The increasing demand for efficient energy conversion and sustainable chemical production has driven research into advanced catalytic processes,with copper-based catalysts emerging as promising candidates due to their...The increasing demand for efficient energy conversion and sustainable chemical production has driven research into advanced catalytic processes,with copper-based catalysts emerging as promising candidates due to their cost-effectiveness and versatile redox properties.However,their practical application in electro-assisted organic reactions is often limited by challenges in achieving high selectivity and efficiency.This study introduces a novel approach that harnesses Cu^(+)-Cu^(0) defect-induced sites to enhance catalytic selectivity and efficiency in electro-assisted propylene oxidation.By inducing lattice distortions,a unique interplay between metallic and oxidized copper is achieved,improving O_(2) activation and stabilizing reactive intermediates.This dopant-controlled modification enriches the copper lattice with active sites,significantly boosting surface reactivity.Under ambient conditions,the Cu^(+)-Cu^(0) interface achieves high selectivity for propylene glycol through selective(*)^OOH formation.This work could lay the groundwork for new paradigms in catalytic design through engineered defects.展开更多
Molybdenum-based catalysts for the gas-phase oxidation of propylene with air were investigated. Various types of silica-supported molybdenum oxide and molybdenum-bismuth mixed oxide cata- lysts were prepared from inor...Molybdenum-based catalysts for the gas-phase oxidation of propylene with air were investigated. Various types of silica-supported molybdenum oxide and molybdenum-bismuth mixed oxide cata- lysts were prepared from inorganic and organometallic molybdenum precursors using wet impregnation and physical vapor deposition methods. The epoxidation activities of the prepared cata- lysts showed direct correlations with their nanostructures, which were identified using transmission electron microscopy. The appearance of a partly or fully crystalline molybdenum oxide phase, which interacted poorly with the silica support, decreased the selectivity for propylene oxide for- mation to below 10%; non-crystalline octahedrally coordinated molybdenum species anchored on the support gave propylene oxide formations greater than 55%, with 11% propylene conversion. Electrochemical characterization of molybdenum oxides with various morphologies showed the importance of structural defects. Direct promotion by bismuth of the epoxidation reactivities over molybdenum oxides is disputed.展开更多
Propylene oxide(PO),with its reactive three-membered epoxide functional group,exhibits remarkable functional versatility and serves as a crucial bridge connecting the gaps between fossil energy utilization and chemica...Propylene oxide(PO),with its reactive three-membered epoxide functional group,exhibits remarkable functional versatility and serves as a crucial bridge connecting the gaps between fossil energy utilization and chemical intermediate generation for new material innovation [1].For instance,PO's downstream derivatives,such as polyether polyols,carbonic esters,and polyurethanes,are widely utilized in wind power generation,battery electrolytes,solar cells,and CO_(2)-based degradable polymers,contributing to sustainable decarbonization in industry [2].展开更多
Propylene oxide(PO)is an important petrochemical materials used to produce downstream products such as propylene glycol(PG),polyether polyols,and dipropylene glycol(DPG).Among these,DPG is commonly used as a solvent f...Propylene oxide(PO)is an important petrochemical materials used to produce downstream products such as propylene glycol(PG),polyether polyols,and dipropylene glycol(DPG).Among these,DPG is commonly used as a solvent for fragrances,cosmetics,food additives,and detergents,and can also be served as a moisturizer in cosmetics,showing broad application prospects.The distribution of DPG isomers in the products synthesized from PO and PG has a significant impactΔrGΔrHΔfHθΔfGθPO+PG⇌DPG PO+DPG⇌TPG PG+PG⇌DPG+H_(2)O PG+DPG⇌TPG+H_(2)O on the quality of the products.Therefore,conducting thermodynamic calculation on the reaction of PO and PG to synthesize DPG can provide a theoretical basis for practical operations and product distribution regulation.So,in this paper,the thermodynamic parameters of PO,1,2-PG,H_(2)O,tripropylene glycol(TPG)and three isomers of DPG under different reaction conditions is calculated.Additionally,the,and lnK for four potential reactions at various reaction temperatures and pressures are calculated.By designing isodesmic reactions and combining the results of thermodynamic calculations,the and for the isomers of DPG are obtained,and the relative error is less than 7%.The results show that in the process of preparing DPG by PO and PG,when PO∶PG=1,the reaction temperature ranges from 298.15 to 413.15 K,and the pressure ranges from 101.325 to 506.625 kPa,the reactions of and are thermodynamically spontaneous.While the reactions of and are thermodynamically unspontaneous.The optimal reaction temperature and pressure are 413.15 K and 101.325 kPa.The thermodynamic stability of the three isomers is DPG1>DPG2>DPG3 under standard conditions.The accuracy of the computational results is verified through experimental design,and based on this,the factors affecting product distribution are analyzed.展开更多
Identification of the catalytically active sites emerges as the prerequisite for an atomic-level comprehensive understanding and further rational design of highly efficient catalysts.Here,we demonstrate a kinetics str...Identification of the catalytically active sites emerges as the prerequisite for an atomic-level comprehensive understanding and further rational design of highly efficient catalysts.Here,we demonstrate a kinetics strategy to identify the active sites of Au catalyst for the disentanglement of geometric and electronic effects on the selective oxidation of propylene to acrolein.Both the Ti-containing titanium-silicalite-1(TS-1)and Ti-free silicalite-1(S-1)were employed as supports to immobilize Au catalysts,which were investigated by a combination of multiple characterization,kinetics analysis,crystal structure modelling.The Au(111)sites are identified as the main active site for acrolein formation,while their electronic effects are highly relevant to the presence or absence of Ti.Moreover,propylene epoxide(PO)formation mainly involves the co-participation of Au and Ti sites,the proximity between Au and Ti sites is found to have less influences on PO formation in a certain distance.In comparison,acrolein is very likely to generate over Au(111)sites via the hydrogen-assisted O_(2) activation to oxygenated species for its oxidizing propylene.The insights gained here could guide the design and preparation of Au catalysts for selective propylene oxidation.展开更多
The unsupported Cu and Ag catalysts with different oxidation states were prepared, and their catalytic performances for propylene epoxidation were investigated.The metallic Cu catalyst exhibits much higher catalytic a...The unsupported Cu and Ag catalysts with different oxidation states were prepared, and their catalytic performances for propylene epoxidation were investigated.The metallic Cu catalyst exhibits much higher catalytic activity and propylene oxide(PO) selectivity than Cu2 O and Cu O catalysts.The Cu0 species are the main active sites for propylene epoxidation, but Cu2 O and Cu O species are in favor of CO2 and acrolein production.The PO selectivity of 54.2 % and propylene conversion of 2.6 % can be achieved over the metallic Cu catalyst at 160 °C in initial stage, but metallic Cu catalyst would be oxidized to Cu2 O during propylene epoxidation, resulting in a sharp decrease in the PO selectivity and propylene conversion.Nanosize Ag Cuxbimetallic catalysts were prepared.It is found that adding Ag to the metallic Cu catalysts can prevent the oxidation of Cu and make Ag Cuxbimetallic catalysts more stable under the condition of propylene epoxidation.The Ag/Cu molar ratio can remarkably affect the catalytic performance of Ag Cuxcatalyst and the selectivity to PO and acrolein.After Ag Cuxwas supported on MOx-modified a-Al2O3, its catalytic performance can be improved and has a close relationship with the acid–base property of support.展开更多
Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized b...Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy and O2 temperatureprogrammed desorption. Ag‐Cu‐Cl/BaCO3 catalyst with 0.036 wt% Cu and 0.060 wt% Cl exhibitedthe highest catalytic performance for gas‐phase epoxidation of propylene by molecular oxygen. Apropylene oxide selectivity of 83.7% and propylene conversion of 1.2% were achieved under thereaction conditions of 20% C3H6‐10% O2‐70% N2, 200 °C, 0.1 MPa and 3000 h?1. Increasing the Clloading allowed Ag to ensemble easier, whereas changing the Cu loading showed little effect on Agcrystallite size. The appropriate Cl loading of Ag‐Cu‐Cl/BaCO3 catalyst can reduce the dissociationadsorption of oxygen to atomic oxygen species leading to the combustion of propylene to CO2, whichbenefits epoxidation of propylene by molecular oxygen. Excessive Cl loading of Ag‐Cu‐Cl/BaCO3catalyst decreases propylene conversion and propylene oxide selectivity remarkably because of Clpoisoning. The appropriate Cu loading of Ag‐Cu‐Cl/BaCO3 catalyst is efficient for the epoxidation ofpropylene by molecular oxygen, and an excess Cu loading decreases propylene oxide selectivitybecause the aggregation of Cu species increases the exposed surfaces of Ag nanoparticles, whichwas shown by slight increases in atomic oxygen species adsorbed. The appropriate loadings of Cu and Cl of Ag‐Cu‐Cl/BaCO3 catalyst are important to strike the balance between molecular oxygen and atomic oxygen species to create a favorable epoxidation of propylene by molecular oxygen.展开更多
Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation.Nevertheless,the elucidation of the structure-performance relationships for the...Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation.Nevertheless,the elucidation of the structure-performance relationships for these systems remains a scientific challenge.In this work,copper oxide clusters deposited on a high-surface-area silica support were synthesized via a deposition-precipitation approach and exhibited remarkable catalytic reactivity(up to 25.5%conversion and 66.8%selectivity)in the propylene-selective oxidation of acrolein at 300℃.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy combined with X-ray absorption fine structure measurements of the catalyst before and after the reaction confirmed the transformation of the small-sized copper oxide(CuO)clusters into cuprous oxide(Cu2O)clusters.With the aid of in situ X-ray diffraction and in situ dual beam Fourier transform infrared spectroscopy(DB-FTIR),the allyl intermediate(CH2=CHCH2*)was clearly observed,along with the as-formed Cu2O species.The intermediate can react with oxygen atoms from neighboring Cu2O species to form acrolein during the catalytic process,and the small-sized Cu2O clusters play a crucial role in the generation of acrolein via the selective oxidation of propylene.展开更多
Selective propylene epoxidation to propylene oxide(PO) with hydrogen peroxide(H_2O_2) was carried out in a catalytic semi-batch reactor.High propylene epoxidation activity(44 h^(-1)) was observed over Nb based mesopor...Selective propylene epoxidation to propylene oxide(PO) with hydrogen peroxide(H_2O_2) was carried out in a catalytic semi-batch reactor.High propylene epoxidation activity(44 h^(-1)) was observed over Nb based mesoporous silicate materials Nb-TUD-1 under mild operating conditions.The physical and chemical properties of the Nb based silicates characterized using BET,FTIR,TPD,TEM and UV–Vis revealed that the site isolation and surface acidity are crucial for PO production.Catalyst synthesis methods were investigated for their effects on PO productivity,PO selectivity and H_2O_2 utilization efficiency.It is found that Nb-TUD-1 material synthesized by the sol–gel method is more active and selective than impregnated materials for liquid phase propylene epoxidation.Surface characterization confirms that thus synthesized Nb-TUD-1 catalysts have more Lewis acidity and less Bronsted acidity compared to the catalysts by impregnation.展开更多
The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Ti^n＋...The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Ti^n＋ site on the surface of the catalyst and that the adisorbing capacity of the catalyst for propylene oxide is larger than that for propylene. Catalytic behavior for propylene epoxidation with H2 and O2 was tested in a micro-reactor. Under typical conditions, the selectivity for propylene oxide is over 87%. The TG curves show that PO successive oxidation cause carbon deposition on the active center and deactivation of the Au catalysts. Because the amounts of Tin＋ site decrease significantly, and consequently the separation between Ti^n＋ sites increases, the Au/TiO2-SiO2 catalyst is more stable than Au/TiO2.展开更多
XPS and chemical trapping experments with H2, NH3, and CH3I as trapping agents were carried out for studying the adsorption of propylene over MoO3 or r-Bi2MoO6. The results show that the fragmentation of carbon chain ...XPS and chemical trapping experments with H2, NH3, and CH3I as trapping agents were carried out for studying the adsorption of propylene over MoO3 or r-Bi2MoO6. The results show that the fragmentation of carbon chain takes place during the adsorption of propylene through breaking C -C double bond and C-C bond on Mo2+ and the adjacent lattice oxygen, leading to formation of the oxygen- or nitrogen-containing by-products of C1 and C2 species. Diffuse-Reflection Fourier Transform Infrared (DRFTIR) Spectroscopy was used to study the surface species formed during the chemisorption and reaction of propylene over y-Bi2MoO6 at a lower temperature. The results that C1, C2 adspecies were detected by DRFTIR at 175℃ are consistent with the results of XPS and chemical trapping experiments, whlle the results at 50℃ Grasselli et al.展开更多
A random walk Monte Carlo （RWMC） simulation model of catalytic particle was established on the basis of the structures of bismuth molybdate catalysts and mechanisms of catalytic reactions with propylene selective ox...A random walk Monte Carlo （RWMC） simulation model of catalytic particle was established on the basis of the structures of bismuth molybdate catalysts and mechanisms of catalytic reactions with propylene selective oxidation and ammoxidation. The simulation results show that rationality of the RWMC model is proved on the basis of pulse experimental data. One of the most remarkable factors affecting catalytic behavior is the transfer of bulk lattice oxygen, which decides the rate of ammonia-consuming and propylene-consuming. The selectivity of main products reaches the maximum after the reduction of catalysts to a certain degree. It is inferred that catalytic performance improves greatly if the ratio of capacity for dehydrogenation from adsorbed propylene molecule on catalytically active site of molybdenum metal-imido group （Mo=NH） to that on catalytically active site of molybdenum metal-oxo group （Mo=O） becomes much higher.展开更多
Aluminum porphyrin complexes are heavy-metal-free and soil-tolerant green catalysts for the copolymerization of CO2 and propylene oxide（PO）, but they suffer from relatively poor poly（propylene carbonate）（PPC） se...Aluminum porphyrin complexes are heavy-metal-free and soil-tolerant green catalysts for the copolymerization of CO2 and propylene oxide（PO）, but they suffer from relatively poor poly（propylene carbonate）（PPC） selectivity. Herein, steric hindrance porphyrin ligand was used to enhance the PPC selectivity. Typically, a bulky anthracene-like group was incorporated into the porphyrin ring to form 5,10,15,20-tetra（1,2,3,4,5,6,7,8-octahydro-1,4：5,8-dimethanoanthracen-9-yl）porphyrin, the aluminum porphyrin complex with this ligand, in combination with bis（triphenylphosphine）iminium chloride as a co-catalyst, produced completely alternate PPC. Additionally, the obtained PPC showed high regioselectivity, with a head-to-tail linkage content（HT） of 92%. Therefore, we demonstrated that introduction of bulky steric ligand into the porphyrin ring could reduce the propylene oxide homopolymerization activity leading to excellent PPC selectivity, and improve regioselectivity for the PO ring-opening during the copolymerization.展开更多
A series of acetate ionic liquids were synthesized using a typical two‐step method.The ionic liquids were used as environmentally benign catalysts in the production of propylene glycol ethers from propylene oxide and...A series of acetate ionic liquids were synthesized using a typical two‐step method.The ionic liquids were used as environmentally benign catalysts in the production of propylene glycol ethers from propylene oxide and alcohols under mild conditions.The basic strengths of the ionic liquids were evaluated by determination of their Hammett functions,obtained using ultraviolet‐visible spectroscopy,and the relationship between their catalytic activities and basicities was established.The catalytic efficiencies of the ionic liquids were higher than that of the traditional basic catalyst NaOH.This can be attributed to the involvement of a novel reaction mechanism when these ionic liquids are used.A possible electrophilic‐nucleophilic dual activation mechanism was proposed and confirmed using electrospray ionization quadrupole time‐of‐flight mass spectrometry.In addition,the effects of significant reaction parameters such as concentration of catalyst,molar ratio of alcohol to propylene oxide,reaction temperature,and steric hindrance of the alcohol were investigated in detail.展开更多
Using supported multi-componem zinc dicarboxylate catalyst, poly（1,2-propylene carbonate-co-1,2-cyclohexylene carbonate） （PPCHC） was successfully synthesized from carbon dioxide （CO2） with propylene oxide （PO）...Using supported multi-componem zinc dicarboxylate catalyst, poly（1,2-propylene carbonate-co-1,2-cyclohexylene carbonate） （PPCHC） was successfully synthesized from carbon dioxide （CO2） with propylene oxide （PO） and cyclohexene oxide （CHO）. The conversion of epoxides dramatically increased up to 89.7% （yield： 384.2 g of polymer per g of Zn） with increasing reaction temperature from 60℃ to 80℃. The optimized reaction temperature is 80℃. The chemical structure, the molecular weight, as well as thermal and mechanical properties of the resulting terpolymers were investigated extensively. When CHO feed content （mol%） is lower than 10%, the PPCHC terpolymers have number average molecular weight （Ma） ranging from 102 × 10^3 to 202 × 10^3 and molecular weight distribution （MWD） values ranging from 2.8 to 3.5. In contrast to poly（propylene carbonate） （PPC）, the introduction of small amount of CHO leads to increase in the glass transition temperature from 38.0℃ to 42.6℃. Similarly, the mechanical strength of the synthesized terpolymer is greatly enhanced due to the incorporation of CHO. These improvements in mechanical and thermal properties are of importance for the practical application of PPC.展开更多
Rare-earth ternary catalysts Y(CCl3COO)3-ZnR2-glycerin were prepared for the copolymerization of carbon dioxide and propylene oxide(PO),where dialkylzincs(ZnR2)were diethylzinc,di(n-propyl)zinc,di(n-butyl)zinc,di(i-pr...Rare-earth ternary catalysts Y(CCl3COO)3-ZnR2-glycerin were prepared for the copolymerization of carbon dioxide and propylene oxide(PO),where dialkylzincs(ZnR2)were diethylzinc,di(n-propyl)zinc,di(n-butyl)zinc,di(i-propyl)zinc,di(i-butyl)zinc,di(s-butyl)zinc,respectively.The Y(CCl3COO)3-ZnR2-glycerin catalysts displayed the highest catalytic activity at the molar ratio of Y(CCl3COO)3:ZnR2:glycerin=1:20:10.In the same copolymerization condition,catalysts containing dialkylzincs with branched alkyl group showed lower catalytic activity than that with primary alkyl group.For those catalysts including dialkylzincs with primary alkyl group,their catalytic activity decreases with increasing number of carbon atom in the alkyl group with the following sequence:Y(CCl3COO)3-ZnEt2-glycerin〉Y(CCl3COO)3-Zn(n-Pr)2-glycerin〉Y(CCl3COO)3-Zn(n-Bu)2-glycerin.However,the alkyl group in the dialkylzinc does not influence the insertion of PO into the propagation chain end.展开更多
A novel copolymer of polyaniline-poly(propylene oxide) (PAN-PPO) was prepared by cyclic voltammetry (CV) and characterized by FTIR and SEM. It showed good electroactivity for methanol oxidation in H2SO4 solution.
The electrocatalytic synthesis of propylene carbonate（PC） from CO2 and propylene oxide（PO） was studied under mild conditions（PCO2=1.01×105 Pa, t=25 ℃）. Influences of solvents, supporting electrolytes, the ...The electrocatalytic synthesis of propylene carbonate（PC） from CO2 and propylene oxide（PO） was studied under mild conditions（PCO2=1.01×105 Pa, t=25 ℃）. Influences of solvents, supporting electrolytes, the passed charge, the nature of electrodes and the current density（j） on the yield of PC were investigated to optimize the electrolytic conditions, with the maximal yield to be 46.2%, the selectivity of propylene carbonate is 100%. The reduction of propylene oxide in the absence and presence of CO2 was examined by cyclic voltammetry. The mechanism of the reaction initiated by the synergistic effect of halides ions of supporting electrolytes with nucleophilicity and the metal ions from scarification anode with Lewis acid acidity was proposed on the basis of our results.展开更多
Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by C-13-NMR and IR spectra. H...Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by C-13-NMR and IR spectra. H-1-NMR analysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecular weight copolymers with various EO content were obtained and their values of molecular weight distribution (MWD) fell in the range of 1.21-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio of EO+PO to initiator moles used, The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.展开更多
It is difficult to separate the methanol and hydrocarbons in the propylene oxide(PO)purification process due to their forming azeotrope.As for this,a novel PO separation process,in that the deionized water is employed...It is difficult to separate the methanol and hydrocarbons in the propylene oxide(PO)purification process due to their forming azeotrope.As for this,a novel PO separation process,in that the deionized water is employed as extractant and 1,2-propylene glycol(MPG)that is formed from the PO hydrolysis reaction is recovered,is presented in this work.The salient feature of this process is that both the non-catalyzed reactions of PO hydrolysis to form MPG and dipropylene glycol(DPG)are simultaneously considered and MPG by-product with high purity is obtained in virtue of the deionized water as reflux liquid and side take-off in MPG column.In addition,the ionic liquid(IL)extractant is screened through the conductorlike screening model for segment activity coefficient(COSMO-SAC)and the comparisons of separation efficiency between the IL and normal octane(nC_(8))extractant for the separation of PO and 2-methylpentane are made.With the non-random two-liquid(NRTL)thermodynamic model,the simulation and optimization design for the full flow sheet are performed and the effects of the key operation parameters such as solvent ratio,theoretical stages,feeding stage etc.on separation efficiency are detailedly discussed.The results show that the mass purity and the mass yield of PO can be up to 99.99%and 99.0%,and the condenser duty,reboiler duty and PO loss in the process with IL extractant can be decreased by 69.66%,30.21%and 78.86%compared to ones with nC_(8).The total annual cost(TAC)calculation also suggests that the TAC would be significantly reduced if using IL in replace of nC_(8) for the investigated process.The presented results would provide a useful guide for improving the quality of PO product and the economic efficiency of industrial plant.展开更多
基金supported by financial aid from the National Key Research and Development Project of China(2022YFC2905201)the National Natural Science Foundation of China(92262301)+2 种基金financial aid from the Science and Technology Agency of Henan Province(222102240120)the Key Research and Development Project of Jiangxi Province(20243BBG71021)the Pioneer Talent Recruitment Program(Category B),Chinese Academy of Sciences(E425C002)。
文摘The increasing demand for efficient energy conversion and sustainable chemical production has driven research into advanced catalytic processes,with copper-based catalysts emerging as promising candidates due to their cost-effectiveness and versatile redox properties.However,their practical application in electro-assisted organic reactions is often limited by challenges in achieving high selectivity and efficiency.This study introduces a novel approach that harnesses Cu^(+)-Cu^(0) defect-induced sites to enhance catalytic selectivity and efficiency in electro-assisted propylene oxidation.By inducing lattice distortions,a unique interplay between metallic and oxidized copper is achieved,improving O_(2) activation and stabilizing reactive intermediates.This dopant-controlled modification enriches the copper lattice with active sites,significantly boosting surface reactivity.Under ambient conditions,the Cu^(+)-Cu^(0) interface achieves high selectivity for propylene glycol through selective(*)^OOH formation.This work could lay the groundwork for new paradigms in catalytic design through engineered defects.
基金A support by VEGA grant 2/0129/13 is acknowledged by I.V.
文摘Molybdenum-based catalysts for the gas-phase oxidation of propylene with air were investigated. Various types of silica-supported molybdenum oxide and molybdenum-bismuth mixed oxide cata- lysts were prepared from inorganic and organometallic molybdenum precursors using wet impregnation and physical vapor deposition methods. The epoxidation activities of the prepared cata- lysts showed direct correlations with their nanostructures, which were identified using transmission electron microscopy. The appearance of a partly or fully crystalline molybdenum oxide phase, which interacted poorly with the silica support, decreased the selectivity for propylene oxide for- mation to below 10%; non-crystalline octahedrally coordinated molybdenum species anchored on the support gave propylene oxide formations greater than 55%, with 11% propylene conversion. Electrochemical characterization of molybdenum oxides with various morphologies showed the importance of structural defects. Direct promotion by bismuth of the epoxidation reactivities over molybdenum oxides is disputed.
基金supported by the National Natural Science Foundation of China (29792072, 22278441, 22478452)National Key Research and Development Program of China (937) (2006CB202508)the SINOPEC Project (419019-2, 413108)。
文摘Propylene oxide(PO),with its reactive three-membered epoxide functional group,exhibits remarkable functional versatility and serves as a crucial bridge connecting the gaps between fossil energy utilization and chemical intermediate generation for new material innovation [1].For instance,PO's downstream derivatives,such as polyether polyols,carbonic esters,and polyurethanes,are widely utilized in wind power generation,battery electrolytes,solar cells,and CO_(2)-based degradable polymers,contributing to sustainable decarbonization in industry [2].
基金Supported by the Natural Science Foundation of Shanxi Province(202203021221303)the Science and Technology Major Project of Shanxi Province(202005D121002)the Science and Technology Cooperation and Communication Project of Shanxi Province(202304041101016)。
文摘Propylene oxide(PO)is an important petrochemical materials used to produce downstream products such as propylene glycol(PG),polyether polyols,and dipropylene glycol(DPG).Among these,DPG is commonly used as a solvent for fragrances,cosmetics,food additives,and detergents,and can also be served as a moisturizer in cosmetics,showing broad application prospects.The distribution of DPG isomers in the products synthesized from PO and PG has a significant impactΔrGΔrHΔfHθΔfGθPO+PG⇌DPG PO+DPG⇌TPG PG+PG⇌DPG+H_(2)O PG+DPG⇌TPG+H_(2)O on the quality of the products.Therefore,conducting thermodynamic calculation on the reaction of PO and PG to synthesize DPG can provide a theoretical basis for practical operations and product distribution regulation.So,in this paper,the thermodynamic parameters of PO,1,2-PG,H_(2)O,tripropylene glycol(TPG)and three isomers of DPG under different reaction conditions is calculated.Additionally,the,and lnK for four potential reactions at various reaction temperatures and pressures are calculated.By designing isodesmic reactions and combining the results of thermodynamic calculations,the and for the isomers of DPG are obtained,and the relative error is less than 7%.The results show that in the process of preparing DPG by PO and PG,when PO∶PG=1,the reaction temperature ranges from 298.15 to 413.15 K,and the pressure ranges from 101.325 to 506.625 kPa,the reactions of and are thermodynamically spontaneous.While the reactions of and are thermodynamically unspontaneous.The optimal reaction temperature and pressure are 413.15 K and 101.325 kPa.The thermodynamic stability of the three isomers is DPG1>DPG2>DPG3 under standard conditions.The accuracy of the computational results is verified through experimental design,and based on this,the factors affecting product distribution are analyzed.
基金the National Key R&D Program of China(No.2021YFA1501403)the National Natural Science Foundation of China(Nos.21922803,22038003,92034301,22008066,and 21776077)+3 种基金the Innovation Program of Shanghai Municipal Education Commission,the Program of Shanghai Academic/Technology Research Leader(No.21XD1421000)the Shanghai Science and Technology Innovation Action Plan(No.22JC1403800)the China Postdoctoral Science Foundation(No.BX20190116)111 Project of the Ministry of Education of China(No.B08021).
文摘Identification of the catalytically active sites emerges as the prerequisite for an atomic-level comprehensive understanding and further rational design of highly efficient catalysts.Here,we demonstrate a kinetics strategy to identify the active sites of Au catalyst for the disentanglement of geometric and electronic effects on the selective oxidation of propylene to acrolein.Both the Ti-containing titanium-silicalite-1(TS-1)and Ti-free silicalite-1(S-1)were employed as supports to immobilize Au catalysts,which were investigated by a combination of multiple characterization,kinetics analysis,crystal structure modelling.The Au(111)sites are identified as the main active site for acrolein formation,while their electronic effects are highly relevant to the presence or absence of Ti.Moreover,propylene epoxide(PO)formation mainly involves the co-participation of Au and Ti sites,the proximity between Au and Ti sites is found to have less influences on PO formation in a certain distance.In comparison,acrolein is very likely to generate over Au(111)sites via the hydrogen-assisted O_(2) activation to oxygenated species for its oxidizing propylene.The insights gained here could guide the design and preparation of Au catalysts for selective propylene oxidation.
基金financially supported by the National Basic Research Program of China (No. 2010CB732300)
文摘The unsupported Cu and Ag catalysts with different oxidation states were prepared, and their catalytic performances for propylene epoxidation were investigated.The metallic Cu catalyst exhibits much higher catalytic activity and propylene oxide(PO) selectivity than Cu2 O and Cu O catalysts.The Cu0 species are the main active sites for propylene epoxidation, but Cu2 O and Cu O species are in favor of CO2 and acrolein production.The PO selectivity of 54.2 % and propylene conversion of 2.6 % can be achieved over the metallic Cu catalyst at 160 °C in initial stage, but metallic Cu catalyst would be oxidized to Cu2 O during propylene epoxidation, resulting in a sharp decrease in the PO selectivity and propylene conversion.Nanosize Ag Cuxbimetallic catalysts were prepared.It is found that adding Ag to the metallic Cu catalysts can prevent the oxidation of Cu and make Ag Cuxbimetallic catalysts more stable under the condition of propylene epoxidation.The Ag/Cu molar ratio can remarkably affect the catalytic performance of Ag Cuxcatalyst and the selectivity to PO and acrolein.After Ag Cuxwas supported on MOx-modified a-Al2O3, its catalytic performance can be improved and has a close relationship with the acid–base property of support.
基金supported by National Basic Research Program of China (2013CB933200)Commission of Science and Technology of Shanghai Municipality (15DZ1205305)~~
文摘Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy and O2 temperatureprogrammed desorption. Ag‐Cu‐Cl/BaCO3 catalyst with 0.036 wt% Cu and 0.060 wt% Cl exhibitedthe highest catalytic performance for gas‐phase epoxidation of propylene by molecular oxygen. Apropylene oxide selectivity of 83.7% and propylene conversion of 1.2% were achieved under thereaction conditions of 20% C3H6‐10% O2‐70% N2, 200 °C, 0.1 MPa and 3000 h?1. Increasing the Clloading allowed Ag to ensemble easier, whereas changing the Cu loading showed little effect on Agcrystallite size. The appropriate Cl loading of Ag‐Cu‐Cl/BaCO3 catalyst can reduce the dissociationadsorption of oxygen to atomic oxygen species leading to the combustion of propylene to CO2, whichbenefits epoxidation of propylene by molecular oxygen. Excessive Cl loading of Ag‐Cu‐Cl/BaCO3catalyst decreases propylene conversion and propylene oxide selectivity remarkably because of Clpoisoning. The appropriate Cu loading of Ag‐Cu‐Cl/BaCO3 catalyst is efficient for the epoxidation ofpropylene by molecular oxygen, and an excess Cu loading decreases propylene oxide selectivitybecause the aggregation of Cu species increases the exposed surfaces of Ag nanoparticles, whichwas shown by slight increases in atomic oxygen species adsorbed. The appropriate loadings of Cu and Cl of Ag‐Cu‐Cl/BaCO3 catalyst are important to strike the balance between molecular oxygen and atomic oxygen species to create a favorable epoxidation of propylene by molecular oxygen.
文摘Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation.Nevertheless,the elucidation of the structure-performance relationships for these systems remains a scientific challenge.In this work,copper oxide clusters deposited on a high-surface-area silica support were synthesized via a deposition-precipitation approach and exhibited remarkable catalytic reactivity(up to 25.5%conversion and 66.8%selectivity)in the propylene-selective oxidation of acrolein at 300℃.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy combined with X-ray absorption fine structure measurements of the catalyst before and after the reaction confirmed the transformation of the small-sized copper oxide(CuO)clusters into cuprous oxide(Cu2O)clusters.With the aid of in situ X-ray diffraction and in situ dual beam Fourier transform infrared spectroscopy(DB-FTIR),the allyl intermediate(CH2=CHCH2*)was clearly observed,along with the as-formed Cu2O species.The intermediate can react with oxygen atoms from neighboring Cu2O species to form acrolein during the catalytic process,and the small-sized Cu2O clusters play a crucial role in the generation of acrolein via the selective oxidation of propylene.
基金Supported by the China Postdoctoral Science Foundation(2017 M612374)the Natural Science Foundation of Shandong Province(ZR2017BB007)+5 种基金the Postdoctoral Research Funding of Shandong Province(201703016)the Qingdao Postdoctoral Research Funding(BY20170210)the Fundamental Research Funding of Qingdao(17-1-1-67-jch,17-1-1-80-jch)the Fundamental Research Funds for the Central Universities(18CX02145A,17CX02017A)the New Faculty Start-up Funding from China University of Petroleum(YJ201601058)the Natural Science Foundation of China(21606254)
文摘Selective propylene epoxidation to propylene oxide(PO) with hydrogen peroxide(H_2O_2) was carried out in a catalytic semi-batch reactor.High propylene epoxidation activity(44 h^(-1)) was observed over Nb based mesoporous silicate materials Nb-TUD-1 under mild operating conditions.The physical and chemical properties of the Nb based silicates characterized using BET,FTIR,TPD,TEM and UV–Vis revealed that the site isolation and surface acidity are crucial for PO production.Catalyst synthesis methods were investigated for their effects on PO productivity,PO selectivity and H_2O_2 utilization efficiency.It is found that Nb-TUD-1 material synthesized by the sol–gel method is more active and selective than impregnated materials for liquid phase propylene epoxidation.Surface characterization confirms that thus synthesized Nb-TUD-1 catalysts have more Lewis acidity and less Bronsted acidity compared to the catalysts by impregnation.
基金Supported by the National Natural Science Foundation of China (29773031).
文摘The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Ti^n＋ site on the surface of the catalyst and that the adisorbing capacity of the catalyst for propylene oxide is larger than that for propylene. Catalytic behavior for propylene epoxidation with H2 and O2 was tested in a micro-reactor. Under typical conditions, the selectivity for propylene oxide is over 87%. The TG curves show that PO successive oxidation cause carbon deposition on the active center and deactivation of the Au catalysts. Because the amounts of Tin＋ site decrease significantly, and consequently the separation between Ti^n＋ sites increases, the Au/TiO2-SiO2 catalyst is more stable than Au/TiO2.
基金Supported by the National Natural Science Fundation of China.
文摘XPS and chemical trapping experments with H2, NH3, and CH3I as trapping agents were carried out for studying the adsorption of propylene over MoO3 or r-Bi2MoO6. The results show that the fragmentation of carbon chain takes place during the adsorption of propylene through breaking C -C double bond and C-C bond on Mo2+ and the adjacent lattice oxygen, leading to formation of the oxygen- or nitrogen-containing by-products of C1 and C2 species. Diffuse-Reflection Fourier Transform Infrared (DRFTIR) Spectroscopy was used to study the surface species formed during the chemisorption and reaction of propylene over y-Bi2MoO6 at a lower temperature. The results that C1, C2 adspecies were detected by DRFTIR at 175℃ are consistent with the results of XPS and chemical trapping experiments, whlle the results at 50℃ Grasselli et al.
基金国家自然科学基金，the Fundamental Research Foundation of SINOPEC
文摘A random walk Monte Carlo （RWMC） simulation model of catalytic particle was established on the basis of the structures of bismuth molybdate catalysts and mechanisms of catalytic reactions with propylene selective oxidation and ammoxidation. The simulation results show that rationality of the RWMC model is proved on the basis of pulse experimental data. One of the most remarkable factors affecting catalytic behavior is the transfer of bulk lattice oxygen, which decides the rate of ammonia-consuming and propylene-consuming. The selectivity of main products reaches the maximum after the reduction of catalysts to a certain degree. It is inferred that catalytic performance improves greatly if the ratio of capacity for dehydrogenation from adsorbed propylene molecule on catalytically active site of molybdenum metal-imido group （Mo=NH） to that on catalytically active site of molybdenum metal-oxo group （Mo=O） becomes much higher.
基金financially supported by the National Natural Science Foundation of China(No.51673193)Key Project for Frontier Research(2016)Youth Innovation Promotion Association Chinese Academy of Sciences
文摘Aluminum porphyrin complexes are heavy-metal-free and soil-tolerant green catalysts for the copolymerization of CO2 and propylene oxide（PO）, but they suffer from relatively poor poly（propylene carbonate）（PPC） selectivity. Herein, steric hindrance porphyrin ligand was used to enhance the PPC selectivity. Typically, a bulky anthracene-like group was incorporated into the porphyrin ring to form 5,10,15,20-tetra（1,2,3,4,5,6,7,8-octahydro-1,4：5,8-dimethanoanthracen-9-yl）porphyrin, the aluminum porphyrin complex with this ligand, in combination with bis（triphenylphosphine）iminium chloride as a co-catalyst, produced completely alternate PPC. Additionally, the obtained PPC showed high regioselectivity, with a head-to-tail linkage content（HT） of 92%. Therefore, we demonstrated that introduction of bulky steric ligand into the porphyrin ring could reduce the propylene oxide homopolymerization activity leading to excellent PPC selectivity, and improve regioselectivity for the PO ring-opening during the copolymerization.
基金supported by the One Hundred Talent Program of CASthe National Natural Science Foundation of China Petroleum & Chemical Corporation Joint Fund(U1662129)+1 种基金the National Natural Science Foundation of China(91434203)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(QYZDY-SSW-JSC011)~~
文摘A series of acetate ionic liquids were synthesized using a typical two‐step method.The ionic liquids were used as environmentally benign catalysts in the production of propylene glycol ethers from propylene oxide and alcohols under mild conditions.The basic strengths of the ionic liquids were evaluated by determination of their Hammett functions,obtained using ultraviolet‐visible spectroscopy,and the relationship between their catalytic activities and basicities was established.The catalytic efficiencies of the ionic liquids were higher than that of the traditional basic catalyst NaOH.This can be attributed to the involvement of a novel reaction mechanism when these ionic liquids are used.A possible electrophilic‐nucleophilic dual activation mechanism was proposed and confirmed using electrospray ionization quadrupole time‐of‐flight mass spectrometry.In addition,the effects of significant reaction parameters such as concentration of catalyst,molar ratio of alcohol to propylene oxide,reaction temperature,and steric hindrance of the alcohol were investigated in detail.
基金financially supported by the China High-Tech Development 863 Key Program(No.2010AA0349)Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme(2010)+1 种基金Guangdong Province Sci.&Tech.Bureau(Key Strategic Project Grant No.2008A080800024)Guangdong Education Bureau(Key Project) and Chinese Universities Basic Research Founding
文摘Using supported multi-componem zinc dicarboxylate catalyst, poly（1,2-propylene carbonate-co-1,2-cyclohexylene carbonate） （PPCHC） was successfully synthesized from carbon dioxide （CO2） with propylene oxide （PO） and cyclohexene oxide （CHO）. The conversion of epoxides dramatically increased up to 89.7% （yield： 384.2 g of polymer per g of Zn） with increasing reaction temperature from 60℃ to 80℃. The optimized reaction temperature is 80℃. The chemical structure, the molecular weight, as well as thermal and mechanical properties of the resulting terpolymers were investigated extensively. When CHO feed content （mol%） is lower than 10%, the PPCHC terpolymers have number average molecular weight （Ma） ranging from 102 × 10^3 to 202 × 10^3 and molecular weight distribution （MWD） values ranging from 2.8 to 3.5. In contrast to poly（propylene carbonate） （PPC）, the introduction of small amount of CHO leads to increase in the glass transition temperature from 38.0℃ to 42.6℃. Similarly, the mechanical strength of the synthesized terpolymer is greatly enhanced due to the incorporation of CHO. These improvements in mechanical and thermal properties are of importance for the practical application of PPC.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.20025414 and 50003009).
文摘Rare-earth ternary catalysts Y(CCl3COO)3-ZnR2-glycerin were prepared for the copolymerization of carbon dioxide and propylene oxide(PO),where dialkylzincs(ZnR2)were diethylzinc,di(n-propyl)zinc,di(n-butyl)zinc,di(i-propyl)zinc,di(i-butyl)zinc,di(s-butyl)zinc,respectively.The Y(CCl3COO)3-ZnR2-glycerin catalysts displayed the highest catalytic activity at the molar ratio of Y(CCl3COO)3:ZnR2:glycerin=1:20:10.In the same copolymerization condition,catalysts containing dialkylzincs with branched alkyl group showed lower catalytic activity than that with primary alkyl group.For those catalysts including dialkylzincs with primary alkyl group,their catalytic activity decreases with increasing number of carbon atom in the alkyl group with the following sequence:Y(CCl3COO)3-ZnEt2-glycerin〉Y(CCl3COO)3-Zn(n-Pr)2-glycerin〉Y(CCl3COO)3-Zn(n-Bu)2-glycerin.However,the alkyl group in the dialkylzinc does not influence the insertion of PO into the propagation chain end.
文摘A novel copolymer of polyaniline-poly(propylene oxide) (PAN-PPO) was prepared by cyclic voltammetry (CV) and characterized by FTIR and SEM. It showed good electroactivity for methanol oxidation in H2SO4 solution.
基金Supported by the National Natural Science Foundation of China(No.20973065)the Fund of Basic Research in Natural Science Issued by Shanghai Municipal Committee of Science+4 种基金 China(No.08dj1400100)the Shanghai Leading Project China (No.B409)the Foundation of Outstanding Young Talent in University of Anhui Province China No.2010SQRL042)
文摘The electrocatalytic synthesis of propylene carbonate（PC） from CO2 and propylene oxide（PO） was studied under mild conditions（PCO2=1.01×105 Pa, t=25 ℃）. Influences of solvents, supporting electrolytes, the passed charge, the nature of electrodes and the current density（j） on the yield of PC were investigated to optimize the electrolytic conditions, with the maximal yield to be 46.2%, the selectivity of propylene carbonate is 100%. The reduction of propylene oxide in the absence and presence of CO2 was examined by cyclic voltammetry. The mechanism of the reaction initiated by the synergistic effect of halides ions of supporting electrolytes with nucleophilicity and the metal ions from scarification anode with Lewis acid acidity was proposed on the basis of our results.
文摘Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by C-13-NMR and IR spectra. H-1-NMR analysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecular weight copolymers with various EO content were obtained and their values of molecular weight distribution (MWD) fell in the range of 1.21-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio of EO+PO to initiator moles used, The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.
基金provided by the National Key Research and Devolopment Program of China(2017YFB0702800)the National Natural Science Foundation of China (21878025, 22078026)。
文摘It is difficult to separate the methanol and hydrocarbons in the propylene oxide(PO)purification process due to their forming azeotrope.As for this,a novel PO separation process,in that the deionized water is employed as extractant and 1,2-propylene glycol(MPG)that is formed from the PO hydrolysis reaction is recovered,is presented in this work.The salient feature of this process is that both the non-catalyzed reactions of PO hydrolysis to form MPG and dipropylene glycol(DPG)are simultaneously considered and MPG by-product with high purity is obtained in virtue of the deionized water as reflux liquid and side take-off in MPG column.In addition,the ionic liquid(IL)extractant is screened through the conductorlike screening model for segment activity coefficient(COSMO-SAC)and the comparisons of separation efficiency between the IL and normal octane(nC_(8))extractant for the separation of PO and 2-methylpentane are made.With the non-random two-liquid(NRTL)thermodynamic model,the simulation and optimization design for the full flow sheet are performed and the effects of the key operation parameters such as solvent ratio,theoretical stages,feeding stage etc.on separation efficiency are detailedly discussed.The results show that the mass purity and the mass yield of PO can be up to 99.99%and 99.0%,and the condenser duty,reboiler duty and PO loss in the process with IL extractant can be decreased by 69.66%,30.21%and 78.86%compared to ones with nC_(8).The total annual cost(TAC)calculation also suggests that the TAC would be significantly reduced if using IL in replace of nC_(8) for the investigated process.The presented results would provide a useful guide for improving the quality of PO product and the economic efficiency of industrial plant.
