Effect of alkalinity variation in gel composition developed for hierarchical ZSM-5 growth: conversion of ZSM-5 to mordenite

In the synthesis of mesoporous hierarchical material based on MFI zeolite in the presence of mesoporogen agents, it was revealed that variations in alkalinity and Na2O/SiO2 ratios lead to cardinal changes in the structure of the zeolite. Although the original composition was designed to synthesize MFI in the presence of a specific organic SDA agent, a MOR phase appeared, very poor in Al. Since the synthetic mixtures used do not have a sufficient amount of Al for the synthesis of MOR in the solution, the Si/Al ratio of the obtained MOR (10) phase differs significantly from the typical one (5). A series of samples were obtained, starting with MFI, through MFI/MOR mixtures, completely MOR phases and finally amorphous mesoporous material. The molar ratio of Na2O/SiO2 dictates the type of zeolite structure, which makes it clear that the specific structure of the zeolite (MOR) will be formed regardless of the use of the organic SDA agent intended for the growth of another zeolite (MFI).

Keywords: mordenite, ZSM-5, hierarchical, mesoporosity, lamellar.