Study On Clean Synthesis Of Cycolhexyl Methyl Carbamate

In this thesis ,we propose a new approach, which belongs to a clean chemical synthetic process, that cyclohexyl methyl carbamate(MCHC) can be prepared via the reaction between cyclohexyl amine and a green chemical-dimethyl carbonate, and then via the condensation reaction and the following decomposition between MCHC and formaldehyde, dicyclohexylmethane diisocyanate can be synthesized. This work emphasizes the study of the clean catalytic synthetic process of cyclohexyl methyl carbamate.As the commercial pure reagent of MCHC is not available to us, we employ CHsONa as catalyst and produce cyclohexyl methyl carbamate. The pure product of MCHC is obtained by several recrystalizations. MCHC is also produced from cyclohexyl isocyanates. We characterize the product qualitatively by IR, MS and NMR.Catalytic activity of homogeneous catalysts, such as sodium methylate and zinc acetate, has been studied in this reaction. Sodium methylate shows very high catalytic activity for this reaction; the highest yield reaches 93.4%. The yield of MCHC increases with the reaction temperature. The optimum n(cyclohexylamine):n(DMC) ratio under the conditions of reflux and run time of 3hr is 1:7. Zinc acetate also shows activity for this reaction. By orthogonal reaction, the sequence of importance of all factors is obtained as follow: ratio of feed > temperature > run time. The optimum reaction conditions : the temperature is 90 癈, the run time is 9hr and ratio of feed is 1:20. Under these conditions, the yield of MCHC reaches 67.1%.Zinc oxide series heterogeneous catalysts have been prepared , the evaluation of activity have been performed, and the bulk phase of the catalysts have been characterized as well. Fe2O3-ZnO compound oxides catalysts have been prepared by coprecipitation method. The influence of preparation method, reaction temperature,value of cyclohexylamine/DMC and run time on catalytic property has been investigated. At 110C, the highest yield of MCHC on the catalyst is 15.6%. Zinc oxide catalyst within nano-meter scale has been prepared by supercritical technology. Average particle size of ZnO is 30~40nm determined by TEM, and its specific surface area is 20 times higher than those prepared by regular methods. The yield of MCHC on this catalyst is elevated from 23.5% of common ZnO to 34.0%. ZnO inserted ZnO-MMT catalyst has been prepared. Characterization results of specific surface area and XRD certificate that ZnO is partially inserted. The yield of MCHC is 64.6%.ZrO2 catalyst within nano-meter scale has been designed and prepared. The influence of preparation method and calcination temperature on the structure and catalytic property has been studied. The particle size of ZrO2 catalyst prepared by supercritical technology varies from 30nm to 40nm. The yield of MCHC increases from 23.7% of those prepared by regular methods to 38.9%. Thinking of problem of utilization of nano-meter catalyst, supported ZrO2/SiO2 catalysts have been prepared by supercritical technology. The specific surface area of these catalysts increased by 26% compared with those prepared by regularmethods, and the yield of MCHC increased by three times reaching 90.2%. The interaction between ZrO2 and SiO2 is thought to be the main reason for the improvement of the activity of the catalyst. ZrO2/MMT catalyst has been prepared. ZrO2 is successfully inserted into the layers of MMT, and the specific surface area is effectively improved. The yield of MCHC is elevated to 66.6%. The catalytic mechanism of the synthesis of MCHC via cyclohexylamine and DMC on ZrO2 catalyst has been presumpted.