Ahmed Probudha Hasan*
Department of Mechanical Engineering, Khulna University of Engineering and Technology, Khulna-9203, Bangladesh.
Md. Abdul Wakil
Department of Mechanical Engineering, Khulna University of Engineering and Technology, Khulna-9203, Bangladesh.
Md. Abdullahil Kafy
Department of Mechanical Engineering, Khulna University of Engineering and Technology, Khulna-9203, Bangladesh.
Non-edible source; Rice bran oil; Biodiesel; Transesterification process
Resource Development and Management
Transesterification ProcessTransesterification can be defined as a chemical reaction in which alcohol reacts with triglycerides of fatty acids (vegetable oil), in presence of a catalyst. It is a reversible reaction. In this process, an ester is transformed into another through an interchange of the alkoxy moiety. Transesterification is used mainly in the synthesis of polyesters and in the production of biodiesel because it has more advantages than ester synthesis from carboxylic acids and alcohol. There are mainly three types of transesterification process based on the use of catalyst and those are Base-Catalyzed Transesterification, Acid-Catalyzed Transesterification and Lipase-Catalyzed Transesterification. All three have their own benefit for biodiesel production from various resources depending on FFA content, temperature and reaction time. There are other few processes for example Heterogeneously Catalyzed Process, Non-Ionic Base-Catalyzed Processes, etc. 2.2. Production of Biodiesel from Rice bran oil refined & neutralized rice bran oil collected from market containing following properties per litter [Moisture0.11 %, Free Fatty Acid (FFA) 0.25 %, Acid value (as KOH) 0.44 mg./ gm., Density at 30ºC is 0.913 gm. / ml, Unsaponifiable matters 0.75 %, Saponifiable matters (as mg KOH/g) 188.61, Peroxide Value (PV) 0.87 meg O/kg, etc. ]* All data are collected from Rashid Oil mill (for White Gold Rice Bran Oil. The selection of appropriate and economical transesterification process is the first priority for biodiesel production. As the FFA content of collected rice bran oil is less than 2% so the base catalyst transesterification process would be the right choice. In transesterification reaction, three moles of the alcohol reacts with one mole of triglyceride. So theoretically the molar ratio of RBO to alcohol should be 1:3. But transesterification is a reversible reaction; to take the reaction always the forward excess amount of alcohol is used. Different studies show that the best reaction occurs at the molar ratio of 1:5 to 1:7 of oil to methanol. Bradshaw and Meuly (1944) reported that a molar ratio greater than 1:5.25 is effective for better separation of ester and glycerol phases. The average molecular weight of RBO is about 867.90 g/mol (source: Ying Xia Li, 2011; about 875g/mol by Lin L., 2008 and the molar mass of methanol is 32.04 g/mol. By the molar ratio to volume calculation, we get for 1 litter of RBO about 255.2 ml of methanol is required (calculation for 1:6 molar ratio of oil to alcohol). For this catalyst NaOH is needed about 18.26 gram (for 2% catalyst) as the density of the RBO is 0.913 g/ml. For small-scale production of biodiesel 250 ml oil, 63.8 ml methanol and 4.565 gm. sodium hydroxide is taken. 3.Prospect of Rice Bran for Biodiesel in Bangladesh According to the Energy and Mineral Resources Division (EMRD) of Bangladesh three major resources (natural gas, coal and petroleum) are used to fulfill the total energy crisis. Among them natural gas plays the most vital role by ensuring 75% of the commercial energy (source: EMRD). But most of this gas is used in electricity production, household purposes and industrial purposes. A new sector is booming which is CNG. Till June 2011 total number of CNG converted vehicles is 1, 96,783 (source: Petro Bangla). Although the total number of registered petroleum vehicles is about 18, 99,193 till May 2013(source: brta). Among the total number of diesel vehicles is about 2, 81,588 (source: brta). This huge amount of vehicles as well as Bangladesh railways consumed about 3.24 million metric tons of high-speed diesel in the year 2011-12 (source: BPC). The current consumption of Petroleum Products in Bangladesh is 3.7 MMT/annum and the annual growth rate is 4% (source: BPC). The only natural resource to supply fuel (CNG) into this huge amount of vehicles in Bangladesh is natural gas. The scarcity of energy is not for a split of a moment, it has an increasing rate with the development and modernization of the human race. So the selected biodiesel must have the raw material which is available all year round, purchasing cost is low, should not affect the cultivation of human food products, and has an increasing rate of production to meet the energy hunger. In Bangladesh, it can be said undoubtedly that the production of rice is peerless comparing to the production of other biodiesel raw materials such as Jatropha, Neem, Sunflower, Coconut, Algae, Cottonseed, Soybean, Mosna, etc. It can be said unambiguously that without hampering the valuable land to produce necessary human foods, the selection of raw materials for biodiesel production in Bangladesh must be rice bran. From a graph of raw material availability and projected estimation for biodiesel production for year 2008-09, 2009-10, and 2010-11 (for rice production of 31.317, 31.975, and 33.54 million metric ton respectively) the prospect of rice bran for biodiesel production.
Procedia Engineering 90 ( 2014 ) 746 – 752
Journal