过饱和铝酸钠溶液结构性质与分解机理研究现状*

过饱和铝酸钠溶液分解是氧化铝生产过机理的研究是氧化铝生产过程的重要基础问题.本文对过饱和铝酸钠溶液中铝酸根离子存在的基本形态,浓度、苛性比和阳离子对铝酸钠溶液结构性质的影响,溶液中多种铝酸根离子平衡与转化规律,以及铝酸钠溶液分解机理研究的现状进行了总结和评述;分析了现有铝酸钠溶液结构性质与分解机理研究的不足;围绕强化氧化铝生产中铝酸钠溶液分解过程的目的,提出了铝酸钠溶液结构性质与分解机理研究的重点.     

Reaction of xylan with aqueous solutions of alkali

Conclusions 1. The action of an aqueous solution of caustic soda on xylan leads to the formation of both a molecular and an alkoxide form of this polysaccharide. The composition and amount of the alkoxide formed depend on the conditions of treating the xylan with alkali.2. In the reaction of an aqueous solution of caustic soda with xylan, the hydrogen of the alcohol grouping on the second carbon atom exhibits the greatest reactivity.3. The result of IR spectroscopy confirm the existence of a chemical interaction of the xylan with caustic soda.4. According to X-ray analysis, the action of a solution of caustic soda on xylan leads to a decrease in intermolecular interaction, to a more ordered supermolecular structure, and to the appearance of crystallinity.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 4, pp. 206–210, 1969     

Isolation of gossypol from hexane-acetone miscellas

Summary 1. The influence of the nature of the alkali on the degree of extraction of gossypol from hexane — acetone miscellas by solutions of NH₄OH, borax, sodium carbonate, and caustic soda has been studied. It has been established that the maximum extraction of gossypol is achieved by using 2% caustic soda solution.2. It is proposed to treat the aqueous layer formed in the decomposition of the sodium gossypolate with sodium chloride, which enables the yield of gossypol to be raised to 90%.3. It has been shown that the concentration of the miscella in order to eliminate acetone does not lower the yield of gossypol on its isolation from caustic soda solution.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 177–180, March–April, 1978.     

Possibilities for Optimization of Industrial Alkaline Steeping of Wood-Based Cellulose Fibers

Steeping of cellulosic materials in aqueous solution of NaOH is a common pre-treatment in several industrial processes for production of cellulose-based products, including viscose fibers. This study investigated whether the span of commonly applied process settings has the potential for process optimization regarding purity, yield, and degree of transformation to alkali cellulose. A hardwood kraft dissolving pulp was extracted with 17–20 wt% aq. NaOH at 40−50 °C. The regenerated residue of the pulp was characterized regarding its chemical composition, molecular structure, and cellulose conformation. Yield was shown to be favored primarily by low temperature and secondly by high alkali concentration. Purity of xylan developed inversely. Both purity of xylan and yield varied over the applied span of settings to an extent which makes case-adapted process optimization meaningful. Decreasing the steeping temperature by 2 °C increased xylan content in the residue with 0.13%-units over the whole span of applied alkali concentrations, while yield increased by 0.15%-units when extracting with 17 wt% aq. NaOH, and by 0.20%-units when extracting with 20 wt%. Moreover, the yield-favoring conditions resulted in a narrower molecular weight distribution. The degree of transformation via alkali cellulose to cellulose II, as determined with Raman spectroscopy, was found to be high at all extraction settings applied.     

Structural Changes and Activation of Cellulose by Caustic Soda Solution with Urea

Investigations on the activation of cellulose by mixed solutions of caustic soda and urea are reported. The structural effects of those solutions on various dissolving pulps are studied by ¹³C-CP/MAS-NMR spectroscopy. In a series of steeping lyes, the concentration of NaOH was varied in a range from 0% to 8% and the urea-concentration in a range from 15% to 40% at ambient temperature and −25 °C. Using solely the single NaOH or urea solutions in the concentration ranges given above, no or only minor structural changes were found. In contrast to that, the cellulose I structure was partially or completely destroyed by using the bicomponent solution with urea added to caustic soda. The structural effect of the bicomponent solutions is comparable with the effect of solely caustic soda solutions of approx. 10% to 18% NaOH. However, the ¹³C-CP/MAS-NMR-spectra from the bicomponent pretreated samples indicate a structure different from the usual ordered structures of sodium cellulose I or II, namely a special urea-NaOH-cellulose complex. The results show that for cellulose activation the NaOH concentration of the caustic soda can be remarkably reduced by adding urea. The improved activating effect of an optimized caustic soda solution with added urea was proved to be useful for the synthesis of cellulose carbamate.     

用邻乙氧基苯酚电化学合成乙基香兰素的研究

乙基香兰素是目前畅销国际市场的一种合成香料 ,具有强烈的香子兰香气 ,其香味为同量香兰素的 3～ 4.5倍[1 ] ,不但可完全替代香兰素调味香精 ,还有独特风味。此外它还是重要的有机中间体 ,在药物合成方面得到广泛应用。市场需求不断增加。乙基香兰素的合成方法很多[2 ] ,工业上常用合成路线是由邻氨基苯乙醚经重氮化、水解、生成邻乙氧基苯酚。在对亚硝基苯胺和催化剂存在下 ,与甲醛缩合反应 ,生成乙基香兰素[3] ,该方法工艺复杂、收率低、污染大。我国采用上述生产工艺已有几十年历史 ,国外早已淘汰。随着环境问题的日益突出 ,新工艺的开…     

Zur Darstellung des Natriumbromits und bromitfreier Hypobromitlösungen

Sodium bromite may be prepared by dismutation of hypobromite solution produced by the addition of bromine to concentrated caustic soda at 0 °C, the hypobromite being destroyed after the maximum bromite concentration has been reached. Using bromine water or bromine vapour diluted by nitrogen at low temperatures, it is possible to prepare bromite-free hypobromite solutions.     

Extraction of Mercaptans from Light Hydrocarbon Mixtures with Aqueous Ammonia

Results of laboratory studies of the extraction of light mercaptans (methyl, ethyl, and propyl mercaptans) from hydrocarbons mixtures with a 25% aqueous solution of ammonia (caustic ammonia) are presented and discussed. It is shown that aqueous ammonia can in principle be used for controlled demercaptanization of light hydrocarbon fractions and liquefied hydrocarbon gases containing hydrogen sulfide and lower mercaptans. The advantage of this demercaptanization method over the conventional processes of alkali treatment is that there is no stage of oxidative catalytic regeneration of a spent alkali and there are no its highly toxic wastes, sulfurousalkaline waste waters. The regeneration of a spent (saturated with sulfurous compounds) aqueous ammonia can be comparatively easily performed by its heating (boiling), which leads to a hydrolytic decomposition of ammonium sulfides and mercaptides to release their constituent gases: hydrogen sulfide, mercaptans, and ammonia. Ammonia is recycled into the process as freshly prepared (regenerated) caustic ammonia.

     

Separation of microgram quantities of aluminum and iron(III)

The separation of microgram quantities of ferric iron and aluminum can be effected by passage of an acidic thiocyanate solution through the anion exchange resin Amberlite IRA-400A. The anionic complex of iron and thiocyanate remains on the column whereas aluminum passes through with the eluate. This method has been utilized in the separation of up to 200 μg of iron from comparable amounts of aluminum thus permitting the spectrophotometric determination of the latter in caustic liquors and other alkali products.     

Geopolymerization process of alkali–metakaolinite characterized by isothermal calorimetry

The geopolymerization process of metakaolinite activated by alkali and alkali silicate solutions was revealed. The effects of alkali concentration, modulus of alkali silicate solution and reaction temperature on geopolymerization were studied systematically by isothermal calorimetry, as well as X-ray diffraction and ²⁷Al/²⁹Si MAS NMR. Results show that the geopolymerization process of metakaolinite under alkali activation condition can be reasonably supposed into three stages: (I) destruction, (II) polymerization and (III) stabilization. The rate of geopolymerization in KOH solution is higher than in NaOH solution and reaches the maximum in 15 mol/L KOH solution during stage II. The extent of geopolymerization increases with increasing of alkali content regardless of the existence of silicate anions in activator.     

分子设计合成高折光指数的光学树脂(Ⅲ)MMDMA的合成及其共聚树脂的制备

采用盐酸/硫脲法合成了2-巯基甲基-1,4-二硫杂环己烷(MMD),利用反滴碱液的低温相转移催化技术合成了2-甲基丙烯酰硫基甲基-1,4-二硫杂环己烷(MMDMA),讨论了MMD合成过程中的结构变化,研究了MMDMA的共聚性能,合成了折光指数高、色散能力低的新型光学树脂.     

Crystallinity changes in lyocell and viscose-type fibres by caustic treatment

One of the most important treatments performed on cellulosic fibres to improve properties such as dimensional stability, tensile strength and lustre, is mercerisation. The aim of this work was to study the crystallinity, accessibility and unit cell structure changes occurring in three types of regenerated cellulose fibres (lyocell, modal and viscose) that were mercerised with caustic soda solutions of different concentrations. Differences were observed between the behaviour of the viscose type fibres (viscose and modal) and that of the lyocell fibres. For the viscose type fibres, the proportion of crystalline regions increased at low alkali concentrations, while for lyocell fibres a decrease in crystallinity was observed. In all three fibres there was a transformation from cellulose II to amorphous cellulose. While for lyocell the transformation was partial, the modal and in particular the viscose fibres showed a complete transformation, and the swelling agent caused the fibre to dissolve at high caustic concentrations.     

化学共沉淀法制备气敏材料Cd2+XSb2O6.8

采用化学共沉淀法,以可溶性的镉盐和三价锑盐为源物质、氢氧化物作共沉淀剂,在较宽的Cd/Sb摩尔配比范围内,制备出了具有缺陷烧绿石结构的镉锑复合氧化物Cd₂Sb₂O_6.8及其固溶体。研究了烧成条件对产物的影响,在较低温度(600℃)下得到了纯相Cd₂Sb₂O_6.8的超微粉,并对其高温反应机理进行了探讨。所得微粉产物制成的厚膜元件经气敏测试,发现n(Cd)/n(Sb)=1.10、 900 ℃、3 h烧成的间隙型固溶体Cd_2+XSb₂O_6.8,对乙炔气体具有非常优秀的气敏性能。     

Technology of magnesium hexafluorosilicate production

Systematic study of parameters of the techological process for producing crystalline magnesium hexafluorosilicate from hexafluorosilic acid and caustic magnesite: reagents concentrations and ratio, temperature of the synthesis and evaporation, order of pouring the reagents (caustic magnesite suspension and hexafluorosilic acid), intensity of the solution stiring at its crystallization. Optimal values providing maximal yield of the targeted product are elucidated.     

A STUDY ON THE ADSORPTION OF LOW CONCENTRATION FREE ALKALI BY SUBACID RESIN

1. INTRODUCTIONIn the purification process of food, drug, and biological products, usually the material to be purified were not neutral. Application of traditional neutralization method with acid or alkali could increase electrolyte content in the material to be purified. Due to the capability of the adsorption of free alkali by subacid resin, the defect of electrolyte absorption in neutralization could be avoided when used in the purification of food, drug, and biological products [1]. H…     

A STUDY ON THE ADSORPTION OF LOW CONCENTRATION FREE ALKALI BY SUBACID RESIN

The absorption of free alkali at low concentration by subacid resin was traced with electric conductance method,the effect of temperature on the adsorption,the activation energy of adsorption (Ea) and interaction energy(U) was studied.The result showed that,the process of low concentration alkali adsorption by subacid resin was in accordance with mechanism of monomolecular layer absorption,in addition,with the increasing of temperature,the interaction energy between adsorbate and sorbent increase,so did the surface adsorption rate(k),and linear correlation existed between interaction energy(U) and temperature(T).     

Distribution of Methoxyl Groups in the Methylation of Starch Alkoxides Obtained by Metallation with Alkali Metal Naphthalene

Abstract

The distribution of the alkoxide groups obtained in the metallation of starch in dimethyl sulfoxide solution by alkali metal naphthalenes was studied. The starch alkoxide was reacted with methyl iodide, and the methylated starch was hydrolyzed and analyzed for glucose and O-methyl glucose derivatives. The metallation reaction was found to be random, as seen from the fact that at low alkoxide concentration (D.S = 0.6), 2,3,6-tri-O-methyl glucose was formed, while at relatively high alkoxide concentration (D.S. = 1.5) unreacted glucose was still present. At low alkoxide concentration (D.S. ? 0.6) there was, to a certain extent, preferential metallation at the C₂ hydroxyl groups, and to a lesser extent at the C₆ hydroxyl groups, as seen from the relative molar ratios of about 10:4:1 of the 2-, 6-, and 3-O-methyl glucose derivatives obtained, respectively. An increase in the metallation at the C₃ hydroxyl occurred with increasing alkoxide concentration. The distribution of the methoxyl groups with the three alkali metals potassium, sodium, and lithium was similar; there were differences only in the ease of metallation of the starch by the various alkali metal naphthalenes and in the efficiency of the coupling reaction with methyl iodide.     

智能求解未知多元酸各级离解常数的研究

本文介绍了一种新的测定未知多元酸各级离解常数的通用方法。该方法实验上采用苛性碱电势滴定多元酸,计算上采用Gordon数学模型和单纯形最优化方法。并为此编制了一名为"GORDANACID"的计算机程序。     

Biosorption of Heavy Metal Ions to A Marine Microalga, Heterosigma akashiwo (Hada) Hada

Alkaline flooding is a method of enhanced oil recovery that relies on the formation of surface-active substances in situ by a chemical reaction between acidic components in the oil and an alkaline reagent. As the injected alkali advances through the porous medium, it keeps contacting fresh oil. At some moment dependent on the alkali/acid concentrations and the velocity, the alkali at the advancing front may become depleted and the flood becomes interfacially nonreactive. The present study is aimed at investigating the above-mentioned phenomena. Displacement studies were conducted in radial cells containing sintered glass beads as a porous medium. Light paraffin oil acidified with 10 mmol/L of linoleic acid served as the displaced (oil) phase while the displacing aqueous solution contained 0-25 mmol/L of sodium hydroxide. The highest oil recovery was obtained under the conditions of low flow rate and high alkali concentration. Increasing the flow rate at high NaOH concentration resulted in decreasing oil recovery up to a certain threshold flow rate. Conversely, the amount of oil recovered by waterflooding only (no alkali) initially increased with increasing flow rate up to the same threshold flow rate beyond which there was no difference between the alkaline flood and a waterflood. Copyright 2000 Academic Press.     

碱木质素在超临界水中Ru/C纳米管催化气化的降解研究

针对碱木质素难降解的特点,在间歇式反应器中,以Ru/C纳米管为催化剂,对碱木质素在超临界水中的气化进行研究。分别探讨了碱木质素在不同温度、水密度、反应时间、反应浓度、催化剂量的影响,并且分析了Ru/C纳米管催化剂的催化效率。通过单因素实验分析,确定了Ru/C纳米管催化剂催化气化碱木质素的最佳反应条件为,反应温度600 ℃、水密度0.128 4 g/cm³、反应时间60 min、反应质量分数3.0%、催化剂量0.5 g/g(碱木质素)。结果表明,碱木质素在超临界水气化过程中,高温、高水密度(或压力)、长反应时间、低反应物浓度及适量的催化剂将更有利于碱木质素的气化。在最佳反应条件下碱木质素的气化率和碳气化率分别达到73.74%和56.34%,且制氢能力也得到明显提高。