*2.1. Materials*

Mesoporous aluminosilicate Al-MCM-41 support (3–4% Al2O3) was supplied by ACS Material (Pasadena, CA, US). Guaiacol (2-methoxyphenol) purchased from Merk (Kenilworth, NJ, US) was used as the model compound for the HDO study. Metal precursors (palladium(II) nitrate, cobalt(II) nitrate (99.999%), and iron(III) nitrate (99.95%)) were purchased from Aldrich (St. Louis, MO, US).
