生活填埋场覆盖层甲烷氧化研究进展

填埋场是重要的人为甲烷释放源。填埋场覆盖层是控制填埋场甲烷无序释放的最后屏障。本文系统介绍了覆盖层甲烷氧化的微生物机制以及影响覆盖层甲烷氧化的因子。系统分析微量气体组分对甲烷氧化的影响与机制,对于丰富填埋场覆盖层甲烷氧化理论,实现填埋场甲烷减排具有指导意义。     

甲烷二氧化碳氧气氧化重整的研究

在镍基催化剂化的甲烷二氧化碳重整反应中加入氧气使得热性的甲烷选择性氧化与吸热的二氧化碳重整责任中反应能够同时进行。实验结果表明，氧气的加入降低了反应温度，同时还可以在一定程度上调节Ｈ２ＣＯ比。良好的催化剂稳定性可能是由于镍粒子在表面镧氧化物中的分布的结果。     

甲烷二氧化碳氧气氧化重整抗积碳催化剂的研究

采用溶胶－凝胶方法合成了Ｌａ２Ｚｒ２Ｏｘ烧绿石，这种烧绿石结构稳定，并具有合适的中孔以及合理的比表面积，是一种具有潜在应用前景的催化剂载体，以Ｌａ２Ｚｒ２Ｏｘ烧绿石为载体制备的负载镍催化剂，在甲烷二氧化碳氧气氧化重整反应中显示了极好的稳定性。     

氧气浓度对好氧甲烷氧化耦合反硝化过程的影响

好氧甲烷氧化耦合反硝化反应是一个重要连接甲烷和氮循环的过程。文中考察了4种氧气浓度(2.5%、5%、10%和21%)对好氧甲烷氧化耦合反硝化反应的影响。试验结果表明,21%的氧气浓度可以促进甲烷氧化,提高体系中溶解性有机碳的浓度,同时一定程度上抑制甲烷氧化耦合反硝化反应。甲烷浓度为6%～8%时,10%氧气浓度下甲烷氧化耦合反硝化反应的脱氮效率最高。     

氧气氧化乙二醛合成乙醛酸

在酸性介质中 ,用氧气氧化乙二醛溶液 ,可快速合成乙醛酸。乙二醛转化率 98% ,乙醛酸产率 82 % ,对乙醛酸选择性 83 %。优化合成条件是 :n(氧 )∶n(乙二醛 ) =0 5 5∶1 0 0 ,氧气压力为0 12MPa ,介质pH <1,反应温度 45～ 6 0℃ ,反应时间 3h。     

氧气氧化是PTA氧化工艺的发展方向

用氧气代替空气作分子氧化剂,是石油化学工业的一个趋势。生产PTA用氧气氧化PX工艺能增加反应速率,缓和反应条件,减少副反应,降低消耗,提高产品质量,提高反应设备生产强度,有利于环境保护。分析氧气氧化工艺的安全性和经济性,指出该工艺有良好的工业应用前景,是PTA氧化工艺的发展方向。     

丙烯氧气氧化制环氧丙烷工艺开发进展

以分子氧为氧源的丙烯环氧化反应是近年来发展起来的一种清洁型环氧丙烷合成技术。综述了丙烯氧气氧化工艺的开发背景、开发进展及其经济性。丙烯与O₂氧化工艺以及丙烯与O₂、H₂氧化工艺因反应过程和反应机理不同而采用相异的催化剂和工艺条件,虽然丙烯氧气氧化工艺存在产率低、生产成本高的缺点,但作为具有最佳原子经济性和较低投资费用的新工艺路线,具有工业化应用前景。     

甲烷部分氧化制甲醇及甲醛

综述了甲烷部分氧化制甲醇及甲醛工艺在催化剂、载体、选择反应条件及氧化反应机理等方面的研究进展。建议研制开发新型的复合型催化剂。     

液相催化氧气氧化菲制取菲醌

在戊酸中,钴盐、锰盐、铈盐、溴化物做催化剂,在温度120～130℃,压力1.0～1.2MPa,由氧气氧化菲制取菲醌,纯度90.4％,收率89.5％。本文研究了溶剂、反应物的浓度、溶剂的含水量和杂质对反应产率的影响。     

甲烷直接氧化制甲醇研究进展

叙述了近年来国内外关于甲烷直接氧化制甲醇的研究成果, 包括甲烷气相均相反应、气固催化反应、液相催化反应及反应机理讨论等, 并展望了进一步研究和开发的方向。     

Microbial aerobic oxidation of methane in paddy soil

The microbial aerobic oxidation activity of methane, the population of aerobic methane oxidizers and the factors influencing the activity of methane oxidation were investigated in three types of paddy rice soil in Zhejiang Province, China. Methane oxidation activity was different among Huangsong paddy soil developed from fluvo-aquic soil, Old huangjinni paddy soil developed from quaternary red clay and Qingzini paddy soil developed from coastal saline soil. The Huangsong paddy rice soil showed the highest activity of methane oxidation. Different methane oxidation activity and populations of methane-oxidizing bacteria were found in various Huangsong soil samples that had different plant-cover. Methane oxidation returned to the same level after these soil samples were incubated and induced by extra added methane. The population of methane oxidizing bacteria was at maximum within the peak-tillering, heading and flowering stages, during which the largest population of methanogenic bacteria also appeared. Temperatures from 25 to 35 °C and pH from 6 to 8 were the optimum conditions for aerobic oxidation of methane in paddy rice soil. Soil particle size also affected the activity of methane oxidation.     

Characteristics of methane oxidation in a flooded rice soil profile

Laboratory experiments were conducted to study the variation of CH₄ oxidation patterns in flooded rice soil profiles. The results indicated that surface soil presented the strongest CH₄ oxidation activities as shown by the highest values of the two kinetic parameters of CH₄ oxidation, V_max and K_m in the ecosystem without rice plants. V_max and K_m decreased significantly from top to bottom in the paddy rice soil profile, ranging from 12.5 to 1.2 μg h^-1 g^-1 and 165 to 4.1 μg g^-1, respectively. In addition, we studied the effect of headspace N₂, O₂ and their ratio on CH₄ emission and oxidation to provide information on the sensitivity of methanogens and methanotrophs to soil redox change resulted from gas transportation through arenchyma. Methane emission rate increased, however, CH₄ oxidation rate decreased with a decrease of O₂ concentration in the headspace. Headspace H₂ increased CH₄ emission rate substantially. In addition to H₂ being a substrate for CH₄ formation, the change of soil redox potential to a considerably low level H₂ should also contribute to the increase in CH₄ emission. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of oxygen mobility in solid catalyst on transient regimes of catalytic reaction of methane partial oxidation at short contact times

Mathematical modeling of the effect of the oxygen mobility in a solid oxide catalyst on the dynamics of transients of fast catalytic reactions has been carried out. The analysis was based upon the redox mechanistic scheme with a due regard for diffusion of oxygen from the bulk of catalyst to its surface. Parameters of kinetic and mathematical models were selected via fitting of the experimental data for methane selective oxidation into syngas on 1.4%Pt/Gd_0.2Ce_0.4Zr_0.4O _x catalyst. The range of the Thiele parameter (φ) where the oxygen bulk diffusion affects the most strongly reaction transients corresponds to φε [0.3 ÷ 7]. For high-surface-area oxide catalysts, the bulk oxygen diffusion coefficients corresponding to this range of the Thiele parameter are in the range of 10^–18 ÷ 10^–13cm²/s.     

The effect of agriculture on methane oxidation in soil

Aerobic soils are an important sink for methane (CH₄) contributing up to 15% of annual global CH₄ destruction. However, the sink strength is significantly affected by land management, nitrogen (N) fertilizers and acidity. We tested these effects on samples taken from the Broadbalk Continuous Wheat, Park Grass permanent grassland and Broadbalk and Geescroft Wilderness experiments at Rothamsted. The rates of uptake from the atmosphere of both enhanced (10 ppmv) and ambient (2 ppmv) concentrations of CH₄ were measured in laboratory incubations of soil cores under controlled conditions. The most rapid rates of uptake were measured in soil from deciduous woodland at pH 7 (measured in water); acidic (pH 4) woodland soil showed no net CH₄ oxidation. While disturbance of the cores used in the experiments did not affect the rate of CH₄ uptake, extended (150 years) cultivation of land for arable crops reduced uptake rate by 85% compared to that in the soil under calcareous woodland. The long-term application of ammonium- (NH₄) based fertilizer, but not nitrate- (NO₃) based fertilizer, completely inhibited CH₄ uptake, but the application for the same period of farmyard manure that contained more N than the fertilizer had no inhibitory effect. Although the effects of agricultural practice on the oxidation of CH₄ in soil are significant, the differences in oxidation rates between land use types are even greater. The likely effects of forest clearance, agricultural intensification and anthropogenic emissions of CH₄ over the last 2500 years have been estimated for the United Kingdom. The calculations indicate that 54% of the current CH₄ uptake by UK soils is the result of increased CH₄ mixing ratio. They also indicate that land use change has decreased the potential sink strength by 62% or 37 kt CH₄ g^-1. In countries with much larger land areas than the UK, such as China, aerobic soil is likely to be a more significant factor in calculating net fluxes of CH₄. It is important that the impacts of different agricultural managements and land use systems are understood and quantified so that the best possible estimate of CH₄ sinks is calculated for comparison with sources. This revised version was published online in August 2006 with corrections to the Cover Date.     

硝态氮/亚硝态型厌氧甲烷氧化在污染控制中的应用进展与探索

硝态氮/亚硝态型厌氧甲烷氧化（NO_x-DAMO）过程在还原硝酸盐/亚硝酸盐的同时将甲烷氧化为二氧化碳,在全球碳氮循环中起着重要作用。从应用的角度看,利用NO_x-DAMO原理进行环境中甲烷和氮素污染控制也值得关注。本文介绍了在MBR和MBfR等反应器中应用NO_x-DAMO过程单独或与其他工艺联合处理模拟废水和实际废水的研究中,污染物去除速率和效率显示出了工程实用价值。指出基于NO_x-DAMO原理开发垃圾渗滤液和填埋气协同处理工艺、煤层气厌氧生物氧化工艺的研究值得探索,其可能为无规模利用价值的生活垃圾填埋气和煤层气的处理提供低成本和环境友好的解决方案。今后的研究方向应该是在继续深入NO_x-DAMO微生物的生理特性研究的同时,需要面向不同应用需求广泛开展工艺开发与优化研究。     

Supercritical water oxidation treatment of humic acid as a model organic compound of landfill leachate

Landfill leachate is a complex and variable effluent, rich in organic and inorganic matters resistant to decomposition, and is an extreme pollutant. Humic acids (HA) are some of the most refractive substances in the leachates, which is the reason why they have been used as an organic model. The degradation of an HA solution through supercritical water oxidation (ScWO) was evaluated under a constant pressure of 22.5 MPa, temperatures from 400°C to 600°C, and reaction times from 15 to 60 seconds. The results showed that the most influential factor was temperature and it guided the operational conditions of the ScWO for the landfill leachate (22.5 MPa, 600°C, and 60 seconds). The landfill leachate treatment promoted high removal rates of true colour (87%), total dissolved solids (94%), nitrate (70%), and total phosphorus (96%). In addition, it removed 57% of the COD, which was similar to the HA removal rate (61%) under the same operational conditions. This indicates that HA are an adequate organic model for landfill leachates. The results suggest that ScWO is a clean and promising treatment technology that can be applied to landfills and can have even better results if used in combination with oxidizers and catalysts, or with the use of higher temperatures.     

有氧补偿乳状液中多不饱和脂肪酸氧化模型

研究了恒表面氧压搅拌式有氧补偿条件下乳状液中多不饱和脂肪酸(PUFA)的氧化。通过综合考虑气液边界传质阻力、油水边界乳化剂形成的液膜边界层阻力、PUFA自催化氧化反应动力学,建立了相应的扩散-氧化数学模型。实验验证该模型能较好地拟合搅拌式有氧补偿条件下乳状液中氧的扩散和亚油酸的氧化过程,并在乳化剂浓度变化对乳状液中PUFA氧化的影响方面表现出很好的适用性。研究对揭示乳状液中PUFA的氧化机制最终有效控制PUFA的氧化具有重要的理论研究价值。     

电催化氧化法处理垃圾渗滤液中氨氮的研究

采用电解槽对垃圾渗滤液进行电解催化处理研究,考察不同的极板间距、电流密度、氯离子的质量浓度等对电解效果的影响。结果表明,极板间距为1.0 cm,电流密度为10 A/dm2,氯离子质量浓度为5 000 mg/L时,该法对中等浓度的垃圾渗滤液中的氨氮有较好的处理效果,对氨氮的去除率能达到97.3%。     

基于Ba-Ce-Co-Fe-O膜反应器的甲烷部分氧化反应研究

为开发稳定性和透氧量俱佳并适用于甲烷部分氧化反应(POM)的透氧膜材料,采用溶胶凝胶工艺合成了具有纯相钙钛矿结构的BaCe0.1Co0.4Fe0.5O3-δ混合导体陶瓷材料。POM操作结果表明:BaCe0.1Co0.4Fe0.5O3-δ膜反应器透氧量高于同类材料,875℃时透氧量达到了8.9 mL/(cm2.m in)。在1 000 h寿命实验中,膜反应器各项反应指标没有出现任何衰减,反应性能稳定,甲烷转化率和CO的选择性都在97%以上。SEM表征表明,反应后膜片表面微观结构的变化虽然不可避免,但是其仍然保持比较完整的结构。因此,该材料良好的透氧量和稳定性说明其具有较好的应用前景。     

Laboratory study of methane oxidation in paddy soils

Methane oxidation in paddy soils was investigated under laboratory conditions. Paddy soils collected before early rice transplanting could not oxidize atmospheric CH₄ but could oxidize CH₄ when the concentration exceeded 10 μl l^-1. Initial CH₄ oxidation rate increased with the increase of initial CH₄ concentration. Soil with the maximum potential to produce CH₄, also had the maximum CH₄ oxidation activity and the maximum emission flux from paddy soil. High CH₄ concentration stimulated the oxidation of CH₄. After 10 days' incubation under atmosphere containing 1000 μl^-1 or 10⁴ μl l^-1 CH₄, the soil which could not oxidize atmospheric CH₄ was able to oxidize it. This revised version was published online in August 2006 with corrections to the Cover Date.