Fundamental Research On Chlorella Derived Biofuels By Higher Pressure Catalytic Liquefaction

In today’s rapid economic development in China and under the background of the dependence on oil imports continuously improving, the technology of biomass converting into liquid fuel has important strategic significance to our country’s sustainable development. This research, taking Chlorella (one kind of microalgae rich in protein) as raw material, aims at converting the microalgae into biofuels by direct liquefaction in autoclave. The following parameters were investigated in this paper: the reaction temperature, holding time, ratio of material to solvent, the type and dosage of catalysts. To study the characteristics of bio-oils thoroughly, the instruments of elemental analyzer, Fourier transform infrared spectrophotometry (FT-IR), gas chromatography-mass spectrometer (GC-MS) and thermogravimetric analysis were employed in the analysis parts. The purpose of this research is to discuss the liquefaction process, enhance the bio-oil yield and improve the quality of bio-oil through additive of catalyst.The results showed that the suitable conditions are reaction temperature260℃, reaction time30min, and the ratio of material to solvent0.2g/mL. Under these conditions the bio-oil yield reached67.28%, and residue yield was7.07%. Elemental analysis data for the oil illustrated that C content increased and that of O reduced significantly, and the HHV (High Heat Value) increased up to30.23MJ/kg. GC-MS results, combined with that of FT-IR, indicated that the bio-oils might mainly consist of ester and ketone compounds. The addition of NaOH, K2CO3, and KOH et al. did not increase the bio-oil yields, while with5wt.%FeS the bio-oil yield reached72.47%and residue yield declined to4.30%. Although ethylene glycol improved the bio-oil yield, the quality of bio-oil downgraded. Through the analytical means, it could be found the C content reduced and O content increased in contrast to the feed, and the HHV declined to19.23MJ/kg. FT-IR and GC-MS analyses indicated that the ester and ketone compounds reduced, while acid compounds increased. The compositions of bio-oil became more complex.The ocean waste shell was taken as catalyst. The suitable conditions were reaction temperature260℃, reaction time15min, the ratio of material to solvent0.2g/mL and the dosage of shell powder5%. Under these conditions the bio-oil yield reached76.58%, and residue yield was about6%. The addition of shell powder shortened the reaction time, as well as obtained high bio-oil yield to save the cost of production. Through calculating the element data, the HHV of bio-oil was30.16MJ/kg. GC-MS results, combined with that of FT-IR, indicated that the ester compounds content increased of the bio-oil. Besides the ketone and alcohol compounds existed in the bio-oil.When impregnation method of zeolite adopted as solid acid catalyst, it was effective for liquefaction of Chlorella. The yield of bio-oil reached74.58%, and residue yield was6.33%. The HHV of bio-oil was29.36MJ/kg, and ester and ketone compounds were dominant in it. Through esterification simulated experiment, it was found that the compositions of bio-oil almost no change. It indicated the direct liquefaction of Chlorella not only obtaining bio-oil, but also improving the quality of it. So the economic cost declined.