Selective production of levulinic acid from furfuryl alcohol over acid-modified zeolite catalysts

Commercial zeolites (Na-ZSM-5, NH 4 -βeta, and Na-mordenite) were protonated, and sulfonic-acid functionalized through microwave-assisted methods to be applied as acid catalysts for the selective production of levulinic acid from furfuryl alcohol using acetone-water mixture as greener solvent. Sulfonated zeolites enhanced levulinic acid formation due to their higher amount of more accessible BrØnsted acid sites. The different zeolite structure of the catalysts clearly affected the accessibility of the reagents to the acid sites, especially for the one-dimensional H-mordenite catalyst, which showed null selectivity to levulinic acid. Interestingly, this effect was in part overcome by the sulfonic-acid functionalization of mordenite increasing considerably its selectivity to levulinic acid up to 40 %. This means that sulfonation mainly occurred on the external zeolite surface. Sulfonated βeta catalyst showed the highest selectivity to levulinic acid (76 %) for a complete conversion while H-βeta had higher reuse stability since deactivating products adsorbed during reaction can be eliminated by calcination. • Sulfonated zeolites led to higher selectivity to levulinic acid than H-zeolites. • The highest yield to levulinic acid was achieved with sulfonated Beta zeolite (76 %). • The zeolite structure affected the accessibility of the reagents to the acid sites. • Sulfonic-acid functionalization of external mordenite surface improved its accessibility.