The purpose of this study is to develop novel P-Mo-V heteropoly compound catalysts for the oxidation of methacrolein to methacrylic acid.The introduction of Cu,as a modifying element,was employed to enhance the cataly...The purpose of this study is to develop novel P-Mo-V heteropoly compound catalysts for the oxidation of methacrolein to methacrylic acid.The introduction of Cu,as a modifying element,was employed to enhance the catalytic performance.Experimental results show that the addition of Cu significantly improved the catalyst performance,increasing the conversion rate of methacrolein from 17.2%to 84.2%,while the yield of methacrylic acid was boosted from 5.5%to 51.7%.A series of characterization results showed that both P-Mo-V and Cu-P-Mo-V catalysts primarily exhibited the crystal phase of[PMo_(12)O_(40)]^(3−),with a small amount of[PMo_(11)VO_(40)]^(3−)phase.However,the Cu-P-Mo-V catalyst exhibited much better oxidation–reduction ability compared to the P-Mo-V catalyst.Isolated Cu atoms were found to exist in a highly decentralized tetrahedral coordination structure,bridged by oxygen atoms within the heteropoly compound framework.The addition of Cu resulted in notable alterations in the modulation of the surface electronic structure,enhancement of oxidation–reduction ability,and optimization of the reaction pathway,thereby improving the overall catalytic activity of the catalyst.This study not only provides new insights into the modification of P-Mo-V heteropoly compound catalysts but also lays a foundation for understanding their catalytic mechanisms in organic synthesis reactions,demonstrating the potential of modifying elements in improving catalyst performance.展开更多
Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited p...Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited pH dependant swelling and solute diffusivity due to the formation or disruption of hydrogen bonded complexation between methacrylic acid (MAA) and etheric (EO). In neutral and basic conditions (above the swelling transition pH), the copolymer swelling was greatly higher than acid condition. In complexed hydrogels, the diffusion coefficients of vitamin B12 (VB12) were in the range of 10-10 to 10-7 cm2s-1; While in uncomplexed hydrogels, the values were about 210-6 cm2s-1. The comonomer composition and synthesis conditions have great effect on the structure, and thereby, swelling and solute diffusion characteristics of the resultant hydrogels. For the copolymers with composition of less than or more than 1:1 MAA/EO molar ratio, the plot of lnD vs 1/H-1 followed two different linear equations of 慺ree volume theory? respectively.展开更多
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 ex...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.展开更多
Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid...Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.展开更多
A full-relaxation optimization of molecule and the Dreiding force field are employed to obtain the geometry parameters and the conformational energy surfaces of meso or racemic dyad of poly(acrylic acid) (PAA) and pol...A full-relaxation optimization of molecule and the Dreiding force field are employed to obtain the geometry parameters and the conformational energy surfaces of meso or racemic dyad of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Three different carbonyl-bond orientations of side-groups resulted in the differences in depth of potential wells in their energetic contours for a meso or a racemic dyad. These discrepancies are interpreted as a result of various fine structures corresponding to grid search conformations as well as thereby different interactions. The analysis on the most stable conformations of PMAA confirmed that the ester groups are nearly perpendicular to the plane defined by the two adjacent skeletal bonds but may possibly change their relative orientations to meet the requirement of lower energy during the conformational state transition. For each polymer, two global energy maps of a meso and a racemic dyad were finally constructed from the superposition of energy data for the three kinds of side-group orientations by the Boltzmann factors. From an ensemble average, the proposed scheme with three rotational isomeric states (RIS) allowed us to access the experimentally unperturbed dimensions of PAA chain via the configurational statistical mechanics. Although the calculation was based on the short-range, local interactions, it was interested to note that the experimental characteristic ratios just fell within the range calculated for atactic chains.展开更多
The photo-controlled/living radical polymerization of methacrylic acid (MAA) was performed at room temperature by irradiation with a high-pressure mercury lamp using azo initiators and 4-methoxy-2,2,6,6-tetramethylpip...The photo-controlled/living radical polymerization of methacrylic acid (MAA) was performed at room temperature by irradiation with a high-pressure mercury lamp using azo initiators and 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator in the presence of (4-tert-butylphenyl)diphenylsulfonium triflate (tBuS) as the accelerator. Whereas the bulk polymerization yielded polymers with a bimodal molecular weight distribution in both the absence and presence of tBuS, the solution polymerization in methanol produced unimodal polymers with the molecular weight distribution of 2.0 - 2.3 in the presence of tBuS. The molecular weight distribution of the resulting poly (MAA) decreased with an in- crease in tBuS. The dilution of the monomer concentration also reduced the molecular weight distribution. The use of the initiator with a low 10-h half-life temperature also effectively controlled the molecular weight. The livingness of the polymerization was confirmed by obtaining linear increases in the first-order conversion versus time, the molecular weight versus the conversion, and the molecular weight versus the reciprocal of the initiator concentration.展开更多
Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH = 6.0 similar to 7.0, vinylene carbonate (VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reve...Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH = 6.0 similar to 7.0, vinylene carbonate (VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reverse-phase suspension polymerization and hydrophilic copolymeric supports were prepared. The properties of the supports were determined using trypsin and results show that the amount of enzymes coupled to the supports and the specific activity of immobilized trypsin are related to the content of VCA structure units, reaction time and concentration of enzyme solution, etc.展开更多
Poly (methacrylic acid-co-poloxamer) hydrogel networks were synthesized byfree-radical solution polymerization, and the dynamic swelling and in vitro release properties ofmodel drugs, dextromethorphan hydrobromide (DM...Poly (methacrylic acid-co-poloxamer) hydrogel networks were synthesized byfree-radical solution polymerization, and the dynamic swelling and in vitro release properties ofmodel drugs, dextromethorphan hydrobromide (DMP) and vitamin B_(12) (VB_(12)) were studied. Thesegels exhibited pH-dependant swelling and sustained drug release properties, and the water uptakerate and drug release rate in neutral or basic media were higher than that in acidic media. Theresults showed that the water uptake followed non-Fickian or zero order process in neutral or basicmedia, and the release of model drugs from hydrogels of appropriate composition was of zero orderkinetics over a period of several hours.展开更多
A highly efficient copolymer (methacrylic acid - co - styrene - divinylbenzene) in situ making high-performance liquid chromatographic column was prepared and evaluated. The column efficiency calculated in terms of he...A highly efficient copolymer (methacrylic acid - co - styrene - divinylbenzene) in situ making high-performance liquid chromatographic column was prepared and evaluated. The column efficiency calculated in terms of height equivalent to a theoretical plate was 25 mu m and rapid separations of small molecules such as substituted aromatic hydrocarbons and aromatic acids were achieved within five minutes.展开更多
The solid phase graft copolymerization of polypropylene (PP) andmethacrylic acid (MAA) was investigated. benzoyl peroxide(BPO) wasused as initia- tor. The influence of the reactive time,concentration of initiator and ...The solid phase graft copolymerization of polypropylene (PP) andmethacrylic acid (MAA) was investigated. benzoyl peroxide(BPO) wasused as initia- tor. The influence of the reactive time,concentration of initiator and monomer on degree of graft and meltflow index of graft copolymer(PP-MAA) was discussed. The effect ofgraft copolymer on mechanical properties of The glass fibre (GF)reinforced PP composites was also Studied. It is proved that graftcopolymer could obviously Increase the interfacial adhesive strengthbetween PP and GF.展开更多
Isobutyraldehyde was used as starting material via three steps: oxidation, chlorination and dehydro-chlorination to yield methacrylic acid. The total yield of methacrylic acid is 49.7%.
The kinetics of free-radical crosslinking co-polymerization(FRCCP)of acrylic acid(AA)with both methacrylic acid(MA)(PAMA hydrogel)and maleic acid(MAL)(PAMAL hydrogel)was investigated under the conditions of isothermal...The kinetics of free-radical crosslinking co-polymerization(FRCCP)of acrylic acid(AA)with both methacrylic acid(MA)(PAMA hydrogel)and maleic acid(MAL)(PAMAL hydrogel)was investigated under the conditions of isothermal conventional heating(CH)and under the conditions of microwave heating(MWH)with controlled cooling.The kinetics curves of FRCCP of PAMA and PAMAL hydrogels under the conditions of CH are described with the kinetics model of second order chemical reaction,whereas the kinetics curves under the conditions of CH are described with the kinetics model of Polany-Winger.It is proved that MWH leads to the changes in the rate of FRCCP and to the changes in the values of the kinetic parameters activation energy(Ea)and pre-exponential factor(lnA).It was found the existence of relationship between the values of the kinetic parameters calculated for MWH and CH for PAMA and PAMAL hydrogel synthesis process,which is well-known as compensation effect.The effect of MWH on the kinetics of FRCCP for PAMA and PAMAL hydrogel formation were explained by applying the model of activation by selective energy transfer(SET).The changes in kinetics model,rate of FRCCP and kinetics parameters,caused with the MWH can found wide application in designing novel technologies for obtaining polymers and for synthesis of polymers with novel physico-chemical properties.The suggested mechanism of activation for polymerisation under the conditions of MWH also enables development of novel reaction systems and technologies for polymers productions.展开更多
A novel environmental friendly catalyst, H3PW12O40/MCM-48, was prepared by impregnation method. The catalysts were characterized by means of XRD and FT-IR. The synthesis of n-butyl methacrylate catalyzed by H3PW12O40/...A novel environmental friendly catalyst, H3PW12O40/MCM-48, was prepared by impregnation method. The catalysts were characterized by means of XRD and FT-IR. The synthesis of n-butyl methacrylate catalyzed by H3PW12O40/MCM-48 was studied with methacrylic acid and n-butyl alcohol as reactants. H3PW12O40/MCM-48 is an excellent catalyst for synthesizing n-butyl methacrylate and Keggin structure of H3PW12O40 kept unchanged after being impregnated on surface of the molecular sieve support. Effects of n（methacrylic acid）：n（n-butyl alcohol）, catalyst dosage, cyclohexane（water-stripped reagent） and reaction time on yields of the product were investigated. The optimum conditions have been found, that is, molar ratio of acid to alcohol is 1：1.6, mass ratio of catalyst used to the reactants is 0.5% and reaction time is 2.0 h. Under these conditions, the yield of n-butyl methacrylate can reach 93.7%.展开更多
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 t...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.展开更多
A novel environmental friendly catalyst, H4SiW12O40/MCM-48, was prepared by impregnation method. The catalysts were characterized by means of XRD and FT-IR. The synthesis of n-butyl methacrylate catalyzed by H4SiW12O4...A novel environmental friendly catalyst, H4SiW12O40/MCM-48, was prepared by impregnation method. The catalysts were characterized by means of XRD and FT-IR. The synthesis of n-butyl methacrylate catalyzed by H4SiW12O40/MCM-48 was studied with methacrylic acid and n-butyl alcohol as reactants. H4SiW12O40/MCM-48 was an excellent catalyst for the synthesis of n-butyl methacrylate and Keggin structure ofH4SiW12O40 kept unchanged after impregnated on surface of the molecular sieve support. Effects of n（methacrylic acid）： n（n-butyl alcohol）, catalyst dosage, cyclohexane （water-stripped reagent） and reaction time on the yields of the product were investigated. The optimum conditions have been found, that is, molar ratio of acid to alcohol is 1：1.5, mass ratio of catalyst used to the reactant is 1.5%, cyclohexane is 10 mL and reaction time is 1.5h. Under these conditions, the yield of n-butyl methacrylate can reach 73.2%.展开更多
In this paper,low-temperature dielectric-blocked discharge plasma(DBD)was employed for the first time to treat silica-doped H_(4)PMo_(11)VO_(40)(HPAV)catalysts(DBD(Ar/x)-MF-Catal)and apply them in the catalytic methac...In this paper,low-temperature dielectric-blocked discharge plasma(DBD)was employed for the first time to treat silica-doped H_(4)PMo_(11)VO_(40)(HPAV)catalysts(DBD(Ar/x)-MF-Catal)and apply them in the catalytic methacrolein(MAL)selective oxidation to produce methacrylic acid(MAA).This work investigates in detail the controllable regulation of the concentration of oxidation states on silica-doped HPAV catalysts by adjusting the DBD discharge with controlled changes in voltage,current,treatment time,and treatment medium.It reports the intrinsic correlation between oxidation states and MAL oxidation performance.The research results indicated that the catalytic performance was related to the presence of oxygen vacancies and oxygen species(VO^(2+)),and are the main reason for the selective oxidation of MAL to MAA.Besides,the generation of oxygen vacancies and VO^(2+)altered localized electrons,which resulted in the easier activation of O_(2).Theoretical calculations of DFT also proved the formation mechanism of oxygen vacancies and VO^(2+)and electron properties on high-performance polymers,which elucidated the intrinsic influence of catalyst components.The DBD(Ar/10)-MF-Catal catalysts with suitable VO^(2+)and oxygen vacancy concentrations exhibited the highest catalytic performance with 90%MAL conversion and 70%MAA selectivity and showed good stability(500 h).展开更多
Oral ulcers may greatly diminish patient life quality and potentially result in malignant transformations.Using gels or films as pseudomembrane barriers is an effective method for promoting ulcer healing.However,these...Oral ulcers may greatly diminish patient life quality and potentially result in malignant transformations.Using gels or films as pseudomembrane barriers is an effective method for promoting ulcer healing.However,these pseudomembranes face challenges such as saliva flushing,dynamic changes,and the presence of abundant microorganisms in the complex oral environment.Herein,we developed an injectable,photoinduction,in situ-enhanceable oral ulcer repair hydrogel(named as GIL2)by incorporating dynamic phenylboronic acid ester bonds and imidazole ions into a methacrylated gelatin matrix.GIL2 exhibited rapid gelation(3 s),low swelling properties(1.07 g/g),robust tensile strength(56.83 kPa)and high adhesive strength(63.38 kPa),allowing it to adhere effectively to the ulcer surface.Moreover,the GIL2 demonstrated intrinsic antibacterial and antioxidant qualities.Within a diabetic rat model for oral ulcers,GIL2 effectively eased oxidative stress and decreased the inflammation present in ulcerated wounds,thereby greatly hastening the healing process of these ulcers.Together,GIL2 hydrogel demonstrates remarkable adaptability within the oral milieu,revitalizing clinical strategy advancements for treating bacterialinfected oral ulcers.展开更多
Traditional biodiesel production primarily uses methanol as the acyl acceptor,but its toxicity to lipase increases process complexity and operational difficulty elevate manufacturing costs.This study aimed to explore ...Traditional biodiesel production primarily uses methanol as the acyl acceptor,but its toxicity to lipase increases process complexity and operational difficulty elevate manufacturing costs.This study aimed to explore a new method for enzymatic synthesis of biodiesel with methyl methacrylate(MMA)as acyl acceptor.Meanwhile,a 1,3-position specific lipase Lipozyme RM IM was applied as biocatalyst,which enables simultaneous production of biodiesel(FAMEs)and methacrylate fatty acid glycerides(MFAGs)via specific sn-1,3 transesterification of MMA with triglyceride.Under the optimal reaction conditions:temperature of 50℃,molar ratio of 4:1 for MMA to triglyceride,enzyme dosage of 7.5%(mass),and an extra water addition of 0.5%(mass);triglyceride conversion rate of 97%,and FAMEs yield of 65%could be obtained.Simultaneously,the multistage short-path distillation and column chromatographic method were combined used for the separation of the mixed products.Finally,the purity of FAME,MFADG,DMFAG,and MMFAG were 98%,97.8%,95.3%,and 81.78%,respectively.In this new approach,MMA demonstrates lower toxicity to lipases,allowing for straightfo rward addition of all the substrates without complex addition process,and enhancing operational feasibility.Meanwhile,the by-products of MFAGs could be applied as monomers in varnishes and protective coatings,which increased the value of the products.Thus,this investigation providing an alternative way to produce biodiesel,and providing a new pathway for the sustainable development of biodiesel.展开更多
Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites;however,traditional compatibilization by copolymers(pre-made or in-situ generation)suffers from weak interfac...Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites;however,traditional compatibilization by copolymers(pre-made or in-situ generation)suffers from weak interface anchoring,and inorganic particles have gained extensive attention recently owing to their large interfacial desorption energy,while their low affinity to bulk components is a drawback.In this study,an interfacial atom transfer radical polymerization(ATRP)technique was employed to grow polystyrene(PS)and poly(2-hydroxyethyl methacrylate)(PHEMA)simultaneously on different hemispheres of Br-functionalized SiO_(2) nanoparticles to stabilize a Pickering emulsion,whereby a brush-type Janus nanoparticle(SiO_(2)@JNP)was developed.The polymer brushes were well-characterized,and the Janus feature was validated by transmission electron microscope(TEM)observation of the sole hemisphere grafting of SiO_(2)-PS as a control sample.SiO_(2)@JNP was demonstrated to be an efficient compatibilizer for a PS/poly(methyl methacrylate)(PMMA)immiscible blend,and the droplet-matrix morphology was significantly refined.The mechanical strength and toughness of the blend were synchronously enhanced at a low content SiO_(2)@JNP optimized~0.9 wt%,with the tensile strength,elongation at break and impact strength increased by 17.7%,26.6%and 19.6%,respectively.This enhancement may be attributed to the entanglements between the grafted polymer brushes and individual components that improve the particle-bulk phase affinity and enforce interfacial adhesion.展开更多
Temporary plugging and diversion fracturing(TPDF)is widely used to promote the uniform and complex distribution of multi-clustered hydraulic fractures(HFs)in a horizontal well of the unconventional formations.However,...Temporary plugging and diversion fracturing(TPDF)is widely used to promote the uniform and complex distribution of multi-clustered hydraulic fractures(HFs)in a horizontal well of the unconventional formations.However,the migration behavior of temporary plugging agent(TPA),as a function of the concentration and particle size of TPA and cluster-perforation numbers,etc.,determining the effectiveness of this technique,remains unclear.Therefore,this study conducted innovatively a series of TPDF simulation experiments on transparent polymethyl methacrylate(PMMA)specimens(cubic block of 30 cm×30 cm×30 cm)to explore visually the migration behavior of TPA in multi-clustered HFs in a horizontal well.A laboratory hydraulic sandblasting perforation completion technique was implemented to simulate the multi-cluster perforations.All the distributions of wellbore,perforations,HFs,and TPA can be seen clearly inside the PMMA specimen post the experiment.The results show that there are four characteristic plugging positions for the TPA:mouth of HF,middle of HF,tip of HF,and the intersection of HFs.Small particle size TPA tends to migrate to the fracture tip for plugging,while large particle size TPA tends to plug at the fracture mouth.The migration of the TPA is influenced obviously by the morphology of the fracture wall.A smooth fracture wall is conducive to the migration of the TPA to the far end of HFs,but not conducive to generating the plugging zone and HF diversion.In contrast,a"leaf vein"fracture of rough wall is conducive to generating the plugging layer and the diversion of HFs,but not conducive to the migration of the TPA to the far end of HFs.The migration ability of TPA in a"shell"pattern is intermediate between the two above cases.Increasing TPA concentration can encourage TPA to migrate more quickly to the characteristic plugging position,and thereby to promote the creation of effective plugging and subsequently the multi-stage diversion of the HFs.Nevertheless,excessive concentration may cause the TPA to settle prematurely,affecting the propagation of the HFs to the far end.Increasing the number of clusters to a certain extent can encourage TPA to migrate into the HFs and form plugging,and promote the diversion.An evaluation system for the migration ability of granular TPA has been established,and it was calculated that when there is no plugging expectation target,the comprehensive migration ability of small particle size TPA is stronger than that of large particle size TPA.This research provides theoretical foundation for the optimization of temporary plugging parameters.展开更多
基金funding support received from China Petrochemical Corporation(Sinopec Group).
文摘The purpose of this study is to develop novel P-Mo-V heteropoly compound catalysts for the oxidation of methacrolein to methacrylic acid.The introduction of Cu,as a modifying element,was employed to enhance the catalytic performance.Experimental results show that the addition of Cu significantly improved the catalyst performance,increasing the conversion rate of methacrolein from 17.2%to 84.2%,while the yield of methacrylic acid was boosted from 5.5%to 51.7%.A series of characterization results showed that both P-Mo-V and Cu-P-Mo-V catalysts primarily exhibited the crystal phase of[PMo_(12)O_(40)]^(3−),with a small amount of[PMo_(11)VO_(40)]^(3−)phase.However,the Cu-P-Mo-V catalyst exhibited much better oxidation–reduction ability compared to the P-Mo-V catalyst.Isolated Cu atoms were found to exist in a highly decentralized tetrahedral coordination structure,bridged by oxygen atoms within the heteropoly compound framework.The addition of Cu resulted in notable alterations in the modulation of the surface electronic structure,enhancement of oxidation–reduction ability,and optimization of the reaction pathway,thereby improving the overall catalytic activity of the catalyst.This study not only provides new insights into the modification of P-Mo-V heteropoly compound catalysts but also lays a foundation for understanding their catalytic mechanisms in organic synthesis reactions,demonstrating the potential of modifying elements in improving catalyst performance.
文摘Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited pH dependant swelling and solute diffusivity due to the formation or disruption of hydrogen bonded complexation between methacrylic acid (MAA) and etheric (EO). In neutral and basic conditions (above the swelling transition pH), the copolymer swelling was greatly higher than acid condition. In complexed hydrogels, the diffusion coefficients of vitamin B12 (VB12) were in the range of 10-10 to 10-7 cm2s-1; While in uncomplexed hydrogels, the values were about 210-6 cm2s-1. The comonomer composition and synthesis conditions have great effect on the structure, and thereby, swelling and solute diffusion characteristics of the resultant hydrogels. For the copolymers with composition of less than or more than 1:1 MAA/EO molar ratio, the plot of lnD vs 1/H-1 followed two different linear equations of 慺ree volume theory? respectively.
基金Support by the National Key Projects for Fundamental Research and Development of China(2016YFB0601303)Key Research Program of Frontier Sciences,CAS,(QYZDBSSW-SLH022)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering(2017-K08).
文摘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.
基金supported by the National Natural Science Foundation of China(Grant No.21978066)Basic Research Program of Hebei Province for Natural Science Foundation and Key Basic Research Project(Grant No.18964308D)the Key Program of Natural Science Foundation of Hebei Province(Grant No.B2020202048).
文摘Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.
基金This work was supported by the Youth Science Foundation of Acedemia Sinica the China Postdoctoral Science Foundation, the National Natural Science Foundation of China, and Polymer Physics Laboratory,Academia Sinica
文摘A full-relaxation optimization of molecule and the Dreiding force field are employed to obtain the geometry parameters and the conformational energy surfaces of meso or racemic dyad of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Three different carbonyl-bond orientations of side-groups resulted in the differences in depth of potential wells in their energetic contours for a meso or a racemic dyad. These discrepancies are interpreted as a result of various fine structures corresponding to grid search conformations as well as thereby different interactions. The analysis on the most stable conformations of PMAA confirmed that the ester groups are nearly perpendicular to the plane defined by the two adjacent skeletal bonds but may possibly change their relative orientations to meet the requirement of lower energy during the conformational state transition. For each polymer, two global energy maps of a meso and a racemic dyad were finally constructed from the superposition of energy data for the three kinds of side-group orientations by the Boltzmann factors. From an ensemble average, the proposed scheme with three rotational isomeric states (RIS) allowed us to access the experimentally unperturbed dimensions of PAA chain via the configurational statistical mechanics. Although the calculation was based on the short-range, local interactions, it was interested to note that the experimental characteristic ratios just fell within the range calculated for atactic chains.
文摘The photo-controlled/living radical polymerization of methacrylic acid (MAA) was performed at room temperature by irradiation with a high-pressure mercury lamp using azo initiators and 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator in the presence of (4-tert-butylphenyl)diphenylsulfonium triflate (tBuS) as the accelerator. Whereas the bulk polymerization yielded polymers with a bimodal molecular weight distribution in both the absence and presence of tBuS, the solution polymerization in methanol produced unimodal polymers with the molecular weight distribution of 2.0 - 2.3 in the presence of tBuS. The molecular weight distribution of the resulting poly (MAA) decreased with an in- crease in tBuS. The dilution of the monomer concentration also reduced the molecular weight distribution. The use of the initiator with a low 10-h half-life temperature also effectively controlled the molecular weight. The livingness of the polymerization was confirmed by obtaining linear increases in the first-order conversion versus time, the molecular weight versus the conversion, and the molecular weight versus the reciprocal of the initiator concentration.
文摘Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH = 6.0 similar to 7.0, vinylene carbonate (VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reverse-phase suspension polymerization and hydrophilic copolymeric supports were prepared. The properties of the supports were determined using trypsin and results show that the amount of enzymes coupled to the supports and the specific activity of immobilized trypsin are related to the content of VCA structure units, reaction time and concentration of enzyme solution, etc.
文摘Poly (methacrylic acid-co-poloxamer) hydrogel networks were synthesized byfree-radical solution polymerization, and the dynamic swelling and in vitro release properties ofmodel drugs, dextromethorphan hydrobromide (DMP) and vitamin B_(12) (VB_(12)) were studied. Thesegels exhibited pH-dependant swelling and sustained drug release properties, and the water uptakerate and drug release rate in neutral or basic media were higher than that in acidic media. Theresults showed that the water uptake followed non-Fickian or zero order process in neutral or basicmedia, and the release of model drugs from hydrogels of appropriate composition was of zero orderkinetics over a period of several hours.
文摘A highly efficient copolymer (methacrylic acid - co - styrene - divinylbenzene) in situ making high-performance liquid chromatographic column was prepared and evaluated. The column efficiency calculated in terms of height equivalent to a theoretical plate was 25 mu m and rapid separations of small molecules such as substituted aromatic hydrocarbons and aromatic acids were achieved within five minutes.
文摘The solid phase graft copolymerization of polypropylene (PP) andmethacrylic acid (MAA) was investigated. benzoyl peroxide(BPO) wasused as initia- tor. The influence of the reactive time,concentration of initiator and monomer on degree of graft and meltflow index of graft copolymer(PP-MAA) was discussed. The effect ofgraft copolymer on mechanical properties of The glass fibre (GF)reinforced PP composites was also Studied. It is proved that graftcopolymer could obviously Increase the interfacial adhesive strengthbetween PP and GF.
文摘Isobutyraldehyde was used as starting material via three steps: oxidation, chlorination and dehydro-chlorination to yield methacrylic acid. The total yield of methacrylic acid is 49.7%.
基金the Ministry of Science and Technical Development of the Republic of Serbia,through Project No.172015 OI.
文摘The kinetics of free-radical crosslinking co-polymerization(FRCCP)of acrylic acid(AA)with both methacrylic acid(MA)(PAMA hydrogel)and maleic acid(MAL)(PAMAL hydrogel)was investigated under the conditions of isothermal conventional heating(CH)and under the conditions of microwave heating(MWH)with controlled cooling.The kinetics curves of FRCCP of PAMA and PAMAL hydrogels under the conditions of CH are described with the kinetics model of second order chemical reaction,whereas the kinetics curves under the conditions of CH are described with the kinetics model of Polany-Winger.It is proved that MWH leads to the changes in the rate of FRCCP and to the changes in the values of the kinetic parameters activation energy(Ea)and pre-exponential factor(lnA).It was found the existence of relationship between the values of the kinetic parameters calculated for MWH and CH for PAMA and PAMAL hydrogel synthesis process,which is well-known as compensation effect.The effect of MWH on the kinetics of FRCCP for PAMA and PAMAL hydrogel formation were explained by applying the model of activation by selective energy transfer(SET).The changes in kinetics model,rate of FRCCP and kinetics parameters,caused with the MWH can found wide application in designing novel technologies for obtaining polymers and for synthesis of polymers with novel physico-chemical properties.The suggested mechanism of activation for polymerisation under the conditions of MWH also enables development of novel reaction systems and technologies for polymers productions.
基金Funded by the Natural Science Foundation of Hubei Province,China(No.2005ABA053)the National Natural ScienceFoundation of China(No.20471044)
文摘A novel environmental friendly catalyst, H3PW12O40/MCM-48, was prepared by impregnation method. The catalysts were characterized by means of XRD and FT-IR. The synthesis of n-butyl methacrylate catalyzed by H3PW12O40/MCM-48 was studied with methacrylic acid and n-butyl alcohol as reactants. H3PW12O40/MCM-48 is an excellent catalyst for synthesizing n-butyl methacrylate and Keggin structure of H3PW12O40 kept unchanged after being impregnated on surface of the molecular sieve support. Effects of n（methacrylic acid）：n（n-butyl alcohol）, catalyst dosage, cyclohexane（water-stripped reagent） and reaction time on yields of the product were investigated. The optimum conditions have been found, that is, molar ratio of acid to alcohol is 1：1.6, mass ratio of catalyst used to the reactants is 0.5% and reaction time is 2.0 h. Under these conditions, the yield of n-butyl methacrylate can reach 93.7%.
基金the National Natural Science Fund for Distinguished Young Scholars(22025803)supported by the National Natural Science Foundation of China(22178338)+1 种基金the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(YLU-DNL Fund 2021018)the financial support of project“Research and development and industrial application of new catalytic materials for green synthesis of MMA to replace highly toxic HCN”(Hebei,20374002D)。
文摘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.
基金Acknowledgment： This work was financially supported by the Natural Science Foundation of Hubei Province, China （No. 2005ABA053） and Hubei Normal University.
文摘A novel environmental friendly catalyst, H4SiW12O40/MCM-48, was prepared by impregnation method. The catalysts were characterized by means of XRD and FT-IR. The synthesis of n-butyl methacrylate catalyzed by H4SiW12O40/MCM-48 was studied with methacrylic acid and n-butyl alcohol as reactants. H4SiW12O40/MCM-48 was an excellent catalyst for the synthesis of n-butyl methacrylate and Keggin structure ofH4SiW12O40 kept unchanged after impregnated on surface of the molecular sieve support. Effects of n（methacrylic acid）： n（n-butyl alcohol）, catalyst dosage, cyclohexane （water-stripped reagent） and reaction time on the yields of the product were investigated. The optimum conditions have been found, that is, molar ratio of acid to alcohol is 1：1.5, mass ratio of catalyst used to the reactant is 1.5%, cyclohexane is 10 mL and reaction time is 1.5h. Under these conditions, the yield of n-butyl methacrylate can reach 73.2%.
基金financially supported by the Taishan Scholars Program of Shandong Province(No.tsqn202103051)the Science and Technology Project of Xinjiang Bingtuan Supported by the Central Government(No.2022BC001)the Project of Scientific Research in Shihezi University(No.CXFZ202205)。
文摘In this paper,low-temperature dielectric-blocked discharge plasma(DBD)was employed for the first time to treat silica-doped H_(4)PMo_(11)VO_(40)(HPAV)catalysts(DBD(Ar/x)-MF-Catal)and apply them in the catalytic methacrolein(MAL)selective oxidation to produce methacrylic acid(MAA).This work investigates in detail the controllable regulation of the concentration of oxidation states on silica-doped HPAV catalysts by adjusting the DBD discharge with controlled changes in voltage,current,treatment time,and treatment medium.It reports the intrinsic correlation between oxidation states and MAL oxidation performance.The research results indicated that the catalytic performance was related to the presence of oxygen vacancies and oxygen species(VO^(2+)),and are the main reason for the selective oxidation of MAL to MAA.Besides,the generation of oxygen vacancies and VO^(2+)altered localized electrons,which resulted in the easier activation of O_(2).Theoretical calculations of DFT also proved the formation mechanism of oxygen vacancies and VO^(2+)and electron properties on high-performance polymers,which elucidated the intrinsic influence of catalyst components.The DBD(Ar/10)-MF-Catal catalysts with suitable VO^(2+)and oxygen vacancy concentrations exhibited the highest catalytic performance with 90%MAL conversion and 70%MAA selectivity and showed good stability(500 h).
基金funding from the National Natural Science Foundation of China(Nos.82071170 and 82371016)the Zhejiang Provincial Science and Technology Project for Public Welfare(No.LGF21H140004).
文摘Oral ulcers may greatly diminish patient life quality and potentially result in malignant transformations.Using gels or films as pseudomembrane barriers is an effective method for promoting ulcer healing.However,these pseudomembranes face challenges such as saliva flushing,dynamic changes,and the presence of abundant microorganisms in the complex oral environment.Herein,we developed an injectable,photoinduction,in situ-enhanceable oral ulcer repair hydrogel(named as GIL2)by incorporating dynamic phenylboronic acid ester bonds and imidazole ions into a methacrylated gelatin matrix.GIL2 exhibited rapid gelation(3 s),low swelling properties(1.07 g/g),robust tensile strength(56.83 kPa)and high adhesive strength(63.38 kPa),allowing it to adhere effectively to the ulcer surface.Moreover,the GIL2 demonstrated intrinsic antibacterial and antioxidant qualities.Within a diabetic rat model for oral ulcers,GIL2 effectively eased oxidative stress and decreased the inflammation present in ulcerated wounds,thereby greatly hastening the healing process of these ulcers.Together,GIL2 hydrogel demonstrates remarkable adaptability within the oral milieu,revitalizing clinical strategy advancements for treating bacterialinfected oral ulcers.
文摘Traditional biodiesel production primarily uses methanol as the acyl acceptor,but its toxicity to lipase increases process complexity and operational difficulty elevate manufacturing costs.This study aimed to explore a new method for enzymatic synthesis of biodiesel with methyl methacrylate(MMA)as acyl acceptor.Meanwhile,a 1,3-position specific lipase Lipozyme RM IM was applied as biocatalyst,which enables simultaneous production of biodiesel(FAMEs)and methacrylate fatty acid glycerides(MFAGs)via specific sn-1,3 transesterification of MMA with triglyceride.Under the optimal reaction conditions:temperature of 50℃,molar ratio of 4:1 for MMA to triglyceride,enzyme dosage of 7.5%(mass),and an extra water addition of 0.5%(mass);triglyceride conversion rate of 97%,and FAMEs yield of 65%could be obtained.Simultaneously,the multistage short-path distillation and column chromatographic method were combined used for the separation of the mixed products.Finally,the purity of FAME,MFADG,DMFAG,and MMFAG were 98%,97.8%,95.3%,and 81.78%,respectively.In this new approach,MMA demonstrates lower toxicity to lipases,allowing for straightfo rward addition of all the substrates without complex addition process,and enhancing operational feasibility.Meanwhile,the by-products of MFAGs could be applied as monomers in varnishes and protective coatings,which increased the value of the products.Thus,this investigation providing an alternative way to produce biodiesel,and providing a new pathway for the sustainable development of biodiesel.
基金financially supported by the National Natural Science Foundation of China(Nos.22172028,21903015,and 22403017)Natural Science Foundation of Fujian Province of China(No.2022J05041)。
文摘Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites;however,traditional compatibilization by copolymers(pre-made or in-situ generation)suffers from weak interface anchoring,and inorganic particles have gained extensive attention recently owing to their large interfacial desorption energy,while their low affinity to bulk components is a drawback.In this study,an interfacial atom transfer radical polymerization(ATRP)technique was employed to grow polystyrene(PS)and poly(2-hydroxyethyl methacrylate)(PHEMA)simultaneously on different hemispheres of Br-functionalized SiO_(2) nanoparticles to stabilize a Pickering emulsion,whereby a brush-type Janus nanoparticle(SiO_(2)@JNP)was developed.The polymer brushes were well-characterized,and the Janus feature was validated by transmission electron microscope(TEM)observation of the sole hemisphere grafting of SiO_(2)-PS as a control sample.SiO_(2)@JNP was demonstrated to be an efficient compatibilizer for a PS/poly(methyl methacrylate)(PMMA)immiscible blend,and the droplet-matrix morphology was significantly refined.The mechanical strength and toughness of the blend were synchronously enhanced at a low content SiO_(2)@JNP optimized~0.9 wt%,with the tensile strength,elongation at break and impact strength increased by 17.7%,26.6%and 19.6%,respectively.This enhancement may be attributed to the entanglements between the grafted polymer brushes and individual components that improve the particle-bulk phase affinity and enforce interfacial adhesion.
基金supported by the National Natural Science Foundation of China Joint Fund for Enterprise Innovation and Development,Enrichment Mechanism and Stereoscopic Development of Shale Oil in Continental Rift Basins(No.U24B6002).
文摘Temporary plugging and diversion fracturing(TPDF)is widely used to promote the uniform and complex distribution of multi-clustered hydraulic fractures(HFs)in a horizontal well of the unconventional formations.However,the migration behavior of temporary plugging agent(TPA),as a function of the concentration and particle size of TPA and cluster-perforation numbers,etc.,determining the effectiveness of this technique,remains unclear.Therefore,this study conducted innovatively a series of TPDF simulation experiments on transparent polymethyl methacrylate(PMMA)specimens(cubic block of 30 cm×30 cm×30 cm)to explore visually the migration behavior of TPA in multi-clustered HFs in a horizontal well.A laboratory hydraulic sandblasting perforation completion technique was implemented to simulate the multi-cluster perforations.All the distributions of wellbore,perforations,HFs,and TPA can be seen clearly inside the PMMA specimen post the experiment.The results show that there are four characteristic plugging positions for the TPA:mouth of HF,middle of HF,tip of HF,and the intersection of HFs.Small particle size TPA tends to migrate to the fracture tip for plugging,while large particle size TPA tends to plug at the fracture mouth.The migration of the TPA is influenced obviously by the morphology of the fracture wall.A smooth fracture wall is conducive to the migration of the TPA to the far end of HFs,but not conducive to generating the plugging zone and HF diversion.In contrast,a"leaf vein"fracture of rough wall is conducive to generating the plugging layer and the diversion of HFs,but not conducive to the migration of the TPA to the far end of HFs.The migration ability of TPA in a"shell"pattern is intermediate between the two above cases.Increasing TPA concentration can encourage TPA to migrate more quickly to the characteristic plugging position,and thereby to promote the creation of effective plugging and subsequently the multi-stage diversion of the HFs.Nevertheless,excessive concentration may cause the TPA to settle prematurely,affecting the propagation of the HFs to the far end.Increasing the number of clusters to a certain extent can encourage TPA to migrate into the HFs and form plugging,and promote the diversion.An evaluation system for the migration ability of granular TPA has been established,and it was calculated that when there is no plugging expectation target,the comprehensive migration ability of small particle size TPA is stronger than that of large particle size TPA.This research provides theoretical foundation for the optimization of temporary plugging parameters.
