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.

100 W-class green hydrogen production from ammonia at a dual-layer electrode containing a Pt-Ir catalyst for an alkaline electrolytic process

Ammonia allows storage and transport of hydrogen over long distances and is an attractive potential hydrogen carrier.Electrochemical decomposition has recently been used for the conversion of ammonia to hydrogen and is regarded as a future technology for production of CO_(2)-free pure hydrogen.Herein,a heterostructural Pt-Ir dual-layer electrode is developed and shown to achieve successful long-term operation in an ammonia electrolyzer with an anion exchange membrane(AEM).This electrolyzer consisted of eight membra ne electrode assemblies(MEAs)with a total geometric area of 200 cm~2 on the anode side,which resulted in a hydrogen production rate of 25 L h~(-1).We observed the degradation in MEA performance attributed to changes in the anode catalyst layer during hydrogen production via ammonia electrolysis.Furthermore,we demonstrated the relationship between the ammonia oxidation reaction(AOR)and the oxygen evolution reaction(OER).

Reaction pathway led by silicate structure transformation on decomposition of CaSiO_3 in alkali fusion process using NaOH

The mechanism of decomposition of calcium inosilicate(CaSiO_3) synthesized through chemical deposition method using analytical reagent NaSiO_3·9H_2O and CaCl_2 during the alkali fusion process using NaOH was investigated by Raman spectroscopy in situ,X-ray diffraction and Fourier transform infrared spectrometer(FTIR).The results show that the tetrahedral silica chains within CaSiO_3 are gradually disrupted and transformed into nesosilicate with the isolated SiO_4 tetrahedra at the beginning of the alkali fusion process.The three intermediates including Ca_2SiO_4,Na_2CaSiO_4 and Na_2SiO_3 appear simultaneously in the decomposition of CaSiO_3,while the final products are Ca(OH)_2 and Na_4SiO_4.It can be concluded that there exist two reaction pathways in the alkali fusion process of CaSiO_3:one is ion exchange,the other is in the main form of the framework structure change of silicate.The reaction pathway is led by silicate structure transformation in the alkali fusion process.

Reaction Process of Chromium Slag Reduced by Industrial Waste in Solid Phase

M, a particular industrial waste, was selected to detoxify chromium slag at a high temperature. The carbon remaining in M reduced Cr （ Ⅳ ） of Na2 CrO4 borne in the chromium slag to Cr （ Ⅲ ） in the solid phase reaction, and its thermodynamics and kinetics were studied. The reduction process of Na2CrO4 by carbon produced CO, whiCh＇was endothermic. Under the experimental condition, the apparent activation energy was 4. 41 kJ·mol^-1 , the＇apparent order of reaction for Na2 CrO4 was equal to one, and the partial pressure of CO was only 0.22 Pa at 1 330℃.

The influence of intimacy on the ’iterative reactions’ during OX-ZEO process for aromatic production

The oxide-zeolite process provides a promising way for one-step production of aromatics from syngas,whereas the reasons for the dramatic effect of intimacy between oxide and zeolite in the composite catalyst on the product selectivity are still unclear. In order to explore the optimal intimacy and the essential influence factors, ZnCrOxcombined with ZSM-5 are employed to prepare the composite catalysts with different distances between the two components by changing the mixing methods. An aromatic selectivity of 74%(with CO conversion to be 16%) is achieved by the composite catalyst when the intimacy is in the range of nanometer. A so-called ‘iterative reactions’ mechanism of intermediates over oxides is then proposed and studied: the intermediate chemical can undergo a hydrogenation reaction on oxide.So the shorter the intermediates stay on oxide, the more of chance for C-C coupling takes place on zeolite to form aromatics. Moreover, the aero-environments of reaction is found to impact on the extent of iterative reaction as well. Therefore, when the intimacy between the two components changes, the extent of iterative reactions vary, resulting in alteration of product distribution. This work provides new insight in understanding the mechanisms during the complex process of OX-ZEO composite catalysis and sheds light to the design of a high-yield catalyst for synthetization of aromatics from syngas.

Effects of Solid-State Reaction Synthesis Processing Parameters on Thermoelectric Properties of Mg_2Si

The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of the material,and also studies effects of doping elemental Sb,Te and their doping seqence on the properties of the material.The result shows that excessively high temperature and elongated holding time of solid-state reaction are harmful,there is a range of particle size to ensure optimum properties and the doping sequence of Sb or Te without influencing the properties.

Preparation of β-Sialon/ZrN bonded corundum composites from zircon by nitridation reaction sintering process

β-Sialon/ZrN bonded corundum composites were synthesized using fused white corundum,alumina micro powder,zircon and carbon black by nitridation reaction sintering process. Phase composition and microstructure of the synthesized composites were investigated by X-ray powder diffraction and scanning electronic microscope,and the formation process of the composites was discussed. The results show that the composites with different compositions can be obtained by controlling the heating temperature and contents of zircon and carbon black. The proper temperature to synthesize the composites is 1773 K.

Empirical correction of kinetic model for polymer thermal reaction process based on first order reaction kinetics

Based on the theory of first-order reaction kinetics,a thermal reaction kinetic model in integral form has been derive.To make the model more applicable,the effects of time and the conversion degree on the reaction rate parameters were considered.Two types of undetermined functions were used to compensate for the intrinsic variation of the reaction rate,and two types of correction methods are provided.The model was explained and verified using published experimental data of different polymer thermal reaction systems,and its effectiveness and wide adaptability were confirmed.For the given kinetic model,only one parameter needs to be determined.The proposed empirical model is expected to be used in the numerical simulation of polymer thermal reaction process.

Modeling and Optimization of Ethane Steam Cracking Process in An Industrial Tubular Reactor with Improved Reaction Scheme

Ethane steam cracking process in an industrial reactor was investigated.An one-demsional(1D)steady-state model was developed firstly by using an improved molecular reaction scheme and was then simulated in Aspen Plus.A comparison of model results with industrial data and previously reported results showed that the model can predict the process kinetics more accurately.In addition,the validated model was used to study the effects of different process variables,including coil outlet temperature(COT),steam-to-ethane ratio and residence time on ethane conversion,ethylene selectivity,products yields,and coking rate.Finally,steady-state optimization was conducted to the operation of industrial reactor.The COT and steam-to-ethane ratio were taken as decision variables to maximize the annual operational profit.

EFFECT OF STRESS-INDUCED REACTIONS ON MORPHOLOGICAL STRUCTURE AND PROCESSABILITY OF PVC DURING PAN-MILLING

The effect of pan-milling on morphological structure,processability and properties of PVC was studied throughSEM,FTIR,granulometer,GPC and mechanical properties test in the hope of gaining ease in operation,needless ofplasticizers,a clean and efficient route for improving the processability of PVC through stress-induced reactions,fulfilling the idea of“plasticizing PVC by itself”.The experimental results show that during pan-milling at ambienttemperature,within 2-3 min,the microcrystalline structure of PVC becomes indistinct,the grain size of PVC is reducedfrom 130-160 μm to 1-50 μm the molecular weight of PVC is slightly decreased,the variation of molecular weightdistribution is indistinct,the plasticizing time and torque at balance drop a great deal from 71-132 s to 31-33 s and from18.2-22.1 Nm to 14.7-18.4 Nm,respectively,the processability of PVC is markedly improved,and the mechanicalproperties get enhanced too.

DBU-based CO2 absorption-mineralization system: Reaction process,feasibility and process intensification

Amine-based carbon dioxide(CO2)capture is still limited by high desorption energy consumption.Fixing CO2 into carbonate is a safer and more permanent method.In this work,calcium oxide(CaO)is introduced to perform chemical desorption instead of thermal desorption on 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU)aqueous solution after CO2 absorption.The X-ray diffraction(XRD)patterns of solid products show the formation of calcite calcium carbonate(CaCO3),which prove the feasibility of this method.The effects of reaction temperature,reaction time and Ca2+/CO32-molar ratios on the related reactions in CO2 absorption-mineralization process and CaCO3 precipitation are discussed,and purer CaCO3 is obtained by ultrasonic treatment.The CaCO3 content can be increased to 95.8%and the CO2 desorption ratio can achieve 80%by 30 min ultrasonic dispersion treatment under the conditions(40℃,180 min,Ca2+/CO32-molar ratio=1.0).After five cycles,DBU aqueous solution shows stable CO2 absorption and mineralization ability.Fourier transform infrared spectroscopy(FT-IR)spectra of the reaction process also indicate the regeneration of the solvent.Compared with thermal desorption,this process is exothermic,almost without no additional heat.

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.

Estimation on Global Reaction Heat for the Aromatization Process of Liquefied Petroleum Gas

The reaction heat effect analysis for the aromatization process of Liquefied Petroleum Gas (LPG) was completed in this paper. In order to characterize this complex reaction system, one set of independent reactions was determined by means of atomic coefficient matrix method. Based on reaction thermodynamic and stoichiometric knowledge, the heat effect, Gibbs free energy change and equilibrium constant for each independent reaction was calculated for the specified conditions. Under these conditions, based on the initial and final composition data from LPG aromatization experiments, the actual extent of reaction for each independent reaction was determined. Furthermore, the global reaction heat and adiabatic temperature rise of LPG aromatization reaction system could be estimated. This work would provide a theoretical guidance for the design and scale-up of reactor for LPG aromatization process, as well as for the selection of proper operating conditions.

Study on the mechanism of coal liquefaction reaction and a new process concept

The coal hydrogenation reaction process is simply considered as three steps.In the first step,the smaller molecules associated with coal structure units are released as some gases and water in the condition of solvent and heating.In this step,some weaker bonds of the coal structure units are ruptured to form free radicals.The radicals are stabi- lized by hydrogen atoms from donor solvent and/or H2.In the second step,chain reaction occurs quickly.In the process of chain reaction,the covalent bonds of coal structure units are attacked by the radicals to form some asphaltenes.In the third step,asphaltenes are hydrogenated form more liquids and some gases.In coal liquefaction,the second step of coal hydrogenation reaction should be controlled to avoid integration of radicals,and the third step of coal hydrogenation should be accelerated to increase the coal conversion and the oil yield.A new concept of coal liquefaction process named as China direct coal lique- faction (CDCL) process is presented based on the mechanism study of coal liquefaction.

Process intensification in gas/liquid/solid reaction in trickle bed reactors: A review

As an important form of reactors for gas/liquid/solid catalytic reaction,trickle bed reactors (TBRs) are widely applied in petroleum industry,biochemical,fine chemical and pharmaceutical industries because of their flexibility,simplicity of operation and high throughput.However,TBRs also show inefficient production and hot pots caused by non-uniform fluid distribution and incomplete wetting of the catalyst,which limit their further application in chemical industry.Also,process intensification in TBRs is necessary as the decrease in quality of processed crude oil,caused by increased exploitation depths,and more restrictive environmental regulations and emission standards for industry,caused by increased environment protection consciousness.In recent years,lots of strategies for process intensification in TBRs have been proposed to improve reaction performance to meet the current and future demands of chemical industry from the environmental and economic perspective.This article summarizes the recent progress in techniques for intensifying gas/liquid/solid reaction in TBRs and application of intensified TBRs in petroleum industry.

Metallurgical Reaction Characteristic for the Combined Blowing Process of Top-Bottom Blown Oxygen and Bottom Blown Natural Gas

The experiment was carried out in a combined blowing converter.The natural gas was supplied as the cooling medium for the bottom lance.The blow- ing practice of medium P hot metal (0.30-0.85% [P]) indicated that with better stirring at the bottom of the converter and lower P_(CO),this steelmgking process was favorable to reduce the amount of [C] and [O] and increase the (P_2O_5)/[P]. The maximum rate of dephospborization might be high up to 0.0a5%/min and the P content in steel could be reduced to lower than 0.03% by single slag-forming operation.

Adjusting oxygen vacancies in perovskite LaCoO_(3)by electrochemical activation to enhance the hydrogen evolution reaction activity in alkaline condition

Developing highly-active,earth-abundant non-precious-metal catalysts for hydrogen evolution reaction(HER)in alkaline solution would be beneficial to sustainable energy storage.Perovskite oxides are generally regarded as low-active HER catalysts,due to their inapposite hydrogen adsorption and water dissociation.Here,we report a detailed study on perovskite LaCoO_(3)epitaxial thin films as a model catalyst to significantly enhance the HER performance via an electrochemical activation process.As a result,the overpotential for the activation films to achieve a current density of 0.36 m A/cm^(2)is 238 m V,reduced by more than 200 m V in comparison with that of original samples.Structural characterization revealed the activation process dramatically increases the concentration of oxygen vacancies(Vo)on the surface of LaCoO_(3).We established the relationship between the electronic structure induced by Vo and the enhanced HER activity.Further theoretical calculations revealed that the Vo optimizes the hydrogen adsorption and dissociation of water on the surface of LaCoO_(3)thin films,thus improving the HER catalytic activity.This work may promote a deepened understanding of perovskite oxides for HER mechanism by Vo adjusting and a new avenue for designing highly active electrochemical catalysts in alkaline solution.

Activation of Transition Metal(Fe,Co and Ni)-Oxide Nanoclusters by Nitrogen Defects in Carbon Nanotube for Selective CO_(2) Reduction Reaction

The electrochemical carbon dioxide reduction reaction(CO_(2)RR),which can produce value-added chemical feedstocks,is a proton-coupled-electron process with sluggish kinetics.Thus,highly efficient,cheap catalysts are urgently required.Transition metal oxides such as CoO_(x),FeO_(x),and NiO_(x)are low-cost,low toxicity,and abundant materials for a wide range of electrochemical reactions,but are almost inert for CO_(2)RR.Here,we report for the first time that nitrogen doped carbon nanotubes(N-CNT)have a surprising activation effect on the activity and selectivity of transition metal-oxide(MO_(x)where M=Fe,Ni,and Co)nanoclusters for CO_(2)RR.MO_(x)supported on N-CNT,MO_(x)/N-CNT,achieves a CO yield of 2.6–2.8 mmol cm−2 min−1 at an overpotential of−0.55 V,which is two orders of magnitude higher than MO_(x)supported on acid treated CNTs(MO_(x)/O-CNT)and four times higher than pristine N-CNT.The faraday efficiency for electrochemical CO_(2)-to-CO conversion is as high as 90.3%at overpotential of 0.44 V.Both in-situ XAS measurements and DFT calculations disclose that MO_(x)nanoclusters can be hydrated in CO_(2)saturated KHCO_(3),and the N defects of N-CNT effectively stabilize these metal hydroxyl species under carbon dioxide reduction reaction conditions,which can split the water molecules and provide local protons to inhibit the poisoning of active sites under carbon dioxide reduction reaction conditions.

Computer Data Processing of the Hydrogen Peroxide Decomposition Reaction

Two methods of computer data processing, linear fitting and nonlinear fitting, are applied to compute the rate constant for hydrogen peroxide decomposition reaction. The results indicate that not only the new methods work with no necessity to measure the final oxygen volume, but also the fitting errors decrease evidently.

Continuous,efficient and safe synthesis of 1-oxa-2-azaspiro[2.5]octane in a microreaction system

1-Oxa-2-azaspiro[2.5]octane,as one of N-H oxaziridines,is a selective electrophilic aminating agent for N-,S-,C-,and O-nucleophiles.It has the features of stereoselectivity and the absence of formation of strongly acidic or basic byproducts,leading to considerable interest in the development of organic synthetic methods.Currently,the economically feasible route of production of 1-oxa-2-azaspiro[2.5]octane is the reaction of cyclohexanone with ammonia and sodium hypochlorite.However,due to strong exothermic reactions,massive gas release and heterogeneous reaction,the controllability,efficiency and safety of the reaction are in great difficulty using batch technology.In this paper,a microreaction system containing predispersion,reaction and phase separation was introduced into the preparation of 1-oxa-2-azaspiro[2.5]octane.The research results showed that precise control of the process including droplet dispersion,temperature control,reaction time control and fast continuous phase separation,was the key to process intensification.Under optimal conditions,the concentration of 1-oxa-2-azaspiro[2.5]octane in product obtained by microreaciton system(~2.0 mol·L^(-1))was much higher than that obtained by batch technology(0.2-0.4 mol·L^(-1)),which demonstrated that the continuous-flow synthesis would be a more efficient substitute for batch synthesis.Meanwhile,the results of the derivation experiments also showed that the aminating agent solution with higher concentration was more advantageous in the applications.