Catalytic upgrading of renewable levulinic acid to ethyl levulinate biodiesel using dodecatungstophosphoric acid supported on desilicated H-ZSM-5 as catalyst

•Esterification of renewable levulinic acid (LA) to ethyl levulinate (EL) was performed.•Desilicated ZSM-5 (DH-ZSM-5) is used for esterification probably for first time.•15% dodecatungstophosphoric acid (DTPA) on DH-ZSM-597 is an optimum robust catalyst.•15% DTPA/DH-ZSM-597 exhibited maximum LA conv. of 94% with 100% EL sel.•Pseudo homogeneous kinetic model is proposed with activation energy 29.35 kJ mol−1.

Levulinic acid (LA) is considered as a renewable platform chemical and can be used for the synthesis of variety of important fuels and chemicals. In particular, its esterification with ethanol produces ethyl levulinate (EL) would be green process, as it can be used as diesel miscible biofuel (DMB), preventing global warming by decreasing atmospheric CO2.This study explores the use of modified H-ZSM-5 by desilication viz.; DH-ZSM-5 and dodecatungstophosphoric acid (DTPA) loaded on DH-ZSM-5 for esterification of LA with ethanol aiming to EL. Different degree of desilication of H-ZSM-5 was performed by using aq. NaOH (0.2–1.5 M) at 338 K for 30 min and then DTPA was loaded on these desilicated H-ZSM-5 (DH-ZSM-5) support. H-ZSM-5, DH-ZSM-5 and DTPA on these DH-ZSM-5 samples were characterized by powder X-ray diffraction (XRD), N2 adsorption–desorption, pyridine chemisorbed IR spectroscopy, Temperature Programmed Ammonia Desorption (TPAD). The increase in conversion of levulinic acid was observed from 28% to 94% with increase of DTPA loading from 0% to 15%. The increased LA conversion may be due to increase in total acidity from 43.14% to 84.31%.The use of DH-ZSM-5 as support for deposition of DTPA may be reported for the first time. The present work also extended to optimize process parameters such as DTPA loading on DH-ZSM-5, catalyst to LA ratio, LA to ethanol molar ratio, speed of agitation, particle size reaction temperature and catalyst reusability. Kinetic study based on pseudo-homogeneous (P-H) model is also presented. The experimental results follow second order kinetics.

Graphical abstract15% (w/w) DTPA/DH-ZSM-597 was found to be an optimum catalyst with 94% levulinic acid (LA) conversion and 100% ethyl levulinate selectivity at 1:8 LA to ethanol molar ratio, 0.25 catalyst to LA ratio, 351 K reaction temperature and 4 h reaction time.Figure optionsDownload full-size imageDownload high-quality image (58 K)Download as PowerPoint slide