Totally found 32 items.

  • [会议] Study Hydrotalcite Solid Base Catalyzed Preparation of Natural L-α- Phosphatidyl Glycerol Phosphatidylcholine
    As a water-soluble phospholipid, L-α-Glycerophosphocholine(GPC for short) is naturally exist in the body of human and animals~[1]. It can be used for treating brain mental illness such as alzheimer's disease and mania. Therefore, it can be widely used in medicine, food and cosmetics industries. In this paper, the craft process on making GPC by use hydrotalcites solid base catalysts of transesterification reaction which use natural phospholipids(phosphatidyl choline, PC for short) as raw materials. It is investigated the effects which influenced by types of catalyst, conditions of preparation and reaction contions, in order to accumulate basic data for scale-up progress and practical application. The calcined U-LDH and T-LDH hydrotalcites catalyst was characterized by Hmmett indicator method, XRD, FT-IR, DSC, SEM. The results showed the optimum U-LDO catalyst was obtained by calcined at 773 K and Mg/Al ratio at 3~[2]. The optimal reaction condition of the Mg/Al hydrotalcites catalysts system is as follows: 10.5 mmol/L PC concentration; catalyst amount 9%; 350 rpm; reaction temperature of 65oC and reaction time of 280 min; conversion of PC was 94.4% and yield of GPC 92.3%. The results stability of U-LDO catalysts showed reused four times. After loss of activity of U-LDH hydrotalcite catalyst~[3], the method of resuming activity of calcined at 773 K catalyst is to supply activated components. Hydrotalcite-like compounds containing Mg~(2+), Al~(3+)and Fe~(3+) layered double hydroxide were synthesized by co-precipitation method. The calcined Mg/Al/Fe hydrotalcites catalyst was characterized by BET, SEM, XRD, TGA, FT-IR. The results showed the optimum Mg/Al/Fe catalyst was obtained by calcined at 773 K and Mg/Al/Fe ratio at 15:8:1[4]. The optimal reaction condition of the Mg Al Fe 15 hydrotalcites catalysts system is as follows: 10.5 mmol/L PC concentration; catalyst amount 7%; 350 rmp; reaction temperature of 60 and reaction time of ℃120 min; conversion of PC was 97.4% and yield of GPC 93.3%. The reasons for loss of activity of Mg Al Fe 15 hydrotalcites catalysts were easily absorb H_2 O and CO_2 in atmosphere. The method of resuming activity of calcined at 773 K catalyst is to supply activated components. Kinetics of PC transesterification by U-RLDO catalytic was analyzed. The experimental data regression showed that reaction complied with the pseudo-first order kinetic model. According to Arrhenius Equation, mass transfer parameter was 0.00408min-1; reaction rate constant was 0.9815min-1; the activation energy of U-RLDO was 71.5k J/mol.
    关键词: L-α-glycerophosphocholine;hydrotalcites;transesterification
  • [会议] Visible-Light-Active Plasmonic Ag-Sr TiO_3 Nanocomposites for the Degradation of NO in Air with High Selectivity
    Harnessing inexhaustible solar energy for photocatalytic disposal of nitrogen oxides is of great significance nowadays.~[1] In this study, Ag-Sr Ti O_3 nanocomposites(Ag-STO) were synthesized via one-pot solvothermal method for the first time.~[2,3] The deposition of Ag nanoparticles incurs a broad plasmonic resonance absorption in the visible light range, resulting in enhanced visible light driven activity on NO removal in comparison with pristine Sr Ti O_3. The Ag loading amount has a significant influence on light absorption properties of Ag-STO, which further affects the photocatalytic efficiency.~[4] It was shown that 0.5% Ag loading onto Sr Ti O_3(in mass ratio) could remove 30% of NO in a single reaction path under visible light irradiation, which is twice higher than that achieved on pristine Sr Ti O_3. Most importantly, the generation of harmful intermediate(NO_2) is largely inhibited over Sr Ti O_3 and Ag-STO nanocomposites, which can be ascribed to the basic surface property of strontium sites. As identified by electron spin resonance(ESR) spectra, ·O_2~- and ·OH radicals are the major reactive species for NO oxidation. Essentially speaking, the abundance of reactive oxygen radicals produced over Ag-STO nanocomposites are responsible for the improved photocatalytic activity. This work provides a facile and controllable route to fabricate plasmonic Ag-Sr Ti O_3 nanocomposite photocatalyst featuring high visible light activity and selectivity for NO abatement.
    关键词: Air pollution control;Ag-SrTiO_3 nanocomposites;Plasmonic effect;Photocatalysis;NO removal
  • [会议] Bismuth-Based Heterojunction Photocatalysts for Efficient NO Abatement in Ambient Conditions
    Study found that secondary organic aerosols(SOA) have important contribution to the concentration of PM2.5 of typical heavy haze pollution in cities of our country ~[1]. Nitrogen oxides(NOx) and volatile organic compounds(VOCs) are important precursors for formation of SOA. Therefore, taking effective measures and technologies to control concentration level of NOx and VOCs in the atmosphere has important practical significance to improve the air quality in our country. Fabrication of heterostructured photocatalysts has drawn significant interest in photocatalytic degradation of organic and inorganic pollutants because these catalysts can expand the light absorption range and promote the separation of photo-generated charge carriers ~[2]. Most bismuth compounds with a layered structure show enhanced visible light absorption and efficient photocatalytic performance ~[3]. Given the thermal instability of(BiO)_2CO_3 ~[4], we adopted in situ calcination to obtain Bi2O3/(BiO)_2CO_3 heterojunction. 2.5 mmol of Bi(NO_3)_3·5H_2O and 10 mmol of CO(NH_2)_2 were mixed and dissolved into 35 m L of deionized water. After vigorous agitation for 30 min at room temperature, the formed suspension liquid was transferred into a 50 m L Teflon-lined stainless steel autoclave and heated at 160 °C for 12 h. After naturally cooling the autoclave to room temperature, the white(BiO)_2CO_3 sample was collected, repeatedly washed with deionized water and absolute ethanol three times, and dried overnight at 70 °C. The as-prepared(BiO)_2CO_3 sample was further calcined at 400 °C for 1 h to obtain Bi_2O_3/(BiO)_2CO_3 composites. And the performance of the fabricated catalysts for NO removal was evaluated. Results showed that the as-prepared Bi_2O_3/(BiO)_2CO_3 exhibited significant visible light photocatalytic activity for NO removal(Figure 1a). The different photocatalytic results were attributed to the improved charge separation and light absorption range under solar light, as confirmed by UV-vis diffuse reflectance spectroscopy(DRS)(Figure 1b) and photocurrent data(Figure 1c). The heterojunction interface formed cannot only improve the charge separation of photo-induced electron–hole pairs but also broaden the light absorption range. Multiple runs of photocatalytic experiments showed that Bi_2O_3/(BiO)_2CO_3 was not significantly deactivated during long-term NO oxidation(Figure 1d). This result indicates that the BOC-based heterojunction is a stable photocatalyst with promising application in gaseous NOx abatement.
    关键词: photocatalysis;NO removal;bismuth system
  • [会议] Creation of Three-dimensionally Ordered Macroporous Fe~(3+)-doped TiO_2 with Excellent Visible-light-driven Photocatalytic Activity
    Three-dimensionally ordered macroporous(3DOM) Fe~(3+)-doped Ti O_2 photocatalysts were prepared using a colloidal crystal template method with low-cost raw material including ferric trichloride, isopropanol, tetrabutyl titanate and polymethyl methacrylate. The as-prepared 3DOM Fe~(3+)-doped Ti O_2 photocatalysts were characterized by various analytical techniques. The TEM and SEM images showed that the obtained photocatalysts possess well-ordered macroporous structure in three dimensional orientations. As proved by XPS and EDX analysis that Fe~(3+) ions have been introduced Ti O_2 lattice and the doped Fe~(3+) ions can act as the electron acceptor/donor centers to significantly enhance the electron transfer from the bulk to surface of Ti O_2, resulting in more electrons could take part in the oxygen reduction process thereby decreasing the recombination rate of photogenerated charges. Meanwhile, the 3DOM architecture with the feature of interfacial chemical reaction active sites and optical absorption active sites is remarkably favorable for the reactant transfer and light trapping in the photoreaction process. As a result, the 3DOM Fe~(3+)-doped Ti O_2 photocatalysts show the considerably higher photocatalytic activity for decomposition of the Rhodamine B(Rh B) and the generation of hydrogen under visible light irradiation due to the synergistic effects of open, interconnected macroporous network and metal ion doping.
    关键词: Ti O_2;Three-dimensionally ordered macroporous;Fe~(3+) doping;Photocatalysis
  • [会议] Two Dimetallocenes with Vanadium and Chromium —Electronic Structures and Their Promising Application in Hydrogen Storage
    As a clean energy, because of its environmental protection, large chemical energy, abundance and high efficiency, hydrogen energy is widely considered that it is hopeful to replace fossil energy and ease current environmental pollution~[1-6]. The strength of Kubas interaction is intermediate between physisorption and chemisorption, therefore, those adsorbed hydrogen molecules meet the reversible adsorbed-desorbed conditions under ambient pressures and temperatures~[7]. In this paper, the hydrogen storage capacities of the two sandwich-type Cp_2TM_2 [Cp= cyclopentadienyl(C_5H_5); TM=V or Cr)] dimetallocenes were studied using first-principles calculations. According to the B3PW91 method in density functional theory(DFT) performed by the Gaussian 09 program package, Cp_2V_2 and Cp_2Cr_2 could adsorb up to seven and six hydrogen molecules, respectively. The predicted hydrogen storage densities of Cp_2V_2 and Cp_2Cr_2 were 5.73 and 4.91 wt%, respectively. Additionally, because hydrogen binding energies bound by Kubas model were 0.39 and 0.43 e V/H_2, respectively, both the Cp_2V_2 and Cp_2Cr_2 dimetallocenes were proven to be favourable for reversible adsorption and desorption of hydrogen molecules under ambient conditions. However, the hydrogen atoms absorbed on Cp_2V_2 and Cp_2Cr_2 with covalent hydrogen bonds would need high temperatures or catalysts to desorb. We expect that our results will be instrumental in the on-going exploration of potential hydrogen storage materials.
    关键词: sandwich-type dimetallocenes;electronic structures;hydrogen storage
  • [会议] Nitrogen-doped Carbon Quantum Dots Decorated Zn Sn(OH)_6 Nanocomposite with Enhanced Visible Light Photocatalytic Oxidation Activity for NO Removal
    Indoor nitrogen oxides can enter the body through breathing, and it cause irritation of the respiratory tract, lungs, and the corrosion damage of organs. So, it is importance to remove these pollutants to improve the indoor air quality. NOx from industrial emissions, traditional techniques such as adsorption, Selective Catalytic Reduction(SCR), and thermal catalysis strategies could function well. But they are not economically feasible for NOx removal at ppb level in both indoor and outdoor air. Photocatalysis, is most potential in air purification under mild conditions, as a green and effective technology. In this work, we report a suite way to synthetic nitrogen doped carbon quantum dots and Nitrogen-doped carbon quantum dots(N-CQDs) used to decorated Zn Sn(OH)6(ZHS) nanocomposite with enhanced visible light photocatalytic oxidation activity for NO removal. Compared to ZHS, which is capable of removing 0% nitric oxide(NO) under visible light conditions, the 20 mg N-CQDs/ZHS can mostly remove NO(30%) under the same conditions. Furthermore, the structure was designed to accelerate carrier transfer among the Zn Sn(OH)6 nanocomposite interior while the Nitrogen-doped carbon quantum dots(N-CQDs) were constructed to facilitate surface charge carrier separation. The mechanisms for the improvement of the photocatalytic performance of the composites were discussed on the basis of the results.
    关键词: NO removal;N-CQDs doped;photocatalyst;ZnSn(OH)_6
  • [会议] Theoretical Investigation of Transition Metal Catalytic Activityn Gas Phase ——Theoretical Investigation for Two–State Reactivity of CO_2 Hydrogenation Catalyzed by Ru in the Gas Phase
    For transition metal or transition metal oxides, the existence of empty or half full of d orbitals in the chemical reaction can interact with the frontier orbital of substrate molecule and formed intermediate formation,(e.g., electronic granted- accepted)~[1]. the process reduces the reaction energy barrier, which is most chemists with transition metals and their complexes as catalyst.Gas–phase CO_2 catalyzed activation hydrogenation by Ru atoms was studied at the density functional theory(DFT)~[2]. Based on the structure optimization of the different potential energy surface, there are two crossing points between singlet and triplet potential energy surfaces and there is a crossing point between quintet and triplet potential energy surfaces in the dehydration process. Spin transition probabilities in the vicinity of the intersections have been calculated by the Landau–Zener model theory~[3]. The results showed that 3 MECPs have strong spin–orbit coupling effect and higher spin transition probability, and all spin inversion occurred in s orbit and different d orbits of ruthenium,indicate this is a typical two–state reactivity(TSR) reaction. During the formation of formaldehyde and methanol is an endothermic reaction are all go against to reaction. Among them, the formaldehyde of heat absorption capacity is higher than methanol, so in the course of the reaction, hardly produce formaldehyde. The reaction of these two parts are in the triplet state reaction, are single-state reaction(SSR).
    关键词: two–state reactivity(TSR);Carbon dioxide hydrogenation;minimum energy crossing point(MECP);transition metal catalyzed;intersystem crossing(ISC)
  • [会议] Oxygen Vacancies-Induced Bi_2O_3/Bi_2O_2CO_3 Heterojunction for Enhancing Photocatalytic Performance and Its Photocatalytic Mechanism
    Oxygen defects, as shallow donors, have obtained attention with significantly enhanced performance for electrical conductivities and charge storage in environmental pollution control. Here we demonstrate that a one-step heat-treatment strategy can fabricate nano-structured Bi_2O_3/Bi_2O_2CO_3 heterojunction by using bismuth oxide with narrow band gap, and can self-dope oxygen vacancies in the same time. Combined with the Raman, electron paramagnetic resonance and theoretical calculation approaches, we elucidate that the oxygen vacancies-induced Bi_2O_3/Bi_2O_2CO_3 heterojunction were controllably formed by a facile, low-cost and one-step heat-treatment under nirtogen atmosphere. The results show that the oxygen vacancies-indueced Bi_2O_3/Bi_2O_2CO_3 heterojunction photocatalyt exhibits excellent and stable removal efficiency to NOx. The enhancement of adsorption ability of NO, photoabsorption properties and the migration and separation of photogenerated carriers for improving the photoactivity can be attributed to the introduction of surface. Compared the Bi_2O_3/Bi_2O_2CO_3 heterojunction photocatalyt without oxygen defects, the mechanism of the photocatalytic removal of NOx over oxygen vacancies-induced Bi_2O_3/Bi_2O_2CO_3 heterojunction was slightly changed. Our findings may provide an opportunity to develop a simple, efficient, cost-effective and promising strategy for the design of efficient solar energy driven photocatalytic materials, which can be used for air pollution control.
    关键词: oxygen vacancies;Bi_2O_3/Bi_2O_2CO_3heterojunction;photoactivity;mechanism
  • [会议] Photocatalytic Removal of NO with Aerosol Flow Synthesized B, N-Codoped TiO_2 Hollow Spheres
    In this study, we demonstrate that B-N-codoped TiO_2 photocatalyst possesses superior photocatalytic activity to the single element doped TiO_2 products on the degradation of NO in a flow system under both simulated solar-light and visible light irradiation. The B, N-codoped TiO_2 photocatalyst was prepared by aerosol assisted flow synthetic method in the presence of H_3BO_3 and urea. Characterization results revealed that B, N-codoped TiO_2 photocatalyst was composed of hollow microspheres. Boron and nitrogen were in the form of Ti-O-B and N-Ti-O structures, respectively. The introduction of B and N into the TiO_2 lattice could effectively tune the band gap of TiO_2 and extend its optical response to the visible-light region. The synergistic effect of B and N co-doping on visible light driven photocatalytic activity enhancement of TiO_2 was discussed on the basis of experimental results. The synergistic effect of B and N co-doping on visible light driven photocatalytic activity enhancement of TiO_2 was studied in detail. This work provides a facile and large scale method to prepare B, N-codoped TiO_2 visible-light-driven photocatalyst for the removal of air pollutants.
    关键词: Boron;Nitrogen;Co-doped;TiO_2;Photocatalysis
  • [会议] Optimization of Sampling and Analytical Method in Determination of Airborne Volatile Organic Compounds(VOCs) in China with Thermal Desorption(TD-Gas Chromatography Mass Spectrometry Method
    Volatile organic compounds(VOCs) play an important role in chemical constituents of urban air pollution [1-4]. Under the sunlight, VOCs react with nitrogen oxides lead to the formation of O_3 and SOAs, to pose adverse effects on human health [5]. In this paper, we describe a standardization of the tube sampling, which is coupled with thermal desportion(TD), gas chromatography/mass pectrometry(GC-MS) detection, for quantification of 57 Photochemical Assessment Monitoring Stations(PAMS) mixture compounds. The adsorption tube packed with Tenax TA, Carbograph 1TD and Carboxen 1003 [6], are used to collect PAMS at the flow of 50 ml/min for 60 min. The PAMS standards were diluted from 100 ppbv to 5ppbv. The system was calibrated at four concentrations adjusted with time(2min, 4min, 8min, and 16min). The method showed the linearity over the concentration range from 0.16 to 1.65 ppbv for all target analytes, and the correlation coefficients were higher than 0.996. The method detection limits were below 0.05 ppbv, except ethylene, acetylene, propylene and isobutane. The method precisions are between 0.3% and 20%. Optimal sampling parameters(i.e., sampling duration) and analytical procedures(i.e., desorption temperature and duration) also have been examined. Our results indicate that TD-GC/MS can serve as a simple and rapid sample collection approach to quantify VOCs accurately and precisely in the atmospheric environment.
    关键词: Volatile organic compounds;Multi-sorbent tubes;TD-GC/MS;Air-quality monitoring