Oxygenated biofuels: synthesis of fatty acid solketal esters with a mixture of sulfonated silica and (Bu4N)(BF4) catalyst - Barbosa, Sandro L.; Lima, Pamela Cristina; Santos, Wallans Torres Pio dos; Klein, Stanlei Ivair; Clososki, Giuliano Cesar; Caires, Franco Jazon (Catalysis Communications, 2019)