Biodiesel merupakan bahan bakar alternatif mesin diesel yang berasal dari minyak nabati. Memiliki kelemahan, yaitu mudah teroksidasi. Hal ini disebabkan karena biodiesel memiliki ikatan karbon tak jenuh yang membuat tidak stabil. Untuk meningkatkan ketahanan oksidasi diperlukan aditif antioksidan. Salah satu alternatif antioksidan yang lebih prospektif ialah Tert-Butylhydroquinone TBHQ baik dari sisi harga maupun ketersediaannya, namun TBHQ memiliki polaritas yang berbeda dengan biodiesel yang menyebabkan TBHQ tidak dapat terdistribusi dengan baik. Peningkatan distribusi TBHQ dalam biodiesel dilakukan dengan penambahan surfaktan yang dapat meningkatkan dispersi antara dua senyawa yang tidak saling larut.Surfaktan yang umum digunakan untuk mencampur aditif bersifat polar pada minyak nabati yaitu Glycerol Monostearate. Variasi konsentrasi Glycerol Monostearate dilakukan untuk mengetahui komposisi terbaik meningkatkan stabilitas oksidasi biodiesel. Stabilitas oksidasi biodiesel diukur berdasarkan peningkatan angka asam dan penurunan bilangan iodin. Hasil penelitian menunjukkan penambahan surfaktan Glycerol Monostearate mampu meningkatkan dispersi TBHQ dalam biodiesel meningkatkan kinerja TBHQ sebagai antioksidan. Penambahan Glycerol Monostearate 300 ppm TBHQ 2000 ppm rasio 3:20 menunjukkan hasil terbaik dalam mencegah oksidasi pada biodiesel.

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Biodiesel is an alternative fuel for diesel engines which comes from vegetable oils or animal fats. Biodiesel has disadvantages, one of disadvantage is easily oxidized. Oxidation in biodiesel is caused by having unsaturated carbon bonds that make it unstable. Antioxidant additives are required to increase the oxidation resistance. Pyrogallol is an antioxidant additive commonly used to prevent oxidation of biodiesel because it has a good performance, but expensive. One of the more prospective antioxidant is Tert Butylhydroquinone TBHQ both price and availability, but TBHQ has a different polarity than biodiesel that causes TBHQ can rsquo t be well distributed in biodiesel. Increasing the distribution of TBHQ in biodiesel can be done by the addition of surfactants which can increase the dispersion between two non soluble compounds.

In this study apply a surfactant commonly used to mix polar additives on vegetable oils that is Glycerol Monostearate surfactant. Concentration variation of Glycerol Monostearate addition were performed to find out the best amount of composition that can improve the oxidation stability of biodiesel. The biodiesel oxidation stability was measured by increasing the acid number and decreasing the iodine number for one month of storage. The results showed that the addition of Glycerol Monostearate could increase TBHQ dispersion in biodiesel and improve the performance of TBHQ as antioxidant. The addition of 300 ppm Glycerol Monostearate and TBHQ 2000 ppm ratio 3 20 showed the best results in preventing oxidation in biodiesel.