对二甲苯液相催化氧化动力学(Ⅲ)催化剂配比与浓度的影响

对二甲苯(PX)高温液相催化氧化过程采用Co-Mn-Br三元复合催化剂,对该催化体系的机理作了深入探讨,针对催化剂总浓度、溴浓度以及钴锰配比对主反应的影响规律进行了系统的动力学实验,获得了各步反应速率随催化剂浓度与配比的变化关系.研究发现,在实验所考察的温度与催化剂组成条件下该催化体系存在一最佳钴锰配比（1∶1）,溴浓度和催化剂总浓度对反应速率都有显著的影响,其中以溴浓度最为敏感.     

TS-1催化苯羟基化制苯酚的本征动力学

TS-1分子筛催化苯羟基化法制苯酚是一种绿色工艺路线。对以TS-1为催化剂苯与过氧化氢反应制苯酚的本征动力学进行了研究。考察了搅拌速度、苯浓度、过氧化氢浓度以及反应温度等因素对苯酚初始生成速率的影响,并采用幂函数方程进行实验数据拟合。结果表明,在消除内外扩散影响的条件下,反应对于苯、过氧化氢的反应级数分别为0.62和0.55,反应的活化能为101.31 kJ/mol。依据上述结果建立了反应的本征动力学方程,并对模型进行验证,结果显示模型计算得到的苯酚初始生成速率与实验值的平均相对偏差为6.81%,吻合较好。研究得到的动力学模型为TS-1催化苯羟基化-膜分离耦合制备苯酚的条件优化及过程开发提供依据。     

碳酸乙烯酯和乙醇均相酯交换反应研究

研究了以乙醇钠为均相催化剂,碳酸乙烯酯和乙醇酯交换合成碳酸二乙酯同时联产乙二醇的过程。考察了催化剂浓度、醇酯比、温度等因素对反应的影响,得到较适宜的工艺条件。以加成-消除机理为基础,分别以两步亲核加成基元反应为速率控制步骤,提出了两个动力学模型,用Runge-Kutta法和非线性最小二乘法估计了相应的模型参数。统计检验表明,两个模型在所研究的压力、温度和组分的浓度范围内均是适用的。     

对羧基苯甲醛在Pd/AC催化剂上加氢反应表观动力学

在实验室间歇高压釜中对Pd/AC催化剂上对苯二甲酸(TA)加氢精制过程的对羧基苯甲醛(4-CBA)加氢反应进行了研究。考察了氢分压、反应温度、催化剂颗粒大小对4-CBA消失速率的影响,并采用幂函数动力学模型拟合得到了接近工业反应温度范围的表观动力学方程。结果表明,氢分压0.35~1.0 MPa时,对4-CBA加氢反应的速率影响很小,反应速率对氢分压可视为零级,随着温度升高和催化剂颗粒减小,4-CBA加氢反应速率显著增加;工业条件下的TA加氢精制过程存在着严重的内外扩散,4-CBA加氢反应的表观活化能为28 kJ/mol,对4-CBA的反应级数为1.23。     

叔丁醇脱水反应动力学研究

以国产NKC-9型强酸性阳离子交换树脂为催化剂,在常压液相下进行了叔丁醇脱水的反应动力学研究,为由叔丁醇脱水生产异丁烯工艺的开发提供了基本理论依据。在消除内外扩散影响下,讨论了反应温度、反应物初始浓度和催化剂用量等条件对反应速率的影响。结果表明：反应温度升高,将加快反应速率：水的存在对此反应过程产生阻碍效应,随着反应物初始浓度中水含量的增加,反应速率减小。考虑异丁烯在液相中含量很低以及产物水对反应的阻碍效应,建立了该反应的动力学模型,并得到了相应的模型参数。在实验温度范围内,速率模型计算结果与实验结果吻合较好。     

铋钼催化剂上丁烯氧化脱氢制丁二烯的本征动力学

采用水热法制备了Bi2MoO6纳米片催化剂、共沉淀法制备了BiMoV0.15催化剂,在固定床反应器中研究了两种催化剂上丁烯氧化脱氢制丁二烯的本征动力学.采用幂函数模型对不同条件下测得的动力学数据进行了拟合,建立了本征动力学模型,并得到了活化能和反应级数等相关参数.结果表明:由于不同的反应温度区间拥有不同的速率控制步骤,Bi2MoO6纳米片催化剂和BiMoV0.15催化剂均在653 K左右存在活化能转折现象;且不论在何温度区间,Bi2MoO6纳米片催化剂的活化能均低于BiMoV0.15催化剂的活化能,表明Bi2MoO6纳米片催化剂能有效降低反应能垒,使得反应更易进行;经检验,所得的本征动力学模型可靠性良好.进一步将动力学实验结果与MarsvanKrevelen(MvK)机理相结合,阐明了动力学唯象规律和反应机理的内在联系.     

生物质超临界水气化制氢技术的研究现状

介绍了国内外生物质超临界水气化制氢技术的研究进展,并对该技术的反应机理、影响因素、不同的催化剂、催化机理进行了评述.指出对气化反应机理的研究应该以关键化合物为基础;在反应器形式和催化剂一定的条件下,影响气化结果的主要因素是反应温度、进料浓度、加热速率、碱性化合物添加剂;碱性化合物添加剂和碳催化剂或金属催化剂结合使用可能会实现高效催化气化过程.     

固载TiO_2光催化降解废水中氨氮的动力学模型

采用固载TiO2光催化氧化处理模拟和实际氨氮废水,研究了反应的动力学模型和反应条件对氨氮氧化速率的影响。结果表明,在低浓度氨氮的TiO2光催化过程中,氨氮分子在催化剂表面的吸附是整个降解过程的控制步骤,过程的动力学方程遵循r=kKCA/(1+KCA)。若此时,氧浓度为常数时,氨氮在水中的降解可用拟一级反应模型来近似;催化剂投加量、曝气量、反应温度、光强等反应条件对反应的表观速率常数有着显著的的影响。     

高直链淀粉的醋酸酯化反应动力学

基于二级反应动力学机理,研究了以甲基磺酸为催化剂的高直链淀粉醋酸酯化动力学过程。讨论了不同温度、催化剂用量以及醋酸与酸酐比例等反应条件对酯化反应速率常数k的影响,求得酯化反应活化能E=43.88kJ/mol。     

硫酸催化合成邻苯二甲酸二甲酯的动力学

在工业生产过程所涉及的温度条件下对浓硫酸催化合成邻苯二甲酸二甲酯的化学反应动力学进行了实验研究,测定丫两个实验温度(90℃,100℃)下硫酸催化剂浓度为0.2%～0.9%时反应中各物质的浓度变化,获得了该温度下和催化剂浓度范围内的反应动力学表达式和反应速率常数.实验结果表明,实验条件下的反应速率对邻苯二甲酸单甲酯,甲醇...     

Esterification of fatty acid over Tunisian acid activated clay: kinetic study

Tunisian acid activated clay was investigated as catalyst in the esterification of stearic acid with ethyl alcohol, carried out in a semi-continuous reactor. Kinetic study shows that the reaction is first order with respect to acid concentration. The activation energy found was 21 kJ/mol. This result suggests that the reaction process was controlled by a diffusional step. A kinetic model, giving the apparent constant rate as a function of temperature and catalyst concentration, has been established. This equation has been then successfully applied for a complex mixture of fatty acid.     

固体超强酸SO_4~(2-)/TiO_2催化合成亚油酸乙酯

用两相滴定沉淀法制备了SO2-4/TiO2固体超强酸催化剂,得到了适合亚油酸酯化的催化剂制备工艺条件:硫酸浸渍浓度0 75mol/L,浸渍时间4h,焙烧温度450℃,焙烧时间4h。首次将该催化剂用于亚油酸的酯化反应催化合成亚油酸乙酯,考察了物料比、反应时间、催化剂用量对亚油酸与乙醇酯化反应的影响规律,最佳反应条件为:n(无水乙醇)/n(亚油酸)=4,w(催化剂)=3%(相对于亚油酸),反应时间8h,亚油酸转化率可达93%。     

Some additional notes on the kinetics and theory of fatty oil hydrogenation

1. Equations are given for estimating from the composition of oil samples the relative reaction rates of the different unsaturated fatty acids in an oil subjected to catalytic hydrogenation.
2. Application of the equations to data from the hydrogenation of cottonseed oil reveals that the ratio of reaction rates, linoleic acid to oleic acid, varies from about 4 to 1 in very non-selective to about 50 to 1 in very selective hydrogenation. Re-examination of analytical data on two series of linseed oils hydrogenated selectively and non-selectively showed the following relative reaction rates for oleic, isolinoleic (9: 10, 15: 16 octadecadienoic), linoleic, and linolenic acids, respectively: non-selective, 1, 2.5, 7.5, 12.5; selective, 1, 3.85, 31, 77. In the non-selective hydrogenation of the oil, 24% of the linolenic acid reacting went to linoleic acid, 65% to isolinoleic acid, and 11% directly to oleic acid. In the selective reaction the corresponding figures were none to linoleic acid, 54% to isolinoleic acid, and 46% to oleic acid. The behavior of soybean oil hydrogenated selectively was quite similar to that of linseed oil.
3. The results are discussed in relation to the theory of catalytic hydrogenation. They indicate that the solution of hydrogen in the oil and the adsorption of unsaturated oil on the catalyst are the two steps which are controlling with respect to the reaction rate. It is suggested that the hydrogen pressure, the degree of hydrogen dispersion through the oil, the catalyst concentration, and the temperature all affect the selectivity of the reaction through their influence on the concentration of hydrogen in the reaction zone, with selectivity being favored by a low concentration.

     

Mechanism and kinetics of the CoCl2-catalyzed esterification reaction of castor oil with oleic acid

The apparent orders of the Lewis acid-catalyzed esterification reactions between castor oil and oleic acid are known to change with the catalyst used and with the reaction temperature. A mechanism is proposed in this study to explain the variations (with temperature) in the apparent orders of the cobalt chloride-catalyzed esterification reaction between castor oil and oleic acid. According to the proposed mechanism, an acid-catalyst intermediate forms in an initial, fast quasi-equilibrium step, and this intermediate then reacts with the oil to yield the products and to regenerate the catalyst in the rate-determining second step. A general rate expression, with an acid concentration term and a temperature-dependent constant in the denominator, is derived from the proposed mechanism and is verified with data obtained at different temperatures.     

玉米油酶法合成甘油二酯工艺优化研究

以玉米油、甘油为原料,在无溶剂体系中用固定化脂肪酶Lipozyme TL IM催化合成甘油二酯,通过单因素试验和响应面试验研究底物摩尔比(亚油酸/甘油)、反应温度、反应时间、酶质量分数和初始水质量分数等因素对亚油酸转化率的影响。得出:反应温度、底物摩尔比、反应时间、酶质量分数对亚油酸转化率影响较大;影响酯化反应中亚油酸转化率的主次因素依次为反应温度、底物摩尔比、反应时间、酶质量分数;最佳工艺条件为亚油酸和甘油的摩尔比为2.10∶1,反应温度为61.16℃,反应时间为12.17 h,酶质量分数为20.09%,亚油酸转化率达到75.69%。Lipozyme TL IM连续反应3批次,其相对酶活仍有65.7%。     

Study of the effect of BDMA catalyst in the epoxy novolac curing process by isothermal DSC

Epoxy novolac/anhydride cure kinetics has been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was an epoxy novolac resin (DEN431), with nadic methyl anhydride as hardener and benzyldimethylamine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants, were investigated. The cure reaction was described with the catalyst concentration, and a normalized kinetic model developed for it. It is shown that the cure reaction is dependent on the cure temperature and catalyst concentration, and that it proceeds through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained using the Arrhenius kinetic model. A suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetics of epoxy novolac resin compositions as a function of the catalyst content and temperature. Copyright © 2003 Society of Chemical Industry     

选择反应法制备高纯油酸

提出一种新的高纯油酸制备方法,以动物油酸为原料,其中亚油酸、亚麻酸与顺丁烯二酸酐选择性反应,经分离得到90%以上含量的高纯油酸。研究了反应温度、催化剂用量、反应物物料比对亚油酸反应速率的影响,其中反应温度影响最大,其它反应条件相同,180℃时反应6 h亚油酸含量降至最低,而210℃时1 h即降至最低;催化剂I2用量0.15%和0.2%时亚油酸反应速率比较接近,0.25%时有明显增加;顺丁烯二酸酐与亚油酸物料比为1.1与1.5时反应速率变化较小。同时研究了反应温度和催化剂用量对反式油酸含量的影响,反应温度210℃,反应时间2 h时,反式与顺式油酸的比值为0.49,而反应温度180℃,反应时间延长至6 h比值降为0.13。降低反应温度,延长反应时间可以降低产物反式油酸含量。     

石煤灰渣酸浸提钒工艺中钒的浸出动力学

采用液-固多相反应的缩芯模型研究了石煤灰渣中V2O5的浸出动力学,考察了酸浸温度、硫酸浓度对V2O5浸出反应速率的影响. 结果表明,在实验温度范围内,V2O5的浸出过程为固膜扩散控制,浸出反应的表观活化能为29.96 kJ/mol. 当硫酸浓度小于6 mol/L时,浸出属化学反应控制过程;当硫酸浓度大于6 mol/L时,浸出过程为固膜扩散控制,其表观反应级数为1.199. 提高酸浸温度可提高V2O5的浸出率;在硫酸浓度小于6 mol/L时提高硫酸浓度,可提高V2O5的浸出率;而高于该值提高硫酸浓度对V2O5浸出率的提高无明显作用.     

八甲基环四硅氧烷/氨基取代有机硅单体的本体阴离子共聚动力学

通过实验分析了八甲基环四硅氧烷(D4)／N—β—氨乙基-γ-氨丙基甲基二甲氧基硅烷(APAEDMS)的本体共聚机理，并结合普适的阴离子聚合机制建立了D4／APAEDMS本体共聚速率模型。通过因素(温度、催化剂浓度及原料单体配比)实验考核并完善了所建立的速率模型。研究表明，D4／APAEDMS的本体共聚具有阴离子聚合特点，也含有部分逐步聚合行为，在APAEDMS/D4质量比小的情况下，可以用普适的阴离子聚合方程进行模型化。     

Crosslinking kinetics and network formation in organic coatings containing hexamethoxymethylmelamine

We have developed a kinetic model of the crosslinking reaction of hydroxy-functional acrylic copolymers with fully alkylated melamines. This model accurately describes the extent of the crosslinking reaction as a function of cure time and melamine concentration in coating films. Using this model, we have determined the effects of acid catalyst concentration and strength and the effects of cure temperature on the rate constant of the crosslinking reaction. The rate constant is proportional to the catalyst concentration and to the square root of the acid constant of the catalyst. The temperature dependence of the rate constant follows an Arrhenius rate law with an activation energy of 12.5 kcal/mol independent of catalyst type. Amine salts of p-toluenesulfonic acid have been compared with p-toluenesulfonic acid as catalysts in these coatings at different bake temperatures. These kinetic results have been used in a network structure model to calculate the cure response of these coatings as a function of formulation variables.