Study On The Mechanism Of Pyrolysis Of Main Model Compounds Of Enteromorpha To Produce Synga

With the development of the economy and society,traditional energy consumption intensifies and environmental pollution becomes increasingly serious.It is imperative to develop and utilize new clean energy.In recent years,"green tide"caused by Enteromorpha prolifera occurs frequently.Enteromorpha prolifera,as a kind of algal biomass,can be transformed into available energy through pyrolysis.Sulfated polysaccharides,glutamic acid,aspartic acid and alanine were used as model compounds of Enteromorpha prolifera.The composition and formation mechanisms of syngas during the pyrolysis of model compounds of Enteromorpha prolifera were analyzed by molecular dynamics simulation.Then,fixed-bed pyrolysis experiments were carried out,using rhamnose,glucuronic acid,aspartic acid,glutamic acid,alanine and Enteromorpha prolifera powder as raw materials.Ni and SPAO-34 catalysts were selected,and a gas chromatograph was used to analyze the syngas obtained from each group of experiments.With rhamnose,glucuronic acid,aspartic acid,glutamic acid and alanine as the model compounds of Enteromorpha prolifera,based on density functional theory（DFT）,the possible paths of H₂and CO production were designed and simulated.The ability of glucuronic acid to produce H₂is equivalent to rhamnose,but the ability of glucuronic acid to produce CO is stronger than rhamnose.The strongest among the three amino acids in terms of their ability to produce H₂is glutamic acid,followed by aspartic and alanine acid.The three amino acids most likely to produce CO are alanine,followed by glutamic acid and aspartic acid.There are six models for pyrolysis simulation,which are sulfated polysaccharides,aspartic acid,glutamic acid,alanine,the mixture of three amino acids,and the mixture of sulfated polysaccharides and amino acids.Sulfated polysaccharides mainly undergo glycoside bond breaking,pyran ring opening,dehydration reaction and C-C bond breaking.Amino acids mainly undergo dehydration reaction,deamination reaction,decarboxylation reaction and R group removal reaction.When sulfated polysaccharides and amino acids are co-pyrolysis,rhamnose and glucuronic acid molecules produced by pyrolysis of sulfated polysaccharides attack each other with amino acids to produce other substances.The content of CO in the syngas obtained from the sulfated polysaccharide model is the highest,followed by CO₂,H₂and CH₄.The syngas obtained by pyrolysis of amino acids and co-pyrolysis of sulfated polysaccharides with amino acids has the highest CO₂content,followed by CO,H₂,and CH₄.The co-pyrolysis of three amino acids shows a synergistic effect in producing H₂.The content of CO₂in the syngas from the co-pyrolysis of sulfated polysaccharides and amino acids increases,while the content of CO decreases.The content of H₂is higher than that of sulfated polysaccharides but lower than that of the co-pyrolysis of three amino acids.Using rhamnose,glucuronic acid,aspartic acid,glutamic acid,alanine and Enteromorpha prolifera powder as experimental materials,Ni and SPAO-34 catalysts were selected for fixed-bed pyrolysis experiments.A gas chromatograph was used to analyze syngas.The content of H₂in the syngas produced by the separate pyrolysis of rhamnose and glucuronic acid is similar（17.75%,17.35%）,and the content of CO in the pyrolysis gas of glucuronic acid（69.19%）is higher than rhamnose（55.08%）.When rhamnose and glucuronic acid are mixed and pyrolyzed,the content of CO in the syngas decreases（69.19%,55.08%→40.32%,41.35%）and the content of CO₂increases（8.22%,2.51%→26.75%,27.6%）.When the mass ratio of rhamnose to glucuronic acid is 1:1.1,there is a strong synergy to increase the H₂content.Among the syngas obtained from the pyrolysis of three amino acids,glutamic acid has the highest content of H₂（24.68%）and alanine has the highest content of CO（44.94%）.During the co-pyrolysis of the three amino acids,it was found that the three had a synergistic effect on the production of H₂.The syngas obtained from the co-pyrolysis of model compounds of polysaccharides and three amino acids has lower CO content（40.32%,41.35%,30.18%→25.69%,26.57%）,higher CO₂content（26.75%,27.6%,36.14%→41.31%,40.62%）,and H₂content between the two.The addition of Ni and SPAO-34 catalysts increased the content of H₂and CO in the syngas.Compared with the syngas obtained from the pyrolysis of Enteromorpha prolifera and model compounds of Enteromorpha prolifera,the H₂content obtained from the pyrolysis of Enteromorpha prolifera is higher and the CO₂content obtained from the pyrolysis of the model compounds is higher.