oil and its derivates

Transcription

1 speech transcript Liceo Scientifico Isaac Newton oil and its derivates in accordo con il Ministero dell Istruzione, Università, Ricerca e sulla base delle Politiche Linguistiche della Commissione Europea percorso formativo a carattere tematico- linguistico- didattico- metodologico scuola secondaria di secondo grado professor Luciana Leonzi eniscuola / smartenglish A cura di Linda Rossi Holden Label europeo

2 1 oil and its derivates speech transcript Oil and its derivates In this video we will talk about petroleum and oil derivates. Petroleum is not only fuel. The association with the oil derivates is not always immediate. Petrol is used to make the sail of boat, the tractor of child, antibiotic pills and insulin, a pair of tights or vaseline jelly. To name just a few. There are in fact huge number of oil derivates in the world that surrounds us. Let s now a look into the processes that make such a vast and amazing transformation possible. Chemical composition of crude oil Crude oil or petroleum is a viscous, liquid mixture of hundreds of hydrocarbons and small amounts of other organic compounds, containing oxygen, nitrogen and sulfur. Its density and relative amounts of hydrocarbons depend on the oil field (of origin). The oil elements are shown in the table. Paraffins or alkanes The most abundant species of hydrocarbons in petroleum are paraffins or alkanes (formula: C n H 2n+2 ). Their properties are: a single σ covalent bond between carbon atoms, so they are called saturated hydrocarbons; their molecules are formed by straight or branched chains; can be found in gaseous, liquid or solid state at room temperature. The simplest alkanes are methane, ethane, propane. Naphthenes or cycloalkanes (C n H 2n ) The second type of hydrocarbons are naphthene or cycloalkanes, that present structures with one or more rings, a single covalent bond between the Carbon atoms, therefore they are called saturated hydrocarbons, and they are liquid at room temperature. (Two examples: Cyclohexane C 6 H 12 and Methylcyclohexane C 6 H 11 CH 3. ) Aromatic Hydrocarbons C 6 H 5 - R The last series of hydrocarbons, present in oil, are aromatic hydrocarbons, characterized by the σ covalent bond and π delocalized bond; (structures with one or more rings) typically liquid at room temperature. The simplest aromatic hydrocarbon is benzene (C 6 H 6 ). Toluene is another example of aromatic hydrocarbon. Crude oil extraction After drilling through the overlying rock, the crude oil rises to the surface, pushed back by the pressure of the gases in the oil field, and afterwards by pumps. Water is injected into the oil well to keep a constant internal pressure; in some cases gas and vapor are used to decrease the viscosity of the oil, and to allow a more rapid release. Crude oil refining Crude oil is of little use in its raw state, unlike its derivates, that are widely exploited for energy production, for transport and in the chemical industry.

3 Refining process The oil derivates are produced through the refining process that includes: fractional distillation, that separates the oil components; cracking, that increases the yield of some oil fractions; reforming, that improves the quality of gasoline and produces substances that will be raw material for the chemical industry. Fractional Distillation In the case of fractional distillation at atmospheric pressure, crude oil is heated in the boiler to 400 C. The vapors are piped into the distilling column, where temperature decreases upward and pressure is slightly above atmospheric pressure. When each substance in the vapor state reaches a height where the temperature of the column is equal to its boiling point, it condenses to form a liquid. The liquid is collected by one of the trays of the column and, from here, can go to storage tanks. The distillation under vacuum. The hydrocarbons of residue from atmospheric fractional distillation degrade before reaching their boiling point. To avoid this, the residue is piped to a second distillation column. where the process is repeated under vacuum (at pressure of 40mmHg and at lower temperatures). The products of fractional distillation Petroleum gas (1 to 4 C) (methane, ethane, propane, butane) used for heating, cooking and making plastics; Naphtha (5 to 9 C) (further processed) to make gasoline; Gasoline (5 to 10 C) for motor fuel; Kerosene (10 to 18 C) fuel for jet engines and tractors, (feedstock for other products); Gas oil or diesel distillate used for diesel fuel and heating oil; (feedstock for other products); Heavy gas or fuel oil used for industrial fuel; (feedstock for other products); Lubricating oil, used for motor oil, grease, other lubricants; Residuals, lubricating oils, coke, asphalt, tar, waxes; (feedstock for other products). Cracking The cracking breaks the σ bond between the carbon atoms of long chains of hydrocarbons, producing mixtures of shorter chain alkanes and alkenes. As shown in the equation of the example, dodecane molecule is broken in hexane and 1-hexene. The cleavage of the σ bond can occur in two different ways. By homolytic fission: the two electrons of covalent bond are divided between the carbon atoms, with radicals production. By heterolytic fission: both electrons are retained by one of the two carbon atoms united by covalent bond. This produces carbocations. (Cracking)

4 Due to the high stability of σ bond between carbon atoms, the process takes place at high temperatures ( C) or in the presence of catalysts (zeolite, aluminum hydrosilicate, bauxite and silica-alumina). Through Cracking : the components of residue from the distillation are cracked into light oil, gasoline, naphtha and kerosene; the molecules of ethane, butane, and naphtha are broken into ethylene and benzene, used for making plastics; the viscosity of heavy oils is reduced so that they can be blended with lighter fuel oil tar is produced; the residue of the process is a heavy, almost pure, carbon. REFORMING During reforming molecules of paraffins (6 9 carbon atoms) are transformed into isoparaffins and naphthenes; naphthenes to aromatic compounds, keeping the same number of atoms of carbon, as shown in the conversion of exane in benzene. The reforming reactions take place at high temperature, high pressure and in the presence of catalysts (platinum). Reforming Another example of reforming is the conversion of heptane into toluene. Hydrogen, produced by the reaction, is used for hydrocraking, for petroleum desulphurization and to maintain constant pressure during the reaction. Isomerization The value of isomerization in petroleum refining is twofold: can convert unbranched paraffins into isoparaffins, thus increasing the octane rating of the gasoline fraction, improving its anti-knock properties; isoparaffins such as isobutane thus produced can also be alkylated to liquid hydrocarbons in the gasoline range. Refining products After the refining process, oil fractions are cooled and then blended together to make various products, such as: gasoline of various grades, with or without additives lubricating oils of various weights and grades (e.g. 10W-40, 5W-30) kerosene of various grades jet fuel diesel fuel heating oil Bitumen chemicals of various grades for making plastics and other polymers. Polymerization Petroleum constituents, containing fewer than five carbon atoms, can be converted to higher molecular weight hydrocarbons via acid-catalyzed polymerization. The linear polymers form thermoplastic resins or unvulcanized elastomers, threedimensional polymers form thermosetting resins or vulcanized elastomers.

5 Polymerization of polyethene During the polymerization reaction, the π bond of double bond between the carbon atoms is broken, so that the molecules of ethene can bind to each other: n CH 2 =CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 - ethene polyethene Polyethene constitutes the 40% of the total volume of the world production of plastics. One of its polymer can contain between 3 and 6 million monomers. According to the degree of polymerization, it can be a more or less viscous liquid or waxy more o less hard mass. This explains the great variety of made of polythene. The entire manufacturing cycle Here is an example of the entire manufacturing cycle. In particularly, we can see how, through refinery, cracking, polymerization and transformation, certain plastic materials can be obtained from short chain alkenes and aromatic hydrocarbons benzene, toluene, and xylene. Hydrocarbons and energy Combustion is the most common reaction connected to the use the majority of the derivates. The combustion of hydrocarbons, a redox reaction, is highly exothermic. As we can see with the combustion of methane, ΔG of the reaction, in fact, has negative sign (This reaction releases 802KJ for mole). The peack oil The graph shows the trend in global oil production. As we can see, the peak oil was reached around So at present we re currently using more than we can extract. The theory of peak oil was made by Hubbert in Not everyone agrees the peak has been reached, because technology improvements make possible to extract greater quantities of oil. Materiale sviluppato da eniscuola nell ambito del protocollo d intesa con il MIUR