*3.4. Catalytic Reaction*

The catalytic performance of LTL-type zeolites in glucose dehydration was evaluated under batch conditions, by using a glass pressure tube equipped with threaded bushing (15 mL, pressure rated to 10 bars, Ace Glass, Vineland, NJ, USA) under magnetic stirring. In a typical experiment, 0.15 g of glucose, 0.05 g of catalyst, 1.5 mL of deionized water and 3.5 mL of methyl isobutyl ketone (MIBK) were introduced into the reactor. Reactors were always purged with nitrogen, prior to the catalytic

study in order to minimize side reactions of HMF which decrease its yield. The mixture was heated with a thermostatically controlled oil bath. The reaction was quenched by submerging the reactor in a cool water bath, and the liquid phases were separated, filtered and the analysis of products was performed in both phases by high performance liquid chromatography (HPLC). A JASCO (Easton, MD, USA) instrument equipped with quaternary gradient pump (PU-2089), multiwavelength detector (MD-2015), autosampler (AS-2055), column oven (co-2065) using a Luna C18 reversed-phase column (250 mm × 4.6 mm, 5 μm) and a Rezex ROA-Organic Acid H<sup>+</sup> column (8%, 300 mm × 7.8 mm, 5 μm) (both supplied by Phenomenex (Torrance, CA, USA). Both glucose and fructose were monitored using a refractive index detector for aqueous phase, while 5-HMF production was monitored using a UV detector in both phases. The mobile phases consisted of pure methanol (flow rate 0.5 mL min−1) for the Luna C18, and deionized water (flow rate 0.35 mL min−1) for the Rezex ROA column, being the columns at room temperature and 40 ◦C, respectively.

**Author Contributions:** Experiment: M.J.G.M., N.H.A., S.M.M.; Data Curation: C.G.S., S.M.; Writing-Original Draft Preparation: C.G.S., E.-P.N., P.M.T.; Writing-Review & Editing: C.G.S., S.M., E.-P.N., P.M.T.; Supervision: E.-P.N., P.M.T.; Funding Acquisition: E.-P.N., P.M.T.

**Funding:** This research was funded by the Spanish Ministry of Economy and Competitiveness (RTI2018-94918-B-C44), FEDER (European Union) funds and FRGS (203/PKIMIA/6711642).

**Acknowledgments:** The authors thank the Servicios Centrales de Apoyo a la Investigación at University of Málaga for technical support. C.G.S. acknowledges the University of Málaga for a postdoctoral contract.

**Conflicts of Interest:** The authors declare no conflict of interest.
