Direct synthesis of dimethyl ether(DME)by CO2 hydrogenation has been investigated over three hybrid catalysts prepared by different methods:co-precipitation,sol-gel,and solid grinding to produce mixed Cu,ZnO,ZrO2 cata...Direct synthesis of dimethyl ether(DME)by CO2 hydrogenation has been investigated over three hybrid catalysts prepared by different methods:co-precipitation,sol-gel,and solid grinding to produce mixed Cu,ZnO,ZrO2 catalysts that were physically mixed with a commercial ferrierite(FER)zeolite.The catalysts were characterized by N2 physisorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),temperature programmed desorption of CO2(CO2-TPD),temperature programmed desorption of NH3(NH3-TPD),and temperature programmed H2 reduction(H2-TPR).The results demonstrate that smaller CuO and Cu crystallite sizes resulting in better dispersion of the active phases,higher surface area,and lower reduction temperature are all favorable for catalytic activity.The reaction mechanism has been studied using in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).Methanol appears to be formed via the bidentate-formate(b-HCOO)species undergoing stepwise hydrogenation,while DME formation occurs from methanol dehydration and reaction of two surface methoxy groups.展开更多
Cellulose is a biodegradable and renewable natural material that it is naturally resistant to breaking and modification. Moreover, the crystalline structure of cellulose is a major factor restricting its industrial ut...Cellulose is a biodegradable and renewable natural material that it is naturally resistant to breaking and modification. Moreover, the crystalline structure of cellulose is a major factor restricting its industrial utilization. In this study, cellulose polymorphs were prepared from natural cellulose, and their solvability and thermal response were investigated. Using liquid- and solid-state NMR signals, the distinct types and dissolving states of cellulose polymorphs were identified. The thermal behavior of the polymorphic forms of cellulose-d was also evaluated, and cellulose Ⅱ exhibited the poorest thermal stability and a unique exothermic reaction.展开更多
The conversion of lignocellulose to value-added products is normally focused on fuel production;however,large-scale biorefineries require a cost-effective pretreatment process that can effectively fractionate the thre...The conversion of lignocellulose to value-added products is normally focused on fuel production;however,large-scale biorefineries require a cost-effective pretreatment process that can effectively fractionate the three main constituents of lignocellulose for the production of chemicals,fuels,and materials.In this study,a hemicellulosic biopolymer from poplar was fractionated by a mild organosolv process and the effects of various chemicals(sodium hydroxide,triethylamine,and formic acid)and alcohols on the fractionation efficiency and structural variation of hemicellulose were examined.Comparative studies indicated that an acidic catalyst decreased the purity of hemicelluloses by partial degradation of cellulose,and the core of the hemicellulosic biomacromolecule could be released and dissolved under alkaline conditions with 5.8%~19.0%yields.In addition,the use of alcohol with longer alkyl chains facilitated the release of the hemicellulosic biomacromolecule by partially cleaving the ether bonds in the lignincarbohydrate complex(LCC);this is probably due to steric hindrance.The thermal degradation behavior showed that complete pyrolysis was easily achieved for the hemicellulosic polymer with minimal branches irrespective of its molecular weight.展开更多
Heavy alcohol drinking is a major public health problem,causing a large disease,social and economic burden in societies.Subjective response (SR) to alcohol is an intermediate characteristic of heavy drinking.A variety...Heavy alcohol drinking is a major public health problem,causing a large disease,social and economic burden in societies.Subjective response (SR) to alcohol is an intermediate characteristic of heavy drinking.A variety of candidate genes have been reported to be associated with SR to alcohol.In this study,we investigated nine single nucleotide polymorphisms (SNPs) related to SR to alcohol in healthy individuals from five Chinese ethnic groups,the Han,Hui,Tibetan,Mongolian and Uygur populations,and a total of 584 bloodstain samples were collected.The nine SNPs included four SNPs in alcohol-metabolizing genes (ADH1B,ADH1C,ALDH2 and CYP2E1*5B) and five SNPs in genes of neurobiological pathways (GABRA2,OPRM1,CHRNA3,HYKK and SLC6A4).A SNaPshot analysis method was developed to type these SNPs simultaneously,and all samples were typed successfully.Statistical analyses of the allele frequencies indicated that the frequencies of all SNPs,except for ADH1C,showed varying degrees of difference in the five studied ethnic groups.Tibetans showed the highest frequencies of risk alleles for heavy drinking at most loci.The genetic polymorphic differences found in this study revealed the variation in genetic susceptibility to heavy drinking in the studied populations.展开更多
基金supported by the China Scholarship Council(No.201608140182)the University of Wyomingand State of Wyoming。
文摘Direct synthesis of dimethyl ether(DME)by CO2 hydrogenation has been investigated over three hybrid catalysts prepared by different methods:co-precipitation,sol-gel,and solid grinding to produce mixed Cu,ZnO,ZrO2 catalysts that were physically mixed with a commercial ferrierite(FER)zeolite.The catalysts were characterized by N2 physisorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),temperature programmed desorption of CO2(CO2-TPD),temperature programmed desorption of NH3(NH3-TPD),and temperature programmed H2 reduction(H2-TPR).The results demonstrate that smaller CuO and Cu crystallite sizes resulting in better dispersion of the active phases,higher surface area,and lower reduction temperature are all favorable for catalytic activity.The reaction mechanism has been studied using in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).Methanol appears to be formed via the bidentate-formate(b-HCOO)species undergoing stepwise hydrogenation,while DME formation occurs from methanol dehydration and reaction of two surface methoxy groups.
基金the National Natural Science Foundation of China (Grant No. 31770622)the Beijing Natural Science Foundation (Grant No. 6174046)+1 种基金the Fundamental Research Funds for the Central Universities (No. 2017PT13)the China Scholarship Council (International Clean Energy Talent Programme (iCET), Grant No. 201702660054).
文摘Cellulose is a biodegradable and renewable natural material that it is naturally resistant to breaking and modification. Moreover, the crystalline structure of cellulose is a major factor restricting its industrial utilization. In this study, cellulose polymorphs were prepared from natural cellulose, and their solvability and thermal response were investigated. Using liquid- and solid-state NMR signals, the distinct types and dissolving states of cellulose polymorphs were identified. The thermal behavior of the polymorphic forms of cellulose-d was also evaluated, and cellulose Ⅱ exhibited the poorest thermal stability and a unique exothermic reaction.
基金financially supported by the Fundamental Research Funds for the Central Universities (2017TP13)the National Key R&D Program of China (2016YFD0600803)+2 种基金2018 National Student Research Training Program (201710022033)the Innovation Program of College of Materials Science and Technologysupported by the 2017 the international Clean Energy Talent program (No.201702660054)
文摘The conversion of lignocellulose to value-added products is normally focused on fuel production;however,large-scale biorefineries require a cost-effective pretreatment process that can effectively fractionate the three main constituents of lignocellulose for the production of chemicals,fuels,and materials.In this study,a hemicellulosic biopolymer from poplar was fractionated by a mild organosolv process and the effects of various chemicals(sodium hydroxide,triethylamine,and formic acid)and alcohols on the fractionation efficiency and structural variation of hemicellulose were examined.Comparative studies indicated that an acidic catalyst decreased the purity of hemicelluloses by partial degradation of cellulose,and the core of the hemicellulosic biomacromolecule could be released and dissolved under alkaline conditions with 5.8%~19.0%yields.In addition,the use of alcohol with longer alkyl chains facilitated the release of the hemicellulosic biomacromolecule by partially cleaving the ether bonds in the lignincarbohydrate complex(LCC);this is probably due to steric hindrance.The thermal degradation behavior showed that complete pyrolysis was easily achieved for the hemicellulosic polymer with minimal branches irrespective of its molecular weight.
基金Ethical approval was given by the medical ethics committee of Sichuan University with the following reference number:2012-001-1.
文摘Heavy alcohol drinking is a major public health problem,causing a large disease,social and economic burden in societies.Subjective response (SR) to alcohol is an intermediate characteristic of heavy drinking.A variety of candidate genes have been reported to be associated with SR to alcohol.In this study,we investigated nine single nucleotide polymorphisms (SNPs) related to SR to alcohol in healthy individuals from five Chinese ethnic groups,the Han,Hui,Tibetan,Mongolian and Uygur populations,and a total of 584 bloodstain samples were collected.The nine SNPs included four SNPs in alcohol-metabolizing genes (ADH1B,ADH1C,ALDH2 and CYP2E1*5B) and five SNPs in genes of neurobiological pathways (GABRA2,OPRM1,CHRNA3,HYKK and SLC6A4).A SNaPshot analysis method was developed to type these SNPs simultaneously,and all samples were typed successfully.Statistical analyses of the allele frequencies indicated that the frequencies of all SNPs,except for ADH1C,showed varying degrees of difference in the five studied ethnic groups.Tibetans showed the highest frequencies of risk alleles for heavy drinking at most loci.The genetic polymorphic differences found in this study revealed the variation in genetic susceptibility to heavy drinking in the studied populations.
