Synthesis Methods of 4,4′- Diaminodiphenyl Methane

4, 4′-Diaminodiphenyl methane (4, 4′-MDA) as an important chemical in the chemical industry has a wide range of applications. In the polymer field, it can be used as chain extenders, curing agents; in the dye industry, it can be used to prepare the basic yellow O, basic violet 5BN and triarylmethane dye; in the polyurethane industry, it is one of the important raw materials for the preparation of polyurethane (PU). It is because of it has above a wide range of applications, its synthesis method has been one of the focuses of the research at domestic and foreign. Using aniline, formaldehyde and benzotriazole as raw materials, the mild reaction conditions, short time; selective reaction generates only 4, 4′-MDA, no 2, 4′-MDA and 2, 2′-MDA isomer generated.But starting materials benzotriazole, and the intermediate N-(1-benzotriazole-methyl) aniline structure is complex, the source does not widely, and the yield is not high, only 58%. Using 4, 4′-dinitro diphenyl methane as the raw material, the method is a typical reaction, a short step, easy to operate, under mild conditions, up to 93% yield; downside is that the higher prices of raw materials used, the complex catalytic system, due to the use of the precious metals as a catalyst, thereby increasing the cost of production, making it subject to certain limitations in the industrial application. Using nitrobenzene and methanol as raw materials, which is an industrial continuous production of it method, raw materials are cheap, and the wide variety of sources, can continue to use the non-completion of the reaction raw materials, and therefore better economic. However, this method also uses a noble metal as the catalyst, so that the production cost increases. In addition there are the byproducts are more difficult to separate liquid acid corrosion equipment more serious. Using aniline and formaldehyde as raw materials, which is the industrial production of 4,4′-MDA most commonly used method. This method has the following advantages: mild reaction conditions, high temperature and high pressure is not required; simple synthetic route, the target product is obtained directly from aniline and formaldehyde; Ingredients simple structure, the wide variety of sources, are commonly used compound; 4)without using a noble metal as catalyst, and to reduce the cost of the industrial production. As the above advantages, this method has been much attention, is the research focus of domestic and foreign and international chemical workers. The catalytic system of this kind of reaction that has a direct and important impact, chemical workers in catalyst research and development devoted a lot of energy, made a series of progress. Overall, the catalyst used can be summarized into two categories: the liquid catalyst and the solid catalyst. With the increasing of social progress and human environmental awareness, green and efficient 4, 4′-MDA Synthesis more and more become the favor of people. Liquid acid catalyst has higher catalytic activity, but make the corrosion of equipment, serious pollution of the environment. Synthesized using a solid catalyst 4, 4′-MDA shows many advantages: low environmental pollution, and the low level of corrosion of the equipment after the completion of the reaction, the catalyst is easily separated from the reaction system, for the cycle of use. Aniline and formaldehyde by the simple and easy to get as the starting materials, environmentally friendly, reusable solid catalyst synthesis 4,4′-MDA is the direction of future research and development and industrial production.