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1800-102-2727Fuel is such an integral part of human civilization. Crude oil extracted from the earth is processed to obtain a multitude of beneficial petrochemical products. A combination of hydrocarbon molecules makes up crude oil.
Oil refineries produce the high-in-demand petrochemical products from the crude oil that makes the Earth run!
You name it— From aeroplanes to school buses, heating your cosy homes to running a large-scale industrial plant, fuel is the ultimate driver of all advancements that are happening across the globe.
Refineries are built to create the fuel and other related resources that the market demands. Fuel for motor vehicles is currently in the highest demand on global markets. However, the amount of petrol (gasoline) and petroleum products produced by standard fractional distillation of crude oil is insufficient to satisfy the increasing customer demands. The fractionation process recovers majorly longer hydrocarbons. Whereas Petroleum hydrocarbons (PHs) are made up of short-chain hydrocarbon substances such as smaller alkanes, paraffin, alicyclic, and aromatic chemicals.
Hence, longer hydrocarbons are subjected to a process called cracking that breaks them down to smaller and economically more beneficial small-chain hydrocarbons to meet the demands of the global sectors.
TABLE OF CONTENTS
Cracking is an integral part of oil refineries. Crude oil is refined using a method called fractional distillation. With this method, crude oil is divided into several fractions based on the boiling points of its constituent molecules. The fractions are heavy gas oil, lubricating oil, gas oil and diesel, kerosene, gasoline, naphtha, and gas, in that order. The length and arrangement of the molecules vary, and as a result, they display various characteristics, including boiling point.
Following separation, fractions can undergo additional processing to yield a variety of products needed every day, such as fuels, polymers, and medications.
This method incorporates a variety of free radical-based chemical processes. Here are several crucial reactions that happen.
Initiation: Here, a single molecule disintegrates into two free radicals as the initial step. Only a small portion of the liberated radicals go through initiation, but it is essential to generate enough free radicals to continue the complete reaction.
CH3CH3 → 2CH3
Abstraction of Hydrogen: In this case, the free radical generated removes an atom of hydrogen from a third molecule, resulting in the formation of a free radical and a lower alkane.
CH3• + CH3CH3 → CH4 + CH3CH2•
Radical Decomposition: In this step, the free radicals split into an alkene and another free radical. The byproducts of this reaction are alkenes.
CH3CH2• → CH2=CH2 + H•
Radical Addition: Here, a radical and an alkene interact to form a free radical.
CH3CH2• + CH2=CH2 → CH3CH2CH2CH2•
Termination: Two free radicals join in this reaction to create products that are not free radicals. One is a lower alkane and the other is an alkene.
CH3• + CH3CH2• → CH3CH2CH3
CH3CH2• + CH3CH2• → CH2=CH2 + CH3CH3
There are three major types of cracking.
Conversion: Residual oil to diesel, fuel oil, petrol, and naphtha.
Conversion: Gas oil or residual oil to diesel and petrol. Extremely cost-effective and energy efficient.
Conversion: Gas oil into petrol.
Answer: A
Solution: Long chain hydrocarbons have high molar mass and hence there is stronger van der Waals force of attraction between them, unlike small chain hydrocarbons which have less intermolecular forces. Hence, the boiling point of small chain hydrocarbons obtained after cracking is expected to be lower than the long-chain hydrocarbons.
So, option A is the correct answer.
Solution: The intermolecular force between longer hydrocarbon molecules is stronger. They have greater boiling points, and so to separate them, more energy is required. So, being less volatile, they become less flammable and as a result, are less efficient as fuels.
Answer: A
Solution: Among the catalysts employed in fluid catalytic cracking procedure, the main ones are (FCC), aluminosilicate zeolite (ZSM-5), and silica-alumina (Al2O3/SiO2).
So, option A is the correct answer.
Answer: Hydrocarbons that are insoluble in typical solvents like carbon tetrachloride but produce liquid or gaseous petroleum when heated are referred to as kerogen.
1. What is petrol’s composition?
Answer: A combination of hydrocarbons with 5 to 10 carbon atoms can be found in petrol (gasoline). Straight-chain alkane content is high in the combination of C5-C10 hydrocarbons derived directly from from the distillation of crude oil. The engine of a car suffers severe harm if this mixture is utilised as gasoline. Hence straight-chain alkanes are transformed into branched-chain alkanes, cycloalkanes, and aromatic hydrocarbons in a number of processes in the refinery to finally obtain the commercially sourced petrol because they are much more knock-resistant.
2. What is Knocking?
Answer: In the cylinder of an automobile engine, gasoline with a high concentration of straight chain alkanes has a tendency to ignite as the piston builds pressure and before the cylinder reaches the ideal position. A spark is generated and this ignites the mixture of air and gasoline at a specific location on the piston in the cylinder causing a knocking sound. This is called as knocking
Engine knock and pre-ignition are two terms used to describe this issue with early ignition. When pre-ignition is audible, the phrase knock is employed. Serious engine damage might result from a severe knocking.
3. What is octane number/octane rating?
Answer: An octane rating is a measurement of how heat resistant a fuel is to avoid knocking. Octane does not improve combustion; rather, it stops the air-fuel mixture inside an engine from igniting earlier than it should. The resistance of a fuel to knocking increases with increasing octane.
The resistance of the gasoline mixture to knocking increases with increasing octane number. Higher compression ratios, turbocharging, and downsizing/downspeeding are also made possible by the use of higher octane fuels, all of which increase engine performance and efficiency.
4. Why is catalytic cracking beneficial as compared to thermal cracking?
Answer: The industry of refining crude oil makes extensive use of catalytic cracking to transform viscous feedstocks into lighter and more valuable gasoline and petrol-based fractions. Catalytic cracking has replaced thermal cracking as a result of the rise in demand for gasoline with a higher octane rating, which is highly efficient for the automobile industry. Also, catalytic cracking requires less temperature and pressure and is hence energy efficient.
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Thin Layer Chromatography |
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