Impact of Hierarchization on the Textural Properties of MCM‐22 Based Zeolites

The impact of zeolite hierarchization is often highlighted in terms of increased mesopore volume or specific surface area and preservation of micropore volume. Yet, although these targets may be achieved, the accessibility to certain micropores might be negatively affected during hierarchization. A set of hierarchical MCM-22 based materials is prepared based on desilication treatments of MCM-22, of the layered precursor MCM-22(P) and of the hexadecyltrimethylammonium bromide (CTAB) swollen precursor swMCM-22(P), and by the pillaring of swMCM-22(P) leading to MCM-36. A new methodology is presented based on comparing the micropore volume of pristine materials with their n-nonane retaining counterparts. A definition of the accessible micropore volume fraction is given, which relates to the amount of surface 12-MR cups. This approach hence allows quantifying which type of microporosity is preferentially destroyed during hierarchization treatments of MCM-22. Besides comparing the development of mesoporosity, specific surface area, and the evolution of micropore volume during hierarchization treatments, the accessible micropore volume fraction allows for a distinct definition of the hierarchization quality for MCM-22 based materials. Despite an important increase in interlayer-mesopore volume and specific surface area for MCM-36, the accessible micropore volume fraction is found to be just 3% higher than for MCM-22.