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《Journal of Adhesion Science and Technology》2013,27(10):815-829
The hydrolysis of a series of alkyl-substituted alkoxysilanes and an antimicrobial quaternary ammonium silane was investigated in water-acetone solvents by Fourier transform infrared (FTIR) spectroscopy. An internal reflectance cell was employed for the investigation. Rates of sequential hydrolysis of the first, second, and in one case the third alkoxy groups were extracted by nonlinear regression of curves of methanol concentration plotted versus time using data obtained from the FTIR spectra of the reaction mixture. Acid catalysis of the hydrolysis was observed. Condensation of the silanol groups produced by the hydrolysis was investigated using similar techniques and rate data are presented. 相似文献
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采用密度泛函理论M06-2X/6-311G(d)方法,对对苯二甲酸丁二醇酯二聚体的水/醇/氨解反应机理进行了量子化学理论研究。提出了各种可能的水/醇/氨解反应路径,对各反应的中间体、过渡态及产物进行了几何结构优化和频率计算以获得热力学与动力学参数值,分析了对苯二甲酸丁二醇酯二聚体主链酯键中的酰氧键位置水/醇/氨降解的反应机理。计算结果表明:水/醇/氨解条件下能够降低对苯二甲酸丁二醇酯二聚体主链酯键中的酰氧键裂解的反应活化能,使反应更易于进行,水/醇/氨解中主要基元反应步的反应能垒分别约为170.0、155.0和165.0 kJ/mol。对苯二甲酸丁二醇酯二聚体水解产物主要为对苯二甲酸和1,4-丁二醇,醇解产物主要为对苯二甲酸二甲酯和1,4-丁二醇,氨解产物主要为芳香腈和1,4-丁二醇等,其中1,4-丁二醇会进一步降解形成四氢呋喃。在对苯二甲酸丁二醇酯二聚体水/醇/氨解反应过程中,甲醇介质中的裂解反应优于氨气气氛中的反应、氨气气氛中的反应优于水分子环境中的反应,且反应温度的升高可以增加其自发性。 相似文献
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《Journal of Adhesion Science and Technology》2013,27(1):127-149
A review of the literature is presented for the hydrolysis of alkoxysilane esters and for the condensation of silanols in solution or with surfaces. Studies using mono-, di-, and trifunctional silane esters and silanols with different alkyl substituents are used to discuss the steric and electronic effects of alkyl substitution on the reaction rates and kinetics. The influences of acids, bases, pH, solvent, and temperature on the reaction kinetics are examined. Using these rate data, Taft equations and Bronsted plots are constructed and then used to discuss the mechanisms for acid and base-catalyzed hydrolysis of silane esters and condensation of silanols. Practical implications for using organofunctional silane esters and silanols in industrial applications are presented. 相似文献
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采用密度泛函理论B3P86/6⁃31++G(d,p)方法对对苯二甲酸乙二醇酯二聚体的水/醇/氨解反应机理进行了理论研究。设计了水/醇/氨降解过程的各种可能反应路径,对参与反应的各种中间体、过渡态及产物进行了几何结构优化和频率计算以获得热力学与动力学参数值,分析了对苯二甲酸乙二醇酯二聚体主链酯键中的酰氧键位置水/醇/氨降解的反应机理。结果表明,水/醇/氨解能够降低对苯二甲酸乙二醇酯二聚体主链酯键中的酰氧键裂解的反应活化能,使反应更易于进行,其中水解中主要基元反应步的反应能垒最高约为169.0 kJ/mol,氨解最低约为153.0 kJ/mol,其次是醇解约为155.0 kJ/mol。 相似文献
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In an effort to increase utilization of fats and oils with high concentrations of FFA, acid catalysts were investigated at
elevated temperatures to determine their efficacy under various operating conditions. Acid-catalyzed alcoholysis of soybean
oil using sulfuric, hydrochloric, formic, acetic, and nitric acids was evaluated at 0.1 and 1 wt% loadings at temperatures
of 100 and 120°C in sealed ampules, but only sulfuric acid was effective. Kinetic studies at 100°C, 0.5 wt% sulfuric acid
catalyst, and nine times methanol stoichiometry provide >99 wt% conversion of TG in 8 h and less than 0.8 wt% FFA concentrations
at less than 4 h. Reaction conditions near 100°C at 0.1 to 0.5 wt% were identified as providing the necessary conversions
in a 24-h batch cycle while not darkening the product as is typical with high temperatures and catalyst loadings. The oxygen/air
contained in the reaction ampules at the onset of the reaction was not sufficient to color the product, but the product darkened
if atmospheric air contacted the reacting mixture. The presence of small amounts of stainless steel significantly decreased
conversions. 相似文献
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The effects of time and temperature on the alcoholysis of rubber seed, melon seed, linseed, and soyabean oils have been studied. The following temperatures were investigated: 200, 220, 245, and 260°C. Litharge (PbO) was used as the alcoholysis catalyst. The optimum alcoholysis temperature was found to be 245 ± 2 °C for each of the oils. At lower alcoholysis temperatures (<245°C), there is the preferential alcoholysis of seed oils derived from unsaturated acid; and the general alcoholysis rates were found to be in the following order: linseed oil ≈ rubber seed oil ≥ soyabean oil ≈ melon seed oil. The alcohol‐solubility of the oils is generally observed to begin at 42–45% conversion of oils to monoglycerides. The α‐monoglyceride contents of the alcoholysis mixtures of rubber seed and linseed oils were generally similar at methanol tolerance, and higher than those of melon seed and soyabean oils. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1826–1832, 2000 相似文献
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John O Oludipe 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1999,74(8):785-789
The objective of this work was to study the hydrolysis kinetics and also the character of the involvement of the epoxidation catalyst (Na2WO4 – sodium tungstate) on the hydrolysis of cis‐epoxysuccinic acid (the initial product in the hydroxylation reaction of maleic acid by hydrogen peroxide). The results obtained at 65 °C clearly revealed that the hydrolysis reaction exhibits a considerably low rate in the absence of a catalyst whilst the rate is significantly enhanced by the introduction of catalytic quantities of Na2WO4. The phenomenon of end‐product inhibition was observed in this study and the results obtained permitted the development of a kinetic model consistent with experimental observations. Analysis of the kinetic model shows that the reaction is first order with respect to the concentrations of the catalyst and the epoxide. However, tartaric acid has a strong inhibitive influence on the overall reaction rate. © 1999 Society of Chemical Industry 相似文献
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Noncatalytic alcoholysis kinetics of soybean oil 总被引:1,自引:0,他引:1
Reaction kinetics for the alcoholysis of soybean oil with methanol, ethanol, and isopropanol were evaluated in the absence
of catalyst. Metal reactor surfaces catalyzed these reactions, so the reactions were conducted in glass capillary tubes at
120, 150, and 180°C. The reactivity of the alcohols increased with decreasing carbon number. Higher temperatures promoted
faster reactions. Higher alcohol stoichiometries did not significantly increase reaction rates; this was attributed to the
limited solubility of the alcohol in the soybean oil. At less than 20% conversion, the solubility of the alcohol in the oil
phase continuously increased, resulting in increased reaction rates. At approximately 20% conversion, the reaction systems
became homogeneous until a glycerine phase was formed at high conversions. In addition to their fundamental value, these data
provided a basis on which catalytic reactions can be investigated between 100 and 200°C. 相似文献
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Amri Hilmi Mohamed Naceur Belgacem Christian Signoret Alessandro Gandini 《Polymer International》1996,41(4):427-435
The reduction of furyloxirane (FO) with different reducing agents was conducted under various experimental conditions and occurred essentially by the α-opening of the oxirane ring. It was also shown that the presence of Lewis acids favoured this mode of ring opening. The hydrolysis of furanic oxiranes was accompanied by oligomerization even in the absence of a catalyst. Moreover, very small quantities of water induced the oligomerization of FO giving degrees of polymerization of 40–50. This behaviour is unique since aliphatic and aromatic oxiranes are not activated by water alone. The alcoholysis of FO catalysed by metal alkoxides showed variable extents of α- and β-opening of the oxirane ring, depending on the steric hindrance of the alkoxide used. 相似文献
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研究了一种应用微波技术在常压下对废PET催化降解以实现化学回收的方法。考察了在微波作用下,醇解温度、物料配比、催化剂含量及醇解剂官能度对废PET降解程度及降解产物的影响,并利用红外光谱仪对降解产物的化学结构进行了分析。结果表明:综合考虑废PET的醇解程度、醇解产物的性能以及经济成本因素,选定的最佳工艺条件是微波功率500W时,醇解时间15min、反应温度220℃、二甘醇与废PET的质量比为1.25、醋酸锌用量0.2%;其他反应条件不变,将醇解剂改为甘油和二甘醇的混合醇,混合醇与废PET的质量比为1.5,当二甘醇与甘油质量比为1:1时,醇解产物羟值最高,可以达到477mg/g;实验所得的废PET的二甘醇醇解产物是羟基封端分子链含有醚键的聚酯多元醇。 相似文献
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The theory of mass transfer accompanied by chemical reaction has been used for studying the kinetics of alkaline hydrolysis of 2-ethylbutylformate at different temperatures and ionic strengths of aqueous alkaline solution. Experiments have been conducted in a stirred cell having a flat liquid-liquid interface. For aqueous phases containing 1–3 kmol/m3 sodium hydroxide, the alkaline hydrolysis conforms to the fast pseudo-first order reaction regime. The system is of considerable practical importance and can be successfully employed for the measurement of the interfacial area of a mechanically-agitated and flooded packed-bed liquid-liquid contactor. 相似文献
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Pin-Jing He Fan Lü Li-Ming Shao Xiu-Jiang Pan Duu-Jong Lee 《Journal of the Chinese Institute of Chemical Engineers》2007
Both pH and volatile fatty acid (VFA) inhibit the hydrolysis of particulate organic waste. It is not clear yet whether VFA or pH is the dominant factor in hydrolysis inhibition. The effects of pH and acetate on the enzymatic hydrolysis of potato samples containing mainly carbohydrate were studied at fixed pH values (5–9) and with/without 20 g L−1 acetate. The leaching liquors were refreshed at prescribed intervals. Experimental results showed that both pH and acetate influenced the hydrolysis of carbohydrate, but that pH was more influential than acetate. 相似文献
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在干燥碱式碳酸锌催化剂的作用下,以尿素和乙二醇(EG)为原料合成碳酸乙烯酯(EC)。重点考察了催化剂用量、原料配比、反应温度、反应时间对反应结果的影响。并通过GC-MS、FTIR和XRD分析,初步探索了反应机理以及碱式碳酸锌的作用机理。结果表明:当催化剂用量为尿素质量的6%,原料配比n(EG)∶n(尿素)=1∶1,反应温度160℃,反应时间3h,反应压力为0.01MPa时,碳酸乙烯酯收率达到91.64%。尿素和乙二醇合成碳酸乙烯酯的反应中,尿素首先分解生成异氰酸,异氰酸再与乙二醇反应生成中间产物2-羟乙基氨基甲酸酯(2-HEC),最后2-羟乙基氨基甲酸酯脱氨环化生成碳酸乙烯酯。所用碱式碳酸锌催化剂中存在Zn4CO3(OH)6·H2O和ZnO两种晶相,且以ZnO为主活性组分,两种晶相的协同作用提高了反应收率。 相似文献
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高聚合度的聚醋酸乙烯酯醇解制备聚乙烯醇,由于其相对分子质量较大,所以研究其醇解工艺显得尤为必要.就影响醇解工艺的因素,如醇解温度、醇解时间、催化剂浓度等进行了探讨,得出了高聚合度PVAc醇解最佳工艺. 相似文献