High activity, templated mesoporous SO₄/ZrO₂/HMS catalysts with controlled acid site density for α-pinene isomerisation

Highly active mesoporous SO₄/ZrO₂/HMS (hexagonal mesoroporous silica) solid acid catalysts with tuneable sulphated zirconia (SZ) content have been prepared for the liquid phase isomerisation of α-pinene. The mesoporous HMS framework is preserved during the grafting process as evidenced by the X-ray diffraction (XRD) and porosimetry with all SO₄/ZrO₂/HMS materials possessing average pore-diameters ∼20 Å. XRD confirms the presence of a stabilized tetragonal phase of nanoparticulate ZrO₂, with no evidence for zirconia phase separation or the formation of discrete crystallites, consistent with a uniform and highly dispersed SZ coating. The activity towards α-pinene isomerisation scales linearly with Zr loading, while the specific activities are an order of magnitude greater than attainable by conventional methodologies (∼1 versus 0.08 mol h⁻¹ g Zr⁻¹).