Ca and Sr co-doping induced oxygen vacancies in 3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts for boosting low-temperature oxidative coupling of methane

It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.

Fe-Al_(2)O_(3)/SBA-15催化臭氧氧化水中布洛芬

以嵌段共聚物为模板剂,在酸性条件下水热合成SBA-15.将铁、铝负载于SBA-15表面制备Fe-Al_(2)O_(3)/SBA-15介孔分子筛催化剂,并将其用于催化臭氧氧化水中布洛芬(IBU).透射电子显微镜、X射线衍射、氮气吸附-脱附表征结果表明,铁、铝均匀负载于SBA-15表面,保持SBA-15有序的介孔结构,具有较大的比表面积.不同催化剂活性评价结果表明,铁、铝的负载显著提高SBA-15催化臭氧氧化水中布洛芬的活性,反应60 min后,Fe-Al_(2)O_(3)/SBA-15的TOC去除率为90%,而Al_(2)O_(3)/SBA-15、Fe/SBA-15和SBA-15的TOC去除率分别为65%、50%和36%,单独臭氧氧化仅为26%.实验结果表明,铁、铝的协同作用有利于臭氧分解为羟基自由基、超氧自由基和活性原子氧,布洛芬和小分子有机酸吸附于催化剂表面从而有利于有机物的矿化.催化剂重复利用6次后仍保持较高的催化活性和稳定性.

Effect of Molybdenum Doping on Oxygen Permeation Properties and Chemical Stability of SrCo0.8Fe0.2O3-δ

The phase composition, microstructure, thermal expansion coefficients, oxygen permeation properties and chemical stability of SrCo0.8Fe0.2O3-δ （SCFM） were investigated and compared with those of SrCo0.8Fe0.2O3-δ（SCF）. Single phase SCFM was successfully prepared by a combined EDTA-citric method. SCFM shows a lower thermal expansion coefficient （24× 10^-6-29× 10^-6/K） than SCF between 500 and 1050 ℃, indicating a more stable structure. SCFM shows a high oxygen permeation flux, although the oxygen flux of SCFM decreases slightly because of Mo dopant. Furthermore, it was demonstrated that the doping of Mo in SCF can prevent the order-disorder transition and improves the chemical stability to CO2.

Highly active OMS-2 for catalytic ozone decomposition under humid conditions

Four kinds of cryptomelane-type octahedral molecular sieve(OMS)-2-X(the X represents the molar ratio of KMnO4/MnAc2) were prepared as catalytic materials for ozone decomposition through a one-step hydrothermal reaction of KMnO4 and MnAc2, by changing their molar ratios. These samples were characterized by N2 adsorption–desorption, X-ray di raction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), temperature programmed reduction by H2(H2-TPR) and X-ray photoelectron spectroscopy(XPS). Among them, the OMS-2-0.7 sample showed the best O3 conversion of 92% under high relative humidity(RH) of 90% and gas hourly space velocity of 585,000 h-1. This was accordingly thought as a possible way for purifying ozone-containing waste gases under high RH atmospheres. The e ciency of ozone decomposition of the prepared OMS-2-X sample was found to be related to specific surface area, particle size, surface oxygen vacancies, and Mn3+ cation amounts. The one-step hydrothermal synthesis was shown to be a simple method to prepare the considerably active OMS-2 solids for ozone decomposition.

Methane Oxidation to Synthesis Gas Using Lattice Oxygen of La_(1-x)Sr_xMO_(3-λ)(M =Fe,Mn) Perovskite Oxides Instead of Molecular Oxygen

In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1- SrxMO3-λ (M=Fe, x Mn) perovskite oxides instead of molecular oxygen was investigated. The redox circulation between 11% O2/Ar flow and 11% CH4/He flow at 900℃ shows that methane can be oxidized to CO and H2 with a selectivity of over 90.7% using the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite oxides in an appropriate reaction condition, while the lost lattice x oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite x oxides instead of molecular oxygen to react with methane to synthesis gas in the redox mode.

Oxygen ionic conductivity of a composite electrolyte SDC-LSGM prepared via glycine-nitrate process

Ce0.8Sm0.2O1.9-δ-La0.9Sr0.1Ga0.8Mg0.2O3-δ（SDC-LSGM）is prepared by the glycine-nitrate process（GNP）.SDC-LSGM composite electrolyte samples with different weight ratios are prepared by the co-combustion method so as to obtain homogeneous nano-sized precursor powders. The X-ray diffraction （XRD） and the scan electron microscope （SEM） are used to investigate the phases and microstructures. The measurements and analyses of oxygen ionic conductivity of SDC-LSGM are carried out through the four-terminal direct current （DC） method and the electrochemical impendence spectroscopy, respectively. The optimum weight ratio of SDC-LSGM is 8∶2, of which the ionic conductivity is 0.113 S/cm at 800℃ and the conductivity activation energy is 0.620 eV. The impendence spectra shows that the grain boundary resistance becomes the main barrier for the ionic conductivity of electrolyte at lower temperatures. The appropriate introduction of LSGM to the electrolyte SDC can not only decrease the electronic conductivity but also improve the conditions of the grain and grain boundary, which is advantageous to cause an increase in oxygen ionic conductivity.

Preparation and oxygen permeability of Bi_(26)Mo_(10)O_(69) porous layer modified ionic-electronic mixed conductor on air side

Bi26MO10O69 nanopowder was prepared by hydrothermal method and used as a surface modification material for oxygen separation membrane to enhance oxygen permeability. Thermal decomposition behavior and phase variation of the precursor were investigated by thermal analyzer （TG-DSC） and high-temperature X-ray diffraction （HT-XRD）. Bi26MO10O69 porous layer was coated on the air side of BaCo0.7Fe0.2Nb0.1O3-δ （BCFN） oxygen permeable membrane by dipping method. In the partial oxidation experiment of coke oven gas （COG）, the Bi26Mo10O69-coated BCFN membrane exhibits higher oxygen permeability and CH4 conversion than the uncoated BCFN membrane. When the thickness of BCFN membrane was 1 mm and the COG and air fluxes were 120 and 100 mL/min, the oxygen permeation flux reached 16.48 mL/（min.cm^2） at 875℃, which was 16.96% higher than the uncoated BCFN membrane. Therefore, Bi26MoloO69 porous layer on the air side will be promising modification coating on the oxygen permeability of BCFN membrane.

Novel cobalt-free tantalum-doped perovskite Ba Fe_(1-y)Ta_yO_(3-δ)with high oxygen permeation

Cobalt-free perovskite-type oxides BaFel_yTayO3-6 （0 _〈 y -〈 0.2） were synthesized via a simple solid state reac- tion. The cubic perovskite structure can be obtained when y is over 0.1. BaFeo.Ta0.lO3-6 （BFT0.1） membrane shows the highest oxygen permeation flux, which can reach 1.6 ml. min- 1. cm-2 at 950 ℃ under the gradient of air/He. The O2-TPD results reveal that BaFe0.9Ta0.lO3-a material shows an excellent reversibility and phase structure stability in air. The oxygen permeation flux is limited by the bulk diffusion when the membrane thick- ness is over 0.8 mm, and it is limited by both the bulk diffusion and the surface exchange when the membrane thickness is below 0.5 mm. Stable oxygen permeation fluxes are obtained during 180 h operation.

Oxygen Isotope Records of Core 8KL of the South China Sea and Sea - level Change

Based on a comparison between the oxygen isotope records of benthic and plank tonic foraminifers from core 8KL of the South China Sea and sea-level change records derived from the Huon Peninsula, New Guinea, it is found that both records are very similar from 72 K a B.P. to the present, especially for the benthic oxygen isotope record. The linear regression shows that δ18O changes (0.9995‰ for benthic foraminifers and 1.022‰ for planktonic foraminifers) are equal to 100 m in sea-level fluctuation. After making temperature correction in the δ18O record of benthic foraminifers from 72 to 120 Ka B.P., the curve of sea-level oscillation of the South China Sea since 186 Ka B.P. has been reconstructed. The lowermost sea - level that occurred in the last glacial maximum and oxygen isotope stage 6 is approximately - 130 m.

SrCo_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ) perovskite stabilized by niobium for oxygen permeation

The effect of Nb doping on the oxygen permeation and stability of SrCo_(0.8)Fe_(0.2)O_(3-δ)(SCFO) was investigated comprehensively.Cubic perovskite phase was formed in SrCo_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ)(SCFNO).The SCFNO with a thickness of 1 mm had a high level of oxygen permeation flux of 1.4 ml.min^(-1).cm^(-2) at 850 ℃ under air/He gradient.The bulk diffusion is the rate-limiting step in overall oxygen permeation mechanism for SCFNO when the thickness is higher than 1.0 mm.The partial substitution of Nb for Co suppresses the transition of oxygen vacancies order/disorder proven by DSC measurement and enhances the phase stability under low oxygen partial pressure.During long-term tests under low oxygen pressure,the SCFNO exhibites structural stability and stable oxygen permeation.It is proved that substitution of Nb for Co is an effective way to improve the properties of SCFO.

Ozone electrogeneration on Pt-TaO_y sol-gel film modified titanium electrode: Effect of electrode composition on the electrocatalytic activity

This work examines the ozone electrogeneration （OE） at a binary coating of different nominal compositions （Pt）x-（TaOy）（100-x）, where x （percentage in the precursor solution） varied between 1% and 100%, coated on titanium substrate prepared by a sol-gel technique, The OE is performed in an artificial tap water at room temperature （25 ℃）. The percentages of Pt and Tatu in the coating significantly affect the electro- catalytic activity towards oxygen evolution. The oxygen evolution was retarded to a different extent based on the electrode composition. The largest retardation was obtained at the （Pt）10-（TaOy）90 electrode （ca. 480 mV positive shift） as compared with the （Pt）100-（TaOy）0 electrode. This was reflected in a high current efficiency （CE） of OE （ca. 19.3%） at the former electrode. This value is considered to be among the highest values reported for OE at 25℃ in neutral media. The composite electrodes were characterized by voltammetric and surface techniques. A plausible explanation for the change of the efficiency of OE with the electrode composition is given based on the electrochemical results.

Promoting surface reconstruction of NiFe layered double hydroxides via intercalating[Cr(C_(2)O_(4))_(3)]^(3-)for enhanced oxygen evolution

Rationally manipulating surface reconstruction of catalysts for water oxidation,inducing formation and dynamic accumulation of catalytically active centers still face numerous challenges.Herein,the introduction of[Cr(C_(2)O_(4))_(3)]^(3-)into NiFe LDHs by intercalation engineering to promote surface reconstruction achieves an advanced oxygen evolution reaction(OER)activity.In view of the weak electronegativity of Cr^(3+) in[Cr(C_(2)O_(4))_(3)]^(3-),the intercalation of[Cr(C_(2)O_(4))_(3)]^(3-)is expected to result in an electron-rich structure of Fe sites in NiFe LDHs,and higher valence state of Ni can be formed with the charge transfer between Fe and Ni.The optimized electronic structure of NiFe-[Cr(C_(2)O_(4))_(3)]^(3-)-LDHs with more active Ni^(3+) species and the expedited dynamic generation of Ni^(3+) (Fe)OOH phase during the OER process contributed to its excellent catalytic property,revealed by in situ X-ray absorption spectroscopy,Raman spectroscopy,and quasi-in situ X-ray photoelectron spectroscopy.With the modulated electronic structure of metal sites,NiFe-[Cr(C_(2)O_(4))_(3)]^(3-)-LDHs exhibited promoted OER property with a lower overpotential of 236 mV at the current density of 10 mA cm^(-2).This work illustrates the intercalation of conjugated anion to dynamically construct desired Ni^(3+) sites with the optimal electronic environment for improved OER electrocatalysis.

Effects of Praseodymium Doping on Conductivity and Oxygen Permeability of Cobalt-Free Perovskite-Type Oxide BaFeO3-δ

Among the perovskite-type oxides with symmetrical structure applied in oxygen permeable membranes, cubic phase structure is the most favorable for oxygen permeation. In order to stabilize the cubic perovskite structure of BaFeO3-δ material at room temperature, iron was partially substituted by praseodymium. BaFe1-yPryO3-δ powders were synthesized by a solid state reaction method, and sintered samples were prepared from the synthesized BaFe1-yPryO3-δ powders. X-ray diffraction results reveal that the BaFe1-yPryO3-δ samples remain cubic structure at praseodymium substitution amount of y 0.05, 0.075, 0.1. Scanning electron microscope observation indicates that the sintered samples contain only a small amount of enclosed pores and the grain size of BaFe1-yPryO3-δ increase monotonically with the increase of the praseodymium doping amount, praseodymium doping promotes the grain size growth. Tests of electrical conductivity and oxygen permeation flux show that praseodymium doping improves the conduction properties of BaFe1-yPryO3-δ and BaFe0.9Pr0.1O3-δ composition has an electrical conductivity of 6.5 S/era and an oxygen permeation of 1.112 mL/（cm^2.min） at 900 ℃, respectively. High temperature XRD in- vestigation shows that the crystal structure of BaFe0.975Pr0.025O3-δ membrane completely transform to cubic phase at 700℃. The present test results have shown that partially substitution of Fe by praseodymium in BaFeO3 can stabilize the cubic structure and improve the properties.

Test on oxygen and benzene contents in gasoline by mid-infrared spectroscopy

This paper aims at testing oxygen and benzene contents in gasoline by mid-infrared spectroscopy.The experimental results prove that infrared spectroscopy(IR)is reliable.Compared with gas chromatography(GC)technology,this paper draws a conclusion that IR has several advantages,including rapid analysis,excellent repeatability and low analysis cost.

TiO_(2)/γ-Al_(2)O_(3)催化臭氧氧化水中布洛芬

以葡萄糖为模板,采用蒸发诱导自组装法合成了γ-Al_(2)O_(3)介孔催化剂,以钛酸四正丁酯(TBOT)为原料制备TiO_(2)/γ-Al_(2)O_(3)催化剂,并将其用于催化臭氧氧化水中布洛芬(IBU).X射线衍射、扫描电子显微镜、氮气吸附-脱附和吡啶红外光谱表征结果表明,TiO_(2)均匀负载于γ-Al_(2)O_(3)表面,保持γ-Al_(2)O_(3)有序的介孔结构,具有较大的比表面积和更多的Lewis酸性位.不同催化剂活性评价结果表明,TiO_(2)的负载显著提高γ-Al_(2)O_(3)催化臭氧氧化水中布洛芬的活性,反应60 min,TiO_(2)/γ-Al_(2)O_(3)催化剂的TOC去除率达到80%,而γ-Al_(2)O_(3)、TiO_(2)及单独臭氧氧化过程中TOC去除率则分别达到62%、32%及26%.电子顺磁共振和原位激光显微拉曼光谱实验结果表明,Lewis酸性位为臭氧高效分解的活性位,活性原子氧和过氧物种是TiO_(2)/γ-Al_(2)O_(3)催化臭氧氧化反应的活性氧物种,有利于有机物的矿化,从而表现出最高的催化活性.重复利用实验结果表明,TiO_(2)/γ-Al_(2)O_(3)催化剂具有较长的使用寿命.

Electrocatalytic Reduction of Oxygen at Perovskite (BSCF)-MWCNT Composite Electrodes

A composite paste electrode based on Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)—initially synthesized by solgel method—and multiwall carbon nanotube (MWCNT) as a cathode in fuel cells is developed. The composite pastes are prepared by the direct mixing of BSCF:MWCNT at 90:10, 80:20 and 70:30 (% w/W). These electrodes are then characterized by the x-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherm, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The XRD and SEM confirm the inclusion and the uniform dispersal of the MWCNT within BSCF, respectively. The nitrogen adsorption isotherm study shows that the porosity of the composite paste electrode has been improved by two-fold from the BSCF electrode. The EIS and CV demonstrate that the higher ratios of MWCNT in the composites are critical in improving the electronic conductivity as well as the kinetics. It is also noticeable that the electrode has increased the catalysis of oxygen in 0.1 M KOH (pH 12.0). Cyclic voltammetric studies on the oxygen reduction reaction (ORR) suggest that the incorporation of MWCNT is vital in improving the electrode (cathode) properties of a fuel cell.

Conjugated polymerized bimetallic phthalocyanine based electrocatalyst with Fe-N_(4)/Co-N_(4) dual-sites synergistic effect for zinc-air battery

The bifunctional oxygen catalyst is essential for zinc-air batteries(ZABs).Here,an efficient bifunctional oxygen catalyst,PPcFeCo/3D-G,is obtained throughπ-πinteraction between the conjugated polymerized iron-cobalt phthalocyanine(PPcFeCo)with excellent thermal stability and three-dimensional graphene(3D-G).The bimetallic synergistic effect of PPcFeCo,verified by DFT(Density functional theory)calculation,andπ-πinteractions enhances the catalytic activity and durability of the PPcFeCo/3D-G.Regarding electrochemical performance,the PPcFeCo/3D-G with a high electron transfer number(3.98,@0.768 V vs.RHE)has excellent half-wave potential(E_(1/2)=0.890 V vs.RHE)and exhibits outstanding reversibility(ΔE=0.700 V,ΔE=Ej=10-E_(1/2)).The liquid ZAB(LZAB)employed PPcFeCo/3D-G displays a high power density(222 m W cm^(-2)),a specific capacity(792 m A h g-1),and excellent durability(120 h).This work has guiding significance for the preparation of high-efficiency bifunctional catalysts.

Effect of Temperature on the Reaction of 2-(N-acetylamine)-3-(3,5-di-<i>tert</i>-butyl-4-hydroxyphenyl)-propionic Acid with Oxygen in an Alkaline Condition

Results of oxidation 2-(N-acetylamine)-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid oxygen depend on temperature. At 55℃?- 60℃, 2,4-di-tert-butylbicyclo(4,3,1)deca-4,6-dien-8-(N-acetylamine)-3,9-dion-1-oxa is formed. The constitution is based on dates of spectrums 1Н and 13С NMR. At 95℃?- 97℃, mixtures of 2,4-di-tert-butylbicyclo(4,3,1)deca-4,6-dien-8-(N-acetylamine)-3,9-dion-1-oxa and of 6,8-di-tert-butyl-3-(N-acetylamine)spiro(4,5)deca-1-oxa-5,8-dien-2,7-dione are produced. Structures are calculated by the method of Hartrii-Foka. Values of enthalpies and of entropies allow to assume dynamic isomerism.

基于臭氧-三维电极工艺的油田采出水处理技术研究

为确定臭氧-三维电极工艺对油田采出水的处理效果,以某联合站采出水为研究对象,通过单因素实验确定采出水化学需氧量(COD)的变化范围,利用响应曲面实验设计确定最佳工艺条件,并探讨联合工艺的协同效应和作用机理。结果表明,影响程度从大到小依次为极板间距、电流密度、活性炭填充量、臭氧曝气量;并且极板间距和电流密度、极板间距和活性炭填充量的交互影响显著;当极板间距2.9 cm、电流密度8.2 mA/cm^(2)、活性炭填充量20.5 g/L、臭氧曝气量31.2 mL/min时,COD的去除率最高为94.83%;联合工艺符合一级反应动力学方程,其速率常数远大于单独工艺速率常数的线性加和,说明两种工艺发生了协同促进效应,强化了有机物的去除速率。