PURPOSE: To select reaction conditions from a wide range and to reduce the cost of the compd. by bringing a carboxylayted cyclic nitrogen-contg. compd. into contact with mixed metal oxide catalysts under effective conditions.

CONSTITUTION: For example, the carboxylayted cyclic nitrogen-contg. compd., such as bis(methyl 2-piperadinoethyl)carbonate, is subjected to the decarboxylation reaction in a liquid diluent, such as benzene or toluene, or a gaseous diluent, such as nitrogen or methane, preferably under 100 to 2500 mmHg and at 225 to 350°C in the presence of the mixed metal oxide catalysts consisting of ≥1 kinds of metal oxides of group IA, group IIA, group IIIB, group IVB, etc., (MgO-Al2O3, MgO-SiO2, etc., having a surface area of 50 m2/gm and associating with a supporting object, such as alumina material).