Study On Product Characteristics And Reaction Pathways Via Hydrothermal Liquefaction To Produce Bio-oil

Exploitation and utilization of renewable energies have become a worldwide concern due to the aggravating environment pollution and widespread energy shortage.Hydrothermal liquefaction(HTL)can be used to generate alternative fuel by directly utilizing wet materials.Transformation of all compositions can be achieved by HTL,which makes the latter a promising technology to produce alternative fuel.The composition of biomass has great influence on the bio-oil generated by HTL.The mechanism for the HTL of biomass is still uncomplete.The present study utilized 3 new types of biomass,i.e.microalgae,macroalgae,and spent coffee grounds,to investigate the reaction mechanism of HTL process in differential reaction conditions,composition of feedstocks.Nannochloropsis sp.,a representative microalgae with high protein content,exhibited the highest oil yields of 54.11% at 320°C,the largest high heat value(HHV)of 37.88 MJ/kg,and the highest energy recovery(ER)of 89.76%.The most dominant components in bio-oil were amides & amines and N-Heterocyclic compounds,which were derived from the acylation and Maillard reaction.Macroalgae Sargassum sp.contains abundant cellulose hemicellulose and lignin compounds,of which the highest oil yield was 9.49% at 340?,the largest HHV 35.23 MJ/kg,and the highest ER 31.72%.Bio-oil primarily contained carbohydrates conversation products.Monosaccharides reacted with amino acids and generated Nheterocyclic compounds.Besides,they also produced cyclic ketones through dehydration and isomerization.Since the aromatic ring structures in lignin were comparably stable,higher temperature maybe required to transfer it into bio-oil.SCG gained the highest oil yield of 32.19% at 340? and 30 min.Highest oil yield was 32.19% at 340?.The largest HHV was 36.60 MJ/kg and the highest ER was 55.60%.Caffeine was most abundant compound in bio-oil.According to products detection results and comparing with HTL researches of other feedstocks,I deduced that there was ring cleavage,decarbonylation,decarboxylation appeared in SCG HTL and generated amides & amines,nitriles and double nitrogen heterocyclic compounds.HTL process was capable to reduce O/C and enhance H/C to improve bio-oil fuel characteristics.Interactions among different biomass compositions,such as acylation,Maillard reaction,esterification,etc.,were key pathways of HTL to generate bio-oil.Besides,during HTL process of low-lipid biomass,interactions among the different components is in favor of the bio-oil yields.