Study On Hydrothermal Liquefaction And Catalytic Hydrogenation Of Large Algae Biomass

At present,the world's energy and environmental issues are becoming increasingly severe,and countries have invested more research into the development of new energy technologies.As a kind of renewable clean energy,biomass energy has gradually gained widespread attention.As a representative of aquatic biomass,algae does not occupy terrestrial resources,has a fast growth rate and has broad development prospects.Many scholars have conducted research on the efficient use of algae biomass energy.In this paper,algae was used as the experimental object,and the hydrothermal liquefaction experiment method was adopted.Based on this,further hydrothermal liquefaction reaction methods were proposed to study and optimize the thermochemical conversion process of algae biomass.Analysis of raw material components is an essential step in hydrothermal liquefaction experiments.In this paper,the large-scale algae,enteromorpha,was used as the experimental object.Before the hydrothermal liquefaction experiment,the necessary industrial analysis and elemental analysis were carried out on the raw material of enteromorpha.In addition,in the hydrothermal liquefaction experiment,including the raw material drying process,the hydrothermal liquefaction reaction process,the product separation process,and the product component analysis process,the operation process is complicated,and various experimental instruments and equipment are also needed,so before the experiment is carried out,it is necessary to have a clear understanding of the experimental steps and instruments.The hydrothermal liquefaction reaction of algae in high temperature and high pressure reactor was studied with stripe moss powder as experimental materials.The reaction conditions including reaction time,reaction temperature and liquid to material ratio(S/A)were discussed.The effect of the distribution,and the addition of different proportions of ethanol as an alcohol-water co-solvent on the bio-oil yield and product composition.The results showed that the optimal reaction conditions for the hydrothermal liquefaction of enteromorpha were: reaction time 45 minutes,reactiontemperature 300°C,liquid to material ratio(S/A)40/4 mL/g and ratio of ethanol in solvent 50%,the bio-oil yield under this condition is 45%,the solid residue yield is5.25%,and the raw material conversion rate is relatively high.In addition,by GC-MS analysis,it was found that the addition of ethanol in the solvent also increased the content of the ester compound in the bio-oil,and the quality of the bio-oil was improved.Based on the above experiments,the experimental idea of two-step hydrothermal liquefaction reaction is proposed.Firstly,the raw materials are reacted at a lower temperature(200°C)for 30 min,and then the temperature is raised to re-react for 30 min under high temperature conditions(300°C).After comparative analysis of the experimental results,it was found that the overall yield of the bio-oil obtained by the two-stage hydrothermal liquefaction was higher than that of the bio-oil obtained under the low-temperature conditions,but slightly lower than the bio-oil yield under the high-temperature conditions.After comparing the two bio-oil products under grading and high-temperature conditions,it was found that the two-stage hydrothermal liquefaction method can reduce the acid substances in the bio-oil and increase the content of ester compounds in the bio-oil,thus the quality of bio-oil has been improved.In addition,the subject also added the catalyst HZSM-5 in the algae hydrothermal liquefaction experiment to study its effect on the hydrothermal liquefaction of enteromorpha in the ethanol-water mixed solvent.In the hydrothermal liquefaction experiment,different doses(10%-30%)of HZSM-5 catalyst were placed to observe the effect on the yield curve of bio-oil.The results showed that when the amount of HZSM-5 catalyst was 15%,the bio-oil yield was the highest at 44.5%,and the bio-oil yield showed a downward trend after continuing to increase the amount of catalyst.However,compared with the absence of catalyst,the overall yield of bio-oil was not improved.Therefore,the bio-oil product components were compared and analyzed.The results show that the presence of catalyst(HZSM-5)can promote the reaction of alcohol with acid compound to form ester,and the acid component in bio-oil is lower,the stability is better,and the quality of the bio-oil is improved.What's more,this study also preliminary studied the effect of hydrogenation on the hydrothermal liquefaction of enteromorpha.In the hydrogenation hydrothermal liquefaction experiment,after the raw material and the solvent were put into the reaction vessel,the hydrogen was passed through a venting valve into the reaction vessel to allow 3 MPa of hydrogen to react at 275 ° C for 45 min.The results show that for the hydrothermal liquefaction of enteromorpha in pure water,the presence of hydrogen can reduce the composition of amide in bio-oil,which is beneficial to the improvement of bio-oil quality;and when the solvent for hydrothermal liquefaction is an ethanol-water mixed solvent,which means ethanol and hydrogen are simultaneously present,the effect of hydrogen is not as obvious as that of ethanol.