PURPOSE: To satisfactorily remove an org. compd. contg. nitrogen from crystalline metallosilicate under a mild temp. condition without disintegrating the crystals by allowing lower alcohol to coexist with gas contg. oxygen when the metallosilicate is calcined in the presence of the gas.

CONSTITUTION: When crystalline metallosilicate contg. a metallic element such as Al as a constituent component in the crystal skeleton in ≥5, preferably ≥20 atomic ratio of Si to the metal is calcined in the presence of gas contg. molecular oxygen to remove an org. compd. contg. nitrogen such as amine or quat. ammonium salt added at the time of hydrothermal synthesis, 1-4C lower alcohol is allowed to coexist with the gas contg. oxygen and the metallosilicate is calcined at <500°C, preferably 300-470°C to remove the org. compd. contg. nitrogen. The amt. of the lower alcohol added is <6vol.%, preferably ≤4vol.% is the case of methanol.