CRUDE OIL
Impact of the Crude Oil Industry on the Environment (Carbon monoxide)
Carbon monoxide is toxic because it combines readily with haemoglobin in the blood to form the stable compound carboxyhaemoglobin. This makes the haemoglobin unable to transport oxygen which results in the cells of the body being deprived of oxygen. A concentration as little as 400 ppm in the air can be fatal.
What is catalytic cracking used for?
Catalystic cracking is used to crack the distilled fractions such as diesel oil and kerosene into smaller molecules. The cracked compounds are important to produce a more valuble fuel as well as chemical feedstock for the petrochemical industry. The alkenes are suitable starting materialsto make plastics, detergents, cosmetics, solvents, paint and many other petrochemicals.
Refinery gas (composition, boiling range, carbon length and use(s))
Composition: 1-2% of crude oil. The boiling Range is <5⁰C (less than) Carbon length: C₁-C₄ carbon chain Uses: Used as gaseous fuel in heating appliances, can be liquified under pressure to produce liquified petroleum gas (LPG) for domestic use, e.g. cooking, refrigerant, aerosol propellant, feedstock for making petrochemcals.
Diesel (gas oil) (composition, boiling range, carbon length and use(s))
Composition: 15-20% of crude oil. Boiling range is 260-340⁰C Carbon length: C₁₄-C₂₀ carbon chain Uses: used as fuel for diesle engines, e.g. cars and large vehicles such as buses, trains, trucks can be cracked to produce kerosene and gasoline.
Naphtha (composition, boiling range, carbon length and use(s))
Composition: 15-30% of crude oil, together with gasoline. The boiling range is 20-180⁰C Carbon length: C₅-C₉ carbon chain. Uses: raw material for making high octane gasoline, used for dilute bitumen which aids in pipeline transportation, used in the petrochemical industry for producing alkenes, used as a solvent in the manufacture of chemicals.
Gasoline (Petrol) (composition, boiling range, carbon length and use(s))
Composition: 15-30% of crude oil, together with naphtha The boiling range is 40-200⁰C Carbon length: C₅-C₁₀ carbon chain. Use: used as fuel for motor vehicles, e.g. cars, boats and light aircraft.
Lubricating oil (composition, boiling range, carbon length and use(s))
Composition: 45-50% of crude oil, together with paraffin wax and bitumen. Boiling range is >370⁰C. Carbon length: C₂₀-C₅₀ Uses: used as lubricating oils, wax, polished, waxed paper, candels, as solvent for ointments and rubs e.g.petroleum jelly, as fuel for large ships, factory boilers, large furnaces such as those in power stations.
Paraffin wax (composition, carbon length and use(s))
Composition: Residue afrer fractionation of cude oil Carbon length is >C₄₀ carbon chain. Use: used as wax and serves as an insulator and also stores heat.
Bitumen (tar) (composition, carbon length and use(s))
Composition: reidue after fractionation of crude oil. Carbon length is >C₇₀ carbon chain. Use: used for road surfacing, roofing, waterproofing, sealing.
What is the importance of toluene and xylenes ?
- Benzene, toluene and the xylenes are some of the main aromatic products of reforming the Cfi - C8 hydrocarbons from the naphtha fraction. All of these are used as starting materials in the petrochemical industry. - Toluene and xylenes are also used to increase the octane number in gasoline. It is also important to note that hydrogen gas is a valuable by-product which can be used in the Haber process.
What is Catalytic Cracking?
- Catalytic cracking (cat-cracking) involves the use of a catalyst at low temperatures to break the bonds of the hydrocarbon molecules. - The reaction is useually catalyzed by a powdered micture of aluminal or silica (Al₂O₂/SiO₂) at about 500⁰C. - The C-C bond undergoes heterolytic fission which results in a mechanism involving carbocations. This tend to produce a larger amount of branched chain alkanes whicha re useful in gasoline. Branched chain alkanes give gasoline a higher octane number.
Impact of the Crude Oil Industry on the Environment (Event in 1979 with the Atlantic Express)
- In 1979 the Atlantic Empress spilled 42.7 million gallons of oil as the result of a collision with the Aegean Captain in the Caribbean Sea near Trinidad and Tobago. Oil spills are detrimental as organisms are at risk of inhaling or ingestion the oil which can poison them. - When sea birds are covered with oil, their feathers stick together and they lose their ability to fly. - The oil also sticks down the fur of animals (e.g. polar bears) which causes them to lose insulation and freeze to death. - Oil spills also ruin coral reefs and beaches thereby affecting the tourism industry.
Impact of the Crude Oil Industry on the Environment (BTEX compounds)
- In the refining process, hazardous and toxic air pollutants such as carbon monoxide, hydrogen sulphide, nitrogen oxides, sulphur dioxide and BTEX compounds (benzene, toluene, ethylbenzene, and xylene) are emitted into the atmosphere. There are concerns about the effects of exposure to these chemicals. - BTEX compounds are possible carcinogens and may cause reproductive and developmental problems. They may also aggravate respiratory conditions such as asthma.
Why is catalytic cracking more frequently used between the two types of cracking?
- It produces a greater amount of branched-chain alkanes, which is desirable; - Ir requires less energy; - It is more efficient.
Kerosene (paraffin oil) (composition, boiling range, carbon length and use(s))
Compostion: 10-15% of crude oil. Boiling ranges is 150-260⁰C Carbon length: C₁₀-C₁₆ carbon chain Uses: used as fuel for jet engines and some rockets, fuel for domestic heating, e.g. kerosene lamps (for lighting), paraffine stoves (for heating), can be cracked to produce gasoline.
What is Cracking?
Cracking is a process in which large hydrocarbon molecules are broken down into smaller molecules. The cracked products may be smaller alkanes, alkenes and hydrogen molecules. The large hydrocarbon molecule can break anywhere along the carbon chain to form a variety of smaller molecules. For example, dodecane can break into decane and ethene. C₁₂H₂₆ → C₁₀H₂₂ + CH₂=CH₂ or nonane and propene C₁₂H₂₆ → C₉H₂₀ + CH₃CH=CH₂ Cracking is carried ot either using heat (thermal cracking) or a catalyst (catalytic cracking)
What does crude oil consists of?
Crude oil consists mainly of a variety of alkanes, cycloalkanes and aromatic hydrocarbons. There are also small amounts of other substances such as compounds of nitrogen, oxygen and sulphur. Crude oil from different areas of the world or even different depths in the same oilfield varies slightly. Thus the composition and appearance of crude oil depend on its source.
How is crude oil formed?
Crude oil was formed from the remains of microscopic plants and animals that were buried and preserved in rocks millions of years ago. These remains slowly decayed as they were buried deeper within layers of rocks and with time and temperature, they were converted to crude oil. Similar conditions have also led to the formation of natural gas which is frequently found associated with crude oil.
What was the first way used to reduce knocking and the reason it needed to be replaced?
In the past, knocking was reduced by adding tetraethyllead (IV) to fuel.However, leaded fuel contributes large amounts of lead pollution to the environment.
What is alkylation?
In this process tertiary alkanes combine with alkenes to make longer branched chain alkanes. The product is a blend of alkanes with high octane numbers. The reaction occurs at room temperature and is catalyzed by concentrated sulphuric acid. FOr example, 20methylpropane is. added to 2-methylpropane to form 2,2,4-trimethylpentane which ahs exceptional anti-knock propeties.
What was the replacement of the chemical containing lead that was added to fuel to reduce knocking?
Now leaded fuel is now being phased out and is largely replaced by unleaded fuel, which containes more branched chain alkanes. - branched-chain alkanes are compact and tend to be more resistant to knwokcing - Straight-chain alkanes are long and prone to cause knocking.
Give an example of octane ratings being used for fuels
On this 'octane rating scale' the straight-chain alkane heptane is assigned an oxtane rating of 0. Heptane is highly prone to detonation as it comprises seven carbon atoms in a long, straight chain and therefore knocks readily with little compression. The highly branched-chain alkane 2,2,4-trimethylpentane (also knwon as iso-octane) is assigned an octane rating of 100. It burns smoothly with little knock.
Fuel consumption and fuel efficiency
Several of the fraction obtained from fractional distillation are used as either motor or aviation fuels. Fuel consumption is substantial and the study of a fuel's efficiency is extremely important in an attempt to maximize the power of an engine without damaging the engine.
Crude Oil
is a complex mixture of naturally occurring hydrocarbons found within the Earth.
How does lead enter the atmosphere?
lead can enter the environment through lead/acid car batteries, car exhaust gases which come from petrol use, waster from smelting, plumbing industries, brass plumbing materials, underground lead pipes and lead solder used in copper pipes.
How does lead perform as a pollutant?
- Lead is a metallic element which can cause serious health problems since it is a cummulative poison and is not excreted from the body. It damages the nervous system, inhibits the action of bodily enzymes and can cause brain damage which reduces a human's intelligence. - There are environmental concerns since lead is a non-biodegradable substance and is hard to clean up once the environment is contaminated. When water from the land containing lead is washed into rivers and seas, this lead enters the food chain and therefore fishes become contaminated with lead. - Fishermen and their families that ingest fish have sometimes been found to have high levels of lead in their bodies.
What is reforming ?
- Reforming is a process which converts straight chain hydrocarbons into aromatic and more highly branched hydrocarbons. This process converts low value naphtha fractions into high grade gasoline components. Higher grade gasoline contains a higher proportion of branched a;lanmes and aromatic hydrocarbons. - Products of reforming are also used as starting materials in the petrochemical industry. Reformoing is the effect of numberous reactions such as isomerization, alkylation and catalytic reforming.
Fractional distillation of crude oil (How does it work?)
- The crude oil is heated to about 400⁰C and passed into a fractionating column which may be as high as 60 metres. The column consists of a number of horizontal trays at intervals along with its height. - It is heated at the base but the temperature gradually decreases towards the top of the column thus each tray is slightly cooler than the one below it. - The vapour rises up the column and condenses on a tray where the temperature is lower than its boiling point. The trays have holes in them which are covered by bubble caps. As more rising vapour passes through the holes in the tray, the bubble caps directly the vapour through the liquid already on the tray. This caused the lighter components condensed in the tray to vaporize again and continue to move up the column. - There are also overflow tubes at the side of trays which allow liquid to flow back down the column. When this liquid reaches a lower tray, the higher temperature there brings about vaporization of the more volatile component which then rises up the column. - As the vapour condenses and vaporizes many times on the trays along the column, the composition of the vapour becomes richer in the more volatile component (i.e. the one with the lower boiling point). The more volatile ones tend to condense on the trays at various levels along the column, Thus the crude oil is separated into different fractions, each boiling within a particular temperature range.
Impact of the Crude Oil Industry on the Environment (crude oil entering the)
- The oil industry is considered a major source of pollution to the environment. Pollution may occur during extraction, transportation and refining of the crude oil. Also the use of its refined products has an impact on the environment. - Extraction of crude oil involves emissions of pollutants from the first seismic survey until the field is shut down. Well drilling discharges oil into surrounding soil and water. This can damage fragile ecosystems by destroying habitats and killing organisms.Oil is usually transported through pipelines and in large ocean tankers. This presents the possibility of accidental leaks and spills.
What is thermal cracking?
- Thermal cracking involves rapidly heating the hydrocarbon to tempertures of about 800⁰C and then cooling it. This process occurs within a second. The high temperatures can cause the C-C bond to undergo homolytic fission. This results in the fomation of free radicals. For example, dodecane can form a decyl radical and an ethyl radical. C₁₂H₂₆ → *C₁₀H₂₁ + *C₂H₅ (* represents the radical) - These three free radicals can undergo further reactions. The ethyl radical can lose a hydrogen atom to form ethene. *C₂H₅ → C₂H₄ + *H The hydrogen atom, which is a free radical, can combine with the decyl radical to form decane. *H + *C₁₀H₂₁ → C₁₀H₂₂ or two hydrogen atoms can combine to form hydroen gas. *H +*H → H₂ - Since the carbon chain can split in a number of ways, a wide variety of smaller molecules are produced which can be separated by fractional distillation. Thermal cracking is generally used for crackibg the residue fraction of crude oil.
What is catalytic reforming?
- This process converts straight chain alkane molecules of the naphtha fraction into cycloalkanes and aromatic hydrocarbons. - The naphtha vapour is heated to about 500°C at a pressure of 20 atm and then passed over a catalyst made of platinum and aluminium oxide. The equations for the conversion of hexane to cyclohexane and hexane to benzene are given below. -
Explain the concept of "Knocking" in fuel
- When the air/fuel mixture is compressed in an internal combustion engine, ideal conditions will result in the mixture burning smoothly in response to ignition by the spark plug at a precise time. - However, some fuel mixtures ignite spontaneously and explode prematurely, thereby creating engine knock which gives a characteristic of rattling or pinging sound. - Knocking not only reduces the efficiency of the fuel, but also causes overheating, loss of power and engine damage. This tendency for fuel to auto-ignite in an engine's combustion chamber is termed detonation.
Cracking of hydrocarbons and why do we do it?
- fractional distillation of crude oil produces a high percentage of large hydrocarbon molecules. Although there are uses for these various heavy fractions of crude oil, the demand for lighter fractions such as gasoline surpasses the amount supplied by fractional distillation. - Therefore, in order to satisfy this demand, oil refineries convert the lower value, heavy fractions into more rmmarketable, higher value products using either process of cracking or reforming.
Alkanes with: - Straight chains have a ______ octane rating; - Branched chains have ______ octane ratings.
1. low 2. high
What can the by-product ethene by used for?
Ethene is the most versatile organic compound in use today, being used primarily in the polymer industry. THe petroleum industry uses considerable quantities of ethene and propene as building blocks for larger organic molecules.
What are the major fractions of crude oil?
From lowest boiling point to highest is: 1. Refinery gas 2. Naphtha 3. Gasoline (petrol) 4. Kerosene (paraffin oil) 5. Diesel (gas oil) 6. Lubricating oil
Is it possible to have a research octane number that is either less than zero or greater than 100? Give an example with your answer.
It is possible for fuels to have a research octane number that is either less than zero or greater than 100. For example, the octane rating for octane (the straight-chain isomer) is -10 whilst that for methanol is 110.
What mixtures are used as standards for octane ratings between 0 and 100?
Mixtures of 2,2,4-trimethylpentane and heptane are used as standards for octane ratings between 0 and 100. For example, a fuel that has the same anti-knocking characteristics in an engine as a mixture of 87% iso-octane and 13% heptane would have an octane rating of 87 and will be rated as 87-octane.
How does crude oil look?
Most crude oil looks like thin, brown treacle, while sokme are most colourless volatile liquids and others are thick black oils.
Impact of the Crude Oil Industry on the Environment (fuel for transportation and electric power)
Most of the petroleum in the world is used as fuel for transportation and electric power generation. This releases large amounts of carbon dioxide, a greenhouse gas, which contributes to global warming. The use of hydrocarbon fuels in vehicle engines also release other gases such as nitrogen oxides which contribute to acid rain and toxic carbon monoxide.
Impact of the Crude Oil Industry on the Environment (Sulphur dioxide)
Sulphur dioxide and nitrogen oxides contribute to the formation of acid rain. The effects of acid rain include erosion of stonework on buildings, destruction of trees and acidifying lakes which results in the death of fish.
Fractional distillation of crude oil (Why use fractional distillation?)
The components of crude oil have different boiling points due to the arrangement and variation in the number of carbon atoms in the hydrocarbon molecules. Fractional distillation uses this difference in boiling point to separate these components.
Fractional distillation (How are the products collected?)
The different fractions are drawn off various levels along the column. The lightest fraction comes off at the top of the column as a gas. It contains fewer carbon atoms and has the lowest boiling point range. As you go down the column, the fractions become heavier and have a higher boiling point range. The typical fractions of crude oil are shown in the image.
Impact of the Crude Oil Industry on the Environment (in the petrochemical industry)
The part of petroleum that is used as feedstock for the petrochemical industry is utilized in making thousands of products. These include plastics, fertilizers, detergents and cosmetics, all of which eventually end up in the environment. Products like plastics are difficult to dispose of as they are not readily degradable and they release toxic fumes when burnt.
How is the performance of fuel measured?
The performance of a fuel is marked by the anti-knock properties, which are measured as an octane rating (number).
Impact of the Crude Oil Industry on the Environment (methods for dealing with oil spills)
There are several different methods for dealing with oil spills on the surface of the water. Some of these are given below. 1. A floating barrier called a boom is placed around the oil to keep it from spreading. 2. The oil can be ignited within the boom. 3. A giant vacuum can be used to suck up the surface oil. 4. Absorbents are used to collect the oil left behind from suctioning. Natural absorbents like clay and sand can hold up to 20 times their weight in oil while synthetic absorbents like polyethene can hold up to 70 times its weight in oil. 5. Solvent compounds are used to break down light oil spills and disperse it. 6. Natural bacteria that use the petroleum products as food are often effective at cleaning up oil spills although they may take years to work.
What is isomerization in the crude oil industry?
This involves breaking up straight chain hydrocarbons and reassembling them as chain isomers. The reaction takes place at about 500°C in the presence of an alumninium chloride catalyst. Isomerization is important for the conversion of normal pentanes and hexanes into higher branched isomers for gasoline blending. It is also used to covert butane into 2-methylpropane to provide additional feedstock for alkylation units.
What is Petroleum?
Together crude oil and natural gas are referred to as petroleum.
Impact of the Crude Oil Industry on the Environment (Wastewater)
Wastewater in refineries may be contaminated with oil residues and other hazardous wastes from equipment leaks and spills. Although this water is treated before being released into the environment, some of these wastes may end up in aquifers and groundwater.
Uses of crude oil
as it comes from the ground are limited. However, maximum value can be obtained from this natural resource when it is used as a raw material. Crude oil must be separated into its various components and selectively modified before it can be useful. This process is called refining and occurs in an oil refinery. Once the crude oil is extracted and transported to the oil refinery, it is transformed into fuel for transportation and electric power generation as well as feedstock for the petrochemical industry. The primary process for separating the components of crude oil is fractional distillation.
