Light alkene production by cracking Picochlorum oculatum microalgae using aluminosilicate catalysts

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 degrees 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-beta 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 degrees 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-beta 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-beta zeolite (10: 1 ratio), respectively, exceeded the literature reported yield by 34% and 60%, respectively.