Polyoxymethylene dimethyl ethers(DMM_n) are promising diesel additives. The synthesis of DMM_n from methylal(DMM) and paraformaldehyde over the NKC-9 acidic ion-exchange resin catalyst was investigated. Many unrecycla...Polyoxymethylene dimethyl ethers(DMM_n) are promising diesel additives. The synthesis of DMM_n from methylal(DMM) and paraformaldehyde over the NKC-9 acidic ion-exchange resin catalyst was investigated. Many unrecyclable by-products such as methyl formate, dimethyl ether and formic acid were produced in the reaction. To increase the selectivity of the desired products DMM_(3-6) and reduce the amount of unrecyclable by-products, the effects of reaction temperature, time, pressure and the molar ratio of the raw materials were evaluated through a series of single factor experiments. Experiments revealed that trace amount of water could suppress the formation of unrecyclable by-products, and the optimum initial water content(less than 2 wt%) was investigated. In addition, the synthetic process needs to go through the polyoxymethylene hemiformals intermediate stage, and then the DMM_n were obtained when polyoxymethylene hemiformals reacted with methanol. Ultimately, a possible mechanism is proposed to describe the formation of DMM_n from polyoxymethylene hemiformals in detail, in which it is revealed that the formation of carbocation intermediates is important in the reaction processes.展开更多
In this work,the oxidation of a mixture of dimethyl ether(DME) and methyl formate(MF) was studied in both an aqueous electrochemical cell and a vapor-fed polymer electrolyte membrane fuel cell(PEMFC)utilizing a multi-...In this work,the oxidation of a mixture of dimethyl ether(DME) and methyl formate(MF) was studied in both an aqueous electrochemical cell and a vapor-fed polymer electrolyte membrane fuel cell(PEMFC)utilizing a multi-metallic alloy catalyst,Pt_(3)Pd_(3)Sn_(2)/C,discovered earlier by us.The current obtained during the bulk oxidation of a DME-saturated 1 M MF was higher than the summation of the currents provided by the two fuels separately,suggesting the cooperative effect of mixing these fuels.A significant increase in the anodic charge was realized during oxidative stripping of a pre-adsorbed DME+MF mixture as compared to DME or MF individually.This is ascribed to greater utilization of specific catalytic sites on account of the relatively lower adsorption energy of the dual-molecules than of the sum of the individual molecules as confirmed by the density fu nctional theory(DFT) calculations.Fuel cell polarization was also conducted using a Pt_(3)Pd_(3)Sn_(2)/C(anode) and Pt/C(cathode) catalysts-coated membrane(CCM).The enhanced surface coverage and active site utilization resulted in providing a higher peak power density by the DME+MF mixture-fed fuel cell(123 mW cm^(-2)at 0.45 V) than with DME(84mW cm^(-2)at 0.35 V) or MF(28 mW cm^(-2)at 0.2 V) at the same total anode hydrocarbon flow rate,temperature,and ambient pressure.展开更多
Halogenated methyl-phenyl ethers (anisoles) are ubiquitous organic compounds in the environment. In the present study, geometrical optimization and electrostatic potential calculations have been performed for 42 hal...Halogenated methyl-phenyl ethers (anisoles) are ubiquitous organic compounds in the environment. In the present study, geometrical optimization and electrostatic potential calculations have been performed for 42 halogenated anisoles at the HF/6-31 G^* level. A number of statistically based parameters have been obtained. By multiple regression method, linear relationships between the gas-chromatographic relative retention time (RRT) and structural descriptors have been established for the training set of 32 halogenated anisoles. The result showed that the parameters derived from electrostatic potentials (ESPs) together with the molecular volume (Vmc) could be well used to express the quantitative structure-RRT relationships of halogenated anisoles. The best two-variable regression model gives a correlation coefficient of 0.980 and a standard deviation of 0.07, and the leave-one-out cross-validated correlation coefficient is 0.975. The goodness of the model has been further validated through exploring the predictive power for the testing set of 10 halogenated anisoles.展开更多
The purpose of this study is to use the newly synthesized molecule Sodium 8-(((carboxymethyl)amino)methyl)-4',7-bishydroxy-isoflavone-3'-sulfonate(M)as a research object,the pharmacological mechanism of the mo...The purpose of this study is to use the newly synthesized molecule Sodium 8-(((carboxymethyl)amino)methyl)-4',7-bishydroxy-isoflavone-3'-sulfonate(M)as a research object,the pharmacological mechanism of the molecule was analyzed by using a series of Systematic pharmacology methods.The results show that the M molecule has a higher drug-like DL value of 0.59 and better molecular property parameters,namely Hdon=4,Hacc=10 and AlogP=0.94;A total of 11 M molecules related targets,namely F2,ESR1,AR,F10,CA2,DPP4,CCNA2,PRSS1,CDK2,GSK3B and PTPN1;A total of 140 diseases are associated with M molecule targets,and these diseases are mainly related to cancer and cardiovascular diseases;A total of 52 pathways involve the pharmacological mechanisms of M molecules,which are mainly related to cancer and other related diseases;GO-enriched analysis showed that these targets are closely related to the regulation of peptidase activity and biological processes such as blood coagulation and hemostasis.This article clearly demonstrated the pharmacological mechanism of M molecule,which provides references for exploring the pharmacological mechanism of new compounds.展开更多
The solid acid SO_4^(2-)/TiO_2 was prepared by immersion method and applied for synthesis of propylene glycol methyl ether acetate(PMA) through esterification reaction of propylene glycol monomethyl ether(PM)and aceti...The solid acid SO_4^(2-)/TiO_2 was prepared by immersion method and applied for synthesis of propylene glycol methyl ether acetate(PMA) through esterification reaction of propylene glycol monomethyl ether(PM)and acetic acid(HAc). The optimal catalyst preparation condition was determined by orthogonal analysis of parameters in a five-factor and four-level test. The obtained solid acid catalysts were characterized in detail by means of X-ray powder diffraction, thermogravimetry, pyridine adsorbed IR analysis, scanning electron microscopy, and BET surface area method. Synthesis of PMA was studied in this paper through experimental investigation of reaction conditions such as temperature, molar ratio of reactants, catalyst dosage and agitation speed. Based on its possible reaction mechanism, a pseudo-homogeneous kinetic model was established and its activation energies E_a^+ and E_a^-,65.68 × 10~3J·mol^(-1) and 57.78 × 10~3J·mol^(-1), were estimated. To prepare shaped solid acid catalyst SO_4^(2-)/TiO_2, the shaping method of impregnation–shaping–impregnation was applied. The optimal molding formulation of solid acid catalyst, obtained from the orthogonal test, was found to be binder 7 wt%, reinforcing agent 20 wt%, pore forming material 2.5 wt%, and lubricant 4 wt%.The results of performance test of catalyst demonstrated that the shaped solid acid catalyst exhibited high activity and stability.展开更多
A novel reverse microemulsion method was used to prepare SnO2/MgO and SnO2/CaO catalysts. It was found that both the catalysts were active for the reaction of catalytic oxidation of dimethyl ether (DME) in the tempe...A novel reverse microemulsion method was used to prepare SnO2/MgO and SnO2/CaO catalysts. It was found that both the catalysts were active for the reaction of catalytic oxidation of dimethyl ether (DME) in the temperature range of 275 to 300 ℃. SnO2/CaO catalyst exhibits much higher activity than SnO2/MgO. On SnO2/CaO catalyst, DME conversion of 21.8% was obtained at 300℃, while selectivities to methyl formate (MF) and dimethoxyethane (DMET) of 19.1% and 59.0% respectively were obtained at 275 ℃.展开更多
The toxicity of methyl tert-butyl ether (MTBE) to Chlorella ellipsoidea and Aphanizomenon flos-aquae was tested and assessed for a 15-d incubation with concentrations of MTBE from high (2.00×10^4 mg/L) to low...The toxicity of methyl tert-butyl ether (MTBE) to Chlorella ellipsoidea and Aphanizomenon flos-aquae was tested and assessed for a 15-d incubation with concentrations of MTBE from high (2.00×10^4 mg/L) to low (2 mg/L). The results showed that the toxicity was low when the concentration of MTBE was in the range 1.00× 10^4-2.00× 10^4 mg/L (the greatest inhibition of growth-rate was 70%-71%, occurred during the day 1-5). Low concentrations (2-500 rag/L) stimulated algal growth up to the greatest effect of 85%-200% when the concentration of MTBE was 50-100 mg/L during day 3-5. The toxicity of MTBE (72-120 h EC50) was 6.65×10^3-9.58×10^3 mg/L for C. ellipsoidea and that is 1.14× 10^4-2.00× 10^4 mg/L for A. floc-aquae. We found that the toxicity and ecological risk of MTBE for the algal community structure were low and the toxicity was influenced by the duration time of the test.展开更多
The contamination of methyl ten-butyl ether (MTBE) in underground waters has become a widely concerned problem all over the world. In this study, a novel dosed culture system with oxygen supplied by H2O2 was introdu...The contamination of methyl ten-butyl ether (MTBE) in underground waters has become a widely concerned problem all over the world. In this study, a novel dosed culture system with oxygen supplied by H2O2 was introduced for MTBE aerobic biodegradation. After 7 d, almost all MTBE was degraded by a pure culture, a member of β-Proteobacteria named as PMI, in a closed system with oxygen supply, while only 40% MTBE was degraded in one without oxygen supply. Dissolved oxygen (DO) levels of the broth in closed systems respectively with and without H2O2 were about 5-6 and 4 mg/L. Higher DO may improve the activity of monooxygemase, which is the key enzyme of metabolic pathway from MTBE to tert-butyl alcohol and finally to CO2, and may result in the increase of the degrading activity of PM1 cell. The purge and trap GC-MS result of the broth in closed systems showed that tea-butyl alcohol, isopronol and acetone were the main intermediate products.展开更多
Hydration heat effect of cement pastes and mechanism of hydroxypropyl methyl cellulose ether (HPMC) and expanded perlite in cement pastes were studied by means of hydration exothermic rate, hydration heat amount, FT...Hydration heat effect of cement pastes and mechanism of hydroxypropyl methyl cellulose ether (HPMC) and expanded perlite in cement pastes were studied by means of hydration exothermic rate, hydration heat amount, FTIR and TG-DTG. The results show that HPMC can significantly delay the hydration induction period and acceleration period of cement pastes. As mixing amount increased, hydration induction period of cement pastes enlarged and accelerated period gradually went back. At the same time, the amount of hydration heat gradually decreased. Expanded perlite had worse delay effects and less change of hydration heat amount of cement pastes than HPMC. HPMC changed the structure of C-S-H during cement hydration. The more amount of HPMC, the more obvious effect. However, EXP had little influence on the structure of C-S-H. At the same age, the content of Ca (OH)2 in cement pastes gradually decreased as the mixing amount increase of HPMC and expanded perlite, and had better delay effect than that single-doped with HPMC or expanded perlite when HPMC and expanded nerlite were both dooed in cement pastes.展开更多
Dimethyl ether (DME) was synthesized from methane through a two-step process, in which CH3Br was prepared from the oxidative bromination reaction of methane in the presence of HBr and oxygen over a Rh-SiO2 catalyst ...Dimethyl ether (DME) was synthesized from methane through a two-step process, in which CH3Br was prepared from the oxidative bromination reaction of methane in the presence of HBr and oxygen over a Rh-SiO2 catalyst and then, in the second step, CH3Br was hydrolyzed to DME over a silica supported metal chloride catalyst. 12 mol%ZnCl2/SiO2 catalyst was found to be the most active, but it deactivated because of Cl- losing.展开更多
A method was developed to determine the concentration of methyl tert-butyl ether(MTBE) in gasoline, diesel and heating oil by gas chromatography(GC) with mass spectrometry(GC-MS) or flame ionization detection(FID). Th...A method was developed to determine the concentration of methyl tert-butyl ether(MTBE) in gasoline, diesel and heating oil by gas chromatography(GC) with mass spectrometry(GC-MS) or flame ionization detection(FID). The diluted gasoline was directly injected into the GC, and the complete separation of MTBE from co-eluting hydrocarbons was not required. GC/MS or GC/FID method can be used to analyze MTBE in different concentration range and have good consistency.展开更多
BACKGROUND The use of methyl-tertiary butyl ether(MTBE)to dissolve gallstones has been limited due to concerns over its toxicity and the widespread recognition of the safety of laparoscopic cholecystectomy.The adverse...BACKGROUND The use of methyl-tertiary butyl ether(MTBE)to dissolve gallstones has been limited due to concerns over its toxicity and the widespread recognition of the safety of laparoscopic cholecystectomy.The adverse effects of MTBE are largely attributed to its low boiling point,resulting in a tendency to evaporate.Therefore,if there is a material with a higher boiling point and similar or higher dissolubility than MTBE,it is expected to be an attractive alternative to MTBE.AIM To determine whether tert-amyl ethyl ether(TAEE),an MTBE analogue with a relatively higher boiling point(102°C),could be used as an alternative to MTBE in terms of gallstone dissolubility and toxicity.METHODS The in vitro dissolubility of MTBE and TAEE was determined by measuring the dry weights of human gallstones at predetermined time intervals after placing them in glass containers with either of the two solvents.The in vivo dissolubility was determined by comparing the weights of solvent-treated gallstones and control(dimethyl sulfoxide)-treated gallstones,after the direct infusion of each solvent into the gallbladder in both hamster models with cholesterol and pigmented gallstones.RESULTS The in vitro results demonstrated a 24 h TAEE-dissolubility of 76.7%,56.5%and 38.75%for cholesterol,mixed,and pigmented gallstones,respectively,which represented a 1.2-,1.4-,and 1.3-fold increase in dissolubility compared to that of MTBE.In the in vitro experiment,the 24 h-dissolubility of TAEE was 71.7%and 63.0%for cholesterol and pigmented gallstones,respectively,which represented a 1.4-and 1.9-fold increase in dissolubility compared to that of MTBE.In addition,the results of the cell viability assay and western blot analysis indicated that TAEE had a lower toxicity towards gallbladder epithelial cells than MTBE.CONCLUSION We demonstrated that TAEE has higher gallstone dissolubility properties and safety than those of MTBE.As such,TAEE could present an attractive alternative to MTBE if our findings regarding its efficacy and safety can be consistently reproduced in further subclinical and clinical studies.展开更多
As an additive of gasoline,methyl tert-butyl ether(MTBE)has a higher solubility in water,which is about 20 times as high as that of benzene.This characteristic results in MTBE dissolving out of the gasoline into the s...As an additive of gasoline,methyl tert-butyl ether(MTBE)has a higher solubility in water,which is about 20 times as high as that of benzene.This characteristic results in MTBE dissolving out of the gasoline into the soil and groundwater.Due to relative unique physicochemical behavior of MTBE it would be an ideal candidate for use in environmental forensic investigations.In order to study the transport and distribution of MTBE in saturated zone of ground water,a two-dimensional experimental cell was setup to simulate the real environment of the groundwater flow.The effects of soil and groundwater flow velocity on the MTBE transport were investigated.The results show that the mobile distance of MTBE in vertical direction was smaller than that in horizontal direction paralleling with the groundwater flow.Because the main dynamics of groundwater flow direction was convection and dispersion,the movement of MTBE is also diffusion in the vertical direction.In addition,the transport of MTBE was more quick in high permeability porous media,and the increase of groundwater flow velocity can accelerate the MTBE plume de-velopment,but the irregularity and randomness of the plume are enhanced synchronously.These research results can give some helps for the investigation of MTBE movement in the groundwater,also can make some references for other petroleum contamination behavior.展开更多
A stereoselective synthetic route to △~5-dehydrosugiyl methyl ether was developed from (S)-(-)-α-cyclocitral, DDQ as a better oxidant for enone was used.
Several pervaporation membranes,cellulose acetate(CA),polyvinylbutyral(PVB),poly(MMA-co-AA),MMA-AA-BA,CA/PVB blend and CA/poly(MMA-co-AA)blend,were prepared,and their pervporation proper-ties were evaluated by separat...Several pervaporation membranes,cellulose acetate(CA),polyvinylbutyral(PVB),poly(MMA-co-AA),MMA-AA-BA,CA/PVB blend and CA/poly(MMA-co-AA)blend,were prepared,and their pervporation proper-ties were evaluated by separation of methanol/C5 or methanol/MTBE(methyl tert-butyl ether),The results shows that the CA composite membrane has a high separation performance (flux Jmethanol=35g.m^-2.h^-1 and separa-tion factor α>400)for methanol /C5 mixtures ,and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer,For CA/poly(MMA-co-AA) blend membrane,the pervapora-tion performance is improved in comparison with CA or poly(MMA-co-AA) membrane,From the experiment of CA/PVB blend membranes for methanol/MTBE mixture,it is found that the compatibility of blends may affect the separation features of blend membrane.展开更多
文摘Polyoxymethylene dimethyl ethers(DMM_n) are promising diesel additives. The synthesis of DMM_n from methylal(DMM) and paraformaldehyde over the NKC-9 acidic ion-exchange resin catalyst was investigated. Many unrecyclable by-products such as methyl formate, dimethyl ether and formic acid were produced in the reaction. To increase the selectivity of the desired products DMM_(3-6) and reduce the amount of unrecyclable by-products, the effects of reaction temperature, time, pressure and the molar ratio of the raw materials were evaluated through a series of single factor experiments. Experiments revealed that trace amount of water could suppress the formation of unrecyclable by-products, and the optimum initial water content(less than 2 wt%) was investigated. In addition, the synthetic process needs to go through the polyoxymethylene hemiformals intermediate stage, and then the DMM_n were obtained when polyoxymethylene hemiformals reacted with methanol. Ultimately, a possible mechanism is proposed to describe the formation of DMM_n from polyoxymethylene hemiformals in detail, in which it is revealed that the formation of carbocation intermediates is important in the reaction processes.
基金Ariel UniversityIsrael National Research Center for Electrochemical PropulsionNew Technologies Research Centre,University of West Bohemia,Pilsen for financially supporting this research。
文摘In this work,the oxidation of a mixture of dimethyl ether(DME) and methyl formate(MF) was studied in both an aqueous electrochemical cell and a vapor-fed polymer electrolyte membrane fuel cell(PEMFC)utilizing a multi-metallic alloy catalyst,Pt_(3)Pd_(3)Sn_(2)/C,discovered earlier by us.The current obtained during the bulk oxidation of a DME-saturated 1 M MF was higher than the summation of the currents provided by the two fuels separately,suggesting the cooperative effect of mixing these fuels.A significant increase in the anodic charge was realized during oxidative stripping of a pre-adsorbed DME+MF mixture as compared to DME or MF individually.This is ascribed to greater utilization of specific catalytic sites on account of the relatively lower adsorption energy of the dual-molecules than of the sum of the individual molecules as confirmed by the density fu nctional theory(DFT) calculations.Fuel cell polarization was also conducted using a Pt_(3)Pd_(3)Sn_(2)/C(anode) and Pt/C(cathode) catalysts-coated membrane(CCM).The enhanced surface coverage and active site utilization resulted in providing a higher peak power density by the DME+MF mixture-fed fuel cell(123 mW cm^(-2)at 0.45 V) than with DME(84mW cm^(-2)at 0.35 V) or MF(28 mW cm^(-2)at 0.2 V) at the same total anode hydrocarbon flow rate,temperature,and ambient pressure.
基金This work was supported by the National Natural Science Foundation of China (No. 20502022) and the Ph.D. Fund of Ningbo ( No. 2004A610010)
文摘Halogenated methyl-phenyl ethers (anisoles) are ubiquitous organic compounds in the environment. In the present study, geometrical optimization and electrostatic potential calculations have been performed for 42 halogenated anisoles at the HF/6-31 G^* level. A number of statistically based parameters have been obtained. By multiple regression method, linear relationships between the gas-chromatographic relative retention time (RRT) and structural descriptors have been established for the training set of 32 halogenated anisoles. The result showed that the parameters derived from electrostatic potentials (ESPs) together with the molecular volume (Vmc) could be well used to express the quantitative structure-RRT relationships of halogenated anisoles. The best two-variable regression model gives a correlation coefficient of 0.980 and a standard deviation of 0.07, and the leave-one-out cross-validated correlation coefficient is 0.975. The goodness of the model has been further validated through exploring the predictive power for the testing set of 10 halogenated anisoles.
基金The study was funded by the Middle-Aged and Young Teachers in Colleges and Universities in Guangxi Basic Ability Promotion Project(No.2017KY0581)and Natural Science Foundation of Guangxi Province(No.2018GXNSFAA138140).
文摘The purpose of this study is to use the newly synthesized molecule Sodium 8-(((carboxymethyl)amino)methyl)-4',7-bishydroxy-isoflavone-3'-sulfonate(M)as a research object,the pharmacological mechanism of the molecule was analyzed by using a series of Systematic pharmacology methods.The results show that the M molecule has a higher drug-like DL value of 0.59 and better molecular property parameters,namely Hdon=4,Hacc=10 and AlogP=0.94;A total of 11 M molecules related targets,namely F2,ESR1,AR,F10,CA2,DPP4,CCNA2,PRSS1,CDK2,GSK3B and PTPN1;A total of 140 diseases are associated with M molecule targets,and these diseases are mainly related to cancer and cardiovascular diseases;A total of 52 pathways involve the pharmacological mechanisms of M molecules,which are mainly related to cancer and other related diseases;GO-enriched analysis showed that these targets are closely related to the regulation of peptidase activity and biological processes such as blood coagulation and hemostasis.This article clearly demonstrated the pharmacological mechanism of M molecule,which provides references for exploring the pharmacological mechanism of new compounds.
基金Supported by the National Natural Science Foundation of China(21306025,21576053)the International Science&Technology Cooperation Program of China(2013DFR90540)
文摘The solid acid SO_4^(2-)/TiO_2 was prepared by immersion method and applied for synthesis of propylene glycol methyl ether acetate(PMA) through esterification reaction of propylene glycol monomethyl ether(PM)and acetic acid(HAc). The optimal catalyst preparation condition was determined by orthogonal analysis of parameters in a five-factor and four-level test. The obtained solid acid catalysts were characterized in detail by means of X-ray powder diffraction, thermogravimetry, pyridine adsorbed IR analysis, scanning electron microscopy, and BET surface area method. Synthesis of PMA was studied in this paper through experimental investigation of reaction conditions such as temperature, molar ratio of reactants, catalyst dosage and agitation speed. Based on its possible reaction mechanism, a pseudo-homogeneous kinetic model was established and its activation energies E_a^+ and E_a^-,65.68 × 10~3J·mol^(-1) and 57.78 × 10~3J·mol^(-1), were estimated. To prepare shaped solid acid catalyst SO_4^(2-)/TiO_2, the shaping method of impregnation–shaping–impregnation was applied. The optimal molding formulation of solid acid catalyst, obtained from the orthogonal test, was found to be binder 7 wt%, reinforcing agent 20 wt%, pore forming material 2.5 wt%, and lubricant 4 wt%.The results of performance test of catalyst demonstrated that the shaped solid acid catalyst exhibited high activity and stability.
基金This work was supported by the Natural Science Foundation of Guangdong Province (4205301, 06021468)Project of Science and Technology of Guangdong Province (2004B33401003, 2005B10201053)+1 种基金Project of Science and Technology of Guangzhou (2006 J1-C0501)National Natural Science Foundation of China (20203012).
文摘A novel reverse microemulsion method was used to prepare SnO2/MgO and SnO2/CaO catalysts. It was found that both the catalysts were active for the reaction of catalytic oxidation of dimethyl ether (DME) in the temperature range of 275 to 300 ℃. SnO2/CaO catalyst exhibits much higher activity than SnO2/MgO. On SnO2/CaO catalyst, DME conversion of 21.8% was obtained at 300℃, while selectivities to methyl formate (MF) and dimethoxyethane (DMET) of 19.1% and 59.0% respectively were obtained at 275 ℃.
基金supported by the National Natural Science Foundation of China (No. 20476099)
文摘The toxicity of methyl tert-butyl ether (MTBE) to Chlorella ellipsoidea and Aphanizomenon flos-aquae was tested and assessed for a 15-d incubation with concentrations of MTBE from high (2.00×10^4 mg/L) to low (2 mg/L). The results showed that the toxicity was low when the concentration of MTBE was in the range 1.00× 10^4-2.00× 10^4 mg/L (the greatest inhibition of growth-rate was 70%-71%, occurred during the day 1-5). Low concentrations (2-500 rag/L) stimulated algal growth up to the greatest effect of 85%-200% when the concentration of MTBE was 50-100 mg/L during day 3-5. The toxicity of MTBE (72-120 h EC50) was 6.65×10^3-9.58×10^3 mg/L for C. ellipsoidea and that is 1.14× 10^4-2.00× 10^4 mg/L for A. floc-aquae. We found that the toxicity and ecological risk of MTBE for the algal community structure were low and the toxicity was influenced by the duration time of the test.
基金Project supported by the National Natural Science Foundation of China (No. 20476099) Zhejiang Provincial Natural Science Foundation (No. Y504272).
文摘The contamination of methyl ten-butyl ether (MTBE) in underground waters has become a widely concerned problem all over the world. In this study, a novel dosed culture system with oxygen supplied by H2O2 was introduced for MTBE aerobic biodegradation. After 7 d, almost all MTBE was degraded by a pure culture, a member of β-Proteobacteria named as PMI, in a closed system with oxygen supply, while only 40% MTBE was degraded in one without oxygen supply. Dissolved oxygen (DO) levels of the broth in closed systems respectively with and without H2O2 were about 5-6 and 4 mg/L. Higher DO may improve the activity of monooxygemase, which is the key enzyme of metabolic pathway from MTBE to tert-butyl alcohol and finally to CO2, and may result in the increase of the degrading activity of PM1 cell. The purge and trap GC-MS result of the broth in closed systems showed that tea-butyl alcohol, isopronol and acetone were the main intermediate products.
基金Funded by the National Natural Science Foundation of China(No.50902107)National Science and Technology Supporting Program (No.2011BAJ04B02)the Fundamental Research Funds for the Central Universities (No.2011-YB-03)
文摘Hydration heat effect of cement pastes and mechanism of hydroxypropyl methyl cellulose ether (HPMC) and expanded perlite in cement pastes were studied by means of hydration exothermic rate, hydration heat amount, FTIR and TG-DTG. The results show that HPMC can significantly delay the hydration induction period and acceleration period of cement pastes. As mixing amount increased, hydration induction period of cement pastes enlarged and accelerated period gradually went back. At the same time, the amount of hydration heat gradually decreased. Expanded perlite had worse delay effects and less change of hydration heat amount of cement pastes than HPMC. HPMC changed the structure of C-S-H during cement hydration. The more amount of HPMC, the more obvious effect. However, EXP had little influence on the structure of C-S-H. At the same age, the content of Ca (OH)2 in cement pastes gradually decreased as the mixing amount increase of HPMC and expanded perlite, and had better delay effect than that single-doped with HPMC or expanded perlite when HPMC and expanded nerlite were both dooed in cement pastes.
基金supported by the Chinese Ministry of Education Project No.107132the Chinese Ministry of Science and Technology Project No.2006BAE02B05,2005CB221406
文摘Dimethyl ether (DME) was synthesized from methane through a two-step process, in which CH3Br was prepared from the oxidative bromination reaction of methane in the presence of HBr and oxygen over a Rh-SiO2 catalyst and then, in the second step, CH3Br was hydrolyzed to DME over a silica supported metal chloride catalyst. 12 mol%ZnCl2/SiO2 catalyst was found to be the most active, but it deactivated because of Cl- losing.
文摘A method was developed to determine the concentration of methyl tert-butyl ether(MTBE) in gasoline, diesel and heating oil by gas chromatography(GC) with mass spectrometry(GC-MS) or flame ionization detection(FID). The diluted gasoline was directly injected into the GC, and the complete separation of MTBE from co-eluting hydrocarbons was not required. GC/MS or GC/FID method can be used to analyze MTBE in different concentration range and have good consistency.
文摘BACKGROUND The use of methyl-tertiary butyl ether(MTBE)to dissolve gallstones has been limited due to concerns over its toxicity and the widespread recognition of the safety of laparoscopic cholecystectomy.The adverse effects of MTBE are largely attributed to its low boiling point,resulting in a tendency to evaporate.Therefore,if there is a material with a higher boiling point and similar or higher dissolubility than MTBE,it is expected to be an attractive alternative to MTBE.AIM To determine whether tert-amyl ethyl ether(TAEE),an MTBE analogue with a relatively higher boiling point(102°C),could be used as an alternative to MTBE in terms of gallstone dissolubility and toxicity.METHODS The in vitro dissolubility of MTBE and TAEE was determined by measuring the dry weights of human gallstones at predetermined time intervals after placing them in glass containers with either of the two solvents.The in vivo dissolubility was determined by comparing the weights of solvent-treated gallstones and control(dimethyl sulfoxide)-treated gallstones,after the direct infusion of each solvent into the gallbladder in both hamster models with cholesterol and pigmented gallstones.RESULTS The in vitro results demonstrated a 24 h TAEE-dissolubility of 76.7%,56.5%and 38.75%for cholesterol,mixed,and pigmented gallstones,respectively,which represented a 1.2-,1.4-,and 1.3-fold increase in dissolubility compared to that of MTBE.In the in vitro experiment,the 24 h-dissolubility of TAEE was 71.7%and 63.0%for cholesterol and pigmented gallstones,respectively,which represented a 1.4-and 1.9-fold increase in dissolubility compared to that of MTBE.In addition,the results of the cell viability assay and western blot analysis indicated that TAEE had a lower toxicity towards gallbladder epithelial cells than MTBE.CONCLUSION We demonstrated that TAEE has higher gallstone dissolubility properties and safety than those of MTBE.As such,TAEE could present an attractive alternative to MTBE if our findings regarding its efficacy and safety can be consistently reproduced in further subclinical and clinical studies.
基金Under the auspices of the National Natural Science Foundation of China(No.20276048)the Municipal Natural Science Foundation of Tianjin(No.06YFJMJC06800)
文摘As an additive of gasoline,methyl tert-butyl ether(MTBE)has a higher solubility in water,which is about 20 times as high as that of benzene.This characteristic results in MTBE dissolving out of the gasoline into the soil and groundwater.Due to relative unique physicochemical behavior of MTBE it would be an ideal candidate for use in environmental forensic investigations.In order to study the transport and distribution of MTBE in saturated zone of ground water,a two-dimensional experimental cell was setup to simulate the real environment of the groundwater flow.The effects of soil and groundwater flow velocity on the MTBE transport were investigated.The results show that the mobile distance of MTBE in vertical direction was smaller than that in horizontal direction paralleling with the groundwater flow.Because the main dynamics of groundwater flow direction was convection and dispersion,the movement of MTBE is also diffusion in the vertical direction.In addition,the transport of MTBE was more quick in high permeability porous media,and the increase of groundwater flow velocity can accelerate the MTBE plume de-velopment,but the irregularity and randomness of the plume are enhanced synchronously.These research results can give some helps for the investigation of MTBE movement in the groundwater,also can make some references for other petroleum contamination behavior.
基金This work was supported by National Science Foundation of China (No. 20264001 ), National Science Foundation of Jiangxi Province, Innovation Fund for Technology Based Firms of China (No. 06C26213601342).
基金the National Natural Science Foundation of China (No. 29372050) for financial support.
文摘A stereoselective synthetic route to △~5-dehydrosugiyl methyl ether was developed from (S)-(-)-α-cyclocitral, DDQ as a better oxidant for enone was used.
基金Supported by the National NaturM Science Foundation of China(No.29836160).
文摘Several pervaporation membranes,cellulose acetate(CA),polyvinylbutyral(PVB),poly(MMA-co-AA),MMA-AA-BA,CA/PVB blend and CA/poly(MMA-co-AA)blend,were prepared,and their pervporation proper-ties were evaluated by separation of methanol/C5 or methanol/MTBE(methyl tert-butyl ether),The results shows that the CA composite membrane has a high separation performance (flux Jmethanol=35g.m^-2.h^-1 and separa-tion factor α>400)for methanol /C5 mixtures ,and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer,For CA/poly(MMA-co-AA) blend membrane,the pervapora-tion performance is improved in comparison with CA or poly(MMA-co-AA) membrane,From the experiment of CA/PVB blend membranes for methanol/MTBE mixture,it is found that the compatibility of blends may affect the separation features of blend membrane.