VEL TECH HIGH TECH DR.RR & DR.SR ENGINEERING COLLEGE Alternative Fuel Sources For Diesel Engines Purushothaman E Viswanathan V Purushothaman E Viswanathan V (Mechanical 3 rd Year)

Contents Introduction Diesel Problems due to Diesel Bio-diesel over Diesel fuel Bio-mass  Transesterification KOH, a homogenous catalyst Conclusion

Introduction At present situation, the world is on the lookout for fuels for their vehicles which are more eco-friendly than the existing fuels. Incidentally, Rudolf Diesel,the man who invented the diesel engine, in 1912 said, "the use of vegetable oils for engine fuels may seem insignificant today but such oils may become, in the course of time, as important as petroleum and the coal-tar products of the present time."

Diesel Diesel fuel in general is any liquid fuel used in diesel engines. The most common is a specific fractional distillate of petroleum fuel oil, but alternatives that are not derived from petroleum, such as biodiesel, biomass to liquid (BTL) or gas to liquid (GTL) diesel, are increasingly being developed and adopted. To distinguish these types, petroleum-derived diesel is increasingly called petrodiesel.Ultra-low sulfur diesel (ULSD) is a standard for defining diesel fuel with substantially lowered sulfur contents.

Problems due to Diesel Spillage Reduce tire grip and traction.. Environment Smoke of diesel car is injurious to health and the toxicants emitted hamper the ozone layer of the atmosphere. Dirtiness If spilled, the fuel takes longer to evaporate thus providing ample of time for dust and mud settlement. Noise Though the technology has advanced, diesel engine still remains louder than petrol.

Bio-diesel over Diesel fuel Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics. It can be used in most diesel engines, especially newer ones, and emits less air pollutants and greenhouse gases other than nitrogen oxides. It’s safer to handle and has virtually the same energy efficiency as petroleum diesel. In addition it has lubricity benefits that fossil fuels do not. Biodiesel blends as low as B2 have been found to significantly reduce the amount of toxic carbon- based emissions.

With the soaring price of petroleum-based products, Biodiesel is becoming an increasingly affordable option relative to petroleum diesel. The use of Biodiesel helps reduce dependence on finite fossil fuel reserves.

Transesterification Biodiesel is produced by chemically reacting a fat or oil with an alcohol, in the presenceof a catalyst. which are known as biodiesel, and glycerol, which is a high value co-product. The process is known as transesterification.The product of the reaction is a mixture of methyl esters, which are known as biodiesel, and glycerol, which is a high value co-product. The process is known as transesterification.

In the transesterification of vegetable oils triglyceride reacts with an alcohol in the presence of a strong acid or base, producing a mixture of fatty acids alkyl esters and glycerol.In the transesterification of vegetable oils triglyceride reacts with an alcohol in the presence of a strong acid or base, producing a mixture of fatty acids alkyl esters and glycerol.

The overall process is a sequence of three consecutive and reversible reactions, in which di and mono glycerides are formed asThe overall process is a sequence of three consecutive and reversible reactions, in which di and mono glycerides are formed as intermediates. The stoichiometric reaction requires 1 mol of a triglyceride and 3 mols of the alcohol.

KOH,a homogenous catalyst Alkaline metal hydroxides (KOH and NaOH) are cheaper than metal alkoxides, but less active. Nevertheless, they are a good alternative since they can give the same high conversions of vegetable oils just by increasing the catalyst concentration to 1 or 2 mol%. However, even if a water-free alcohol/oil mixture is used, some water is produced in the system by the reaction of the hydroxide with the alcohol. The presence of water gives rise to hydrolysis of some of the produced ester, with consequent soap formation.

Need for Heterogeneous Catalyst Nowadays the production of bio-diesel is done by mixing a homogeneous catalyst with vegetable oil. The homogeneous catalysts used at present (KOH) is quite corrosive in nature. So when KOH is mixed with vegetable oil in a cylindrical container,it corrodes the inner layers of the wall. When an alkali catalyst is added, the free fatty acids react with the catalyst to form soap and water. To avoid catalyst removal operations and soap formation, much effort has been expended on the search for solid acid or basic catalysts that could be used in a heterogeneous catalyzed process.

Some solid metal oxides such as those of tin, magnesium, and zinc are some of the known catalysts but they actually act according to a homogeneous mechanism and end up as metal soaps or metal glycerates.

Conclusion Biodiesel is an important new alternative transportation fuel. Conventional processing involves an alkali catalyzed process but this is unsatisfactory for lower cost high free fatty acid feedstocks due to soap formation. Adherence to a quality standard is essential for proper performance of the fuel in the engine and will be necessary for widespread use of biodiesel.

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