Process for preparing ZSM-5, large pore mordenite and ZSM-35

A process for preparing porous crystalline aluminosilicates said process consisting of the steps of:

• (a) bringing into contact, in an aqueous environment and in the absence of organics, ammonia and ammoniacal substances, sodium silicate with an aluminum derivative at a molar SiO.sub.2 /Al.sub.2 O.sub.3 ratio greater than or equal to 8, in the presence of one or more alkaline hydroxides at a molar Me.sup.+ /SiO.sub.2 ratio greater than 0.6, where Me.sup.+ represents the alkaline metal or metals, and in the presence of a mineralizing agent selected from the group consisting of sodium sulphate, potassium sulphate, sodium phosphate, potassium phosphate, sodium chloride and potassium chloride, and
• (b) conducting the reaction at a temperature between 20.degree. and 100.degree. C. while controlling the molar OH.sup.- /SiO.sub.2 ratio of the reaction mixture between 0.01 and 0.8, the resulting mixture being crystallized at said molar ratio of OH.sup.- /Si.sub.2 in a closed environment for a period of between several hours and 40 days at a temperature between 100.degree. and 200.degree. C.