Synthesis of di-n-butyl carbonate from n-butanol: Comparison of the direct carboxylation with butanolysis of urea by using recyclable heterogeneous catalysts

The synthesis of di-n-butyl carbonate has been studied starting from n-butanol and either CO2 or urea. A comparison of the two synthetic routes is reported. Several mixed oxides have been synthesized and tested with the aim of finding a catalyst active in mild conditions (T, t), recoverable and reusable. Different strategies to push the reaction toward the formation of the target product (di-n-butylcarbonate) have been applied and adapted to each case. The pervaporation membrane and chemical water traps are compared as techniques for water elimination and equilibrium shift in the direct carboxylation. Among the tested catalysts, 0.03Nb2O5/CeO2 is the best in the case of the direct carboxylation of butanol, whereas 0.5MgO/ZnO results the best in terms of activity and robustness for the alcoholysis of urea.