挥发性有机化合物催化氧化催化剂的制备和性能研究

研制出用于催化氧化废气中挥发性有机化合物（ＶＯＣ）的非贵金属氧化物催化剂,在固定床上,处理含醋酸丁酯的模拟气,考察了空速、浓度等因素对催化剂活性的影响及催化剂的耐热性能,当空速为５０００ｈ＾－１,进气温度为２２０℃、醋酸丁酯质量浓度为２．４～５．８ｇ／ｍ＾２时,醋酸丁酯的去除率〉９８％,而且该催化剂人具有较高的热稳定性。     

催化燃烧处理有机废气及催化剂中毒的防止

研究了在Ｐｔ、Ｐｄ、Ｃｅ多组分蜂窝状催化剂上乙醇、环己烷和苯的氧化性能及水蒸气对催化剂活性的影响,探讨了如何防止硫化氢和甲硫醇引起的催化剂中毒。     

催化氧化法处理氯甲烷废气

用催化氧化法处理氯甲烷废气，考察了各种因素对催化氧化处理效果的影响。实验结果表明：在反应温度为350℃、空速为4800h^-1、空气与氯甲烷废气的体积比为15的条件下，氯甲烷转化率和总烃转化率均大于99％，催化氧化过程中基本不产生光气；催化氧化反应后尾气中的HCl用NaOH溶液作吸收剂的吸收效果较好；γ—Al2O3为载体的催化剂活性基本稳定。     

铁铈钛复合氧化物催化剂的制备及其选择性催化还原NO的性能

采用共沉淀法制备了一种新型催化剂——铁铈钛复合氧化物催化剂,研究了Fe掺加量、体积空速以及H2O和SO2的加入对其选择性催化还原NO性能的影响;采用XRD和SEM等手段对催化剂的结构和形貌进行了表征。表征结果显示,Fe的掺加使催化剂表面的颗粒更均匀,提高了催化剂的分散度。实验结果表明：以Ce（NO3）3,Fe（NO3）3?9H2O,TiOSO4?2H2O为原料、按n（Ce）∶n（Fe）∶n（Ti）=0.2∶0.8∶1配比制得的Ce0.2Fe0.8TiOx为催化剂,在反应温度250 ℃、反应时间3 h、体积空速25 000 h-1的条件下,NO去除率为99.8%,N2选择性为100%;Fe的掺加显著提高了Ce0.2Fe0.8TiOx催化剂的抗H2O和SO2的能力。     

整体式催化剂选择性催化氧化硫化氢

在堇青石蜂窝陶瓷基体上分两步涂覆了SiO₂和TiO₂两种涂层,再通过浸渍法制备了V₂O₅/TiO₂-SiO₂/堇青石整体式催化剂。采用BET、XRD、XRF、SEM和H₂-TPR等方法对催化剂进行了表征,并对催化剂的H₂S选择性催化氧化活性进行了评价。结果表明：V₂O₅负载量为20%（w）时,催化剂的活性最好;在反应温度180 ℃、空速3 000 h^-1、V（O₂）∶V（H₂S）=0.5的条件下,转化率达96.94%,硫产率达95.41%。在40 h的稳定性试验过程中,转化率稳定在96%左右,硫产率稳定在94%左右,催化剂的稳定性较好。与传统颗粒状催化剂相比,该整体式催化剂更具工业应用前景。     

蜂窝状Ce/Cr掺杂Cu基催化剂用于乙烷的催化燃烧

以蜂窝堇青石陶瓷为载体,采用浸渍法负载氧化铝涂层和活性组分,制备了蜂窝状Ce/Cr掺杂Cu基催化剂。运用BET,XRD,XPS,H₂-TPR技术对催化剂进行了表征,并对其乙烷催化燃烧活性进行了评价。表征结果显示,Ce/Cr掺杂提高了催化剂表面化学吸附氧的含量,提升了催化剂在较低温度下的氧化还原性能。实验结果表明：在入口乙烷质量浓度2 000 mg/m³、反应空速20 000 h^-1的条件下,Cu-Ce催化剂较Cu催化剂的T₅₀和T₉₀（乙烷转化率为50%和90%时的反应温度）分别降低了46 ℃和101 ℃,降幅高于Cu-Cr催化剂的38 ℃和78 ℃;较高反应空速（30 000 h^-1）对催化反应不利,乙烷浓度对催化剂活性的影响不明显;550 ℃下Cu-Ce催化剂对乙烷的转化率100 h内保持在99%以上,表现出良好的稳定性。     

催化燃烧法治理苯酐生产尾气

研制出一种治理苯酐生产尾气用的催化剂,在φ20毫米的固定床反应器上.模拟苯酐生产尾气中可燃物浓度,对空速、催化剂床层高度及水蒸汽等影响因素进行了考察,并进行了耐硫(SO_2)性、热稳定性试验以及1000小时实际气体验证。结果表明该催化剂活性高,性能稳定,当空速10000时~(-1),进气温度为230—240℃时,顺酐去除率>98％。     

氧化亚氮分解催化剂的研究进展

对近年来N2O分解反应催化剂的研究进行了综述,包括离子交换分子筛、过渡金属氧化物、负载型贵金属等催化剂.对于离子交换分子筛催化剂而言,分子筛骨架结构、交换离子类型、制备方法均对催化剂的活性有一定影响.在过渡金属氧化物催化剂中,Co-A1、Co-Mn-A1等类水滑石衍生复合氧化物的比表面积和催化活性均较高,在其表面添加适量的碱金属或碱土金属助剂可进一步提高催化活性.在贵金属催化剂中,还原型载体负载的催化剂活性较高.Co基复合氧化物负载Au催化剂有望成为实用型的N2O低温分解催化剂.     

中等温度SCR脱硝催化剂在高硫、高钙条件下的适应性研究

介绍了在模拟高硫、高钙灰的试验烟气环境下,钒钛系中温SCR脱硝催化剂在NH3/NOx、SO2、空速、O2、H2O等参数变化时对脱硝效率的影响.试验还对催化剂的抗毒性能、再生性能进行了初步研究,可为工业化的催化剂选型提供参考.     

DS—Ⅱ催化剂脱硫脱氮技术的实验研究

以纯SO2及燃煤电厂烟气作实验气,利用积分法固定床CFB方式进行了DS－Ⅰ型催化剂与活性炭催化性能的对比试验,对不同还进行了不同烟气温度、SO2浓度、湿度、烟气流速等工艺参数对DS－Ⅰ型催化剂催化性能的影响试验。对不同催化剂进行优化组合,可在除尘器后直接脱硫、脱氮、其脱硫率达86％、脱氮率达68％。催化剂经再生,可反复使用。     

Review of the kinetics of alkaline degradation of cellulose in view of its relevance for safety assessment of radioactive waste repositories

The degradation of cellulose (a substantial component of low- and intermediate-level radioactive waste) under alkaline conditions occurs via two main processes: a peeling-off reaction and a basecatalyzed cleavage of glycosidic bonds (hydrolysis). Both processes show pseudo-first-order kinetics. At ambient temperature, the peeling-off process is the dominant degradation mechanism, resulting in the formation of mainly isosaccharinic acid. The degradation depends strongly on the degree of polymerization (DP) and on the number of reducing end groups present in cellulose. Beyond pH 12.5, the OH^- concentration has only a minor effect on the degradation rate. It was estimated that under repository conditions (alkaline environment, pH 13.3-12.5) about 10% of the cellulosic materials (average DP = 1000-2000) will degrade in the first stage (up to 10⁵ years) by the peeling-off reaction and will cause an ingrowth of isosaccharinic acid in the interstitial cement pore water. In the second stage (10⁵-10⁶ years), alkaline hydrolysis will control the further degradation of the cellulose. The potential role of microorganisms in the degradation of cellulose under alkaline conditions could not be evaluated. Proper assessment of the effect of cellulose degradation on the mobilization of radionuclides basically requires knowing the concentration of isosaccharinic acid in the pore water. This concentration, however, depends on several factors such as the stability of ISA under alkaline conditions, sorption of ISA on cement, formation of sparingly soluble ISA-salts, etc. A discussion of all the relevant processes involved, however, is far beyond the scope of the presented overview.     

Study of Aging Characteristics of Ternary Blends of Polyethylenes—II

Six film samples of low-density polypropylene (LDPE)/linear LDPE (LLDPE)/high-density polypropylene (HDPE) with varying ratios of LDPE (20–45 ... wt%) and LLDPE (25–50 wt%) having a fixed amount of HDPE at 30 wt% were prepared by blown film extrusion technique. The samples were aged at four different temperatures, 55°, 70°, 85°, and 100°C, for four different time periods in the interval of between 150 hours and up to 600 hours. The change in the structure of various constituents and the formation of various oxygenated (peroxy and hydroperoxy) and unsaturated groups during thermo-oxidative degradation was discussed by infrared spectroscopy. The visiosity-average molecular weight was found to have decreased slowly in the initial aging hours and temperatures, whereas it decreased by 10% with its previous value tensile strength that is, 100°C when aged for 600 hours. The tensile strength of the sample first increased by 67% at 55°C and 89% at 70°C up to 450 hours, whereas the values increased by 52.5% at 85°C and 33.9% at 100°C when aged for 150 hours and then decreased. The percentage elongation at break increased by 2.7% at 55°C and 10.7% at 70°C for 150 and 300 hours of aging, respectively, whereas the percentage decreased when aged at 85°C and 100°C for up to 600 hours of aging. The values of gel content (percent) increased and initial degradation temperature decreased with aging time and temperature.     

Calculation of carbon balances for evaluation of the biodegradability of polymers

Establishing carbon balances has been proven to be an applicable and powerful tool in testing biodegradability of polymers. In controlled degradation tests at a 4-L scale with the model polymer poly(-hydroxybutyrate) (PHB), it was shown that the degree of degradation could not be determined with satisfactory accuracy from CO₂ release alone. Instead, the course of degradation was characterized by means of establishing carbon balances for the degradation of PHB withAcidovorax facilis and a mixed culture derived from compost. Different analytical methods for determining the different carbon fractions were adapted to the particular test conditions and compared. Quantitative determination of biomass and residual polymer were the main problems in establishing carbon balances. Amounts of biomass derived from protein measurements depend strongly on assumptions of the protein content of the biomass. Selective oxidation of biomass with hypochlorite was used as alternative, but here problems arose from insoluble metabolic products. Determination of soluble components with the method of chemical oxygen demand (COD) also includes empirical assumptions but seems acceptable if the dissolved carbon fraction is in the range of some 10% total carbon. Results confirm both analytical assays and theoretical approaches, in ending up at values very close to 100%, within an acceptable standard deviation range under test conditions comparable to standard test practice.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts.     

Model of technological alternatives of production of sodium chromate (VI) with the use of chromic wastes

This article presents a mathematical model which describes the sodium chromate (VI) production process with the use of chromic waste as a substitution of natural raw materials. This model is a function of selected process parameters common for all of the examined alternatives and based on equations of material balance. Optimization of the elaborated technological alternatives of the production process with use of recycling of chromic waste has been evaluated by determining the extreme value of the quality indicator WJ. This indicator defines the quantity of waste created in the process. Optimization results enabled the selection of the optimal technological solution from all of the alternatives possible for use in industrial practice. Negative values of the indicator prove that there is the possibility of introducing to the process a larger quantity of waste than the one obtained in the process and transported to the storage heaps.     

化学品生物降解性的评价与预测

介绍了有机化学物质生物降解性的测定方法及其预测方法研究概况，并讨论了生物降解性评价的发展前景。     

Determination of the Burning Characteristics of a Slick of Oil on Water

The burning rate of a slick of oil on a water bed is characterized by three distinct processes, ignition, flame spread and burning rate. Although all three processes are important, ignition and burning rate are critical. The former, because it defines the potential to burn and the latter because of the inherent possibility of boilover. Burning rate is calculated by a simple expression derived from a one-dimensional heat conduction equation. Heat feedback from the flame to the surface is assumed to be a constant fraction of the total energy released by the combustion reaction. The constant fraction (χ) is named the burning efficiency and represents an important tool in assessing the potential of in situ burning as a counter-measure to an oil spill. By matching the characteristic thermal penetration length scale for the fuel/water system and an equivalent single layer system, a combined thermal diffusivity can be calculated and used to obtain an analytical solution for the burning rate. Theoretical expressions were correlated with crude oil and heating oil, for a number of pool diameters and initial fuel layer thickness. Experiments were also conducted with emulsified and weathered crude oil. The simple analytical expression describes well the effects of pool diameter and initial fuel layer thickness permitting a better observation of the effects of weathering, emulsification and net heat feedback to the fuel surface. Experiments showed that only a small fraction of the heat released by the flame is retained by the fuel layer and water bed (of the order of 1%). Ignition has been studied to provide a tool that will serve to assess a fuels ease to ignite under conditions that are representative of oil spills. Two different techniques are used, piloted ignition when the fuel is exposed to a radiant heat flux and flash point as measured by the ASTM D56 Tag Closed Cup Test. Two different crude oils were used for these experiments, ANS and Cook Inlet. Crude oils were tested in their natural state and at different levels of weathering, showing that piloted ignition and flash point are strong functions of weathering level.     

Mechanism of Microbial Degradation of Slow-Release Fertilizers

Methyleneureas are condensation products of urea and formaldehyde of different molecular mass and solubility; they are used in large amounts both as resins, binders, and insulating materials for industrial applications, as well as a slow-release nitrogen fertilizer for greens, lawns, or in bioremediation processes. In the present study, the microbial breakdown of these products was investigated. The nitrogen was released as ammonia and urea, and the formaldehyde released immediately oxidized via formiate to carbon dioxide. The enzymatic mechanism of metabolization of methyleneureas was studied in microorganisms isolated from soil, which were able to use these compounds as the sole source of nitrogen for growth. A strain of the Gram-negative bacterium Ralstonia paucula (formerly Alcaligenes sp. CDC group IVc-2) completely degraded methylenediurea and dimethylenetriurea to urea, ammonia, formaldehyde, and carbon dioxide. The enzyme initiating this degradation (methylenediurease) was purified and turned out to be different from the previously described enzyme from Ochrobactrum anthropi with regard to its regulation of expression and physicobiochemical properties. Fungal degradation of methyleneureas may occur via the formation of organic acids, thus leading to a nonenzymatic degradation of methyleneureas, which are unstable under acidic conditions.     

Effect of Degree of Substitution of Octenyl Succinate Starch on Enzymatic Degradation

Octenyl succinate starch of degree of substitution (ds) 0.03, 0.07, and 0.11 was synthesized in an aqueous medium. These compounds were then tested for the susceptibility to enzymatic degradation. The multiple-enzyme regime of -amylase, amyloglucosidase, and pullulanase was chosen for the evaluation. This combination of enzymes had been proven to degrade 99.5% of unmodified starch to glucose and hence was chosen for this study. It was found that even small amounts of subsituent caused a considerable decrease in the extent of degradation. The net extent of degradation decreased with increasing ds. Surprisingly, the amount of glucose from all three substituted substrates was quite similar, suggesting the effect small amounts of subtituent had on the enzymatic activity.     

Electron Microscope Observation of Biodegradation of Polymers

Biodegradable polymers generally decompose in the various media in our environments. These environments contain soils, seawater, and activated sludge. If biodegradable materials waste is discarded, they decompose in these media. The biodegradation process of biodegradable polymers was investigated by scanning electron microscopy. Polycaprolactone, polybutylene succinate, and P(3HB-co-3HV) were tested. The shapes of holes on the decomposing surfaces are different according to the biodegradation media. Semispherical holes are observed on the surfaces of polybutylene succinate films degraded in activated sludge and cracks are observed on the surfaces of polycaprolactone films degraded in soil.     

Structure-biodegradation relationships of polymeric materials. 1. Effect of degree of oxidation on biodegradability of carbohydrate polymers

The biodegradability of oxidized starch and inulin has been studied in relation to the degree of periodate oxidation to dialdehyde derivatives, by measuring oxygen consumption and mineralization to carbon dioxide. A higher degree of oxidation of dialdehyde starch and dialdchyde inulin results in a lower rate at which the polymers are biodegraded. It is demonstrated that the biodegradation rate of dialdehyde inulin derivatives decreases more than that of equivalent starch derivatives. The differences in biodegradation behavior between dialdehyde starch and dialdehyde inulin, resulting from comparable modifications, are discussed in terms of conformational structure.