Answer to Question #299601 in Organic Chemistry for claire yeboah

Question

Describe the process of catalytic cracking used in the petroleum refining industry

Your answer must also include:

·     A balanced chemical equation, physical states included and reaction conditions stated

·     Examples of a product formed from catalytic cracking (in petroleum refining) and its use

Answer 1

In petroleum refining, this process is used in the production of petrol, diesel, and gasoline. In chemistry, it is a process of breaking down large alkane into simpler alkenes and alkanes. Similarly, cracking of hydrocarbons includes breaking down of a complex long chain of hydrocarbons into smaller ones.

Cracking in Organic Chemistry

During this process, it involves numerous chemical reactions based on free radicals. Some vital reactions that take place are stated below.

Initiation: Here a single molecule breaks down into 2 free radicals. Only a smaller portion of freed radicals undergoes initiation, but it is sufficient to produce free radicals that are necessary to carry forward the entire reaction.

CH₃CH₃ → 2 CH₃

Abstraction of Hydrogen: Here the second molecule becomes a free radical as it removes a hydrogen atom from another molecule.

CH₃• + CH₃CH₃ → CH₄ + CH₃CH₂•

Radical Decomposition: Here free radicals break into other free radical and an alkane. This reaction gives rise to alkene products.

CH₃CH₂• → CH₂=CH₂ + H

Radical Addition: This reaction results in the formation of aromatic products. Here radical reacts with an alkene to produce a free radical.

CH₃CH₂• + CH₂=CH₂ → CH₃CH₂CH₂CH₂•

Termination: Here 2 radicals react with each other to form products that are not free radicals. This reaction results in two forms namely recombination and disproportionation.

CH₃• + CH₃CH₂• → CH₃CH₂CH₃

CH₃CH₂• + CH₃CH₂• → CH₂=CH₂ + CH₃CH₃

Types of Cracking

1. FCC: Fluid Catalytic Cracking: It is mainly used in petroleum refiners. This process involves the conversion of high molecular weight, high boiling hydrocarbons into olefinic, gases, gasoline and other products.
2. Hydro cracking: It is a catalytic cracking process, where it uses hydro cracking to break C – C bonds. Products produced by this process include diesel, jet fuel, and LPG.
3. Steam Cracking: It is a petrochemical process that involves the breakdown of saturated hydrocarbons into smaller unsaturated hydrocarbons.
4. Thermal Cracking: It is a process that involves breaking of large non-volatile hydrocarbons into gasoline

The first thermal cracking process for breaking up large nonvolatile hydrocarbons into gasoline came into use in 1913; it was invented by William Merriam Burton, a chemist who worked for the Standard Oil Company (Indiana), which later became the Amoco Corporation. Various improvements to thermal cracking were introduced into the 1920s. Also in the 1920s, French chemist Eugène Houdry improved the cracking process with catalysts to obtain a higher-octane product. His process was introduced in 1936 by the Socony-Vacuum Oil Company (later Mobil Oil Corporation) and in 1937 by the Sun Oil Company (later Sunoco, Inc.). Catalytic cracking was itself improved in the 1940s with the use of fluidized or moving beds of powdered catalyst. During the 1950s, as demand for automobile and jet fuel increased, hydrocracking was applied to petroleum refining. This process employs hydrogen gas to improve the hydrogen-carbon ratio in the cracked molecules and to arrive at a broader range of end products, such as gasoline, kerosene (used in jet fuel), and diesel fuel. Modern low-temperature hydrocracking was put into commercial production in 1963 by the Standard Oil Company of California (later the Chevron Corporation).