Abstract
Hexahydro-2-methylpyrimidine was prepared in a good yield and selectively by gas phase reaction of trimethylenediamine with ethylene glycol. The reaction was carried out over 10 kinds of silica-alumina catalysts within the temperature range of 220-440°. They were Neobead (I), 5% K2O-Neobead (II), 6.8% Cr2O3-Neobead (III), synthetic zeo1ite (IV), 5% K2O-synthetic zeolite (V), natural zeolite (Clinoptilolite, Itaya, Yamagata) (VI), 5% SiO2+95% Al2O3 (VII), 30% SiO2+70% Al2O3 (VIII), 50% SiO2+50% Al2O3 (IX), and 70% SiO2+30% Al2O3 (X). Yield and selectivity of a series of zeolites were higher than that of Neobeads. The yield and selectivity were higher in case of catalysts VII, VIII, IX, and X when SiO2 content was larger. Among all these catalysts, VI gave the best yield of hexahydro-2-methylpyrimidine, which was 65% under the condition of molar ratio of 1 : 3, for feed rate of materials of 1 ml/min, weight of packed catalyst of 30g, and reaction temperature of 315°.
