Research On The Alcoholysis Of Urea, Nitrile And Amide In Supercritical Alcohol And Alcohol/Water System

With the rapid growth of population, depletion of resources, and the rapid development of industry, the environmental pollution has become more and more serious. The pollution caused by the chemical industry is the main source of today’s environmental pollution. The development of green chemical technology has become an inevitable trend of evelopment of chemical industry.In recent decades, the supercritical fluid technology as the representative of the green chemical technology obtained the rapid development. The supercritical fluids include the supercritical water, the supercritical carbon dioxide, and the supercritical alcohol. Compared with the supercritical water and carbon dioxide, the supercritical alcohol has the excellent mass transfer performance as well as other supercritical fluids. Besides, it also has the three characters, namely,1. For the technology operated at the high temperature and pressure, the supercritical alcohol has the advantages of the mild operating conditions, reducing the corrosion of the equipment, the simple and energy conservation for the product’s purification and separation.2. It has good solubility. In instance, it can be dissolved lignin, cellulose and other biomass resources and polymer materials.3. Supercritical alcohol can be used as reacton medium, and also be used as a reactant in alkylation reaction, which avoid using the toxic alkylation agents. So the supercritical alcohol is widely used in many fields, such as organic synthesis, the waste polymer recycled, the biomass resource, and the preparation of nanoparticles and so on.The esters or ester amine compounds plays an important role in the chemical production and daily life, being used as the medicine intermediate and making the spices,flavors, cometics etc. However, there are much drawback to produce these compounds by the conventional methods, such as adding strong acid as catalyst, easy corrosion reaction equipment, difficult separation of products, and low yield. Based on the advantage of supercritical alcohol, it could-resolve the problems to promote the yield and reduce the reaction time.In the paper, urea, nitrile and amide are used as subjects. And the alcoholysis of urea, phenylacetonitrile, and caprolactam in supercritical alcohol or alcohol/water system is proposed in order to enrich the application of organic synthesis using supercritical alcohol method and to provide the experimental data and the theoretical basis for the chemical industry.The details are given as follows:1. Research on the alcoholysis of urea in supercritical methanol and ethanolThe synthesis of dimethyl carbonate (DMC) from the direct alcoholysis of urea in supercritical methanol system was investigated. The effects of different reaction parameters, such as reaction temperature, reaction time, the molar ratio of methanol/urea, reaction pressure, the volume of reaction solution, the treating reactor and the amount of water on DMC yield were systematically investigated. The-experimental results indicated that the optimal reaction conditions were reaction temperature of538K, time of2h, the molar ratio of methanol/urea of14, and the reactor loading of285μL, respectively. And the DMC yield was98%under the optimal reaction condition. The reaction mechanism of urea in supercritical methanol was proposed. At the same time, the alcoholysis of urea in supercritical ethanol was compared with the alcoholysis of urea in supercritical methanol. The reaction condition, such as CO2(N2or air) loaded into the reactor and metallic oxides on the reaction was further investigated. It suggested that the reactivity of supercritical methanol is better than that of supercritical ethanol. A probable mechanism for alcoholysis of urea in supercritical ethanol was also proposed.2. Research on the phenylacetonitrile in supercritical alcohol with little water systemThe alcoholysis of phenylacetonitrile in supercritical methanol, ethanol and2-propanol with little water system was investigated. The effects of various operating conditions, such as the reaction temperature, the reaction time, the molar ratio of phenylacetonitrile/water/methanol or ethanol on product yield were systematically investigated. The experimental results indicated that the yields of methyl phenylacetate, ethyl phenylacetate, and isopropyl phenylacetate are70%,80%and31%, respectively. The solubility parameter of ethanol was close to phenylacetonitrile, but was greatly less than methanol which leaded to the yield of ethyl phenylacetate being higher than that of methyl phenylacetate. The low alkoxide ion concentration in supercritical2-propanol resulted in the low yield of isopropyl phenylacetate. At the same time, a plausible mechanism was proposed for phenylacetonitrile in supercritical methanol, ethanol and2-propanol with little water system.3. Research on the caprolactam in supercritical ethanol with waterThe reaction of caprolactam in supercritical alcohol with water system was investigated. The main product was ethyl-6-aminohexanoate. The effects of the reaction temperature, reaction time, molar ratio of reactant/water and additives on the yields of ethyl-6-aminohexanoate were systematically investigated. The optimal yield (98%) was obtained at573K,2.5h, molar ration of caprolactam/water/alcohol of1:56:28and SnCl2as additive. At the same time, the reaction between caprolactam and alcohol was proposed by a lumped kinetic equation as a second-order reaction in supercritical ethanol with water system, and the active energy was obtained according to the Arrhenius equation under the acid and base condition. Based on the experimental results, the reaction mechanism of caprolactam in supercritical ethanol with water was proposed.