The economic importance of alkanes Alkanes are used to obtain finely divided carbon (black carbon) by thermal cracking, The black carbon is produced by heating methane to 1000° C in the absence of air, Black carbon is used in the manufacture of car tires, black painting, polishes, and printing ink. They react to form alkenes and alkanes-So shorter chain alkanes and alkenes are formed. Describe the catalyst used in catalytic cracking. Zeolite catalyst, consisting of silicon dioxide and aluminium oxide honeycomb structure acidic. Catalytic Cracking. Explain the main economic reason why alkanes are cracked (1) To produce substances. Catalytic cracking takes place at a slight pressure, high temperature and in the presence of a zeolite catalyst and is used mainly to produce motor fuels and aromatic hydrocarbons (mechanism not required). Students should be able to: explain the economic reasons for cracking alkanes. Cracking and alkenes is a reaction in which larger saturated are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated: • the original starting hydrocarbons are • the products of cracking include alkanes and, members of a different For example, hexane can be cracked to form butane and ethene: hexane → butane + ethene C 6 H 14 → C 4 H 10 + C 2 H 4 The total number of carbon and hydrogen atoms in the is the same as in the starting alkane. Question C 16 H 34 is an alkane which can be used as the starting chemical in cracking. Uniblue registrybooster 2010 fr serial killer. One of the products of cracking this is an alkane which has 10 carbon atoms in it. Write a balanced symbol equation for this cracking reaction. Reveal answer. Butane and ethene are produced Reasons for cracking Cracking is important for two main reasons: • it helps to match the supply of with the demand for them • it produces alkenes, which are useful as for the industry Supply and demand The supply is how much of a fraction an oil refinery produces. The demand is how much of a fraction customers want to buy. Very often, of produces more of the larger hydrocarbons than can be sold, and less of the smaller hydrocarbons than customers want. Smaller hydrocarbons are more useful as than larger hydrocarbons. Since cracking converts larger hydrocarbons into smaller hydrocarbons, the supply of fuels is improved. This helps to match supply with demand. Alkenes Alkanes and alkenes both form homologous series of hydrocarbons, but: • alkanes are, their carbon atoms are only joined by C-C single bonds • alkenes are, they contain at least one C=C double bond As a result, alkenes are more than alkanes. Alkenes can take part in reactions that alkanes cannot. For example, ethene molecules can react together to form poly(ethene), a. For these reasons. Long chain hydrocarbons undergo a process called CATALYTIC CRACKING. Alkenes are unstable because of their double bonds. As more hydrogen could be added across a double bond. During catalytic cracking alkenes are always produced as there are not enough hydrogen atoms to create two alkanes. Petroleum and Alkanes - Download as PDF File (.pdf), Text File (.txt) or read online. Edexcel AS Chemistry unit 1, Here you will get the idea about PETROLEUM AND ALKANES,Fractional Distillation,Cracking,Combustion. Alkenes will react with bromine water and turn it from orange/brown to colourless. This is the way to test for a double C=C bond in a molecule. In, and, cracking is the process whereby complex such as or long-chain are broken down into simpler molecules such as light hydrocarbons, by the breaking of -carbon in the precursors. The of cracking and the end products are strongly dependent on the and presence of. Cracking is the breakdown of a large into smaller, more useful. Simply put, hydrocarbon cracking is the process of breaking a long-chain of hydrocarbons into short ones. This process might require high temperatures and high pressure. More loosely, outside the field of petroleum chemistry, the term 'cracking' is used to describe any type of splitting of molecules under the influence of heat, catalysts and solvents, such as in processes of. Fluid catalytic cracking produces a high yield of and, while hydrocracking is a major source of,,, and again yields LPG. Contents • • • • • • • • • • • • • History and patents [ ] Among several variants of thermal cracking methods (variously known as the ', ', 'Burton-Humphreys cracking process', and 'Dubbs cracking process'), a Russian engineer, invented and patented the first in 1891 (Russian Empire, patent no. 12926, November 7, 1891). One installation was used to a limited extent in Russia, but development was not followed up. In the first decade of the 20th century the American engineers and Robert E. Humphreys independently developed and patented a similar process as U.S. Patent 1,049,667 on June 8, 1908. Among its advantages was the fact that both the condenser and the boiler were continuously kept under pressure. In its earlier versions it was a batch process, rather than continuous, and many patents were to follow in the USA and Europe, though not all were practical. ![]() ![]() In 1924, a delegation from the American visited Shukhov. Sinclair Oil apparently wished to suggest that the patent of Burton and Humphreys, in use by Standard Oil, was derived from Shukhov's patent for oil cracking, as described in the Russian patent. If that could be established, it could strengthen the hand of rival American companies wishing to invalidate the Burton-Humphreys patent. In the event Shukhov satisfied the Americans that in principle Burton's method closely resembled his 1891 patents, though his own interest in the matter was primarily to establish that 'the Russian oil industry could easily build a cracking apparatus according to any of the described systems without being accused by the Americans of borrowing for free'. At that time, just a few years after the, Russia was desperate to develop industry and earn foreign exchange, so their oil industry eventually did obtain much of their technology from foreign companies, largely American. At about that time, was being explored and developed and soon replaced most of the purely thermal cracking processes in the fossil fuel processing industry. The replacement was not complete; many types of cracking, including pure thermal cracking, still are in use, depending on the nature of the feedstock and the products required to satisfy market demands. Thermal cracking remains important, for example in producing naphtha, gas oil, and coke, and more sophisticated forms of thermal cracking have been developed for various purposes. These include,,. Cracking methodologies [ ] Thermal methods [ ] Thermal cracking was the first category of hydrocarbon cracking to be developed. Thermal cracking is an example of a reaction whose energetics are dominated by (∆S°) rather than by (∆H°) in the Gibbs Free Energy equation ∆G°=∆H°-T∆S°. Although the bond dissociation energy D for a carbon-carbon single bond is relatively high (about 375 kJ/mol) and cracking is highly endothermic, the large positive entropy change resulting from the fragmentation of one large molecule into several smaller pieces, together with the extremely high temperature, makes T∆S° term larger than the ∆H° term, thereby favoring the cracking reaction. [ ] [ – ] Thermal cracking [ ] Modern high-pressure thermal cracking operates at absolute pressures of about 7,000 kPa. An overall process of disproportionation can be observed, where 'light', hydrogen-rich products are formed at the expense of heavier molecules which condense and are depleted of hydrogen. The actual reaction is known as and produces, which are the basis for the economically important production of. [ ] Thermal cracking is currently used to 'upgrade' very heavy fractions or to produce light fractions or distillates, burner fuel and/or. Two extremes of the thermal cracking in terms of product range are represented by the high-temperature process called 'steam cracking' or (ca. 750 °C to 900 °C or higher) which produces valuable and other feedstocks for the petrochemical industry, and the milder-temperature (ca. 500 °C) which can produce, under the right conditions, valuable, a highly crystalline petroleum coke used in the production of for the and industries. [ ] developed one of the earliest thermal cracking processes in 1912 which operated at 700–750 °F (371–399 °C) and an absolute pressure of 90 psi (620 kPa) and was known as the. Shortly thereafter, in 1921,, an employee of the Company, developed a somewhat more advanced thermal cracking process which operated at 750–860 °F (399–460 °C) and was known as the. The Dubbs process was used extensively by many until the early 1940s when catalytic cracking came into use. ![]() [ ] Steam cracking [ ] Steam cracking is a process in which saturated are broken down into smaller, often unsaturated, hydrocarbons. It is the principal industrial method for producing the lighter (or commonly ), including (or ) and (or ). Steam cracker units are facilities in which a feedstock such as naphtha, liquefied petroleum gas (LPG),, or is thermally cracked through the use of steam in a bank of pyrolysis furnaces to produce lighter hydrocarbons. The products obtained depend on the composition of the feed, the hydrocarbon-to-steam ratio, and on the cracking temperature and furnace residence time. In steam cracking, a gaseous or liquid hydrocarbon feed like, or is diluted with steam and briefly heated in a furnace without the presence of oxygen. Typically, the reaction temperature is very high, at around 850 °C, but the reaction is only allowed to take place very briefly. In modern cracking furnaces, the residence time is reduced to milliseconds to improve yield, resulting in gas velocities up to the. After the cracking temperature has been reached, the gas is quickly quenched to stop the reaction in a transfer line or inside a quenching header using quench oil. [ ] The products produced in the reaction depend on the composition of the feed, the hydrocarbon to steam ratio and on the cracking temperature and furnace residence time. Light hydrocarbon feeds such as, LPGs or light give product streams rich in the lighter alkenes, including ethylene, propylene,. Heavier hydrocarbon (full range and heavy naphthas as well as other refinery products) feeds give some of these, but also give products rich in and hydrocarbons suitable for inclusion in.
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