Optimization and characterization of palm ethyl ester produced by mechanical agitation and ultrasonic assistance | |
| Author | Kate-natee Noipin |
| Call Number | AIT Diss. no.ET-14-02 |
| Subject(s) | Biodiesel fuels--Thailand--Testing Palm oil--Thailand--Analysis |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science in Energy |
| Publisher | Asian Institute of Technology |
| Abstract | Increase in the consciousness to address environmental problems and the need to conserve fossil fuels has led to various approaches to address one of the main challenges of this century, namely, greenhouse gas emission reduction. Using biofuel is one key measure to mitigate the problems, as it is an alternative fuel to petroleum products derived from renewable resources. It has lower emissions than petro - diesel, bio degradable and helps reduce both greenhouse gas and sulfur emissions. The current biodiesel production is basically carried out in a batch process with mechanical agitation. Palm oil and methanol are the major feedstock for biodiesel production. One of disadvantages of methanol derived biodiesel is that methanol used today is produced from the petroleum industry. This makes biodiesel not a truly carbon - neutral fuel. Therefore, ethanol derived from agricultural raw material is an interesting option to be considered to produce biodiesel, namely ethyl ester. Many literatures indicate that alkali catalyst is the most favorite one for biodiesel production. However, the production of biodiesel by using ethanol in alkali - catalyzed transesterification is more difficult than that by using methanol. The approach to improve ethyl ester yield, as well as the optimal condition of ethyl ester production, is not clearly known. Ultrasonic assistance is one interesting options for the biodiesel production process because ultrasonic transesterification is expected to improve biodiesel production and lead to continuous production process. Nonetheless, there are only limited studies on the optimization of alkali - catalyzed transesterification, especially when using ethanol as a feedstock, and in the application of factorial design for ethyl ester production especially with ultrasonic assistance. This research thus aimed to study (a) optimization of ethyl ester production by two processes: batch process with mechanical stirring, and continuous process with ultrasonic irradiation by potassium hydroxide - catalyzed transesterification of palm oil and ethanol, and (b) characterization of the products and its pollution/environmental effects For batch process, experiments were conducted in a lab - scale 5L batch reactor with mechanical stirring provided with a reflux condenser. The reaction temperature was kept constant throughout the reaction by immersing the reactor in a thermostatic bath. T he variables considered were ethanol/oil molar ratio, reaction temperature and catalyst concentration by weight of palm oil and the responses were ethyl ester yield. In total, 24 experiments were done to determine the ethyl ester yield from the results of products’ weight and ethyl ester content. Statist ical analysis was carried out and polynomial model for predicting the amount of ester yield was developed. Furthermore, a second - order model was plotted as a three - dimensional surface and contour plots representing the response as a function of main effects and interaction effects to show the ester yield for the experimental range of the parameters. Catalyst concentration was found to be the most important factor and has negative effect on ethyl ester yield, while reaction temperature is the second factor of significance with negative effect on ethyl ester yield, due to yield losses caused by soap formation from saponification - side reaction and ethyl ester dissolution in glycerin. The results indicate that reaction conditions with high reaction temperature ( >60 O C) and catalyst concentration (>1.5%) should be avoided and high ethyl ester conversion can be obtained at small amount of catalyst, around 0.5 - 0.8%, and wide range of temperature of 55 - 75 O C. For continuous process, two mixing tanks with working volu me of 10 liters, one separation tank with working volume of 20 liters were used. A reactor column had a working flow rate of 0.5 L/min, and the reagent then separated into 2 layers in the separation tank, crude ethyl ester and glycerin. An ultrasonic trans ducer with flow cell, having the frequency of 20 kHz and a maximum power of 1.5 kW, was used to conduct the transesterification reaction. The independent variables considered were ethanol to oil molar ratio, catalyst concentration, reaction temperature and ultrasonic amplitude; and the response was ethyl ester yield. 40 experiments were conducted. The statistical analysis and response surfaces for the predicted values of the ethyl ester yield as a function of each pair of key parameters were done. The resul ts show that ethanol to oil molar ratio, catalyst concentration, and ultrasonic amplitude have positive effects on ethyl ester yield, whereas reaction temperature has negative influence on ethyl ester yield. This study shows that ultrasonic irradiation imp roved the ethyl ester production process to achieve ethyl ester yields above 92%. The reaction conditions with; ethanol to oil molar ratio between 9:1 and 11:1; catalyst concentration between 1.5 - 1.7%wt; reaction temperature between 35 - 40 o C; and ultrasonic amplitude at 150 micron can achieve high ethyl ester yields. The use of factorial design of experiments and statistical analysis provided a polynomial model for predicting the amount of ester yields, namely responses. Second - order models were developed as a function of the key variables, for batch process and continuous process. The developed models predict the results in the experimental ranges studied adequately. The produced ethyl ester was characterized and tested to determine the properties and emis sions, and was further evaluated by its use in an agricultural engine. It was found that all properties of the products were within the limits of the specification of community biodiesel of Thailand, such as, density 872 kg/m 3 , viscosity 4.9 cSt, flash poi nt 183 o C, sulfur content 0.0001 %wt, water and sediment <0.025, total acid number 0.27 - 0.28 mgKOH/g, free glycerin <0.005 and total glycerin 0.55 %wt. Thus, ethyl ester from palm oil can be used as fuel effectively especially for community level or low speed diesel engine. In addition, the produced ethyl ester was evaluated for the air pollution studies including regulated emissions (NOx, CO, CO 2 , PM, and THC (Total hydrocarbon) emissions). The results show that the THC of biodiesel is slightly lower than that of diesel ( - 1.8 to - 3.6%). While, CO and PM of biodiesel are lower than those of diesel ( - 38% for CO and - 30.8 to - 33.3% for PM). However, NOx and CO 2 emissions from biodiesel are higher than those from conventional diesel (+3.2 to +4.0%). All the re sults of experiments – optimization, characterization and emissions – of this study were compared with literatures and discussed. The uniqueness of this research is its focus on ethanol - derived biodiesel from palm oil using ultrasonic assistance . The resul ts of this study also have potential to develop to commercial - scale production, and also help in the efforts to greenhouse gas mitigation and fossil fuel consumption reduction in the transport sector |
| Year | 2014 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Energy Technology (ET) |
| Chairperson(s) | Kumar, Sivanappan |
| Examination Committee(s) | Salam, P. Abdul ;Anal, Anil Kumar |
| Scholarship Donor(s) | HM Queen Sirikit Scholarship ;Asian Institute of Technology Fellowship |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2014 |