Abstract
The activity of Pd and Rh complex catalysts (Pd(py) 2Cl 2, Rh(py) 3Cl 3, etc.) in the carbonylation of 2,4-dinitrotoluene (DNT) has been investigated, and the effect of ligands, metal oxide and chloride promoters on the conversion of DNT and selectivity of isocyanates has been studied. It was found that these catalysts exhibit very high selectivity for total isocyanates. The intermediate isocyanates formed were characterized by GC-MS techniques. The effects of free pyridine on the activity of both Pd and Rh complex catalysts showed that an optimum ratio of py/metal exists for a given set of conditions. The influence of CO pressure, catalyst concentration, DNT concentration, temperature and contact time on the activity of the Pd(py) 2Cl 2 catalyst was also studied. It was observed that higher CO pressure and catalyst concentration with a shorter contact time are conditions which favour higher selectivity for 2,4-toluene diisocyanate.
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