Fatty acid methyl ester
Fatty acid methyl esters ( FAME abbreviated from English- fatty acid methyl ester ) are compounds of fatty acid and the alcohol methanol. A mixture of FAMEs that is of vegetable or animal fats (e.g., rapeseed oil) obtained and used as fuel for diesel engines is referred to as biodiesel.
Properties
FAME from vegetable fats are liquid at room temperature and come up with some of their properties to those of diesel fuel very close (hence the term "biodiesel" ), but are also solvent effects other than diesel fuel, which can lead to technical problems of sealing materials in motor systems. Fatty acid methyl esters can be used as an alternative fuel, when the sealing materials are resistant to FAME.
The storage of FAME should with as little oxygen as possible take place since FAME responding because of the partially contained double bonds in the carbon chains of unsaturated fatty acids with oxygen from the air and gummy by the formation of bridges between the individual molecules. If FAME are used as fuel, it is necessary to obtain a high quality standard. The iodine value is a measure for the tendency to formation of resin, since it is proportional to the existing carbon-carbon double bonds. Fatty acid methyl esters with high iodine resinify therefore lighter than those with low iodine value.
Production
Fatty acid methyl esters (FAME ) can be prepared by transesterification of fats or oils (triglycerides ) with methanol. This reaction is catalyzed acidic or basic. Here, the trivalent alcohol glycerol is replaced with methanol. This results glycerol and FAME as reaction products, in which, with the use of natural fats, is always a mixture of various fatty acid methyl esters, is obtained ( with an even number of carbon atoms), as natural triglycerides generally include several different fatty acid residues.
In the art, the equilibrium of the transesterification reaction, by removing the glycerol, or by an excess of the alcohol ( methanol) on the product side, so the side of the fatty acid methyl esters moved.
FAME may also be prepared by esterification of fatty acids produced artificially. However, this route is a minor player in the industry. As one of the largest producers of FAME biodiesel production, the proportion of FAME from purely synthetic fatty acids is always lower. A variant with also less technical importance is the specific enzymatic transesterification by special 1.3 - lipases. This specificity is not chemically and finds use in the production of cocoa butter set, margarine, butter and shortenings.
Use
Fatty acid methyl esters are now used primarily for the production of biodiesel and can be used as a pure fuel, as well as any mixtures with conventional diesel fuel. The fatty acid methyl esters must be as a mixing component for diesel satisfy certain well-defined quality parameters, which are defined in the standard DIN EN 14214.
FAME have a much lower viscosity than untreated vegetable oil; Therefore, it can be used as a replacement for mineral diesel fuel, without the diesel engine needs to be adjusted. However, coming into contact with fuel fuel system components such as hoses and seals against the methyl esters must be resistant and made of polytetrafluoroethylene ( Teflon) or fluorine rubber ( eg Viton ) exist. The solvent properties of FAME can lead to a solution of diesel residues in the fuel system and thereby clog the fuel filter, as well as biodiesel can attack painted surfaces. Further problems may arise due to accumulation of bio-diesel in the engine oil, which helps shorten oil change intervals are necessary.
From FAME can also fatty alcohols and fatty amines, for example, used in the manufacture of surfactants and emulsifiers, are produced. In the production of motor and transmission housings in automobile molds are used, which are formed of the molding sand and resins. For this so-called cold-box system is SME, but also RME ( rapeseed methyl ester ) used in a larger scale than the binder resin component. This emissions of problematic solvents of the BTX fraction can be reduced (benzene, toluene and xylene ); continue to the methyl ester use also lead to technical advantages over the classical cold box systems.
The most common fatty acid methyl esters for biodiesel production are soybean oil methyl ester (SME; especially in North and South America, imported into Europe), rapeseed methyl ester (RME, especially in Central Europe ), palm oil methyl ester ( PME) and the fatty acid methyl esters derived from animal fats (FME ). FAME from the oil of the physic nut (Jatropha curcas ) and other oils are currently under development but are not yet used on a large scale.
Sulfonated fatty acid methyl esters are used as anionic surfactants, such as the α - methyl ester sulfonate (MES).