CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Yangzhen Jin,Yebin Zhou,Pengze Zhang,Yi Liu,Chunshan Lu,Xiaonian Li
The catalytic alkaline dehydrochlorination process, characterized by high atom economy, stands as a prevalent method in the synthesis of valuable alkene halides. Nonetheless, the efficacy of ionic liquids (ILs) as catalysts for dehydrochlorination is hindered by challenges such as swift deactivation attributed to decomposition and reduced selectivity without clear causative factors. This investigation employs a systematic approach, integrating Density Functional Theory (DFT) simulations with experimental methodologies, to delve into the mechanisms of IL-catalyzed dehydrochlorination, aiming to elucidate both stabilization strategies and catalytic pathways. The examination of thermal decomposition rates is rooted in a meticulous assessment of the energy barriers associated with decomposition and dissociation processes. The active role of free Cl − is established, albeit its acidification by HCl, which results in diminished catalytic activity. To counteract this acidifying influence, a novel active site denoted as [Cl-KCl] − is conceptually devised to mitigate such effects. Through the strategic implementation of cationic fixation, the IL-KCl combination catalyst is synthesized and empirically confirmed to demonstrate augmented acid resistance while upholding a consistent reaction selectivity of approximately 85 %. This contrasts starkly with the declining catalytic selectivity observed with IL in isolation, plummeting from 85% to 65%. Consequently, the IL-KCl combination catalyst emerges as a promising option for alkali catalyzed dehydrochlorination, offering enhanced stability and sustained high selectivity throughout the catalytic process.
研究领域:
化学工程
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
SYNTHETIC COMMUNICATIONS
·
2013
·
IF 1.06
Xuerui Zhang,Guoping Yong,Wenlong She
The potassium metal can promote direct arylation of unactivated aromatic C-H bonds under an oxygen atmosphere. Interestingly, in situ demethoxylation, dechloridation, or decyanogenation from the corresponding coupling aromatic compounds mediated by potassium metal was also observed in the radical reaction systems.
Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for full spectral details.
研究领域:
有机化学
·
合成化学
✓ 已验证
产品关联
DOI
高影响因子
POLYMER DEGRADATION AND STABILITY
·
2018
·
IF 3.193
Bozhen Wu,Yating Wang,Si Chen,Muyan Wang,Meng Ma,Yanqin Shi,Xu Wang
A novel kind of poly(vinyl chloride) (PVC) thermal stabilizer , zinc dehydroacetate (ZnL 2 ), was designed and synthesized using zinc acetate and dehydroacetic acid (DA) as raw materials, which had a unique "zinc burning" inhibition synergistic effect with calcium stearate (CaSt 2 ) that was 8 times greater than that of the CaSt 2 /ZnSt 2 combination reference stabilizer . The structure and stability of ZnL 2 were confirmed by Fourier-transform infrared, elemental analysis , and thermogravimetric analysis . The stability distinction of ZnL 2 and ZnSt 2 , and the stable effect of the two systems after being combined with CaSt 2 , were investigated by the Congo red test, solution acidity test, and discoloration test. The results showed that in the Congo red test the stability time of ZnL 2 was 8.9 min, which was 1.3 times that of ZnSt 2 , and the stability time of ZnL 2 /CaSt 2 was 13 min, which was 1.4 times that of a traditional Ca/Zn stabilizer. Furthermore, the stability time of ZnL 2 was 36 min in the solution acidity test, which was 2 times higher than that of ZnSt 2 , and the stability time was increased to 196 min after combining it with CaSt 2 , which was 8 times greater than that of the Ca/Zn stabilizer. Moreover, the dehydrochlorination rate of PVC stabilized with ZnL 2 was slower than with other stabilizers. The system with ZnL 2 /CaSt 2 could effectively delay “zinc burning” because of the excellent synergistic effect in the thermal aging test, with a stability time as long as 140 min. At the same time, the mechanism of PVC stabilization by ZnL 2 was studied in two simple experiments, and the stabilization mechanism of ZnL 2 in PVC degradation was speculated on.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
POLYMER DEGRADATION AND STABILITY
·
2014
·
IF 2.633
Guoan Chen,Liqiang Gu,Youwei Yao
A Zn-containing complex ([ZnL 2 ]· x H 2 O, x ≈ 4, abbreviated as ZnL 2 ; HL = 1,3-dihydroxy-2-hydroxymethyl-2-(salicylidimino)propane) was synthesized and used as a thermal stabilizer . Through discoloration and dehydrochlorination tests at 180 °C, ZnL 2 was proved to be a co-stabilizer of long-term thermal stability for poly(vinyl chloride) (PVC): compared with the PVC samples stabilized using typical metallic soap stabilizers with the mass ratio of calcium stearate (CaSt 2 ) to zinc stearate (ZnSt 2 ) ranging from 1.5/0 to 0/1.5, whose induction time ( t i ), stability time ( t s ) respectively ranged from 9 to 54 min, from 12 to 56 min, the PVC samples stabilized using combinations with the mass ratio of CaSt 2 to ZnL 2 from 1.5/0 to 0/1.5 showed apparent thermal stability with t i , t s ranging from 44 to 85 min, from 49 to 88 min. PVC sample (PVC resin = 50.0 g, ZnL 2 = 1.5 g, pentaerythritol = 0.3 g, dioctyl phthalate = 2.5 g) displayed a significant long-term thermal stability with t i of 102 min, t s of 105 min, and totally-turning-black time of 170 min.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
POLYMER DEGRADATION AND STABILITY
·
2011
·
IF 2.594
Shumin Li,Youwei Yao
Zinc barbiturate [Zn(H 2 L) 2 ·2H 2 O, abbreviated as ZnL 2 ] was synthesized by a precipitation method in aqueous solution, and investigated as a co-stabilizer with calcium stearate (CaSt 2 ) for rigid poly(vinyl chloride) (PVC) by the discoloration test and the dehydrochlorination test at 180 °C. ZnL 2 exhibits high stabilizing effect with excellent initial colour of PVC films. In comparison with the synergistic effect of CaSt 2 /ZnSt 2 stabilizers, the CaSt 2 /ZnL 2 stabilizers in mass ratios ranging from 0.3/1.2 to 0.6/0.9 exhibit better synergistic effect. Moreover, PVC films stabilized by CaSt 2 /ZnL 2 show better initial colour with the addition of dibenzoyl methane as an auxiliary stabilizer . The mechanism of stabilizing action of ZnL 2 is also proposed. ZnL 2 may replace the labile chlorine atoms to interrupt the formation of conjugated double bonds in PVC chains, and act as the absorber of hydrogen chloride to restrain the self-catalytic dehydrochlorination.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2022
·
IF 16.744
Zifei Yan,Chencan Du,Yubin Wang,Jian Deng,Guangsheng Luo
Glycidyl esters, as a class of terminal epoxides, are important raw materials for the synthesis and modification of epoxy resins. Their synthetic routes via the dehydrochlorination of β-chlorohydrin esters are typically conducted under heterogeneous condition. Under the control of multiphase mass transfer, the inherently fast reaction can exhibit a very low observed reaction rate. Here we developed a continuous microflow system to determine the kinetic parameters of dehydrochlorination in the presence of aqueous NaOH solution. The same device was applied for the continuous production of glycidyl esters, and the conditions including flow velocity, alkali concentration, phase ratio and temperature were fully optimized. Comparing the obtained reaction performances in the microreactor with the conventional batch reactors, the required reaction time was shortened by 1/20 and the space–time yield was increased by 15 times, which is attributed to the mass transfer enhancement and the continuous operating mode. Finally, a mathematical model was established to calculate the volumetric mass transfer coefficients, whose value were in the range of 0.005–0.03 s −1 . The established microflow system and research methods could have high merit for guiding the kinetic studies and process intensification of other dehydrohalogenation reactions.
研究领域:
化学工程
·
有机合成
✓ 已验证
DOI
高影响因子
FUEL
·
2022
·
IF 8.035
Jinchang Liu,Yaping Li,Chenyang Shen,Maohong Fan,Qiang Xie,Dingcheng Liang
The carbonaceous pitch derived from coal liquefaction residue was controllably synthesized from the molecular dimension with a novel method, chlorination–dechlorination. The factors affecting the qualities of chlorination–dechlorination derived pitch, including chlorine ratios, were studied. The qualities of the pitches prepared with chlorination–dechlorination and the conventional thermal condensation method are compared. The carbons in the prepared carbonaceous pitch mainly exist in aromatic structures, which are oligomerized to transform dimers and trimers by chlorination–dechlorination. The C/H ratio, average molecular weight, and carbon aromaticity are increased by chlorination–dechlorination. According to the result of the simulation, the hydrogen atoms on the side chain of aromatic compounds are easier to be mono-substituted by chlorine atoms during chlorination, and then the substituting chlorine atoms connect with other hydrogen atoms to form to escape out of the reactor in the formation of hydrogen chloride during dechlorination , making the aromatic compounds oligomerize with each other. Thus, the conclusion that the chlorinated pitch has a more linear and cross-linking molecular structure is demonstrated, which is also confirmed by the results of 13 C NMR. The pitch precursors exhibit better thermal stability and thermochemical property even when the softening point has been raised to around 230 ℃ owing to the linear and cross-linking molecular structure. In addition, the pitches synthesized by the method of chlorination–dechlorination shows a more homogeneous state, while the pitch produced by thermal condensation contains a small number of powdery coke particles, and they also possess more excellent spinnability and appropriate viscosity for the process of melt-spinning. Chlorination–dechlorination can be used to achieve the controllable synthesis of the carbonaceous pitch from the molecular dimension. The properties of derived pitches are better as the addition of chlorine increases.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
Materials Research Express
·
2022
·Vol. 9
·期 2
·025305
·
IF 2.025
Long-juan Ma,Yi-heng Lu,Yan Chen,Yu-wei Lu,Gang Yuan
Understanding the influence of additives on the dehydrochlorination of plasticized poly(vinyl chloride) (PVC) from the source and long-term storage is an attractive topic. In this work, the effects of folic acid modified nano titanium dioxide (FANT), cerium stearate, organotin and β -diketone compound additives on the dehydrochlorination of plasticized PVC and long-term storage were investigated using conductivity measurements. The results showed that the induction time of hydrogen chloride removal of plasticized PVC (C-1) containing composite stabilizer at 200 °C were 243% higher than those of the control (S1). After storage, the heat stability of the control decreased significantly. Instead, the induction time and stability time of plasticized PVC containing FANT, cerium stearate, organotin and β- diketone composites were significantly enhanced at 200 °C. The thermal stability sequence from difficult to easy for removal of hydrogen chloride was : 3.0 phr (1.90% wt) (C2) >1.0 phr (0.64% wt) (C1) > 5.0 phr (3.17% wt) (C3) with FANT. It is inferred that this is due to the FANT's hydrogen bonding van der Waals force and the complexation reaction of variable valence metal Ce+3/Ce+4 with C-Cl bond in PVC polymer molecule. The induction time (min) of hydrogen chloride removal at 200 °C before and after storage is as follows: C-20 (71.9) > C-10 (70.6) > C-1 (60.7) > C-3 (57.2) > C-30 (52.7) > C-2 (49.9) > S1 (25.3) > S10 (19.7). The critical temperature for hydrogen chloride removal by the composite film is around 210 °C. If the content of FANT increased to 3.17%, the intermolecular force and repulsive force in PVC system offset each other, indicating that the increase of FANT content will lead to the increase of repulsive force with PVC. A certain amount of FANT, cerium stearate, organotin and β- diketone composites has a significant synergistic effect on the thermal stability of PVC.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
GREEN CHEMISTRY
·
2025
·
IF 9.2
Grace Dai Zhen Lee,Zifei Yan,Jing Song,Jian Deng,Guangsheng Luo
Terminal epoxides are important monomers and modifiers that are widely used in the polymer and coating industries. Apart from direct oxidation of alkenes to produce ethylene oxide or propylene oxide, many terminal epoxides are still synthesized through the chlorohydrin method. Due to the limited mass transfer performance and complex thermodynamics and kinetics in this heterogeneous reaction system, the dehydrochlorination reaction still suffers from low reaction efficiency, large amounts of solid precipitation waste, and highly excessive use of alkali. Herein, the dehydrochlorination process of 3-chloro-2-hydroxypropyl neodecanoate (CHPDA), selected as a typical β-chlorohydrin with extremely poor solubility in water, was intensified using phase transfer catalysts (PTCs). The structure–function relationship of PTCs was elucidated and it was demonstrated that tetrabutylammonium chloride (TBACl) is one of the most effective catalysts for heterogeneous dehydrochlorination. Due to the significant promotion of mass transfer by applying a catalytic amount of TBACl, the reaction time was shortened from several hours to just 3 min, and the usage of the reactant sodium hydroxide can be reduced from multiple equivalents to nearly stoichiometric with β-chlorohydrin, while the selectivities of the side products, neodecanoic acid (NDA) and diester, were only 0.4 and 1 mol%, respectively. Compared to existing works, this study could be very helpful for the development of continuous and green synthesis technology for epoxides.
研究领域:
化学工程
·
催化化学
·
绿色化学
✓ 已验证
DOI
高影响因子
ACS ES&T Engineering
·
2021
·
IF 0
Lichun Li,Xiaoli Wei,Shenglan Zhou,Zhongsheng Jia,Chuanzhao Wang,Houlin Yu,Sen Wu,Ying Li,Wenfeng Han
Hydrochlorofluorocarbon (HCFC) has been widely applied as the third-generation refrigerant globally, however, the global warming potential of such gases is often 100 and 1000 times higher than that of CO2. Dehydrochlorination reaction offers an encouraging strategy to transform the high-global-warming-potential gases of hydrochlorofluorocarbons (HCFCs) to low-global-warming-potential gases of hydrofluoroolefins (HFOs). However, the handling of a large amount of byproduct HCl remains one of the major challenges blocking the industrialization of dehydrochlorination of HCFC-142a for the production of vinylidene fluoride (VDF). A one-pot cascade reaction combining dehydrochlorination of HCFC-142b and hydrochlorination of acetylene was first proposed to spontaneously produce valuable monomers of VDF and vinyl chloride monomer (VCM) while eliminating the tedious HCl treatment step. Both thermodynamic calculations and experimental results validate the feasibility of the cascade reaction. Five different heterogeneous catalysts were screened for the proposed cascade reaction, including monocomponent catalyst BaF2, NAC, bifunctional BaF2/NAC catalyst, and bicomponent BaF2-NAC-S and BaF2-NAC-M catalysts. Among them, the mixed BaF2-NAC-M catalyst demonstrated the best catalytic performance, with BaF2 mainly acting as the dehydrochlorination site and NAC mainly acting as the hydrochlorination site. The corresponding reaction mechanism was also proposed.
研究领域:
化学工程
·
催化
·
环境化学
·
绿色化学
✓ 已验证
产品关联
DOI
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY
·
2017
·Vol. 17
·期 6
·3744-3750
·
IF 1.483
Yang Guangming,Yu Hongbo,Zhang Jianfeng,Yin Hongfeng,Ma Zhen,Zhou Shenghu
AuPd nanoparticles (NPs) protected by tetradecyl trimethyl ammonium bromide (TTAB) were coated with SiO2 through hydrolysis of tetraethylorthosilicate (TEOS). The as-synthesized AuPd@SiO2 core–shell NPs were calcined in air at 500 °C to remove TTAB and
open up mesopores within the SiO2 shells. The obtained Au–PdO@m-SiO2 NPs were reduced by H2 at 300 °C to obtain AuPd@m-SiO2 NPs with AuPd NP cores (diameter: ~3 nm) and SiO2 shells (thickness: ~18 nm). Results from relevant characterization
indicated that these SiO2-protected core–shell NPs were highly stable during calcination and subsequent reduction. Au@m-SiO2, Au10Pd@m-SiO2, Au5Pd@m-SiO2, AuPd5@m-SiO2, AuPd10@m-SiO2,
and Pd@m-SiO2 NPs with similar core sizes and shell thicknesses were also synthesized. These samples were tested in the catalytic hydrogenation of p-chloronitrobenzene. The activity and selectivity were found to be tunable, depending on the composition of the bimetallic alloys.
AuPd@m-SiO2 NPs with a 1/1 molar ratio of Au/Pd showed the highest selectivity for the hydrodechlorination of p-chloronitrobenzene.
研究领域:
材料科学
·
催化
·
化学工程
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF VINYL & ADDITIVE TECHNOLOGY
·
2021
·Vol. 28
·期 4
·696-705
·
IF 1.993
Zhimin Fu,Zhanhong Yang,Lie Deng,Yao Rong,Jian Wu
The tris(hydroxymethyl)aminomethane (THAM) and its derivative (DHD 2-([1,3-dihydroxypropan-2-ylidene]amino)-2-(hydroxymethyl)propane-1,3-diol) have been used as organic thermal stabilizers for flexible poly(vinyl chloride) (PVC). According to dehydrochlorination and discoloration tests conducted at 180°C, THAM showed to be an excellent organic thermal stabilizer for flexible PVC, not only THAM stabilizer improved the thermal stability of PVC but also maintained the initial color of the PVC. The induction time and the thermal stability time were 52 and 55.5 min, respectively. DHD can also be used as an organic thermal stabilizer for flexible PVC; however, its thermal stabilizing efficiency was not satisfactory, but it has a good synergistic effect with traditional cadmium–zinc soap stabilizers. Besides, the experiments had been performed to investigate pentaerythritol (PER) and THAM, two substances with similar structure, but such a huge difference in thermal stabilizing efficiency for flexible PVC. THAM did improve the thermal stability of PVC, both in initial whiteness and long-term thermal stability. But PER has no thermal stabilizing efficiency for PVC when used alone. At the end of the article, the probable mechanism which can give an explanation for the stabilizing efficiency given by the THAM has been proposed.
研究领域:
材料科学
·
高分子化学
·
热工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）