g-C3N4/Bi2O2CO32D纳米片复合材料的制备及可见光催化性能研究

采用自组装和化学沉淀法分别制得两种可见光驱动复合材料石墨相氮化碳/碳酸氧铋(g-C_3N_4/Bi_2O_2CO_3).采用X射线衍射光谱(XRD),紫外可见光谱、扫描电镜(SEM)、N_2吸附、电化学阻抗谱(EIS)和X射线光电子能谱(XPS)等分析手段对制备的催化剂进行了表征.结果表明,制备方法对纳米复合材料的晶相、形态及光学性能没有影响,但是影响g-C_3N_4和Bi_2O_2CO_3之间的相互作用力,导致光生电子-空穴对的分离速率存在显著差异.以可见光驱动苯酚和罗丹明B的降解实验为探针反应检测催化剂的光催化性能.实验结果表明自组装法得到的异质结催化剂中相互作用力更强,催化效果最高.O_2-是罗丹明B降解反应的主要活性物种,染料的光敏化、Bi_2O_2CO_3与g-C_3N_4综合效应,导致光生载流子电荷分离效率更高.     

Vibrational frequencies and force constants of N2O4 in complexes with molecules of different solvents determined by Raman spectra andAb initio calculation

The Raman spectra of N₂O₄ solutions in organic solvents have been recorded. The frequencies ofv ₁,v ₂, andv ₃ bands of N₂O₄ increase with increasing solvent electron-donor properties. Especially large changes ofv ₃ N-N stretching band have been observed (254.5 cm^–1 in n-hexane, 276.5 cm^–1 in 1,4-dioxane). The ab initio calculations have shown that the interaction between N₂O₄ and electron-donor molecules causes an increase of N-N and N-O stretching and O-N-O bending force constants of N₂O₄ in agreement with the results of Raman study.     

N2O4 complexes with electron donor molecules. An STO-3G study

The quantum chemical calculations for N₂O₄ complexes with some electron-donor molecules: CH₃NO₂, CH₃COOH, CH₃CN, C₆H₆ and with another molecule of N₂O₄ show that the donor molecule lies under the N₂O₄ plane and its electron-donor atom points to the center of N-N bond of N₂O₄ (or near this center). The electron charge is transferred from the donor to N₂O₄ molecule, mostly to the N-N bond of N₂O₄.     

Co(III) complexes of Me-salpn and Me-salbn and the ring size effect on the coordination modes and electrochemical properties: The crystal structures of trans-[Co(Me-salpn)(py)2]PF6 and cis-α-[Co(Me-salbn)(4-Mepy)2]BPh4 · 4-Mepy

The synthesis and characterization of a series of cobalt(III) complexes of the general type [Co(N₂O₂)(L₂)]⁺ are described. The N₂O₂ Schiff base ligands used are Me-salpn (H₂Me-salpn = N,N′-bis(methylsalicylidene)-1,3-propylenediamine) (1–3) and Me-salbn (H₂Me-salbn = N,N′-bis(methylsalicylidene)-1,4-butylenediamine) (4–5). The two ancillary ligands L include: pyridine (py) 1, 3-metheylpyridine (3-Mepy) 2, 1-methylimidazole (1-MeIm) 3, 4-methylpyridine (4-Mepy) 4 and pyridine (py) 5. These complexes have been characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structures of trans-[Co^III(Me-salpn)(py)₂]PF₆, 1, and cis-α-[Co^III(Me-salbn)(4-Mepy)₂]BPh₄ · 4-Mepy, 4, have been determined by X-ray diffraction. Examination of the solution and crystalline structures revealed that the outer coordination sphere of the complexes exerts a noticeable influence on the inner coordination sphere of the Co(III) ion. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial (R-py)–cobalt bonds. It has also been observed that the Co(III) state is stabilized with increasing the flexibility of the ligand environment.     

Hydrocarbon and fluorocarbon solubility and dilation in poly(dimethylsiloxane): Comparison of experimental data with predictions of the Sanchez–Lacombe equation of state

Sorption and dilation isotherms are reported for a series of gases (N₂, O₂, CO₂), hydrocarbon vapors (CH₄, C₂H₆, C₃H₈), and their fluorocarbon analogs (CF₄, C₂F₆, C₃F₈) in poly(dimethylsiloxane) (PDMS) at 35°C and pressures up to 27 atmospheres. The hydrocarbons are significantly more soluble in hydrocarbon-based PDMS than their fluorocarbon analogs. Infinite dilution partial molar volumes of both hydrocarbons and fluorocarbons in PDMS were similar to their partial molar volumes in other hydrocarbon polymers and in organic liquids. Except for C₂H₆ and C₃H₈, partial molar volume was independent of penetrant concentration. For these penetrants, partial molar volume increased with increasing concentration. The Sanchez–Lacombe equation of state is used to predict gas solubility and polymer dilation. If the Sanchez–Lacombe model is used with no adjustable parameters, solubility is always overpredicted. The extent of overprediction is more substantial for fluorocarbon penetrants than for hydrocarbons. Very good fits of the model to the experimental sorption and dilation data are obtained when the mixture interaction parameter is treated as an adjustable parameter. For the hydrocarbons, the interaction parameter is approximately 0.96, and for the fluorocarbons, it is approximately 0.87. These values suggest less favorable interactions between the hydrocarbon-based PDMS matrix and the fluorocarbon penetrants than between PDMS and hydrocarbons. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3011–3026, 1999     

Preparation of activated carbons and their adsorption properties for greenhouse gases: CH4 and CO2

Three kinds of activated carbons were prepared using coconut-shells as carbon precursors and characterized by XRD, FT-IR and texture property test. The results indicate that the prepared activated carbons were mainly amorphous and only a few impurity groups were adsorbed on their surfaces. The texture property test reveals that the activated carbons displayed different texture properties, especially the micropore size distribution. The adsorption capacities of the activated carbons were investigated by adsorbing CH4, CO2, N2 and O2 at 25 ?C in the pressure range of 0-200 kPa. The results reveal that all the activated carbons had high CO2 adsorption capacity, one of which had the highest CO2 adsorption value of 2.55 mmol/g at 200 kPa. And the highest adsorption capacity for CH4 of the activated carbons can reach 1.93 mmol/g at 200 kPa. In the pressure range of 0-200 kPa, the adsorption capacities for N2 and O2 were increased linearly with the change of pressure and K-AC is an excellent adsorbent towards the adsorption separation of greenhouse gases.     

Formation of different products during photo-catalytic reaction on TiO<Subscript>2</Subscript> suspension in water with and without 2-propanol under diverse ambient conditions

Studies on photo-catalytic reduction of CO₂ using TiO₂ photo-catalyst (0.1%, w/v) as a suspension in water was carried out at 350 nm light. CO₂ from both commercially available source, as well as generated in situ through 2-propanol oxidation, was used for this study. The photolytic products such as hydrogen (H₂), carbon monoxide (CO) andmethane (CH₄) generated were monitored in TiO₂ suspended aqueous solution with and without a hole scavenger, viz., 2-propanol. Similar photolytic experiments were also carried out with varying ambient such as air, O₂, N₂ and N₂O. The yields of CO and CH₄ in all these systems under the present experimental conditions were found to be increasing with light exposure time. H₂ yield in N₂-purged systems containing 2-propanol was found to be more as compared to the without 2-propanol system. The rate of H₂ production in N₂-purged aqueous solutions containing 0.1% TiO₂ suspension were evaluated to be 0.226 and 5.8 μl/h, without and with 0.5 M 2-propanol, respectively. This confirmed that 2-propanol was an efficient hole scavenger and it scavenged photo-generated holes (h⁺), allowing its counter ion, viz., e⁻, to react with water molecule/H⁺ to yield more H₂. The formation of both CO and CH₄ in the photolysis of CO₂-purged aqueous solutions containing suspended TiO₂ in absence of 2-propanol reveal that the generation of CH₄ is taking place mainly through CO intermediate. In presence of air/O₂, the yield of H₂ in the system without 2-propanol was observed to be negligible as compared to the system containing 2-propanol in which low yield of H₂ was obtained with a formation rate of approx. 0.5 μl/h.     

Chemiluminescence in O2 oxidation of organosodium compounds of polycyclic aromatic hydrocarbons and benzophenone

Chemiluminescence (CL) in oxidation of organosodium compounds by O₂ in THF was studied. Emitters of CL are excited complexes of polycyclic aromatic hydrocarbons, excimers¹(R·R)^*. The mechanism of their formation was proposed. The Na⁺, R^.−+O₂ CL system is a unique source for the selective generation of excimers of aromatic hydrocarbons. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 284–288, February, 1997.     

Conversion of NO in NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 Systems by Dielectric Barrier Discharge Plasmas

An experimental study on the conversion of NO in the NO/N₂, NO/O₂/N₂, NO/C₂H₄/N₂ and NO/C₂H₄/O₂/N₂ systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N₂ system, NO decomposition to N₂ and O₂ is the dominating reaction; NO conversion to NO₂ is less significant. O₂ produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O₂ produced decreases at 298 K, but slightly increases at 523 K. In the NO/O₂/N₂ system, NO is mainly oxidized to NO₂, but NO conversion becomes very low at 523 K and over 1.6% of O₂. In the NO/C₂H₄/N₂ system, NO is reduced to N₂ with about the same NO conversion as that in the NO/N₂ system but without NO₂ formation. In the NO/C₂H₄/O₂/N₂ system, the oxidation of NO to NO₂ is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO₂ selectivity in the energy density range of 317–550 J L⁻¹. It finally decreases gradually at high energy density. A negligible amount of N₂O is formed in the above four systems. Of the four systems studied, NO conversion and NO₂ selectivity of the NO/C₂H₄/O₂/N₂ system are the highest, and NO/O₂/C₂H₄/N₂ system has the lowest electrical energy consumption per NO molecule converted.     

含O2高温高压CO2环境中3Cr钢腐蚀产物膜特征

采用高温高压反应釜分别开展3Cr钢在CO2和O2共存、单独CO2和单独O2三种气体条件下的腐蚀实验,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能量色散X射线能谱(EDS)和电化学方法研究了3Cr钢在高温高压含有O2的CO2环境中的腐蚀产物膜特征.结果表明,在含有O2的CO2的条件下,3Cr钢表面腐蚀产物膜疏松多孔,主要成分为FeCO3、Fe3O4和Fe2O3,腐蚀产物中未见明显Cr元素富集,3Cr钢表现出点蚀的腐蚀形态.3Cr钢在高温高压含O2的CO2腐蚀条件下内外膜层电阻(Rf1、Rf2)和电荷传递电阻Rt均比仅含有CO2腐蚀环境的低,双电层电容(Cdl)和内外膜层电容(Cf1、Cf2)均比仅含有CO2腐蚀环境的高.含有O2的CO2条件下,其保护性显著低于单一CO2条件下形成的腐蚀产物膜.提出了在含O2的CO2气体条件下,3Cr钢表面存在由多种物质组成的腐蚀产物,这导致腐蚀产物疏松多孔,不会形成单一CO2条件下存在的显著提高腐蚀产物膜保护性的Cr(OH)3层,从而促进了3Cr钢的析氢腐蚀和酸性介质中的吸氧腐蚀的机理.     

Defect-free asymmetric hollow fiber membranes from Torlon, a polyamide–imide polymer, for high-pressure CO2 separations

Torlon^®, a polyamide–imide polymer, was used for high-pressure CO₂ separations, as it can form inter- and intra-chain hydrogen bonding that may provide stability against plasticization. Asymmetric hollow fiber membranes with a defect-free selective skin were successfully formed from Torlon^® using a dry–wet spinning process. Dope and spinning parameters were optimized to obtain these fibers, which had CO₂/CH₄ selectivity of 44 and O₂/N₂ selectivity of 7.7. These selectivities are about 85% of the intrinsic (dense film) value of 52 for CO₂/CH₄ and 90% of the intrinsic value of 8.3 for O₂/N₂, respectively. Based on analyses presented, the reduced selectivities are attributed to substructure resistance rather than actual skin layer defects. Macrovoids, which compromise the strength of the fiber, were reduced by increasing the polymer concentration. The resulting fiber could withstand up to 2000 psi of N₂, and a CO₂ permeation study indicates that this fiber can perform selective separations under supercritical conditions of 1100 psi of CO₂ at 35 °C.     

Non-catalytic pyrolysis of ethane to ethylene in the presence of CO2 with or without limited O2

Influence of the presence of CO₂, which is a mild oxidant, on the performance of the thermal cracking of ethane to ethylene in the absence or presence of limited O₂ at different temperatures (750–900‡C), space velocities (1500–9000 h^-1) and CO₂/C₂H₆ and O₂/C₂H₆ mole ratios (0–2.0 and 0–0.3 respectively) has been investigated. In both the presence and absence of limited O₂, ethane conversion increases markedly because of the presence of CO₂, indicating its beneficial effect on the ethane to ethylene cracking. The increased ethane conversion is, however, not due to the oxidation of ethane to ethylene by CO₂; the formation of carbon monoxide in the presence of CO₂ is found to be very small. It is most probably due to the activation of ethane in the presence of CO₂.     

Enhancing effect of water vapor on the reduction of lean NOx by ethanol over an Ag/Al2O3 catalyst supported on cordierite honeycomb

The Ag/Al₂O₃ catalyst supported on cordierite honeycomb (Ag/Al₂O₃/ cordierite) is highly active forthe reduction of lean NOx by ethanol. Addition of H₂O enhances the NOx reduction to CO₂ and N₂, and suppresses the formation of by-products such as CO, CH₃CHO and C₂H₄.     

A Novel Solution Method for Interpreting Binary Adsorption Isotherms from Concentration Pulse Chromatography Data

Adsorption separation of carbon dioxide from nitrogen (N₂, which represents air) was investigated by using H-ZSM-5 as the adsorbent with SiO₂/Al₂O₃ ratios of 30 and 280. Pure and binary isotherms at 40°C have been determined experimentally using concentration pulse chromatography.Presently available methods for determining binary isotherms from concentration pulse chromatography data have been reviewed and shown incapable of interpreting this particular binary system. A novel solution method is presented and shown to be superior to the other methods.The binary isotherms for the CO₂-N₂ system show an increase in CO₂ selectivity with increase in surface heterogeneity. The optimal separation factor for H-ZSM-5-30 was found to be 215 at 0.7% CO₂ in the feed, whereas, H-ZSM-5-280 has an optimal separation factor of 48 at 2.7% CO₂ in the feed.     

Study on the interactions between anti-tumor metal complexes and mononucleotides using trans -[en2Os(η2-H2)(CF3SO3)](CF3SO3) as a 1H NMR probe in a competitive mode

The interaction of several anti-tumor metal complexes with dGMP have been investigated using trans-[en₂Os(η²-H₂)]²⁺ as a ¹H NMR probe in a competitive mode. Me₂SnCl₂, Bu₂SnCl₂, Et₂Sn(phen)Cl₂ and Et₂SnCl₂can bind to dGMP mainly via phosphate; Cp₂TiCl₂ binds to dGMP mainly via phosphate and N₇. The binding constant for (CH₃)₂SnCl₂ binding to phosphate of dGMP exceeds 2.71×10⁴. The binding constant for Cp₂TiCl₂ to phosphate is even greater than that of Sn(IV). Cis-platin has high affinity for both N₇ and phosphate, but mainly for N₇. Binding of the probe to N₇ of dGMP reduces the binding affinity for phosphate of the same dGMP molecule by a factor of 5 to 6. Much the same factor is expected to apply to other metals containing agents interacting with dGMP.     

Methane generated during photocatalytic redox reaction of alcohols on TiO2 suspension in aqueous solutions

Studies on the photo-catalytic redox reaction of C1–C3 alcohols such as methanol, ethanol and 2-propanol were carried out in aqueous solution containing TiO₂ photocatalyst (0.1% w/v) as suspension using 350 nm light. Other hydrocarbons such as ethane and ethene in the case of ethanol, and propene in the case of 2-propanol with low yields were produced along with the major photolytic products methane and carbon dioxide. The yields of methane and CO₂ were found to be dependent on the light exposure time and ambient conditions. Methane yields were higher in 2-propanol and ethanol systems than in methanol system, showing their better hole-scavenging properties. In the aerated condition, methane was produced during photolysis of all alcohols in the presence of TiO₂ and the yield was comparable to those observed in the corresponding CO₂-saturated systems. The overall results reveal that the surface adsorbed, as well as in-situ-generated CO₂ from photo-oxidation of alcohols are equally responsible for methane formation through photo-reduction in presence of TiO₂. In the O₂-saturated system, the methane yield was lower as compared to that in aerated system, in contrast to the CO₂ yield. In N₂O-and N₂-purged systems, the yield of methane was observed to be low, inferring that the methane generation has not taken place through photodecomposition/photodissociation of alcohols. Again, photolysis of alcohols without TiO₂ did not generate any methane.     

Carbon Dioxide Reforming of Methane over Ni Catalysts Supported on Al2O3 Modified with La2O3, MgO, and CaO

The preparation of synthesis gas from carbon dioxide reforming of methane (CDR) has attracted increasing attention. The present review mainly focuses on CDR to produce synthesis gas over Ni/MO_x/Al₂O₃ (X = La, Mg, Ca) catalysts. From the examination of various supported nickel catalysts, the promotional effects of La₂O₃, MgO, and CaO have been found. The addition of promoters to Al₂O₃-supported nickel catalysts enhances the catalytic activity as well as stability. The catalytic performance is strongly dependent on the loading amount of promoters. For example, the highest CH₄ and CO₂ conversion were obtained when the ratios of metal M to Al were in the range of 0.04–0.06. In the case of Ni/La₂O₃/Al₂O₃ catalyst, the highest CH₄ conversion (96%) and CO₂ conversion (97%) was achieved with the catalyst (La/Al = 0.05 (atom/atom)). For Ni/CaO/Al₂O₃ catalyst, the catalyst with Ca/Al = 0.04 (atom/atom) exhibited the highest CH₄ conversion (91%) and CO₂ conversion (92%) among the catalysts with various CaO content. Also, Ni/MgO/Al₂O₃ catalyst with Mg/Al = 0.06 (atom/atom) showed the highest CH₄ conversion (89%) and CO₂ conversion (90%) among the catalysts with various Mg/Al ratios. Thus it is most likely that the optimal ratios of M to Al for the highest activities of the catalysts are related to the highly dispersed metal species. In addition, the improved catalytic performance of Al₂O₃-supported nickel catalysts promoted with metal oxides is due to the strong interaction between Ni and metal oxide, the stabilization of metal oxide on Al₂O₃ and the basic property of metal oxide to prevent carbon formation.     

Tunable Viscoelastic Properties of Sodium Polyacrylate Solution via CO2-Responsive Switchable Water

Upon stimulus by CO₂, CO₂-switchable viscoelastic fluids experience a deliberate transition between non-viscous and highly viscous solution states. Despite attracting considerable recent attention, most such fluids have not been applied at a large- scale due to their high costs and/or complex synthesis processes. Here, we report the development of CO₂-switchable viscoelastic fluids using commercially available sodium polyacrylate (NaPAA) and N,N-dimethyl ethanol amine (DMEA)-based switchable water. Upon bubbling CO₂, into the solutions under study, DMEA molecules are protonated to generate quaternary ammonium salts, resulting in pronounced decreases in solutions viscosity and elasticity due to the influence of increased ionic strength on NaPAA molecular conformations. Upon removal of CO₂ via introduction of N₂, quaternary salts are deprotonated to tertiary amines, allowing recovery of fluid viscosity and elasticity to near the initial state. This work provides a simple approach to fabricating CO₂-switchable viscoelastic fluids, widening the potential use of CO₂ in stimuli-responsive applications.     

Mononuclear hydridocarbonyl ruthenium complexes incorporating N2O2 bis-chelating ligands

The reactions of [RuH(CO)Cl(PPh₃)₃] with N,N^′-bis(salicylidine)-hydrazine (H₂bsh) and N,N^′-bis(salicylidine)-p-phenylene diammine (H₂bsp) in presence of KOH in methanol led in the formation of neutral mononuclear complexes with the formulations [RuH(CO)(PPh₃)₂(L)] (LHbsh or Hbsp). These present the first examples where the ligands H₂bsh or H₂bsp provide only two of its available donor sites for interaction with the metal centre. The complexes have been characterized by elemental analyses, FAB-MS, IR, ¹H, ¹³C, ³¹P NMR and electronic spectral studies. Molecular structure of the representative complex [RuH(CO)(PPh₃)₂(Hbsh)] have been determined by single crystal X-ray analysis.     

制备工艺对NiFe2O4分解CO2活性的影响

随着大气中CO2浓度的增加,温室效应日趋严重,促使人们对大气中CO2的转化与消除这一课题更加重视。1990年Yutaka Tamaura[1]发现氧缺位磁铁矿几乎可以100%分解CO2后,为解决温室效应提供了一条新的探索途径。通过对不同铁酸盐MFe2O4(M=Fe,Mn[2],Co[3],Zn[4],Ni[5]等)分解CO2活性的考察,发现铁酸镍在300℃分解CO2的活性比其它铁酸盐都好。NiFe2O4的制备最常采用的是共沉淀法、柠檬酸溶胶凝胶法和水热法,3种方法由于制备