Structural characterisation and optimisation of acid-treated montmorillonite and high-porosity silica supports for ZnCl2 alkylation catalysts

The effect of acid treatment of montmorillonite clay on its activity as a support for ZnCl2 alkylation catalyst is examined. Maximum activity is associated with long acid treatment times. Structural characterisation, using X-ray diffraction (XRD), 29Si magic-angle-spinning nuclear magnetic resonance (MASNMR) and elemental analysis, suggests that there is little residual clay structure in the most active supports. A selection of commercially available high-porosity silicas are shown to be more active supports than the acid clays under study. Porosimetry measurements indicate that the presence of mesopores may be an important requirement for an effective ZnCl2 catalyst support.