Cracking Process: Liquid vs Vapor Phase

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Questions and Answers

At what temperature is heavy oil cracked in the liquid phase?

300°C

4755°C (correct)

5300°C

475°C

What is the approximate yield of gasoline in the vapor phase cracking process?

70% (correct)

90%

10%

40%

Which type of cracking is carried out at lower temperature and pressure with the aid of a catalyst?

Vapor Phase Cracking

Liquid Phase Cracking

Catalytic Cracking (correct)

Polymerization Cracking

What is the purpose of alkylation in the synthesis of petrol?

To enhance octane number Signup and view all the answers

What term is used to describe the characteristic metallic or rattling sound from an engine due to badly controlled burning and explosion?

Detonation Signup and view all the answers

In which cracking process is heavy oil first vaporized before being cracked at a lower pressure?

Vapor Phase Cracking Signup and view all the answers

What are the common examples of combustible substances according to the text?

Wood, charcoal, coal Signup and view all the answers

What is the final product of complete combustion of hydrocarbons?

Carbon Dioxide and Water Signup and view all the answers

Which instrument is used to measure the density of fuel?

Hydrometer Signup and view all the answers

What does specific gravity measure?

Density of fuel relative to water Signup and view all the answers

What is the unit for density as mentioned in the text?

kg/m^3 Signup and view all the answers

What always accompanies the vigorous reaction with oxygen according to the text?

Heat and light Signup and view all the answers

What is the harmful air pollutant created during the burning of lead bromide?

Lead bromide gas Signup and view all the answers

Which gas is found above the oil in oil wells and is also known as Marsh gas?

Methane Signup and view all the answers

What is the calorific value range of Natural Gas, consisting mainly of methane and other saturated hydrocarbons?

12,000 - 14,000 kcal/m3 Signup and view all the answers

Which gas is a major constituent of Water or Blue Gas?

Hydrogen (H2) Signup and view all the answers

What is one of the uses of Natural Gas mentioned in the text?

Generation of electricity using fuel cells Signup and view all the answers

Which gas mixture is used in the manufacture of ammonia by Haber's process?

Blue Gas Signup and view all the answers

What is the calorific value of the fuel mentioned in the text?

5400 kcals/m3 Signup and view all the answers

What must be present for complete combustion of a fuel to occur?

Adequate supply of oxygen gas (O2) Signup and view all the answers

Why do solid or liquid fuels need to be changed to a gas before burning?

To allow them to burn efficiently in their normal state Signup and view all the answers

What role does N2 play in the combustion process?

Dilutes flue gases Signup and view all the answers

What percentage of dry air is composed of oxygen gas (O2)?

21% Signup and view all the answers

Why is complete combustion of a fuel only possible with an adequate supply of oxygen?

To avoid incomplete combustion and produce heat effectively Signup and view all the answers

What is the main way asphalt is obtained?

Deep vacuum distillation of residual heavy oil Signup and view all the answers

What type of gasoline is obtained from the fractional distillation of crude oil?

Straight Run Gasoline Signup and view all the answers

What happens to straight chain alkanes during cracking?

They are converted into branched chain hydrocarbons Signup and view all the answers

Why does straight run gasoline produce knocking in internal combustion engines?

Because it contains mainly straight chain paraffin hydrocarbons Signup and view all the answers

Which statement about cracking is false?

Thermal cracking is carried out at lower temperatures and pressures with a catalyst Signup and view all the answers

What is the main use of asphalt as mentioned in the text?

Road making and water-proofing roofs Signup and view all the answers

Study Notes

Combustible Substances

Combustible substances contain carbon as a main constituent and produce a large amount of heat when burned properly.
They can be solid, liquid, or gas and are used economically for domestic and industrial purposes.
Examples include wood, charcoal, coal, kerosene, petrol, diesel, producer gas, and oil gas.

Combustion

Combustion is a vigorous reaction with oxygen, accompanied by the evolution of heat and light.
It is an exothermic process, releasing heat energy.
The final products of complete combustion of hydrocarbons are carbon dioxide and water vapor.

Incomplete Combustion

Incomplete combustion results in a mixture of carbon dioxide and carbon monoxide with water.
This occurs when there is not enough oxygen available for complete combustion.

Properties of Fuels

Density

Density is the ratio of the mass of a fuel to its volume at a reference temperature of 15°C.
It is measured by a hydrometer.
Density is useful for quantity calculations and assessing ignition quality.
It is measured in kg/m3.

Specific Gravity

Specific gravity is the ratio of the weight of a given volume of oil to the weight of the same volume of water at a given temperature.
It is measured by a hydrometer.
Specific gravity is used in calculations involving weights and volumes.
It has no units, as it is a ratio.

Asphalt

Asphalt is obtained by the oxidation of residual heavy oil in the presence of air at higher temperatures.
It can also be obtained through the deep vacuum distillation of residual heavy oil.
Asphalt is available in liquid, semi-solid, and solid forms.
It is used for road making, waterproofing roofs, and manufacturing waterproofing concrete and paints.

Cracking

Cracking is the decomposition of high boiling hydrocarbons of high molecular weight into smaller, low boiling hydrocarbons of low molecular weight.
Straight chain alkanes are converted into branched chain hydrocarbons during cracking.
Saturated hydrocarbons are converted into a mixture of saturated and unsaturated hydrocarbons.
Aliphatic alkanes are converted into cyclic alkanes.
All hydrocarbons obtained by cracking have a lower boiling point than the parent hydrocarbons.

Types of Cracking

Thermal Cracking: carried out at higher temperature and pressure without a catalyst.
Catalytic Cracking: carried out at lower temperature and pressure in the presence of a suitable catalyst.

Synthesis of Petrol

Polymerization: thermal and catalytic polymerization.
Hydrogenation of Coal: Bergius Process or Direct Process, and Fisher Tropsch Process or Indirect Process.
Alkylation.

Knocking and Octane Number

Knocking occurs when the fuel-air mixture is heated to a temperature greater than its ignition temperature, resulting in spontaneous combustion.
This leads to a sudden, badly controlled burning and explosion, producing a characteristic metallic or rattling sound from the engine.

Natural Gas

Natural Gas is always found above the oil in oil wells and is also called Marsh gas.
It consists of methane and other saturated hydrocarbons.
Calorific value varies from 12,000 to 14,000 kcal/m3.
Constituents: methane, ethane, propane, butane, and pentane.
Uses: domestic and industrial fuel, raw material for the manufacture of carbon black and hydrogen, and generation of electricity by using it in fuel cells.

Water or Blue Gas

Water or Blue Gas is a mixture of combustible gases like CO, H2, with a little non-combustible gases like CO2 and N2.
Calorific value is 2800 kcal/m3.
Composition: H2 = 48%, CO = 44%, and CO2, N2, and CH4 = rest.
Uses: manufacture of ammonia by Haber's process, and generation of electricity by burning it to raise steam.

Combustion Efficiency

N2 is a temperature-reducing diluent that must be present to obtain the O2 required for combustion.
N2 reduces combustion efficiency by absorbing heat from the combustion of fuels and diluting the flue gases.
This reduces the heat available for transfer and increases the volume of combustion by-products.

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Description

Learn about the differences between liquid phase and vapor phase cracking processes for heavy oil, including temperature, pressure, and gasoline yield. Explore the concept of catalytic cracking carried out under lower temperature and pressure with a suitable catalyst.