Full Answer
What is cracking in chemistry?
What is Cracking? Cracking is defined as a process, wherein complex organic molecules namely long chain hydrocarbons or kerogens are broken down into smaller molecules namely light hydrocarbons. It is caused by the breaking of carbon-carbon bonds.
What is cracking of hydrocarbon?
Cracking is defined as a process, wherein complex organic molecules namely long chain hydrocarbons or kerogens are broken down into smaller molecules namely light hydrocarbons. It is caused by the breaking of carbon-carbon bonds.
What are the by-products of cracking?
To produce by-products such as cooking oil, ethanol, liquefied petroleum gas, diesel fuel, jet fuel and other petroleum distillates, cracking removes large hydrocarbon molecules in raw crude oil. What happens during cracking?
What are the products produced by the steam cracking process?
Products produced by this process include diesel, jet fuel, and LPG. Steam Cracking: It is a petrochemical process that involves the breakdown of saturated hydrocarbons into smaller unsaturated hydrocarbons.
What can cause cracking?
Cracking is a common damage caused by stress in a material that can easily be exaggerated by other factors, including corrosion, fatigue, high pressure, and material of construction.
What products does cracking produce?
Cracking of petroleum yields light oils (corresponding to gasoline), middle-range oils used in diesel fuel, residual heavy oils, a solid carbonaceous product known as coke, and such gases as methane, ethane, ethylene, propane, propylene, and butylene.
What chemicals are used in cracking?
The catalytic cracking process involves the presence of solid acid catalysts, usually silica-alumina and zeolites.
What are the 3 types of cracking?
Process of Cracking Hydrogen Abstraction- Hydrogen is removed from the second molecule thereby making it a free radical. Radical Decomposition- Free radicals break into other free radicals to form alkene products. Radical Addition- Then the free radicals react with the alkenes.
What is made in the process of cracking?
Cracking is a chemical process which is used in oil refining. To produce by-products such as cooking oil, ethanol, liquefied petroleum gas, diesel fuel, jet fuel and other petroleum distillates, cracking removes large hydrocarbon molecules in raw crude oil.
What are the 2 types of cracking?
Cracking in chemistry is of two types: Thermal cracking and Catalytic Cracking. The chemical process of cracking involves various free radical reactions. These cracking reactions are Initiation, Hydrogen Abstraction, Radical Decomposition, Radical Addition and Termination.
What type of reaction is cracking?
Cracking is an example of a thermal decomposition chemical reaction.
Which gas is known as cracking gas?
(a) The composition of the feedstockProductFeedstockEthaneGas oilHydrogen51Methane98Ethene7823-156 more rows
What is cracking explain with example?
The decomposition of a compound by heat in the absence of air is called Pyrolysis. When pyrolysis occurs in alkanes, the process is termed as cracking. For example: Alkanes on heating under high temperature or in the presence of a catalyst in absence of air broken down into lower alkanes, alkenes and hydrogen.
What catalyst is used in cracking?
zeolitesModern cracking uses zeolites as the catalyst. These are complex aluminosilicates, and are large lattices of aluminium, silicon and oxygen atoms carrying a negative charge.
What is cracking used for?
What Is Cracking? Cracking is a technique used in oil refineries whereby large and complex hydrocarbon molecules are broken down into smaller and lighter components that are more useful for commercial or consumer use. Cracking is a critical stage in the process of refining crude oil.
What are types of cracking?
Various methods can be used for cracking, eg catalytic cracking and steam cracking: Catalytic cracking uses a temperature of approximately 550°C and a catalyst known as a zeolite which contains aluminium oxide and silicon oxide. Steam cracking uses a higher temperature of over 800°C and no catalyst.
What are the products of thermal cracking?
In thermal cracking, high temperatures (typically in the range of 450 °C to 750 °C) and pressures (up to about 70 atmospheres) are used to break the large hydrocarbons into smaller ones. Thermal cracking gives mixtures of products containing high proportions of hydrocarbons with double bonds - alkenes.
What is cracking used for?
What Is Cracking? Cracking is a technique used in oil refineries whereby large and complex hydrocarbon molecules are broken down into smaller and lighter components that are more useful for commercial or consumer use. Cracking is a critical stage in the process of refining crude oil.
Does cracking produce hydrogen?
Hydrogen can be produced by different processes like from fossil fuels (Steam methane reforming, coal gasification, cracking of natural gas); renewable resources (electrolysis, wind, etc.); nuclear energy (thermochemical water splitting).
What are the typical products of cracking of hydrocarbons?
The products of cracking include alkanes and alkenes , members of a different homologous series . An alkene is a hydrocarbon that contains a carbon-carbon double bond.
What is cracking organic chemistry?
Cracking is a reaction in which greater saturated hydrocarbon molecules are broken down into smaller, more functional hydrocarbon molecules, some o...
What is cracking used for?
Cracking is a chemical process which is used in oil refining. To produce by-products such as cooking oil, ethanol, liquefied petroleum gas, diesel...
What happens during cracking?
Cracking is the mechanism of petrochemistry, petroleum geology, and organic chemistry whereby complicated organic molecules such as kerogens or lon...
Why is cracking so important?
For two key reasons, cracking is important: It helps balance the availability of fractions with the demand for them. When cracking transforms bigge...
What is needed for cracking?
Cracking is the term given for splitting up large clusters of hydrocarbons into smaller and more functional pieces. This is accomplished by using h...
What is cracking in encyclopaedia?
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Cracking, in petroleum refining, the process by which heavy hydrocarbon molecules are broken up into lighter molecules by means ...
What is cracking in petroleum refining?
Cracking, in petroleum refining, the process by which heavy hydrocarbon molecules are broken up into lighter molecules by means of heat and usually pressure and sometimes catalysts. Cracking is the most important process for the commercial production of gasoline and diesel fuel.
What was the purpose of hydrocracking in the 1950s?
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.
When was thermal cracking first used?
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.
Who improved thermal cracking?
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.
What process took the less volatile fractions after distillation and subjected them to heat under pressure?
…with the introduction of thermal cracking. This process took the less volatile fractions after distillation and subjected them to heat under pressure, thus cracking the heavy molecules into lighter molecules and so increasing the yield of the most valuable fuel, petrol or gasoline. The discovery of this ability to tailor…
What is cracking in chemistry?
In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. The rate of cracking and the end products are strongly ...
What is hydrocarbon cracking?
Simply put, hydrocarbon cracking is the process of breaking a long-chain of hydrocarbons into short ones. This process might require high temperatures and high pressure. More loosely, outside the field of petroleum chemistry, the term “cracking” is used to describe any type of splitting of molecules under the influence of heat, ...
What are the products produced in a hydrocarbon reaction?
The products produced in the reaction depend on the composition of the feed, the hydrocarbon to steam ratio and on the cracking temperature and furnace residence time. Light hydrocarbon feeds such as ethane, LPGs or light naphtha give product streams rich in the lighter alkenes, including ethylene, propylene, and butadiene. Heavier hydrocarbon (full range and heavy naphthas as well as other refinery products) feeds give some of these, but also give products rich in aromatic hydrocarbons and hydrocarbons suitable for inclusion in gasoline or fuel oil.
What is the difference between hydrocracking and catalytic cracking?
Fluid catalytic cracking produces a high yield of petrol and LPG, while hydrocracking is a major source of jet fuel, Diesel fuel, naphtha, and again yields LPG. A large number of chemical reactions take place during the cracking process, most of them based on free radicals.
What happens when a furnace cracks?
A higher cracking temperature (also referred to as severity) favors the production of ethene and benzene, whereas lower severity produces higher amounts of propene, C4-hydrocarbons and liquid products. The process also results in the slow deposition of coke, a form of carbon, on the reactor walls. This degrades the efficiency of the reactor, so reaction conditions are designed to minimize this. Nonetheless, a steam cracking furnace can usually only run for a few months at a time between de-cokings. Decokes require the furnace to be isolated from the process and then a flow of steam or a steam/air mixture is passed through the furnace coils. This converts the hard solid carbon layer to carbon monoxide and carbon dioxide. Once this reaction is complete, the furnace can be returned to service.
What temperature does steam cracking take place?
Typically, the reaction temperature is very high, at around 850 °C, but the reaction is only allowed to take place very briefly.
How long does a cracking furnace run?
Nonetheless, a steam cracking furnace can usually only run for a few months at a time between de-cokings. Decokes require the furnace to be isolated from the process and then a flow of steam or a steam/air mixture is passed through the furnace coils. This converts the hard solid carbon layer to carbon monoxide and carbon dioxide.
What is cracking in chemistry?
Cracking (chemistry) In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon -carbon bonds in the precursors.
How does a cracking reaction work?
The hot catalyst vaporizes the feed and catalyzes the cracking reactions that break down the high-molecular weight oil into lighter components including LPG, gasoline, and diesel. The catalyst-hydrocarbon mixture flows upward through the riser for a few seconds, and then the mixture is separated via cyclones. The catalyst-free hydrocarbons are routed to a main fractionator for separation into fuel gas, LPG, gasoline, naphtha, light cycle oils used in diesel and jet fuel, and heavy fuel oil.
What are the products produced in a hydrocarbon reaction?
The products produced in the reaction depend on the composition of the feed, the hydrocarbon-to-steam ratio, and on the cracking temperature and furnace residence time. Light hydrocarbon feeds such as ethane, LPGs or light naphtha give product streams rich in the lighter alkenes, including ethylene, propylene, and butadiene. Heavier hydrocarbon (full range and heavy naphthas as well as other refinery products) feeds give some of these, but also give products rich in aromatic hydrocarbons and hydrocarbons suitable for inclusion in gasoline or fuel oil. Typical product streams include pyrolysis gasoline (pygas) and BTX .
What is the difference between hydrocracking and catalytic cracking?
Fluid catalytic cracking produces a high yield of petrol and LPG, while hydrocracking is a major source of jet fuel, diesel fuel, naphtha, and again yields LPG.
What is steam cracking?
Steam cracking is a petrochemical process in which saturated hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons. It is the principal industrial method for producing the lighter alkenes (or commonly olefins ), including ethene (or ethylene) and propene (or propylene ). Steam cracker units are facilities in which a feedstock such as naphtha, liquefied petroleum gas (LPG), ethane, propane or butane is thermally cracked through the use of steam in a bank of pyrolysis furnaces to produce lighter hydrocarbons.
What is cracking hydrocarbons?
Simply put, hydrocarbon cracking is the process of breaking a long chain of hydrocarbons into short ones. This process requires high temperatures. More loosely, outside the field of petroleum chemistry, the term "cracking" is used to describe any type of splitting of molecules under the influence of heat, catalysts and solvents, ...
What temperature does steam cracking take place?
Typically, the reaction temperature is very high, at around 850 °C, but the reaction is only allowed to take place very briefly.
Why is branched alkanes used in car engines?
The process is particularly useful in enhancing the octane rating of petrol, as branched alkanes burn more efficiently in a car engine than straight-chain alkanes.
Why is alkane conversion important?
This is a very important process for the petroleum and chemical industries. It enables straight chain alkanes to be converted into branched-chain alkanes, cyclohexanes and aromatic hydrocarbons which are used to enhance the octane number of petrol.
What are the advantages and disadvantages of cracking plants?
The advantages of this are that it cuts out the expensive distillation processes needed, for example to produce naphtha, and that it produces a wider range of products. However the disadvantage is that it may not produce the product that is needed in high enough yield. F or example, if you want a high yield of ethene it is better to make it from ethane or naphtha. This disadvantage can be overcome by having more than one plant on the same site.
Where are the largest continuous chemical sites in the world?
Figure 1 A view of the steam crackers at Ludwigshafen in Germany. The whole site is the largest continuous chemical site in the world. The steam crackers alone occupy 64 000 m2, which is about the size of 13 football fields. Naphtha is the feedstock and the main products are ethene and propene, used to make polymers.
How much does a steam cracking plant cost?
Modern steam cracking plants are very large, usually producing 1-2 million tonnes of products annually and several have been built recently that can have an output of nearly 3 million tonnes a year and cost about 1 billion dollars to build,
Which alkanes are more resistant to knock?
However, branched-chain alkanes, cycloalkanes and aromatic hydrocarbons are much more resistant to knock and straight-chain alkanes are converted into them in a series of processes in the refinery which are described in this unit. The resistance of petrol to knock is measured in terms of an octane rating (octane number).
What is the catalyst used for in catalytic cracking?
A catalyst allows lower reaction temperatures to be used. In fluidised catalytic cracking, the feedstock is gas oil which is vaporised and passed through a zeolite, produced as a fine powder (Unit 2), heated to about 700-800 K in the reactor. It is so fine that it behaves like a fluid and continuously flows out of the furnace with the cracking products. The temperature, residence time and the catalyst determine the product proportions. After cracking, the catalyst is separated from the products, regenerated by burning off deposited carbon in air (900 K), and subsequently recycled.
Why does my knee crack?
The answer to the first question has been delineated in detail below and the answer to the second question is that when there is Knee Cracking it is not the bones that are actually cracking as then it would lead to intense pain and you will not be able to move your knee. Thus, generally Knee Cracking do not cause any injury nor does it predispose you to any medical conditions, except when you already have a known diagnosis of a degenerating knee joint.
Why does my synovial fluid crack?
The cracking sound occurs when the joints are moved apart from each other creating a gap where synovial fluid forms a bubble. This bubble when it collapses or bursts causes the cracking sound.
How to Stop the Cracking Sound from Knee?
There are a few exercises which can be done to get rid of Knee Cracking. These exercises are:
Does cracking your knee cause injury?
Thus, generally Knee Cracking do not cause any injury nor does it predispose you to any medical conditions, except when you already have a known diagnosis of a degenerating knee joint. Advertisement.
Is cracking your knees a synovial fluid?
Advertisement. As discussed above, Knee Cracking is nothing but the synovial fluid producing the sound. 1 There is no involvement of the bones or ligaments and hence there is no chance of an injury to the ankles.
How much petrol is produced by cracking?
More then 50 % petrol is produced by cracking. It gives better quality of petrol in term of anti-knocking property.
How is thermal cracking done?
In this way the gasoline can be separated from the fractions. Thermal cracking is done both in liquid and vapor phase.
How is oil gas obtained?
Oil gas is obtained by the cracking kerosene oil by dropping it over red hot iron retort.
What is the temperature of a vapor phase cracking?
In a vapor-phase cracking, the temperature is 600 °C and the pressure is 3.5-10.5 atmosphere.
What is the alkene used for?
Simple alkene which are produced in the pyrolysis are used to prepare polymers. These polymers can be the polymers of petrol.
Why does my back make a snapping noise?
One way it may impact the backbone and its supporting structures is by causing ligaments or tendons to rub up against spinal bones. This friction results in a snapping noise you might describe as cracking.
What to do if your back cracks?
If you notice sudden, severe, or lingering back pain after you hear your back cracking or you hear cracking or popping sounds in your back after a fall, car accident, or another type of injury, see your doctor or a Los Angeles spine surgeon right away.
Can you crack your spine?
In fact, the source of your spinal cracking may not be found at all. However, if it’s accompanied by pain, see your doctor or a spine specialist, especially if you start to notice the cracking after a recent spine-related injury or following a procedure such as coflex surgery.
Overview
In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. The rate of cracking and the end products are strongly dependent on the temperature an…
History and patents
Among several variants of thermal cracking methods (variously known as the "Shukhov cracking process", "Burton cracking process", "Burton-Humphreys cracking process", and "Dubbs cracking process") Vladimir Shukhov, a Russian engineer, invented and patented, the first in 1891 (Russian Empire, patent no. 12926, November 7, 1891). One installation was used to a limited extent in Russia, but development was not followed up; In the first decade of the 20th century the Americ…
Cracking methodologies
Modern high-pressure thermal cracking operates at absolute pressures of about 7,000 kPa. An overall process of disproportionation can be observed, where "light", hydrogen-rich products are formed at the expense of heavier molecules which condense and are depleted of hydrogen. The actual reaction is known as homolytic fission and produces alkenes, which are the basis for the economical…
Fundamentals
Outside of the industrial sector, cracking of C-C and C-H bonds are rare chemical reactions. In principle, ethane can undergo homolysis:
CH3CH3 → 2 CH3•
Because C-C bond energy is so high (377 kJ/mol), this reaction is not observed under laboratory conditions. More common examples of cracking reactions involve retro-Diels-Alder reactions. Ill…
See also
• Steam reforming
• Catalytic reforming
External links
• Information on cracking in oil refining from howstuffworks.com
• www.shukhov.org/shukhov.html — Vladimir Grigorievich Shukhov biography