Adsorption characteristics of water-reducing agents on gypsum surface and its effect on the rheology of gypsum plaster

In this study, by using UV-visible adsorption spectrophotometer, Zeta potential analyzer and X-ray photo spectroscopy, the adsorption characteristics and surface electrochemical properties of two types of superplasticizer-β-naphthalene sulfonic acid type (BNS) and polycarboxylate type (PC) and their effects on the fluidity of gypsum plaster were studied. The results show that the adsorption of BNS and PC on gypsum surface approximately conforms to Langmuir's adsorption isotherm. The adsorption of BNS belongs to physical adsorption, its adsorption heat being 14.71 kJ/mol and the thickness of adsorption layer 120 Å; while the adsorption of PC belongs to chemical adsorption, with an adsorption heat of 20.85 kJ/mol and a thickness of adsorption layer of 120 Å. The adsorption conformation of BNS is lying on the flat of gypsum surface, generating weak steric hindrance to inhibit agglomerate of gypsum particles. Its dispersion effect mainly depends on electrostatic repulsive force caused by ζ-potential, which is determined by the adsorbed amount of BNS at the first adsorption layer on gypsum surface. The adsorption conformation of PC is comb-shaped, generating strong steric hindrance by side chains of adsorption layer, thus, its dispersion ability mainly comes from a combination effect of steric hindrance and electrostatic repulsive force. The dispersion by steric hindrance is less affected by the rapid hydration of gypsum, thus, its stability is much better than that of electrostatic repulsive force, resulting in little flow loss of fresh gypsum plaster.     

新型杂环Schiff碱的合成、晶体结构及荧光性质研究

以3-甲基-2-噻吩甲醛和4-氨基安替比林为原料合成了一种新的schiff碱--1,5-二甲基-4-[(3-甲基噻吩-2-亚甲基)氨基]-2-苯基-1,2-二氢吡唑-3-酮,采用IR、元素分析法、NMR及X-射线单晶衍射法对其结构进行了表征.该化合物属于正交晶系,P212121空间群,晶胞参数a=0.697 81(6)...     

Studies on the surface properties and the adhesion to metal of polyethylene coatings modified with primary aromatic amines

The surface free energy and acid–base characteristics of polyethylene coatings formed on steel in the presence of primary aromatic amines (PAAs) were investigated. PAAs were shown to interact with steel by a donor–acceptor mechanism. An increase in the coating adhesion is realized through chemical and physical bond formation between an adhesive and a substrate with the help of the PAA. The free surface energy of the contact‐to‐metal side of these coatings modified with PAA was shown to grow in parallel with the increase in adhesion. The results correlate with the data on polyethylene surface wetting with nonionic surfactants. Acid–base interactions were found to exert primary control over polyethylene's adhesion to steel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 388–397, 2001     

稀土镧氨基酸Schiff碱的合成及热分解动力学研究

合成了配合物[La(Glu-sal)(H2O)2Cl].2H2O,并通过化学分析、红外光谱、紫外光谱、摩尔电导和TG-DTA等对其进行了表征,运用Achar法和Coats-Redfern法,研究了配合物第3步、第4步热分解的动力学过程,第3步非等温动力学方程为dα/dt=Ae-E/RT3/2(1-α)2/3[1-(1-α)1/3]-1,其表观活化能E=216.4 kJ/mol,指前因子lnA=45.2 s-1;而第4步动力学方程为dα/dt=Ae-E/RT(1-α)2,其表观活化能E=289.8 kJ/mol,指前因子lnA=50.9 s-1。     

重质芳烃油选择性加氢工艺研究

以油浆抽提得到的重质芳烃油为原料,通过选择性加氢工艺降低其中有害的稠环芳烃(PAHs)化合物,得到的精制油为橡胶用环保芳烃油。实验分别对反应温度、压力、时间以及一段、二段加氢工艺对PAHs转化率的影响进行了考察,同时运用BET及EDS对2种硫化态催化剂进行了表征,以考察催化剂的活性及选择性。结果表明,Ni-W/γ-Al2O3催化剂活性及选择性较Ni-Mo/γ-Al2O3高。实验证明:通过选择性加氢可大幅度降低重质芳烃油中PAHs质量分数,一段加氢采用Ni-W/γ-Al2O3催化剂,在反应温度280℃、压力8 MPa、时间6 h的条件下,原料PAHs转化率达到46.24%;二段加氢采用Ni-Mo/γ-Al2O3催化剂,在与一段相同的反应条件下,PAHs转化率达到32.94%。经2段加氢后,产物中PAHs质量分数由起始的58.13%降到21.05%,总转化率达到63.79%,液体总收率91.72%。     

高纯四氢芳樟醇的研究

在一定条件下,芳樟醇可高选择性地氢化成四氢芳樟醇,氢化选择性与催化剂的特性、氢化温度及芳樟醇来源有关。在适宜的氢压及搅拌条件下,改变催化剂的特性、反应温度及使用不同来源的芳樟醇能提高加氢产物中四氢芳樟醇的含量。以日本进口的合成芳樟醇（含量98.7%）为原料,采用W-6型雷尼镍为催化剂,在（60±10）℃、1～3 MPa氢压的条件下进行氢化,所得四氢芳樟醇含量为98.7%,选择性为100%。     

水杨醛缩取代芳基Schiff碱制备及其光致变色性能研究

制备了水杨醛缩邻(对)氨基苯甲酸Schiff碱,利用红外(IR)、核磁(1H NMR)光谱和元素分析仪(EMS)对化合物结构进行了表征。利用紫外-可见光谱(UV-Vis)研究了两种Schiff碱在乙醇溶液中的光致变色性能。结果表明,两种Schiff碱都具有良好的光致变色性能,其变色过程是由烯醇式结构向酮式结构转变,不存在其它形式的光分解副反应。该类化合物与金属铜离子(Cu2+)能形成稳定配合物,且配合物也具有较好光致变色性能。     

芳香硝基化合物还原方法的研究进展

综述了各种芳香硝基化合物还原制备相应苯胺方法的研究进展,尤其总结了在CO2-H2O体系中绿色、环境友好的还原硝基物制备相应芳胺的新方法,并对各种方法的应用前景进行了评价。     

A new route to synthesis of sulphonato-salen-chromium(III) hydrotalcites: Highly selective catalysts for oxidation of benzyl alcohol to benzaldehyde

The Mg–Al layered-double hydroxides (LDHs) intercalated by three kinds of sulphonato-salen-chromium(III) complexes were prepared and characterized by FTIR, UV–vis, XRD and elemental analysis. It was found that the homogeneous complexes were successfully intercalated into the LDH interlayer via the method of anion exchange followed by coordination with chromium(III) chloride. And the resulting LDH hosted chromium complexes were shown to be effective heterogeneous catalysts for the solvent-free oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using 30% H₂O₂ as oxidant. Furthermore, owing to the different local environment of the central metal ion chromium(III), the catalyst with the backbone of o-C₆H₄ displayed the highest catalytic performance followed by the NH(CH₂CH₂)₂ with the (CH₂)₂ showing the lowest BzH yield. In addition, a tentative mechanism was also discussed.     

Kinetic studies on the catalytic reduction of o-, m-, and p-nitrophenols by hydrazine

The kinetics of the reduction of o, m- and p-nitrophenols by hydrazine over Raney nickel catalysts have been studied spectrophotometrically. The reactions have been found to be first order with respect to both hydrazine and nitrocompound. The first order behaviour has been observed at the initial part of each of the reactions. The influences of solvent, salt and the amount of catalyst on the reaction rate have been investigated. The rate constants have been found to depend on the nature of the substrate, the dielectric constant, the ionic strength and the amount of catalyst. The activation energies for the reactions in various solvent compositions have been determined and their variations interpreted in favour of an ionic mechanism. The effect of the p-substituent on the activation energy has been explained in terms of the electron-shifting capacity of the substituent.     

室温固相研磨法合成邻氨基苯甲酸类芳醛席夫碱的研究

为了寻找清洁而方便的有机席夫碱制备方法,我们以邻氨基苯甲酸和各种芳醛的物质的量之比为1∶1的比例,采用室温固相研磨合成法,在常温下合成了10种邻氨基苯甲酸类芳醛席夫碱化合物,反应几乎定量完成。用熔点测定和元素分析法对其进行表征。重结晶产率达70%～82%,该法具有反应条件温和,反应时间短,产率高和分离提纯容易等特点,是实验室合成邻氨基苯甲酸类席夫碱的一种快捷而实用的方法。     

Effects of solvent polarity on the hydrogenation of xylose

The three‐phase hydrogenation of xylose to xylitol and anomeric equilibria of xylose were studied batchwise in aqueous and alcoholic solvents. Rate equations based on a novel model for semi‐competitive adsorption of dissociated hydrogen and organic species were developed. The proposed kinetic model was well able to predict the xylose, xylitol and also the by‐product concentrations. The model parameters were related to the polarity of the solvent. The sugar equilibria studies gave new information about the temperature dependence of the α–β‐pyranose and pyranose–furanose equilibria of xylose, in both water and aqueous ethanol solutions. It was found that the equilibria in both D₂O and C₂D₅OD follow an S‐shaped curve, the equilibria being shifted towards the α‐form at higher temperatures. The enhancing effect of alcoholic (eg ethanol, 2‐propanol) solvents on the hydrogenation of sugars is notable. We propose that the rate accelerating effect of alcohols is mainly due to the improved hydrogen solubility. Thus, the mass transfer of hydrogen from the gas phase to the liquid bulk, and further to the surface of the catalyst is clearly improved by the use of an alcohol solvent. © 2001 Society of Chemical Industry     

Comments on the Mechanisms of Heterogeneous Catalysis of the Hydrodenitrogenation Reaction

The purpose of this commentary is to draw from recent observations in these laboratories and from literature examples to propose logical mechanisms that describe the catalytic pathways by which heterogeneous catalysts catalyze hydrodenitrogenation.     

新型含芴Schiff碱化合物的合成及其紫外-可见光谱性能研究

通过9-芴甲醛与相应的芳胺衍生物反应合成了两种新型含芴Schiff碱化合物:9-亚甲基19-亚(2-氨基芴)基芴和9-亚甲基-9-亚(2-甲基苯胺)基芴,其结构经核磁共振谱、红外光谱和质谱表征.吸收光谱法测定了两种含芴Schiff碱衍生物在乙醇、四氢呋喃、环己烷和氯仿中的最大吸收波长(λmax),并探讨了分子结构和溶剂...     

纳米氧化镍的低温固相合成及电容性能研究

通过低热固相反应法合成了纳米氧化镍,在不同温度热处理条件下研究氧化镍的结构、形貌及其作为超级电容器电极材料的电化学性能。采用XRD和SEM表征产物的结构特点,采用循环伏安和恒流充放电等方法表征其电化学性能。XRD测试结果表明,所制备的氧化镍为立方相,且随着热处理温度升高,晶型趋于完整。SEM和电化学测试结果表明,高温热处理（>400 ℃）使样品团聚更为严重,导致电极材料利用率降低,质子传递阻力加大,比电容急剧下降;低温处理颗粒分布均匀,粒子间存在孔道,使电极具有较大的比容量（228 F/g）和良好的化学稳定性,在20 mV/s快速扫描速率下,电极显示出良好的倍率特性。     

香豆素席夫碱的合成及荧光性能研究

以香豆素为原料,合成了3个香豆素席夫碱化合物,用元素分析、红外光谱和核磁共振对其结构进行了表征。测定了化合物4、5的荧光光谱,结果表明:所测定的化合物表现出双光子荧光特性,这种香豆素席夫碱结构单元对于合成新型高效双光子荧光有机化合物具有潜在的价值。     

CS-DAS希夫碱的制备及吸附胭脂红的动力学研究

以淀粉和壳聚糖为底物制备壳聚糖双醛淀粉(CS-DAS)希夫碱,利用IR及DSC对产物进行表征,研究了希夫碱对色素胭脂红的动力学及热力学吸附行为。采用Lagergren拟一级吸附速率方程和Lagergren拟二级速率方程拟合吸附动力学数据。结果表明,当胭脂红浓度为20mg/L时,吸附速率随吸附时间的增加而逐渐减小,90min后达到吸附平衡,拟二级速率方程拟合效果好于拟一级速率方程;当胭脂红浓度变化时,吸附容量随胭脂红浓度的增加而增加,当其浓度为40mg/L时,吸附量为22.16mg/g。     

丹皮酚及其席夫碱衍生物的抑菌性研究

以丹皮酚为先导,合成了丹皮酚缩1,3-丙二胺、丹皮酚缩2-羟基-1,3-丙二胺和丹皮酚缩糠胺3种丹皮酚席夫碱衍生物。琼脂扩散抑菌试验表明,丹皮酚及其衍生物对受试4种革兰氏阴性菌、阳性菌皆有明显的抑制作用。     

Substitutent effects on the spectral behaviour and acid-base properties of arylidene derivatives of salicylic hydrazide

The u.v. and i.r. spectra of some arylidene derivatives of salicylic hydrazide have been studied. The u.v. spectra in organic solvents are considered in terms of medium effect and molecular structure. The changes of the spectra in buffer solutions are explained on the basis of the shifts in the acid-base equilibrium set; the various pK values are determined and commented upon in relation to substituent effects. The main bands in the i.r. spectra are assigned and the shift in their positions is discussed in the light of substituent effects.     

Studies on curing kinetics and thermal behavior of phosphorylated epoxy resin in the presence of aromatic amide‐amines

This article describes the synthesis of some novel aromatic amide‐amine curing agents by reacting 1 mole of p‐amino benzoic acid with 1 mole of each of 1,4‐phenylene diamine (P), 1,5‐diamino naphthalene (N), 4,4′‐(9‐fluorenyllidene)‐dianiline (F), 3,4′‐oxydianiline (O), and 4,4′‐diaminodiphenyl sulphide (DS) and were designated as PA, NA, FA, OA, and SA, respectively. The aromatic amide‐amines so synthesized were characterized with the help of spectroscopic techniques, viz., Fourier Transform Infrared, proton nuclear magnetic resonance, and carbon nuclear magnetic resonance. The curing kinetics of the epoxy resins obtained by reacting amines with diglycidyl ether of bisphenol‐A blended with tris(glycidyloxy)phosphine oxide in a ratio of 3 : 2, respectively, were investigated by DSC technique using multiple heating rate method (5, 10, 15, 20°C/min). Activation energies were determined by fitting the experimental data into Kissinger and Flynn‐Wall‐Ozawa Kinetic models. The activation energies obtained through Flynn‐Wall‐Ozawa method were slightly higher than Kissinger method but were comparable. However, both the energies were found to be dependent on the structure of amines. The thermal stability and weight loss behavior of isothermally cured thermosets were also investigated using thermogravimetric analysis in nitrogen atmosphere. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010