高温液态水中果糖无催化分解反应动力学

研究了压力10 MPa下、温度453.15～493.15 K范围内果糖在高温液态水中的无催化分解反应动力学.实验结果表明,在无任何催化剂条件下,果糖能顺利进行分解反应,且随着温度的升高,分解反应速率常数显著地增大.在本实验范围内,果糖分解反应的活化能为126.16 kJ•mol^-1.另外,对不同温度下反应时间对果糖分解的主要产物——5-羟甲基糠醛收率的影响进行了考察.通过控制反应条件可以有选择性地调节产物分布.     

高温液态水中木糖无催化分解反应动力学

研究了压力10 MPa、温度180~120℃下木糖在高温液态水中的无催化分解反应动力学。实验结果表明,在无任何催化剂条件下,木糖能顺利进行分解反应。在实验范围内,木糖分解反应的活化能为123.27 kJ/mol。另外,对不同温度下反应时间对木糖分解的主要产物糠醛收率的影响进行了考察。通过控制反应条件可以有选择性地调节产物分布。     

高温液态水中氯化铜催化葡萄糖分解反应动力学

以纤维素的水解产物葡萄糖为模型物质,利用小型高压反应釜系统地测定了不同反应温度 （423.15K～463.15K）和不同的氯化铜浓度（0～0.08M）对葡萄糖和中间产物5-羟甲基糠醛（5-HMF）分解动力学的影响,结果表明反应温度的提高和氯化铜浓度的增加都能促进葡萄糖和5-HMF的分解反应,提高乙酰丙酸（LA）的收率。采用相关系数比较法确定了葡萄糖和5-HMF分解反应的级数均为一级。利用一级动力学模型对葡萄糖和5-HMF分解反应动力学数据进行了拟合,求得葡萄糖分解生成5-HMF的主副反应活化能分别为134.65kJ.mol^-1、144.1kJ.mol^-1,而5-HMF分解生成LA的主副反应活化能分别为131.97kJ.mol^-1、135.18kJ.mol^-1。本文的研究工作能为葡萄糖水解反应机理的探索以及高活性、高选择性催化剂的开发提供重要的基础数据。     

高温液态水中有机酸对果糖分解反应动力学的影响

研究了压力10MPa下、温度453.15～493.15K范围内高温液态水中有机酸（甲酸、乙酸）对果糖分解反应动力学的影响. 实验结果表明，在有机酸存在下，果糖分解反应速度大大加快.在相同浓度有机酸存在时，甲酸对果糖分解反应的促进作用明显大于乙酸.对不同温度、有机酸和反应停留时间对果糖分解的主要产物——5-羟甲基糠醛(5-HMF)和乙酰丙酸(LA)收率的影响进行了考察. 果糖分解反应主要由果糖分解为中间产物5-HMF和5-HMF进一步分解成LA两步组成，乙酸的加入加快了第一步反应速度，而对第二步反应无明显影响，因而中间产物5-HMF收率可高达83%;甲酸的加入可同时加快果糖分解为中间产物5-HMF和5-HMF进一步分解为LA的速度，因此LA的收率得到了较大的提高.     

C207铜基催化剂常压甲醇分解反应动力学(Ⅰ)本征动力学模型

在直流流动积分反应器中常压下研究了C207催化剂甲醇分解反应本征动力学。实验温度、气体组成与甲醇合成工业条件相接近。以实验測定数据应用改进高斯-牛顿法对动力学模型参数进行估值,获得甲醇分解反应本征动力学方程。     

金属氯化物对高温液态水中葡萄糖分解反应动力学的影响

以纤维素水解产物葡萄糖为模型物质,利用小型高压反应釜测定了180℃下13种金属氯化物催化葡萄糖和中间产物5-羟甲基糠醛(5-HMF)分解反应动力学数据,并用一级反应动力学模型对葡萄糖及5-HMF分解反应动力学数据进行了拟合。结果表明,不同的金属氯化物对葡萄糖和5-HMF的分解反应具有不同的催化效果,其中FeCl₃、NiCl₂和ZnCl₂可大大提高葡萄糖分解反应的速率,而FeCl₃和CuCl₂可大大提高5-HMF分解反应的速率。在碱金属、碱土金属和过渡金属氯化物中,过渡金属氯化物对葡萄糖及5-HMF分解反应的催化效果明显占优。对于第四周期金属元素,随着原子量的增加,葡萄糖分解反应速率常数呈现增加的趋势。金属氯化物对葡萄糖和5-HMF分解反应的催化活性随金属离子pK_a值的减小而增强。本文得到了金属氯化物对葡萄糖和5-HMF分解反应影响的规律,为生物质资源的高效利用提供了重要的基础数据。     

葡萄糖和蔗糖热分解过程的动力学分析

对葡萄糖和蔗糖的热分解过程进行了TG-DTA研究,采用Kissinger法、Friedman法及非线性拟合法获得了分解过程的反应机理和动力学参数. 结果表明,葡萄糖比蔗糖更易分解. 葡萄糖的分解过程分别为二级和一级反应,蔗糖的分解过程分别为n级和一级反应. 利用非线性拟合法给出了葡萄糖与蔗糖热分解过程的完整反应途径和动力学参数,葡萄糖三阶段的活化能分别为132, 150和253 kJ/mol,指前因子分别为11.6, 11.1和19.6 s-1;蔗糖两阶段的活化能分别为105和229 kJ/mol,指前因子分别为8.2和18.6 s-1.     

燃烧固硫反应的动力学和热力学及其影响固硫产物分解因素的研究

煤在高温条件下燃烧不利于固硫反应，并从热力学角度出发，得出了煤燃烧中钙基固硫剂反应自由能与温度的关系函数，由化学反应动力学得出院 硫酸钙分解反应的动力学方程及其相关参数，在还原性气氛中，从理论和实验上都证明了硫酸钙在较低温下会发生二次分解，理论分解温度与实际分解温度非常吻合，煤灰中氧化钙和三氧化二铝的存在，可以提高硫酸钙的分解温度同阳也给出了钙基固硫剂的应用条件。     

微波作用磷矿分解反应非等温动力学研究

实验研究了微波场对硫酸分解磷矿过程的影响。结果表明随着微波功率的增加,磷矿转化率、反应体系温度和升温速率都在增高．提出的微波非等温磷矿分解反应动力学模型与实验结果很好地相符．通过与相同温度下无微波作用的实验结果比较,验证了“微波非热效应”的存在,并初步分析了微波场对硫酸分解磷矿过程的作用机理。     

分子筛催化葡萄糖水解的宏观动力学

分别采用硅铝比为20~25和30的两种ZRP-5分子筛催化剂研究不同温度下葡萄糖水解动力学。研究结果表明,葡萄糖水解属于一级反应,反应温度显著地影响葡萄糖的转化。在相同反应温度下,前者作用下葡萄糖水解的表观反应速率常数大于后者。前者作用下葡萄糖水解的表观活化能为99.24 kJ/mol,后者作用下葡萄糖水解的表观活化能为108.99 kJ/mol。该反应动力学方程的葡萄糖水解转化率计算值与实验值吻合较好。     

The preparation of 5-hydroxymethylfurfuraldehyde from high fructose corn syrup and other carbohydrates

5-Hydroxymethylfurfuraldehyde (HMF) was prepared from high fructose corn syrup (HFCS), or crystalline D -fructose, in high yield and purity. A 95–97% conversion of fructose to HMF was achieved using 25 mol% (based on fructose) boron trifluoride etherate catalyst in dimethyl sulphoxide, under a nitrogen atmosphere, a reaction temperature of 273 K and 30 min reaction time. Inferior yields of HMF were obtained from glucose and starch.     

芬顿试剂催化糖类制备5-羟甲基糠醛

研究了在水-正丁醇双相体系中,芬顿试剂催化转化淀粉、葡萄糖和果糖为5-羟甲基糠醛（5-HMF）的反应。考察了多种影响因素,包括反应温度、反应时间、水和正丁醇比例、芬顿试剂（Fe²⁺和H₂O₂）比例,淀粉、葡萄糖和果糖为底物的5-HMF最高收率分别达到46.5%、47.4%和61.7%。探讨了芬顿试剂催化糖类制备5-HMF的作用机理,即芬顿试剂可以降解淀粉为葡萄糖,催化葡萄糖异构化为果糖,催化果糖生成5-HMF。     

强酸性树脂催化下六元糖降解反应动力学

开展了以固体酸替代无机酸降解模型物质六元糖的研究。利用小型高压反应釜测定了在130～160℃范围内Amberlyst 35W和36W树脂催化下葡萄糖和果糖的降解反应动力学,结果表明35W树脂的加入对葡萄糖异构化成果糖的速率影响较小,但可提高果糖脱水生成中间产物5-羟甲基糠醛以及5-羟甲基糠醛脱羧生成乙酰丙酸的速率,从而提高产物乙酰丙酸的收率;在0.2 g 35W树脂催化下,葡萄糖和果糖的降解反应活化能分别为111、97.0 kJ·mol^-1。Amberlyst 36W与35W具有相似的催化活性,同时Amberlyst 35W和36W在实验条件下可以重复使用。该研究结果证实了用耐水型强酸性树脂替代现有的无机酸催化制备乙酰丙酸的可能性。     

金属离子催化葡萄糖异构化和脱水反应特性研究

以金属氯化物为催化剂，研究金属离子对葡萄糖异构化和脱水反应的催化特性。考察金属离子种类、用量和温度对反应过程的影响，用动力学模型拟合实验数据，定量分析金属离子的催化规律。葡萄糖脱水制备HMF的反应是一个串联反应，基于此机理构建的动力学模型能准确描述各组分浓度随时间的变化。Ni²⁺、Cr³⁺和Sn⁴⁺具有良好的催化活性，但3种金属离子呈现不同的催化特性。Sn⁴⁺的葡萄糖转化速率最快，Ni²⁺最慢，但Sn⁴⁺的副反应速率常数是Ni²⁺的约20倍。实验范围内，增加Ni²⁺用量，葡萄糖异构化和副反应速率加快，但对果糖脱水过程没有催化活性。增加Cr³⁺用量能显著提升葡萄糖异构化速率，对其它反应影响不大。随着Sn⁴⁺用量的增大，各步反应速率均加快，但整个反应过程中的副反应的严重程度有所降低。反应速率常数随温度的变化规律遵循Arrhenius模型，对Ni²⁺而言，升高温度更能促进果糖副反应的发生；金属离子为Cr³⁺时，升高温度有利于果糖脱水生成HMF；而对于Sn⁴⁺，升高温度则更有利于葡萄糖的异构化。     

Kinetic investigation into glucose-, fructose-, and sucrose-activated autoxidation of methyl linoleate emulsion

Autoxidation of methyl linoleate emulsions in aqueous phosphate buffer solutions in the presence of glucose, fructose, and sucrose has been studied by the rate of oxygen uptake. Oxidation rates increased with increasing concentration of sugars in the system. At comparable molar ratios of sugar to methyl linoleate the rate of oxidation in the presence of fructose was greater than with glucose which, in turn, was greater than with sucrose. Oxidation rates increased with pH until a maximum rate was reached at pH 8.00. There was less conjugation and more CO₂ with fructose than with glucose at a comparable level of oxygen uptake and pH value. This suggested concurrent oxidation of methyl linoleate and sugars; fructose is the most readily oxidized of those studied. Sugars seemed to be effective only in combination with the resulting methyl linoleate hydroperoxide. The effect of sugars rests in an activation of the decomposition of the linoleate hydroperoxide, and on the acceleration of the autocatalysis. The activation energy values for the autoxidation of methyl linoleate emulsions in the presence of sucrose, glucose, and fructose are 14.9, 10.6, and 10.6 K. Cal./mol. at pH 5.50; 16.0, 10.8, and 10.4 K. Cal./mol. at pH 7.00; and 14.4, 10.2, and 8.8 K. Cal. at pH 8.00, respectively. Addition of ascorbic acid to the system at zero time or after 2 hrs. increased oxygen absorption. It appeared that oxidized methyl linoleate caused co-oxidation of the ascorbic acid. Additions of nordihydroguaiaretic acid, propyl gallate, and hydroquinone to the system were ineffective in stopping oxidation when they were added after oxidation had commenced. They reduced effectively the rate of oxidation when added at zero time. Presented at the 52nd annual meeting, American Oil Chemists' Society, St. Louis, Mo., May 1–3, 1961. American Meat Institute Foundation Journal Paper No. 215.     

Effect of Reaction Conditions on the Volatile Pyrazines Components of Defatted Flaxseed Meal in the Maillard Reaction System

Defatted flaxseed meal, as a high-protein by-product can be used as a good raw material for the Maillard reaction (MR). A MR model system was established using glucose, fructose, and glucose/fructose (1:1) to produce volatile compounds typically obtained from defatted flaxseed meal protein hydrolysate; these compounds were analyzed using head-space solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC–MS). From the 12 MR model reaction groups, the production of pyrazines was between 12.76% and 26.56%. In the 1G group (the group prepared using DH₁ = 7.87% with a glucose concentration of 10%), the amount of pyrazines generated reached 26.56%, and this was higher than that of the other 11 model reaction groups. The effect of reaction temperature (100–150 °C), reaction time (10–60 min), and sugar concentration (5–30%) on pyrazine content was determined using the 1G group. The results of this study indicated that the effect of temperature on pyrazine production was higher than that exerted by reaction time and glucose addition. The pyrazine content reached the maximum at a reaction temperature of 140 °C. The degree of reaction and pH value were also determined; the results demonstrated that accumulation of pyrazines was suboptimal when the pH of the system was dramatically decreased. For the overall reaction, the pyrazine content remained similar to that of the final products; however, the pyrazine content exhibited little correlation with the intermediate products in the MR.     

Catalytical conversion of fructose and glucose into 5-hydroxymethylfurfural in hot compressed water by microwave heating

Production of 5-hydroxymethylfurfural (5-HMF) from glucose and fructose catalyzed by TiO₂ and ZrO₂ under microwave irradiation was studied. For the case of TiO₂ used in the fructose reaction, 5-HMF yield was 38.1% for a fructose conversion of 83.6% for 5 min reaction time. A 5-HMF yield of 30.5% for a fructose conversion of 65% was obtained for 5 min reaction time in the presence of ZrO₂. The ZrO₂ was found to promote isomerization of glucose to fructose, in which the selectivity of fructose from glucose became higher than 60% for about 50% glucose conversion for a reaction time of 1 min. Under the conditions (5 ml of 2 wt% fructose solution, 0.05 g of TiO₂, 200 °C, and 3 min), fructose conversion and HMF yields by microwave heating (73% and 35%, respectively) were higher than those by sand bath heating (27% and 12%, respectively).