空分精馏系统最佳氩馏分位置的确定

指出在同时生产高纯度的氢、氮及粗氩产品，并带粗氩塔的空气分离双级精馏系统中，双级精馏塔的上塔存在最佳抽氩馏分位置，并介绍其确定方法。     

Mixed‐cation LiCa‐LSX zeolite with minimum lithium for air separation

The aim of this work was to reduce/minimize Li in Li‐LSX by replacing the 70% Li⁺ cations in Li‐LSX that are bonded to the interior or inaccessible sites which are not used for adsorption. Thus, mixed‐cation LiCa‐LSX containing minimum lithium were prepared by exchanging small fractions of Li⁺ into Ca‐LSX, followed by dehydration under mild conditions to avoid migration/equilibration of Li cations. Comparisons of adsorption isotherms of N₂/O₂ and heats of adsorption for the LiCa‐LSX samples with that for pure‐cation Li‐LSX and Ca‐LSX provided strong evidence that significant amounts of these Li cations indeed remained on the exposed sites (SIII). The mixed‐cation LiCa‐LSX samples were compared against the pure‐cation Ca‐LSX and Li‐LSX based on their performance for oxygen production by PSA, via model simulation. The results showed that the mixed‐cation LiCa‐LSX samples yielded significantly higher O₂ product productivities at the same product purity and recovery than their pure‐cation precursor (Ca‐LSX). © 2017 American Institute of Chemical Engineers AIChE J, 64: 406–415, 2018     

Evaluation of mixed‐conducting lanthanum‐strontium‐cobaltite ceramic membrane for oxygen separation

In this study, La_0.4Sr_0.6CoO_3‐δ (LSC) oxide was synthesized via an EDTA‐citrate complexing process and its application as a mixed‐conducting ceramic membrane for oxygen separation was systematically investigated. The phase structure of the powder and microstructure of the membrane were characterized by XRD and SEM, respectively. The optimum condition for membrane sintering was developed based on SEM and four‐probe DC electrical conductivity characterizations. The oxygen permeation fluxes at various temperatures and oxygen partial pressure gradients were measured by gas chromatography method. Fundamental equations of oxygen permeation and transport resistance through mixed conducting membrane were developed. The oxygen bulk diffusion coefficient (D_v) and surface exchange coefficient (K_ex) for LSC membrane were derived by model regression. The importance of surface exchange kinetics at each side of the membrane on oxygen permeation flux under different oxygen partial pressure gradients and temperatures were quantitatively distinguished from the oxygen bulk diffusion. The maximum oxygen flux achieved based on 1.6‐mm‐thick La_0.4Sr_0.6CoO_3‐δ membrane was ～4.0 × 10^?7 mol cm^?2 s^?1at 950°C. However, calculation results show theoretical oxygen fluxes as high as 2.98 × 10^?5 mol cm^?2 s^?1 through a 5‐μm‐thick LSC membrane with ideal surface modification when operating at 950°C for air separation. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

High‐rate hydrogen separation using an MIEC oxygen permeable membrane reactor

In this study, we propose using mixed ionic‐electronic conducting (MIEC) oxygen permeable membrane to separate hydrogen via the water splitting reaction. To do that, steam was fed to one side of the membrane (side I) and a low‐purity hydrogen was fed to the other side (side II). Oxygen from water splitting on side I permeates through the membrane driven by an oxygen chemical potential gradient across the membrane to react with the low‐purity hydrogen on side II. After condensation and drying, high‐purity hydrogen is acquired from side I. Thus, the hydrogen separation process is realized based on the fact that the low‐purity hydrogen is consumed and high‐purity hydrogen is acquired. We achieved a high hydrogen separation rate (13.5 mL cm^?2 min^?1) at 950°C in a reactor equipped with a 0.5‐mm‐thick Ba_0.98Ce_0.05Fe_0.95O_3‐δ membrane. This research proofed that it is feasible to upgrade hydrogen purity using an MIEC oxygen permeable membrane. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1278–1286, 2017     

Photocrosslinking of halogen‐free flame‐retarded ethylene‐vinyl acetate copolymer by phosphorous‐nitrogen compound NP28

The photoinitiated crosslinking of halogen‐free flame‐retarded ethylene‐vinyl acetate copolymer (EVA) by the phosphorous‐nitrogen compound NP28 in the presence of photoinitiator and crosslinker and characterization of the related properties have been investigated by gel determination, heat extension test, thermogravimetric analysis (TGA), mechanical measurement, and thermal aging test. The photocrosslinking efficiency of EVA/NP28 blend and various factors affecting the crosslinking process, such as photoinitiator, crosslinker, NP28 content, and irradiation temperature, were studied in detail and optimized by comparison of gel content. The results show that the EVA/NP28 blend filled with 28.2 wt % NP28 with a thickness of 1.6 mm is homogeneously photocrosslinked to a gel content of above 80 wt % with 4.8 s UV‐irradiation under optimum conditions. The data from TGA, mechanical measurement, and thermal aging test give evidence that the thermal stability and mechanical properties of photocrosslinked EVA/NP28 blend are much better than those of the unphotocrosslinked one.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sol‐gel preparation and properties of Ag‐containing bioactive glass films on titanium

Ag‐containing bioactive glass films (Ag/Ca atomic ratios of 0, 5% and 10%) were sol‐gel prepared for bioactive and antibacterial modification of titanium. The gel powders calcined at 610°C are mainly amorphous confirmed by x‐ray diffraction, but small diffraction peaks of Ca₃SiO₅ and silver are detected. The film surface is porous with the pore size of ~200 nm. Silver‐rich sub‐micro particles with sizes of 100‐480 nm are present at the surface of Ag‐glass films. CaP phase, metallic silver and silica are detected by x‐ray photoelectron spectroscopy. The mean apparent bonding strength of the films is as high as 21±1 MPa measured by the pull‐off test. The potentiodynamic polarization test shows that the coated samples have better corrosion resistance than the polished sample. The Ag‐glass coatings and their wafer samples exhibit antibacterial activity against S. aureus. The coated samples are covered by apatite layer after soaked in the simulated body fluid for 2 weeks, demonstrating their bioactivity.     

Efficient metal‐free aerobic oxidation of aromatic hydrocarbons utilizing aryl‐tetrahalogenated N‐hydroxyphthalimides and 1,4‐diamino‐2,3‐dichloroanthraquinone

BACKGROUND: Hydrocarbon oxidation reactions are central to numerous processes that convert bulk chemicals into useful and higher‐value products. In this investigation, an efficient metal‐free catalytic system for aerobic oxidation of aromatic hydrocarbons was successfully established by synthesizing a series of aryl‐tetrahalogenated N‐hydroxyphthalimides and applying these compounds with 1,4‐diamino‐2,3‐dichloroanthraquinone (DADCAQ). RESULTS: Ethylbenzene was oxidized with 82.3% conversion and 86.9% selectivity to acetophenone catalyzed by the system of TCNHPI/DADCAQ under 0.3 MPa of molecular oxygen at 100 °C for 5 h. Other hydrocarbons were oxidized with high efficiency using this catalytic system. For example, indane can be converted completely to indan‐1‐one with 98.0% selectivity. CONCLUSION: A highly efficient metal‐free catalytic system consisting of TCNHPI and DADCAQ was developed for the oxidation of aromatic hydrocarbons with molecular oxygen. Aryl‐halogen substituents served to significantly increase the activities of the catalytic system. The results in this study can form the basis for the design of an efficient hydrocarbon oxidation process. Copyright © 2008 Society of Chemical Industry     

Bias‐free results in the spectrophotometric determination of chemical oxygen demand in bleached textile mill effluents

A calibration methodology that enables validation of the analytical procedure used in those cases where no placebo or standard reference material is available is applied here. The total Youden blank is used to eliminate the constant error component, and analytical measurements in the presence of the matrix at two different levels of the test portion, in order to avoid its interactive interference, are made. Moreover, the results obtained in the determination of chemical oxygen demand following a closed reflux spectrophotometric method are compared with those obtained when a definitive analytical method is applied, in order to show the absence of direct interference from the matrix. © 2002 Society of Chemical Industry     

High pressure adsorptive separation of ethylene and ethane on Na-ETS-10

Previously, we reported that Na-ETS-10 can be used to separate a mixture of ethylene and ethane from an industrial process stream under low pressure (101 kPa) with a binary bed selectivity of 5 at 298 K and 101.3 kPa. In this study, we show that selectivity improves considerably under high pressure conditions. Na-ETS-10 was used as a packed bed adsorbent to separate an ethylene/ethane 59/41 mixture over a pressure range of 101–2580 kPa and at two different temperatures (273 and 298 K). At these pressures, pure ethane gas raffinate streams prior to ethylene breakthrough are obtained. The extract phase obtained following desorption from the packed bed column contained up to 94% ethylene. The separation performance improved as adsorption column pressures increased. The ethylene/ethane bed selectivity achieved at 298 K and 2580 kPa was ∼11, more than double the previously reported selectivity under low pressure.     

Highly efficient separation of methane from nitrogen on a squarate‐based metal‐organic framework

Highly selective capture of methane from nitrogen is considered to be a feasible approach to improve the heating value of methane and mitigate the effects of global warming. In this work, an ultramicroporous squarate‐based metal‐organic framework (MOF), [Co₃(C₄O₄)₂(OH)₂] (C₄O₄^2? = squarate), with enhanced negative oxygen binding sites was synthesized for the first time and used as adsorbent for efficient separation of methane and nitrogen. Adsorption performance of this material was evaluated by single‐component adsorption isotherms and breakthrough experiments. Furthermore, density functional theory calculation was performed to gain the deep insight into the adsorption binding sites. Compared with the other state‐of‐the‐art materials, this material exhibited the highest adsorption selectivity (8.5–12.5) of methane over nitrogen as well as the moderate volumetric uptake of methane (19.81 cm³/cm³) under ambient condition. The unprecedented selectivity and chemical stability guaranteed this MOF as a candidate adsorbent to capture CH₄ from N₂, especially for the unconventional natural gas upgrading. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3681–3689, 2018     

Combined Effect of Agitation/Aeration and Fed‐Batch Strategy on Ubiquin‐ one‐10 Production by Pseudomonas diminuta

The effects of aeration rate and agitation speed on ubiquinone‐10 (CoQ10) submerged fermentation in a stirred‐tank reactor using Pseudomonas diminuta NCIM 2865 were investigated. CoQ10 production, biomass formation, glycerol utilization, and volumetric mass transfer coefficient (k_La) were affected by both aeration and agitation. An agitation speed of 400 rpm and aeration rate of 0.5 vvm supported the maximum production (38.56 mg L^–1) of CoQ10 during batch fermentation. The fermentation run supporting maximum production had an k_La of 27.07 h^–1 with the highest specific productivity and CoQ10 yield of 0.064 mg g^–1h^–1 and 0.96 mg g^–1 glycerol, respectively. Fermentation kinetics performed under optimum aeration and agitation showed the growth‐associated constant (a = 5.067 mg g^–1) to be higher than the nongrowth‐associated constant (β = 0.0242 mg g^–1h^–1). These results were successfully utilized for the development of fed‐batch fermentation, which increased the CoQ10 production from 38.56 mg L^–1 to 42.85 mg L^–1.     

Efficient adsorptive desulfurization by task‐specific porous organic polymers

A task‐specific mesoporous organic polymer (TSPOP) with unique features like good porosity and rich aromatic phenyl groups was facilely made and utilized as a promising adsorptive desulfurization absorbent for the first time. The material exhibits an efficient saturated adsorption of dibenzothiophene (DBT), as high as 111.1 mg g^?1. In addition, the intrinsic mesoporous skeleton of TSPOP gave rise to a facile incorporation of uniform Ag(I) species inside the network which facilitated the uptake of organosulfur compounds. A significantly higher saturated DBT adsorption for Ag(I)‐loaded TSPOP reaches 203.7 mg g^?1 via a multiple‐site interaction. A detailed model study based on the density functional calculation provides a deeper understanding of the origin of this high activity. In addition to the π–π stacking between DBT and phenyl rings, there exists an additional π‐complexation adsorption with Ag(I) ions, thus, significantly improving the DBT capture performance. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1740–1746, 2016     

空分短期停车时间阈值对氧气生产调度的影响

针对钢铁企业高炉休风场景下的氧气生产调度问题,提出以空分短期计划性停车为主要手段的调度策略,并基于MILP方法建立了氧气系统的优化调度模型。调度模型的优化目标为整个规划周期内氧气高压管网的综合压力最小化。模型包含了空分和部分氧气压缩机短期停车再启动操作的约束条件,并结合实际情况考虑了前述设备的停车时间阈值和运行时间阈值。以国内某大型钢铁企业为实际案例,验证了调度模型的合理性与可行性,然后基于模型计算分析了空分停车时间阈值对调度目标的影响规律。分析结果表明,减小空分停车时间阈值有利于获得更优的调度目标,但空分停车时间阈值对优化目标的影响规律具有阶跃特性,而非简单的比例关系。     

Experimental investigation on possibility of oxygen enrichment by using gradient magnetic fields

This paper presents a novel method that uses the interception effect of gradient magnetic field on oxygen molecules to realize enrichment. The use of two opposite magnetic poles of two magnets at a certain distance forms a magnetic space having a field intensity gradient near its borders. When air injected into the magnetic space outflows from the magnetic space via its borders, oxygen molecules in the air will experience the interception effect of the gradient magnetic field, but nitrogen molecules will outflow from the magnetic space without hindrance. Thus, continuous oxygen enrichment is realized. The enrichment degree of oxygen reaches 0.65% when the inlet and outlet air flows are 40 mL/min and 20 mL/min, respectively, and the gas temperature is 298 K and the maximal product of magnetic flux density and its gradient is 563 T²/m (the distance between two magnetic poles is 1 mm). When the gas temperature rises to 343 K, the enrichment degree drops to 0.32%; and when the maximal product of magnetic flux density and field intensity gradient drops to 101 T²/m (the distance between two magnetic poles is 4 mm), the enrichment degree drops to 0.23%. The experimental results show that there is an optimal ratio between the inlet air flow and the outlet air flow. Under the experimental conditions in this paper, the value is about 2.0. It is demonstrated that the method presented in this paper can continuously enrich oxygen and has a higher enrichment degree than other oxygen-enrichment methods using magnetic separation. Translated from Journal of Beijing University of Chemical Technology, 2006, 33(5): 62–66 [译自: 北京化工大学学报]     

Formation of defect‐free polyetherimide/PIM‐1 hollow fiber membranes for gas separation

Dual‐layer hollow fiber membranes were produced from blends of Ultem and polymer of intrinsic microporosity (PIM‐1) with enhanced gas permeance. The effects of spinning parameters (take‐up speed and air gap distance) on gas separation performance were investigated based on the pristine Ultem. Selected spinning conditions were further adopted for the blend system, achieving defect‐free and almost defect‐free hollow fibers. Adding PIM results in a higher fractional free volume, 50% increments in gas permeance were observed for Ultem/PIM‐1 (95/5) and more than 100% increments for Ultem/PIM‐1 (85/15). Both O₂/N₂ and CO₂/CH₄ selectivities remained the same for Ultem/PIM‐1 (95/5) and above 80% of their respective intrinsic values for Ultem/PIM‐1 (85/15). The selective layer thickness ranges from 70 to 120 nm, indicating the successful formation of ultrathin dense layers. Moreover, minimum amounts of the expensive material were consumed, that is, 0.88, 1.7, and 2.3 wt % PIM‐1 for Ultem/PIM‐1 (95/5), (90/10), and (85/15), respectively. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3848–3858, 2014     

Multichannel mixed‐conducting hollow fiber membranes for oxygen separation

A multichannel mixed‐conducting hollow fiber (MMCHF) membrane, 0.5 wt % Nb₂O₅‐doped SrCo_0.8 Fe_0.2O_3‐δ (SCFNb), has been successfully prepared by phase inversion and sintering technique. The crystalline structure, morphology, sintering behavior, breaking load, and oxygen permeability of the MMCHF membrane were studied systematically. The MMCHF membrane with porous‐dense asymmetrical microstructure was obtained with the outer diameter of 2.46 mm and inner tetra‐bore diameter of 0.80 mm. The breaking load of the MMCHF membrane was 3–6 times that of conventional single‐channel mixed‐conducting hollow fiber membrane. The MMCHF membrane showed a high oxygen flux which was about two times that of symmetric capillary membrane at similar conditions as well as a good long‐term stability under low oxygen partial pressure atmosphere. This work proposed a new configuration for the mixed‐conducting membranes, combining advantages of multichannel tubular membrane technology and conventional hollow fibers. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1969–1976, 2014     

Synthesis of monodisperse styrene/methyl methacrylate/acrylic acid latex using surfactant‐free emulsion copolymerization in air

Monodisperse styrene/methyl methacrylate/acrylic acid (St/MMA/AA) copolymer microspheres have been prepared with surfactant‐free emulsion polymerization in air. The presence of oxygen in the system not only caused an induction period but also decreased the average particle size (D_p). However increasing AA concentration ([AA]) gave a reduction in the induction period. The FTIR and NMR analysis of the latex copolymer confirmed that the correlation of the copolymer compositions with the feed compositions was much better at the lower [AA] than at the higher levels. The AA contents of the copolymers obtained in air were much lower than those of the copolymers obtained under N₂ protection. Decreasing [AA] led to decrease in the copolymer molecular weight and broadening of the molecular weight distribution, but the particle size distribution (δ/D_p) was unaffected. In addition, the average particle diameter (D_p) was proportional to [AA]^–0.255, and increasing comonomers feed content caused linear increase of D_p, and a monodisperse sample with final solids contents up to 34.2 wt % was obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Plasma polymer membranes from hexafluoroethane/hydrogen mixtures for separation of oxygen and nitrogen

Thin plasma polymer layers were produced employing feed mixtures of hexafluoroethane and hydrogen in an rf parallel-plate reactor. The layers are intended for use in membrane-based separation of oxygen and nitrogen. The hexafluoroethane-to-hydrogen mixture ratio was varied over a wide range, whereas all other process parameters (power, pressure, substrate temperature, and total gas flow) were held constant. The plasma polymers were examined by scanning electron microscopy, X-ray analysis, quantitative elemental analysis, and X-ray photoelectron spectroscopy. Permeability coefficients of oxygen and nitrogen and selectivities of the pure gases were determined. Pinhole-free plasma polymer films containing different amounts of fluorine, carbon, and hydrogen were formed. The distributions of fluorine and hydrogen in the products reflect their distributions in the feed gas. Traces of oxygen in some of the polymers are explained by the reaction of trapped radicals with atmospheric oxygen on the samples' exposure to air. Fluorine-containing carbon moieties such as CF₃, CF₂, and CF, and carbon moieties with fluorine atoms exclusively in secondary positions are present. A method of calculating crosslink density using the analytical data is described. The oxygen permeability coefficient and the selectivity of the plasma polymers increase as the hexafluoroethane content of the feed gas is raised. This behavior is attributed to growing solubility selectivity as a result of the rising fluorine content of the polymers. Maximum selectivity amounts to 3.4 at an oxygen permeability coefficient of 21 Barrer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1517–1526, 1997     

Oxygen enrichment from air through multilayer thin low‐density polyethylene films

Several multilayer thin low‐density polyethylene (LDPE) films were fabricated by blown thin film having a thickness of 7 μm and an area of 130 cm². They were characterized for their oxygen‐enrichment performance from air by a constant pressure–variable volume method in a round permeate cell with an effective area of 73.9 cm². The relationship between oxygen‐enrichment properties, including oxygen‐enriched air (OEA) flux, oxygen concentration, permeability coefficients of OEA, oxygen, nitrogen, as well as separation factor through the multilayer LDPE films, and operating parameters, including transfilm pressure difference, retentate/permeate flux ratio, temperature, as well as layer number, are all discussed in detail. It is found that all of the preceding oxygen‐enrichment parameters increase continuously with an increase of transfilm pressure difference from 0.1 to 0.65 MPa, especially for the trilayer and tetralayer LDPE films. The oxygen concentration and separation factor appear to rapidly increase within the retentate/permeate flux ratio below 200, and then become unchangeable beyond that, whereas the OEA flux and the permeability coefficients of OEA, oxygen, and nitrogen seem to remain nearly constant within the whole retentate/permeate flux ratio investigated, especially for the monolayer and bilayer LDPE films. The selectivity becomes inferior, whereas the permeability becomes superior, as the operating temperature increases from 23 to 31°C. The highest oxygen concentration was found to be 44.8% for monolayer LDPE film in a single step with air containing oxygen of 20.9% as a feed gas and operating pressure of 0.5 MPa at a retentate/permeate flux ratio of 340 and 23°C. The results demonstrate a possibility to prepare an oxygen‐enriching membrane directly from air, based on the easily obtained thin LDPE films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3013–3021, 2002; DOI 10.1002/app.2331