4,4′-Methylenebiscyclohexylamine (H12MDA) is a kind of special amine. Its downstream products include MDI, high-quality epoxy curing agent, polyamide materials, elastomers, fibers, foamed plastics, etc. The fields of high-tech materials such as optics, liquid crystal display, and optical fiber communication have broad application prospects. At present, only a few companies in the world, such as the United States, Germany and China, have the industrialized production technology of H12MDA, all of which require the use of precious metal catalysts, the addition of lye in the production process, and the high reaction temperature and pressure.

MDA catalytic hydrogenation green preparation H12MDA technology uses 4,4′-methylene diphenylamine (MDA) as raw material, adopts self-developed new high-efficiency special catalyst, does not add high-polluting liquid caustic soda, and converts it into H12MDA, a new low-cost green process route.

According to Wang Liguo, a researcher at the Institute of Process Engineering, Chinese Academy of Sciences, in view of the harsh reaction conditions, complex reaction system, low product selectivity in traditional processes, and the need to add lye to tetrahydrofuran solvent to suppress the side reactions of deamination and condensation, their research team innovatively proposed The preparation technology of low-load Ru-based catalyst on nitrogen-containing carrier forms a metal-N coordination center, provides abundant basic sites on the catalyst surface, realizes effective metal immobilization, and prevents particle agglomeration. The catalyst has the characteristics of high selectivity, high activity, high stability and easy to scale up preparation, and can effectively suppress by-products in the reaction process.

Relying on the laboratory’s small-scale technology, Shaanxi Coal Technology Center built a 100-ton MDA catalytic hydrogenation green preparation H12MDA pilot plant in Weinan, Shaanxi, which opened up the process flow and realized long-term safe and stable operation. And optimize the technological process, adjust the material ratio, and clarify the optimal reaction conditions, which provides a basis for the subsequent industrialized devices. The MDA conversion rate reached 100% and the H12MDA yield was 96.5% after a 72-hour on-site assessment organized by experts from the Shaanxi Petrochemical Federation. The reliability and stability of the technology have been verified.

Experts believe that the technology does not use lye, reduces the discharge of “three wastes”, mild reaction conditions, and has the characteristics of green environmental protection and higher safety. It is recommended to speed up its industrial application.

Song Shuangtian, chairman of Shaanxi Coal Technology Center Co., Ltd., said that with the wide application of new products such as high-end polyurethane and high-quality curing agents, the demand for aromatic amines and alicyclic amines will continue to grow, and green synthesis technology has become a development trend. The next step will be to increase the industrialization promotion of H12MDA green preparation technology, and with this technology as the core, continue to expand the upstream and downstream industrial chain of special amine-high-end isocyanate-polyurethane new materials, increase the added value of products, and break the monopoly of foreign technologies and products.