Catalysis Science & Technology
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2018
·Vol. 8
·期 13
·3346-3356
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IF 5.365
Peidong Li,Qiao Han,Xiaomin Zhang,Yangyang Yuan,Yanfei Zhang,Hongchen Guo,Li Xu,Lei Xu
Side-chain alkylation of toluene with methanol is a potential technology to realize the one-step production of styrene under mild conditions. Herein, a series of cesium X zeolites with different cesium contents were prepared through an ion-exchange method. The performance of the CsX zeolites was extensively investigated in the side-chain alkylation of toluene and methanol. The acid–base properties of the involved CsX were characterized and the results showed that the acid–base properties present regular changes with varied cesium contents. Based on the full understanding of the acid–base properties of the involved CsX, the reaction behaviors of the main and side reactions in the side-chain alkylation of toluene with methanol over CsX were investigated and new insights were revealed. It has been found that the crucial steps for the main reactions were the activation of toluene and the formation of formaldehyde from dehydrogenation of methanol when the cesium exchange degree of CsX was lower and higher than 32.3%, respectively. The hydride transfer reaction between styrene and carbon deposition is responsible for the formation of ethylbenzene over CsX with lower cesium contents, while the transfer hydrogenation of styrene with methanol and formaldehyde was the main path for ethylbenzene formation over CsX with higher cesium contents. And it was found that the existence of Brønsted acid sites accounts for the formation of xylene over CsX. These new findings will give a new insight into the reaction behaviors of the side-chain alkylation of toluene with methanol over CsX and may also provide a potential modification method for high-efficiency catalysts.
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
RSC Advances
·
2019
·Vol. 9
·期 23
·13234-13242
·
IF 3.049
Peidong Li,Qiao Han,Xiaomin Zhang,Yangyang Yuan,Yanfei Zhang,Li Xu,Hongchen Guo,Lei Xu
The effect of the introduced base sites in CsX with alkali oxide modification towards side-chain alkylation of toluene with methanol was systematically investigated in the present work. A series of alkali oxide modified CsX with a base properties (base strength and amount) gradient were prepared by impregnating CsX with alkali metal hydroxide. Here, CsX with different base strengths were selected as the parent zeolite, which is favorable to clarify the different types of base site in the modified CsX. The base properties of the samples were elucidated based on the CO2-TPD results as well as with characterization by XPS and FT-IR of adsorbed CO2. It was revealed that the base strength of the oxygen atoms with negative charge (Oδ−) in the zeolite framework can be strengthened by the electron donating function of the alkali oxides in the supercage of CsX. Detailed analysis of the correlation between the reaction behaviors of side-chain alkylation reaction and the base properties of the indicated catalysts was carried out. It was found that the dehydrogenation of methanol to formaldehyde step was promoted by the increasing base properties of Oδ− in the CsX framework and that was the main reason for the promotion of the whole side-chain alkylation reaction. However, it was also found that the stronger base properties of the alkali oxide modified CsX would enhance the formation of active hydrogen atoms, which aggravated the unwanted styrene conversion to ethylbenzene.
研究领域:
催化
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化学工程
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF CHEMICAL THERMODYNAMICS
·
2021
·
IF 3.178
Qi-Chao Yang,Dong-Fang Qiu,Yuan-Lin Dang,Zhan-Ping Qiao,Zhi-wei Xu
Two equilibrium diagrams of the ternary system (CsX + MnX 2 + H 2 O, X = Cl, Br) at 298.15 K are reported in this paper. Each system has two double salts (CsMnX 3 ·2H 2 O and Cs 2 MnX 4 ·2H 2 O X = Cl, Br) in it and the elements of all double salts in phase diagrams are confirmed by Schreinemaker method. Equilibrium phase diagrams show that the chloride double salts are congruently soluble compounds in water, however that the bromide double salts are incongruently soluble compounds in water. All the double salts are characterized by titrimetric analysis, powder X-ray diffraction, thermogravimetric and differential thermalanalysis. The enthalpies of formation of these double salts are first calculated by measuring their enthalpies of dissolution.
研究领域:
物理化学
·
无机化学
·
热力学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF CHEMICAL THERMODYNAMICS
·
2024
·
IF 2.2
Yufeng Tang,Qichao Yang,Zhanping Qiao
The phase equilibrium of ternary systems RbX/CsX + CuX 2 + H 2 O (X = Cl, Br) at T = 298.15 K were investigated by the isothermal dissolution equilibrium method, in which the composition of equilibrium solid phases was determined by the Schreinemaker’s wet residue method. In the system RbCl + CuCl 2 + H 2 O, there were three crystallization regions corresponding to RbCl, Rb 2 CuCl 4 ·2H 2 O and CuCl 2 ·2H 2 O, respectively. Five crystallization fields corresponding to CsCl, CsCuCl 3 , Cs 3 Cu 2 Cl 7 ·2H 2 O, Cs 2 CuCl 4 and CuCl 2 ·2H 2 O were formed in the system CsCl + CuCl 2 + H 2 O. The ternary system RbBr + CuBr 2 + H 2 O had three crystalline regions corresponding to RbBr, Rb 2 CuBr 4 ·2H 2 O and CuBr 2 . In the system CsBr + CuBr 2 + H 2 O, the solid-phases of CsCuBr 3 , Cs 2 CuBr 4 , besides CsBr and CuBr 2 , were discovered. The results were compared with available literature data for cesium bromide/copper bromide salt-water system. The seven new solid phase were characterized using the X-ray diffraction method and thermogravimetric/differential analysis. The dissolution enthalpies of Rb 2 CuCl 4 ·2H 2 O, Rb 2 CuBr 4 ·2H 2 O, CsCuCl 3 , Cs 3 Cu 2 Cl 7 ·2H 2 O, Cs 2 CuCl 4 , CsCuBr 3 and Cs 2 CuBr 4 at T = 298.15 K were measured. Their standard enthalpies of formation were obtained, and the results were in order with −(1714.4 ± 3.2) kJ·mol −1 , −(1533.6 ± 3.3) kJ·mol −1 , −(697.8 ± 3.1) kJ·mol −1 , −(2418.9 ± 6.1) kJ·mol −1 , −(1134.8 ± 3.2) kJ·mol −1 , −(563.5 ± 3.2) kJ·mol −1 and −(966.2 ± 3.3) kJ·mol −1 , respectively.
研究领域:
物理化学
·
无机化学
·
热力学
✓ 已验证
DOI
高影响因子
FUEL
·
2020
·
IF 5.578
Qijun Yu,Jinzhe Li,Changcheng Wei,Zhongmin Liu
Although side-chain methylation of toluene with methanol to produce styrene has been investigated in the past decades, commercial application of this process is still a great challenge due to the lack of efficient catalysts. Here we present a bifunctional catalyst composed of dehydrated sodium borate (Na 2 B 4 O 7 ) and zeolite (CsX) that yields a high selectivity to styrene (89.6%) with a relative high toluene conversion (9.57%). Na 2 B 4 O 7 not only contributes to the formation of the reaction intermediate formaldehyde but also constructs the frustrated Lewis pairs (FLPs) with basic sites on the zeolites, which could activate C–H bond in the methyl group of toluene more efficiently. Thus, the crucial role of boron species is revisited. The nature of cesium in CsX is found to be important for the reactivity of the bifunctional catalyst. Good reaction performance on composite catalyst Na 2 B 4 O 7 -CsX also depends on the spatial proximity and mass ratio of the two components.
研究领域:
化学工程
·
催化
·
有机化学
✓ 已验证
产品关联
DOI
高影响因子
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