Study On The Coupling Process Of Catalytic Esterification And Extraction By Methanol For High Acid Value Waste Cooking Oil

As a new renewable fuel,biodiesel was one of the effective ways to resolve the current energy crisis.The high cost and the limited supply of raw materials were the main problems of biodiesel production.The waste oil with high acid value was a welcome raw oil of biodiesel production because of its low cost.FFAs in the oil must be removed during the transesterification process.But traditional deacidification method had a lot of disadvantages. This paper tried to develop a new deacidification method.In the coupling process of catalytic esterification and extraction,the solid acid in the extraction-esterification column was used both as packing and catalyst.Fatty acid methyl esters(FAME) were prepared and the acid value was reduced by the coupling process of catalytic esterification and extraction by methanol for the waste oil with high fatty acid content.According to pre-experiment,732 cation-exchage resins were chosed as catalyst and packing.Methanol and waste oil entered from the bottom to top of the column by co-current operation.In the thesis,the optimal condition of the coupling process was confirmed.The effect of two operation methods in the coupling process,named as running operation and circulating operation, on the decacidification efficiency and esterification yield were studied.In running operation,the effect of process parameters on the coupling process were considered,such as residence time,mass ratio of methanol/oil(wt/wt), temperature.The experimental results showed the optimum parameters of the process were that the ratio of methanol to oil is 1:1,the residence time was 52.31min,and temperature is 60℃.The acid value of raw oil reduced to 2.95mgKOH/g oil from 52.45mgKOH/g oil.The esterification yield is 94.53%. Besides,the times of cycling had little effect to the deacidification efficiency. In circulating operation,the influence on the coupling process such as flowrate, mass ratio of methanol/oil(wt/wt),feedstock mass,were considered.The experimental results showed the optimum parameters of the process were that the ratio of methanol to oil is 0.5:1,and the flowrate was 6.20ml/min.The acid value of raw oil reduced to 2.15mgKOH/g oil from 52.45mgKOH/g oil.The esterification yield is 94.11%.After transesterification with HC and distillation,the properties of the biodiesel prepared from the oil were in accord with China biodiesel standard.Compared with the process of extraction,the deacidification efficiency of the coupling process was equivalent to seven cross-flow extraction stages; compared with the process of esterification,the esterification yield after 32 min of the coupling process was 90.30%,while the esterification yield of the esterification process was about 22%.Next a series of experiment indicated that the decacidification efficiency and esterification yield of the coupling process were better than that of the traditional MS catalytic esterification.In the thesis,lifetime of the catalyst was studied.Ion-exchange resins could be steadily used 30 h without decline,the resin could not be steady after three times regeneration.