Enhanced gas separation performance of mixed matrix hollow fiber membranes containing post-functionalized S-MIL-53

Mixed matrix hollow fiber membranes（MMHFMs）filled with metal-organic frameworks（MOFs）have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and membrane plasticization.Herein,lab-synthesized MIL-53 was post-functionalized by aminosilane grafting and subsequently incorporated into Ultem-1000 polymer matrix to fabricate high performance MMHFMs.SEM,DLS,XRD and TGA were performed to characterize silane-modified MIL-53（S-MIL-53）and prepared MMHFMs.Moreover,the effect of MOFs loading was systematically investigated first;then gas separation performance of MMHFMs for pure and mixed gas was evaluated under different pressures.MMHFMs containing post-functionalized S-MIL-53 achieved remarkable gas permeation properties which was better than model predictions.Compared to pure HFMs,CO2permeance of MMHFM loaded with 15%S-MIL-53 increased by 157%accompanying with 40%increase for CO2/N2selectivity,which outperformed the MMHFM filled with naked MIL-53.The pure and mixed gas permeation measurements with elevated feed pressure indicated that incorporation of S-MIL-53 also increased the resistance against CO2plasticization.This work reveals that post-modified MOFs embedded in MMHFMs facilitate the improvement of gas separation performance and suppression of membrane plasticization.

Synergistic Effect in Mixed Capillary Gas Chromatographic Stationap Phases Containing Heptakis(2,3,6-tri-o-pentyl)-β-cyclodextrin and Dibenzo-18-crown-6

used－silical capillary columns containing heptakis（2、3、6－tri－o－pentyl）-β-cyclodextrinand dibenzo-18-crown-6 were prepared．By studying the selectivity of mixed stationary phases forsome solute pairs.as well as comparing with the heptakis（2．3、6-tri-O-pentyl）-β-cyclodextrin and thedibenzo-18-crown-6 used as individual stationary phase、the synergistic effects were observed.These effects were affected by the column temperature．mixed ratio and linear velocity of carrier gas．

Distinguished discriminatory separation of CO2 from its methane-containing gas mixture via PEBAX mixed matrix membrane

Highly selective separation of CO_2 from its methane-containing binary gas mixture can be achieved by using Poly(ether-block-amide)(PEBAX)mixed matrix membranes(MMMs).According to FESEM and AFM analyses,silica-based nanoparticles were homogenously integrated within the polymer matrix,facilitating penetration of CO_2 through the membrane while acting as barrier for methane gas.The membrane containing 4.6 wt% fumed silica(FS)(PEBAX/4.6 wt%FS)exhibits astonishing selectivity results where binary gas mixture of CO_2/CH_4 was used as feed gas.As detected by gas chromatography,in the permeate side,data showed a significant increase of CO_2 permeance,while CH_4 transport through the mixed matrix membrane was not detectable.Moreover,PEBAX/4.6 wt%FS greatly exceeds the Robeson limit.According to data reported on CO_2/CH_4 gas pair separation in the literature,the results achieved in this work are beyond those data reported in the literature,particularly when PEBAX/4.6 wt%FS membrane was utilized.

Discharge mode and particle transport in radio frequency capacitively coupled Ar/O_(2)plasma discharges

Simulations are conducted on capacitively coupled Ar/O_(2)mixed gas discharges employing a one-dimensional fluid coupled with an electron Monte Carlo(MC)model.The research explores the impact of different O_(2)ratio and pressures on the discharge characteristics of Ar/O_(2)plasma.At a fixed Ar/O_(2)gas ratio,with the increasing pressure,higher ion densities,as well as a slight increase in electron density in the bulk region can be observed.The discharge remains dominated by the drift-ambipolar(DA)mode,and the flux of O(3P)at the electrode increases with the increasing pressure due to higher background gas density,while the fluxes of O(1D)and Ardecrease due to the pronounced loss rate.With the increasing proportion of O_(2),a change in the dominant discharge mode from a mode to DA mode can be detected,and the O_(2)-associated charged particle densities are significantly increased.However,Ar+density shows a trend of increasing and then decreasing,while for neutral fluxes at the electrode,Arflux decreases,and O(3P)flux increases with the reduced Ar gas proportion,while trends in O(1D)flux show slight differences.The evolution of the densities of the charged particle and the neutral fluxes under different discharge parameters are discussed in detail using the ionization characteristics as well as the transport properties.Hopefully,more comprehensive understanding of Ar/O_(2)discharge characteristics in this work will provide a valuable reference for the industry.

Multichannel Discharge Characteristics of Gas Switch Gap in SF_6-N_2 or SF_6-Ar Gas Mixtures Under Nanosecond Triggering Pulses

Experiments were carried out to ascertain multichannel discharge characteristics in a self-designed coaxial field-distortion gas switch filled with SFa-N2 or SF6-Ar gas mixtures of different mixing ratios. In these experiments, the pressure varied from 0.1 MPa to 0.2 MPa, the voltage pulse peak applied to the switch was in the range from 40 kV to 78 kV, and the pulse rise time was 11 ns. The static breakdown strength of the gas switch gap in the switch was also measured. The results show that in general the average number of discharge channels for SF6-Ar or SF6-N2 gas mixture which contains less SFa is larger than that for gas mixture which contains more SF6, however, the average number of channels almost keeps constant as the gas mixing ratio varies when the pulse rise rate is high enough. The static breakdown strength of the gas switch gap decreases slightly as the content of argon or nitrogen increases.

Recovery of iron from copper slag via modified roasting in CO-CO2 mixed gas and magnetic separation

A novel technology,modified roasting in CO-CO2 mixed gas and magnetic separation,was presented to recover iron from copper slag.The effects of various parameters such as dosage of flux(CaO),gas flowrate of CO and CO2,roasting temperature,roasting time,particle size of modified slag and magnetic flux density on the oxidized modification and magnetic separation were investigated by comparison of the X-ray diffraction patterns and iron recovery ratio.The optimum conditions for recovering iron by oxidizing roasting and magnetic separation are as follows:calcium oxide content of 25 wt.%,mixed gas flow rates of CO2 and CO of 180 and 20 mL/min,oxidizing roasting at 1323 K for 2 h,grinding the modified slag to 38.5-25.0μm and magnetic separation at 170 mT.The mineralogical and microstructural characteristics of modified slag revealed that the iron-bearing minerals in the copper slag were oxidized,the generated magnetite grew into large particles,and the silicate in copper slag was combined with calcium oxide to form calcium silicate.Finally,the iron-bearing concentrate with an iron grade of 54.79%and iron recovery ratio of 80.14%was effectively obtained.

Insight into the promotional mechanism of Cu modification towards wide-temperature NH3-SCR performance of NbCe catalyst

A simple strategy of Cu modification was proposed to broaden the operation temperature window for NbCe catalyst.The best catalyst Cu0.010/Nb1Ce3 presented over 90%NO conversion in a wide temperature range of 200-400℃and exhibited an excellent H_(2)O or/and SO_(2) resistance at 275℃.To understand the promotional mechanism of Cu modification,the correlation among the"activity-structure-property"were tried to establish systematically.Cu species highly dispersed on NbCe catalyst to serve as the active component.The strong interaction among Cu,Nb and Ce promoted the emergence of NbO4 and induced more Bronsted acid sites.And Cu modification obviously enhanced the redox behavior of the NbCe catalyst.Besides,EPR probed the Cu species exited in the form of monomeric and dimeric Cu^(2+),the isolated Cu^(2+)acted as catalytic active sites to promote the reaction:Cu^(2+)-NO_(3)^(-)+NO(g)→Cu^(2+)-NO_(2)^(-)+NO_(2)(g).Then the generated NO_(2) would accelerate the fast-SCR reaction process and thus facilitated the lowtemperature deNO_(x) efficiency.Moreover,surface nitrates became unstable and easy to decompose after Cu modification,thus providing additional adsorption and activation sites for NH3,and ensuring the improvement of catalytic activity at high temperature.Since the NH3-SCR reaction followed by E-R reaction pathway efficaciously over Cu_(0.010)/Nb_(1)Ce_(3) catalyst,the excellent H_(2)O and SO_(2) resistance was as expected.

Room temperature NO2-sensing properties of hexagonal tungsten oxide nanorods

Hexagonal WO_3 nanorods were synthesized through a facile hydrothermal method. The nanorods properties were investigated by scanning electron microscope（SEM）, transmission electron microscope（TEM）, energy dispersive spectroscopy（EDS）, and x-ray diffraction（XRD）. The NO_2-sensing performances in terms of sensor response, response/recovery times and repeatability at room temperature were optimized by varying the heat treatment temperature of WO_3 nanorods. The optimized NO_2sensor（400-℃-annealed WO_3 nanorods） showed an ultra-high sensor response of 3.2 and short response time of 1 s to 5-ppm NO_2. In addition, the 400-℃-annealed sample exhibited more stable repeatability.Furthermore, dynamic responses measurements of annealed samples showed that all the annealed WO_3 nanorods sensors presented p-type behaviors. We suppose the p-type behavior of the WO_3 nanorods sensor to be that an inversion layer is formed in the space charge layer when the sensor is exposed to NO_2 at room temperature.Therefore, the 400-℃-annealed WO_3 nanorods sensor is one of the most energy conservation candidates to detect NO_2 at room temperature.

600MW烟煤锅炉掺烧褐煤试验研究

以某600 MW机组锅炉为研究对象,进行褐煤掺烧试验,通过对20%、40%、60%不同褐煤掺烧比例及纯烟煤工况下的制粉特性、炉内燃烧特性、锅炉热效率、运行参数等分析对比,结果表明:掺烧褐煤后,通过降低磨出口温度,调整折向挡板开度等手段可使制粉系统的出力满足要求,同时保证制粉系统运行的安全性。从炉内着火情况来看,喷口的着火距离有拉近的趋势,炉膛水冷壁、大屏上覆盖的渣量及炉底渣量都呈增加趋势。掺烧褐煤后锅炉效率总体下降,褐煤掺烧比例为60%时,锅炉效率同比降低约0.45%。NO_(x)排放浓度随着掺烧比例的提高而增大。以期为同类型褐煤掺烧锅炉燃烧优化及技术改造提供依据。

Preparation of gangue ceramsite by sintering pot test and potential analysis of waste heat recovery from flue gas

Preparation of ceramsite from solid waste based on the sintering process is a new technology and had a high efficiency in improving producing capability, decreasing consumption of liquefied petroleum gas (LPG), and recovering waste heat of flue gas. An experiment sintering gangue ceramsite was conducted in a 25 kg scale sintering pot with a 100 cm height. The combustion characteristics, phase transformation, and the release profile of SO_(2)^(*) (SO and/or SO_(2)) and NO_(x)^(*) (N_(2)O, NO, and/or NO_(2)) of gangue ceramsite during the sintering process were studied by X-ray diffraction analysis, X-ray fluorescence spectrometry, thermogravimetry–differential thermogravimetry–differential scanning calorimetry, and measurement of physical properties of ceramsite and gas components of flue gas. The results showed that the gangue ceramsite had excellent properties, and its compressive strength and water absorption were 8.2–9.6 MPa and 8.9%–9.8%, respectively, far exceeding the requirement of standard (GB/T 17431.1–2010). The ignition temperature of gangue ceramsite was 443 ℃, and the ignition loss was 14.60 mass% at 1000 ℃. Kaolinite and calcite disappeared at 600 and 800 ℃, respectively. Albite disappeared and mullite formed at 1000 ℃. Two peaks of SO_(2)^(*) emissions emerged in the range of 311–346 mg m^(-3) near 500 ℃ of upper layer ceramsite and 420–489 mg m^(-3) near 1000 ℃ of lower layer ceramsite, respectively. NO_(x)^(*) emissions peak emerged in the range of 227–258 mg m^(-3) near 550 ℃ of the upper layer ceramsite, which was related to the oxidation of sulfide and the combustion of LPG. Gangue is a direct heat source for sintering of ceramsite as well. During sintering process, the heat of flue gas above and below 400 ℃ accounts for 55.9% and 30.0% of the all-output heat, respectively, and was potentially used for producing waste-heat steam or electricity as by-products and drying raw materials during its own initial sintering process, which can realize combined mass and heat utilization for the gangue and further reduce the cost of sintered gangue ceramsite.

STUDY ON ATMOSPHERIC TRACE GAS NO_2

The content of NO_2 in the atmosphere is one of the important factors for atmospheric environmental appreciation. An automatic solar spectrophotometer (ASS) system has been developed in order to observe the content of NO_2 in the atmosphere. The column content of atmospheric NO_2 has been obtained by use of radiative transfer equation and maximum resembled method, through the ground-based observation of direct solar radiative spectrum of 4470—4490. Some months' observations of NO_2 have been made in the suburbs of Beijing. The results have been discussed here.

Enhanced room temperature gas sensing performance of ZnO with atomic-level Pt catalysts facilitated by the polydopamine mediator

The poor sensitivity of metal-oxide(MO)sensing material at room temperature can be enhanced by the modi-fication of noble metal catalysts.However,the large size and uncontrollable morphology of metal nanoparticles(NPs)compromise the catalytic activity and selectivity.Downsizing metal NPs to the atomic level is a promising solution because it offers high activity and selectivity.Nevertheless,a facile and universal approach for stable loading atomic-level metal on MO-based sensing materials is still challenging.Herein,we present a strategy to construct synergetic coordination interface for uniform loading of atomic-level metal catalysts on MO-based gas-sensing materials using a difunctional mediator layer.In this work,atomically dispersed Pt catalysts are coor-dinately anchored on ZnO nanorods(NRs)using polydopamine(PDA)as a mediator.As a result,compared with pristine ZnO NRs,a six-fold enhanced response of 18,489%is achieved toward 100 ppm NO_(2)on 0.20 wt%Pt-ZnO@PDA-1.5 nm,and the selectivity is also promoted.Such sensitivity is higher than that of most reported noble metal-modified MO NO_(2)-sensing materials.This work provides a simple and general strategy for building highly sensitive and selective gas-sensing materials using atomic-level noble metal catalyst.

Graphdiyne:a Highly Sensitive Material for ppb-Level NO_(2) Gas Sensing at Room Temperature

Detection of a trace amount of NO_(2) at room temperature has very important applications in air quality monitoring,protection of human health and medical diagnose.However,the existing NO_(2) sensors often suffer from low sensitivity when the concentration at the ppb-level.Here,we report a new kind of materials based on graphdiyne(GDY)for highly sensitive detection of ppb-level(ppb:part per billion)NO_(2) at room temperature.After thermal treatment of the as-prepared GDY at 600℃under argon atmosphere for 2 h(the obtained sample denoted as GDY-600),the prepared sensor with GDY-600 displays excellent sensitivity with a response value of 6.2%towards 250 ppb NO_(2) at room temperature,which is better than most of reported sensing materials.In addition,the sensor exhibits significantly high selectivity to NO_(2) against typical interfering gases including CO,CO_(2),NH_(3),H_(2),H_(2)S and toluene.Moreover,the sensor shows remarkable stability after repetitive measurements.The superior sensing performance of GDY-600 can be ascribed to the highlyπ-conjugated structure with special acetylenic bonds and abundant oxygen-containing functional groups,which are all beneficial for the gas adsorption and redox reaction on the surface.

Self-healable, recyclable, ultrastretchable, and high-performanceNO_(2) sensors based on an organohydrogel for room and sub-zero temperature and wireless operation

To date,development of high-performance,stretchable gas sensors operating at and below room temperature(RT)remains a challenge in terms of traditional sensing materials.Herein,we report on a high-performance NO_(2) gas sensor based on a self-healable,recyclable,ultrastretchable,and stable polyvinyl alcohol–cellulose nanofibril double-network organohydrogel,which features ultrahigh sensitivity(372%/ppm),low limit of detection(2.23 ppb),relatively fast response and recovery time(41/144 s for 250 ppb NO_(2)),good selectivity against interfering gases(NH3,CO_(2),ethanol,and acetone),excellent reversibility,repeatability,and long-term stability at RT or even at−20°C.In particular,this sensor shows outstanding stability against large deformations and mechanical damages so that it works normally after rapid self-healing or remolding after undergoing mechanical damage without significant performance degradation,which has major advantages compared to state-of-the-art gas sensors.The high NO_(2) sensitivity and selectivity are attributed to the selective redox reactions at the threephase interface of gas,gel,and electrode,which is even boosted by applying tensile strain.With a specific electrical circuit design,a wireless NO_(2) alarm system based on this sensor is created to enable continuous,real-time,and wireless NO_(2) detection to avoid the risk of exposure to NO_(2) higher than threshold concentrations.

ZnO/PANI nanoflake arrays sensor for ultra-low concentration and rapid detection of NO_(2)at room temperature

With the development of environmental monitoring,it is urgent to establish NO_(2)sensor with good sensing performance.Compared with the traditional NO_(2)sensors made of metal oxides,NO_(2)sensors made of n-p heterostructure nanocomposites have good sensing performance in detection limit and operating temperature.ZnO nanoflake arrays with polyaniline film grown on the surface were prepared on ceramic tubes by hydrothermal and vapor diffusion method.The gas-phase diffusion method can control the heterostructure by adjusting the diffusion time.At room temperature(25℃),the construction of rich n-p heterogeneous interface enables the sensor prepared by the nanocomposite to respond to NO_(2),showing the sensing performance with the response value of 28.00 to10.00×10^(-6)NO_(2);the detection limit improved to0.01×10^(-6)and the recovery time of 18 s.In this work,the sensing mechanism of NO_(2)at heterogeneous interface is analyzed,which provides a promising material for the detection of low concentration NO_(2)at room temperature.

Development of CO_(2) capture and utilization technology in steelmaking plant

The performance of a recycling process for CO_(2) capture and utilization of exhaust gas in the steelmaking plant was reported.A facility capable of capturing CO_(2) at 3200 m^(3)/h was established in the steelmaking plant,resulting in the CO_(2) production of 50,000 t/a.The CO_(2) concentration of the exhaust gas from the lime kiln increased from 25.0 to 99.8 vol.%using the comprehensive method of the pressure swing adsorption and cryogenic separation.The captured and purified CO_(2) was successfully applied in the converter process by the top blowing and bottom blowing.The utilization of CO_(2) was 3.5 m^(3)/t through these two modes.After optimizing parameters of CO_(2)-O_(2) mixed top blowing,the value of[C]×[O]and the content of TFe in slag were reduced by 1.33×10-4 and 1.27%,respectively,and the dephosphorization rate of the molten steel increased by 2.31%.For the CO_(2) bottom blowing,the[N]content in the molten steel was significantly reduced by 5.7×10^(-6).

ZnSe/NiO heterostructure-based chemiresistive-type sensors for low-concentration NO_(2) detection

Novel ZnSe/NiO heterostructure nanocomposites were successfully prepared by one-step hydrothermal method.The ZnSe/NiO-based sensor exhibits a response of~96.47% to 8×10^(-6) NO_(2) at 140℃,which is significantly higher than those of intrinsic ZnSe-based(no response)and NiO-based(~19.65%)sensors.The theoretical detection limit(LOD)of the sensor is calculated to be 8.91×10^(-9),indicating that the sensor can be applied to detect the ultralow concentrations of NO_(2).The effect of NiO content on the gas-sensing performance of the nanocomposites was investigated in detail.The optimal NiO content in the nanocomposite is determined to be15.16%to achieve the highest response.The as-fabricated sensor also presents an excellent selectivity to several possible interferents such as methanol,ethanol,acetone,benzene,ammonia and formaldehyde.The enhanced sensing performance can be attributed to the formation of p-p heterostructures between ZnSe and NiO,which induces the charge transfer across the interfaces and yields more active sites.