Full Answer
What is steam cracking in chemistry?
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 lighter alkenes (olefins), including ethene (or ethylene) and propene (or propylene) (Figure 3.2).
What is cracking of hydrocarbons GCSE?
Cracking is a reaction in which larger hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated: the original starting hydrocarbons are alkanes. the products of cracking include alkanes and alkenes , members of a different homologous series.
What is thermal cracking GCSE?
Thermal cracking uses harsh conditions like high temperature and high pressure. It breaks the alkanes into a high percentage of alkenes and comparatively few alkanes. Thermal cracking is done at about 1,000 degrees Celcius and 70 atm pressure.
What is catalytic cracking GCSE?
Catalytic cracking involves heating the hydrocarbon molecules to around 470 – 550°C to vaporise them. The vapours then pass over a hot powdered catalyst of aluminium oxide.
Why is cracking used in the oil industry GCSE?
Cracking allows large hydrocarbon molecules to be broken down into smaller, more useful hydrocarbon molecules. Fractions containing large hydrocarbon molecules are heated to vaporise them.
What are the conditions for steam 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.
Is steam cracking the same as thermal cracking?
Thermal cracking is currently used to "upgrade" very heavy fractions or to produce light fractions or distillates, burner fuel and/or petroleum coke. Two extremes of the thermal cracking in terms of the product range are represented by the high-temperature process called "steam cracking" or pyrolysis (ca.
What are the two types of cracking?
Cracking in chemistry is of two types: Thermal cracking and Catalytic Cracking. It is a critical technique used in the refining process of crude oil.
How does thermal cracking work?
Thermal cracking is a process in which hydrocarbons present in crude oil are subject to high heat and temperature to break the molecular bonds and breaking down long-chained, higher-boiling hydrocarbons into shorter-chained, lower-boiling hydrocarbons.
What is thermal cracking and catalytic cracking?
Definition. Thermal Cracking: Thermal cracking is the process of breaking down large compounds into small compounds at high temperatures and high pressures. Catalytic Cracking: Catalytic cracking is the breakdown of large compounds into small hydrocarbons using an acid catalyst.
Why is catalytic cracking important?
Catalytic cracking is an important process in the oil industry where petroleum vapor passes through a low-density bed of catalyst, which causes the heavier fractions to 'crack' producing lighter more valuable products. In the petrochemicals industry they are used for producing polyolefins on a very large scale.
What type of reaction is cracking?
Cracking is an example of a thermal decomposition chemical reaction.
How are hydrocarbons cracked?
Cracking is the name given to breaking up large hydrocarbon molecules into smaller and more useful bits. This is achieved by using high pressures and temperatures without a catalyst, or lower temperatures and pressures in the presence of a catalyst.
What is it meant by the term cracking?
You use cracking to describe something you think is very good or exciting. [British, informal]
Why do we crack hydrocarbons?
Cracking larger hydrocarbons produces smaller alkanes that can be converted into petrol. It also produces small alkenes, which are used make many other useful organic chemicals (petrochemicals), especially plastics.
Why is cracking hydrocarbons important?
Since cracking converts larger hydrocarbons into smaller hydrocarbons, the supply of fuels is improved. This helps to match supply with demand. It produces alkenes. Alkenes are more reactive than alkanes.
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 ...
What temperature does steam cracking occur?
Typically, the reaction temperature is very high, at around 850 °C. The reaction occurs rapidly: the residence time is on the order of milliseconds.
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 is the difference between steam cracking and olefins?
Olefins are useful precursors to myriad products. Steam cracking is the core technology that supports the largest scale chemical processes, i.e. ethylene and propylene.
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.
Where does the cracked gas go?
all of the cold cracked gas stream goes to the demethanizer tower. The overhead stream from the demethanizer tower consists of all the hydrogen and methane that was in the cracked gas stream. Cryogenically (−250 °F (−157 °C)) treating this overhead stream separates hydrogen from methane.
What is the bottom stream of a C3 splitter?
The overhead stream from the C3 splitter is product propylene and the bottom stream is propane which is sent back to the furnaces for cracking or used as fuel. The bottom stream from the depropanizer tower is fed to the debutanizer tower.
What temperature is used for cracking?
Various methods can be used for cracking, eg catalytic cracking and steam cracking: 1 Catalytic cracking uses a temperature of approximately 550°C and a catalyst known as a zeolite which contains aluminium oxide and silicon oxide 2 Steam cracking uses a higher temperature of over 800°C and no catalyst
Why is cracking important?
Reasons for cracking. Cracking is important for two main reasons: It helps to match the supply of fractions with the demand for them. It produces alkenes, which are useful as feedstock for the petrochemical industry.
What is cracking and alkenes?
Cracking is a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated: the original starting hydrocarbons are alkanes. the products of cracking include alkanes and alkenes, members of a different homologous series.
What happens when alkenes react with bromine?
Alkenes will react with bromine water and turn it from orange/brown to colourless. This is the way to test for a double C=C bond in a molecule.
What is cracking hydrocarbons?
Cracking allows large hydrocarbon molecules to be broken down into smaller, more useful hydrocarbon molecules. Fractions containing large hydrocarbon molecules are heated to vaporise them. They are then:
What are the hydrocarbons formed by cracking?
The process is as follows: Some of the smaller hydrocarbons formed by cracking are used as fuels (eg large chains are often cracked to form octane for petrol, which is in high demand), and the alkenes are used to make polymers in the manufacturing of plastics.
Why is cracking important?
Reasons for cracking. Cracking is important for two main reasons: it helps to match the supply of fractions with the demand for them. it produces alkenes, which are useful as feedstock for the petrochemical industry.
What is cracking in hydrocarbons?
Cracking is a reaction in which larger hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated:
What temperature is used for cracking?
Various methods can be used for cracking, eg catalytic cracking and steam cracking: 1 Catalytic cracking uses a temperature of approximately 550°C and a catalyst known as a zeolite which contains aluminium oxide and silicon oxide 2 Steam cracking uses a higher temperature of approximately 550°C and no catalyst
Why is cracking important?
Reasons for cracking. Cracking is important for two main reasons: it helps to match the supply of fractions with the demand for them. it produces alkenes, which are useful as feedstock for the petrochemical industry.
What is cracking and alkenes?
Cracking is a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated: The total number of carbon and hydrogen atoms in the products is the same as in the starting alkane.
What are the products of cracking?
the products of cracking include alkanes and alkenes, members of a different homologous series. For example, hexane can be cracked to form butane and ethene: hexane → butane + ethene. C6H14 → C4H10 + C2H4. The total number of carbon and hydrogen atoms in the products is the same as in the starting alkane.
