Bayer centre targets isocyanate process advances

Leverkusen, Germany – Bayer MaterialScience has commissioned a new Euro5-million technical center for the development of isocyanate production processes at Chempark Dormagen. The facility is focused on hydrogenation technology for the production of precursors to diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI).

All global research activities related to the production of aromatic isocyanates have now been pooled in the new hydrogenation technical center,” according to Dr. Joachim Wolff, head of the polyurethanes business and member of the BMS executive committee.

“The associated efficiency gains in the research and optimization of the production processes will help to further expand our global technological leadership,” said Wolff.

MDI is based on benzene, which is first nitrated into nitrobenzene and then hydrogenated to produce aniline. An additional step then converts the aniline to diphenylmethane diamine, the direct precursor to MDI. A catalyst is used to produce aniline from nitrobenzene and hydrogen gas.

With the conventional isothermic process, which is performed at a constant temperature, the substantial heat generated during the reaction must be dissipated using heat transfer oils. The reaction takes place inside a reactor block, in which many thousands of tubes containing the catalyst have been welded together. Finally, the aniline must be painstakingly purified of byproducts before it can be used further.

The adiabatic variant developed by BMS eliminates the need for heat transfer and enables a substantial gain in efficiency. Here the reaction takes place in a large steel vessel, in which the catalyst is placed on a grating. The heat of reaction is dissipated together with the gas flow, eliminating the need for the circulating oil loop. In addition, the product is also of significantly higher purity.

The technology is already in use at Bayer’s facility in Shanghai, China, which has an annual production capacity of 350 kilotonnes.

“The conventional process would have been too complex and too expensive for a facility of this size,” said Dr. Thorsten Dreier, who heads the isocyanate research department at polyurethane production.

The researchers plan to concentrate on the further optimization of both process variants at the new technical center. Other focal points will be researching and improving the hydrogenation of dinitrotoluene to obtain toluene diamine, the direct precursor to TDI, and also the Deacon process for the oxidation of hydrogen chloride.