丙酮醛

The method of 4-methylimidazole synthesis using pyroracemic aldehyde was selected,and flow chart and operation process were studied.

本文对4-甲基咪唑常用的几种合成方法进行了介绍，对其工业化生产的优缺点进行了对比，最终选定了丙酮醛法，并给出了工艺流程图和操作步骤。

In recent years, the demand for methylglyoxal increased with the rise of the demand for imidazole and furanone.

近年来随着咪唑以及呋喃酮等香料需求的增加，丙酮醛的需求也在逐步升高。

Pyruvaldehyde was synthesized with acetone or 1,2 propanediol as starting material respectively.With n∶n=1 00∶0 79,3 0-4 0 g potassium chlorate as catalyst,and water and glacial acetic acid as solvent,refluxing on water bath of 60-75 ℃ for 4 h,bromoacetone was obtained in 63 5% yield.

分别用丙酮和 1，2 丙二醇做原料合成了丙酮醛。n∶n =1 0 0∶0 79，加入 3 0～4 0g氯酸钾做催化剂，水和冰醋酸做溶剂，水浴温度为 6 0～ 75℃，回流 4h ，制得产率为 6 3 5 %的溴丙酮。V∶V =11 9∶1 0 ，通入空气，在 6 5～ 70℃反应 5～ 8h ，制得产率为 5 9 6 %的丙酮醛。

In this paper, the structures of methylglyoxal and 1,1-dimethoxy-2-propanone are identified by GC-MS, NMR and the standard samples. The reaction conditions of catalyst oxidation and acetalation according to reaction mechanisms are discussed.

本文运用质谱、核磁和标样确定了中间体丙酮醛及其产物1，1-二甲氧基丙酮的结构，并结合反应机理对催化氧化和醛保护的反应工艺条件进行了探索。

As for acetalation, we research the effects of acid kinds, acid quantity, temperature solvents on it and get the conclusions that the optimized acid is sulfuric acid, the optimized temperature is 65 °C, the reaction time is five hours, and the material ratio of sulfuric acid to methylglyoxal to methanol is 0.028:1:6.837.

在醛保护一步中，研究了酸种类、酸用量、温度及其溶剂的影响，得到了本反应的较好条件是：酸为浓硫酸，反应温度为65℃，反应时间为5小时，浓硫酸：丙酮醛：甲醇的配比为0.028：1：6.837，反应收率可达81%。

Secondly, the silver based catalysts modified by phosphorus, zirconium, zinc, potassium and so on using molecular sieve as carrier, which were produced by ion-exchange method, had also good catalytic performance for 1,2-propane glycol oxidation to methylglyoxal. The conversion of 1,2-propane glycol and the selectivity of methylglyoxal were both high, and the impurity such as formaldehyde and acetaldehyde in the product is little. At the condition of the temperature 300 ℃, the molar ratio of oxygen to 1,2-propane glycol 1.7:1, the space velocity 6000h~(-1), and the concentration of 1,2-propane glycol 70wt%, the conversion of 1,2-propane glycol is 90% and the selectivity of methylglyoxal is 45% on the Ag-P catalyst.

其次对采用离子交换法制备的负载在分子筛上的银系催化剂进行了研究，发现此催化剂在助催化剂磷、锆、锌、钾等的作用下对丙二醇的低温氧化脱氢具有很高的活性，可以得到较好的丙酮醛的收率，并且产物中的甲醛、乙醛副产物的量比较低；经过对Ag-P催化剂上反应条件的考察，发现当温度为300℃、氧醇比1.7：1、空速6000h~(-1)、丙二醇浓度为70wt%时，丙二醇的转化率为90%，丙酮醛的选择性为45%。

The results indicated isoprene was soon consumed under the condition of excess ozone. During the reaction, the major carbonyl products formed were methyl vinyl ketone, methacrolein, methylglyoxal, and formaldehyde. Formic acid, CO and CO2 were also among the products.

在反应温度(294±2)K，压力为1.01×10^5Pa空气，O3过量的条件下，异戊二烯很快反应完全，反应中生成的羰基产物主要包括甲基丙烯醛、甲基乙烯基酮、丙酮醛和甲醛；产物中还包括甲酸、一氧化碳和二氧化碳。

Then with V∶V=11 9∶1 0,and by bubbling of air at 65-70 ℃ for 5-8 h,pyruvaldehyde was produced in 59 6% yield.

丙酮醛的总收率达 37 8%。n∶n∶n(1，2 丙二醇)=1 0∶4 0∶(1 5～ 2 5 )，以水为溶剂，在 6 0～ 70℃间歇通入氮气 1 5h ，边加原料边蒸馏，制得产率为5 0 %的丙酮醛。

The yield of pyruvaldehyde in glucose/glycine system (181□g/100ml)was3.6 folds that of galactose/glycine system (50□g/100ml)at 48 hr,We also founded that higher tmeperature promoted the change of pH, which in turn effect more significantly on Maillard reaction.

在丙酮醛产量方面，45°C组葡萄系统在6084小时后才开始产生且量较少；而60°C组葡萄糖系统其产量於48小时达至最高（181□g/100ml），此时丙酮醛的产量为乳糖组（50□g/100ml ）的3.6倍，之后有下降的趋势，其中浓度的效应较不明显。

Hydrothermal reactions makes water a Bronsted base-acid and act as an effective catalyst and the metal ions represent Lewis base character. The conversion process occurs in a very complex network of parallel, consecutive and equilibrium reactions, and the last step being the catalyzed Cannizzaro-type reaction of pyruvaldehyde to lactic acid.

nsted酸碱并具有一定的催化作用，金属离子在水热催化降解丙酮醛生成乳酸中表现出Lewis碱的特性，能与丙酮醛生成金属复合物，最终生成乳酸，此反应过程符合Cannizzaro反应特性。

Now, however, all children continue in "comprehensive" schools, and the eleven-plus determines which courses of study the child will follow.

然而现在，所有的孩子都要在综合学校继续学习，所以这次考试只是决定他们将要学习哪些课程。

Cultivatable land , and led to a general recognition that development must not be carried at the cost of agriculture .

城区的迅速扩大在很多情况下侵占了宝贵的可耕地，使人们普遍认识到发展不能以牺牲农业为代价。