碩士 / 大仁科技大學 / 環境管理研究所 / 102 / Biodiesel (fatty acid methyl esters, FAMEs) is a mixture derived from the esterification and transesterification of free fatty acids (FFAs) and triglycerides and is typically made from renewable biological resources. Microalgae are a source of triglycerides. Many microalgae are exceedingly rich in lipids and oils, which can be converted into biodiesel. Microalgae not only have higher biomass production and faster growth than those of energy crops, producing many times more oil for biodiesel production than traditional oilseed crops on an area basis, but can also reduce the amount of global warming gases and consume other pollutants. Microalgal oils suitable for making biodiesel are common.
Four main synthetic approaches have been used for biodiesel production, namely dilution, microemulsion, pyrolysis, and transesterification. The most commonly used method for converting microalgal oils to biodiesel is transesterification. The transesterification reaction is an important step in the overall process of biodiesel production, which is both energy- and cost-intensive. Several factors influence the transesterification reaction. Transesterification can be catalyzed by both alkali and acid catalysts. The alkali catalysis reaction is about 4,000 times faster than the acid catalysis reaction. However, the performance of alkali catalysts is strongly affected by the presence of FFAs in the feedstock.
In the present study, one of the dominant green microalgal species, Monoraphidium sp., isolated from local source water was cultured in BG-11 medium. The dried algal biomass was used for biodiesel production. The objectives of this study firstly are to understand the effect of the factors including alcohol quantity, reaction temperature, reaction time, and catalyst concentration on FAMEs yield. An experimental design is implemented to examine the effects among the factors, namely alcohol quantity, reaction temperature, reaction time, and ultrasound radiation that affect the FAMEs yield from microalgal biomass. Due to biomass drying has been demonstrated to be one of the most important economic steps in the microalgae production process, this study therefore also aims to evaluate the FAMEs yield of the wet microalgae biomass among the four transesterification process in order to reduce the biomass drying requirements.
The results indicated that the highest FAMEs yield of Monoraphidium sp. was obtained at an alkali catalyst amount 0.5 % NaOH/MeOH of 18 mL, a reaction temperature of 60 °C, and a reaction time of 30 min, while the highest FAMEs yield obtained at a 18 mL acid catalyst amount containing 2 % H2SO4/MeOH, a 60 °C reaction temperature, and a 80 min reaction time for the acid catalysis reaction. Under the experimental range considered, the significant factors for FAMEs yield are the methanol quantity, reaction time, and reaction temperature for both alkali and acid catalysis process. The FAMEs yield increased with decreasing moisture of wet microalgae biomass. However, no significant difference in FAMEs yield affected by moisture of wet microalgae biomass was found when reaction with suitable catalyst amount was adopted. The highest FAMEs yield of wet microalgae biomass was obtained at a 25 mL acid catalyst amount containing 0.5 % NaOH/MeOH and 2 % H2SO4/MeOH respectively. Furthermore, it was observed that alkali-acid-catalyzed transesterification led to a higher FAMEs yield than that obtained only alkali or acid catalyzed transesterification.
| Identifer | oai:union.ndltd.org:TW/102TAJ00700039 |
| Date | January 2014 |
| Creators | Xian-Ting Zhu, 朱憲庭 |
| Contributors | Jen-Jeng Chen, 陳振正 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 107 |
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