Rapeseed methyl ester
| Rapeseed methyl ester | |||||||
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| other names |
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| Trade names |
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| Brief description | light to dark yellow, oily liquid with a smell of rapeseed oil | ||||||
| Characteristic components |
Fatty acid methyl ester (C16-C18) |
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| CAS number |
67762-38-3 |
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| properties | |||||||
| Physical state | liquid | ||||||
| viscosity |
6.1 mPas (20 ° C) |
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| density |
approx. 0.89 g cm −3 (20 ° C) |
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| calorific value |
approx. 37.1 MJ / kg (10.3 kWh / kg) |
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| Melting range | -17 ... -16 ° C | ||||||
| Boiling range |
345 ... 354 ° C |
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| Flash point |
173 ° C ( closed cup ) |
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| Ignition temperature | 256 ... 266 ° C | ||||||
| Temperature class | T3 | ||||||
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | |||||||
Rapeseed methyl ester (RME; also rapeseed oil methyl ester or colloquially rapeseed diesel ) is a mixture of methyl esters consisting of saturated and unsaturated fatty acids , each with 16 to 18 carbon atoms. By chemically converting refined rapeseed oil with methanol, rapeseed methyl ester is obtained as a clear, thin, flammable and water-insoluble liquid. In Europe, the RME obtained from rapeseed represents the largest proportion of biodiesel . RME based on fully refined products is also used as a solvent in industrial production .
Manufacturing
When methanol is added to the rapeseed oil in transesterification plants , the rapeseed methyl ester is produced through a catalytic reaction ; Another product is raw glycerine, which is processed into pharmaceutical glycerine through further purification and distillation . The RME formation takes place according to the following reaction equation:
Pretreatment of the rapeseed oil
After the initial and auxiliary products have been delivered, the rapeseed oil used is cleaned. First, the crude oil is deacidified by adding phosphoric acid with elimination of phosphatides. This creates mucilage, the so-called rapeseed soap, which is separated from the oil with the help of a centrifuge . In the next process step, the remaining soap is washed out of the neutralized oil and then dried in a vacuum dryer . Before the crude oil is put into a washing centrifuge, caustic soda is added. In this way, the previously added phosphoric acid and the remaining fatty acids are completely neutralized . Following centrifugation, the slimy substances are separated off in a separator .
Transesterification process
The main process of RME production, transesterification , is based on the chemical reaction of triglycerides with methanol to form methyl esters and glycerine, which is accelerated in the presence of an alkaline catalyst. The transesterification takes place in two reactors connected in series, each of which is provided with different reaction chambers in order to achieve the highest possible conversion to methyl esters. Both methanol and the catalyst sodium methylate are fed to the reactors in parallel . At normal pressure and temperatures around 60 ° C in the 1st reactor and around 50 ° C in the 2nd reactor, the ester bonds of the triglycerides in rapeseed oil are cleaved. With the help of phase separators , RME and glycerine can be separated from one another due to their different densities .
Cleaning the product
The phase with the ester also contains methanol, glycerine, catalysts, soaps and other components. The water-soluble substances are removed by a washing process with the addition of catalysts such as sulfuric or hydrochloric acid, before the RME is then dried in vacuum dryers and is finally available for economic recycling. The remaining free methanol is worked up and fed back into the process, the separated glycerine as a by-product is also processed.
Areas of application
RME has a significantly lower viscosity than untreated rapeseed oil; therefore it can be used as biodiesel instead of mineral diesel fuel without having to modify the engine . However, the plastic parts that come into contact with fuel must be resistant to biodiesel. Around 80% of the biodiesel produced in Germany is made from rapeseed oil and 20% from soybean oil ( soy methyl ester ).
In the manufacture of engine and transmission housings in the automotive industry , molds are used that are made from molding sand and resins. For this so-called cold box system, RME can be used on a larger scale as a binder for the resin component. This enables emissions of problematic solvents in the BTX fraction (benzene, toluene and xylene) to be reduced; Furthermore, the use of RME should also lead to technical advantages compared to conventional cold box systems.
In the future, RME could copy papers as a substitute for other solvents provide the necessary color reaction, as well as the connecting material in road construction are used.
swell
- Areas of application of RME ( Memento from February 2, 2012 in the Internet Archive )
- Germany's biodiesel capacity is growing rapidly - biodiesel, a fuel with a promising future (PDF; 126 kB)
- School trial: production of RME
- Martin Kaltschmitt, Hans Hartmann and Hermann Hofbauer (eds.): Energy from biomass. Basics, techniques and procedures. 2nd edition, Springer Verlag, 2009, ISBN 978-3-540-85094-6 , pp. 736-745.
Individual evidence
- ↑ a b c d e f g h i j k Entry on fatty acids, C16-18 and C18 unsaturated, methyl esters in the GESTIS substance database of the IFA , accessed on November 20, 2017(JavaScript required) .
- ↑ Guido A. Reinhardt: Energy and CO2 accounting for renewable raw materials. 2nd Edition. Springer-Verlag, Wiesbaden 1993, ISBN 978-3-322-91770-6 , p. 152 ( limited preview in the Google book search).
- ↑ John Fresner: resource efficiency in production. 2nd Edition. Symposion Publishing GmbH, Düsseldorf 2014, ISBN 978-3-86329-629-2 , p. 135 ( limited preview in the Google book search).
- ^ Ulrich Hampicke: Cultural landscape and nature conservation. Problems - Concepts - Economy. Springer-Verlag, Wiesbaden 2013, ISBN 978-3-8348-8236-3 , p. 262 ( limited preview in the Google book search).
- ^ Association of the German Biofuel Industry eV: Page no longer available , search in web archives: German producers only use sustainably produced soy. ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. Press release from April 2, 2008.
