.1002/poc.1810
Abstract
The substituents of quinones play an important role in modulating the kinetics of the electron- and proton-transfer reaction. In this paper, the steric effects of substituents of quinones on their catalytic performance were studied in the oxidation of ethylbenzene and ascorbate. The substituents limited the addition of the free radicals to the CC double bonds of the quinone ring because of the steric hindrance. On the other hand, too many substituents hindered the contact between the active site (CO) of quinone and the reactant. So, the quinones with two substituents presented better catalytic performance than those with more or less substituents. These results will be helpful in designing the quinone compounds for drugs and in understanding the catalytic behavior of quinones in biochemistry. Copyright © 2010 John Wiley & Sons, Ltd.
Co-reporter:Xiaomei Yang;Ying Wang;Chen Chen;Wei Zhang;Jie Xu
Journal of Chemical Technology and Biotechnology 2010 Volume 85( Issue 4) pp:564-568
Publication Date(Web):
DOI:10.1002/jctb.2345
Abstract
BACKGROUND: Organocatalysis, a promising strategy for the oxidation of organic compounds, does not involve the use of a catalytic metal. In this work, an efficient organocatalyst system consisting of 2,3-dichloro-5,6-dicyano-benzoquinone (DDQ) and N-hydroxyphthalimide (NHPI) was studied.
RESULTS: 72.2% conversion with 92.3% selectivity for acetophenone was obtained in ethylbenzene oxygenation catalyzed by DDQ/NHPI under 0.3 MPa of molecular oxygen at 80 °C for 10 h. In addition, other hydrocarbons were also oxidized with high efficiency using this catalyst system. UV/Vis spectroscopy of the catalytic system indicated that DDQ accelerated the generation of free radical phthalimido-N-oxyl (PINO) by abstracting a hydrogen atom from NHPI.
CONCLUSION: An efficient organocatalyst system consisting of DDQ and NHPI for selective oxidation of hydrocarbons to corresponding ketones with molecular oxygen as oxidant is reported. DDQ promoted the generation of PINO from NHPI, and the oxidation reaction was accelerated via PINO. This organocatalyst system should be useful for the design of highly selective catalysts for hydrocarbon oxidation. Copyright © 2010 Society of Chemical Industry
Co-reporter:Xiaomei Yang, Lipeng Zhou, Chen Chen, Jie Xu
Materials Chemistry and Physics 2010 Volume 120(Issue 1) pp:42-45
Publication Date(Web):15 March 2010
DOI:10.1016/j.matchemphys.2009.10.018
Zr-MCM-41 materials were synthesized by the hydrothermal method in the presence of ZrOCl2 and NaCl. The characterization results showed that Zr was highly dispersed in the tetrahedral environment of silica framework. In the synthesis process, the self-generated acidity by the hydrolysis of ZrOCl2 acted as the catalyst for TEOS hydrolysis. In order to form the ordered structure of Zr-MCM-41, the addition of NaCl in the synthesis gel was essential and the optimum NaCl/Si molar ratio was 1.0. The ordering of Zr-MCM-41 was also influenced by the content of Zr, which decreased gradually with the increase of Zr content.
Co-reporter:Xiaomei Yang, Lipeng Zhou, Chen Chen, Xiaoqiang Li, Jie Xu
Materials Letters 2009 Volume 63(Issue 20) pp:1754-1756
Publication Date(Web):15 August 2009
DOI:10.1016/j.matlet.2009.05.045
Methyl group functionalized Zr-MCM-41 was synthesized by the hydrothermal method. The obtained Me–Zr-MCM-41 materials were characterized by X-ray diffraction, N2 physisorption, transmission electron microscopy, Fourier transform infrared spectroscopy and Ultraviolet–visible diffuse reflectance spectroscopy. The results indicated that Zr was highly dispersed in the framework of MCM-41, and methyl group was stable enough to endure the acid treatment for removing the template. The measurement results of the surface hydrophobic/hydrophilic properties showed that the surface hydrophobicity of Me–Zr-MCM-41 materials increased with increasing the content of methyl groups.
Co-reporter:Lipeng Zhou;Yong Chen;Xiaomei Yang;Yunlai Su;Wei Zhang;Jie Xu
Catalysis Letters 2008 Volume 125( Issue 1-2) pp:
Publication Date(Web):2008/09/01
DOI:10.1007/s10562-008-9537-y
Quinones with electron-withdrawing F, Cl or Br groups and N-hydroxyphthalimide (NHPI) were used as catalysts in selective oxidation of hydrocarbons with molecular oxygen as oxidant. The catalytic activity in the selective oxidation of ethylbenzene to oxygenation products was in the following order: p-benzoquinone < tetrafluoro-p-benzoquinone ≈ tetrachloro-p-benzoquinone < tetrabromo-p-benzoquinone (p-TBBQ). Moderate electron-withdrawing power of substituent was suitable for quinone abstracting hydrogen from NHPI to generate reactive phthalimido-N-oxyl (PINO). The catalytic activity of p-TBBQ/NHPI, the best catalyst in our study, was also tested in the selective oxidation of alkylarenes, alkenes and alkanes.
Co-reporter:Xiaomei Yang, Lin Wu, Zhen Wang, Jingjing Bian, Tianliang Lu, Lipeng Zhou, Chen Chen and Jie Xu
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 6) pp:NaN1763-1763
Publication Date(Web):2015/10/19
DOI:10.1039/C5CY01037C
Hierarchical Sn-USY zeolites were prepared by the post-synthesis method via dealumination of H-USY zeolite with nitric acid and solid-state ion-exchange with SnCl4. High concentration of nitric acid was favorable for removal of framework Al and the following Sn incorporation. The physicochemical properties of Sn-USY zeolites were characterized by various techniques. Sn was incorporated into the framework site which created Lewis acid sites. Meanwhile, the abundant mesopores generated by acid treatment were preserved after Sn incorporation. The prepared hierarchical Sn-USY zeolites were used to catalyze the conversion of 1,3-dihydroxyacetone (DHA) to methyl lactate (MLA) in methanol. It is found that the hierarchical Sn-USY zeolites are highly active and selective for this reaction. At ambient temperature (25–40 °C), DHA was completely transformed with more than 95% MLA yield. Moreover, the hierarchical Sn-USY zeolites are recyclable and reusable at least five times without significant loss of activity and selectivity.
