小型变压吸附制氧的真空解吸实验

通过实验研究了真空环境对小型变压吸附制氧的影响,考察了真空解吸与常压解吸两种条件下,进气压力、产氧量与均压时间对氧气纯度的影响。实验结果表明:真空解吸有利于提高氧气纯度和缩短产氧启动时间;真空解吸条件下,进气压力、产氧量与均压时间的变化对氧气纯度的影响规律与常压解吸时相同,但影响程度减弱。     

亚油酸乳状液体系氧化模型与求解

研究了恒表面氧压静置式无限氧补偿条件下乳状液中亚油酸的氧化,通过综合考虑气液边界传质阻力、水相扩散、油水边界乳化剂膜边界层阻力、多不饱和脂肪酸(PUFA)自催化氧化反应动力学,建立了扩散-氧化数学模型。采用非对称正交配置法处理特殊边界,求解偏微分方程组,计算了氧化过程中乳状液中氧和亚油酸在垂直于液膜方向的浓度分布,计算方法快捷、有效;结合数学模拟试验和实验值,确定了气液界面氧的液膜传质系数和水相中氧的扩散系数。实验验证该模型能较好地拟合静置式无限氧补偿条件下乳状液中氧的扩散和亚油酸的氧化过程。     

化学链燃烧中载氧体磨损和产生积碳的机制及抑制方法

磨损和积碳的产生都严重干扰化学链燃烧(CLC)的正常运行，磨损可造成载氧体的损耗，积碳可导致载氧体与燃料不能充分接触。载氧体的循环燃烧效率与CLC技术成本密切相关，是其进入商业化的关键。本工作针对载氧体的磨损和积碳抑制这两大主要问题进行了分析总结。阐述了CLC过程发生的详细反应及形成炭黑型积碳前驱物多环芳烃机制，总结了应对的可行方法，其中联合水蒸气和CO2喷射具有很好的前景。并在此基础上讨论了该领域的潜在研究需求。     

活性丁苯无规共聚物的氧偶联反应研究

研究了正丁基锂为引发剂，抽余油为溶剂的活性丁苯无规共聚合体系中氧偶联反应特点及氧偶联作用对Sn偶联丁苯无规共聚物影响。研究表明：随着氧含量、反应温度及反应时问的增加，氧偶联反应效率增加；GPC谱图表明，氧偶联反应形成双臂大分子峰，且Sn偶联的丁苯无规共聚物呈多峰分布：氧偶联反应对产物物理机械性能影响较小，但对产物动态力学性能及耐磨性能有一定的影响。     

组合型填料与焦炭填料塔中餐厅污水氧传递研究

本文分别以焦炭和自行开发的新型组合填料为塔内构件，对清水和餐厅污水中的氧传递特征进行了分析和实验研究，纯氧和空气供氧实验结果证实氧传递过程为液膜控制；通过实验测定了清水和餐厅污水在组合型填料和焦碳填料塔中曝气过程溶解氧的变化规律，从实验结果回归得到了上述填料塔内清水与餐厅污水氧转移系数计算关联式，计算值与实测值吻合较好；最后，对相同操作条件下焦炭与组合型填料在清水与餐厅污水中的氧转移系数进行了比较。     

Phonon dynamics in AlN lattice contaminated by oxygen

The phonon dynamics of wurtzite aluminum nitride contaminated by oxygen were investigated by employing the Raman back scattering, the Fourier Transform Infrared (FT-IR) reflectivity and absorption, and the Brillouin scattering techniques on unseeded polycrystalline samples of AlN built of single crystallites 1–5 mm in size. The six Raman active zone center optic modes were observed and identified. Throughout the oxygen contamination range (∼1, ∼2, and ∼6 at.%) of three samples investigated, the widths of the principal Raman modes were found to decrease with increasing the oxygen content in the single crystal. This behavior is interpreted as a change in the nature of the oxygen defect when the oxygen concentration exceeds 1 at.%. The FT-IR reflectivity spectrum exhibits two-mode behavior at low oxygen concentration, one-mode behavior tends to be dominant when the oxygen concentration increases, and only one-mode behavior can be observed at high oxygen concentration. These changes in the reststrahlen band with oxygen concentration support the hypothesis of a transition in the oxygen accommodation defect as the concentration of oxygen increases. The oxygen effects on the AlN optical parameters were investigated by calculating these optical parameters from the reflectivity data of single crystallites differing in their oxygen concentration. The FT-IR absorption measurements showed several absorption bands in the multiple-phonon region. A tentative interpretation is proposed in which these bands are considered to be due to oxygen impurity absorption and to a combination of several phonon branches at the Brillouin-zone boundaries. The absorption spectrum in the one-phonon region allowed us to obtain a reliable data on the phonon density of states function in bulk AlN. Lastly, three different configurations were used in Brillouin scattering measurements to achieve a complete determination of the elastic stiffness constants of AlN.     

Oxygen Diffusion in Nickel Ferrous Ferrite

The diffusion coefficients of oxygen in single crystals of nickel ferrite with Fe/Ni=3.4 were determined as a function of oxygen stoichiometry between 1140° and 1340°C. The diffusion kinetics were followed by measuring the rate of exchange of ¹⁸O between the gas and solid slabs of ferrite, and the oxygen stoichiometry was established by controlling total pressure of oxygen in the gas phase. At higher oxygen contents, the diffusion coefficient is independent of stoichiometry and is given by D =10^-2.3exp cm²/s. At low oxygen contents the diffusion rate depends strongly on oxygen stoichiometry and is smaller. In polycrystalline ferrite the diffusion at 1197°C is 40 times faster than in single crystals but shows the same dependence on oxygen stoichiometry. Probable diffusion mechanisms are discussed.     

Atom-resolved noncontact atomic force microscopic and scanning tunneling microscopic observations of the structure and dynamic behavior of CeO2(1 1 1) surfaces

Atomic-scale structures and dynamic behaviors of CeO₂(1 1 1) surfaces were imaged by noncontact atomic force microscopy (NC-AFM) and scanning tunneling microscopy (STM). Hexagonally arranged oxygen atoms, oxygen point vacancies, multiple oxygen vacancies, and hydrogen adatoms at the surfaces were visualized by atom-resolved NC-AFM observations. Multiple defects were stabilized by displacement of the surrounding oxygen atoms around the multiple defects, which gave enhanced brightness in the NC-AFM image due to a geometric reason. Multiple defects without reconstruction of the surrounding oxygen atoms were reactive and were healed by exposure to O₂ gas and methanol at RT. Successive NC-AFM and STM measurements of slightly reduced CeO₂(1 1 1) surfaces revealed that hopping of surface oxygen atoms faced to the metastable multiple defects was thermally activated even at room temperature (RT) and more promoted at higher temperatures. Heterogeneous feature of the reactivity of surface oxygen atoms with methanol was imaged by successive NC-AFM observations. These observations gave a new insight for understanding the surface structures and behavior of CeO_2−x with the facile oxygen reservoir and oxidation–reduction properties related to the unique catalysis.     

中后期不同溶氧水平对赖氨酸发酵的影响

发酵过程中合理且充分供氧是提高L-赖氨酸发酵产量的主要途径之一,实际生产中溶氧控制策略又往往难以进行具体化操作,尤其是发酵中后期的溶氧水平直接决定了发酵生产的水平.通过5 L发酵罐实验分析中后期溶氧水平对赖氨酸发酵的影响,研究了不同溶氧水平条件下的发酵规律.实验数据表明,赖氨酸发酵中后期溶氧水平控制在60%~80%内,可以明显提高发酵的终点酸、转化率、酸固比和单罐总酸等生产指标,与正常控制水平(40%~60%)相比,依次分别提高了7.30%、3.08%、0.92%、5.48%.     

Influence of oxygen content on structure and properties of pressurelessly sintered aluminum-nitride- and zirconium-boride-doped silicon-carbide ceramics

SiC is a widely used material. Understanding how oxygen content affects the SiC structure and properties is crucial. In this paper, heat treatment was used to prepare SiC powder samples with different oxygen contents, which were doped with AlN and ZrB₂ and were densified by pressureless sintering at 2050 °C. The effect of oxygen content on the sintered SiC structure was determined by X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The results indicated that the oxygen content influenced the SiC phase composition, grain boundaries, and densification. Additionally, the interaction between oxygen defects and AlN played an important role in sintering. The nanoindentation, alternating-current impedance, and thermal conductivity of the densified SiC specimens were also evaluated to elucidate the influence of the oxygen content on the densified-SiC functional properties. The results revealed that the oxygen content affected all the measured mechanical, electrical, and thermal properties. Furthermore, surface oxygen impurities suggested that oxygen content had similar critical effects on both the densified SiC structure and properties.     

Surface modification of aromatic polyamide film by remote oxygen plasma

Surface modification of poly(p-phenylene terephthalamide) (PPTA) film by a remote oxygen plasma treatment has been investigated from a viewpoint of comparison with a direct oxygen plasma treatment. We call the modification procedure in a space far away from the oxygen plasma zone “the remote oxygen plasma treatment,” and the modification procedure in a space just in the oxygen plasma zone (a conventional oxygen plasma treatment) “the direct oxygen plasma treatment.” In a space far away from the plasma zone, oxygen radicals rather than electrons and oxygen ions are predominant, and the PPTA film can be modified by the remote oxygen plasma treatment into a hydrophilic surface without heavy degradation of the PPTA film. The PPTA film surfaces modified by the remote oxygen plasma treatment were analyzed with contact angle measurement, scanning microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 831–840, 1997     

Ignition properties of polymers evaluated from ignition temperature and ignition limiting oxygen index

An apparatus for measuring ignition temperature and ignition-limiting oxygen index was devised in order to study ignition properties of polymers. Ignition limiting oxygen index, which was suggested by the limiting oxygen index (ASTM D2863-70), was defined as the minimum volume fraction of oxygen required for ignition to occur in a slowly rising gaseous atmosphere. The ignition temperatures and the ignition limiting oxygen indexes of typical polymers were measured by this apparatus. Polymers which produced more ethylene by pyrolysis tend to have lower ignition temperatures. In the case of the same kinds of polymers, plots of ignition temperatures versus ignition limting oxygen indexes gave nearly straight lines (Fig. 3), but the straight line of depolymerization-type polymers differed from that of random degradation-type polymers differed from that of random degradation-type polymers. In most polymers, ignition limiting oxygen indexes were nearly proportional to limiting oxygen indexes, but in the cases of hard poly(vinyl chloride) and soft poly(vinyl chloride), the plots did not follow this relation (Fig. 4). Ignition properties of self-extinguishing polymers were also studied.     

Singlet oxygen oxidation of lipids resulting from photochemical sensitizers in the presence of antioxidants

Singlet oxygen produced by photochemical sensitizers may play an important role in the oxidation of lipids in foods. Therefore, we studied the singlet oxygen oxidation of lipids and the scavenging ability of antioxidants. Singlet oxygen was generated using the photosensitizer rose bengal. The oxidation products of lipids and antioxidants were separated by high-performance liquid chromatography and monitored using post-column chemiluminescence and/or iodometric detection. The competitive reaction rates of various antioxidants and lipids were studied to elucidate the roles played by antioxidants in the prevention of food oxidation by singlet oxygen.     

Effect of α-, β-, γ-, and δ-Tocotrienol on the Singlet Oxygen Oxidation of Lard

The impacts of four different types of tocotrienol homologues on the singlet oxygen oxidation of lard were evaluated by measuring the headspace oxygen content and the peroxide value. Singlet oxygen oxidation of lard was induced by chlorophyll photosensitization. Samples of 0.100, 0.250, and 0.400 M lard in methylene chloride containing chlorophyll and α‐, β‐, γ‐, or δ‐tocotrienol were prepared and stored under light at 3,000 lux for 4 h. All tocotrienol homologues at 1.20 mM significantly prevented the singlet oxygen oxidation of lard. Chlorophyll under light produced singlet oxygen at 1.09 μmol oxygen/mL headspace/h. A steady state kinetic study showed that tocotrienols reduced the singlet oxygen oxidation of lard by quenching the singlet oxygen. Singlet oxygen reacted with lard at 6.50 × 10⁴M^?1 s^?1. α‐, β‐, γ‐, and δ‐tocotrienol quenched singlet oxygen with the rate of 2.16, 1.99, 2.05, and 0.800 × 10⁷M^?1 s^?1, respectively. Among them, α‐tocotrienol significantly prevented singlet oxygen oxidation of lard.     

Oxygen Fugacity Control in Nonflowing Atmospheres: I, Experimental Observations in CO/CO2 and O2/N2 Mixtures

The performance of a stabilized zirconia sensor and electrochemical oxygen pump combination in the isothermal control of oxygen fugacity in a nonflowing atmosphere was studied in a closed furnace system in the temperature range of 800° to 1100°C. Under certain conditions, large differences in oxygen pressure were found between sensors at the same constant temperature in close proximity to each other. This result reflected the existence of a stable steplike oxygen fugacity "front" in the furnace, separating regions which differed by several orders of magnitude in oxygen fugacity. This oxygen pressure profile in the furnace resulted from the steady-state transport of oxygen from oxygen leakage sources to the pump. The existence, magnitude, and position of the oxygen fugacity front were found to depend on the gas-phase composition, the relative locations of the leakage sources and the pump, the oxygen fugacity of the reference electrode, and the magnitude of the oxygen flux in the gas phase.     

Chemical looping oxidative propane dehydrogenation controlled by oxygen bulk diffusion over FeVO4 oxygen carrier pellets

The oxygen distribution and evolution within the oxygen carrier exert significant influence on chemical looping processes. This paper describes the influence of oxygen bulk diffusion within FeVO₄ oxygen carrier pellets on the chemical looping oxidative propane dehydrogenation (CL-ODH). During CL-ODH, the oxygen concentration at the pellet surface initially decreased and then maintained stable before the final decrease. At the stage with the stable surface oxygen concentration, the reaction showed a stable C₃H₆ formation rate and high C₃H₆ selectivity. Therefore, based on Fick’s second law, the oxygen distribution and evolution in the oxygen carrier at this stage were further analyzed. It was found that main reactions of selective oxidation and over-oxidation were controlled by the oxygen bulk diffusion. C₃H₈ conversion rate kept decreasing during this stage due to the decrease of the oxygen flux caused by the decline of oxygen gradient within the oxygen carrier, while C₃H₆ selectivity increased due to the decrease of over-oxidation. In addition, reaction rates could increase with the propane partial pressure due to the increase of the oxygen gradient within the oxygen carrier until the bulk transfer reached its limit at higher propane partial pressure. This study provides fundamental insights for the diffusion-controlled chemical looping reactions.     

碳酸铵沉淀剂对储氧材料性能的影响

以碳酸铵为沉淀剂制备一系列高比表面积、高储氧性能的储氧材料,表征了其物相组成,同时对其储氧性能和比表面积进行了测定。结果表明,得到的前驱体为晶型沉淀,pH值、陈化温度、反应物浓度对材料的储氧性能、比表面积、抗老化性能有着不同程度的影响。     

Quenching by oxygen of excited states of dyes on cotton investigated with diffuse reflectance laser flash photolysis and singlet oxygen detection

Diffuse reflectance laser flash photolysis was successfully employed to study the triplet states of dyes adsorbed on or chemically attached to cotton. This technique, together with the detection of singlet oxygen from dyes on cotton, made it possible to investigate the diffusion of oxygen in cotton fibres and the mobility of dyes adsorbed onto cotton. Absorption by the triplet states of aluminium phthalocyanine chloride and eosin and the phosphorescence of singlet oxygen produced by sensitisation with rose bengal was used to monitor oxygen diffusion and dye mobility by measuring differences in triplet lifetimes, singlet oxygen lifetimes and in signal intensities. It was found that swollen cotton allows diffusion of oxygen in the fibres. However, a noticeable effect on the triplet state of adsorbed aluminium phthalocyanine chloride is only observed if oxygen is removed or added by thorough evacuation or oxygenation of the samples over several days. Singlet oxygen was quenched dynamically by adsorbed dyes, which were found to be immobilised on the fibres, demonstrating that oxygen is mobile within the fibres at the molecular level.     

CONSUMPTION OF THE MOLECULAR OXYGEN IN POLYMERIZATION SYSTEMS USING PHOTOSENSITIZED OXIDATION OF DIMETHYLANTHRACENE

It is well known that the presence of oxygen in free radical polymerization systems leads to an inhibition period and a lowered ultimate conversion. In this contribution, we report a method for consuming molecular oxygen photochemically before the polymerization takes place, thereby allowing the reaction to proceed in an oxygen-free environment. The method is based on the generation of singlet oxygen by reaction of the ground state oxygen with the excited triplet state of the singlet oxygen generator (a porphyrin, Znttp). The singlet oxygen is then consumed by reaction with a second compound (the singlet oxygen trapper, dimethylanthracene). The possible factors that might affect the efficiency of the singlet oxygen generation/trapping processes were discussed and the effectiveness of a dimethylanthracene/Znttp combination for consumption of oxygen was investigated in two acrylate systems of different viscosity.     

摇瓶发酵参数的测定及其应用的探索

研究制作了一种可在线检测发酵过程中气相氧、溶解氧及中间补料、采样的特殊摇瓶，取得了摇瓶规模下的菌体摄氧率、氧传递系数等重要工程参数，并以摇瓶所得摄氧率（ＯＵＲ）为依据进行发酵放大，通过质谱仪在线检测，验证发酵罐发酵与摇瓶发酵所得数据的异同。