Process for producing pentacyl-type crystalline zeolites and a process for producing ε-caprolactam using the same

A process for producing a pentacyl-type crystalline zeolite, comprising the steps of:

• (i) preparing a mixture of a silicon compound, water and tetrapropyl ammonium hydroxide,
• (ii) conducting a hydrothermal reaction of the mixture to obtain a reaction mixture containing zeolite crystals,
• (iii) separating the zeolite crystals from the reaction mixture to collect a remaining solution,
• (iv) calcining the resulting zeolite crystals,
• (v) treating the calcined zeolite crystals with an aqueous solution containing a compound selected from the group consisting of ammonia and ammonium salts to obtain a pentacyl-type crystalline zeolite, and
• (vi) recycling the solution collected in step (iii) to the mixture preparing step (i),
• wherein a molar-ratio composition of the mixture prepared in step (i) is adjusted so that the molar ratio of the hydroxide ion to silicon falls within a range of from about 0.1 to about 0.4;
• that a molar ratio of potassium to silicon is about 0.1 or less;
• and that an atomic ratio of silicon to the total of aluminum, gallium, boron, titanium and zinc is about 500 or more.