Microwave-enhanced catalytic conversion of fatty acid ester to olefins by Na-ZSM-5

The bio-based production of essential chemicals is important for the sustainability of the chemical industry. Here, we demonstrate efficient olefin production from methyl oleate using Na substituted ZSM-5 (Na-ZSM-5) and microwave irradiation. Na-ZSM-5 exhibits superior microwave heating properties compared to H-ZSM-5 and other zeolites. It was more effective in converting methyl oleate to olefins such as ethylene and propylene than H-ZSM-5 or Y zeolites. Microwave irradiation promoted the conversion efficiency of methyl oleate by Na-ZSM-5, achieving an olefin yield over four times higher than that obtained with conventional heating (CH) using an electric furnace. Meanwhile, the aromatization to benzene, toluene and xylene (BTX) was suppressed using Na-ZSM-5, which was attributed to the removal of strong acid sites. In addition, in situ microwave XRD revealed that microwaves promoted temperature-dependent structural changes in Na-ZSM-5 at lower temperatures than CH, suggesting that microwaves form localized high temperatures in the zeolite. These localized high temperatures effectively enhance olefin production via microwave irradiation.