Theoretical investigations on the SO2 + HO2 reaction and the SO2–HO2 radical complex

The mechanism of the SO₂ + HO₂ reaction was studied theoretically for the first time. Three product channels were revealed, namely, O₂ + HOSO, O₂ + HSO₂, and OH + SO₃. The O₂ + HOSO channel dominates the reaction under combustion conditions. A five-member-ring complex [SO₂–HO₂] exists at the entrance of the reaction. The structure and binding energy (D_e and D₀) of the SO₂–HO₂ complex have been calculated. In view of D₀ = 21.2 ± 2.0 kJ mol⁻¹, the SO₂–HO₂ complex should be stable at low temperature. The infrared spectra and frequency shifts were calculated for both SO₂–HO₂ and SO₂–DO₂, and compared with the available experimental data.     

High temperature reaction of SiCl4 and O2 in quartz tubes

The reaction between SiCl₄ and O₂ at 1 atm between 25 and 1200°C has been followed by mass spectrometry. Below 600°C no reaction with O₂ is noted. Above 600°C the reaction proceeds in two steps. Between 800 and 1000°C the ²⁸Si/³²O₂ peak height ratio is constant with no evolution of Cl₂. It is suggested that silicon oxychlorides are being formed in this temperature regime. Above 1000°C the reaction between SiCl₄ and O₂ intensifies with concomitant production of Cl₂. It is suggested that above 1000°C the reaction SiCl₄ + O₂ → SiO₂ + Cl₂ becomes important.

At low temperatures (<800°C) adsorbed H₂O and OH groups from the surface of the fused silica tube react with SiCl₄ to form HCl. The importance of this reaction decreases with increasing temperature. The increased production of HCl above 1000°C is ascribed to H₂O and H₂ diffusing from the tube.     

Se和SeO2在O2/CaO (001)表面吸附反应的第一性原理研究

基于密度泛函理论的第一性原理和平板模型构造了最稳定的O₂/CaO（001）表面,通过优化Se和SeO₂在此表面可能的初始吸附结构得到最佳吸附构型,分析了Se原子在O₂/CaO（001）表面向SeO₂的转化。结果表明,Se原子在O₂/CaO（001）表面的稳定吸附构型主要有两种,即O-Se-O和O-O-Se基团,其中,O-O-Se基团的Se终端具有一定化学活性;Se在O₂/CaO（001）表面向SeO₂转化所需反应能垒小于均相条件下生成SeO₂所需反应能垒,表明CaO不仅作为吸附剂,也能促进Se向SeO₂的转化;SeO₂分子在O₂/CaO（001）表面发生化学吸附时,吸附基底的部分价电子转移至SeO₂分子轨道中。     

Membrane purification of Cl2 gas: I. Permeabilities as a function of temperature for Cl2, O2, N2, H2 in two types of PDMS membranes

Permeability (P) of Cl₂, O₂, N₂ and H₂ was measured in polydimethylsiloxane (PDMS) composite membranes with two different degrees of cross-linking. The permeability was measured in the low pressure range (1–3 bar absolute) over a fairly large temperature range 35–120°C. The functionalities of the membranes were compared on the basis of permeation rate and ability to separate the gases Cl₂–O₂. These results are part of an extensive survey where perfluorinated and carbon membranes are also included (not reported here). The purpose of the project is to develop an industrial membrane with high permselectivity for either O₂ or Cl₂ (depending on the type of membrane) at temperatures preferably above 70°C. Process conditions are set in an industrial project. The PDMS membranes are good candidates for this separation, having a high permeation rate for Cl₂ and a selectivity of Cl₂/O₂ in the range of 8–25 depending on temperature. Durability of the PDMS membranes in this aggressive environment is found to be very dependent on process conditions and on how the material is polymerized and cured. For documentation of durability, various silicones were tested; these results are to be reported separately.     

O2/CO2气氛下污泥/煤混燃中半挥发性重金属的释放特性

在固定床焚烧实验装置上,采用正交实验法研究了焚烧温度(t_c)、污泥掺混比(X_s)、O_2体积分数(φ_(O2))、初始含水率(φ_(H2O))、焚烧时间(τ)和含氯量(φ_(Cl))六个因素对O_2/CO_2气氛下污泥/煤混燃中半挥发性重金属(Zn、Pb、Cd、Cu、Ni和Cr)释放特性的影响。结果表明,六种因素对重金属释放率影响程度排序为t_cX_sφ_(H2O)φ_(O2)≈τφ_(Cl)。相同焚烧工况下,Zn释放率最大,Pb和Cd次之,Cu、Ni和Cr较小。提高温度会促进重金属释放,且高温(1000-1100℃)对重金属释放的影响显著强于低温(700-900℃)。随着温度由700℃升高至1100℃,Zn和Pb释放率分别由36.1%和12.2%上升至70.9%和63.5%,Cd在900℃下达到40.0%的最大释放率,而Cu、Ni和Cr释放率大都维持在20.0%以下,温度对重金属释放率影响程度排序为PbZnCdCuCrNi。重金属释放率随着污泥掺混比增加逐渐下降,却随着初始含水率增加呈现波浪式变化趋势,且在30%O_2体积分数下重金属释放率取得最小值。焚烧时间和含氯量对Pb释放的影响程度显著强于其他五种重金属。O_2/CO_2气氛下污泥/煤混燃的最佳工况为:焚烧温度为900-1000℃、污泥掺混比为25%左右、O_2体积分数为30%、初始含水率小于10%,并尽可能的缩短焚烧时间。     

Properties of Pd---Au and Pt---Cu alloy surfaces for the adsorption and catalytic reduction of O2 and NO by H2

The adsorption and catalytic properties of Pd---Au and Pt---C alloy surfaces were investigated under low pressure conditions, with the real surface composition being monitored using Auger electron spectroscopy. Flash desorption experiments on O₂ and NO, and steady state kinetic experiments involving the reduction of these substances by H₂ were performed on polycrystalline alloy surfaces. For the Pd---Au system, O₂ desorption was promoted by gold, as shown by the shift of O₂ desorption toward lower temperature and a linear decrease in the saturated amount of O₂ adsorption with increase in gold content. For the Pt---Cu system, O₂ desorption was retarded by copper i.e. the O₂ desorption temperature shifted upward with increase in copper content. In both the alloy systems, catalytic activities for the above reactions were significantly suppressed by the addition of gold or copper to the platinum group metals. The drop was more pronounced for NO reduction, suggesting that a larger ensemble of active platinum group metal atoms are necessary for NO dissociation.     

低阶煤半焦利用热重在O2/CO2、O2/N2和O2/Ar气氛下燃烧特性研究

利用热重研究了两种中国西北典型低阶煤半焦的燃烧特性。探究了不同气氛（O₂/CO₂、O₂/N₂和O₂/Ar）和不同氧气浓度对其燃烧特性的影响。实验结果表明,无论是反应气氛还是氧气浓度都会对低阶煤半焦的燃烧产生影响。相比于N₂和Ar,CO₂明显有利于燃烧反应进行：当反应气氛由O₂/CO₂变为O₂/Ar时,两种不同低阶煤半焦的燃尽温度分别升高了63.7和68.8℃;而当反应气氛由O₂/CO₂变为O₂/N₂时,两种不同低阶煤半焦的燃尽温度分别升高了135.9和129.6℃。在研究范围内,氧气浓度的提高也能明显提高半焦的燃烧性能。与此同时,半焦燃烧特性的动力学分析表明,随着氧气浓度提高,两种半焦燃烧反应的表观活化能E和指前因子A均呈增大趋势。通过对E和A两者关系的分析结果表明,半焦富氧燃烧的活化能和指前因子存在动力学补偿效应。     

The polymerization of [P(O2C12H8)(N3)] and the formation of soluble and insoluble poly(2,2′-dioxy-1,1′-biphenylphosphazene)

The phosphorus azide [P(O₂C₁₂H₈)(N₃)] [(O₂C₁₂H₈) = 2,2′-dioxy-1,1′-biphenyl] undergoes a solid state polymerization at 30 °C giving a separable mixture of the polyphosphazene {[NP(O₂C₁₂H₈)]}_n with a M_w in the range of 10⁴, together with a fraction of small and large cyclic spirophosphazene oligomers {[NP(O₂C₁₂H₈)]}_n, and an insoluble polymeric material with a very high char forming tendency, consisting very likely on a network of large interlooped cyclic oligomers and polymers of overall composition [NP(O₂C₁₂H₈)]_n. The reaction proceeds with smooth though irregular release of nitrogen at first but tending to abrupt accelerations ending in an explosion. The later outcome is more likely in scales of 10–50 g, and results in a decrease in the yield of the soluble polymer and a large increase in the yield of the polymeric matrix.     

An electron transfer mechanism of O4 formation

A resonating valence bond electron transfer mechanism of combining two O₂ molecules to form an O₄ molecule is presented. The predicted molecular states of the reaction path D_∞h→C_2v→D_2h are supported by the present ab initio molecular orbital calculations. The CASPT2 BSSE calculations yield a stable diamagnetic D_2h O₄ molecule with a very weak chemical bond between the monomers, in good agreement with experiments. A low activation barrier energy of 26 cal/mol for the O₄ formation is found.     

Synthesis and characterization of P2O5–SiO2–X (X = phosphotungstic acid) glasses as electrolyte for low temperature H2/O2 fuel cell application

A new class of proton conducting glass membranes for hydrogen fuel cell applications are being developed using phosphotungstic acid. These glasses are being design to yield high proton conductivities could be potential substitutes for electrolytes in H₂/O₂ fuel cell. P₂O₅–SiO₂–PWA glasses have been non-crystalline phases confirmed by structural studies. The glass materials showed good mechanical and thermal stability, and also found a maximum proton conductivity of 9.1 × 10⁻² S/cm at 90 °C and 30% RH. The average pore size less than 5 nm was determined by Barrett–Joyner–Halenda (BJH) desorption method. The electrochemical activity was investigated by polarization curves and current–voltage profiles. A maximum power density value of 10.2 mW/cm² was obtained using 0.15 mg/cm² of Pt/C loaded on electrode and 5P₂O₅–87SiO₂–8PWA glasses at 30 °C and 30% humidity.     

Ab initio study of the two competitive channels HO2 + H → H2 + O2 and HO2 + H → H2O + O

Saddle point geometries and barrier heights have been calculated for the H abstraction reaction HO₂(²A″)+H(²S) → H₂(¹Σ⁺_g)+O₂(³Σ⁻_g) and the concerted H approach-O removing reaction HO₂ (²A″)+H(²S) → H₂O(¹A₁)+O(³P) by using SDCI wavefunctions with a valence double-zeta plus polarization basis set. The saddle points are found to be of C_s symmetry and the barrier heights are respectively 5.3 and 19.8 kcal by including size consistent correction. Moreoever kinetic parameters have been evaluated within the framework of the TST theory. So activation energies and the rate constants are estimated to be respectively 2.3 kcal and 0.4×10⁹ ℓ mol⁻¹ s⁻¹ for the first reaction, 20.0 kcal and 5.4.10⁻⁵ ℓ mol⁻¹ s⁻¹ for the second. Comparison of these results with experimental determinations shows that hydrogen abstraction on HO₂ is an efficient mechanism for the formation of H₂ + O₂, while the concerted mechanism envisaged for the formation of H₂O + O is highly unlikely.     

流化床O2/CO2气氛下添加石灰石对燃煤PM2.5的控制

采用小型流化床研究了在O₂/CO₂气氛下添加石灰石对PM_2.5(空气动力学直径小于2.5 μm的颗粒物)的控制.实验采用荷电低压撞击器(ELPI)采集和分析燃烧后的PM_2.5.结果表明,添加石灰石是燃烧过程中影响PM_2.5生成的重要因素.添加石灰石后,生成PM_1.0的数量浓度均降低,而PM_1.0~2.5的数量浓度均略有增加;PM_2.5质量粒径分布均呈双峰分布,峰值分别出现在0.2和2.0 μm左右.随着Ca/S物质的量比的增加,PM_2.5中Si、Na、K、S和Cu的含量呈减少的趋势;随着颗粒粒径的减小,S、Cu、K和Na的含量有增大的趋势,而Si的含量有减少的趋势.     

Solid state photodecomposition studies of K4Ti(O2)4·2H2O, K3Ta(O2)2F4 and K2V2O3(O2)2F2

The compounds K₄Ti(O₂)₄·2H₂O, K₃Ta(O₂)₂F₄ and K₂V₂O₃(O₂)₂F₂ undergo photolysis in the solid state. The photolysis kinetics obey the parabolic rate equation p = kt^1/2 and indicate a monoexcitation process for the photolysis. These features are similar to those reported previously for peroxo complexes. The mechanism of evolution of oxygen reported earlier appears to be the same in all these solids.     

Rate coefficients for the reactions of cyclohexadienyl (c-C6H7) radicals with O2 and NO at room temperature

Rate coefficients for the reactions of cyclohexadienyl (c-C₆H₇) radicals with O₂ and NO were measured at 296 ± 2 K. The c-C₆H₇ radicals were detected selectively by laser-induced fluorescence. The rate coefficient for the reaction of c-C₆H₇ with O₂, (4.4 ± 0.5) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, was independent of the bath-gas (He) pressure (13–80 Torr). In the reaction of c-C₆H₇ with NO, thermal equilibrium among c-C₆H₇, NO, and C₆H₇NO was observed. The forward and reverse reactions were in the falloff region, and the equilibrium constant was (1.5 ± 0.6) × 10⁻¹⁵ cm³ molecule⁻¹.     

Photochemistry of perfluoroacyl halides in the presence of O2 and CO

Photolyses of CF₃C(O)X and C₂F₅C(O)X (X=Cl, F) at 254 nm in the presence of O₂ yield the perfluorinated radicals C₂F₅O (C₂) and CF₃O (C₁), respectively. The C₂ radicals decompose to give CF₃ radicals:

C₂F₅O→CF₃+CF₂O

which, in turn, react with O₂ leading to the formation of C₁ radicals. When in addition to O₂, CO is present, the C₁ radicals react with it leading to its catalytic oxidation to CO₂. The trioxide CF₃OC(O)O₃C(O)OCF₃ was observed following the photolysis of all four halides in the presence of O₂ and CO.

The other radical partners coming from the initial step in the photolysis (XC(O)) as well as the products of their reaction with O₂ (XC(O)O_y, y=1, 2) do not react with CO but when X=F they lead to the formation of a new stable peroxy molecule with the formula CF₃OC(O)O₂C(O)F. Some of the properties of this new molecule, its stability and its IR features are presented in this work.     

TiCl4(THF)2 impregnation on a flat SiOx/Si(1 0 0) and on polycrystalline Au foil: determination of surface species using XPS

TiCl₄(THF)₂ was impregnated by spin-coating on a Si(1 0 0) wafer covered with a thin SiO_x layer and on a polycrystalline Au foil. The nature of the surface species was determined at room temperature and after annealing, by X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). A mixed Si:O:Ti interfacial layer was formed on the silicon substrate while in the case of Au, TiOCl_x and TiO_x were the main surface species at room temperature. Annealing at 723 K leads to the total desorption of the Cl atoms, and in both cases a significant amount of Ti atoms was reduced to the Ti³⁺ state. AFM measurements revealed a homogenous distribution of nano-sized TiO_x clusters with semi-ellipsoid shape and increased contact area with the underlying silica.     

贫煤O_2/CO_2气氛下燃烧时内在矿物质对SO_2和NO_x排放特性的影响

利用管式炉反应器在550-1 000℃对长治贫煤和脱矿物质煤分别在空气和O_2/CO_2气氛进行了燃烧实验。利用XRF、XRD等分析手段,对煤样的基本性能进行了分析表征,并采用热分析仪(TG-DTG)以及傅里叶红外气体分析仪(AntarisIGS)对贫煤燃烧过程中的燃烧特性和SO_2和NO_x释放规律进行了研究。结果表明,与原煤相比,脱矿物质煤的着火温度和燃烬温度有所降低;O_2/CO_2气氛下,原煤和脱矿物质煤的着火温度和燃烬温度都升高,说明当O_2浓度为20%时,空气气氛比O_2/CO_2气氛更易于着火和燃烬。此外,与长治原煤相比,脱矿物质煤在相同条件下燃烧时SO_2的释放量明显提高,而NO_x的释放量却有所降低。O_2/CO_2气氛下原煤燃烧时SO_2浓度比空气气氛下的要高,而脱矿物质煤燃烧时释放的SO_2浓度明显比空气气氛下的低;O_2/CO_2气氛下原煤和脱矿物质煤燃烧时释放的NOx浓度比空气气氛下燃烧时释放的NO_x浓度要低。     

Simultaneous monitoring of pH, CO2 and O2 using an optical imaging fiber

The interdependence of pH, CO₂ and O₂ during chemical and biochemical processes has driven the need to monitor them simultaneously, continuously and in situ, in order to exert better control over such reactions. We present the fabrication and performance of a multi-analyte imaging fiber sensor that allows pH, CO₂ and O₂ to be monitored simultaneously with rapid response. Sensing elements are fabricated by covalently immobilizing fluorescent indicators within polymer matrices via photopolymerization, resulting in the formation of distinct regions of analyte-sensitive polymer at the fiber's distal end. The multianalyte sensor's working range is 0%–100% for O₂ and 0%–10% for CO₂ in the pH range 5.5–7.5. The sensor was used to monitor the pH, CO₂ and O₂ changes during a beer fermentation.     

The electronic and reduction properties of Ce0.75Zr0.25O2(1 1 0)

The electronic and chemical reduction properties of the Ce_0.75Zr_0.25O₂(1 1 0) surface are presented based on DFT + U calculations, i.e. density functional theory with the inclusion of on-site Coulomb interaction. Experimental studies in the literature have shown that redox activity and thermal stability of ceria are significantly enhanced by the presence of zirconia dopants. In the present theoretical study it is found that mixing zirconia into ceria leads to important structural and chemical consequences such as non-equivalent O atoms at the surface, lower reduction energy and larger surface relaxation. The electronic mechanisms behind these modifications are analysed.     

Hydrogenmaleato bridged supramolecular double chains via π–π stacking interactions: syntheses, crystal structures and magnetic properties of ∞[Cu(phen)X(HL)2/2] with X=Cl (1), NO3 (2) and H2L=maleic acid

Two novel hydrogen maleato (HL) bridged Cu(II) complexes _∞¹[Cu(phen)Cl(HL)_2/2] 1 and _∞¹[Cu(phen)(NO₃)(HL)_2/2] 2 were obtained from reactions of 1,10-phenanthroline, maleic acid with CuCl₂·2H₂O and Cu(NO₃)₂·3H₂O, respectively, in CH₃OH/H₂O (1:1 v/v) at pH=2.0 and the crystal structures were determined by single crystal X-ray diffraction methods. Both complexes crystallize isostructurally in the monoclinic space group P2₁/n with cell dimensions: 1 a=8.639(2) Å, b=15.614(3) Å, c=11.326(2) Å, β=94.67(3)°, Z=4, D_calc=1.720 g/cm³ and 2 a=8.544(1) Å, b=15.517(2) Å, c=12.160(1) Å, β=90.84(8)°, Z=4, D_calc=1.734 g/cm³. In both complexes, the square pyramidally coordinated Cu atoms are bridged by hydrogen maleato ligands into 1D chains with the coordinating phen ligands parallel on one side. Interdigitation of the chelating phen ligands of two neighbouring chains via π–π stacking interactions forms supramolecular double chains, which are then arranged in the crystal structures according to pseudo 1D close packing patterns. Both complexes exhibit similar paramagnetic behavior obeying Curie–Weiss laws χ_m(T−θ)=0.414 cm³ mol⁻¹ K with the Weiss constants θ=−1.45, −1.0 K for 1 and 2, respectively.