*3.2. Catalyst Characterisation*

The bulk Ga loading was determined by elemental analysis using a Thermofisher iCAP 7000 ICP-OES (Thermofisher, UK). Identification of crystalline phases was performed using a Bruker D8 Advance powder X-ray diffractometer (Bruker, UK) with Cu Kα radiation for angles between 2θ = 10–80◦ with a step size of 0.04◦. Volume averaged particle sizes were estimated from the Scherrer equation using the peak width of characteristic HZSM-5 and Ga2O3 reflections at 2θ = 14.8◦ and 35.2◦ respectively. Surface areas, pore size distributions and mesopore volumes were determined by N2 porosimetry using a Quantasorb Nova 4000 e porosimeter and Novawin 11.03 software (Quantachrome, UK). Samples were outgassed in vacuo at 300 ◦C for 18 h according to Quantachrome recommendations for microporous zeolites prior to analysis, with specific surface areas calculated by applying the Brunauer–Emmet–Teller (BET) model over the range P/P0 = 0.02–0.07 of the adsorption isotherm. Micropore volumes were determined using the t-plot method developed by Lippens and de Boer over the range P/P0 = 0.2–0.5. X-ray photoelectron spectroscopy (XPS) measurements were performed using a Kratos Axis HSi photoelectron spectrometer (Kratos Analytical, UK) equipped with a charge neutraliser and a monochromated Al Kα X-ray source (hν = 1486.7 eV). Spectra were recorded using

an analyser pass energy of 20 eV and X-ray power of 225 W at a normal emission. Spectral fitting was performed using CasaXPS version 2.3.14 (Casa Software Ltd, UK), with binding energies corrected to the C 1s peak at 284.6 eV; high resolution C and O 1s, Ga, Al and Si 2p XP spectra fitted using a common Gaussian/Lorentzian line shape. Spectra were Shirley background-subtracted and surface compositions quantified by application of element- and instrument-specific response factors. Errors in surface composition were estimated by varying the background subtraction procedure across reasonable limits and re-calculating fits. The carbon content of spent catalysts was measured using a Thermo Scientific Flash 2000 organic elemental analyser (Thermofisher, UK) calibrated to sulfanilamide, fitted with a Cu/CuO CHNS quartz tube and a thermal conductivity detector. Samples were prepared by adding ~10 mg catalyst and ~2 mg V2O5 to tin crucibles.

Acid site loadings and strength were determined by n-propylamine (Sigma Aldrich, UK, ≥99%) temperature-programmed reaction spectroscopy (TPRS) using a Mettler Toledo TGA/DSC 2 STARe system (Mettler Toledo, UK) connected to a Pfei ffer Vacuum ThermoStar GSD 301 T3 (Pfei ffer, UK) benchtop mass spectrometer (MS). Propylamine adsorption was performed by adding liquid n-propylamine to pre-weighed samples (1 mL per 20 mg) and placing in an alumina crucible. Excess physisorbed propylamine was removed by drying in vacuo at 30 ◦C for 1 h prior to analysis. Samples were heated in the thermogravimetric analyser (TGA) from 40 ◦C to 800 ◦C at a ramp rate of 10 ◦C.min−<sup>1</sup> under flowing N2 (40 mL·min−1), with evolved gases analysed by MS to monitor reactively formed propene. Lewis/Brønsted character was determined by di ffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of samples following pyridine adsorption over diluted samples (10 wt% in KBr). Excess physisorbed pyridine was removed in vacuo at 30 ◦C overnight prior to room temperature measurement using a Nicolet Avatar 370 MCT (Thermofisher, UK) with Smart Collector accessory and liquid nitrogen cooled mercury cadmium telluride (MCT-A) detector. DRIFTS spectra were background-subtracted, and the ratio of the transmitted intensities of the 1450 cm<sup>−</sup><sup>1</sup> and 1540 cm<sup>−</sup><sup>1</sup> peaks used to quantify the ratio between Lewis and Brønsted acid sites.
