HYDROCARBON

 HYDROCARBON 

-Hydrocarbon And Its Main Class

Hydrocarbon and its Main Classes

The name hydrocarbon‘ is derived from the two elements - hydrogen and carbon. Hydrocarbons are organic compounds that contains only carbon and hydrogen. Some examples of hydrocarbons are; methane, CH4; Propane, C3H5; butane, C4H8; benzene, C6H6. Hydrocarbons are classified

into two groups. They are; the aliphatic and the aromatic hydrocarbons. Aliphatic hydrocarbon are composed of carbon chains. Aliphatic compounds with either straight or branched chain hydrocarbons are also called the acyclic compounds. Aliphatic compounds where the end

carbons atoms join together to form rings are known as cyclic compound. Aromatic hydrocarbons are all cyclic compounds that contain benzene ring. They have sweet odour and are used in the manufacture of perfume. Examples of aliphatic hydrocarbon are; alkanes, alkenes and alkynes

Examples of aromatic hydrocarbons are; benzene, toluene, naphthalene

PETROLEUM

 Origin and Composition of Crude Oil

The term petroleum is made up of two words; petra meaning rock and 'oleum' meaning oil. It is usually applied to dark coloured oily liquid found below the earth's crust. It is obtained by the process of mining. Petroleum is therefore known as mineral oil or crude oil. The petroleum industry came into existence in the year 1959 when Col. Edwin L. Drake drilled the first well after finding the oil at Titrusville, Pennylvania in U.S.A. Crude oil or petroleum is a mixture of many hydrocarbons. It is believed to have been formed from the decay of dead marine plants and animals at the bottom of sea. The remains of these equatic plants and animals were covered with many layers of the earth. They were subjected to high temperature and pressure. Then after many thousands and millions of years, these plants and animals remains were converted into petroleum and natural gas. The sea water contains the crude oil (mixture of hydrocarbons). The marine plants and animals absorb and drink the sea water respectively. The hydrocarbons in the seawater are therefore incorporated into the tissues and cells of these aquatic organisms. When the aquatic plants and animals die and thier remains decay, the hydrocarbons in their body are converted to petroleum or crude oil after many years. Hydrocarbons are organic compounds composed of only two elements-carbon and hydrogen. The main source of hydrocarbons is crude oil. Petroleum or crude oil is a mixture of many hydrocarbons. The hydrocarbons include the gaseous, liquid and solid alkanes, alkenes, cycloakanes, aromatic hydrocarbons and others. Natural gas consists mainly of methane.

Nigerian and World Crude Oil Reserves

Nigeria is among the top ten oil producers of the world. Crude oil was recently found in Otu-Aguleri in Anambra State of Nigeria. On 30th of August 2012, the President, Goodluck Jonathan Ebele Azikiwe commissioned Oleum Petroleum Industry at Otu-Aguleri. He declared Anambra State as the tenth (10th) oil producing state in Nigeria. Since 1956, when crude oil was first discovered at Olobiri, Nigeria has acquired much money from it. Large deposits of oil have been found in the Niger delta-Afam, Abata, Egbema, ughelli, Owaza and Bornu. Crude oil was also found in calabar and Burutu (Delta State). Crude oil is pumped from these areas through pipelines to the oil terminals at Bonny or Forcados for export. The oil is refined outside Nigeria because Nigerian oil refineries are presently not functional. Nigerian oil refineries are located at Port-Harcourt, Warri and Kaduna.

China and Asia are two Asia countries that are rich in crude oil. Asia has about three-fifths of the world's oil reserves but most of it are found in the Middle East. Russia has the next largest oil reserves. Other important oil reserves are found in United states, Canada, Australia, Venezuela, Northern and Western Africa.

Exploration and Drilling of Crude Oil

Petroleum occurs naturally as a dark, viscous liquid in huge subterranean deposits in many countries of the world such as Nigeria, Egypt, Russia Kuwait, U.S.A., Saudi Arabia, Iran, Iraq, Venezuela, Mexico, Rummania etc. Crude oil is generally found under the rocky starata of the earth‘s crust, trapped deep bellow. A certain amount of gas called ―natural gas‖ is associated with the oil.

Coarse grained rock layers or oil-bearing rock layers are explored or located by:

· Aerial photography

· Examining the surface rocks,

· Core drilling and

· Mapping the earth's rock layers.

Geologists do the mapping by exploding dynamite in deep holes in the earth's crust to detest possible oil-bearing areas. Crude oil is extracted by drilling deep holes or wells into the ground when a well reaches any oil-bearing layer, crude oil and natural gas may rise suddenly into the air under pressure. The crude oil then is pumped out and stored in large steel tanks. It is then sent to oil refineries by pipelines or tankers.

[ Earth surface         surface strata       Fine grained rock        Coarse grained rock         Fine grained rock ]

 Fractional Distillation of Petroleum and Major Products

Petroleum or crude oil is said to be a mixture of many hydrocarbon. It also contains 1% of sulphur compounds and traces of oxygen and nitrogen compounds. Fractional distillation technique is used in separating mixture of liquids with boiling points that are close together. This method is applied in the purification of crude oil since it is a liquid mixture containing many hydrocarbons with relatively close boiling points. Petroleum contains some very important hydrocarbons like kerosene, petrol, engine oil, gas oil, bitumen, lubricating oil etc. these products are separated by fractional distillation. The crude oil is heated at the furnace. It vaporizes and enters into the fractionating column where the real separation occurs. The column is cooler at the top than at the bottom. Thus the higher the vapour mixtures rises in the column the faster it condenses. The different components or fractions are taken out from different levels (outlets) of the tower.

No	Fraction	Boiling point 0oC	Carbon atom in molecule	USES
1	Petroleum gas	Below 40	1-4	Fuel and manufacture of other organic compound
2	Petrol	40-200	4-12	Fuel in aeroplane and motor vehicle
3	kerosene	200-250	12-18	Fuel for lighting, heating and jet engine
4	Gas oil and diesel oil	250-350	12-25	Fuel for heating and diesel engine. Raw materials for cracking process
5	Lubricating oil	350- 500	More than 20	Lubricating moving parts of a machine and cosmetics
6	Paraffin wax		About 30	Ointment and candles
7	Bitumen	Viscous liquid	More than 35	Surfacing road
8	Residue	Solid		Fuel and protective paint.

 

 Petrochemicals

Petroleum or crude oil was originally used as a source of fuels but in 1930 and 1950 in the U.S,A and European countries, it started to be a very important source of many individual chemicals.

The term 'Petrochemicals' is applied to those numerous organic chemicals that are derived from petroleum sources. Petroleum are produced either from natural gas or any of the fractions obtained during the refining of crude oil. Today petroleum has assumed a supreme position as a potent source of a very large number of organic compounds required for industry.

Petrochemicals are chemicals that are chemicals derived from petroleum and natural gas. These chemicals are of great importance to chemical industries. Such essential chemicals include benzene, phenol, methane, ethane, propane, butane, ethane, butane etc. These chemicals are also used in the production of a wide variety of other useful chemicals. Carbon black is easily obtained at the top of a burning kerosene lamp. Carbon black is important as an essential ingredient in the making of tires and in the manufacturing of printer's ink.

Benzene is used in the making of synthetic detergents. The petrochemicals known as butadiene and styrene are used in the making of synthetic rubber. The petrochemicals called polythene is used in making of plastic materials like polythene bags, plastic buckets, balls, spoons, plates, tables, chairs etc. Petrochemicals are used in the manufacture of a lot of other products like body pomade, polishes, disinfectants, insecticides, herbicides, shampoo, hand lotions, body cream, lipsticks, rouge, stain removers and drugs. The formulae and structure of some of the petrochemicals used in the manufacturing of synthetic detergents are as follows.

 Cracking; Polymerization; Reformation; Octane Rating

The first stage in refining of petroleum is the separation of petroleum into various components (fractions) by fractional distillation. All the conversion is the second stage in the refining process. It involves three main processes namely: (i) Cracking (ii) Polymerization and (iii) Reformation.

These processes are designed to convert unwanted fractions into the products in high demand.

Cracking is the breaking of the complex fraction into smaller or simpler fractions that are in high demand. This is brought about by subjecting the complex fraction to high temperature and pressure often in the presence of a catalyst. Eg Gas oil fraction is cracked to yield more petrol.

C15H30             C8H18 + C3H6

Two types of cracking are:

(i) Thermal cracking and (ii) Catalytic cracking

Thermal Cracking is the breaking of the complex fraction into smaller units by heating it to high temperature up to 700oC and high pressure of about atmosphere.

Catalytic Cracking is the breaking of the complex fraction by heating it in the presence of a catalyst at a reduced temperature and pressure. Examples of such catalyst are: Silica alumina and a mixture of silicon (iv) oxide and aluminum oxide.

Polymerization involves joining small molecules of hydrocarbon gases in the C1 – C4 range to produce molecules in the C5 – C10 range. Both cracking and polymerization are used to increase the yield of petrol from crude oil.

Reformation is the rearrangement of carbon atoms in a molecule. Reformation is used to improve the quality of petrol by changing linear or straight chain alkanes to branched chain and cyclic hydrocarbon which yield better or high performance fuel.

In the process of reforming, the gasoline is heated to a temperature of about 600oC for a very short time, in presence of a platinum catalyst. The pressure (28-50 atmosphere) is maintained in such a way that molecules do not crack but are reformed. The straight chain hydrocarbons may be converted to branched chain hydrocarbons by Isomerisation or Alkylation; alkanes to cycloalkanes and cycloalkanes to aromatic hydrocarbons. The overall effect is increase of octane number of the fuel and the process is known as reforming. Reforming carried out in the presence of hydrogen is known as hydroforming

Octane rating: Petrol is a hydrocarbon containing carbon in the C5-C10 range. The major compounds in petrol are C7 (Heptane) and C8 (Octane) hydrocarbon. These hydrocarbons may occur as straight chain or branched chain molecules as in OR Octane rating of petrol is a measure of its performance in an internal combustion engine. Straight chain alkanes do not burn smoothly in internal combustion engines. They burn rapidly and unevenly, and generate an explosion which disturbs the up and down movement of pistons in the engine. This causes a strange sound, usually referred to as 'engine knock'. Octane number is the percentage of 2,2,4-trimethyly pentane in a petrol or fuel. For example, the petrol with an octane number of 90, means that the fuel is made up of 90% 2,2,4-trimethyly pentane and 10% normal heptanes. A fuel which contains only the straight chain hydrocarbon (n-heptane) is a very poor quality fuel and its octane number is zero. Thus higher grade petrols are said to have a high octane rating or number. Motor vehicles run well on petrol with a high octane rating of about 80-90.

Ethyl fluid and methyl fluid are added to petrol as an antiknock compounds. They raise the octane rating of petrol. Ethyl fluid is a mixture of tetraethyl lead (iv) (TEL), Pb (C2H5)4 (60%), Dibromo ethane, (26%), Dichloro ethane (9%) and a red dye (2%). Methyl fluid is a mixture of tetramethyl lead (iv) (TML), Pb (CH3)4 (60%), Dibromomethane (26%), Dichloro-methane (9%) and the red dye (2%). 1-3ml of these mixtures (Ethyl fluid or methyl fluid) is added to a gallon of petrol to increase its antiknock properties. HYDROCARBON – I