Synthesis of ethyl levulinate from furfuryl alcohol using H-ZSM-5 dealuminated with sulfuric acid as a heterogeneous catalyst

In this study, the effect of dealumination of H-ZSM-5 zeolite on the concentration acid sites was analyzed to optimize its catalytic performance in the conversion of furfuryl alcohol (FAL) to ethyl levulinate (EL). The integrity of the zeolites after dealumination was examined using complementary X-ray diffraction (XRD), nitrogen adsorption, and high-resolution transmission electron microscopy (HR-TEM) analyses, while the concentration and nature of the acid sites and Al coordination were analyzed using a combination of FT-IR spectroscopy with pyridine adsorption and 27 Al MAS NMR spectroscopy. Increasing the severity of acid treatment results in a gradual decrease in the concentration of sites and the formation of perturbed and dislocated Al atoms from the zeolite framework, present as Al-OH groups, Lewis acid sites, and octahedrally coordinated Al, only partially removed from the dealuminated zeolite. The reduced concentration of acid sites achieved through dealumination enables a significantly more efficient reaction, resulting in an almost fourfold increase in EL yield compared to the non-dealuminated zeolite. Tuning the density of acid sites and reaction parameters allowed for precise control over both conversion and selectivity. The optimal combination of reaction conditions and ZSM-5 dealumination resulted in complete conversion of FAL and an EL yield of 98%.