What are the benefits of anti-knock drugs

Big Bang HTL 3, textbook

106 Organic Technology and Ecology (3rd year, 6th semester) 11.3.4 Refinement 2. Catalytic reforming (improving the product) The reforming process is used to produce even higher quality gasoline components. Primary gasoline is heated to 500 ° C and fed into a reactor. There a platinum-containing catalyst causes various transformation reactions in the hydrocarbon molecules. Because of the platinum, the process is also called “platforming”. The following types of reaction take place: Isomerization: z. B. heptane → 2,3 dimethylpentane cyclization: e.g. E.g. hexane → (-H 2) → cyclohexane dehydrogenation: e.g. B. Cyclohexane → (–3H 2) → Benzene Linear alkanes produce branched, aromatic and cyclic hydrocarbons. These have significantly higher octane numbers than unbranched ones. Reformat gasoline (OZ approx. 85–95) is therefore mixed with the gasoline from the primary distillation (OZ approx. 35–45) in order to increase the octane number. 3. Additives (improving the product) In order to improve the quality of the gasoline even further, substances have been found which, even in small amounts (as additives), can greatly increase the knock resistance. MTBE: methyl tert-butyl ether (IUPAC name: 2-methoxy-2-methylpropane), is currently the anti-knock agent of choice. It is easy to manufacture, has little tendency to form peroxide, and has an octane number of 118. Approx. 5% is mixed with gasoline. ETBE: Ethyl tert-butyl ether has a similar structure to MTBE and also has similar properties. Its advantage, however, is that it can be partially produced from renewable sources, in this case ethanol. ETBE can therefore be classified as a "biofuel admixture" to almost 50%. However, it is more expensive than pure ethanol (which can also be used as an anti-knock agent due to its high OZ), which is why it is only used when high octane numbers are to be achieved. Fig. 11.18: Production of ETBE Fig. 11.17: MTBE fuel production Place the correct structural formulas of all molecules involved for the aforementioned isomerization, cyclization and dehydrogenation reactions. L 11.3 F15 B1 The gasoline engine and knocking In a gasoline engine, gaseous mixtures of gasoline and air should be burned as completely as possible. To do this, the mixtures must be compressed and ignited by the spark plug at maximum compression. If the gasoline is of a low quality, it tends to ignite by itself due to the strong warming during compression. The consequences are irregular combustion and a knocking noise from the engine. This knocking leads to damage to the engine, so it is important to fill up with fuel that is as resistant to knocking as possible. The measure of the knock resistance of a gasoline mixture is the octane number (OZ). The higher the OZ, the better the gasoline. To establish an octane number scale, two substances have been selected as reference points: heptane as a substance with low knock resistance (ie high tendency to knock), receives OZ = 0, and iso-octane (actually 2,2,4-trimethylpene - tan) with high knock resistance (i.e. low tendency to knock) receives OZ = 100. A mixture of 91% iso-octane and 9% heptane accordingly receives OZ = 91. (Regular petrol at the petrol station) Every fuel mixture that comes onto the market is now tested for its knock resistance in test engines. If it behaves like a mixture of 95% iso-octane and 5% heptane, it has an octane number of 95 and can be sold as super gasoline. Super gasoline does not consist of 95% iso-octane and 5% heptane, it just behaves in the same way as this mixture. (F14) Depending on the type and compression of the engine, there is the optimal fuel variant. If you refuel with a lower octane number than prescribed, you risk a reduction in performance or, in the worst case, engine damage. If you refuel higher octane numbers than prescribed, however, this does not lead to higher performance, it is just more expensive. i For testing purposes only - property of the publisher öbv

Made with FlippingBook