Method for the synthesis of ZSM-5 zeolite, at atmospheric pressure and at low temperature

摘要

Method for the synthesis of ZSM-5 zeolites at atmospheric pressure, at a temperature preferably from 60 to 100°C wherein:a) an aqueous solution containing a quaternary ammonium compound (OA) is added to a second aqueous solution, containing a Si compound, a Na compound and a potassium halogenide (K Hal.), according to the molar ratios:-Na2O/SiO2 ≥0.20 (preferably from 0.25 to 2);-H2O/SiO2= = from 5 to 100 (preferably from 10 to 50);-K Hal/SiO2 = from 0.03 to 0.50;b) a third aqueous solution, containing A1 sulphate, is added to the mixture obtained according to a);c) to the mixture obtained according to b) an aqueous solution of H2SO4 is added;wherein the molar ratio Y = (QA/SiO2) is from 0.02 to 0.08 and the molar ratio Z = SiO2/Al2O3 is from 25 to 210, said Y ratio and the molar ratio X = OH-/SiO2 being represented by points lying within triangles limited by the following 3 straight lines:A) Y = 0.7 X;B) X = K/Z, wherein K = 4 (K being constant);C) Y = - 2/3 X + 1 - H, wherein the constant H is obtained from the expression: H = 1/2 (45/Z)0,317.