STUDI STABILITAS TERMAL DAN SIFAT FISIKOKIMIA CAMPURAN BIODIESEL B40 MENGGUNAKAN KO-SOLVEN ALKOHOL DAN ADITIF

Abstrak

Penggunaan bahan bakar B40 memiliki kendala teknis terkait viskositas yang tinggi dan kerentanan terhadap pemisahan fasa, terutama pada suhu rendah. Penelitian ini bertujuan untuk mengevaluasi pengaruh penambahan ko-solven (etanol dan n-butanol) serta zat aditif terhadap stabilitas fasa dan sifat fisikokimia B40. Pengujian diawali dengan pencampuran sampel menggunakan magnetic stirrer (200 rpm, 10 menit). Stabilitas campuran dievaluasi melalui uji kontrol suhu termal (10°C–90°C) dan uji stabilitas penyimpanan selama 20 hari pada tiga kondisi lingkungan (ruang terbuka, ruang tertutup 28°C, dan ruang pendingin). Karakteristik fisikokimia dianalisis melalui uji densitas, viskositas, prakira titik beku, dan kadar air dengan menggunakan dua bahan dasar berbeda (HSD dan Solar Pertamina). Hasil penelitian menunjukkan bahwa campuran terbukti stabil secara termodinamik, tidak mengalami pemisahan fasa makroskopis, dan tetap homogen baik selama siklus suhu maupun penyimpanan 20 hari. Secara fisikokimia, penambahan etanol dan aditif berhasil menurunkan viskositas. Nilai densitas sangat dipengaruhi oleh bahan dasar, yakni berkisar pada 0,85–0,88 Kg/L untuk base HSD dan 0,83–0,84 Kg/L untuk base Pertamina. Walaupun etanol cenderung menaikkan kadar air hingga lebih dari 2%, penggunaan aditif efektif menekan kadar air kembali ke level 0,49% (HSD) dan 0,20–1,59% (Pertamina). Selain itu, formulasi campuran ini mampu menunda pembentukan kristal padat dengan titik beku yang berhasil diturunkan hingga mencapai 1°C. Kesimpulannya, modifikasi B40 dengan kombinasi etanol, n-butanol, dan aditif terbukti kompatibel dan efektif dalam mempertahankan stabilitas fasa serta memperbaiki karakteristik aliran dingin (cold flow properties), sehingga sangat potensial diaplikasikan secara luas.

The use of B40 fuel faces technical challenges related to high viscosity and susceptibility to phase separation, particularly at low temperatures. This study aims to evaluate the effect of adding co-solvents (ethanol and n-butanol) and additives on the phase stability and physicochemical properties of B40. The experiment commenced with sample mixing using a magnetic stirrer (200 rpm, 10 minutes). The stability of the mixture was evaluated through thermal control tests (10°C–90°C) and a 20-day storage stability test under three different environmental conditions (open space, closed room at 28°C, and freezer). Physicochemical characteristics were analyzed through density, viscosity, estimated freezing point, and water content tests using two different base materials (HSD and Pertamina Diesel). The results indicated that the mixtures were thermodynamically stable, did not undergo macroscopic phase separation, and remained homogeneous during both thermal cycling and the 20-day storage period. Physicochemically, the addition of ethanol and additives successfully reduced viscosity. Density values were highly influenced by the base material, ranging from 0.85–0.88 Kg/L for the HSD base and 0.83–0.84 Kg/L for the Pertamina base. Although ethanol tended to increase water content to more than 2%, the use of additives effectively suppressed it back to 0.49% (HSD) and 0.20–1.59% (Pertamina). Furthermore, the mixture formulation was able to delay the formation of solid crystals, successfully lowering the freezing point to as low as 1°C. In conclusion, the modification of B40 with a combination of ethanol, n-butanol, and additives proved to be compatible and effective in maintaining phase stability and improving cold flow properties, demonstrating its high potential for widespread application.