Synthesis of Allantoin Catalyzed by SO42-/La2O3-SiO2-ZrO2

Abstract

Allantoin was synthesized using glyoxalic acid and urea as raw materials and La₂O₃-promoted solid acid SO₄^2-/SiO₂-ZrO₂ as catalyst. The present research focused on the effects of La₂O₃ doping amount, catalyst dosage, reactant ratio and reaction temperature and time on the yield of allantoin. The optimum condition for reactions is as follows: amount of catalyst, 2.5 g; doping amount of La₂O₃, 0.12 wt %; molar ratio of reactants n_(urea):n_{(glyoxylic acid)} = 4:1; reaction temperature, 75 ºC and reaction time, 5 h. The yield of allantoin at optimum condition was up to 46 %. The melting point determination, infrared spectroscopy and elemental analysis of the product confirmed that the obtained product is allantoin and the analysis indicated that the purity was 98.5 % or above.