Study on trifluoromethanesulfonic acid-promoted synthesis of daidzein: Process optimization and reaction mechanism

Daidzein has been widely used in pharmaceuticals,nutraceuticals,cosmetics,feed additives,etc.Its preparation process and related reaction mechanism need to be further investigated.A cost-effective process for synthesizing daidzein was developed in this work.In this article,a two-step synthesis of daidzein(Friedel–Crafts acylation and[5+1]cyclization)was developed via the employment of trifluoromethanesulfonic acid(TfOH)as an effective promoting reagent.The effect of reaction conditions such as solvent,the amount of TfOH,reaction temperature,and reactant ratio on the conversion rate and the yield of the reaction,respectively,was systematically investigated,and daidzein was obtained in 74.0%isolated yield under optimal conditions.Due to the facilitating effect of TfOH,the Friedel–Crafts acylation was completed within 10 min at 90℃ and the[5+1]cyclization was completed within 180 min at 25℃.In addition,a possible reaction mechanism for this process was proposed.The results of the study may provide useful guidance for industrial production of daidzein on a large scale.

Reaction mechanism and kinetics of pressurized pyrolysis of Chinese oil shale in the presence of water

A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.

The dynamic changes and mechanisms of Rehmanniae radix processing based on Maillard reaction

Background:Traditional Chinese medicines are usually processed before they are used for clinical treatment.This is done in a way associated with the Maillard reaction.Methods:Based on the Maillard reaction,this paper analyzed the degree of processing of rehmannia root(Rehmanniae radix)relative to the dynamic variation rules of Maillard reaction index parameters,including pH,A420,amino acids,and 5-hydroxymethylfurfural.Furthermore,this study introduced thermal analysis techniques and pyrolysis kinetics to assess the influence of the correlation between processing raw rehmannia root and the Maillard reaction during carbonization.It then went through the whole process of transforming the raw material to end-product in order to explain the scientific connotation of processing it.Results:The results showed that each time rehmannia root was processed,its pH value and amino acid content decreased,while the A420 value and 5-HMF increased.Processing with wine shows a significant difference in these experimental indexes.The position and intensity of the maximum thermal weight loss rate peak of processed rehmannia root at different degrees of processing are different.Comprehensive quantitative 221±0.2°C for processed rehmannia root carbonization was the processing temperature limit.Moreover,the kinetic solution verified that the activation energy corresponding to the carbonization temperature was close to the maximum value of the activation energy of the whole carbonization process,and the optimal mechanism function was g(α)=((1−α)−1/3−1)2.Conclusion:The Maillard reaction occurred during the processing of rehmannia root mixed with carbonization.With each increase of the number of steaming and drying cycles involved in the processing,the level of Maillard reaction increased significantly.The wine-steaming method had a significant effect on the quality of the processed product.

Dimensionality Reduction with Input Training Neural Network and Its Application in Chemical Process Modelling

Many applications of principal component analysis (PCA) can be found in dimensionality reduction. But linear PCA method is not well suitable for nonlinear chemical processes. A new PCA method based on im-proved input training neural network (IT-NN) is proposed for the nonlinear system modelling in this paper. Mo-mentum factor and adaptive learning rate are introduced into learning algorithm to improve the training speed of IT-NN. Contrasting to the auto-associative neural network (ANN), IT-NN has less hidden layers and higher training speed. The effectiveness is illustrated through a comparison of IT-NN with linear PCA and ANN with experiments. Moreover, the IT-NN is combined with RBF neural network (RBF-NN) to model the yields of ethylene and propyl-ene in the naphtha pyrolysis system. From the illustrative example and practical application, IT-NN combined with RBF-NN is an effective method of nonlinear chemical process modelling.

Lagrangian simulation of multi-step and rate-limited chemical reactions in multi-dimensional porous media

Management of groundwater resources and remediation of groundwater pollution require reliable quantification of contaminant dynamics in natural aquifers, which can involve complex chemical dynamics and challenge traditional modeling approaches. The kinetics of chemical reactions in groundwater are well known to be controlled by medium heterogeneity and reactant mixing, motivating the development of particle-based Lagrangian approaches. Previous Lagrangian solvers have been limited to fundamental bimolecular reactions in typically one-dimensional porous media. In contrast to other existing studies, this study developed a fully Lagrangian framework, which was used to simulate diffusion-controlled, multi-step reactions in one-, two-, and three-dimensional porous media. The interaction radius of a reactant molecule, which controls the probability of reaction, was derived by the agent-based approach for both irreversible and reversible reactions. A flexible particle tracking scheme was then developed to build trajectories for particles undergoing mixing-limited, multi-step reactions. The simulated particle dynamics were checked against the kinetics for diffusion-controlled reactions and thermodynamic wellmixed reactions in one-and two-dimensional domains. Applicability of the novel simulator was further tested by(1) simulating precipitation of calcium carbonate minerals in a two-dimensional medium, and(2) quantifying multi-step chemical reactions observed in the laboratory. The flexibility of the Lagrangian simulator allows further refinement to capture complex transport affecting chemical mixing and hence reactions.

Opinion: Chemical--Mesoscopics..for the Mesoparticles Reactivity Explanation

The estimation of chemical particles reactivity and the determination of chemical reactions direction are the actual theme in new scientific trend-Chemical Mesoscopics.Paper includes the proposal about the using the theory of free energy linear dependence from physical organic chemistry and their applications for prognosis of reactions flowing.The semi-empiric constants is given according to mesoscopic physics definitions as well as the transformed Kolmogorov-Avrami equation is discussed.It is the development of Chemical Mesoscopics for organic reactivity estimation including nanostructures reactivity.

Chemical looping gasification of maceral from low-rank coal: Products distribution and kinetic analysis on vitrinite

The product distribution and kinetic analysis of low-rank coal vitrinite were investigated during the chemical looping gasification(CLG)process.The acid washing method was used to treat low-rank coal,and the density gradient centrifugation method was adopted to obtain the coal macerals.By combining thermogravimetric analysis and online mass spectrometry,the influence of the heating rate and oxygen carrier(Fe2O3)blending ratio on product distribution was discussed.The macroscopic kinetic parameters were solved by the Kissinger-Akahira-Sunose(KAS)method,and the main gaseous product formation kinetic parameters were solved by the iso-conversion method.The results of vitrinite during slow heating chemical looping gasification showed that the main weight loss interval was 400–600℃,and the solid yield of sample vitrinite-Fe-10 at different heating rates was 64.30%–69.67%.When b=20℃·min^(-1),the maximum decomposition rate of vitrinite-Fe-10 was 0.312%min1.The addition of Fe2O_(3)reduced the maximum decomposition rate,but by comparing the chemical looping conversion characteristic index,it could be inferred that the chemical looping gasification of vitrinite might produce volatile substances higher than the pyrolysis process of vitrinite alone.The average activation energy of the reaction was significantly reduced during chemical looping gasification of vitrinite,which was lower than the average activation energy of 448.69 kJ·mol^(-1) during the pyrolysis process of vitrinite alone.The gaseous products were mainly CO and CO_(2).When the heating rate was 10℃·min^(-1),the highest activation energy for CH4 formation was 21.353 kJ·mol^(-1),and the lowest activation energy for CO formation was 9.7333 kJ·mol^(-1).This study provides basic data for exploring coal chemical looping gasification mechanism and reactor design by studying the chemical looping gasification process of coal macerals。

Recent Research Progress of Chemical Reactions under Supercritical Conditions

Chemical reactions (such as hydrogenation, hydroformylation, alkylation, esterification, etc.) at supercritical conditions afford opportunities to manipulate the solubility of reactants and products, to eliminate interphase transport limitations in the reaction systems, and to be beneficial to the environment. This review concentrates on the most recent developments after 2001 with only a brief summary of pioneering research work before 2001.

Numerical Analysis on Wood Pyrolysis in Pre-Vacuum Chamber

In the previous experimental work, a new technology system for wood pyrolysis was developed to aim at mitigating climate change, global warming, and energy crisis as well as enhancing low electrification in rural areas in developing countries. The new technology system equipped with a pre-vacuum chamber requires low cost and less maintenance. However, large wood pyrolysis in the pre-vacuum chamber is rather complicated. To obtain a good understanding of the previous experimental results, a numerical analysis taking account of heat-mass transfer and chemical reaction is carried out. Two-step general reaction model is proposed for the numerical analysis. The first stage is volatile and char formation from the wood pieces and the second state is decomposition of the volatile to five species including vapor of tar. In this analysis, chemical formulae of the volatile and the tar are successfully identified hypothetically. The results obtained by this numerical analysis can explain the experimental results reasonably and provide useful information about time evolution of volatile formation, temperature change in pre-vacuum chamber with time, and species mole concentration decomposed from the volatile.

Surface-Driven High-Pressure Processing

The application of high pressure favors many chemical processes, providing higher yields or improved rates in chemical reactions and improved solvent power in separation processes, and allowing activation barriers to be overcome through the increase in molecular energy and molecular collision rates. High pressures-up to millions of bars using diamond anvil cells-can be achieved in the laboratory, and lead to many new routes for chemical synthesis and the synthesis of new materials with desirable thermody- namic, transport, and electronic properties. On the industrial scale, however, high-pressure processing is currently limited by the cost of compression and by materials limitations, so that few industrial processes are carried out at pressures above 25 MPa. An alternative approach to high-pressure processing is pro- posed here, in which very high local pressures are generated using the surface-driven interactions from a solid substrate. Recent experiments and molecular simulations show that such interactions can lead to local pressures as high as tens of thousands of bars （1 bar=1×10^5 Pa）, and even millions of bars in some cases. Since the active high-pressure processing zone is inhomogeneous, the pressure is different in dif- ferent directions. In many cases, it is the pressure in the direction parallel to the surface of the substrate （the tangential pressure） that is most greatly enhanced. This pressure is exerted on the molecules to be processed, but not on the solid substrate or the containing vessel. Current knowledge of such pressure enhancement is reviewed, and the possibility of an alternative route to high-pressure processing based on surface-driven forces is discussed. Such surface-driven high-pressure processing would have the advantage of achieving much higher pressures than are possible with traditional bulk-phase processing, since it eliminates the need for mechanical compression. Moreover, no increased pressure is exerted on the containing vessel for the process, thus eliminating concerns about materials failure.

Phase and chemical state tuning of FeNi oxides for oxygen evolution reaction

Advancing and deploying the Fe Ni-based catalyst,the state-of-the-art pre-electrocatalysts,for oxygen evolution reactions(OER)still suffer from unclear chemical state correlation to the catalytic ability,as evidenced by the variedly reported performance for the different Fe Ni structures.Herein,we contributed the phase and redox chemical states tuning of Fe Ni oxides by the surface microenvironment regulation for the OER catalysis that was realized by the urea-assisted pyrolysis and molybdenum-doping technique by integrating molybdenum into the iron–nickel metal-organic precursor.Driven by the complicated and compromised atmosphere,namely,the oxidation state driven by the Mo doping and reduction ability induced by the urea-assisted pyrolysis,could transfer confined Fe Ni oxides to hybrid phases of Fe_(2)O_(3)and FeNi_(3)alloy,and the resultant compromised chemical states by the charge redistribution imparted very high electrocatalytic performance for OER compared with the control samples.The insitu Raman spectroscopy and post-XPS analysis confirmed the facile Fe/Ni oxyhydroxide active phase formation resulting from the proper phase and chemical states,and theoretical analysis disclosed the microenvironment regulation resulting in the charge redistribution forming the electron accumulation and depletion sites to accelerate the oxygen-species to oxyhydroxide-species transformation and enhance the electronic state density near the Fermi level by significantly reducing the energy barrier.The work not only showed the importance of surface chemical state tunning that can basically answer the varied performance of Fe Ni catalysts but also revealed an effective approach for fine-tuning their catalytic properties.

Transport-Reaction Process in the Reaction of Flue Gas Desulfurization

A theoretical investigation was conducted to study the transport-reaction process in the spray-drying flue gas desulfurization. A transport-reaction model of single particle was proposed, which considered the water evaporation from the surface of droplet and the reaction at the same time. Based on this model, the reaction rate and the absorbent utilization can be calculated. The most appropriate particle radius and the initial absorbent concentration can be deduced through comparing the wet lifetime with the residence time, the result shows in the case that the partial pressure of vapor in the bulk flue gas is 2000Pa, the optimum initial radius and absorbent concentration are 210～310 μ m and 23% respectively. The model can supply the optimum parameters for semi-dry FGD system designed.

Multiple objectives application approach to waste minimization

Besides economics and controllability, waste minimization has now become an objective in designing chemical processes, and usually leads to high costs of investment and operation. An attempt was made to minimize waste discharged from chemical reaction processes during the design and modification process while the operation conditions were also optimized to meet the requirements of technology and economics. Multiobjectives decision nonlinear programming (NLP) was employed to optimize the operation conditions of a chemical reaction process and reduce waste. A modeling language package-SPEEDUP was used to simulate the process. This paper presents a case study of the benzene production process. The flowsheet factors affecting the economics and waste generation were examined. Constraints were imposed to reduce the number of objectives and carry out optimal calculations easily. After comparisons of all possible solutions, best-compromise approach was applied to meet technological requirements and minimize waste.

化工过程中的电子传递、质子传递和分子传递

随着“绿色化学”和“可持续发展”概念以及“碳达峰、碳中和”(双碳)目标的相继提出与推进,化学工业逐步进入绿色化、高端化、智能化发展新阶段。对于包含反应的化工过程有非常经典的“三传一反”理论,以反应动力学为核心,以动量传递、热量传递与质量传递为基础,揭示了物质、能量传递与化学反应的协同强化规律,对化工领域的发展具有重要和深远意义。近年来,由于光能、电能等清洁能源以及绿色生物制造、光电化学工程等新学科引入化工反应过程中,以电子传递、质子传递和分子传递为代表的三类传递现象得到了广泛关注和大量研究,为“三传一反”理论注入了新的活力。在此背景下,尝试将电子传递、质子传递和分子传递三类现象进行分析和介绍,针对不同化学反应的特点,初步总结了通过电子传递、质子传递和分子传递过程的单独或协同强化,以实现传递过程与化学反应过程的高度匹配,进而实现化学反应效率的显著提升。

基于学生能力培养的化学反应工程课堂教学设计与探索

化学反应工程是化学工程与工艺专业的核心必修课。为了提高化学反应工程的教学质量,教学团队总结多年的教学经验,结合学生学习过程中的难点,对课堂教学过程进行精心设计并进行了教学探索。通过丰富教学课件,习题讨论和课模作品分享增加学生自主学习的能力;采用多元化的评价方式鼓励学生参与课堂教学内容。在整个教学过程中注重培养化工专业学生的工程思维和分析解决实际问题的能力。

三氨基甲苯的工程化合成工艺及其反应安全性

以2,4,6-三硝基甲苯(TNT)为原料,商业钯碳(Pd/C)为催化剂,通过催化氢化实现了一种芳香多胺类化合物——2,4,6-三氨基甲苯(TAT)的规模化合成。采用红外光谱、核磁共振波谱、高分辨质谱测试证明成功合成了TAT。当TNT用量为1 kg,乙酸乙酯用量为10 L时,TAT合成反应的最优工艺参数为:5%Pd/C用量40 g(干料)、反应温度60℃、氢气压力1 MPa、搅拌速率650 r·min^(-1)。TNT氢化反应安全性研究表明:TNT氢化反应为放热反应,平均放热速率为38.2 W·kg^(-1),绝热温升为150.85℃,不存在由于其反应失控而引发二次分解反应的可能性。

化学反应工程教学改革与实践

化学反应工程课程涉及多学科知识,对学生学习基础要求较高,传统教学模式难以满足高效课堂的要求。采用线上线下混合式教学,提高学生学习积极性。改革成绩评价方式,增加过程性考核比重,学生学习成绩得到改善。理论教学与专业实验环节相结合,提升学生的综合实践能力,近三年学生在化工专业学科竞赛中获得省级以上奖项40余项。改革效果明显。

以重油加氢实例展示化工过程分析与合成课程中稳态模拟的正、逆问题求解

本文采用了一种基于数值计算的稳态模拟方法,结合实验获取的重质油加氢脱硫实验数据和模型假设,使用数学模型进行“正、逆问题”求解。通过对重油加氢实例的研究,首先实现了重质油加氢脱硫模型的建立,进而基于实验数据求解了稳态模拟的“逆问题”;其次又基于所建立模型及拟合得到的参数完成了稳态模型“正问题”的求解。“正、逆问题”的求解逻辑,不仅是一种有效的科研手段,更是一项脱胎于工程实际案例的教学素材。通过深入探讨重油加氢实例,并结合正、逆问题求解方法,我们可以为学生提供更全面、系统的化工知识和能力培养。

热解-芬顿法处理聚乳酸技术研究

采用高温高压热解和芬顿氧化相结合的方法处理聚乳酸材料,通过X射线衍射和红外光谱等方法对材料进行了表征分析,并研究了热解温度、芬顿反应时间、溶液pH、H_(2)O_(2)和七水合硫酸亚铁(FeSO_(4)·7H_(2)O)投加量对处理后溶液化学需氧量(COD)的影响。结果表明,水热反应温度达到200℃时,聚乳酸可以完全热解;当溶液pH=3、H_(2)O_(2)投加量为55.2mL、FeSO_(4)·7H_(2)O投加量为21g时,通过芬顿反应可以将热解后溶液COD值由105000mg/L降低至287mg/L。

基于辩证唯物主义认识论略谈化学工程学科发展

为培养学生关于化学工程学科的系统观、整体观、历史发展观,进而对学科内容有更深入的理解,提高其工程思维能力,基于辩证唯物主义认识论原理,系统地阐述了学科创立的基本条件和辩证发展过程。统一的研究对象、统一的研究方法是学科创立的基本前提,大规模化的化工生产过程是化学工程学科建立和发展的客观依据。化工生产过程通常由物理和化学两类不同性质的过程构成,对物理过程的研究建立了化工原理分支学科,对化学过程的研究建立了化学反应工程学科。任何过程总是包括两个方面,即过程的方向、极限及过程的速率,依据对过程方向、极限的研究建立了化工热力学分支学科,对速率的研究则是属于化工原理和化学反应工程的内容。学科的研究方法通常可分为数学解析法、数学模型法及经验法三类,不同分支学科所采取的研究方法往往各有侧重、各具特色,如传递过程偏重数学解析法,化学反应工程主要采取数学模型法,化工原理则以经验法为主要特色。基于唯物辩证法,系统地阐述了学科的辩证发展过程,学科的发展是其自身的自我否定,完整的辩证发展过程必然经历两次否定,才能达到自身完善。化学工程学科正是经历了从综合到分解,再由分解到综合的两次否定过程,到化工系统工程创立,最终形成了完整的学科体系,从而完美地诠释了辩证唯物主义的科学性和真理性。唯物辩证法为我们培养正确的学科发展观提供了根本的方法依循。