共查询到19条相似文献,搜索用时 125 毫秒
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腐植酸与碳酰胺接枝改性的研究 总被引:1,自引:0,他引:1
研究了褐煤及降解的风化煤腐植酸与碳酰胺(CA)-甲醛(F)体系的接枝聚合。考察了影响反应的主要因素。接枝产物(HA-CA)的红外,TG,DTA表征,和对膨润土吸附性能及Zeta电位的影响,揭示了HA接枝碳酰胺的改性具有良好的应用前景。 相似文献
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研究了稀土元素铈(Ⅲ)离子与3,4-二羟基苯甲酸(H3L)在水溶液体系中生成羧基配位化合物的条件,表征其组成为Ce(H2L)2(OH).3H2O。并研究了该配合物在一定条件下,铈离子由羧基配位反应变由为两个邻酚羟基配位的配合物(Ce(HL)n的转型反应及氧化物铈(VI)配合物的反应。 相似文献
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采用pH-电位滴定法研究了乙醇溶液中RE(Ⅲ)与新型荧试剂H2L[5-(2'-羧基苯偶氮)]绕丹宁(Br-RACP)、5-(4'-氯代-2'-羧基苯偶氮)绕丹宁(Cl-RACP)、5-(4'-溴代-2'-羧基苯偶氮)绕丹宁定常数大小为RACP>Cl-RACP>Br-RACP。而与Nd(Ⅲ)的累积生成常数lgβmlh随原子序数Z增大时,研究了浓度对lgβmlh的影响,测定了15种稀土与RACP的ig 相似文献
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用2—羟基—3—羧基—5—磺酸基苯重氮氨基偶氮苯流动注射分光光度法测定汞 总被引:7,自引:1,他引:7
研究了在乳化剂OP存在下,2-羟基-3-羧基-5-磺酸基苯重氮氨基偶氮苯(HCSDAA)-汞(Ⅱ)显色体系流动注射分光光度法。用PH10.0-10.5的Na2B4O7-NaOH缓冲溶液作载流,汞(Ⅱ)与HCSDAA和乳化剂OP的混合试剂反应形成红色络合物。用于测定汞时,方法的线性范围是0.05-1.0mg/L,检测限为0.016mg/L,进样频率为100样/h。直接应用于头发、自来水和废水中微量汞 相似文献
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在束-气条件下,通过检测反应产物的化学发光光谱,研究了亚稳态He(2~3s)原子与甲烷、氯代甲烷(CH_nCl_(4-n),n=1~3)反应中的解离激发动力学过程.观察到反应的主要激发态碎片CH(A~2Δ)、CH(B~2Σ~(-))、CH(C~2Σ~+)、H和CCl(A~2Δ),用参比反应测定了发光碎片的形成速率常数。对CH(A,B)光谱的计算机模拟获得了CH(A~2Δ,v′=0~2)和CH(B,v′=0)的振转分布。该反应的可资用能绝大部分转移成产物的平动能,且He(2~3s)与甲烷及氯代甲烷反应形成CH(A~2Δ,v′=0)的转动分布不同,前者为单Boltzmann分布,后者则在低转动能级上转动温度比高转动态低,近似可用双Boltzmann分布描述,对上述反应机理进行了讨论。 相似文献
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系统研究了聚萘胺膜与Ag、Hg(2+)等十余种金属离子的络合特性。以循环伏安法、交流阻抗分析等方法研究了Ag-PNA电极对抗坏血酸(H2A)氧化的催化作用,提出了电极反应的可能机理。Ag-PNA电极可用于测定试样中的H2A含量。 相似文献
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马来酸酐-苯乙烯多组分单体熔融接枝聚丙烯的机理研究 总被引:38,自引:1,他引:37
用单螺杆挤出机研究了马来酸酐(MAH)-苯乙烯(St)对聚丙烯(PP)的多组分单体自由基熔融接枝体系。研究结果表明,用St作共单体能够显著提高MAH的接枝率。讨论了St用量、引发剂用量对接枝反应的影响。发现当两种单种物质的量比约为1:1时,接枝物的接枝率最高,熔体流动速率(MFR)也最大,通过对反应机理的探讨,认为St和MAH的相互作用或反应在接枝反应中起到了重要的作用,在自由基的作用下,St与M 相似文献
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Olga Ershova Elisabete V. da Costa António J. S. Fernandes M. Rosário Domingues Dmitry V. Evtuguin Herbert Sixta 《Cellulose (London, England)》2012,19(6):2195-2204
The effect of urea on the cellulose degradation under conditions of alkaline pulping has been studied using purified cellulose powder. The increased cellulose yield in the presence of urea was assigned essentially to the carbamation reactions which were confirmed by elemental analysis, UV-resonance Raman and solid-state 13C nuclear magnetic resonance spectroscopy. The stabilizing effect of urea on the cellulose peeling reactions during heating up period of pulping process was suggested based on kinetic studies and additionally confirmed in model reactions using cellobiose. The reaction products formed in alkaline urea solutions were analysed by tandem electrospray ionization mass spectrometry and the occurrence of Maillard type reactions between reducing end groups of cellobiose and urea were evidenced. Both Maillard type reactions and carbamation of reducing end groups were proposed to be a part of cellulose protection mechanism against peeling under the conditions of alkaline pulping. 相似文献
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C. Rosilio A. Ruaudel-Teixier 《Journal of polymer science. Part A, Polymer chemistry》1975,13(11):2459-2471
Evidence is given for solid-state polycondensation reactions in octadecyl urea multilayers, built up by the Langmuir-Blodgett method. The disappearance and infrared frequency modifications of characteristic functional groups are followed by spectroscopy in transmitted and reflected light and in ATR. The crosslinked polymer thus obtained on a solid substrate is compared with the polymer obtained at the liquid-air interface. The chemical reactions are accompanied by molecular reorientation phenomena in multilayers. 相似文献
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Recently, the application of ReaxFF based reactive molecular dynamics simulation (ReaxFF MD) in complex processes of pyrolysis, oxidation and catalysis has attracted considerable attention. The analysis of the simulation results of these processes is challenging owing to the complex chemical reactions involved, coupled with their dynamic physical properties. VARxMD is a leading tool for the chemical reaction analysis and visualization of ReaxFF MD simulations, which allows the automated analysis of reaction sites to get overall reaction lists, evolution trends of reactants and products, and reaction networks of specified reactants and products. The visualization of the reaction details and dynamic evolution profiles are readily available for each reactant and product. Additionally, the detailed reaction sites of bond breaking and formation are available in 2D chemical structure diagrams and 3D structure views; for specified reactions, they are categorized on the basis of the chemical structures of the bonding sites or function groups in the reacting species. However, the current VARxMD code mainly focuses on global chemical reaction information in the simulation system of the ReaxFF MD, and is incapable of locally tracking the chemical reaction and physical properties in a 3D picked zone. This work extends the VARxMD from global analysis to a focused 3D zone picked interactively from the 3D visualization modules of VARxMD, as well as physical property analysis to complement reaction analysis. The analysis of reactions and physical properties can be implemented in three steps: picking and drawing a 3D zone, identifying molecules in the picked zone, and analyzing the reactions and physical properties of the picked molecules. A 3D zone can be picked by specifying the geometric parameters or drawing on a screen using a mouse. The picking of a cuboid or sphere was implemented using the VTK 3D view libraries by specifying geometric parameters. The interactive 3D zone picking was implemented using a combination of observer and command patterns in the VTK visualization paradigm. The chemical reaction tracking and dynamic radial distribution function (RDF) of the 3D picked zone was efficiently implemented by inheriting data obtained from the global analysis of VARxMD. The reaction tracking between coal particles in coal pyrolysis simulation and dynamic structure characterization of carbon rich cluster formation in the thermal decomposition of an energetic material are presented as application examples. The obtained detailed reactions between the coal particles and comparison of the reaction between the locally and globally picked areas in the cuboid are helpful in understanding the role of micro pores in coal particles. The carbon to carbon RDF analysis and comparison of the spherical region picked for the layered molecular clusters in the pyrolysis system of the TNT crystal model with the standard RDF of the 5-layer graphene demonstrate the extended VARxMD as a chemical structure characteristic tool for detecting the dynamic formation profile of carbon rich clusters in the pyrolysis of TNT. The extended capability of VARxMD for a 3D picked zone of a ReaxFF MD simulation system can be useful for interfacial reaction analysis in a catalysis system, hot spot formation analysis in the detonation of energetic material systems, and particularly the pyrolysis or oxidation processes of coal, biomass, polymers, hydrocarbon fuels, and energetic materials. 相似文献
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We report herein a computational study of proton transfer reactions between dithiophosphinic acids (HAs) and water clusters using B3LYP and MP2 methods. The ground-state and transition-state structures of HA-(H(2)O)(n) (n = 1, 2, 3) cluster complexes have been calculated. The influence of water molecules on energy barrier heights of proton transfer reactions has been examined in the gas phase and solution for bis[o-(trifluoromethyl)phenyl]- and bis(2,4,4-trimethylpentyl)dithiophosphinic acids (HA1 and HA2, respectively). Gas-phase calculations indicate that electron-withdrawing substituents and trifluoromethyl groups in the ortho position favor deprotonation of HA1 when three water molecules are included in the cluster. This suggests that at least three water molecules are necessary to solvate the abstracted proton in the presence of the anion. In the case of HA2, the electron-donating groups favor the reverse proton transfer reaction, namely, protonation of dithiophosphinate anion. Bulk solvent effects have been modeled for aqueous and organic media with the CPCM model. The calculated results show that polar solvents can lower the activation energy for less energetically stable transition states that have more localized charges. 相似文献
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以合成焦炭为载体,研究不同种类的钠元素在煤粉燃烧过程中对微细颗粒物生成特性的影响,并通过向载体中添加煤中常见的矿物元素的氧化物(SiO_2、Al_2O_3),反映煤粉燃烧过程中钠与煤中常规矿物的相互作用。结果表明,无机水溶性钠更容易生成稳定的亚微米颗粒物;在缺少氯元素的情况下,有机态钠更容易与煤中的超微米硅铝矿物反应;化学反应和物理捕捉是硅铝矿物捕捉钠元素的两种方式,其中,对于PM1-10的硅铝矿物颗粒,化学反应固定的钠含量是物理捕捉过程的2.4倍。 相似文献
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Tatjana Andjelkovic Jelica Perovic Milovan Purenovic Srdjan Blagojevic Ruzica Nikolic Darko Andjelkovic Aleksandar Bojic 《Analytical sciences》2006,22(12):1553-1558
Isolated soil humic acid (HA) and commercial Aldrich HA were derivatized by esterification with methanol-thionyl and acetylation with acetic anhidride, in order to obtain derivatives with selectively blocked carboxyl and phenol groups, respectively. Results obtained by FT-IR spectroscopy and potentiometry show that the methanol-thionyl procedure is a selective, specific and efficient route for blocking carboxyl groups. The good correlation between results obtained by direct potentiometry after HA esterification and by classical calcium-acetate and baryta exchange methods suggests that esterification followed by direct acid-base potentiometric titration can be used as a method for the estimation of carboxyl and phenol group contents. Phenol groups can not be specifically identified by the acetylation method, due to the low selectivity of the acetylation method. The average values of apparent and intrinsic pK of underivatized and derivatized HAs confirm decrease in ionizable groups content due to derivatization and their values are related to the different chemical structures of the acids. 相似文献
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Thermal analysis was used to study the influence of CaCl2 and urea as possible chemical additives inhibiting coal oxidation process at temperatures 100?C300?°C. Weight increase due to oxygen chemisorption and corresponding amount of evolved heat were evaluated as main indicative parameters. TA experiments with different heating rates enabled determination of effective activation energy E a as a dependence of conversion. In the studied range of temperatures, the interaction of oxygen with (untreated) coal was confirmed rather as a complex process giving effective activation energies changing continuously from 70?kJ?mol?1 (at about 100?°C) to ca. 180?kJ?mol?1 at temperatures about 250?°C. The similar trend in E a was found when chemical agents were added to the coal. However, while the presence of CaCl2 leads to higher values of the effective activation energies during the whole temperature range, urea causes increase in E a only at temperatures below 200?°C. Exceeding the temperature 200?°C, the presence of urea in the coal induces decrease in activation energy of the oxidation process indicating rather catalysing than inhibiting action on coal oxidation. Thus, CaCl2 can only be recommended as a ??real?? inhibitor affecting interaction of coal with oxygen at temperatures up to 300?°C. 相似文献