1.0
INTRODUCTION
1.1
Background of experiment With the increasing price of petroleum, the limited of its resources, and the environmental concerns, renewable and more environmentally benign energy sources have been developed. Biodiesel is one of the most promising substitutes. Biodiesel is a nonpetroleum-based fuel that generally consists of fatty acid methyl esters or fatty acid ethyl esters, respectively derived from the transesterification of oil, whose main components are triglycerides, with methanol or ethanol. The transesterification process can be catalysed by bases, acids, and enzymes. Base catalysts are more attractive by their faster speed than acids and lower price than enzymes in this reaction. The homogeneous alkaline catalysts, usually potassium hydroxide(KOH) or sodium hydroxide(NaOH), now widely used in industrial production, have disadvantages, including a separating problem of its catalyst and product as well as a huge amount of wastewater. Moreover, the homogeneous base catalysts are sensitive to water and acid. Thus, the vegetable oil has the requirement of its water and fatty acid content, which limits the source of the raw materials. Palm oil, which will be used in this experiment, is one of the four leading vegetable oils traded on the world market. Because it is cheaper than canola, rapeseed, or soybean oil, the use of palm oil would reduce the overhead cost of biodiesel production and generate a ready supply of diesel fuel substitute. For our experiment, biodiesel will be synthesis from palm oil, methanol and sodium hydroxide with effect factor of methanol/oil molar ratio in the reaction. This reaction is known as a transesterification reaction. Transesterification is the process of transforming one type of ester into another type of ester. The overall mechanism is catalyzed by the presence of NaOH. In the first step of the reaction, NaOH reacts with methanol in an acid-base reaction. The product of this reaction is the very strong base sodium methoxide and water. In the second step, the sodium methoxide acts as a nucleophile and attacks the three carbonyl carbons of the vegetable oil. This produces a tetrahedral intermediate that is highly unstable. The overall result is the "cracking" of the triglyceride. The elimination of the glycerol backbone leads to the formation of the three methyl esters (biodiesel) and glycerol. The glycerol will fall to the bottom, and the methyl ester (biodiesel) will float to the top.
1.2
Objective of experiment To synthesis biodiesel from palm oil, methanol and sodium hydroxide with effect factor of methanol/oil molar ratio in the transesterification reaction.
1.3
Scope of Experiment The scope of experiment will only include the study the lab-scale production of biodiesel from palm oil, methanol and sodium hydroxide.
2.0
LITERATURE REVIEW The United States is the largest single consumer of fossil fuels in the world. Each year, the U.S. consumes 125 billion gallons of gasoline and 60 billion gallons of diesel fuel. It is desired to find alternative feedstock due to high current energy consumption. One such alternative feedstock is vegetable oil. Vegetable oil offers the benefits of a greener synthetic route for obtaining diesel fuel. This fuel source is known as biodiesel, and can be synthesized on an individual level or on an industrial scale. Transesterification is the process of exchanging the organic group R” of an ester with the organic group R’ of an alcohol and possibly with the aid of catalyst (Wikipedia).
The overall process is normally a sequence of three consecutive steps, which are reversible reactions. In the first step, from triglycerides, diglyceride is obtained, then from diglyceride, monoglycerides is produced and in the last step, from monoglycerides, glycerin is obtained. In all these reactions esters are produced. The sequences reactions are shown below:
Triglycerides (TG) + R’OH Diglyceride (DG) + R’OH
↔ ↔
Monoglycerides (MG) + R’OH
Diglycerides (DG) + R’COOR1
Monoglycerides (MG) + R’COOR2 ↔
Glycerin (GL) + R’COOR3
Biodiesel production in laboratory is done by reacting palm oil and methanol with the aid of NaOH (catalyst), separating the glycerine from the mixture and obtaining the desired product. In the first step of the reaction, NaOH reacts with methanol in an acid-base reaction. The product of this reaction is the very strong base sodium methoxide and water. In the second step, the sodium methoxide acts as a nucleophile and attacks the three carbonyl carbons of the vegetable oil. This produces a tetrahedral intermediate that is highly unstable which also called the "cracking" of the triglyceride. The elimination of the glycerol backbone leads to the formation of the three methyl esters (the biodiesel) and glycerol. The NaOH is reproduced as a product in the reaction. If the biodiesel is removed from the mixture, glycerol and unreacted NaOH and methanol remain. The glycerol can be converted to soap through a saponification reaction if excess NaOH is used. Excessive amount of NaOH will produce a jelly like mix of glycerol and soap. For a basic catalyst, sodium hydroxide (NaOH) or potassium hydroxide (KOH) should be used with methanol or ethanol as well as any kind of oils. Alcoxy is produced before the reaction to obtain a better efficiency. The alcoxi reaction is R-CH2OH + NaOH → H2O + R-CH2ONa The alcohol–oil molar ratio that should be used is 6:1. N = 6:1 is the most used ratio conversion for the alkali catalyst without using a great amount of alcohol. The stoichiometric molar ratio is 3:1. Increasing methanol/oil molar ratio to 6:1 can improve the efficiency of transesterification, which in turn enhances the yield. The percentage yield will decrease if the molar ratio exceeds 6:1. Possible reason to explain this phenomenon is that excessive methanol will increase the solubility of the by-product (glycerol) which might cause a reverse reaction which reduces the yield. Second, excess solute of the by-product might increase the separation difficulty of biodiesel (Azcan and Danisman, 2007). The types of alcohol are usually methanol and
ethanol which is less toxic. As raw materials, the oils used could come from any vegetable, e.g., corn, canola, peanut, sunflower, soybean, olive, palm, or palm kernel. The optimum amount of catalyst that should be added is 1% of the weight of palm oil used. More than 1% will result in lower percentage yield as too much catalyst used may initiate a saponification reaction as stated before. Less than 1% will also bring about lower yield because palm oil may contain trace free fatty acids which is also referred as FFA. Some NaOH catalyst may be neutralised during the transesterification process by those FFA thus resulting in lesser catalyst in reaction. (Lin and Hsiao, 2012) These biofuel is a renewable resource causes less air pollutants except NO 2 emission, biodegradable which is make from non-petroleum or plastic component, nontoxic, safer to handle and less greenhouse gas emissions (B20 can reduce 15% of CO 2 emission). Engines running on biodiesel do not emit black smoke can help to improve current environmental pollution problems. Besides its advantages, it also has weakness or disadvantages. One of them is this fuel is only available for diesel engine only. The price is more expensive while decreasing the engine power respect to the per cent blended. It also increases the emission of nitrogen oxide. Lastly, it not suitable for use in low temperatures because of the blended properties itself.
3.0
METHODOLOGY
3.1
Materials Palm oil, sodium hyroxide, NaOH (99% pure), methanol (99% pure), distilled water
3.2
Apparatus 500mL conical flasks, 500 mL beakers, hot plate, magnetic stirrer, measuring cylinder, aluminium foil, electronic balance, 1L separatory funnel, thermometer
3.3
Experimental Procedure 1. 2.
A beaker is weighed and its value is recorded. 300ml of palm oil is measured and transferred into the beaker to be warm up to
3.
50-55oC while stirred with hot plate magnetic stirrer. About 2.66 g of sodium hydroxide pellets is added into a beaker containing 76.4 ml of methanol and stirred using hot plate magnetic stirrer until all the sodium hydroxide pellets completely dissolve in methanol. *Precaution: Handle this reaction with care as it is corrosive. Avoid contact with skin. Methanol is highly volatile (b.p. 64.7˚C). Do the dissolvation under stagnant place or fume chamber to prevent methanol evaporates to the air and thus the actual amount used will become less.
4.0
4.
The mixture is added into the 50-55oC palm oil and stirring speed of palm oil is
5.
maintained. The beaker is covered with aluminium foil and is stirred continuously for 30
6.
minutes. After 30 minutes, the content is transferred into a separating funnel and is left to
7.
settle the glycerine for 30 minutes. The lower glycerine layer is drained off from the mixture from the opening at the
8. 9.
bottom. The upper layer of crude biodiesel is washed with distilled water and drained off. The content left in the separating funnel is drained into another beaker and
10.
weighed using electronic balance. The value is recorded. The experiment is repeated using 152.8 ml of methanol.
List of Mathematical Equation/Correlations Needed
In order to study the effect of different molar ratio of methanol to palm oil on the conversion to the products, two different molar ratio of methanol to palm oil were used to produce two samples of biodiesel.
Number of Moles of Palm Oilused =
¿
Volume of PalmOil × Dens ity of Palm Oil Molecular Weight of PalmOil
300 × 0.8875 846.1
¿ 0.3147 mol
Sample A (molar ratio of methanol to palm oil = 6:1): Volume of Methanol used
¿
6 × Number of Moles of Palm Oil× Molecular Weight of Methanol Density of Methanol
¿
6 × 0.3147 ×32.04 0.7918 ¿ 76.4 ml
Sample B: (molar ratio of methanol to palm oil = 12:1): Volume of M ethanol used
¿
12 × Number of Moles of PalmOil× Molecular Weight of Methanol Density of Methanol
¿
12 ×0.3147 × 32.04 =152.8 ml 0.7918
* Density of methanol at room temperature (25°C) is 0.7918 g cm−3; Density of palm oil at room temperature (25°C) is 0.8875 g cm−3; Molecular weight of methanol is 32.0381 g mol−1; Average molecular weight of palm oil is 846.1 g mol−1. Weight of NaOH used ¿ Weight of PalmOil ×1
¿ Volume of PalmOil× Density of PalmOil ×1 ¿ 300× 0.8875 ×1
¿ 2.66 g
5.0
Anticipate Results 6:1 has a higher percentage yield
6.0
Identification of Data Needed Methanol-Palm oil Mole Ratio Weight of empty beaker (g) Weight of empty beaker + palm oil (g) Weight of palm oil (g) Weight of empty beaker (g) Weight of empty beaker + biodiesel (g) Weight of biodiesel (g) Percentage yield (%)
Percentage Yield=
7.0
6:1
12:1
Weight of biodiesel( product ) ×100 % Weight of palm oil
Reference Azcan, N. and A. Danisman. (2007). Alkali catalyzed transesterification of cottonseed oil by microwave irradiation. Fuel 86:2639-2644. Wikipedia. (2014). Transesterification. Retrieved November 16, 2014, from http://en.wikipedia.org/wiki/Transesterification Lin, C.C and Hsiao, M.C. (October, 2012). Effects of Catalyst Amount, Reaction Temperature and Methanol/Oil Molar Ratio on Conversion Rate of Soybean Oil
Assisted by Ultrasonic Mixing and Closed Microwave Irradiation. Retrieved 16 November 2014, from www.ijeijournal.com
