Wahyudi, - (2018) Pemanfaatan Potensi Energi Polaritas Asam Lemak Untuk Perbaikan Sifat Fisika, Kimia Dan Nilai Kalor Minyak Nabati. Doctor thesis, Universitas Brawijaya.
Abstract
Pemanfaatan minyak nabati untuk bahan bakar alternatif sangat dibutuhkan. Kelemahan minyak nabati sebagai bahan bakar adalah viskositasnya yang tinggi. Jika dibandingkan dengan minyak diesel, nilai kalor minyak nabati relatif rendah. Minyak nabati tersusun dari asam lemak. Panjang rantai karbon dan derajat ketidakjenuhan asam lemak berpengaruh pada sifat minyak nabati. Minyak jarak, minyak sawit dan minyak kelapa memiliki asam lemak penyusun dominan yang berbeda. Minyak jarak didominasi asam lemak tak jenuh ganda, minyak sawit didominasi asam lemak tak jenuh tunggal, sedangkan minyak kelapa didominasi asam lemak jenuh. Perubahan struktur asam lemak pada minyak mempengaruhi sifat-sifatnya. Perubahan struktur dapat diperoleh dengan cara pencampuran dan pemanasan minyak nabati. Asam lemak takjenuh ganda memiliki methylene allylic dan bis-allylic yang relatif lebih lemah ikatannya dibanding posisi ikatan yang lain. Asam lemak takjenuh ganda dan asam lemak jenuh cenderung bersifat polar. Polaritas asam lemak diperkirakan dapat membantu proses perubahan struktur asam lemak takjenuh ganda pada proses pencampuran. Penelitian ini bertujuan untuk mengetahui peran polaritas dan komposisi asam lemak terhadap sifat campuran minyak nabati, terutama viskositas, nilai kalor, densitas dan flash point. Minyak jarak dengan rantai karbon panjang dan tingkat ketidakjenuhan tinggi dicampur dengan minyak kelapa dengan rantai karbon yang pendek dan tingkat ketidakjenuhan rendah. Percampuran dilakukan pada berbagai variasi komposisi. Selanjutnya campuran dipanaskan pada temperatur 90oC dan diaduk selama 30 menit. Pengukuran sifat minyak meliputi densitas, viskositas, nilai kalor dan flash point. Selain itu juga dilakukan pengukuran komposisi asam lemak pada setiap campuran. Cara yang sama dilakukan untuk campuran minyak sawit dan minyak kelapa. Campuran minyak nabati dengan asam lemak jenuh dan tak jenuh tunggal menghasilkan komposisi asam lemak yang linier dengan komposisi asam lemak minyak nabati penyusunnya. Hal tersebut terbukti pada pencampuran minyak sawit dan minyak kelapa. Minyak nabati dengan asam lemak tak jenuh ganda seperti minyak jarak, menghasilkan perubahan komposisi asam lemak yang berbeda dari minyak penyusunnya. Pada pencampuran minyak jarak dengan minyak kelapa, polaritas asam lemak membantu putusnya ikatan asam lemak menjadi rantai yang lebih pendek dan derajat ketidakjenuhan rendah. Perubahan komposisi asam lemak pada campuran menyebabkan perubahan sifat minyak seperti densitas, viskositas, nilai kalor dan flash point. Densitas, viskositas dan nilai kalor tidak hanya dipengaruhi oleh panjang rantai karbon dan derajat ketidakjenuhan, namun juga dipengaruhi oleh jumlah molekul polar pada minyak nabati. Flash point minyak dipengaruhi oleh derajat ketidakjenuhan dan panjang rantai karbonnya.
English Abstract
Utilization of vegetable oil for alternative fuels is needed. The weakness of vegetable oil as a fuel is its high viscosity. When compared with diesel oil, the calorific value of vegetable oil is relatively low. Vegetable oil composes of fatty acids. The length of the carbon chain and the degree of unsaturation of fatty acid affect the properties of the vegetable oil. Jatropha oil, palm oil, and coconut oil contain different dominant fatty acids. Jatropha oil is predominantly polyunsaturated fatty acid, palm oil is dominated by monounsaturated fatty acids, while coconut oil is dominated by saturated fatty acids. Changes in the structure of fatty acids in the oil affect its properties. Structural changes can be obtained by mixing and heating of vegetable oils. The polyunsaturated fatty acids have methylene allylic and bis-allylic which are relatively weaker in bonds than other bonding positions. Polyunsaturated and saturated fatty acids tend to be polar. Fatty acid polarity is expected to assist the process of changing the structure of polyunsaturated fatty acids in the mixing process. The aim of this research is to determine the influence of polarity and fatty acid compositions on mixed oil properties, i.e. viscosity, heating value, density and flash point. Jatropha oil with long carbon chains and high unsaturation levels were mixed with coconut oil with short carbon chains and low unsaturation levels. Mixing was done on a variety of compositions. The mixture was heated at 90°C and stirred for 30 minutes. The properties being evaluated include density, viscosity, heating value and flash point. Next, the measurement of fatty acid composition in each mixture was conducted. The same procedure was done for palm oil and coconut oil mixture. A mixture of vegetable oils with saturated and monounsaturated fatty acids produce a linear fatty acid composition with that of the vegetable oil fatty acid constituent. This is evident in the mixing of palm oil and coconut oil. Vegetable oils with polyunsaturated fatty acids such as jatropha oil, result in changes in a different composition from that of fatty acids of the vegetable oil constituent. In mixing jatropha oil with coconut oil, the polarity of fatty acids helps to break the bonds of fatty acids into shorter chains and low degrees of unsaturation. Changes in the fatty acid composition of the mixture cause changes in oil properties such as density, viscosity, heat value and flash point. Density, viscosity, and heating value are not only influenced by carbon chain length and degree of unsaturation in the vegetable oil but are also influenced by the number of polar molecules. Flash point of oil is affected by the degree of unsaturation and the length of its carbon chain.
Other obstract
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| Item Type: | Thesis (Doctor) |
|---|---|
| Identification Number: | DIS/662.88/WAH/p/2018/061803846 |
| Uncontrolled Keywords: | asam lemak, viskositas, nilai kalor, minyak jarak, minyak kelapa, minyak sawit,-fatty acid, viscosity, calorific value, jatropha oil, coconut oil, palm oil |
| Subjects: | 600 Technology (Applied sciences) > 662 Explosives of explosives, fuels, related products > 662.8 Other fuels > 662.88 Biomas as fuel |
| Divisions: | S2/S3 > Doktor Teknik Mesin, Fakultas Teknik |
| Depositing User: | Endang Susworini |
| Date Deposited: | 02 Feb 2022 08:56 |
| Last Modified: | 08 Feb 2022 02:40 |
| URI: | http://repository.ub.ac.id/id/eprint/189186 |
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