*3.1. Catalyst Synthesis*

A commercial HZSM-5 (SiO2:Al2O3 = 30, Zeolyst International, CBV 3024E) was first calcined in air at 550 ◦C for 4 h to remove any surface residues. Then 3 g of calcined HZSM-5 was subsequently wet-impregnated with appropriate concentrations of a 20 mL aqueous solution of Ga(NO3)3·xH2O (crystalline, 99.9% trace metals basis, Sigma-Aldrich, UK) to prepare Ga gallium zeolites with nominal loadings of 0.5 wt% (0.005 M), 3 wt% (0.03 M) and 10 wt% (0.1 M). In each case the resulting slurry was stirred for 6 h at ambient temperature, dried overnight at 90 ◦C, and finally calcined at 500 ◦C under static for 4 h. The resulting catalysts were designated xGa/HZSM-5 where x is the nominal Ga loading. Bulk Ga2O3 (≥99.99% trace metals basis, Sigma-Aldrich, UK) was also calcined at 500 ◦C for 4 h as a reference material.
