Chemical Engineering and Processing-Process Intensification
·
2024
·
IF 3.8
Zifei Yan,Grace Dai Zhen Lee,Jian Deng,Guangsheng Luo
The synthesis of terminal epoxides, which are vital components in pharmaceuticals and resins, often involves dehydrochlorination of β-chlorohydrins. Although intrinsic kinetics indicate that the dehydrochlorination reaction in the presence of sodium hydroxide could be very rapid, the practical implementation could always be hindered by long reaction time and low conversion rate. Extended contact between the product and the alkaline solution can lead to hydrolysis of the epoxy group, thus necessitating the process intensification to realize higher production efficiency and selectivity. Here, by characterizing thermodynamic equilibrium data and in-situ recording of the reaction that proceeded in a constant interphase reactor, the heterogeneous dehydrochlorination is demonstrated to occur primarily in the organic phase, and the overall reaction rate depends on the equilibrium concentration of sodium alkoxides. This finding, which is fundamentally different from the traditional view that chlorohydrin is first dissolved in the aqueous phase and then reacts with NaOH, leads us to use inert alcohols to assist in the extraction of NaOH. Based on this method, the reaction time can be reduced over 80 % both in batch and continuous reactors. Besides, the method is demonstrated to be effective in the dehydrochlorination of five different long-chain β-chlorohydrins.
研究领域:
化学工程
·
有机合成
✓ 已验证
DOI
高影响因子
POLYMER DEGRADATION AND STABILITY
·
2017
·
IF 3.386
Danfeng Zhang,Shen Yao,Shuai Li,Jun Wang,Youwei Yao
A new thermal stabilizer , La-Gly (Gly = n -[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]-glycin), was synthesized. Through discoloration and dehydrochlorination tests at 180 °C, La-Gly is found to possess high stabilizing efficiency for poly(vinyl chloride) (PVC): as the mass ratio of La-Gly to PVC resin is increased from 0.3/50.0 to 2.0/50.0, the time to degradation of PVC samples increases from 90 min to 190 min. Studies on combinations of La-Gly and ZnSt 2 , and of La-Gly and dibenzoyl methane (DBM) show that the initial color of PVC is improved, as the ratio of ZnSt 2 to La-Gly or DBM to La-Gly is increased from 0.3/1.2 to 1.2/0.3. One sample (50.0 g PVC, 0.6 g ZnSt 2 , 0.9 g La-Gly, 3.4 g tributyl citrate) shows the best balance between initial color and long-term thermal stability (140 min). Studies on dynamic thermal stability of the samples (50.0 g PVC, x g La-Gly, 3.4 g tributyl citrate, x = 0.3, 0.6, 0.9, 1.2, 1.5, 2.0) show that when x equals 1.2, the thermal dynamic stability time is 24.5 min, much longer than 6.4 min and 4.8 min, respectively, for two controls (50.0 g PVC, 1.5 g LaSt 3 , 3.4 g tributyl citrate; 50.0 g PVC, 0.6 g CaSt 2 , 0.9 g ZnSt 2 , 3.4 g tributyl citrate).
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2018
·
IF 11.698
Tong-Yang Song,Zhao-Xia Dong,Jian-Dong Song,Xiao-Xia Wang,Guan-Qun Xie,Meng-Fei Luo,Ji-Qing Lu
Dehydrochlorination of 1, 1, 2-trichloroethane was performed on SiO 2 supported alkali metal (Na. K, Cs) and transition metal (Mn, Ni, Zn) catalysts. The surface basicity or acidity of the catalyst exerted great influence on catalytic behaviors. The catalysts with higher amount of base or acid sites resulted in higher activity due to more adsorption sites for reactant. The basic catalysts (Cs/SiO 2 and K/SiO 2 ) tended to form vinylidene chloride with a selectivity up to 80 %; the neutral catalysts (Na/SiO 2 and SiO 2 ) tended to form 1, 2-dichloroethene with a selectivity up to about 80 %; the acidic catalysts (Zn/SiO 2 , Mn/SiO 2 and Ni/SiO 2 ) tended to form 1, 2-dichloroethene with a selectivity up to 96 %. Proposed reaction mechanisms included an E1cb mechanism with a carbanion intermediate on the basic catalysts, an E2 concerted mechanism on the neutral catalysts, and an E1 mechanism with a carbonium intermediate on the acidic catalysts.
研究领域:
化学工程
·
催化科学
✓ 已验证
DOI
高影响因子
CHEMICAL RESEARCH IN CHINESE UNIVERSITIES
·
2015
·Vol. 31
·期 5
·787-791
·
IF 0.875
Tang Cen,Jin Yanxia,Wang Xiaoxia,Hu Gengshen,Xie Guanqun,Li Xiaonian,Luo Mengfei
The manufacture of 1,1-dichloroethylene(1,1-DCE) usually employs liquid phase method to perform the dehydrochlorination of 1,1,2-trichloroethane(TCE), where large amounts of high-concentration salty wastewater is produced inevitably. It has been a long-term goal to achieve the gas phase synthesis of 1,1-DCE via supported catalysts. In this work, the gas-phase synthesis of 1,1-DCE from TCE was studied in the presence of pentaethylenehexamine( PEHA) supported on silica. High and stable selectivity to 1,1-DCE(up to 98%) was obtained, which could be ascribed to the relatively strong basicity of PEHA according to a proposed E2 mechanism. The formation of PEHA chloride from the HCl generated in situ was detected and was considered to be the main reason for the deactivation of PEHA catalyst.
研究领域:
化学工程
·
催化化学
✓ 已验证
DOI
高影响因子
CARBON
·
2022
·
IF 11.307
Qing Yu,Xiaoling Mou,Luyao Guo,Zupeng Chen,Ronghe Lin,Yunjie Ding
Nitrogen-doped carbons (NC) and carbon nitride (C 3 N 4 ) belong to the two fundamental pillars of functionalized carbon materials that have broad applications in different fields. The synthesis of NC and C 3 N 4 often starts from different precursors, and a general approach that can offer both architectures is still highly sought. Herein, a facile Triton X-100-assisted copolymerization-carbonization strategy is reported to fulfill this task. By moderating the weight ratios of Triton X-100 and several conventional precursors of C 3 N 4 ( e.g ., dicyandiamide, urea, and cyanamide), a series of both types of N-functionalized carbons with controllable N dopants is successfully afforded. The yielded solids transform from graphitic C 3 N 4 with low surface areas to porous NC when the weight ratio reaches the critical values. This phenomenon might be attributed to the intensified copolymerization between the intermediates of both starting precursors during the carbonization, resulting in increased oxygen content and decreased N:C ratio in the products. Both the bulk and activated carbon-supported materials are then designed and used as metal-free catalysts in the dehydrochlorination of ethylene dichloride, a key reaction in polyvinyl chloride manufacture. It is found that NC is significantly more active than C 3 N 4 , but the corresponding supported catalysts exhibit an opposing trend. The structure-activity correlations suggest both the number of different N defects and the surface areas might play key roles in determining the dehydrochlorination chemistry.
研究领域:
材料科学
·
催化化学
✓ 已验证
DOI
高影响因子
JOURNAL OF FLUORINE CHEMISTRY
·
2022
·
IF 2.226
Tongyun Zhang,Chengping Zhang,Xiaoxun Ma,Hengdao Quan
Chlorotrifluoropropene isomers including 1‑chloro-3,3,3-trifluoroproene (HCFO-1233zd(Z/E)) and 2‑chloro-3,3,3-trifluoropropene (HCFO-1233xf) were adopted as the dehydrochlorination materials to produce 3,3,3-trifluoropropyne (TFPY) by one-pot method were reported. The experimental data indicated that HCFO-1233zd(Z) was the most favorable synthetic raw material in this process, followed by HCFO-1233xf, and HCFO-1233zd(E) then. However, DFT calculations demonstrated the superiority of HCFO-1233zd(E) to HCFO-1233xf according to the reaction energy barrier. By further referring to the thermodynamic calculations and the computed water solubility, the reaction priority herein was identified as HCFO-1233zd(Z) > HCFO-1233xf > HCFO-1233zd(E). Therefore, compared to kinetic effects, the reactivity of HCFO-1233zd(Z/E) and HCFO-1233xf was evidently determined by their thermodynamic properties and solubility. This work thus provides guidance for similar hydrogen halide removal in liquid phase.
研究领域:
化学工程
·
理论化学
✓ 已验证
产品关联
DOI
高影响因子
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