Studi proses mekanisme pengadukan dengan metode static -mixer untuk meningkatkan efisiensi transesterifikasi minyak sawit

Abstract

Biodiesel merupakan monoalkil ester (misal: fatty acid methyl ester atau FAME) yang diproses dengan metode transesterifikasi antara trigliserida yang berasal dari minyak nabati atau lemak hewani dengan alkohol rantai pendek terutama metanol untuk digunakan sebagai bahan bakar mesin diesel. Proses esterifikasi atau transesterifikasi dapat dilangsungkan dengan menggunakan katalis atau tanpa katalis. Sejauh ini dalam produksi biodiesel umumnya dilakukan dengan proses transesterifikasi menggunakan katalis basa. Kekurangan dari proses katalis basa adalah: 1) terdapat dua fase campuran minyak nabati-metanol (MeOH) yang memerlukan mekanisme pengadukan yang kuat agar proses transesterifikasi bisa efektif dan reaksi mengarah ke sebelah kanan, 2) dalam purifikasi biodiesel kasar (crude biodiesel) diperlukan proses yang panjang karena di dalam produk masih terkandung impurities yang terdiri dari residu katalis, metanol yang tidak bereaksi, dan sabun yang harus dipisahkan. Waktu reaksi transesterifikasi dengan sistem pengadukan ini berkisar antara 60 – 90 menit.

One of the difficulties faced in the current technology for biodiesel production is the requirement for rigorous mixing of methanol with the feedstock oil in the reactor. Utilization of blade mixer has limitation due to the immiscible state of those substances. This research was devoted to assess of static-mixer utilization in a transesterification reactor for biodiesel production in terms of kinetics reaction (reaction rate coefficient k, activation energy Ea, and collision factor or coefficient factor A). The experiments were conducted by reacting refined bleached deodorized palm olein (triglyceride or TG) with methanol (MeOH) at 50, 55, 60, 65, and 70o C, using potassium hydroxide (KOH) as a catalyst at atmospheric pressure. Molar ratio of TG and MeOH was 1 : 11.5 and KOH used was 1% of palm oil weight. Transesterification process using blade agitator with the same reaction condition was performed as base of comparison to those of static-mixer. Energy consumption was measured for heater during oil heating, transesterification, boiling water and biodiesel drying by kWh meter. It was also conducted for pump for distribution, reactant mixing, and impeller of blade agitator. The experiments showed that static-mixer has significant effect in reducing reaction time to reach required fatty acid methyl ester content (FAME) i.e. 96.5% than those of blade agitator. Transesterification reaction time with static-mixer were shorter than with blade agitator for all temperature levels. Reaction temperature of 65o C with 5 minutes of reaction time demonstrated the best condition for running the static-mixer reactor.