Light alkene production by cracking Picochlorum oculatum microalgae using aluminosilicate catalysts

Abstract

Microalgae are increasingly viewed as a sustainable potential resource of chemicals and biologicals. The production of light alkenes (C2-C4 olefins), a major precursor to plastics and other value-added chemicals currently produced from fossil fuels, was studied by catalytically cracking marine microalgae Picochlorum oculatum. The process was studied in the temperature range of 400–650 °C using two aluminosilicate catalysts; (1) commercial Si/Al at catalyst-to-algae mass ratios of zero, 1:1, 5:1, 10:1, and 20:1; and (2) H-β zeolite at a catalyst-to-algae mass ratio of 10:1. Ethene was obtained as the most significant light olefin product followed by propene and butenes as a result of the selectivity of the Si/Al catalyst towards ethene formation. The total olefin yield rose with increasing temperature, as cracking of cellular macromolecules intensified. However, olefin formation started to level off above 550 °C. The total olefin yield also rose with increasing catalyst-to-algae mass ratio, as a result of the presence of more catalytic reaction sites, but the impact lessened at high ratios. A maximum ethene yield (7.3%) was achieved using Si/Al at a catalyst-to-algae mass ratio of 20:1, whereas a maximum propene yield (5.1%) was obtained using H-β zeolite at a catalyst-to-algae ratio of 10:1. The study provided a more effective catalyst for producing light olefins, compared to previous reports, as the maximum total olefin yields of 10.3% and 12.3% with Si/Al (20:1 ratio) and H-β zeolite (10:1 ratio), respectively, exceeded the literature reported yield by 34% and 60%, respectively.