Preparation Of Mesoporous Solid Base Catalyst And Its Application In Biodiesel Production From Microalgae

As a renewable liquid fuel,biodiesel has received worldwide attention due to its environmental friendly,renewable and biodegradable properties.There are some advantages for microalgae as the raw materials,such as short growth cycle,high biomass production and high oil content.The traditional microalgae biodiesel production process includes two steps:oil extraction and transesterification under homogeneous catalyst.The two-step method for biodiesel production has the disadvantages of long time-consuming and high consumption of organic solvents.The homogenous catalysts are difficult to be separated from the product and the purification of the product requires a large amount of water,resulting in the emission of waste water.In order to produce biodiesel efficiently,we dedicated to preparing a mesoporous solid base catalyst and applying it on biodiesel production from Chlorella vulgaris biomass by a one-step method.Three mesoporous solid base catalysts were synthesized in this study.The effect on conversion efficiency of catalyst preparation conditions was systematically investigated.XRD,BET,FT-IR,SEM,TGA and VSM methods were used to characterize the structure and properties of the prepared catalysts.At the same time,the effects on conversion efficiency of in-situ transesterification parameters were systematically studied to optimize the biodiesel production technology.The main conclusions are as follows:(1)The fatty acid methyl esters(FAME)composition of biodiesel produced by chlorella oil was analyzed by gas chromatography-mass spectrometry.The results showed that the main components of FAME were:methyl hexadecanoate,methyl palmitolea,methyl 10-undecenoate,methyl hexadecadienoate,methyl hexadecatrienoate,methyl stearate,methyl oleate,methyl linoleate,methyl linolenate and methyl eicosapentaenoate,in which saturated fatty acids account for 26.1%of the total,and unsaturated fatty acids account for 73.9%of the total.(2)KOH/CeO2 was prepared by impregnation method and used to produce biodiesel from Chlorella vulgaris biomass by in situ transesterification.The results showed that the optimum preparation conditions of solid base catalyst KOH/CeO2 were as follows:50 wt%loading of KOH,350 ? of calcination temperature and 3 h of calcination time.The characterization results shows that the prepared cerium oxide had a high specific area.With the increase of calcination temperature,K2O was formed on the surface of the catalysts.At the optimal transesterification conditions of catalyst content of 14 wt%,methanol to biomass ratio of 6 mL/g,reaction temperature of 60 ? and reaction time of 6 h,the highest biodiesel yield could achieve 92.9%.(3)Mesoporous carbon-based solid base catalyst K/MC-Fe3O4 was successfully prepared and used to produce biodiesel from Chlorella vulgaris biomass by in situ transesterification.The results showed that the optimum preparation conditions of K/MC-Fe3O4 were as follows:45 wt%loading of KOH,500 ? of calcination temperature and 3 h of calcination time.At the optimal transesterification conditions of catalyst content of 16%wt%,methanol to biomass ratio of 8 mL/g,reaction temperature of 60 ? and reaction time of 6 h,the highest conversion efficiency of biodiesel could achieve 93.3%.After calcination at high temperature,the catalyst has high activity because of the formation of K2O.(4)Mesoporous ZrO2-based solid base catalysts K/ZrO2-Fe3O4 were prepared and applied to the production of biodiesel by in situ transesterification of Chlorella vulgaris.Under the optimum conditions,the conversion efficiency of biodiesel in transesterification catalyzed by KOH/ZrO2-Fe3O4 was 96.3%.Compared with the catalyst K2CO3/ZrO2-Fe3O4,the conversion efficiency of Biodiesel Catalyzed by KOH/ZrO2-Fe3O4 increased by 13%under the same conditions.The alkaline strength of catalysts is one of the factors affecting the catalytic transesterification reaction.