Porous clay heterostructures (PCHs) from Al13-intercalated and Al13-pillared montmorillonites: Properties and heptane hydro-isomerization catalytic activity

Abstract

The conventional method of synthesizing porous clay heterostructures (PCHs) is based on the use of cetyltrimethylammonium cations, amines (as a co-surfactant) and a silica source. In the present study, we report the preparation of PCH materials from Al13-intercalated montmorillonite and its pillared derivatives using one directing template (dodecylamine) and a silica source. This method allowed us to reduce the use of the organic template and to incorporate the aluminum species directly into the silica framework intercalated between the clay sheets in one step. The dodecylamine template was removed by calcination at 550°C in air. The PCH material prepared from the Al13-intercalated clay exhibited a higher surface area, mesopore volume and acidity, as well as strong Brønsted and Lewis acid sites. However, the use of pillared clays did not lead to the formation of PCH material due to the strong interaction between the alumina species and the clay sheets, which hindered their exchange with dodecylamine, as indicated by XRD and 29Si and 27Al solid-state NMR techniques. The hydro-isomerization reaction of heptane was tested on the differently prepared PCHs with a conversion of 60% and isomer yield of 50% at 350°C.