Experimental study on the effect of H_(2)O and O_(2) on the degradation of SF_(6) by pulsed dielectric barrier discharge

SF_(6) has excellent insulation performance and arc extinguishing ability,and is widely used in the power industry.However,its global warming potential is about 23,500 times that of C0_(2),it can exist stably in the atmosphere,it is not easily degradable and is of great potential harm to the environment.Based on pulsed dielectric barrier discharge plasma technology,the effects of H_(2)O and 0_(2) on the degradation of SF_(6) were studied.Studies have shown that H_(2)O can effectively promote the decomposition of SF_(6) and improve its degradation rate and energy efficiency of degradation.Under the action of a pulse input voltage and input frequency of 15 kV and 15 kHz,respectively,when H_(2)O is added alone the effect of 1% H_(2)O is the best,and the rate and energy efficiency of degradation of SF_(6) reach their maximum values,which are 91.9% and 8.25 g kWh^(-1),respectively.The synergistic effect of H_(2)O and O_(2) on the degradation of SF_(6) was similar to that of H_(2)O.When the concentration of H_(2)O and O_(2) was 1%,the system obtained the best rate and energy efficiency of degradation,namely 89.7% and 8.05 g kWh~(-1),respectively.At the same time,different external gases exhibit different capabilities to regulate decomposition products.The addition of H_(2)O can effectively improve the selectivity of S0_(2).Under the synergistic effect of H_(2)O and O_(2),with increase in O_(2) concentration the degradation products gradually transformed into SO_(2)F_(2).From the perspective of harmless treatment of the degradation products of SF_(6),the addition of O_(2) during the SF_(6) degradation process should be avoided.

添加剂及其含量对交联聚乙烯高压电缆绝缘材料性能影响

为优化高压电缆交联聚乙烯(XLPE)绝缘材料配方,采用凝胶萃取、热延伸、转矩流变仪和失重法研究材料交联特性,采用红外光谱表征XLPE热氧老化特性,并测试了XLPE的力学性能和电学性能。结果表明,随交联剂过氧化二异丙苯(DCP)含量增大,XLPE凝胶含量及交联速率增大、力学性能变化较小、交流击穿强度的温度敏感性降低。优先考虑交联特性,确定DCP含量为1.8 phr。随抗氧剂含量增加,XLPE交联度降低、热延伸率稍有提高。相比单独使用0.3 phr抗氧剂300的XLPE,抗氧剂1010和1035各以0.15 phr复配使用可发生协同作用,从而更显著地抑制XLPE中羰基的形成和热氧老化,还可以在不降低交联度的前提下,改善XLPE抗焦烧性,避免预交联对XLPE性能的影响,且该材料具有更优的击穿强度温度特性和更低的介电损耗。

构筑耦合界面提高MnO2@Co3O4催化氧化甲苯性能

挥发性有机化合物(VOCs)是大气主要污染物之一,它不仅危害人类健康,而且也危害环境.催化氧化是消除VOCs最有前景的方法之一.过渡金属氧化物由于其低成本、环境友好、高催化活性等优点,而越来越受到VOCs氧化领域的重视.一般认为,具有耦合界面的多组分金属氧化物比单组分金属氧化物表现出更好的催化性能.因此,本文在一维(1D)α-MnO2纳米线上原位生长ZIF衍生的Co3O4(α-MnO2@Co3O4).由于α-MnO2和Co3O4之间耦合界面的协同效应,使得α-MnO2@Co3O4表现出优异的催化活性,甲苯转化率达到90%的反应温度(T90%)约为229℃,分别低于α-MnO2纳米线的(47℃)和热解ZIF-67产生的Co3O4-b的(28℃).本文采用氢气程序升温还原(H2-TPR),氧气程序升温脱附(O2-TPD),X射线光电子能谱(XPS),原位漫反射红外光谱(in situ DRIFTS)等手段研究了具有α-MnO2和Co3O4耦合界面的α-MnO2@Co3O4催化剂表现更优异甲苯氧化性能的原因.H2-TPR结果表明,相比于α-MnO2纳米线和热解ZIF-67产生的Co3O4-b,α-MnO2@Co3O4催化剂因具有耦合界面而表现出更好的氧流动性.O2-TPD结果表明,具有耦合界面的α-MnO2@Co3O4催化剂表面有更多的表面氧空位,从而使气相氧更容易活化为表面活性氧物种.XPS结果表明,具有耦合界面的α-MnO2@Co3O4催化剂表面有更多的活性氧物种,并且增强了Mn^4+/Mn^3+和Co^2+/Co^3+氧化还原对.原位漫反射红外结果表明,催化剂在180℃下吸附甲苯/N2250 min后,通入N2吹扫30 min,然后将气氛切换为20%O2/N2,温度保持在180℃,反应进行250 min时,α-MnO2表面吸附甲苯和苯甲醛的特征峰强度没有明显降低的趋势.相反,在反应进行50 min时,α-MnO2@Co3O4表面吸附甲苯和苯甲醛的特征峰强度明显减弱,至250 min时,这些特征峰几乎完全消失.这进一步表明,在α-MnO2@Co3O4表面,气相氧可能更容易活化为吸附氧物种,且甲苯在α-MnO2@Co3O4催化剂的可能催化反应路径如下:甲苯→苯甲酸→含氧官能团的烷烃→CO2和H2O,而更多的吸附氧物种有利于甲苯的催化氧化,且它们在催化氧化过程中起着重要的作用.另一方面,在催化反应中,阳离子的可逆价态转变(Mn^3+■Mn^4++e和Co^2+■Co^3++e)为活化氧分子提供了电子.因此,具有耦合界面的α-MnO2@Co3O4催化剂表现出更好的甲苯催化性能.此外,该制备方法可推广到其它一维MnO2材料,为开发具有实际意义的高性能催化剂提供了一种新的策略.

Highly efficient Cu/anatase TiO2 {001}-nanosheets catalysts for methanol synthesis from CO2

Anatase TiO2 nanosheets（-ns-） with dominant exposed {001} facets were used as support to load copper,and the synthesized Cu/TiO2-ns catalysts were evaluated for CO2 hydrogenation to methanol. Under the reaction conditions, P = 3.0 MPa, T = 260 ℃, V（N2）：V（H2）：V（CO2） = 8：69：23 and gas hourly space velocity（GHSV） = 3600 mL g-1h-1, the methanol yield reached an appealing high value, 5.6%. Copper-loading amount, calcination temperature and reduction atmosphere have been investigated in this work, which significantly influence the particle sizes of copper and/or the defect concentration in TiO2, then leading to different catalytic performance. Characterizations of XRD, EPR, CO2-TPD and FTIR demonstrate that higher specific surface area of Cu is good for the hydrogenation of CO2 and adequate amount of Ti3＋ plays important roles in CO2 activation. Both of them facilitate high turnover frequency（TOF） of methanol formation.

弹性体对聚丙烯基电缆绝缘材料力学及介电性能的影响

文中对聚烯烃弹性体(POE)和晶型调控聚丙烯基绝缘材料(PPB)共混体系的力学性能及介电性能进行了研究,探讨了弹性体含量对材料性能的影响。采用扫描电子显微镜和差示扫描量热仪研究了共混物的相态结构及熔融结晶特性。结果表明,POE与基体的相容性较好,有良好的分散性,弹性体的引入对共混物的熔融及结晶特性无明显影响。通过拉伸试验和动态力学热分析说明,共混物的力学性能得到了明显改善,当POE的质量分数为40%时,断裂伸长率为632.05%,提高了约20%,弹性模量降低了50%,低温韧性也有所提高;介电频谱、交流击穿等实验表明,POE质量分数不超过40%时,该体系更大程度地维持了基体的电性能,具有潜在的工程应用价值。

Low-temperature NH_(3) abatement via selective oxidation over a supported copper catalyst with high Cu^(+) abundance

Selective catalytic NH_(3)-to-N_(2) oxidation(NH_(3)-SCO)is highly promising for abating NH_(3) emissions slipped from stationary flue gas after-treatment devices.Its practical application,however,is limited by the non-availability of low-cost catalysts with high activity and N_(2) selectivity.Here,using defect-rich nitrogen-doped carbon nanotubes(NCNT-AW)as the support,we developed a highly active and durable copper-based NH_(3)-SCO catalyst with a high abundance of cuprous(Cu^(+))sites.The obtained Cu/NCNT-AW catalyst demonstrated outstanding activity with a T_(50)(i.e.the temperature to reach 50% NH_(3) conversion)of 174℃ in the NH_(3)-SCO reaction,which outperformed not only the Cu catalyst supported on N-free O-functionalized CNTs(OCNTs)or NCNT with less surface defects,but also those most active Cu catalysts in open literature.Reaction kinetics measurements and temperature-programmed surface reactions using NH_(3)as a probe molecule revealed that the NH_(3)-SCO reaction on Cu/NCNT-AW follows an internal selective catalytic reaction(i-SCR)route involving nitric oxide(NO)as a key intermediate.According to mechanistic investigations by X-ray photoelectron spectroscopy,Raman spectroscopy,and X-ray absorption spectroscopy,the superior NH_(3)-SCO performance of Cu/NCNT-AW originated from a synergy of surface defects and N-dopants.Specifically,surface defects promoted the anchoring of Cu O nanoparticles on N-containing sites and,thereby,enabled efficient electron transfer from N to Cu O,increasing significantly the fraction of SCR-active Cu^(+)sites in the catalyst.This study puts forward a new idea for manipulating and utilizing the interplay of defects and N-dopants on carbon surfaces to fabricate Cu^(+)-rich Cu catalysts for efficient abatement of slip NH_(3)emissions via selective oxidation.

Efficient NO_x abatement by passive adsorption over a Pd-SAPO-34 catalyst prepared by solid-state ion exchange

Palladium-exchanged chabazite(Pd-CHA) zeolites as passive NO_x adsorbers(PNAs) enable efficient purification of nitrogen oxides(NO_x) in cold-start diesel exhausts. Their commercial application, however,is limited by the lack of facile preparation method. Here, high-performance CHA-type Pd-SAPO-34 zeolite was synthesized by a modified solid-state ion exchange(SSIE) method using PdO as Pd precursor,and demonstrated superior PNA performance as compared to Pd-SAPO-34 prepared by conventional wetchemistry strategies. Structural characterization using Raman spectroscopy and X-ray diffraction revealed that the SSIE method avoided water-induced damage to the zeolite framework during Pd loading. Mechanistic investigations on the SSIE process by in situ infrared spectroscopy and X-ray photoelectron spectroscopy disclosed that, while PdO precursor was mainly converted to Pd^(2+) cations coordinated to the zeolite framework by consuming the-OH groups of the zeolite, a portion of PdO could also undergo thermal decomposition to form highly dispersed Pd~0 clusters in the pore channels. This simplified and scalable SSIE method paves a new way for the cost-effective synthesis of defect-free high-performance Pd-SAPO-34 zeolites as PNA catalysts.

Broadband impedance spectrum detection of buffer layer defects in 110 kV crosslinked polyethylene cable with corrugated aluminium sheath

The buffer layer defects of high‐voltage crosslinked polyethylene(XLPE)cable occur frequently,which makes the detection method become the focus to be studied.Here,the broadband impedance detection technology for the buffer layer defects of high‐voltage XLPE cables with corrugated aluminium sheath is investigated.There are nine cable samples,including new and defective ones.Some of the defective cables are artificial,and the other is retired cables.The influence of wiring mode,the circumferential relative position of electrodes,cable length,artificial white powder,artificial damp,and retired defective cables on the impedance spectrum is studied.It is found that the wiring mode of the insulation shield/aluminium sheath at the end of the cable can effectively detect the buffer layer defects.And the broadband impedance amplitude spectrum of the buffer layer in defective cable,measuring at various circumferential relative positions,is obviously different.When there are white powders,air gaps,or ablation in the buffer layer,the broadband impedance spectrum(BIS)will increase by several times.When the buffer layer is damped,the BIS will reduce.The research here provides theoretical support and technical methods for the buffer layer defects of XLPE cable with corrugated aluminium sheath.

Adsorption of VOCs on reduced graphene oxide

A modified Hummer＇s method was adopted for the synthesis of graphene oxide（GO） and reduced graphene oxide（rGO）. It was revealed that the modified method is effective for the production of GO and rGO from graphite. Transmission electron microscopy（TEM） images of GO and rGO showed a sheet-like morphology. Because of the presence of oxygenated functional groups on the carbon surface, the interlayer spacing of the prepared GO was higher than that of rGO. The presence of ／OH and CO groups in the Fourier transform infrared spectra（FTIR） spectrum and G-mode and 2D-mode in Raman spectra confirmed the synthesis of GO and rGO. rGO（292.6 m2/g） showed higher surface area than that of GO（236.4 m2/g）. The prepared rGO was used as an adsorbent for benzene and toluene（model pollutants of volatile organic compounds（VOCs）） under dynamic adsorption/desorption conditions. rGO showed higher adsorption capacity and breakthrough times than GO. The adsorption capacity of rGO for benzene and toluene was 276.4 and 304.4 mg/g, respectively.Desorption experiments showed that the spent rGO can be successfully regenerated by heating at 150.0℃. Its excellent adsorption/desorption performance for benzene and toluene makes rGO a potential adsorbent for VOC adsorption.

Macroporous Ni foam-supported Co_3O_4 nanobrush and nanomace hybrid arrays for high-efficiency CO oxidation

Herein, we reported the synthesis of well-defined Co_3O_4 nanoarrays(NAs) supported on a monolithic three-dimensional macroporous nickel(Ni) foam substrate for use in highefficiency CO oxidation. The monolithic Co_3O_4 NAs catalysts were obtained through a generic hydrothermal synthesis route with subsequent calcination. By controlling the reaction time,solvent polarity and deposition agent, these Co_3O_4 NAs catalysts exhibited various novel morphologies(single or hybrid arrays), whose physicochemical properties were further characterized by using several analytical techniques. Based on the catalytic and characterization analyses, it was found that the Co_3O_4 NAs-6 catalyst with nanobrush and nanomace arrays displayed enhanced catalytic activity for CO oxidation, achieving an efficient 100% CO oxidation conversion at a gas hourly space velocity(GHSV) 10,000 hr^(-1) and 150°C with longterm stability. Compared with the other Co_3O_4 NAs catalysts, it had the highest abundance of surface-adsorbed oxygen species, excellent low-temperature reducibility and was rich in surface-active sites(Co^(3+)/Co^(2+)= 1.26).

Toluene decomposition performance and NOx by-product formation during a DBD-catalyst process

Characteristics of toluene decomposition and formation of nitrogen oxide（NOx） by-products were investigated in a dielectric barrier discharge（DBD） reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide（Mn Ox）, iron oxide（Fe Ox）, cobalt oxide（Co Ox） and copper oxide（Cu O）, supported on Al2O3/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO2 selectivity. In addition, NOx was suppressed with the decrease of specific energy density（SED） and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the Cu O catalyst showed the best performance in NOx suppression. The Mn Ox catalyst exhibited the lowest concentration of O3 and highest CO2 selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression.

Unraveling specific role of carbon matrix over Pd/quasi-Ce-MOF facilitating toluene enhanced degradation

Metal organic frameworks(MOFs)derivatives represented by quasi-MOFs have excellent physical and chemical properties and can be applied for the catalytic combustion of volatile organic compounds(VOCs).In this work,Pd/quasi-Ce-BTC synthesized by simple one-step Npyrolysis was applied to the oxidation of toluene,showing excellent toluene catalytic activity(T_(90)=175℃,30000 mL/(g·h)).Microscopic analyses indicate the formation and interaction of a carbon matrix composite quasi-MOF structure interface.The results show that the amorphous carbon matrix formed during the partial pyrolysis of Ce-BTC significantly improves the adsorption and activation capacity of toluene in the reaction,and constructs a reductive system to maintain high concentrations of Ce^(3+)and Pd^(0),which can facilitate the activation and utilization of oxygen in reaction.Quasi in-situ XPS proves that carbon matrix is indirectly involved in the activation and storage of oxygen,and Pd^(0)is the crucial active site for the activation of oxygen.Stability and water resistance tests display good stability of Pd/quasi-Ce-BTC.This work provides a potential method for designing quasi-MOF catalysts towards VOCs effective abatement.

Research progress of semiconductive shielding layer of HVDC cable

As an indispensable part of high-voltage direct current(HVDC)cable,the semiconductive shielding layer plays the role of uniforming electric field in the cable.However,cable shielding materials>35 kV mainly rely on foreign imports in China,which belongs to the technical weak issues in the field of electrical materials.At present,there are few systematic reports on semiconductive shielding material of HVDC cable.In the work,the mechanisms of charge conduction and thermal conduction of semiconductive material have been introduced.Effect of raw material,carbon black content and the second conductive filler on the resistance characteristics of the semiconductive layer,the charge accumulation characteristics of the insulating layer and the interface characteristics have been studied.A kind of semiconductive layer as a high voltage terminal charge emission method has been proposed to study charge emission from the semiconducting layer to the insulation layer.This work can provide theoretical guidance for the research of semiconductive shielding materials.

Experimental study on the partial discharge and AC breakdown properties of C_(4)F_(7)N/CO_(2)mixture

As an environmental friendly insulating medium,C_(4)F_(7)N has received extensive attention in the past two years.In this study,the partial discharge(PD)and breakdown characteristics of C_(4)F_(7)N/CO_(2)gas mixture were investigated using the gas insulation performance test platform.The influence of gas pressure and mixing ratio on the PD initial voltage(PDIV)and breakdown voltage of C_(4)F_(7)N/CO_(2)gas mixture in different electric fields was tested.It was found that the PDIV and breakdown voltage of gas mixture with 2-8%C_(4)F_(7)N in the highly non-uniform field showed a linear saturation increasing trend with the change of gas pressure and mixing ratio.The breakdown voltage of gas mixture increases linearly with gas pressure in the quasi-uniform electric field.The relative breakdown voltage of gas mixture in the highly non-uniform field under high-pressure conditions is inferior to those of low-pressure conditions.The C_(4)F_(7)N/CO_(2)gas mixture containing 2-8%C_(4)F_(7)N is sensitive to the non-uniformity of electric field.According to the PD and breakdown tests results,C_(4)F_(7)N/CO_(2)gas mixture with 2-8%C_(4)F_(7)N has the potential to replace SF6 using in gas-insulated equipment.

Construction of Cu-Ce interface for boosting toluene oxidation:Study of Cu-Ce interaction and intermediates identified by in situ DRIFTS

A facile hydrothermal method was applied to gain stably and highly efficient CuO-CeO_(2)(denoted as Cu1Ce2)catalyst for toluene oxidation.The changes of surface and inter properties on Cu1Ce2 were investigated comparing with pure CeO_(2)and pure CuO.The formation of Cu-Ce interface promotes the electron transfer between Cu and Ce through Cu^(2+)+Ce^(3+)↔Cu^(+)+Ce^(4+)and leads to high redox properties and mobility of oxygen species.Thus,the Cu1Ce2 catalyst makes up the shortcoming of CeO_(2)and CuO and achieved high catalytic performance with T_(50)=234°C and T_(99)=250°C(the temperature at which 50%and 90%C_(7)H_(8)conversion is obtained,respectively)for toluene oxidation.Different reaction steps and intermediates for toluene oxidation over Cu1Ce2,CeO_(2)and CuO were detected by in situ DRIFTS,the fast benzyl species conversion and preferential transformation of benzoates into carbonates through C=C breaking over Cu1Ce2 should accelerate the reaction.

Synergistic catalytic ozonation of toluene with manganese and cerium varies at low temperature

The temperature of waste gas in refuse transfer station,airport smoking area,and RTO terminal is low,which needs deep oxidation.Catalytic ozonation is one of the most effective treatment techniques in these scenarios.In this study,we reported that catalysts were modified under the condition of mag-netic field to simulate the low temperature dynamic conditions of low concentration toluene for catalytic ozonation.This paper aims to explore the relationship between oxygen vacancy and active oxygen species,and the specific pathways of toluene oxidation.The study found that citric acid can enhance the syner-gistic effect between Mn and Ce,and promote the generation of oxygen vacancies.The surface molecule adsorption oxygen is more conducive to catalytic oxidation than subsurface atom adsorption oxygen.Fi-nally,we proposed the main pathways of toluene in this reaction system,which runs through the whole process of the reaction.

Immobilizing ultrafine bimetallic PtAg alloy onto uniform MnO_(2) microsphere as a highly active catalyst for CO oxidation

Herein,a facile glycol reduction route is successful employed to synthesize bimetallic Pt Ag alloys with homogeneous distribution of sizes and elements.Experimental studies reveal that the ultrafine Pt Ag alloys with well-defined sizes from around 3.3 nm to 5.8 nm are immobilized onto MnO_(2)microsphere,which remarkably enhances the catalytic performances for CO oxidation.Importantly,quasi in-situ X-ray photoelectron spectroscopy(XPS)result reveals that both Mn and Pt ions on the surface of catalysts would realize alternating reduction-oxidation by CO and O_(2)molecules,and the oxygen vacancy sites could be replenished and excited by gas-phase O_(2).

Effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria:Soot-ceria contact and interfacial oxygen evolution

Ceria is widely used as a catalyst for soot combustion,but effects of Zr substitution on the reaction mechanism is ambiguous.The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria.The nanostructured CeO_(2),Ce_(0.92)Zr_(0.08)O_(2),and Ce_(0.84)Zr_(0.16)O_(2)composed of 5-6 nm crystallites display T_(m-CO2)(the temperature at maximum CO_2 yield)at 383,355,and 375℃under 10 vol.%O_(2)/N_(2),respectively.The size of agglomerate decreases from 165.5 to 51.9-57.3 nm,which is beneficial for the sootceria contact.Moreover,Zr increases the amount of surface oxygen vacancies,generating more active oxygen(O_(2)^-and O^(-))for soot oxidation.Thus,the activities of Ce_(0.92)Zr_(0.08)O_(2)and Ce_(0.84)Zr_(0.16)O_(2)in soot combustion are better than that of CeO_(2).Although oxygen vacancies promote the migration of lattice O~(2-),the enriched surface Zr also inhibits the mobility of lattice O^(2-).Therefore,the T_(m-CO2)of Ce_(0.84)Zr_(0.1)6 O_(2)is higher than that of Ce_(0.92)Zr_(0.08)O_(2).Based on reaction kinetic study,soot in direct contact with ceria preferentially decomposes with low activation energy,while the oxidation of isolated soot occurs through diffusion with high activation energy.The obtained findings provide new understanding on the soot combustion over nanoceria.

Corrigendum to ‘Adsorption of VOCs on reduced graphene oxide’ [J. Environ. Sci. 67 (2018) 171-178]

The authors regret“In the whole text,ppm and mg/L was confusing.As in aqueous phase,1 ppm=1 mg/L,but in gaseous phase,1 ppm=0.001%o.In this paper,in text and figures,the concentration units were ppm,but when calculating the adsorption ca-pacity,the concentration units ppm were mistakenly used as mg/L.As for benzene,1 ppm=3.4871 x 10^-3 mg/L,as for toluene。