Liquid-phase esterification of methacrylic acid with methanol catalyzed by cation-exchange resin in a fixed bed reactor:Experimental and kinetic studies

The kinetic behavior of esterification between methacrylic acid and methanol catalyzed by NKC-9 resin was studied in a fixed bed reactor.The reaction was conducted in the temperature range of 323.15 to 368.15 K with the molar ratio of reactants from 0.8 to 1.4 under certain pressure.The measurement data were regression with the pseudo-homogeneous(P-H),Eley-Rideal(E-R),and Langmuir-Hinshelwood(L-H)heterogeneous kinetic models.Independent adsorption experiments were implemented to gain the adsorption equilibrium constants of four components.Among the above three models,the L-H model exhibited the best fitting results.The stability of NKC-9 was evaluated by long-term running with the yield of methyl methacrylate no decrease during 3000 h operation.The structure and physicochemical properties of the new and used catalyst were performed by several characterizations including thermogravimetric analysis(TG),scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)and so on.

In-situ generated ionic liquid catalyzed aldol condensation of trioxane with ester in mild homogeneous system

α, β-unsaturated esters were often synthesized from aldehydes and esters in the presence of strong organic base that was very sensitive to air and moisture via aldol reaction. Trioxane was very useful C1 resource, however, the decomposition of it was always the challenging problem that facing researchers. Herein, a novel synthetic methodology for α, β-unsaturated ester preparation from trioxane and ester with mild catalysis of generated ammonium trifluoromethanesulfonate ionic liquid. The enolization of ester as well as the decomposition of trioxane could proceed easily in the presence of boryl trifluoromethanesulfonate and amine at 20–25℃. Then the enolate and decomposed formaldehyde occurs aldol reaction to form α, β-unsaturated ester. With this strategy, the yield and selectivity of product from various substrates including aliphatic esters,lactones and thioester could reach up to 85.2% and 90.1%.

Process design and economic analysis of methacrylic acid extraction for three organic solvents

In this work,a techno-economic study for the solvent based extraction of methacrylic acid from an aqueous solution is presented.The involved phase equilibrium calculations in process design are verified by measured experimental data.First,experiments are conducted with different solvent candidates to measure LLE(liquid–liquid equilibrium)data and to establish the effects of extraction temperature and dosage of solvent.Next,the binary interaction parameters for the UNIQUAC model to be used for equilibrium calculations are fine-tuned with measured data.Then,a process for the solvent based extraction of methacrylic acid recovery is designed and verified through simulation with the regressed UNIQUAC model parameters.The optimal configuration of the process flowsheet is determined by minimizing the total annualized cost.Among the three solvent candidates considered-cyclohexane,hexane and toluene-the highest efficiency and the lowest total annualized cost is found with toluene as the solvent.

Ionic liquid catalyzed solvent-free synthesis of chalcone and its derivatives under mild conditions

An ionic liquid(IL)catalyzed solvent-free process was developed for the direct synthesis of chalcone and its derivatives by using substituted acetophenones and benzaldehydes via aldol reaction under mild conditions.A series of acidic and basic ILs were selected and screened.The influences of cations and reaction conditions on product yield and selectivity were systematically investigated.The[Bmim]OH was identified as the optimal IL,with the highest yield and selectivity reaching up to 96.7% and 100%,respectively.A reaction mechanism-based kinetic model was established and regressed with experimental data,revealing the β-Hydroxylketone dehydrolysis with activation barrier of 37.8 kJ·mol^(-1) was observed as the ratecontrolling step.

MOOC/SPOC Blended Teaching Practice on Software Engineering Using“Integration of Physical Classroom,Online Classroom and Practical Classroom”

With the vigorous development of MOOC and SPOC,software engineering teachers are exploring how to use first-class online resources to reconstruct the software engineering teaching system.This study proposed a project-driven group discussion classroom teaching reform,which is characterized by“the trinity integration of physical classroom,online classroom,and practical classroom”.The reform employs heuristic and case-based teaching methods,in which,the curriculum is supplemented by smart teaching tools and takes discussion teaching as the core.The teaching process emphasizes the accumulation of multi-stage study results and adopts smart teaching method innovation.In this study,we also build practical classrooms with top software companies.We encourage students to participate in the classroom and take the initiative to practice through“discussion groups”“enterprise practice”,and“cloud training”,which improves learning effectiveness and enhances the ability to analyze problems,design systems,and innovate in actual software projects.

Modification to solution-diffusion model for performance prediction of nanofiltration of long-alkyl-chain ionic liquids aqueous solutions based on ion cluster

Mathematical modeling for nanofiltration of ionic liquids(ILs) solutions could assist to understand transfer mechanism and predict experimental values. In this work, modeling by solution-diffusion model for nanofiltration of long-alkyl-chain ILs aqueous solutions was proposed. Molecular simulations were performed to validate the existence of ion cluster in long-alkyl-chain ILs aqueous solution. Based on the results of simulations, parameters used in the solution-diffusion model were modified, such as concentration of ILs and diameter of ion cluster.The modeling process was developed for three long-alkyl-chain ILs aqueous solutions with different concentrations(1-alkyl-3-methylimidazolium chloride: [C6 mim]Cl, [C8 mim]Cl, [C10 mim]Cl). The calculated values obtained from modified solution-diffusion model could well match the experimental values.

Research on Online and Offline Hybrid Teaching Mode under the Concept of OBE ——A Case Study for Software Engineering

With the support of the Ministry of Education’s Industry-Academia Collaborative Education Project and the critical project of Shandong Province’s education and teaching reform,we explore student-centered education reform positively to learn outcome-driven,which have the characteristics of a solid foundation,intense practice,strict process,and innovation.Under the technical support of the“Internet+”smart education,our practice has formed an online and offline hybrid teaching mode based on the effective interaction of teaching total factor under the OBE concept.Based on Bloom’s Taxonomy and Outcomes-based Education(OBE),this model formulates the overall objectives of the curriculum and the detailed objectives of each teaching step,plans the online and offline teaching design as a whole,and implements the target teaching by classification.Based on Laurillard’s scientific model of designing teaching sessions,we continuously iterate over the teaching steps like teacher communication,teacher demonstration,peer communication,and peer demonstration following the agile education concept.In the meantime,comprehensive application of SPOC online platform,Mu classroom,smart classroom offline carrier,WeChat/QQ social software,and other technical means facilitates the design for student-student interaction,teacher-student interaction,student-student discussion,teacher-student discussion,and other scenarios,realizing the combination of online and offline environment,of study independently and in the group,of flipped classroom and seminars.

Silver modified Cu/SiO2 catalyst for the hydrogenation of methyl acetate to ethanol

A series of silver modified Cu/SiO2 catalysts were synthesized with ammonia-evaporation method and applied in vapor-phase hydrogenation of methyl acetate to ethanol.The influence of additive‘Ag’on the structural evolution of catalyst was systematically studied by several characterization techniques,such as N2 adsorption–desorption,N2O titration,PXRD,FTIR,in-situ FTIR,H2-TPR,H2-TPD,XPS and TEM.Results showed that incorporation of a small amount of Ag could enhance the structural stability,and the strong interaction between Cu and Ag species was conducive to increase the dispersion of copper species and create a suitable Cu+/(Cu0+Cu+)ratio,which was proposed to be responsible for the improved catalytic activity.The maximum conversion of MA(94.1%)and selectivity of ethanol(91.3%)over optimized Cu-0.5 Ag/SiO2 and 120 h on stream without deactivation under optimal conditions demonstrates its excellent stability.

A simple strategy to synthesize and characterization of zirconium modified PCs/γ–Al_2O_3

Crystalline phase is the key factor for catalyst activity. The zirconium modified PCs/γ-Al_2O_3 samples were prepared through a simple step incipient-wetness impregnation method. The raw materials and samples were characterized by thermogravimetric-differential analysis(TG-DTA), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), temperature-programmed desorption of ammonia and carbon dioxide(NH_3-and CO_2-TPD). The effects of calcination temperature and zirconium content on structure, chemical transformation,and acidity-basicity were investigated. Calcination temperature exhibited the major effect on the crystalline phase of samples. The new phase of Al0.1Zr_(0.9)O_(1.95) was exhibited which was above 650 ℃. In addition, zirconium content was influenced by the acidic and basic properties of the surface. The acidity and basicity of the Zr PCs/γ-Al_2O_3 sample increased with the increasing of zirconium content.

Research on Blended Teaching Based on“MOOC+SPOC+multimodal classroom”

Combined with China’s educational reality and the vigorous development of MOOC and SPOC,this paper discusses the connotation and mode of blended teaching based on“MOOC+SPOC+multimodal classroom”,and puts forward that blended teaching is the deep integration of“teaching”as the center and“learning”as the center.The classroom form of blended teaching is various and rich,which is defined as multimodal classroom,and the common forms of multimodal classroom are given.This paper summarizes the specific problems encountered in the implementation of blended teaching,and gives the solutions.Based on Bloom’s cognitive model and Dewey’s“learning by doing”theory,the scheme takes cumulative assessment as the starting point,makes full use of intelligent teaching tools such as rain classroom and mobile cloud classroom,and pays more attention to the agility of teaching and the coordination inside and outside the classroom.Through practice,the teaching efficiency and effect are improved obviously.

Sulfur production from smelter off-gas using CO–H2 gas mixture as the reducing agent over modified Fe/γ-Al2O3 catalysts

A series of modifiedγ-Al_2O_3supported iron-based catalysts(M-Fe/γ-Al_2O_3)was developed to reduce SO_2in actual smelter off-gases using CO–H_2gas mixture as reducing agent for sulfur production.Used as modifiers,three metal additives—Ni,Co,and Ce were added to Fe/γ-Al_2O_3catalysts.Changes in catalyst structure and active phase were characterized with X-ray diffraction,XPS,SEM,and EDS.The reduction ability of catalysts was exhibited via CO-TPR.The prepared catalysts only need to be pre-reacted for a period of time,eliminating the need for presulfidation treatment.Reaction conditions were optimized in a fixed bed reactor to achieve high SO_2conversion and sulfur selectivity.XRD characterization was carried out to verify the resulting sulfur products.Combining in situ infrared characterization and catalyst evaluation of support and active component,the reaction mechanism was investigated and proposed.

Cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3)in Al_(2)O_(3)-AlPO_(4)for aldol condensation of methyl acetate with formaldehyde to methyl acrylate

The bare amorphous Al_(2)O_(3)-AlPO_(4)and Cs/Al_(2)O_(3)-AlPO_(4)catalysts were developed for the aldol condensation of methyl acetate with formaldehyde to methyl acrylate.The structure and property of catalyst were characterized by XRD,XPS,BET,Pyridine-IR,FT-IR,^(27)Al-MASNMR,NH_(3)-/CO_(2)-TPD and SEM.The correlation between structural features and acid-base properties was established,and the loading effect of the cesium species was investigated.Due to cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3),the weak-Ⅱacid and medium acid site densities and the product selectivity were improved.While the basic site densities of these catalysts were almost in proportion to the conversion of methyl acetate.The loaded Cs could form new basic sites and change the distribution of acid sites which further enhance the catalytic performance.As a result,the 10Cs/8AlP was proved to be an optimal catalyst with the yield and selectivity of 21.2%and 85%for methyl acrylate respectively.During the reaction,a deactivation behavior was observed on 10Cs/8AlP catalyst due to the carbon deposition,however,it could be regenerated by thermal treatment in the air atmosphere at 400℃.

ANTIOXIDANT DEPLETION AND OIT VALUES OF HIGH IMPACT PP STRANDS

The service life of a polyolefin product depends to large extent on the type and amount of the antioxidants added. During the manufacturing,storage and use of the product the antioxidants are depleted by physical processes and chemical degradation,and this impairs its long-term performance.The initial and in-use oxidation stability is often characterized and monitored by the measurement of the oxidative induction time(OIT),and service life predictions are based on the rate of decrease of the OIT value.To study the correlation between the OIT value and the actual antioxidant concentration,eight random arrays of high-impact polypropylene(PP)strands stabilized using six different antioxidant packages(composed of Irgafos 168,Irganox 1010 and 1330,Chimassorb 944)were immersed in hot water(80℃and 90℃)and oven aged in air (80℃)for more than two years,and the change of OIT values and antioxidant concentrations was measured.For phosphitic and phenolic stabilizers water immersion is generally a more critical aging condition than oven aging in air,while for the hindered amine stabilizers(HAS)the opposite was observed.As expected,a linear correlation between OIT values and concentrations was found for the'classical'package of phosphitic and phenolic stabilizers.In the case of Irganox 1330,the change of the OIT values during aging was considerably slower than the change of concentration.Even when zero concentration was reached according to the vanishing peak height in the chromatogram,a considerable OIT value was still measurable.This may be due to unidentified degradation products of Irganox 1330 which still act as antioxidants in the long run.Addition of HAS(Chimassorb 944)seems to enhance the initial OIT of stabilized phenolic samples and the long-term effectiveness of the phenolic stabilization under air oven aging conditions.However,the marked long-term effectiveness of the HAS itself and the slow change with time of the concentration were not detectable by OIT measurements above the PP melting point of about 170℃.

A novel synthetic method of porous and nanoflower-like Al_(2)O_(3)/MoS_(2)catalyst for reduction of SO_(2)to elemental sulfur

MoS_(2)nanoflowers are favored for their potential in the production of elemental sulfur due to abundant surface area and good catalytic performance for reducing SO_(2).A novel synthetic strategy of porous Al_(2)O_(3)supported on the MoS_(2)with nanoflower structure was proposed.The effects of preparation concentration,calcination atmosphere,Al_(2)O_(3)contents on the growth of catalysts with nanoflower structure were systematically studied via X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM),Fourier transform infrared(FTIR)spectroscopy,Brunauer–Emmett–Teller(BET).The surface area was increased to 295.502 m^(2)/g and the amount of Lewis acid on the surface of the Al_(2)O_(3)/MoS_(2)catalyst was increased by adjusting the ratio of Al/Mo.The porous and nanoflower structures of Al_(2)O_(3)/MoS_(2)catalysts promoted the sulfur selectivity without inhibiting the catalytic performance of MoS_(2).The conversion of SO_(2)and the selectivity of sulfur were 100%and 92%after 100 h life evaluation.

二氧化硅表面疏水改性研究

以合成二氧化硅为原料,采用硅烷偶联剂对其进行表面改性处理。结果表明:硅烷偶联剂与二氧化硅表面羟基发生反应,当使用量达到16%,改性处理时间达到4小时,使二氧化硅具有良好的疏水性能。

Molecular level understanding of CO_(2) capture in ionic liquid/polyimide composite membrane

Ionic liquid(IL)/polyimide(PI)composite membranes demonstrate promise for use in CO_(2)separation applications.However,few studies have focused on the microscopic mechanism of CO_(2)in these composite systems,which is important information for designing new membranes.In this work,a series of systems of CO_(2)in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide composited with 4,4-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)-based PI,6FDA-2,3,5,6-tetramethyl-1,4-phenylene-diamine,at different IL concentrations were investigated by all-atom molecular dynamics simulation.The formation of IL regions in PI was found,and the IL regions gradually became continuous channels with increasing IL concentrations.The analysis of the radial distribution functions and hydrogen bond numbers demonstrated that PI had a stronger interaction with cations than anions.However,the hydrogen bonds among PI chains were destroyed by the addition of IL,which was favorable for transporting CO_(2).Furthermore,the self-diffusion coefficient and free energy barrier suggested that the diffusion coefficient of CO_(2)decreased with increasing IL concentrations up to 35 wt-%due to the decrease of the fractional free volume of the composite membrane.However,the CO_(2)selfdiffusion coefficients increased when the IL contents were higher than 35 wt-%,which was attributed to the formation of continuous IL domain that benefitted the transportation of CO_(2).

Modeling of fixed bed reactor for coal tar hydrogenation via the kinetic lumping approach

Hydrogenation technology is an indispensable chemical upgrading process for converting the heavy feedstock into favorable lighter products.In this work,a new kinetic model containing four hydrocarbon lumps(feedstock,diesel,gasoline,cracking gas)was developed to describe the coal tar hydrogenation process,the Levenberg–Marquardt’s optimization algorithm was used to determine the kinetic parameters by minimizing the sum of square errors between experimental and calculated data,the predictions from model validation showed a good agreement with experimental values.Subsequently,an adiabatic reactor model based on proposed lumped kinetic model was constructed to further investigate the performance of hydrogenation fixed-bed units,the mass balance and energy balance within the phases in the reactor were taken into accounts in the form of ordinary differential equation.An application of the reactor model was performed for simulating the actual bench-scale plant of coal tar hydrogenation,the simulated results on the products yields and temperatures distribution along with the reactor are shown to be good consistent with the experimental data.

Highly selective and stable hydrogenation of heavy aromatic-naphthalene over transition metal phosphides

The present study reports a highly selective and stable catalytic approach for producing tetralin, an important chemical, solvent, and H2 storage material. Transition metal phosphides(Mo P, Ni2 P, Co2 P, and Fe2P) were prepared by wet impregnation and temperature-programmed reduction and characterized by X-ray diffraction(XRD), energy dispersive X-ray spectroscopy(EDX), EDX mapping, scanning electron microscopy(SEM), transmission electron microscopy(TEM), brunauer-emmettteller(BET), temperature-programmed desorption of ammonia(NH3-TPD), and fourier transform infrared spectroscopy of pyridine(pyridine-FTIR). Of all the transition metal phosphides Mo P was formed at a lower reduction temperature, which resulted in smaller particle size that enhanced the overall surface area of the catalyst. The existence of weak, moderate, and Lewis acidic sites over Mo P were responsible for its high tetralin selectivity(90%) and stability during the 100 h reaction on-stream in a fixed-bed reactor.