Hydrothermal liquefaction of green macroalgae Cladophora glomerata: Effect of functional groups on the catalytic performance of graphene oxide/polyurethane composite

Abstract

This study highlights the challenges and opportunities of Hydrothermal Liquefaction (HTL) of Cladophora glomerata. It suggests functionalized graphene oxide/polyurethane (F-GO-PU) composite as the promising metal-free catalysts for sustainable algae upgrading. The catalysts contained three types of functional groups, including methyl (-CH3), vinyl (-CH=CH2), and amine (-NH2), and were completely analyzed by FTIR, XRD, and SEM-EDS in terms of functional groups, crystalline structure, morphology, and surface elemental distribution, respectively. The results showed that F-GO-PU catalysts efficiently suppressed side reactions that would generate non-desired chemicals. Functionalization with vinyl increased the yield of bio-crude oil by about 54% and showed high selectivity for hydrocarbons with a yield of 15.66 wt%. This catalytic activity was due to the existence of stable and accessible Brønsted acid sites plus the hybrid structure of the composite, which enhanced the accommodation of reaction intermediates on the surface of the catalyst. Thus, as-prepared F-GO-PU composites may hold great promise as metal-free active phase catalysts to develop algae transformation reactions.