Abstract
The conversion of trimethylenediamine on platinum group metal -Al2O3 catalysts was examined in a stream of water vapor and hydrogen gas. The reaction was carried out over the temperature range of 220° to 410°, at atmospheric pressure. 2-Ethylpyrimidine (P3) and 2-methylpyrimidine (P2) were obtained as the principal products. Rh-Al2O3 and Pt-Rh-Al2O3 catalysts gave the best yield of P3, which was about 50% at the reaction temperature between 330° and 350°. H2O vapor and H2 gas showed a suppressive effect on the cracking and catalyst decay. It was concluded from kinetic studies that the formation of P3 from trimethylenediamine involved the following successive reactions : disproportionation of trimethylenediamine to 3, 3'-diaminodipropylamine and ammonia (reaction 1), deaminocyclization of 3, 3'-diaminodipropylamine to 2-ethylhexahydropyrimidine (reaction 2), dehydrogenation to 2-ethyl-1, 4, 5, 6-tetrahydropyrimidine (reaction 3), and finally dehydrogenation to P3 (reaction 4). N-Propionyltrimethylenediamine was present in equilibrium with 2-ethy1-1, 4, 5, 6-tetrahydropyrimidine. It was concluded that reactions 1 and 4 were ratedetermining steps, and that reactions 2 and 3 were very rapid. The rate of formation of P3 was determined and the predicted values agreed well with the experimental results. It was considered that P2 was formed from 2-methylhexahydropyrimidine produced by demethylaminocyclization of 3, 3'-diaminodipropylamine.
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