Golden seaweed tides from beach inundations as a valuable sustainable fuel resource: Fast pyrolysis characteristics, product distribution and pathway study on Sargassum horneri based on model compounds

This study investigates the pyrolysis characteristics and product distribution in the individual pyrolysis of Sargassum horneri (S. horneri) golden seaweed tide components (cellulose, protein and polysaccharide model compounds) and how the primary components lead to the observed product selectivity to explore their application as feedstocks for bio-oil production. The thermogravimetric analysis (DTG) curve of S. horneri was fitted by single pyrolysis curves of cellulose, protein and polysaccharide, which verified the feasibility of the selected model compounds. A higher heating rate significantly enhances the devolatilization performance of S. horneri and its main pseudocomponents. The fast pyrolysis of protein involves random cleavage of the main chain to form diketopiperazines (DKPs), and the side group will undergo cross-linking, cyclization, dehydroaromatization and other reactions to form amide/amines/nitriles, esters, hydrocarbons and N-heterocyclic compounds in particular. The fast pyrolysis of cellulose involves dehydration and 1,4-glycosidic bond-cleavage reactions as well as further rearrangement of intramolecular structures to form the intermediate product levoglucosan, secondary decomposition of levoglucosan to form aldehydes and ketones and rearrangement of intramolecular structures to form furan and its derivatives. The fast pyrolysis of polysaccharide involves depolymerization, dehydration, decarboxylation, decarbonylation and scission and condensation reactions to form lower molecular weight products, such as furfural, carbon dioxide, ketoesters and hydrocarbons. The results also indicate that the three main model compounds of S. horneri each exert a different influence on the product distribution under high-temperature pyrolysis.