Decomposition of sec-butyl acetate on charcoal

The decomposition of sec-butyl acetate on de-ashed 20-to 30-mesh coconut-shell charcoal (1500 m²/g) was studied in a fixed bed reactor in the temperature range 300–375°C, and at partial pressures of 1 atm. and 0.29 atm. The ester decomposed principally to n-butene and acetic acid, and only small amounts of other products were found. The ratio of 1-butene to 2-butene was about 1:1, very close to that observed for thermal decomposition of the ester but far removed from the equilibrium butene ratio. The butene selectivity was independent of conversion. The rate of reaction followed the rate equation r = kA P_E/1 + AP_E This expression corresponds to surface reaction on one site being rate controlling. The activation energy of rate constant k was 32.7 kcal/mole, compared to 46.6 kcal/mole for the gas-phase reaction. The temperature dependence of adsorption constant A showed a heat adsorption of 12 kcal/mole. Gas chromatographic measurements confirmed this value and also showed that ester is the principal adsor-bate on the charcoal.     

Decomposition of t-butyl acetate on charcoal and comparison with isomers on charcoal and in the gas phase

The decomposition of t-butyl acetate on charcoal to isobutene and acetic acid is a clean, zero-ordet reaction at temperatures of 151° to 288°C with an apparent activation energy of 90.8 kJ/mol. The rates for the 4 butyl acetates on charcoal and in the gas phase are compared. The rates on charcoal are always larger than those in the gas phase. The primary reaction products from the decomposition on charcoal and in the gas phase are acetic acid and the butene indicated by the six-center-ring mechanism.     

甲基异丁基酮生产与市场浅析

甲基异丁基酮简称ＭＩＢＫ,是一种优良的中沸点溶剂和化工中间体,可用作油漆、硝化纤维、乙基纤维素、录音录像带、石蜡及多种天然或合成树脂溶剂,润滑油精制的脱蜡剂,稀土金属钽、铌及其盐的萃取剂,橡胶防老剂的原料和农药萃取剂等。１　生产方法ＭＩＢＫ合成方法很多,其中工业化的合成方法主要有异丙醇法、丙酮三步法和丙酮一步法等。１１　异丙醇法异丙醇和丙酮在Ｃｕｏ／Ａｌ２Ｏ３或ＣｕＯ／ＳｉＯ２Ａｌ２Ｏ３上常压脱氢,脱水缩合制备ＭＩＢＫ,主副产物为二异丁基酮,此法生产国外报道较少,国内在这方面的研究较多,如锦…     

纳米铁氧体/石墨烯复合材料的制备研究进展

石墨烯/铁氧体复合材料由于复合单体石墨烯与铁氧体两者特殊的结构和性质引起了国内外研究者的极大兴趣。石墨烯结构特殊,性能优异却由于其本身存在的层间易团聚现象导致了有效比表面积减小,比电容等性能下降,铁氧体具有高的比容量却电导率低,为了有效地克服二者的不足并充分利用其优势,近年来研究者们不断研究两者的复合制备方法。介绍了复合材料的制备方法的最新研究进展,并对其应用前景进行了展望。     

溴代乙酸酯类化合物的合成进展

溴代乙酸酯作为一类重要的精细化工原料和中间体，其合成与应用已得到国内外的广泛关注。本文主要介绍了一些常见溴代乙酸酯的合成方法，并对这些方法进行了简要评述。     

磷酸二氢钠催化合成乙酸异丁酯的研究

研究了以磷酸二氢钠为催化剂,冰乙酸和异丁醇为原料合成乙酸异丁酯,确定了酯化反应最佳条件。结果表明,冰乙酸用量为0．17mol,异丁醇用量为0．10mol,催化剂用量为2．5g,反应时间为2．0h时,乙酸酯化率达93．17％。     

甲醇存在时异丁硫醇在HZSM-5分子筛上的转化反应研究

在固定床微型反应器中,以异丁硫醇为研究对象,通过其在不同反应条件和稀土改性 HZSM-5分子筛中的一系列反应,探讨其催化转化反应及规律。在HZSM-5及改性催化剂催化条件下, 异丁硫醇在较低温度250℃下就可以有较高的转化率(70％),当温度达到350℃时,异丁硫醇完全转化,生成产物主要为硫化氢;稀土镧负载量对其转化率有较大影响,w(La2O3)=1．0％时有较好的效果; 甲醇的加入对异丁硫醇的转化率有一定提高,甲醇与苯的体积比为0．2时对异丁硫醇转化较为有利,但其液相反应产物趋于复杂,选择性有所降低。     

氯乙烯-乙烯基异丁基醚树脂在涂料中的应用

阐述氯乙烯-乙烯基异丁基醚树脂的制备方法、树脂表征和性能及其应用范围。     

Carbon-sulphur surface complexes on charcoal

Interaction of charcoal with sulphur, hydrogen sulphide, carbon disulphide and sulphur dioxide at 600°C results in appreciable fixation of sulphur. The amount fixed varies with the nature of the reagent used and, for a given reagent, it depends not so much on surface area as on oxygen and hydrogen contents, extent of surface unsaturation and pore structure of charcoal. There are indications that sulphur is fixed partly by addition at the unsaturated sites and partly by substitution through interaction with certain oxygen groups which come off as carbon monoxide on high temperature evacuation. The carbon-sulphur complex, resulting from fixation of sulphur on charcoal, is highly stable. The products, when heated in a current of nitrogen, evolve largely hydrogen sulphide and carbon disulphide but the entire amount cannot be recovered even at 1200°C. The amount of sulphur recovered as sulphate ion on prolonged treatment with excess of hot concentrated nitric acid varies with the nature of the reagent used in the fixation of sulphur. The results give some indication of the possible nature of sulphur-containing groups and structures formed. The products catalyse sodium azide-iodine reaction to varying extents. The adsorption isotherms of water, methanol and benzene indicate considerable narrowing down of capillary pores of charcoal, as a result of fixation of sulphur.     

Kinetics of zinc adsorption on charcoal

The kinetics of zinc adsorption on charcoal was carried out. In order to study the kinetics of adsorption various parameters were studied such as pH, particle size of charcoal, temperature, amount of charcoal as well as initial Zn²⁺ ion concentration. The adsorption kinetics followed a Freundlich adsorption isotherm. Good correlation of the theoretical and experimental equilibrium concentrations of Zn²⁺ ions was observed for the isotherm model. A mathematical model was developed to explain the kinetic data. The rate determining step for adsorption was found to be diffusion controlled.     

二氧化碳活化法制备竹材基药用炭的研究

以竹炭为原料,二氧化碳为活化剂制备药用炭。系统研究了活化温度、活化时间、二氧化碳流量以及原料粒度对药用炭吸着力及得率的影响,并对过程反应机理进行了初步探索。得到了优化工艺条件,当活化温度950℃,活化时间120min,二氧化碳流量600mL／min,原料粒度3．35～4．75mm,所得药用炭的吸着力达到1．28,得率54．30％,其吸着力超过《中国药典（2005年版）》的要求。实验结果表明,采用竹炭可以制备高性能的药用炭。     

The Influence of n-3 PUFA Supplements and n-3 PUFA Enriched Foods on the n-3 LC PUFA Intake of Flemish Women

Food consumption data of Flemish women of reproductive age collected in 2002 showed a large deficit for ALA and n-3 LC PUFA compared to the recommendations (mean ALA and EPA + DHA intake 1.4 g/day and 209 mg/day, respectively) and indicated a need to tackle the problem of low n-3 PUFA intake. Another recent Belgian study demonstrated that enrichment of commonly eaten food items with n-3 PUFA provides the opportunity to increase the n-3 PUFA intake up to 6.5 g/day and decrease the n-6/n-3 ratio. Since a large supply of n-3 PUFA supplements and n-3 PUFA enriched foods exists on the Belgian market, this study aimed at assessing the influence of these products on the n-3 LC PUFA intake for Flemish women of reproductive age. It was found that n-3 supplements are consumed by 5% of the Flemish women. Of all the n-3 PUFA enriched foods on the Flemish market, margarines and cooking fat are most frequently consumed by young women. The results indicated that a big gap remains between the EPA&DHA intake (mean = 276 mg/day) and the recommendation. Seafood remains the most important source of EPA&DHA. Only 11.6% of the population sample reached an intake level of 500 mg EPA&DHA per day. The study showed that other strategies will be needed to increase the EPA&DHA intake in the long term.     

Anti-icing agents based on magnesium and sodium acetates and chlorides

Phase equilibria in sections of the Mg(CH₃COO)₂-NaCl-H₂O system at 0 to ?30°C have been investigated, and, based on the data obtained, new anti-icing agents (solid and liquid ones) are suggested. The ice melting capacity of these agents under equilibrium conditions has been determined. The liquid agent causes no damage to Portland cement concrete pavements. The corrosivity of this agent toward carbon steel St3 has been determined. The agent can be made considerably less corrosive by introducing a corrosion inhibitor. The agents can be prepared using mineral raw materials, namely, bischofite (MgCl₂ · 6H₂O) and halite (NaCl).     

Geometrical and positional isomerization of alkenyl acetates produced by hydrogenation of alkynyl acetates over palladium metal catalysts

Alkenyl acetates containing both geometrical isomers can be produced by a single controlled catalytic hydrogenation of the corresponding alkynyl acetate. The hydrogenation is capable of yielding formulations containing up to 60% trans isomer; the reduction is attended by positional isomerization in both geometrical isomers.NRCC No. 16834.     

Surface properties and biocompatibility of cellulose acetates

The article describes some properties of cellulose acetates (CAs) with different substitution degrees. The hydrophilic/hydrophobic properties, morphological aspects, and interface properties with red blood cells and platelets are affected by the substitution degree, synthesis conditions, history of the formed films from solutions in acetone/water nonsolvent/nonsolvent mixtures, and low pressure plasma treatment. The results obtained are useful in biomedical applications, including evaluation of bacterial adhesion onto surfaces, or utilization of CA for semipermeable membranes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A cation exchange resin based on the condensation product of poly(iso-butyl vinyl ether) and furfural

A cation exchange resin was synthesized from the condensation product of poly(iso-butyl vinyl ether) and furfural by treating it with concentration sulphuric acid. The resin produced was characterized by measuring its total and salt splitting capacities, and by studying its thermal characteristics and behaviour to pH metric titration. The latter suggests the resin to be a weak one possibly containing ? COOH groups, which result from the oxidation of the furfural aldehyde group by sulphuric acid.     

活性炭脱附方法的探讨

对活性炭的几种脱附方法进行了阐述,分析了不同吸附质的脱附方式,结合脱附活化能的知识建立了模型,并对脱附技术提出了节能、环保的发展要求.     

Nickel-catalysed electrochemical carboxylation of allylic acetates and carbonates

The electrochemical carboxylation of a series of allylic acetates and carbonates was carried out in the presence of CO₂ under atmospheric pressure, with a catalytic amount of nickel-bipyridine complex, to afford the corresponding β,γ-unsaturated carboxylic acids. In the absence of nickel catalyst, alcohols were obtained.     

Contrasting Effects of n-3 and n-6 Fatty Acids on Cyclooxygenase-2 in Model Systems for Arthritis

Cyclooxygenase-2 (COX-2) is intimately involved in symptoms of arthritis while dietary n-3 polyunsaturated fatty acids (PUFA) are thought to be beneficial. In these experiments, using both bovine and human in vitro systems that mimic features of arthritis, we show that the n-3 PUFA eicosapentaenoic acid (EPA) is able to reduce mRNA and protein levels of COX-2. Activity, as assessed through prostaglandin E₂ formation, was also reduced in a dose-dependent manner. These effects of EPA contrasted noticeably with the n-6 PUFA, arachidonic acid. The data provide direct evidence for a molecular mechanism by which dietary n-3 PUFA, such as EPA, can reduce inflammation and, hence, associated symptoms in arthritis.     

The influence of n-6 and n-3 fatty acids on kidney phospholipid composition and on eicosanoid production in aging rats

Changes in eicosanoid production may contribute to some of the complications of the aging process such as atherosclerosis and glomerular sclerosis. Polyunsaturated fatty acids of the n-6 and n-3 series are precursors of eicosanoids. We fed diets containing safflower oil as a source of n-6 fatty acids, fish oil as a source of n-3 fatty acids or beef tallow as a source of saturated fats to three groups of normal rats from 2–18 months of age. We demonstrated incorporation of the n-3 fatty acids, 20:5n-3 and 22:6n-3 into kidney phospholipids. Feeding of the diet containing n-3 fatty acids was associated with a markedly decreased giomerular production of PGE, 6-keto-PGF_1α and TXB₂. It also decreased the aortic production of 6-keto-PGF_1α and platelet production of TXB₂. No significant effect of n-6 fatty acids on dienoic eicosanoid production was observed. There were no adverse effects on kidney function as measured by urinary protein excretion and serum creatinine levels or on renal morphology by any diet. A diet enriched in n-3 fatty acids for 18 months remains effective in decreasing dienoic eicosanoids in the aging rat.