Introduction
The fractional distillation of petroleum gives only around 20% fuel. As a result of its high demand, this supply is augmented by transforming excess supplies of less desirable oil fractions such as kerosene oil and gasoline oil into fuel by a process called cracking.
Definition
It is defined as cracking of higher hydrocarbons having high boiling points into a selection of lower hydrocarbons, which are much more volatile (reduced boiling).
This is the process in which C-C bonds in long-chain alkane molecules are broken, generating smaller molecules of both alkanes and also alkenes. The make-up of the products depends upon the condition under which the cracking takes place.
Methods of Cracking
Cracking is generally performed in the following ways.
(1) Thermal Cracking
Breaking down large molecules by heating at high temperature and pressure is called Thermal Cracking. It is especially useful in the production of unsaturated hydrocarbons such as ethene and also propene.
(2) Catalytic Cracking
Higher hydrocarbons can be broken at a lower temperature (500 ° C) and lower pressure (2 atm), in the presence of an appropriate catalyst. A typical catalyst used for this function is a mix of silica (SiO2) and also alumina (AI2O3).
Catalytic cracking produces fuel of higher-octane number as well as, consequently, this approach is made use of for acquiring far better high-quality fuel.
The zeolites are used in catalytic cracking are picked to give a high percentage of hydrocarbons with between 5 and 10 carbon atoms – specifically useful for fuel (gasoline). It additionally produces high proportions of branched alkanes as well as aromatic hydrocarbons like benzene.
The zeolite catalyst has sites that can eliminate hydrogen from an alkane along with the two electrons which bound it to the carbon.
(3) Steam Cracking
In this process, higher hydrocarbons in the vapor stage are blended with steam, heated up for a short period at about 900 ° C as well as cooled rapidly. The process is appropriate for obtaining lower unsaturated hydrocarbons.
Advantages of Cracking
- Besides increasing the yield of fuel, cracking has actually additionally created huge quantities of useful by-products, such as ethene, propene, butene, and also benzene.
- These are utilized for manufacturing medicines, plastics, detergents, synthetic fibers, plant foods, weed killers, and essential chemicals like ethanol, phenol, and acetone.
FAQs – Cracking of Petroleum
- What is cracking in the context of petroleum refining?
- Cracking refers to the process of breaking down higher hydrocarbons with high boiling points into smaller, more volatile hydrocarbons to increase the yield of valuable fuels.
- Why is cracking necessary in the petroleum industry?
- The fractional distillation of petroleum provides only around 20% fuel. Cracking allows the transformation of less desirable oil fractions into valuable fuels, meeting the high demand for energy resources.
- How is cracking defined in the context of hydrocarbon molecules?
- Cracking involves breaking C-C bonds in long-chain alkane molecules, producing smaller molecules of both alkanes and alkenes. The composition of the products depends on the specific conditions of the cracking process.
- What are the main methods of cracking?
- Cracking is performed through three main methods: Thermal Cracking, Catalytic Cracking, and Steam Cracking.
- Explain Thermal Cracking and its significance.
- Thermal Cracking involves breaking down large molecules by heating at high temperature and pressure. It is especially useful in the production of unsaturated hydrocarbons like ethene and propene.
- What is Catalytic Cracking, and how does it differ from Thermal Cracking?
- Catalytic Cracking occurs at lower temperature and pressure in the presence of a catalyst, typically a mix of silica and alumina. It produces higher-octane fuel and is known for generating valuable by-products.
- How does Steam Cracking contribute to the cracking process?
- In Steam Cracking, higher hydrocarbons in the vapor stage are mixed with steam, heated, and rapidly cooled. This process is suitable for obtaining lower unsaturated hydrocarbons.
- What are the advantages of cracking besides increasing fuel yield?
- Cracking results in significant by-products such as ethene, propene, butene, and benzene. These by-products are utilized in various industries for manufacturing medicines, plastics, detergents, synthetic fibers, and essential chemicals.
- What catalyst is commonly used in Catalytic Cracking, and why?
- A common catalyst used in Catalytic Cracking is a mixture of silica and alumina. Zeolites within the catalyst provide sites for removing hydrogen from an alkane, producing high-quality fuel.
- How has cracking contributed to the production of valuable chemicals beyond fuels?
- Cracking has led to the production of valuable by-products like ethene, propene, butene, and benzene, which are used in the manufacturing of medicines, plastics, detergents, synthetic fibers, fertilizers, herbicides, and essential chemicals like ethanol, phenol, and acetone.