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2016 Volume 33 Issue 4
2016, 33(4): 367-378
doi: 10.11944/j.issn.1000-0518.2016.04.150439
Abstract:
Metal-organic frameworks(MOFs) are a new class of hybrid porous crystalline materials constructed from metal-oxygen clusters with organic linkers, creating three dimensional ordered frameworks. As porous materials, MOFs usually possess very high surface area. The framework topologies and pore size of MOFs can be designed via choosing various metal centers and organic linkers, their chemical properties can be modified by chemical functionalization of linkers and post modification. These unique characteristics make MOFs one of the research hot spots in the fields of chemistry and materials, and they have shown potential applications in various research areas. But there is a crucial weakness which hinders the development of MOFs, namely, the low stability. However, zirconium-terephthalate-based MOF UiO-66 has remarkable hydrothermal stability, the framework is claimed to be stable up to 500 ℃, and it is also highly resistant to many solvents. UiO-66 has gained great attention since the outstanding qualities. In this review, details of the synthesis modulation and functionalization of UiO-66 are presented. In addition, the research actuality and prospective of UiO-66 in the fields of adsorption, catalysis, etc. are also discussed.
Metal-organic frameworks(MOFs) are a new class of hybrid porous crystalline materials constructed from metal-oxygen clusters with organic linkers, creating three dimensional ordered frameworks. As porous materials, MOFs usually possess very high surface area. The framework topologies and pore size of MOFs can be designed via choosing various metal centers and organic linkers, their chemical properties can be modified by chemical functionalization of linkers and post modification. These unique characteristics make MOFs one of the research hot spots in the fields of chemistry and materials, and they have shown potential applications in various research areas. But there is a crucial weakness which hinders the development of MOFs, namely, the low stability. However, zirconium-terephthalate-based MOF UiO-66 has remarkable hydrothermal stability, the framework is claimed to be stable up to 500 ℃, and it is also highly resistant to many solvents. UiO-66 has gained great attention since the outstanding qualities. In this review, details of the synthesis modulation and functionalization of UiO-66 are presented. In addition, the research actuality and prospective of UiO-66 in the fields of adsorption, catalysis, etc. are also discussed.
2016, 33(4): 379-390
doi: 10.11944/j.issn.1000-0518.2016.04.150328
Abstract:
Nanomaterials find extensive application in various fields due to their small sizes and large specific surface areas. Immobilization of nanoparticles on polymer supports can improve their dispersion and stability and thus improve their performance. This paper reviews the recent progress in the synthesis of polymer-supported nanomaterials and discusses the application of these materials in the catalysis field.
Nanomaterials find extensive application in various fields due to their small sizes and large specific surface areas. Immobilization of nanoparticles on polymer supports can improve their dispersion and stability and thus improve their performance. This paper reviews the recent progress in the synthesis of polymer-supported nanomaterials and discusses the application of these materials in the catalysis field.
2016, 33(4): 391-396
doi: 10.11944/j.issn.1000-0518.2016.04.160057
Abstract:
In this paper, silica hollow nanoparticles(SHNs) with quite uniform particle sizes were prepared by reverse microemulsion system. High resolution transmission electron microscopy(HRTEM) and field emission scanning electron microscopy(FESEM) were used to characterize the structure of SHNs. The carbon dots and silica hollow nanoparticles composite(CD-SHN) was prepared by hydrothermal treatment of self-assembled SHNs in presence of citric acid and ethylene diamine. FESEM images show that the average diameter of sea anemone-like carbon dots-silica nanocomposite is about 1 μm. The size of silica hollow nanosphere is between 30~40 nm, and shell thickness is 10 nm. The CD-SHN demonstrates multicolor fluorescence emission, and high photostability. The maximum excitation and emission wavelengths of CD-SHN are 360 nm and 435 nm, respectively, and 97% of the fluorescence intensity can be retained after being excited for 60 min by a 40 W incandescent lamp. Due to the mild preparation conditions and good biocompatibility of the materials, the composite material has the potential application in biological imaging.
In this paper, silica hollow nanoparticles(SHNs) with quite uniform particle sizes were prepared by reverse microemulsion system. High resolution transmission electron microscopy(HRTEM) and field emission scanning electron microscopy(FESEM) were used to characterize the structure of SHNs. The carbon dots and silica hollow nanoparticles composite(CD-SHN) was prepared by hydrothermal treatment of self-assembled SHNs in presence of citric acid and ethylene diamine. FESEM images show that the average diameter of sea anemone-like carbon dots-silica nanocomposite is about 1 μm. The size of silica hollow nanosphere is between 30~40 nm, and shell thickness is 10 nm. The CD-SHN demonstrates multicolor fluorescence emission, and high photostability. The maximum excitation and emission wavelengths of CD-SHN are 360 nm and 435 nm, respectively, and 97% of the fluorescence intensity can be retained after being excited for 60 min by a 40 W incandescent lamp. Due to the mild preparation conditions and good biocompatibility of the materials, the composite material has the potential application in biological imaging.
2016, 33(4): 397-405
doi: 10.11944/j.issn.1000-0518.2016.04.160053
Abstract:
A benzopyran-based turn-on near-infrared probe (E)-2-(benzopyran)ethenyl-5-(diethylamino)phenyl acrylate(DCM-AC) has been successfully synthesized. Acrylate bond is specifically designed for the response units of amino acid. The results show that the spectral response of DCM-AC towards cysteine is highly sensitivity and selectivity. With increasing the concentration(1.0~8.0 μmol/L) of cysteine, a significant color change can be observed and the fluorescent intensity of DCM-AC at 710 nm increases gradually, showing a good linear relationship with concentration. The limit of detection of DCM-AC for cysteine is determined as 2.8×10-7 mol/L. DCM-AC exhibits a highly selective probe for cysteine over homocysteine and glutathione, with no interference of other substances. The recognition mechanism of the DCM-AC to cysteine is verified by mass spectrum,1H NMR titration and absorption spectra, indicating that cysteine thiol groups attack at acrylate double bond of DCM-AC by addition reaction, and finally removed as the cyclic lactam compound.
A benzopyran-based turn-on near-infrared probe (E)-2-(benzopyran)ethenyl-5-(diethylamino)phenyl acrylate(DCM-AC) has been successfully synthesized. Acrylate bond is specifically designed for the response units of amino acid. The results show that the spectral response of DCM-AC towards cysteine is highly sensitivity and selectivity. With increasing the concentration(1.0~8.0 μmol/L) of cysteine, a significant color change can be observed and the fluorescent intensity of DCM-AC at 710 nm increases gradually, showing a good linear relationship with concentration. The limit of detection of DCM-AC for cysteine is determined as 2.8×10-7 mol/L. DCM-AC exhibits a highly selective probe for cysteine over homocysteine and glutathione, with no interference of other substances. The recognition mechanism of the DCM-AC to cysteine is verified by mass spectrum,1H NMR titration and absorption spectra, indicating that cysteine thiol groups attack at acrylate double bond of DCM-AC by addition reaction, and finally removed as the cyclic lactam compound.
2016, 33(4): 406-411
doi: 10.11944/j.issn.1000-0518.2016.04.150312
Abstract:
Crosslinked porous poly(styrene-co-divinylbenzene) microspheres with tunable particle and pore diameters were synthesized by suspension polymerization and characterized by optical microscopy, SEM and N2 adsorption-desorption isotherm. The particle diameters can be controlled by tuning the content of poly(vinyl alcohol), the water-oil ratio, the stirring rate and the amount of porogen. At the same time, the pore diameters can be tuned by adjusting the type and amount of porogens and the ratio of mixed porogens. The particle diameters decrease with the increase of the amount of PVA, the water-oil ratio and the stirring rate. Both the particle and pore diameters increase with the increase of the amount of porogen and the difference in solubility parameters between the polymer and the porogen. The particle and pore diameters of crosslinked microspheres with 27% crosslinking density are controlled in the range of 100～300 μm and 8～36 nm, respectively. These porous poly(styrene-co-divinylbenzene) microspheres are suitable supports for solid phase synthesis.
Crosslinked porous poly(styrene-co-divinylbenzene) microspheres with tunable particle and pore diameters were synthesized by suspension polymerization and characterized by optical microscopy, SEM and N2 adsorption-desorption isotherm. The particle diameters can be controlled by tuning the content of poly(vinyl alcohol), the water-oil ratio, the stirring rate and the amount of porogen. At the same time, the pore diameters can be tuned by adjusting the type and amount of porogens and the ratio of mixed porogens. The particle diameters decrease with the increase of the amount of PVA, the water-oil ratio and the stirring rate. Both the particle and pore diameters increase with the increase of the amount of porogen and the difference in solubility parameters between the polymer and the porogen. The particle and pore diameters of crosslinked microspheres with 27% crosslinking density are controlled in the range of 100～300 μm and 8～36 nm, respectively. These porous poly(styrene-co-divinylbenzene) microspheres are suitable supports for solid phase synthesis.
2016, 33(4): 412-418
doi: 10.11944/j.issn.1000-0518.2016.04.150259
Abstract:
A sugar-based functional monomer containing double bond was synthesized by the reaction of D-glucose, hydroxylethyl acrylate and 1,4-butanediamine. The as-prepared compound was confirmed by Fourier transform infrared spectroscopy(FTIR) and proton nuclear magnetic resonance spectroscopy(1H NMR). The unsaturated sugar monomer was grafted onto the surface of polyurethane(PU) films by UV-induced grafting polymerization. The surface grafting polymerization was confirmed by FTIR in the attenuated total reflection mode(ATR-FTIR). Water contact angle measurement and platelet adhesion were used to study the hydrophilicity and hemocompatibility of the modified PU films, respectively. It is found that the contact angle of modified PU films decreases from 86° to 45°, and the amount of platelet adhesion is reduced from 14.36×103 cells/mm2 to 2.57×103 cells/mm2. The hydrophilicity of the modified PU films is obviously enhanced and a more hemocompatible interface can be obtained between the film and the biomolecules.
A sugar-based functional monomer containing double bond was synthesized by the reaction of D-glucose, hydroxylethyl acrylate and 1,4-butanediamine. The as-prepared compound was confirmed by Fourier transform infrared spectroscopy(FTIR) and proton nuclear magnetic resonance spectroscopy(1H NMR). The unsaturated sugar monomer was grafted onto the surface of polyurethane(PU) films by UV-induced grafting polymerization. The surface grafting polymerization was confirmed by FTIR in the attenuated total reflection mode(ATR-FTIR). Water contact angle measurement and platelet adhesion were used to study the hydrophilicity and hemocompatibility of the modified PU films, respectively. It is found that the contact angle of modified PU films decreases from 86° to 45°, and the amount of platelet adhesion is reduced from 14.36×103 cells/mm2 to 2.57×103 cells/mm2. The hydrophilicity of the modified PU films is obviously enhanced and a more hemocompatible interface can be obtained between the film and the biomolecules.
2016, 33(4): 419-429
doi: 10.11944/j.issn.1000-0518.2016.04.150196
Abstract:
Coal fly ash composited sodium polyacrylate superabsorbent polymer hydrogel(CFAPAANa) was prepared by free radical solution polymerization of acrylic acid(AA) using potassium persulfate(KPS) as an initiator and N,N'-methylene-bis-acrylamide(NNMBA) as a crosslinker in the presence of coal fly ash(CFA). The CFAPAANa gel has the highest equilibrium swelling degree of 1556 g/g and 168 g/g in distilled water and physiological saline, respectively, when the mass ratio of cross linker to AA is 0.08%, initiator to AA is 0.4%, fly ash to AA is 3%, the neutralization degree of acrylic acid is 70% and polymerization temperature is 70 ℃. The swelling kinetics of gel in different media solution, the water retention properties and degradation behavior in soil were also studied, respectively. Results of the swelling kinetics show that the water absorbent capacity and rate are limited by the expanding polymer segment in distilled water, but the translation and convective diffusion of water play an important role during the swelling process in saline. The results obtained from tests of water retention and degradation show that water retention ratio of hydrogel is 65% after 50 h at 25 ℃, and the degradation percent is about 60% after 50 days in soil. Water retention ratio increases by 8% compared with that of PAANa hydrogel.
Coal fly ash composited sodium polyacrylate superabsorbent polymer hydrogel(CFAPAANa) was prepared by free radical solution polymerization of acrylic acid(AA) using potassium persulfate(KPS) as an initiator and N,N'-methylene-bis-acrylamide(NNMBA) as a crosslinker in the presence of coal fly ash(CFA). The CFAPAANa gel has the highest equilibrium swelling degree of 1556 g/g and 168 g/g in distilled water and physiological saline, respectively, when the mass ratio of cross linker to AA is 0.08%, initiator to AA is 0.4%, fly ash to AA is 3%, the neutralization degree of acrylic acid is 70% and polymerization temperature is 70 ℃. The swelling kinetics of gel in different media solution, the water retention properties and degradation behavior in soil were also studied, respectively. Results of the swelling kinetics show that the water absorbent capacity and rate are limited by the expanding polymer segment in distilled water, but the translation and convective diffusion of water play an important role during the swelling process in saline. The results obtained from tests of water retention and degradation show that water retention ratio of hydrogel is 65% after 50 h at 25 ℃, and the degradation percent is about 60% after 50 days in soil. Water retention ratio increases by 8% compared with that of PAANa hydrogel.
2016, 33(4): 430-435
doi: 10.11944/j.issn.1000-0518.2016.04.150278
Abstract:
The renewable lignocellulosic sources for biocomposites have received much attention in recent years because of the shortage of forest resources. The surface of rice straw was pretreated through humid-heat and chemical modification by coupling reagent which could improve the adhesion capacity between urea formaldehyde resin and rice straw. Meanwhile, the process of fabricating straw board was explored in this paper. The experimental data shows that the straw boards with perfect properties are prepared under the temperature of 150 ℃, the pressure of 15 MPa, the hot pressing time of 8 min, the mass ratio of resin powder to water of 1:1, and the urea formaldehyde resin adhesive content of 15%(mass fraction). The straw boards prepared by 3-glycidyloxypropyltrimethoxysilane(KH560) as surface modification reagent show better properties than those by KH550 and untreated rice straw.
The renewable lignocellulosic sources for biocomposites have received much attention in recent years because of the shortage of forest resources. The surface of rice straw was pretreated through humid-heat and chemical modification by coupling reagent which could improve the adhesion capacity between urea formaldehyde resin and rice straw. Meanwhile, the process of fabricating straw board was explored in this paper. The experimental data shows that the straw boards with perfect properties are prepared under the temperature of 150 ℃, the pressure of 15 MPa, the hot pressing time of 8 min, the mass ratio of resin powder to water of 1:1, and the urea formaldehyde resin adhesive content of 15%(mass fraction). The straw boards prepared by 3-glycidyloxypropyltrimethoxysilane(KH560) as surface modification reagent show better properties than those by KH550 and untreated rice straw.
2016, 33(4): 436-441
doi: 10.11944/j.issn.1000-0518.2016.04.150268
Abstract:
The cofactor-binding domains of malic enzyme(ME) L310, Q401 and L404 were found to have a steric effect on binding of nicotinamide adenine dinucleotide(NAD+). The site-directed mutagenesis of these three sites shows that the cofactor activities of NAD+ analogs(B1~B7) change in some level, indicating that these sites have a critical role in binding the cofactors. A high-throughput screen between malic enzyme mutants and NAD+ analogs affords 2 different mutants capable of taking NAD+ analogs as the cofactor. ME-Q401H/L404T has a 50-fold higher kcat/Km than the that of wild-type ME for the analog B4. For ME-L310M/Q401N, the kcat/Km are 16-fold and 5-fold higher than those of wild-type ME for the cofactors B4 and B3. The coenzyme activity can be increased through site-directed mutagenesis of cofactor-binding domains.
The cofactor-binding domains of malic enzyme(ME) L310, Q401 and L404 were found to have a steric effect on binding of nicotinamide adenine dinucleotide(NAD+). The site-directed mutagenesis of these three sites shows that the cofactor activities of NAD+ analogs(B1~B7) change in some level, indicating that these sites have a critical role in binding the cofactors. A high-throughput screen between malic enzyme mutants and NAD+ analogs affords 2 different mutants capable of taking NAD+ analogs as the cofactor. ME-Q401H/L404T has a 50-fold higher kcat/Km than the that of wild-type ME for the analog B4. For ME-L310M/Q401N, the kcat/Km are 16-fold and 5-fold higher than those of wild-type ME for the cofactors B4 and B3. The coenzyme activity can be increased through site-directed mutagenesis of cofactor-binding domains.
2016, 33(4): 442-451
doi: 10.11944/j.issn.1000-0518.2016.04.150282
Abstract:
A series of novel pseudostilbene azobenzenes was synthesized and their structures were characterized by FT-IR, NMR, MS(ESI) and elemental analysis. The photoisomerization properties and reversible cis/trans isomerization rate constants in solvent were measured via UV-Vis spectroscopy, as well as the fatigue resistance property in polymethyl methacrylate(PMMA) film was performed. The azobenzenes in ethyl acetate have the two bands of π-π* and n-π* inverted on the energy scale and π-π* and n-π* bands are practically superimposed. The isomerization rate constants range from 10-1 to 100 s-1. The trans to cis isomerization rate constants depend on the dipole-dipole interactions and molecular steric hindrance, with the dipole-dipole interactions having larger impact on monobromo-azobenzenes than dibromo-azobenzenes, and a reverse impact from molecular steric hindrances. The faster trans to cis transformation corresponds to the slower cis to trans transformation. The azobenzene has a good fatigue resistance to some extent in PMMA film.
A series of novel pseudostilbene azobenzenes was synthesized and their structures were characterized by FT-IR, NMR, MS(ESI) and elemental analysis. The photoisomerization properties and reversible cis/trans isomerization rate constants in solvent were measured via UV-Vis spectroscopy, as well as the fatigue resistance property in polymethyl methacrylate(PMMA) film was performed. The azobenzenes in ethyl acetate have the two bands of π-π* and n-π* inverted on the energy scale and π-π* and n-π* bands are practically superimposed. The isomerization rate constants range from 10-1 to 100 s-1. The trans to cis isomerization rate constants depend on the dipole-dipole interactions and molecular steric hindrance, with the dipole-dipole interactions having larger impact on monobromo-azobenzenes than dibromo-azobenzenes, and a reverse impact from molecular steric hindrances. The faster trans to cis transformation corresponds to the slower cis to trans transformation. The azobenzene has a good fatigue resistance to some extent in PMMA film.
2016, 33(4): 452-458
doi: 10.11944/j.issn.1000-0518.2016.04.150283
Abstract:
Two kinds of novel polyesters containing Schiff base side groups(P5, P6) were synthesized by multistep reactions. Subsequently, P5 and P6 reacted with zinc acetate to get zinc complexes(P5-Zn, P6-Zn). The structures and properties of polyesters and zinc complexes were characterized by elemental analysis, FT-IR, UV-Vis, 1H NMR, GPC, TG, DSC and fluorescence spectroscopy. Polyesters P5 and P6 are soluble in tetrahydrofurane(THF), CHCl3, N,N-dimethyl formamide(DMF), N,N-dimethyl acetamide(DMAc), dimethylsulfoxide(DMSO), and N-methyl pyrrolidone(NMP). Complexes P5-Zn and P6-Zn can be partly dissolved in THF and CHCl3, and completely dissolved in DMF, DMAc, DMSO, and NMP. The Mw and PDI of P5 and P6 are 4164, 6148 g/mol and 1.42, 1.43, respectively. The 5% mass loss temperatures of P5, P6, P5-Zn and P6-Zn are 339, 348, 367 and 358 ℃, respectively. The Tg values of P5, P5-Zn, P6 and P6-Zn are 88.8, 123.3, 39.8 and 63.8 ℃, respectively. Fluorescence emission peaks of P5 and P6 in DMF solution appear at 418 and 416 nm, emitting weak purple light. Fluorescence emission peaks of P5-Zn and P6-Zn in DMF solution appear at 505 and 506 nm, emitting strong green light. Fluorescence emission peaks of P5-Zn and P6-Zn in solid state appear at 527 and 532 nm, emitting strong green light.
Two kinds of novel polyesters containing Schiff base side groups(P5, P6) were synthesized by multistep reactions. Subsequently, P5 and P6 reacted with zinc acetate to get zinc complexes(P5-Zn, P6-Zn). The structures and properties of polyesters and zinc complexes were characterized by elemental analysis, FT-IR, UV-Vis, 1H NMR, GPC, TG, DSC and fluorescence spectroscopy. Polyesters P5 and P6 are soluble in tetrahydrofurane(THF), CHCl3, N,N-dimethyl formamide(DMF), N,N-dimethyl acetamide(DMAc), dimethylsulfoxide(DMSO), and N-methyl pyrrolidone(NMP). Complexes P5-Zn and P6-Zn can be partly dissolved in THF and CHCl3, and completely dissolved in DMF, DMAc, DMSO, and NMP. The Mw and PDI of P5 and P6 are 4164, 6148 g/mol and 1.42, 1.43, respectively. The 5% mass loss temperatures of P5, P6, P5-Zn and P6-Zn are 339, 348, 367 and 358 ℃, respectively. The Tg values of P5, P5-Zn, P6 and P6-Zn are 88.8, 123.3, 39.8 and 63.8 ℃, respectively. Fluorescence emission peaks of P5 and P6 in DMF solution appear at 418 and 416 nm, emitting weak purple light. Fluorescence emission peaks of P5-Zn and P6-Zn in DMF solution appear at 505 and 506 nm, emitting strong green light. Fluorescence emission peaks of P5-Zn and P6-Zn in solid state appear at 527 and 532 nm, emitting strong green light.
2016, 33(4): 459-465
doi: 10.11944/j.issn.1000-0518.2016.04.150269
Abstract:
IL@TiO2 nanocomposites were synthesized by grafting ionic liquids(ILs) onto the surface of TiO2 via —Si—O— covalent bond. The prepared nanocomposites were acharacterized by IR, thermal gravity-differential analysis and elemental analysis. [C8tespim]Br@TiO2([C8tespim]:N-3-triethoxysilypropyl-4,5-dihydroimidazole) can catalyze the degradation of methyl orange to almost colourless after being illuminated by ultraviolet light for 60 min. The superior performance of prepared nanocomposites compared to that of TiO2 nanopaticles suggests that anion-exchange can tailor the photocatalytic activity, and the activity order is [C8tespim]Br@TiO2< [C8tespim]PF6@TiO2< [C8tespim]Tf2N@TiO2(Tf2N:bis[(trifluoromethyl)sulfonyl]imide).
IL@TiO2 nanocomposites were synthesized by grafting ionic liquids(ILs) onto the surface of TiO2 via —Si—O— covalent bond. The prepared nanocomposites were acharacterized by IR, thermal gravity-differential analysis and elemental analysis. [C8tespim]Br@TiO2([C8tespim]:N-3-triethoxysilypropyl-4,5-dihydroimidazole) can catalyze the degradation of methyl orange to almost colourless after being illuminated by ultraviolet light for 60 min. The superior performance of prepared nanocomposites compared to that of TiO2 nanopaticles suggests that anion-exchange can tailor the photocatalytic activity, and the activity order is [C8tespim]Br@TiO2< [C8tespim]PF6@TiO2< [C8tespim]Tf2N@TiO2(Tf2N:bis[(trifluoromethyl)sulfonyl]imide).
2016, 33(4): 466-472
doi: 10.11944/j.issn.1000-0518.2016.04.150288
Abstract:
A series of Cu/SiO2 catalysts with 20.0% mass fraction of Cu loading was prepared by the ammonia evaporation method using SiO2 as the support and Cu(NH3)42+ aqueous solutions as the precursor. The catalysts were characterized through X-ray diffraction(XRD), H2-temperaure programmed reduction(H2-TPR), transmission electronic microscopy(TEM) and X-ray Auger spectra(XAES) to investigate the influence of the ammonia evaporation rate on the catalyst physical and chemical structure and its catalytic performance for the hydrogenation of dimethyl oxalate(DMO) to ethylene glycol(EG). The catalytic activity measurement experiments were performed under working conditions of 200 ℃, p=3.0 MPa, LHSV=0.4 h-1 and the molar ratio of hydrogen to DMO(n(H2):n(DMO)=80:1). The results indicate that the catalyst prepared under high vacuum during ammonia evaporation has better catalytic performance. For the catalyst prepared under ammonia evaporation pressure of 31.3 kPa, 99.9% conversion of DMO and 94.4% selectivity to EG are obtained. Characterizations through XRD, H2-TPR, TEM and XAES suggest that the higher the ammonia evaporation rate, the faster and more uniform distribution of copper precursors upon the SiO2 support, and the coagulation and growth of the Cu particles during calcination and reduction can be reduced, which guarantees the high catalytic activity, particularly the selectivity to EG.
A series of Cu/SiO2 catalysts with 20.0% mass fraction of Cu loading was prepared by the ammonia evaporation method using SiO2 as the support and Cu(NH3)42+ aqueous solutions as the precursor. The catalysts were characterized through X-ray diffraction(XRD), H2-temperaure programmed reduction(H2-TPR), transmission electronic microscopy(TEM) and X-ray Auger spectra(XAES) to investigate the influence of the ammonia evaporation rate on the catalyst physical and chemical structure and its catalytic performance for the hydrogenation of dimethyl oxalate(DMO) to ethylene glycol(EG). The catalytic activity measurement experiments were performed under working conditions of 200 ℃, p=3.0 MPa, LHSV=0.4 h-1 and the molar ratio of hydrogen to DMO(n(H2):n(DMO)=80:1). The results indicate that the catalyst prepared under high vacuum during ammonia evaporation has better catalytic performance. For the catalyst prepared under ammonia evaporation pressure of 31.3 kPa, 99.9% conversion of DMO and 94.4% selectivity to EG are obtained. Characterizations through XRD, H2-TPR, TEM and XAES suggest that the higher the ammonia evaporation rate, the faster and more uniform distribution of copper precursors upon the SiO2 support, and the coagulation and growth of the Cu particles during calcination and reduction can be reduced, which guarantees the high catalytic activity, particularly the selectivity to EG.
2016, 33(4): 473-480
doi: 10.11944/j.issn.1000-0518.2016.04.150265
Abstract:
High purity Ca-Al-layered double hydroxides(LDH) was prepared in an ethanol/water solution at a volume ratio of 4:1. Effect of sorbent dosage, adsorption time, pH value, inorganic electrolyte(Na2CO3, KCl, Na2SO4, KNO3), temperature for phosphate adsorption were investigated. As prepared Ca-Al-LDH is an effective sorbent for phosphate adsorption. The maximum adsorption capacity of phospahte is 160.78 mg/g and the phosphate removal efficiency reaches to 95.88% at pH 5.1, temperature 318 K, time 600 min, solid/liquor ratio of 0.15 g/250 mL and initial phosphate concentration of 80 mg/L. Inorganic anions can restrain the adsorption of phosphorus on Ca-Al-LDH absorbent. Sorption capacity of phosphate is decreased 23.99% from 69.96 mg/g to 53.18 mg/g with increasing the concentration of Cl- from 2.5 g/L to 25 g/L. The sorption capacity is reduced about 24.79% with SO42- at the same conditions. Other inorganic anion also has a certain influence on phosphate sorption in pure Ca-Al-LDH. The second order kinetic equation is suitable for describing the adsorption process, and the Langmuir isotherm model fits the data well. The sorption mechanism is electrostatic attraction, chemosorption and anion intercalation.
High purity Ca-Al-layered double hydroxides(LDH) was prepared in an ethanol/water solution at a volume ratio of 4:1. Effect of sorbent dosage, adsorption time, pH value, inorganic electrolyte(Na2CO3, KCl, Na2SO4, KNO3), temperature for phosphate adsorption were investigated. As prepared Ca-Al-LDH is an effective sorbent for phosphate adsorption. The maximum adsorption capacity of phospahte is 160.78 mg/g and the phosphate removal efficiency reaches to 95.88% at pH 5.1, temperature 318 K, time 600 min, solid/liquor ratio of 0.15 g/250 mL and initial phosphate concentration of 80 mg/L. Inorganic anions can restrain the adsorption of phosphorus on Ca-Al-LDH absorbent. Sorption capacity of phosphate is decreased 23.99% from 69.96 mg/g to 53.18 mg/g with increasing the concentration of Cl- from 2.5 g/L to 25 g/L. The sorption capacity is reduced about 24.79% with SO42- at the same conditions. Other inorganic anion also has a certain influence on phosphate sorption in pure Ca-Al-LDH. The second order kinetic equation is suitable for describing the adsorption process, and the Langmuir isotherm model fits the data well. The sorption mechanism is electrostatic attraction, chemosorption and anion intercalation.
2016, 33(4): 481-488
doi: 10.11944/j.issn.1000-0518.2016.04.150315
Abstract:
Rapid analysis chemical composition of plant samples was achieved using internal extractive electrospray ionization mass spectrometry(iEESI-MS) without any sample pretreatment. In this study, fresh asparagus tubers together with two kinds of dry asparagus tubers were treated as representative samples for the iEESI-MS analysis. Choosing methanol as an iEESI extractant, various chemical composition in asparagus tissue samples was profiled in mass scan range of m/z 50~1000 under the positive ion detection mode, and through collision-induced dissociation(CID) experiments, nutrient and medicinal components including sugars, amino acids, alkaloids, and rutin were identified, which play an significant role in development of pharmaceutical drugs, natural product research and understanding of primary and secondary metabolites. Our experimental results demonstrate that iEESI-MS makes rapid recognition of chemical composition differences in different asparagus. Such information renders the nutritious and medicinal assessment of plant natural products possible. The merits of iEESI-MS include no sample pretreatment, high-throughput(less than 1 min per sample), low sample consumption, simplicity, as well as good specificity, showing potential applications in phytochemicals analysis.
Rapid analysis chemical composition of plant samples was achieved using internal extractive electrospray ionization mass spectrometry(iEESI-MS) without any sample pretreatment. In this study, fresh asparagus tubers together with two kinds of dry asparagus tubers were treated as representative samples for the iEESI-MS analysis. Choosing methanol as an iEESI extractant, various chemical composition in asparagus tissue samples was profiled in mass scan range of m/z 50~1000 under the positive ion detection mode, and through collision-induced dissociation(CID) experiments, nutrient and medicinal components including sugars, amino acids, alkaloids, and rutin were identified, which play an significant role in development of pharmaceutical drugs, natural product research and understanding of primary and secondary metabolites. Our experimental results demonstrate that iEESI-MS makes rapid recognition of chemical composition differences in different asparagus. Such information renders the nutritious and medicinal assessment of plant natural products possible. The merits of iEESI-MS include no sample pretreatment, high-throughput(less than 1 min per sample), low sample consumption, simplicity, as well as good specificity, showing potential applications in phytochemicals analysis.
