Optimization Study Of Ultrasound-assisted Biodiesel Preparation From Grease Of Case Fatality Livestock And Poultry

In this paper,biodiesel was prepared from diseased swine carcasses.Firstly,concentrated sulfuric acid was used to catalyze transesterification reaction.with purity as the index,the optimum values of time,temperature,catalyst concentration and molar ratio of alcohol to oil were obtained by single factor and response surface experiments.On the basis of the experimental results,three-dimensional ultrasound was added and the kinetics analysis was carried out.In addition,alkali-catalyzed transesterification of the raw material was also studied.Firstly,ultrasonic-assisted concentrated sulfuric acid was used to pre-esterify and reduce acid.On this basis,potassium hydroxide was used to catalyze esterification.Similarly,the optimum values of four factors were obtained by single factor and response surface experiments.The main conclusions are as follows:1.In one-step acid catalysis experiment,the four factors affecting the purity are time,catalyst concentration,temperature and molar ratio of alcohol to oil.The optimum technological conditions are as follows:catalyst concentration is 5.0 wt%,temperature is 68?,molar ratio of alcohol to oil is 10:1,and time is 37 h.Under this condition,the purity can reach the highest 93.7%.The optimum frequency,power and time were 20 kHz,500 W and 8 h respectively,and the purity was 98.1%after 8 h treatment.The kinetic analysis showed that the reaction rate constant of the ultrasound group was 4.45-5.52 times that of the control group.The reaction order of the ultrasound group was about 1.5,and that of the control group was about 1.9.The activation energy of the three-dimensional ultrasound group was 25.58 kJ/mol,which was 22.81%lower than that of the control group,which was 33.14 kJ/mol.2.In the two-step alkali catalytic experiment,the first step of pre-esterification and acid-reducing treatment is to reduce the acid value of diseased swine carcasses below 2.5 mg KOH/g when the catalyst concentration is 1.0 wt%,the molar ratio of alcohol to oil is 6.0:1,the temperature is 65?,the ultrasonic power is 500 W,the frequency is 20 kHz and the ultrasonic time is 60 min.In the second step of alkali catalysis experiment,the four factors affecting the purity of the catalyst are catalyst concentration,time,molar ratio of alcohol to oil and temperature.When catalyst concentration is 1.1 wt%,temperature is 62?,molar ratio of alcohol to oil is 7.5:1,and time is 115 minutes,the purity can reach 98.0%.3.The main components of the product are fatty acid methyl esters of hexadecane and octadecane.Under the optimum conditions,the content of fatty acid methyl esters after vacuum distillation is more than 98 wt%.Its kinematic viscosity(40?)is 6.0 mm2/s,density(20?)is 881 kg/m3,acidity value is 0.42 mgKOH/g,hexadecane value is 52,sulfur content is 19 mg/kg,and cold filter point is 0?,which conform to GB/25199-2017 BD100 biodiesel S50 index.