Preparation And Application Of Sargassum Horneri Carbon Based Solid Acid Catalyst

Sargassum horneri,as a kind of dominant macroalgae in Zhejiang coast,has been used in restoring marine ecosystems.However,for mature Sargassum horneri plants,it is important to find suitable applications as they are a form of waste,with causing seawatera eutrophication problem.In recent years,the research for utilization of macroalgae(such as Sargassum horneri)has become a hot topic in the development of marine resources.In this paper,Sargassum Horneri was employed as raw materials to prepare biomass carbon-based solide acid catalyst via hydrothermal carbonization and sulfuric acid sulfonation.Based on the single factor experiments,response surface analysis was used to determine the optimal conditions for the catalyst preparation.Physical and chemical properties were characterized by TG,XRD,N2 sorption,FTIR,SEM and elemental analysis.Besides,the solid acid catalyst was applied in the esterification of oleic acid with methanol and the effect of reaction conditions on esterification yield was studied.The method of life cycle assessment(LCA)was applied to calculate greenhouse gas(GHG)emission of Sargassum Horneri carbon based solid acid catalyst system.The results indicated that:(1)The optimal preparation conditions of Sargassum Horneri carbon based solid acid catalyst were carbonization temperature of 217?,carbonization time of 4.6 h,concentrated sulfuric acid Volume of 15 ml,Sulfonation temperaturethe of 108.5? and Sulfonation time of 2 h.Under this conditions,the surface acidity measured by experiment could reach 1.615 mmol/g.(2)The results of morphology analysis,crystal structure analysis,pore structure analysis and contact angle analysis indicated the existence of amorphous carbon structure,large pore structure and the hydrophilicity of hydrochar,which makes it a good carbon support for solid acid catalysts.The results of elemental analysis and surface functional group analysis indicated the sulfonic acid group was successfully loaded onto the surface of hydrochar.The optimal reaction conditions of esterification obtained by response surface analysis were mass ratio of catalyst to oleic acid of 16.6%,molar ratio of methanol to oleic acid of 7.23:1,reaction temperature of 90? and reaction time of 2.72 h,the esterification yield could reach 96.58% under this conditions.The esterification yield was still above 85% after seven cycles of successive reuse,which indicated that the catalyst stability was excellent.(4)The net GHG emission per kg of catalyst is 20.369 kg CO2-eq.The largest emission source is the indirect GHG emission caused by power consumption in the stage of catalyst preparation,which account for 83.7% of net GHG emission.Thus,reducing power consumption and improving energy efficiency is one of the directions in the future research.In this paper,the preparation and application of carbon based solid acid catalyst has been systematically studied,which broadens the utilization ways of Sargassum Horneri and provides reference for the development of macroalgae.