CHEMICAL ENGINEERING RESEARCH & DESIGN
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2020
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IF 3.35
Shaojian Hu,Jianhua Zhu,Bencheng Wu,Rui Ma,Xiaohui Li
As an eco-friendly lubricant base oil, ester base oil is receiving increasing attention. However, studies on synthetic reaction kinetics of high viscosity complex ester have been rarely reported. In this work, based on the principle of equal reactivity of all functional groups and simplified kinetics models, synthetic reaction kinetics for high viscosity complex ester was investigated in two steps. As for the esterification of trimethylolpropane with glutaric acid, the activation energies of the first and second stage were 55.3 and 73.5 kJ/mol, respectively. As for the esterification of the first step products with 2-ethylhexanoic acid, the activation energies of the first and second stage were 60.6 and 98.2 kJ/mol, respectively. As for the esterification of the first step products with n -heptanoic acid, its activation energy was 68.9 kJ/mol. A mutation phenomenon on reaction order from zero to second order was discovered, which could be explained by the strong adsorption of organic acid on catalyst surface. The conversion rate of carboxyl of synthetic reaction for mixed acid ester was estimated by simulation, and average relative error was less than 3.0%. The synthetic process of high viscosity complex ester was considered to consist of a series of parallel–consecutive reactions with addition–elimination mechanism.
研究领域:
化学工程
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环境科学
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DOI
高影响因子
MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2015
·Vol. 216
·期 5
·569-581
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IF 2.616
Ying Li,Yongjie Zhang,Qian Li,Huayi Li,Shuirong Zheng,Youliang Hu
Chain-end-functionalized polyethylenes (Cef-PEs: PE S SH (Cef 1 ), PE S furfuryl (Cef 2 ), PE S NH 2 (Cef 4 ), PE S NH 2 •HCl (Cef 5 ), PE S COONa (Cef 6 ), PE S CHA(Cef 7 ), PE S SO 3 Na (Cef 8 ), PE S OH (Cef 9 ) and PE S COOH (Cef 10 )) are synthesized by thiol-ene addition of vinyl-terminated polyethylene (v-PE) with 1,2-ethanedithiol, furfurylmercaptan, cysteamine, cysteamine hydrochloride, sodium thioglycolate, L-cysteine hydrochloride, sodium 2-mercaptoethanesulfonate, mercaptoethanol, and thioglycolic acid, respectively. PE S t NCO (Cef 3 ) is obtained by subsequent reaction of Cef 9 with anhydrous 4,4′-MDI. Cef-PE 1–8 are reported for the first time. The conversions of all the reactions are up to 95%–100%. All the Cef-PEs are characterized by NMR, GPC, DSC, FT-IR, and TGA. In the experiments, it is found that alkaline mercaptans and solvents are adverse to the thiol-ene click reactions.
研究领域:
高分子化学
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材料科学
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DOI
高影响因子
CATALYSIS LETTERS
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2020
·Vol. 150
·期 8
·2437-2445
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IF 2.482
Yang Zhi,Luo Mingsheng,Liu Qinglong,Shi Buchang
A potassium- and copper-modified iron-based catalyst (K–Cu–Fe/SiO 2 ) was synthesized by the co-precipitated method. The general structural properties of the catalyst were characterized with various techniques, including SEM, XRD, H 2 -TPR, N 2 adsorption–desorption and Raman spectroscopy. The results reveal that the fresh catalyst is mainly composed of α-Fe 2 O 3 phase with rod-shaped morphology formed by nanoparticles. The effect of activation process on the Fischer–Tropsch synthesis catalytic performance was then investigated. It shows that activation process has an important influence on the reactive stability. The in situ XRD and in situ Raman spectroscopy were used to study the structural changes of the Fe-based catalyst during reduction and reaction processes. The Fe 2 C iron carbide as the main active phase was observed after reduction process. Graphic Abstract
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
Catalysts
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2022
·Vol. 12
·期 2
·205
·
IF 4.501
Haodong Tang,Xiali Zheng,Yun Yu,Jinxin Liang,Yifan Zheng,Zongjian Liu
SiO2encapsulated SnZnCu microspheres (several micrometers to about 30 μm in diameter) with very low undercooling, narrow freezing/melting range, and high thermal cycling stability have been produced and used as the temperature stabilizer of the packed bed in highly exothermic Fischer–Tropsch reaction. The core–shell structured SnZnCu@SiO2microspheres are prepared in a two-step way, namely SnZnCu microspheres are firstly produced via a molten LiCl–KCl–CsCl eutectic-based metal emulsion method, and then a sol–gel approach is employed to coat them with a uniform, anti-leakage SiO2layer. It is found that raising the amount of Zn to 4.0 at.% is critical for achieving a very low undercooling (<5 °C for SnZn0.04Cux@SiO2vs. about 84 °C for Sn@SiO2) and a narrow freezing/melting peak width, and both undercooling and peak width are almost unchanged as the Cu content (x) increases from 1.5 to 3.0 at.%. However, their thermal cycling stability depends positively on the amount of Cu and can be remarkably improved when 3.0 at.% Cu is added. The results also show that low undercooling and narrow freezing/melting peak width are associated with the formation of Sn–Zn–Cu ternary eutectic and metastable phase Cu5Zn8, and poor thermal cycling stability of SnZn0.04Cux@SiO2microspheres with low Cu content is related to the decomposition of Cu5Zn8during thermal cycling. By embedding thermally stable SnZn0.04Cu0.03@SiO2microspheres into the Co/SiO2catalyst for Fischer–Tropsch synthesis, the temperature gradient in the catalyst bed can be significantly reduced by suppressing the formation of hot spots or thermal runaway and thus rapid deactivation of Co catalyst that occurs in the SnZn0.04Cux@SiO2-absent Co/SiO2catalyst can be avoided.Keywords:exothermic reaction;microcapsules;phase change materials;SiO2;Sn–Zn–Cu
研究领域:
材料科学
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化学工程
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DOI
高影响因子
THERMOCHIMICA ACTA
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2018
·
IF 2.189
Zichao Guo,Shiran Li,Peng Zhou,Liping Chen,Wanghua Chen
Semibatch reactors (SBRs) are commonly used to conduct exothermic reaction in the pharmaceutical and fine chemical industries. From the thermal safety point of view, low MTSR (maximum temperature of synthesis reactions) is desirable. We have found that MTSR vs process temperature ( T ) profile favorably present S-shape in isothermal homogeneous SBRs involving highly exothermic or slow reactions. However, the criterion to determine the dependency of MTSR on T has been not thoroughly studied. In this work, such a theoretical criterion will be developed based on the fact that the derivative of MTSR to T is zero at the reaction temperature at which the lowest value of MTSR is obtained and experimentally validated by the hydrolysis reaction of acetic anhydride. To develop such a criterion, the quantitative relationship between the maximum accumulation X ac,max and Damköhler number ( Da ) for isothermal homogeneous semibatch reactions of arbitrary kinetic orders is first developed and numerically verified.
研究领域:
化学工程
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制药工程
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反应动力学
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DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2015
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IF 2.587
Zi-Chao Guo,Lin Hao,Wen-Shuai Bai,Rui Wang,Hong-Yuan Wei
Maximum temperature of synthesis reaction (MTSR), which is a function of the process temperature (Tp) and the maximum accumulation (Xac,max), is an important criterion for process hazard assessment and reactor design. For isothermal reactions, Xac,max is influenced by kinetics, thermodynamics and operating conditions. To analyze the behaviors of MTSR and Xac,max, a mathematical model for isothermal homogeneous semibatch reactors is proposed. The influence of several dimensionless parameters (νADaRE, γ, Δτ) and reaction orders on MTSR and Xac,max are also studied. It is found that the MTSR curves for slow and highly exothermic reactions tend to present a “S” shape. On the basis of the above analysis, a semiempirical criterion is suggested to quantificationally decide whether the MTSR curves are monotonously increasing or not. A typical esterification reaction is conducted to validate the proposed model and the semiempirical criterion. Applications using the mathematical model and the criterion in hazard assessment and process optimization are also discussed.
研究领域:
化学工程
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过程安全
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产品关联
DOI
高影响因子
Processes
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2022
·Vol. 10
·期 9
·1738
·
IF 3.352
Jingjing Liu,Juanli Shi,Bo Zhang,Zhenmin Cheng
Three novel magnetically-recoverable solid acid catalysts (hydrophobic catalysts Fe3O4@SiO2-Me&PrSO3H, Fe3O4@SiO2-Oc&PrSO3H and hydrophilic catalyst Fe3O4@SiO2-PrSO3H) were synthesized by introducing organic propylsulfonic acid and alkyl groups to Fe3O4@SiO2nanocomposites. We characterized these catalysts by FT-IR, EDS, XRD, VSM and SEM, and found that they had excellent core-shell structure and magnetic responsiveness. We also explored the impact of surface hydrophobicity on activity and stability of catalysts in ethyl acetate (EAC) synthesis reaction. The results indicated that: for reactivity and reusability, Fe3O4@SiO2-Oc&PrSO3H > Fe3O4@SiO2-Me&PrSO3H > Fe3O4@SiO2-PrSO3H. This was because octyl and methyl groups could build a hydrophobic layer on the surfaces of Fe3O4@SiO2-Oc&PrSO3H and Fe3O4@SiO2-Me&PrSO3H, and this could effectively prevent water molecules from poisoning active sites; the hydrophobicity of octyl was stronger than methyl. Fe3O4@SiO2-Oc&PrSO3H also showed higher catalytic activity in the external aqueous reaction system, which indicated that it had good water toleration. Moreover, we could easily separate Fe3O4@SiO2-Oc&PrSO3H from the reaction mixture with an external magnetic field, in the meanwhile, its reactivity could still remain above 80% after reusing 6 times.
研究领域:
化学工程
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催化材料
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DOI
高影响因子
JOURNAL OF LOSS PREVENTION IN THE PROCESS INDUSTRIES
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2015
·
IF 1.406
L. Zhang,W.D. Yu,X.H. Pan,J.J. Fang,M. Hua,F.M. Chen,J.C. Jiang
The exothermic oxidation of 3-methylpyridine with hydrogen peroxide was analyzed by Reaction Calorimeter (RC1e) in semi-batch operation. Heat releasing rate and heat conversion were studied at different operating conditions, such as reaction temperature, feeding rate, the amount of catalyst and so on. The thermal hazard assessment of the oxidation was derived from the calorimetric data, such as adiabatic temperature rise (ΔT ad ) and the maximum temperature of synthesis reaction (MTSR) in out of control conditions. Along with thermal decomposition of the product, the possibility of secondary decomposition under runaway conditions was analyzed by time to maximum rate (TMR ad ). Also, risk matrix was used to assess the risk of the reaction. Results indicated that with the increase of the reaction temperature, the reaction heat release rate increased, while reaction time and exotherm decreased. With the increase of feeding time, heat releasing rate decreased, but reaction time and exotherm increased. With the amount of the catalyst increased, heat releasing rate increased, reaction time decreased and exothermic heat increased. The risk matrix showed that when the reaction temperature was 70 °C, feeding time was 1 h, and the amount of catalyst was 10 g and 15 g, respectively, the reaction risk was high and must be reduced.
研究领域:
化学工程
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安全科学
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产品关联
DOI
高影响因子
ORGANIC PROCESS RESEARCH & DEVELOPMENT
·
2018
·
IF 3.584
Juncheng Jiang,Fusheng Cui,Saili Shen,Xiuxia Guo,Lei Ni,Yong Pan
In this study, in order to assess thermal runaway risk of two step synthesis reactions, two new risk assessment methods were proposed by combining the new assessment procedure with the risk matrix and the Stoessel criticality diagram. The thermal runaway risks of the tert-butyl peroxybenzoate (TBPB) synthesis process and the tert-butyl peracetate (TBPA) synthesis process, and the influence of the use of the pure target products on the assessment results were also studied by the new methods. The results showed that the new methods could obtain more accurate assessment results of two step synthesis reactions. Some measures should be taken to reduce the thermal runaway risks of the two synthesis processes. Furthermore, the use of the pure target products in the new methods would exaggerate the thermal runaway risks of the two step synthesis reactions.
研究领域:
化学工程
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安全科学
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过程安全
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DOI
高影响因子
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
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2022
·Vol. 147
·期 20
·11467-11475
·
IF 4.755
Ma Xiao‑Hua,Hu Jie,Li Quan‑Guo,Li Peng,Liu Xuan,Yan Xiao-Min,Cheng Chun-Sheng,Li San-Xi
This study describes the apparent thermodynamics and reaction kinetics of the synthesis of [(5,6-dimethyl dicarboxylate-3-pyridine) methyl]-trimethyl ammonium bromide (DPTAB) and established a reaction kinetics model firstly. Simultaneous thermal analysis coupled with Fourier transform infrared and mass spectrometry (STA-FTIR-MS) was utilized to study the mechanism of the decomposition reaction of DPTAB firstly also. The finding is that the apparent activation energy of the synthesis reaction of DPTAB is 69.27 kJ mol −1 , and the apparent reaction heat is –74.46 kJ mol −1 (based on the moles of dimethyl 5-bromomethylpyridine-2,3-dicarboxylate). Under thermal runaway conditions, the adiabatic temperature rise is 8.87 K. The synthesis reaction kinetic equation is \(r=5.876\times {10}^{13}\cdot \mathrm{exp}\left(-69.27/RT\right)\cdot {C}_{\mathrm{CMPE}}^{ 0.893}\cdot {C}_{\mathrm{TMA}}^{ 1.136}\) . Under a nitrogen atmosphere, the decomposition of DPTAB undergoes an endothermic melt accompanied by an exothermic decomposition process. The decomposed products, trimethylamine reacts with bromomethane further to form tetramethylammonium bromide salt that undergoes an endothermic sublimation at 583 K, and the enthalpy of sublimation is 72.92 kJ mol −1 .
研究领域:
化学动力学
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材料科学
·
热分析
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产品关联
DOI
高影响因子
JOURNAL OF LOSS PREVENTION IN THE PROCESS INDUSTRIES
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2021
·
IF 3.66
Qiang Chen,Yuqing Ni,Jun Liang,Lei Ni,Juncheng Jiang,Yong Pan,Qingsheng Wang
Esterification reactions between anhydrides and alcohols catalyzed by sulfuric acid have broad applications in the food, cosmetic, and pharmaceutical industries. However, the exothermic behavior cannot be well explained, especially in semibatch reactors with different feeding procedures. In this study, a series of esterification processes in semibatch systems were conducted with a wide range of feeding rates with two different substrates. The structures of initial catalytic substrates were characterized using in situ Fourier Transform Infrared (FTIR) spectroscopy. A total of 11 reaction pathways, including those for the initial activation of substrates and the subsequent reactions of the feeding process, were calculated by the density functional theory (DFT) method. Three possible catalytic cycles of the esterification with specific acid catalysis, protonated intermediate, and protonated intermediate and H 2 O, were established for the semibatch esterification reaction based on calculated results and experimental evidence. Thermal safety parameters such as reaction enthalpy ( Δ H r ), adiabatic temperature rise ( Δ T r , a d ), and maximum temperature of the synthetic reaction (MTSR) were determined based on Wilson equation used to calibrate mixing heat. The results reveal that mixing heat was 2.5 kJ/mol with same mole ratio of n -butanol ( n B) and propionic anhydride (PA). The reactions started by PA are dominant, no matter whether the substrate is n B or PA. The initial reaction rate is restricted by the low concentration of catalyst and active reactant when n B is used as substrate, which lead to significant reactant accumulation with high MTSR of approximately 160 °C. Furthermore, feeding n B into PA allows a controllable increase in the Δ T r , a d realized by changing the feeding rate and limiting the accumulation of reactant.
研究领域:
化学工程
·
物理化学
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过程安全
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产品关联
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2022
·
IF 7.392
Chunhua Du,Yue Chen,Song He,Chichi Ruan,Xinyu Liu,Chunxiang He,Xin Jin,Qilin Chen,Yuansheng Ma,Guanyu Chen
This paper reported the preparation of ultra-flexible silica aerogels based on diene synthesis reaction at atmospheric pressure. Vinyl trimethoxy silane and vinyl methyl dimethoxy silane as silicon source were used to prepare vinyl aerogels by one-pot acid-base sol–gel route. The diene synthesis reaction was used to prepare ultra-flexible and super hydrophobic silica aerogels on the basis of vinyl aerogels. Maximum strain of the ultra-flexible aerogels is as high as 90 % for 20 compression-decompression cycles. The aerogels can be recovered completely without structure destruction. In addition, the adsorption capacity of the samples is higher than that of the conventional silica aerogels, which can reach to 15.0 g⋅g −1 of dichloromethane. It is worth noting that they also have efficient cycle performance for adsorption and filtration. Acting as core part of filtration, the organic solvents insoluble in water can be easily separated from water by the aerogels.
研究领域:
材料科学
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化学工程
·
环境科学
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）