Complete kinetic model for esterification reaction of lauric acid with glycerol to synthesize glycerol monolaurate

Glycerol monolaurate(GML)is a widely used industrial chemical with excellent emulsification and antibacterial effect.The direct esterification of glycerol with lauric acid is the main method to synthesize GML.In this work,the kinetic process of direct esterification was systematically studied using p-toluenesulfonic acid as catalyst.A complete kinetic model of consecutive esterification reaction has been established,and the kinetic equation of acid catalysis was deduced.The isomerization reactions of GML and glycerol dilaurate were investigated.It was found that the reaction was an equilibrium reaction and the reaction rate was faster than the esterification reaction.The kinetic equations of the consecutive esterification reaction were obtained by experiments as k_(1)=(276+92261Xcat)exp(-37720/RT)and k_(2)=(80+4413Xcat)exp(-32240/RT).The kinetic results are beneficial to the optimization of operating conditions and reactor design in GML production process.

Experimental investigation of the mixing efficiency via intensity of segregation along axial direction of a rotating bar reactor

As a significant index to evaluate the mixing efficiency,studying the concentration distribution is directly related to the intensity of segregation(I_(s)).In this work,the I_(s) of the mixture composed of NaCl solutionwater was investigated experimentally in a rotating bar reactor(RBR)by the conductivity method.The results showed that the mixing efficiency was improved along the axial direction from the bottom to the top in the RBR.The concentration distribution at the bottom section was more uneven,and I_(s) was higher compared with the top section,which decreased from 6.53×10^(-5)to 1.57×10^(-7).With the increase of rotational speed from 0 to 700 r·min^(-1),I_s at the bottom and top sections decreased from 4.27×10^(-3)to 7.10×10^(-5)and from 1.93×10^(-3)to 7.29×10^(-7),respectively.The increases flow rate of solution A,and the decreases of concentration of NaCl and flow rate of solution B gave rise to the reduction of I_(s),signifying an improved mixing efficiency.The results revealed that the conductivity method used in this paper has high efficiency and low cost to measure the I_(s),which indicates a promising prospect for estimating reactors'mixing performance.

新冠病毒肺炎疫情期间口罩能否经热水泡灭毒后重复使用?

新冠病毒肺炎疫情期间,口罩成为不可或缺的防控利器和战略物资。如何科学、安全、有效地重复使用口罩,让每一只口罩发挥最大效能,数倍甚至十倍以上地提高防护口罩的有效使用时间,是疫情防控所急需解决的关键科技问题。我们提出了“口罩荷电再生重复使用”的技术方法,并开展了再生口罩性能评价。首先将使用后的口罩浸泡在56℃以上热水中30min进行消毒处理,随后采用普通家用电吹风机等对“失效”的口罩进行吹干荷电处理,使口罩可重新荷电而再生静电效应。对市售的三类典型口罩(一次性医用口罩、医用外科口罩、KN95级防护口罩)进行“热水泡灭毒+荷电再生”处理,实验证明其过滤层微观结构和口罩抗渗水性均无明显变化,再生口罩对非油性颗粒物的过滤效率满足相关口罩指标要求。相关研究结果为新冠病毒肺炎疫情期间的口罩荷电再生重复使用提供了参考。进一步研究了真人佩戴过程对不同初始性能的口罩的性能演变。浙江闰土股份有限公司在2月20日至3月30日期间应用“口罩荷电再生重复使用技术”,将原先每个员工每日发放一个一次性医用口罩,改为每个员工每三日发放一个一次性医用口罩,节约口罩12.25万只,降低了公司的口罩使用量,也确保了防疫工作的正常开展。本文基于真实佩戴口罩的研究,建立了基于荧光纳米颗粒渗透探伤的口罩检测新方法,为可重复使用口罩材料设计、结构优化和性能综合评价提供参考。

Computational fluid dynamic simulation of gas-liquid flow in rotating packed bed:A review

The rotating packed bed(RPB)has been widely used in gas-liquid flow systems as a process intensification device,exhibiting excellent mass transfer enhancement characteristics.However,the complex internal structure and the high-speed rotation of the rotor in RPB bring significant challenges to study the intensification mechanism by experiment methods.In the past two decades,Computational fluid dynamics(CFD)has been gradually applied to simulate the hydrodynamics and mass transfer characteristics in RPB and instruct the reactor design.This article covers the development of the CFD simulation of gasliquid flow in RPB.Firstly,the improvement of the simulation method in the aspect of mathematical models,geometric models,and solving methods is introduced.Secondly,new progress of CFD simulation about hydrodynamic and mass transfer characteristics in RPB is reviewed,including pressure drop,velocity distribution,flow pattern,and concentration distribution,etc.Some new phenomena such as the end effect area with the maximum turbulent have been revealed by this works.In addition,the exploration of developing new reactor structures by CFD simulation is introduced and it is proved that such new structures are competitive to different applications.The defects of current research and future development directions are also discussed at last.

Preparation of Pd/c-Al_(2)O_(3)/nickel foam monolithic catalyst and its performance for selective hydrogenation in a rotating packed bed reactor

Selective hydrogenation plays an important role in chemical industries,yet its selectivity is usually limited by the mass transfer.In this work,the enhanced hydrogenation selectivity was achieved in a rotating packed bed(RPB)reactor with excellent mass transfer efficiency.Aiming to be used under the centrifugal filed,a monolithic catalyst Pd/c-Al_(2)O_(3)/nickel foam suiting for the shape and size of the rotor of RPB reactor was prepared by the electrophoretic deposition method.The mechanical strength of the catalyst can meet the requirement of high centrifugal force in the RPB.The hydrogenation selectivity in the RPB reactor using the 3-methyl-1-pentyn-3-ol hydrogenation system was 3–8 times higher than that in a stirred tank reactor under similar conditions.This work proves the feasibility of intensifying the selectivity of hydrogenation process in the RPB reactor.

An Evaluation of Metronidazole Degradation in a Plasma-Assisted Rotating Disk Reactor Coupled with TiO2 in Aqueous Solution

Pollution involving pharmaceutical components in bodies of water is an increasingly serious environmental issue.Plasma discharge for the degradation of antibiotics is an emerging technology that may be relevant toward addressing this issue.In this work,a plasma-assisted rotating disk reactor(plasma-RDR)and a photocatalyst—namely,titanium dioxide(TiO_(2))—were coupled for the treatment of metronidazole(MNZ).Discharge uniformity was improved by the use of a rotating electrode in the plasma-RDR,which contributed to the utilization of ultraviolet(UV)light radiation in the presence of TiO_(2).The experimental results showed that the degradation efficiency of MNZ and the concentration of generated hydroxyl radicals respectively increased by 41%and 2.954 mg∙L^(-1) as the rotational speed increased from 0 to 500 r∙min^(-1).The synergistic effect of plasma-RDR plus TiO_(2) on the generation of hydroxyl radicals was evaluated.Major intermediate products were identified using three-dimensional(3D)excitation emission fluorescence matrices(EEFMs)and liquid chromatography-mass spectrometry(LC-MS),and a possible degradation pathway is proposed herein.This plasma-catalytic process has bright prospects in the field of antibiotics degradation.

Controllable and high-throughput preparation of microdroplet using an ultra-high speed rotating packed bed

Microdroplets and their dispersion,with a large specific surface area and a short diffusion distance,have been applied in various unit operations and reaction processes.However,it is still a challenge to control the size and size distribution of microdroplets,especially for high-throughput generation.In this work,a novel ultra-high speed rotating packed bed(UHS-RPB)was invented,in which rotating foam packing with a speed of 4000-12000 r·min^(-1) provides microfluidic channels to disperse liquid into microdroplets with high throughput.Then generated microdroplets can be directly dispersed into a continuous falling film for obtaining a mixture of microdroplet dispersion.In this UHS-RPB,the effects of rotational speed,liquid initial velocity,liquid viscosity,liquid surface tension and packing pore size on the average size(d_(32))and size distribution of microdroplets were systematically investigated.Results showed that the UHS-RPB could produce microdroplets with a d_(32) of 25-63μm at a liquid flow rate of 1025 L·h^(-1),and the size distribution of the microdroplets accords well with Rosin-Rammler distribution model.In addi-tion,a correlation was established for the prediction of d_(32),and the predicted d_(32) was in good agreement with the experimental data with a deviation within±15%.These results demonstrated that UHS-RPB could be a promising candidate for controllable preparation of uniform microdroplets.

Chemical probe systems for assessing liquid–liquid mixing efficiencies of reactors

Liquid-liquid mixing,including homogeneous and heterogeneous mixing,widely exists in the chemical industry.How to quantitatively characterize the mixing performance is important for reactor assessment and development.As a convenient and direct method for mixing characterization,the chemical probe method uses some special test reactions to characterize the mixing results.Here,the working principle and selection requirements of this method are introduced,and some common chemical probe systems for homogeneous and heterogeneous mixing processes are reviewed.The characteristics and applications of these systems are illustrated.Finally,the development of the new system is proposed.

Numerical studies of dynamic behavior of liquid film on single-layer wire mesh with different wettabilities

Droplet impacting on the stainless steel wire mesh is very common in chemical devices,like a rotating packed bed.Surface wettability of wire mesh significantly affects the liquid flow pattern and liquid dispersion performance.However,the effect of surface wettability on the impaction phenomena at microscale such as liquid film is still unknown.In this work,the dynamic behavior of liquid film on the surface of wire mesh was analyzed by computational fluid dynamics simulation.The dynamic behavior of liquid film on the surface of wire mesh can be divided into the following three steps:(1)spreading step;(2)shrinkage process;(3)stabilizing or disappearing step.Effects of surface wettability,as well as operating conditions,on wetting area and liquid film thickness were studied.Compared to the hydrophilic wire mesh,the final wetting area of hydrophobic wire mesh is zero in most cases.The average liquid film thickness on the surface of hydrophilic wire mesh is 30.02–77.29μm,and that of hydrophobic wire mesh is 41.76–237.37μm.This work provided a basic understanding of liquid film flow at microscale on the surface with various surface wettabilities,which can be guiding the packing optimization and design.

NO_(x) removal by non-thermal plasma reduction:experimental and theoretical investigations

Green and efficient NO_(x)removal at low temperature is still desired.NO_(x)removal via non-thermal plasma(NTP)reduction is one of such technique.This work presents the experimental and theoretical study on the NO_(x)removal via NTP reduction(NTPRD)in dielectric barrier discharge reactor(DBD).The effect of O_(2)molar fraction on NO_(x)species in the outlet of DBD,and effects of NH_(3)/NO_(x)molar ratio and discharge power of DBD on NO_(x)removal efficiency are investigated.Results indicate that anaerobic condition and higher discharge power is beneficial to direct removal of NO_(x),and the NO_(x),removal efficiency can be up to 98.5%under the optimal operating conditions.It is also found that adding NH_(3)is favorable for the reduction of NO_(x),to N_(2)at lower discharge power.In addition,the NO_(x)removal mechanism and energy consumption analysis for the NTPRD process are also studied.It is found that the reduced active species(N^(+),N^(-),N^(+),N_(2)^(*),NH_(2)^(+),etc.)generated in the NTPRD process play important roles for the reduction of NO_(x),to N_(2).Our work paves a novel pathway for NO_(x)removal from anaerobic gas in industrial application.