| Biodiesel is an environment-friendly and renewable bioenergy. It's an excellent fuel to substitute for petrolic diesel and can be used in any diesel engine which needn't to be changed on its construction. Along with petroleum drying up and environment problem, people are paying more attention to the biodiesel today. But the higher price of biodiesel hobbles itsself development. So we should research advanced technologies to reduce its cost to produce. This paper mainly investigate to produce biodiesel by continuous process in homogeneous phase by adding co-solvent in the process.In order to reduce the reaction time and increase the conversion ratio, we also design a tubular static-mix reactor which are efficient heat and mass transfer.This research selected aether solvents including isopropyl ether, 1,4-dioxane and terahydrofuran(THF), ketone solvents including acetone and butanone, as well as acetone and hexane which consists co-boiling solvent as co-solvent. We investigated their solubilizing power of methanol in plant oil, and found the best co-solvent was THF. We also found the performance of acetone as co-solvent was improved to make oil-alcohol as one phase when hexane was added in. However butanone has almost the same performance with THF. Because of low price and better solubilizing capability we chose butanone as co-solvent to prepare biodiesel .In this experiment we used KOH as catalyst, methanol and rapeseed oil as material .In our work, central composite experiment design was applied to investigate the biodiesel production factor effects, and a lin / quad math model was gained to predict the biodesel conversion ratio. A maximum conversion of 99.2% (GC content) was achieved under the condition of molar ratio 1:13.1 of oil to methanol and 0.67% KOH as catalyst at 65 degrees.We used branch-chain alcohol and methanol to produce biodiesel, so that contain branch-chain esters .The branch-chain alcohol was one of these alcohols: isopropanol, isobutyl alcohol, sec-butyl alcohol, and isopropanol has better reaction property in these alcohols. The effect of reaction time, temperature, catalyst dosage, and the molar ratio of isopropanol to methanol was researched on fatty acid isopropyl esters (IPE) content. The IPE content could be more than 50% in this experiment, but glycerin was unease separated from esters when it over 20%. The viscosity of different IPE content were mensurated and it higher than fatty acid methyl esters .The production were analyzed for cold flow performance through condensation point(CP) and cold filter plugging point (CFPP)determinations and they were decreased from 5 to 8℃compared with FME.A continuous process for biodiesel production was investigated in a pilot plant, using rapeseed oil and methanol as the feedstock, and KOH as the catalyst. The process was equipped with a tubular static mixer as reactor and co-solvent such as tetrahydrofuran (THF) and butanone was added in. This experiment study their infection and we found when co-solvent was added in the conversion ratio was improved in evidence. Compared with no co-solvent the conversion ratio increased from 56% to more than 80% at feedstock passed the pipe once and the tiptop conversion increased from 76.5% to 94.0% when butanone or THF was added in. All these were at the same reaction condition ,molar ratio of methanol to oil was 6:1, catalyst was 1% weight of oil, the heating oil temperature was controlled in 250℃to 270℃,total flow was 5L/min. It's indicated that cut down the co-solvent dosage in a limit range the conversion ratio and reaction velocity of biodiesel production in this equipment will not change, such as when chose THF with 1/6 vol. of methanol or butanone with 1/12 vol. of methanol, the result reduce little compared with full dosage which can be enough to make methanol and oil form one phase. All these reaction could reach 90% conversion ratio at 6min to 9min except no co-solvent.
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