Splitting tendency of cellulosic fibers. Part 2: Effects of fiber swelling in alkali solutions

The splitting tendency of lyocell fiber in aqueous alkali solutions like KOH, NaOH, LiOH and TMAH was investigated. Up to 5 M concentration of alkali solutions, cation type is important on splitting of lyocell. Above 5 M concentration, cation type is no more relevant to splitting of lyocell. At 1 M of alkali solutions, alkali retention value (ARV) and split number increase in the order of KOH<LiOH<NaOH<TMAH. It was proposed that lyocell is swollen homogeneously inside fiber above 5 M alkali concentration, so that when force is applied on fiber, no split occurs in lyocell fiber since there isn’t enough internal stress inside of the fiber. Different concentrations of each type of alkali result in the same ARV for the fiber, but their alkali distribution inside fiber is the decisive point for splitting of lyocell fiber, so that for each alkali type different split numbers are observed. Depending on alkali concentration and alkali type, maximum splitting of a fiber into 15–20 fibrils could be observed.     

碱对聚丙烯酰胺的分子形态及其流变性的影响

在碱、活性剂、聚合物三元(ASP)复合驱提高石油采收率的技术中,由于碱与聚合物分子的不相容性,严重地影响着驱油配方体系的研究及复合驱技术的推广.针对大庆油田的情况,利用HAAK流变仪,系统地研究了复合体系的流变性.结果表明,碱的加入明显地破坏了ASP复合体系的粘弹性.利用原子力显微镜,研究了碱对聚合物分子形态的影响.在无碱条件下,聚合物分子在液相充分舒展,而加入碱造成聚合物分子蜷缩,碱浓度越高,聚丙烯酰胺分子蜷缩成的线团越紧凑.在低浓度碱溶液中（质量分数0.3％）,聚合物分子也不能完全舒展,而是以多个分子侧向聚集状态存在.     

ZSM-5分子筛的脱硅改性及加氢改质性能

考察了水热与碱联合处理过程中两者的先后顺序对ZSM-5分子筛酸性和孔结构的影响,并与单独的水热和碱处理进行了比较。结果表明,水热后的碱处理对ZSM-5分子筛具有骨架脱硅、骨架补铝和清除非骨架铝物种三重作用,而碱处理后的水热处理具有骨架脱铝和部分骨架稳定化双重作用。与先水热处理再碱处理相比,先碱处理后的水热处理在优化分子筛酸性和产生介孔方面更加有效。基于水热-碱联合处理的HZSM-5分子筛所制备的催化剂对催化裂化汽油的加氢改质表现出适中的异构化活性、较高的烯烃芳构化活性以及最高的稳定性。     

Solvothermal Synthesis and Crystal Structures of Alkali Molybdates

Within the frame of systematic morphological studies concerning the solvothermal formation of nanoscale and microscale molybdenum oxides from the interaction of a molybdenum‐based precursor such as MoO₃⋅2 H₂O with ionic additives such as alkali and earth alkali halides, we studied – with the aim to elaborate preparative guidelines – the influence of the precursor structure and the alkali halide upon the crystal structure of the emerging alkali polymolybdates in terms of solvothermal fields and high‐throughput solvothermal techniques. The discussion of the resulting crystal structures revealed a structure‐directing potential of the alkali cations that was explored for the synthesis of new mixed alkali polymolybdates.     

Studies of synergism/antagonism for lowering dynamic interfacial tension in surfactant/alkali/acidic oil systems. 3. Synergism/antagonism in surfactant/alkali/acidic model oil systems

Experimental studies have been conducted to elucidate the mechanisms responsible for synergism/antagonism for lowering dynamic interfacial tension (IFT) in surfactant/alkali/hydrocarbon and surfactant/alkali/acidic model oil systems. Dynamic IFTs between hydrocarbon/acidic model oil and alkali/surfactant solutions were measured. We learned from our experimental results that alkali has the function of decreasing n(min) values of surfactant solutions. The synergism/antagonism for lowering the stable values of dynamic IFTs in surfactant/alkali/hydrocarbon and surfactant/alkali/acidic model oil systems depends on factors that can change the EACN/n(min) value, such as the oleic acid in the oil phase and the n(min) values of surfactant and alkali. A new explanation with respect to EACN/n(min) values is provided.     

三元复合驱碱/表面活性剂/聚合物模拟原油乳状液稳定动力学特性

基于两相分离的乳状液稳定模型,研究了三元复合驱模拟原油乳状液稳定动力学特性;通过液膜强度和油水界面张力探讨了碱/表面活性剂/聚合物对模拟原油乳状液稳定动力学特性的影响机理。 结果表明,乳状液稳定模型可以很好的评价乳状液的稳定性,并得到乳状液的稳定动力学特性;碱浓度小于900 mg/L有利于乳状液的稳定,碱浓度大于900 mg/L不利于乳状液的稳定;表面活性剂和聚合物浓度的增加使得形成的模拟原油乳状液更加稳定;模拟原油乳状液的稳定作用主要是通过碱、表面活性剂降低油水界面张力并增加油水界面膜强度,聚合物通过提高界面膜强度实现的,三者存在协同效应。     

燃煤过程中碱金属迁移规律的模拟研究与预测分析

基于ASPEN PLUS 平台,对燃煤过程中碱金属迁移规律进行了模拟研究和预测。模拟结果表明,在850K~1650K气态碱金属物质随反应温度的升高而增加;1400K以下,气相中以NaCl、KCl为主,Na2SO4蒸气量明显高于K2SO4;1500K以下,气态碱金属释放量随着煤中氯质量分数的增加而增加;一定温度下,气态碱金属质量分数随压力的升高而降低;常压下煤中氯的质量分数0.1%,温度降到972K时气态碱金属的质量分数可降到2.4×10－8;而当氯的质量分数分别为0.05%和0.01%时,为达到同样的气态碱金属质量分数,温度需分别降到990K和1025K。模拟结果为燃煤联合循环发电系统的设计和优化提供了参考依据。     

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.     

Quaternized lignin-based dye dispersant: Characterization and performance research

Lignin-based dye dispersants have aroused an increasing interest due to their environment-friendly properties. In this research, the quaternized lignin-based dye dispersant (QLD) was prepared using alkali lignin from masson pine sulfate pulping liquor as raw materials by chemical modification, that is, sulfonation and quaternization. The structure and performance characterization of alkali lignin and QLD were studied. The analyses indicated that the structural unit of alkali lignin contained more G type and S type. Additionally, it was also proved that QLD contained quaternary ammonium group, amine group, and sulfonic group, which could improve the dispersion performance and thermostability of QLD. The results of thermogravimetric (TG) concluded that the dispersion performance and thermostability of QLD prevailed over alkali lignin. Compared with the contact angle of water, alkali lignin, and QLD with dye, the contact angle of QLD was much better than water and alkali lignin, indicating that the hydrophilicity and dispersion performance of QLD were superior to water and alkali lignin in Vat Olive T.     

Why alkali metals preferably bind on structural defects of carbon nanotubes: a theoretical study by first principles

By using ab initio calculations we investigated the interaction of alkali metal atoms and alkali metal cations with perfect and defective carbon nanotubes. Our results show that the alkali metals prefer to interact with the pentagons and heptagons that appear on the defective site of the carbon nanotube rather than with the hexagons. The alkali metals remain always positively charged not depending on their charge state (neutral, cation) or the different carbon ring that they interact with. The molecular orbital energy level splitting from a defect creation on the carbon nanotube along with the localization of charge-electron density on the defect, results in binding the alkali metals more efficient. More interestingly, metallic sodium appears to bind very weak on the nanotube compared to the rest of alkali metals. The Na anomaly is attributed to the fact that unlike the K case, sodium's inner p shell falls energetically lower than carbon nanotube's p molecular orbitals. As a result, the Na p shell is practically excluded from any binding energy contribution. In the alkali metal cation case the electronegativity trend is followed.     

Humidity sensor using zirconium phosphates and silicates. Improvements of humidity sensitivity

Humidity-impedance characteristics were examined for amorphous and crystalline zirconium phosphate, their alkali salts as well as zircon samples calcined in the presence of phosphoric acid or monobasic alkali phosphates. The humidity-impedance characteristic was shown to be improved when the acidic protons of the sample were replaced with alkali cations. For calcined zircon, the impedance in a humid atmosphere was lowered when the sample was calcined with monobasic alkali phosphate as compared with the sample calcined with phosphoric acid, while the surface area hardly depended on the additives. In the case of amorphous zirconium phosphate-bases samples, replacing the acidic protons with alkali cations such as Na and K made the impedance lower and less dependent on the calcination temperature, while it decreased the surface area and the response time. Similar effects of alkali cations on impedance were also observed with crystalline zirconium phosphate.     

Two-photon photoemission study of the coverage-dependent electronic structure of chemisorbed alkali atoms on a Ag(111) surface

We report a systematic investigation of the electronic structure of chemisorbed alkali atoms (Li-Cs) on a Ag(111) surface by two-photon photoemission spectroscopy. Angle-resolved two-photon photoemission spectra are obtained for 0-0.1 monolayer coverage of alkali atoms. The interfacial electronic structure as a function of periodic properties and the coverage of alkali atoms is observed and interpreted assuming ionic adsorbate/substrate interaction. The energy of the alkali atom σ-resonance at the limit of zero coverage is primarily determined by the image charge interaction, whereas at finite alkali atom coverages, it follows the formation of a dipolar surface field. The coverage- and angle-dependent two-photon photoemission spectra provide information on the photoinduced charge-transfer excitation of adsorbates on metal surfaces. This work complements the previous work on alkali/Cu(111) chemisorption [Phys. Rev. B 2008, 78, 085419].     

准东煤中碱金属的赋存形式及其在燃烧过程中的迁移规律实验研究

对新疆煤采用三步化学提取实验(蒸馏水洗、醋酸铵洗、稀盐酸洗)以分析其碱金属赋存特性,对水溶的阴离子进行了离子色谱分析。分别检测了在不同温度、不同停留时间下准东煤灰的碱金属量,并用Factsage软件模拟该煤灰中碱金属的析出形式。结果表明,煤中的钠主要是水溶钠,钾主要以不可溶钾存在,水溶碱金属主要以水合离子形式的氯化物存在。准东煤中碱金属在400~600℃析出最快,主要是水溶态碱金属的释放,碱金属的释放主要发生在燃烧后期。灰中碱金属在高温下会与烟气中的成分发生反应,主要产物是氯化物以及氢氧化物。在700℃钠对准东煤中低温共融物的形成有很大贡献。     

New observations on the solubility of prussian blue

1. Alkali metaphosphates and alkali polyphosphates dissolve Prussian blue to potassium ferrocyanide and to the corresponding ferric alkali metaphosphates and polyphosphates. But smaller quantities peptize Prussian blue. The alkali metaphosphates and alkali polyphosphates are the first inorganic substances whose peptizing action on Prussian blue was observed. 2. The alkali salicylates and alkali β-resorcylates react in an analogous way with Prussian blue. They dissolve Prussian blue if sufficient quantities are present. But smaller quantities yield colloidal Prussian blue. 3. The statement in the literature that Turnbull's blue is not peptized by potassium oxalate is erroneous. Simultaneously, the conclusion had to be drawn that Turnbull's blue is an equimolecular mixture of Prussian blue and ferrous ferrocyanide. 4. Data given in the literature describing some reactions leading to colloidal Prussian blue and stating that Prussian blue does not react with hydrobromic acid are erroneous.     

Novel evidence on the chemistry of β-Lactone anionic polymerization

The mechanistic aspects of the β-lactones anionic polymerization initiated by both classical initiators, i.e. alkali metal alkoxides, and non-traditional ones, such as supramolecular complexes of alkali metals and alkali metal naphthalenes, are discussed in this paper.     

Mechanisms of the action of alkali metal admixtures on the properties of copper–zinc–aluminum water–gas shift catalysts

The effect of alkali metal (Cs, Na) admixtures on the catalytic and physicochemical properties of coprecipitated Cu–Zn–Al catalysts for the low-temperature water–gas shift reaction has been investigated. The inhibition of the formation of methanol, an undesired by-product, by alkali metals is accompanied by a decrease in the activity of the catalyst in the main, water–gas shift reaction ion. The alkali metals exert an adverse effect on the thermal stability of the catalyst. Experimental data are explained in a consistent way on the basis of the following conceptions of the mechanism of the action of alkali metals: (1) the alkali metals stimulate sintering of the crystal structure of the main components of the catalyst, diminishing the activity of the catalyst in the water–gas shift reaction and in methanol formation; (2) the alkali metals directly or indirectly accelerate methanol conversion into other chemical products.     

Binding mechanisms of nano-baskets toward alkali metals

Thirty-four nano-basket derivatives of di-ionizable calix[4]arene conformers in nine scaffolds bearing two pendant groups of N-(R)-sulfonyl carboxamides were synthesized and examined using isothermal titration calorimetry. The binding mechanisms of synthesized conformers toward alkali metal cations were evaluated and two main interactions were assessed including cation?C?? interaction between alkali metal and the aromatic unit of conformer as well as the strong binding ion?Cdipole interaction between nitrogen atoms in the pendant groups and alkali cation. The ITC data revealed that the bindings of cone and partial-cone conformers toward alkali metal cations exhibited one-step mechanism, while both 1,2 alternate conformer bounds the alkali metal cations in a two-step mechanism.     

Experimental Study of the Effect of Strong Alkali on Lowering the Interfacial Tension of Oil/Heavy Alkylbenzene Sulfonates System

Experimental studies were conducted to explore the fundamental mechanisms of alkali to lower the interfacial tension of oil/heavy alkylbenzene sulfonates (HABS) system. Sodium hydroxide was used as the strong alkali chemical to investigate the interfacial tension (IFT) of oil/HABS system. The influences of salt and alkali on the interfacial activity were studied by the measurement of interfacial tension and partition coefficient. Moreover, the alkali/surfactant solutions were measured by dynamic laser scattering. The results showed that compared with the salt, the function of alkali to lower the interfacial tension and improve partition coefficient is more significant. The micelles formed by surfactants could be disaggregated because of adding alkali, so the size of micelles decreases and the number of mono‐surfactants increases, then more surfactant molecules move to the interface of oil/surfactant system and the adsorption of surfactants at oil‐water interfaces increases, which can lead to the decrease of IFT.     

Neutron Total Scattering Investigation of the Dissolution Mechanism of Trehalose in Alkali/Urea Aqueous Solution

The atomic picture of cellulose dissolution in alkali/urea aqueous solution is still not clear. To reveal it, we use trehalose as the model molecule and total scattering as the main tool. Three kinds of alkali solution, i.e., LiOH, NaOH and KOH are compared. The most probable all-atom structures of the solution are thus obtained. The hydration shell of trehalose has a layered structure. The smaller alkali ions can penetrate into the glucose rings around oxygen atoms to form the first hydration layer. The larger urea molecules interact with hydroxide groups to form complexations. Then, the electronegative complexation can form the second hydration layer around alkali ions via electrostatic interaction. Therefore, the solubility of alkali aqueous solution for cellulose decreases with the alkali cation radius, i.e., LiOH > NaOH > KOH. Our findings are helpful for designing better green solvents for cellulose.     

Grass fiber reinforced phenol formaldehyde resin composite: preparation,characterization and evaluation of properties of composite

There is a growing interest in the development of new materials through utilization of natural resources. This paper describes evaluation of water leached and alkali treated chopped grass fiber reinforced phenol formaldehyde composite. Here alkali treatment of grass fiber was carried out by varying the concentration of sodium hydroxide. The thermal stability of the composite was assessed by thermogravimetric analysis (TGA). Fourier transformation infrared spectroscopic study of both water leached and alkali treated grass fiber‐phenolic resin composite was also performed. Water absorption and swelling behavior of grass fiber phenolic resin composites in water were studied and the alkali treated grass fiber‐resin composite showed less water absorption and swelling. A composite prepared from 1% alkali treated grass fiber and 55% resin, showed the highest tensile strength whereas a composite prepared from 5% alkali treated grass fiber and 55% resin, showed maximum flexural properties. Copyright © 2006 John Wiley & Sons, Ltd.