Research On Preparation Of Biodiesel From Waste Frying Oil By Sonochemical Reactor

As an important part of waste cooking oil, waste frying oil is composed of glyceride.By reacting with methanol or ethanol, glyceride can be turnied into glycerinum andaliphatic ester, the latter is called biodiesel. So using waste cooking oil to producebiodiesel has high economic value. Considering the traditional method is timeconsuming, ultrasound assistance can shorten reaction time to a large extent andincrease transesterification conversion. However， there are few article focus onsonochemical reactor applied to prepare biodiesel.The decolorized frying oil is selected as raw material, KOH as catalyst and gaschromatography (GC) as test tool to study the reinforcement of producing biodieselwith ultrasound. The contrast experiments under mechanical stirring and ultrasonicirradiating without catalyst determines the ultrasonic reinforcement heads from thephysical effects and the impacts of reaction time, reaction temperature, ethylalcohol-oil ratio, concentration of catalyst， ultrasonic power and positions in theultrasonic field are researched. The optimal temperature is determined as45℃though comprehensive consideration of system activity and cavitation intensity, theoptimal power is100W though sound field’s intensity and homogeneity, the ethylalcohol-oil ratio is6:1~9:1and concentration of catalyst is better at0.5wt%~2wt%.Furthermore, when the reactants interface is near the position of standing wave in thesound field, the transesterification is effectively promoted. The central compositedesign of response surface analysis in Design Exper software is choosen as a methodto optimize the transesterificationin, combined with three factors (ethyl alcohol-oilratio, concentration of catalyst, positions in the ultrasonic field) and its optimal level.With the guidance of design criteria and biodiesel transesterification conditions, thesonochemical reactor is designed and manufactured which can provides single soundfield and2d,3d sound field. Using ultraviolet-visible spectrophotometry, one methodof hydroxyl radicals capture method, the variety of sound fields of new thesonochemical reactors are studied. It shows that absorbance of methylene bluesolution linearly related to ultrasonic time, the intensity of acoustic field has thecharacteristics that3d sound field>2d sound field> single sound field and thecavitation of mixed sound field is greater than the algebraic sum of each ultrasonic cavitation. It means that improve the uniformity of the sound field can effectivelyincrease the sonochemical yield which provides a theoretical support in designing ofsonochemical reactor.The transesterification of biodiesel with waste frying oil in the new sonochemicalreactor is explored. At the optimum experiment condition and the best operatingcondition of the reactor, the conversion rate could reach90.47%in jusst5min andcan basically keep stability within40min. The experiment illustrates that the reactorhas a certain production capacity used for waste frying oil transform into biodieselproduction with stability and efficiency.