As a natural organic polymer,xanthan gum(XG)can alleviate the plastic deformation of gel ink under strong stress and realize the reasonable regulation of the rheological properties of gel ink.However,as the double-hel...As a natural organic polymer,xanthan gum(XG)can alleviate the plastic deformation of gel ink under strong stress and realize the reasonable regulation of the rheological properties of gel ink.However,as the double-helix structure connected by hydrogen bonds cannot resist the mechanical environment of strong stress,XG shows poor shear resistance.In this study,a polymer gel with interpenetrating polymer network structure was prepared by esterifying XG,taking polystyrene maleic anhydride(SMA)as the modifier.In addition to retaining the excellent rheological properties of XG,the generated polymer gel also exhibited high shear resistance.The optimal addition amount of the esterification reaction modifier was determined as mXG:mSMA=5:3 according to the gel ink standard.With this amount,the viscosity of the modified xanthan gum(SXG)gel increased to 1578.8 mPa·s and 100.7 mPa·s at shear rates of 4 s1 and 383 s1,respectively,and the shear resistance increased more than 2 times compared to the unmodified one.It is because of the ester bond formed by esterification that the reaction strengthens the interaction between molecular segments,enabling the new gel to resist to strong mechanical stress.The new polymer gel studied in this paper and the proposed mechanism of action provide new insights for the development of high-end gel ink and also provide theoretical support for the study of rheological properties of non-Newtonian fluids.展开更多
The selective oxidative esterification of aldehydes with alcohols to the corresponding esters has been one of the hot spots in scientific research and industrial synthesis.However,the application of precious metal cat...The selective oxidative esterification of aldehydes with alcohols to the corresponding esters has been one of the hot spots in scientific research and industrial synthesis.However,the application of precious metal catalytic systems is limited by their complicated synthetic steps and high cost.Thus a highly efficient,green,recyclable selective synthesis method of esters catalyzed by polyoxovanadate(POV)-based molecu-lar catalysts has been developed in this paper.The results show that supramolecular interaction between POV and 1,3-dibenzylimidazolium bromide(Act_(2)Im)can efficiently convert alcohols and aldehydes to the corresponding esters in high yield under much milder conditions.Mechanistic insight is also provided based on the control experiments,single crystal X-ray diffraction and cyclic voltammetry studies.展开更多
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 ...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.展开更多
Based on a strategy of ground-state destabilisation of the N—C bond,a general protocol for the esterification of amides with carbohydrates was reported.This protocol offers mild reaction conditions,excellent yields,a...Based on a strategy of ground-state destabilisation of the N—C bond,a general protocol for the esterification of amides with carbohydrates was reported.This protocol offers mild reaction conditions,excellent yields,and broad substrate compatibility,thereby demonstrating great potential for the synthesis of glycoconjugates.Additionally,this method provides an alternative approach for addressing the challenging task of esterifying sterically hindered secondary hydroxyl group of carbohydrates and paving the way for advancements in carbohydrate-based pharmaceuticals.展开更多
Dioctyl sebacate(DOS)is an organic ester compound,mainly used as a low-temperature plasticizer and synthetic antirust and cold-resistant ester lubricant base oil.This study discusses the use of synthesized molybdenum ...Dioctyl sebacate(DOS)is an organic ester compound,mainly used as a low-temperature plasticizer and synthetic antirust and cold-resistant ester lubricant base oil.This study discusses the use of synthesized molybdenum disulfide/C60(MoS_(2)/C_(60))composite particles as catalysts to synthesize a new type of DOS endowed with high lubricity.This was achieved through a catalytic esterification reaction between sebacic acid and 1-octanol.After the reaction,MoS_(2)/C_(60) was dispersed in situ in this novel DOS to form a suspension(MoS_(2)/C_(60)/DOS).The tribological properties of MoS_(2)/C_(60)/DOS were examined through high-frequency reciprocating friction and wear experiments,and the friction and wear mechanisms were analyzed.The results show that MoS_(2)/C_(60)/DOS can significantly enhance the antiwear and friction reduction performance compared to commercial DOS by 91% and 95%,respectively,achieving an ultra-low friction state with an average friction coefficient of 0.006.A friction film containing elements such as Fe,O,C,Mo,and S forms on the friction surface,significantly improving the lubrication state of the friction interface and achieving low friction.展开更多
The transformation of biomasses from agro-industrial waste can significantly impact the production of green chemicals from sustainable resources.Pectin is a biopolymer present in lignocellulosic biomass as Orange Peel...The transformation of biomasses from agro-industrial waste can significantly impact the production of green chemicals from sustainable resources.Pectin is a biopolymer present in lignocellulosic biomass as Orange Peel Waste(OPW)and has possibilities for making platform compounds such as furfural for sustainable chemistry.In this work,we studied the transformation to furfural of OPW,pectins,and d-galacturonic acid(D-GalA),which is the main component(65 wt%)of pectin.We analyzed pectins with different degrees of esterification(45,60 and 95 DE)in a one-pot hydrolysis reaction system and studied the differences in depolymerization and dehydration of the carbohydrates.The results show that the production of furfural decreases as the DE value increases.Specifically,low DE values favor the formation of furfural since the decarboxylation reaction is favored over deesterification.Interestingly,the furfural concentration is dependent upon the polysaccharide composition of pentoses and uronic acid.The obtained concentrations of furfural(13 and 14 mmol/L),d-xylose(6.2 and 10 mmol/L),and L-arabinose(2.5 and 2.7 mmol/L)remained the same when the galacturonic acid was fed either as a polymer or a monomer under the same reaction conditions(0.01 M SA,90 min and 433 K).OPW is proposed as a feedstock in a biorefinery,in which on a per kg OPW dry basis,90 g of pectin and 15 g of furfural were produced in the most favorable case.We conclude that the co-production of pectin and furfural from OPW is economically feasible.展开更多
A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4. The structure and acidity of the catalyst were characterized by Fourier transform infrared spe...A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4. The structure and acidity of the catalyst were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, thermogravimetric analysis, X‐ray photoelectron spectroscopy, and elemental analysis, which showed that it was an amorphous carbon material composed of aromatic carbon sheets in random orientations. Sulfonic acid groups were present on the surface at a density of 0.81 mmol/g. The carbon solid acid catalyst showed better performance than HZSM‐5 for the esterification of cyclohexene with formic acid. At a3：1 molar ratio of formic acid to cyclohexene, catalyst loading of 0.07 g/mL of cyclohexene, and reaction time of 1 h at 413 K, the cyclohexene conversion was 88.4% with 97.3% selectivity to cyclohexyl formate. The carbon solid acid catalyst showed better reusability than HZSM‐5 because its large pores were minimally affected by the accumulation of oligomerized cyclohexene, which deactivated HZSM‐5. The activity of the carbon solid acid catalyst decreased somewhat in the first two recycles due to the leaching of polycyclic aromatic hydrocarbon containing –SO3H groups and then it remained constant in the following reuse.展开更多
Fhnctionalized ionic liquid samples （bmim-PW12） were synthesized by 1-butyl-3-methyl- imidazolium bromide （bmimBr） and 12-phosphotungstic heteropolyacid （PW12）. The samples were annealed at 100-450 ℃ and were c...Fhnctionalized ionic liquid samples （bmim-PW12） were synthesized by 1-butyl-3-methyl- imidazolium bromide （bmimBr） and 12-phosphotungstic heteropolyacid （PW12）. The samples were annealed at 100-450 ℃ and were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, thermal gravity-DTG, brunauer emmett teller, and NHa-temperature programmed desorption. The results showed that the bmim-PW12 samples were crystal and maintained intact Keggin structure. The organic parts of those samples were partly decomposed at a temperature more than 350 ℃. The sample annealed at 400 ℃ exhibited nano-porous structure, strong acidity, and excellent catalytic activity on the esterification of n-butanol with acetic acid. The higher ester yield was obtained when the mass ratio of catalyst over the reactants amount was 5% for bmim-PW12 catalyst annealed at 400 ℃.展开更多
Esterification of carboxylic acid with equimolar amounts alcohol can be efficiently catalyzed by biphasic 4-(benzylamino)formoyldiphenylammonium triflate (BDPAT, 3) in good yield. The catalyst can be easily recovered...Esterification of carboxylic acid with equimolar amounts alcohol can be efficiently catalyzed by biphasic 4-(benzylamino)formoyldiphenylammonium triflate (BDPAT, 3) in good yield. The catalyst can be easily recovered without loss of activity.展开更多
基金supported by Shanxi Provincial Science and Technology Achievement Transformation Guidance Special Program of China(202104021301052)Shanxi Provincial Patent Transformation Special Plan Project(202202054,202306013).
文摘As a natural organic polymer,xanthan gum(XG)can alleviate the plastic deformation of gel ink under strong stress and realize the reasonable regulation of the rheological properties of gel ink.However,as the double-helix structure connected by hydrogen bonds cannot resist the mechanical environment of strong stress,XG shows poor shear resistance.In this study,a polymer gel with interpenetrating polymer network structure was prepared by esterifying XG,taking polystyrene maleic anhydride(SMA)as the modifier.In addition to retaining the excellent rheological properties of XG,the generated polymer gel also exhibited high shear resistance.The optimal addition amount of the esterification reaction modifier was determined as mXG:mSMA=5:3 according to the gel ink standard.With this amount,the viscosity of the modified xanthan gum(SXG)gel increased to 1578.8 mPa·s and 100.7 mPa·s at shear rates of 4 s1 and 383 s1,respectively,and the shear resistance increased more than 2 times compared to the unmodified one.It is because of the ester bond formed by esterification that the reaction strengthens the interaction between molecular segments,enabling the new gel to resist to strong mechanical stress.The new polymer gel studied in this paper and the proposed mechanism of action provide new insights for the development of high-end gel ink and also provide theoretical support for the study of rheological properties of non-Newtonian fluids.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.22371158,21801153,21225103)2021-2023 Intergovernmental S&T Cooperation Project No.1 between China and Serbia,Tsinghua University Initiative Foundation Research Program(No.20131089204)the State Key Laboratory of Natural and Biomimetic Drugs(No.K202008).
文摘The selective oxidative esterification of aldehydes with alcohols to the corresponding esters has been one of the hot spots in scientific research and industrial synthesis.However,the application of precious metal catalytic systems is limited by their complicated synthetic steps and high cost.Thus a highly efficient,green,recyclable selective synthesis method of esters catalyzed by polyoxovanadate(POV)-based molecu-lar catalysts has been developed in this paper.The results show that supramolecular interaction between POV and 1,3-dibenzylimidazolium bromide(Act_(2)Im)can efficiently convert alcohols and aldehydes to the corresponding esters in high yield under much milder conditions.Mechanistic insight is also provided based on the control experiments,single crystal X-ray diffraction and cyclic voltammetry studies.
基金supported by the National Research and Development Program of China(2021YFC3001100)the National Natural Science Foundation of China(22288102).
文摘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.
文摘Based on a strategy of ground-state destabilisation of the N—C bond,a general protocol for the esterification of amides with carbohydrates was reported.This protocol offers mild reaction conditions,excellent yields,and broad substrate compatibility,thereby demonstrating great potential for the synthesis of glycoconjugates.Additionally,this method provides an alternative approach for addressing the challenging task of esterifying sterically hindered secondary hydroxyl group of carbohydrates and paving the way for advancements in carbohydrate-based pharmaceuticals.
基金The financial support from the National Natural Science Foundation of China(52075141,52075144)is gratefully acknowledged.
文摘Dioctyl sebacate(DOS)is an organic ester compound,mainly used as a low-temperature plasticizer and synthetic antirust and cold-resistant ester lubricant base oil.This study discusses the use of synthesized molybdenum disulfide/C60(MoS_(2)/C_(60))composite particles as catalysts to synthesize a new type of DOS endowed with high lubricity.This was achieved through a catalytic esterification reaction between sebacic acid and 1-octanol.After the reaction,MoS_(2)/C_(60) was dispersed in situ in this novel DOS to form a suspension(MoS_(2)/C_(60)/DOS).The tribological properties of MoS_(2)/C_(60)/DOS were examined through high-frequency reciprocating friction and wear experiments,and the friction and wear mechanisms were analyzed.The results show that MoS_(2)/C_(60)/DOS can significantly enhance the antiwear and friction reduction performance compared to commercial DOS by 91% and 95%,respectively,achieving an ultra-low friction state with an average friction coefficient of 0.006.A friction film containing elements such as Fe,O,C,Mo,and S forms on the friction surface,significantly improving the lubrication state of the friction interface and achieving low friction.
基金supported by the project:“Obtención de biocombustibles y compuestos químicos de alto valor agregado a partir de biomasas de desecho ricas en pectina”,CONAHCYT agreement:CB 255527-2016the Fellowship with reference number:654271 from the Mexican Council for Science and Technology,CONAHCYT was assigned to Eva Estela Rivera Cedillo as PhD student.
文摘The transformation of biomasses from agro-industrial waste can significantly impact the production of green chemicals from sustainable resources.Pectin is a biopolymer present in lignocellulosic biomass as Orange Peel Waste(OPW)and has possibilities for making platform compounds such as furfural for sustainable chemistry.In this work,we studied the transformation to furfural of OPW,pectins,and d-galacturonic acid(D-GalA),which is the main component(65 wt%)of pectin.We analyzed pectins with different degrees of esterification(45,60 and 95 DE)in a one-pot hydrolysis reaction system and studied the differences in depolymerization and dehydration of the carbohydrates.The results show that the production of furfural decreases as the DE value increases.Specifically,low DE values favor the formation of furfural since the decarboxylation reaction is favored over deesterification.Interestingly,the furfural concentration is dependent upon the polysaccharide composition of pentoses and uronic acid.The obtained concentrations of furfural(13 and 14 mmol/L),d-xylose(6.2 and 10 mmol/L),and L-arabinose(2.5 and 2.7 mmol/L)remained the same when the galacturonic acid was fed either as a polymer or a monomer under the same reaction conditions(0.01 M SA,90 min and 433 K).OPW is proposed as a feedstock in a biorefinery,in which on a per kg OPW dry basis,90 g of pectin and 15 g of furfural were produced in the most favorable case.We conclude that the co-production of pectin and furfural from OPW is economically feasible.
基金supported by the National Natural Science Foundation of China(2123600121176056)+1 种基金the Programme for 100 Excellent Talents in Universities of Hebei Province(II)(BR2-208)the Natural Science Foundation of Hebei Province(B2015202228)~~
文摘A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4. The structure and acidity of the catalyst were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, thermogravimetric analysis, X‐ray photoelectron spectroscopy, and elemental analysis, which showed that it was an amorphous carbon material composed of aromatic carbon sheets in random orientations. Sulfonic acid groups were present on the surface at a density of 0.81 mmol/g. The carbon solid acid catalyst showed better performance than HZSM‐5 for the esterification of cyclohexene with formic acid. At a3：1 molar ratio of formic acid to cyclohexene, catalyst loading of 0.07 g/mL of cyclohexene, and reaction time of 1 h at 413 K, the cyclohexene conversion was 88.4% with 97.3% selectivity to cyclohexyl formate. The carbon solid acid catalyst showed better reusability than HZSM‐5 because its large pores were minimally affected by the accumulation of oligomerized cyclohexene, which deactivated HZSM‐5. The activity of the carbon solid acid catalyst decreased somewhat in the first two recycles due to the leaching of polycyclic aromatic hydrocarbon containing –SO3H groups and then it remained constant in the following reuse.
文摘Fhnctionalized ionic liquid samples （bmim-PW12） were synthesized by 1-butyl-3-methyl- imidazolium bromide （bmimBr） and 12-phosphotungstic heteropolyacid （PW12）. The samples were annealed at 100-450 ℃ and were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, thermal gravity-DTG, brunauer emmett teller, and NHa-temperature programmed desorption. The results showed that the bmim-PW12 samples were crystal and maintained intact Keggin structure. The organic parts of those samples were partly decomposed at a temperature more than 350 ℃. The sample annealed at 400 ℃ exhibited nano-porous structure, strong acidity, and excellent catalytic activity on the esterification of n-butanol with acetic acid. The higher ester yield was obtained when the mass ratio of catalyst over the reactants amount was 5% for bmim-PW12 catalyst annealed at 400 ℃.
文摘Esterification of carboxylic acid with equimolar amounts alcohol can be efficiently catalyzed by biphasic 4-(benzylamino)formoyldiphenylammonium triflate (BDPAT, 3) in good yield. The catalyst can be easily recovered without loss of activity.
