Formulasi Aditif Biodiesel B50 Berbasis Gliserol Ester dan Uji Stabilitas Penyimpanan

Abstract

Fatty Acid Methyl Ester (FAME) merupakan biodiesel yang saat ini digunakan di Indonesia. Pencampuran FAME dan diesel oil masih terdapat kendala: FAME terpisah dengan diesel oil pada suhu rendah. Penurunan kualitas biodiesel disebabkan perubahan sifat fisiko kimia selama penyimpanan, karena adanya oksigen terlarut yang berpotensi merusak mesin. Permasalahan tersebut dapat diatasi dengan aditif gliserol ester (GE). Penelitian ini terdiri atas dua tahap. Pertama, sintesis GE dengan mereaksikan gliserol 99,9% dan asam oleat (1:1 mol/mol) menggunakan katalis PTSA dialiri gas nitrogen 100 cc/menit. Reaksi esterfikasi dilakukan pada suhu 140, 160, 180, dan 240oC pengadukan 400 rpm selama 180 menit. Analisis fisiko kimia GE meliputi: rendemen, angka asam, densitas, viskositas kinematis, dan FTIR. Tahap kedua adalah GE terbaik digunakan sebagai aditif pada biodiesel B50. Jenis aditif divariasikan yaitu GE dan aditif komersial dietil eter (DEE) konsentrasi 1000, 2000, dan 3000 ppm, suhu penyimpanan 25, 12, dan 42oC. Pengujian stabilitas penyimpanan selama 3 bulan, meliputi: angka asam, viskositas, laju korosifitas, dan kadar air. Sintesis gliserol ester suhu terbaik berdasarkan metode Analytical Hierarchy Process (AHP) adalah suhu 160oC dengan atribut rendemen, pH, angka asam, viskositas kinematis, densitas. Rendemen pada suhu 160oC sebesar 95,66%, pH 7, nilai angka asam 11,28 mg KOH/g sampel, viskositas kinematis 75,76 cst, dan densitas 0,944 g/cm3. Hasil sintesis gliserol ester terbaik digunakan untuk aditif biodiesel B50 dengan uji stabilitas penyimpanan selama 3 bulan pada suhu 25, 12, dan 42oC. Parameter ujinya adalah angka asam, viskositas kinematis, korosifitas, dan kadar air. Nilai angka asam dari variasi jenis dan konsentrasi aditif masih memenuhi standar SNI 7182-2015 (0,5 mg KOH/g sampel) dengan rentang nilai 0,148-0,392 mg KOH/g sampel. Viskositas kinematis memiliki rentang nilai 3,12- 3,58 cst yang juga memenuhi standar SNI 7182-2015 (2,3-6 cst). Laju korosifitas tertinggi ada pada minggu ke-1 sebesar 0,447 mpy (GE) dan 0,261 mpy (DEE). Kadar air tertinggi pada hari ke-18 (0,046%), aditif GE 1000 ppm dan kontrol, yang artinya penambahan aditif dapat mempertahankan kadar air pada biodiesel B50. Secara keseluruhan variasi jenis aditif dan konsentrasi memenuhi standar SNI biodiesel 7182-2015. Berdasarkan hasil uji ANOVA dan Duncan (α = 0,05) menunjukkan bahwa suhu sintesis berpengaruh nyata pada rendemen. Suhu sintesis 140oC menghasilkan rendemen yang berbeda nyata, sedangkan suhu 160oC, 180oC, dan 240oC tidak berbeda nyata. Suhu sintesis berpengaruh nyata terhadap angka asam dan viskositas. Uji stabilitas penyimpanan menunjukkan perlakuan jenis, konsentrasi aditif, dan suhu penyimpanan berpengaruh nyata pada angka asam dan viskositas. Uji laju korosifitas menunjukkan bahwa jenis aditif berpengaruh nyata terhadap laju korosifitas. Faktor jenis dan konsentrasi aditif juga berpengaruh nyata pada kadar air, interaksi kedua faktor tersebut mulai terlihat pada hari ke 24.

Fatty Acid Methyl Ester (FAME) is a biodiesel currently used in Indonesia. However, the obstacles of mixing FAME with diesel oil: FAME separates from diesel oil at low temperatures. Physicochemical properties also lead to a decrease in the quality of biodiesel during storage due to dissolved oxygen can possibly damage the engine. The addition of glycerol ester (GE)-based additives can solve this problem. This investigation consists of two phases. The first step is to synthesize GE by reacting 99.9% glycerol with oleic acid (1:1 mol/mol) using a PTSA catalyst flowing at 100 cc/min N2 gas. The esterification reaction was carried out at temperatures of 140, 160, 180, and 240oC with a stirring of 400 rpm for 180 minutes. The physicochemical properties of GE were analyzed: yield, acid number, density, kinematic viscosity, and FTIR. The second stage is the best GE from the first stage is used as an additive to biodiesel B50. The types of additives were varied GE and diethyl ether (DEE) with concentrations of 1000, 2000, and 3000 ppm, storage temperatures of 25, 12, and 42oC. The storage stability test was carried out for three months for: acid number, viscosity, corrosion rate, and water content. The best temperature synthesis of GE based on AHP was at 160oC from yield, pH, acid number, kinematic viscosity, density. The result at 160oC was 95.66%, pH 7, acid number 11.28 mg KOH/g sample, kinematic viscosity was 75.76 cst and density 0.944 g/cm3. The best results of the synthesis of GE were used for the biodiesel additive B50 with a storage stability test for 3 months at temperatures of 25, 12, and 42oC. The test parameters are acid number, kinematic viscosity, corrosiveness, and water content. The value of the acid number from the variation of the type and concentration of the additives still corresponds to the SNI 7182-2015 (0.5 mg KOH/g sample) with a value range of 0.148-0.392 mg KOH/g sample. The kinematic viscosity has a value range of 3.12-3.58 cst corresponds to the SNI 7182-2015 (2.3-6 cst). The highest corrosivity rate at week 1 was 0.447 mpy (GE) and 0.261 mpy (DEE). On the 18th day, the highest water content of 0.046% was found in the 1000 ppm GE and control, which means that the addition of the additive can maintain the water content of the B50. Overall, the type and concentration of additive still met the biodiesel standard SNI 7182-2015. The results of the ANOVA and Duncan's tests (α = 0.05), it was shown that the synthesis temperature had a significant influence on the yield. The synthesis temperature of 140°C led to significantly different yields, but another temperatures didn’t. The synthesis temperature of GE, types, additive concentrations, and storage temperatures significantly affected the acid number and viscosity. The type of additive had a significant influence on the corrosion rate. The factor type and concentration of the additives also influenced the water content significantly, with the interaction of the two factors becoming visible from the 24th day.