In petroleum geology and chemistry, cracking is the process whereby complex organic molecules (e.g. kerogens or heavy hydrocarbons) are converted to simpler molecules (e.g. 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 and presence of any catalysts. Petroleum geology is a term used to refer to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil exploration). ... Chemistry (in Greek: χημεία) is the science of matter and its interactions with energy and itself (see physics, biology). ... An organic compound refers to any member of a large class of chemical compounds whose molecules contain carbon, with exception of carbides, carbonates and carbon oxides. ... In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... Kerogens are chemical compounds, often found to be formed by the low-grade metamorphism (i. ... In chemistry, a hydrocarbon is any chemical compounds that consists only of carbon (C) and hydrogen (H). ... General Name, Symbol, Number Carbon, C, 6 Chemical series Nonmetals Group, Period, Block 14 (IVA), 2, p Density, Hardness 2267 kg/m3 0. ... In chemistry, a chemical bond is the force, which holds together atoms in molecules or crystals. ... The reaction rate for a reactant or product in a particular reaction is defined as the amount (in moles or mass units) per unit time per unit volume that is formed or removed. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... A catalyst (Greek: καταλύτης, catalytis) is a substance that accelerates the rate of a chemical reaction, at some temperature, but without itself being transformed or consumed by the reaction (see also catalysis). ...

Applications

Cracking processes allow the production of "light" products (such as LPG and gasoline) from heavier crude oil distillation fractions (such as gas oils and distillation residues). Fluid Catalytic Cracking (FCC for short) produces a high yield of petrol and LPG, while thermal cracking is currently used to "upgrade" very heavy fractions ("upgrading", "visbreaking"), or to produce light fractions or distillates, burner fuel and/or petroleum coke. Liquified Petroleum Gas (also called Liquefied Petroleum Gas, Liquid Petroleum Gas, LPG, or LP Gas) is a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing fluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer. ... Petrol (gasoline in the United States and Canada) is a petroleum-derived liquid mixture consisting primarily of hydrocarbons, used as fuel in internal combustion engines. ... Nodding donkey pumping an oil well near Sarnia, Ontario, 2001 Petroleum (from Latin petrus – rock and oleum – oil), mineral oil, or crude oil, sometimes colloquially called black gold, is a thick, dark brown or greenish flammable liquid, which exists in the upper strata of some areas of the Earths... Fractional distillation is the separation of a mixture of compounds by their boiling point, by heating to high enough temperatures. ... Kerosene, gas oil, paraffin (not the waxy solid of that name) is a colorless flammable hydrocarbon liquid. ... Petrol pumps in Germany Petrol (commonly known as gasoline in North America, and sometimes also called motor spirit) is a petroleum-derived liquid mixture consisting primarily of hydrocarbons, used as fuel in internal combustion engines. ... Liquified Petroleum Gas (also called Liquefied Petroleum Gas, Liquid Petroleum Gas, LPG, or LP Gas) is a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing fluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer. ... Categories: Possible copyright violations ...

Fluid Catalytic Cracking

Fluid catalytic cracking is a commonly used process and a modern oil refinery will typically include a cat cracker, particularly refineries in the USA due to the high demand for gasoline. The process was first used in around 1942, and employs a powdered catalyst. Initial process implementations were based on a reactor where the catalyst particles were suspended in an ascendant flow of feed hydrocarbons in a fluidized bed. In newer process variants, the contact time between the catalyst and the feed is greatly reduced in order to reduce the amount of coke deposited on the catalyst. The actual reactor is an ascendant-flow pipe called the "riser" in which pre-heated feed meets hot catalyst particles for just a few seconds before the catalyst is separated from the hydrocarbon using a cyclone, contacted with steam to strip off the remaining hydrocarbon and stop the reaction, and then transported into a fluidized-bed regenerator where air (or in some cases air plus oxygen) is used to burn off the coke to restore catalyst activity and also provide the necessary heat for the next reaction cycle, cracking being an endothermic reaction. View of the Shell/Valero Martinez oil refinery An oil refinery is an industrial process plant where crude oil is processed and refined into useful petroleum products. ... Petrol (gasoline in the United States and Canada) is a petroleum-derived liquid mixture consisting primarily of hydrocarbons, used as fuel in internal combustion engines. ... 1942 was a common year starting on Thursday (link will take you to calendar). ... A catalyst (Greek: καταλύτης, catalytis) is a substance that accelerates the rate of a chemical reaction, at some temperature, but without itself being transformed or consumed by the reaction (see also catalysis). ... Cyclonic separation is a method of removing particles from an air stream without having to use filters. ... General Name, Symbol, Number Oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16 (VIA), 2, p Density, Hardness 1. ... In chemistry, an endothermic reaction is one that requires heat to break the bonds of the reactants. ...

Hydrocracking

Hydrocracking is a catalytic cracking process assisted by the presence of an elevated partial pressure of hydrogen. The products resulted are saturated hydrocarbons; depending on the process severity (temperature, pressure, catalyst activity) these products range from ethane, LPG to heavier hydrocarbons comprising mostly of isoparaffins. Hydrocracking is normally facilitated by a bifunctional catalyst that is capable of rearranging and breaking hydrocarbon chains as well as adding hydrogen to aromatics and olefins to produce naphthenes and alkanes. Approximately, the partial pressure of a gas in atmospheres in a mixture or solution is what would be the pressure of that gas if all other components of the mixture or solution suddenly vanished without its temperature changing. ... General Name, Symbol, Number Hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1, s Density, Hardness 0. ... The term saturation generally means thoroughly full, and can refer to the following: In chemistry, see saturation (chemistry) for a number of meanings. ... Ethane is a chemical compound with chemical formula C2H6. ... An alkane in organic chemistry is a type of hydrocarbon in which the molecule has the maximum possible number of hydrogen atoms and so has no double bonds (they are saturated). ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... An olefin is an alkene hydrocarbon. ... Cycloalkanes are chemical compounds with a one or more rings of carbons to which hydrogens are attached according to the formula CnH2n. ... An alkane in organic chemistry is a type of hydrocarbon in which the molecule has the maximum possible number of hydrogen atoms and so has no double bonds (they are saturated). ...

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). A petrochemical is any chemical derived from fossil fuel. ... In chemistry, a hydrocarbon is any chemical compounds that consists only of carbon (C) and hydrogen (H). ... An alkene is one of the three classes of unsaturated hydrocarbons that contain at least one carbon-carbon double bond and have the general molecular formula of CnH2n (the other two being alkynes and arenes). ... An olefin is an alkene hydrocarbon. ... Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ... Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ... Propylene, also known as propene, is a colorless flammable gas with chemical formula C3H6 having a garlic odor. ... Propylene, also known as propene, is a colorless flammable gas with chemical formula C3H6 having a garlic odor. ...

In steam cracking, a gaseous or liquid hydrocarbon feed is diluted with steam and then briefly heated in a furnace. Typically, the reaction temperature is very hot—over 900°C—but the reaction is only allowed to proceed for a few tenths of a second before being quenched by contact with a colder fluid.

The products produced in the reaction depend on the composition of the feed, the hydrocarbon to steam ratio and on the cracking temperature & furnace residence time. Light hydrocarbon feeds (such as ethane, LPGs or light naphthas) give product streams rich in the lighter alkenes, including ethylene, propylene, and butadiene. Heavier hydrocarbon (full range & 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. The higher cracking temperature (also referred to as severity) favours the production of ethene and benzene, whereas lower severity produces relatively higher amomunts of propene, C4-hydrocarbons and liquid products. Ethane is a chemical compound with chemical formula C2H6. ... Naphtha is a group of various volatile flammable liquid hydrocarbon mixtures used primarily as feedstocks in refineries for the reforming process and in the petrochemical industry for the production of olefins in steam crackers. ... Butadiene can refer to either one of two hydrocarbon chemical compounds which are alkenes that are isomers of each other. ... An aromatic hydrocarbon (abbreviated as AH), or arene is a hydrocarbon, the molecular structure of which incorporates one or more planar sets of six carbon atoms that are connected by delocalised electrons numbering the same as if they consisted of alternating single and double covalent bonds. ... Petrol (gasoline in the United States and Canada) is a petroleum-derived liquid mixture consisting primarily of hydrocarbons, used as fuel in internal combustion engines. ... Nodding donkey pumping an oil well near Sarnia, Ontario, 2001 Petroleum (from Latin petrus – rock and oleum – oil), mineral oil, or crude oil, sometimes colloquially called black gold, is a thick, dark brown or greenish flammable liquid, which exists in the upper strata of some areas of the Earths...

The process also results in the slow deposition of coke, a form of carbon, on the reactor walls. This degrades the effectiveness 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. Coke is a solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal from which the volatile constituents (including water, coal-gas and coal-tar) are driven off by baking in an airless oven at temperatures as high as 1,000 degrees Celsius so that the fixed carbon and... General Name, Symbol, Number Carbon, C, 6 Chemical series Nonmetals Group, Period, Block 14 (IVA), 2, p Density, Hardness 2267 kg/m3 0. ...

Two extremes of the thermal cracking in terms of product range are represented by the high-temperature process called "pyrolysis" (ca. 750-900°C) which produces valuable ethylene and other feeds for the petrochemical industry, and the milder-temperature "delayed coking" (ca. 500°C) which can produce, under the right conditions, valuable "needle coke", a highly crystalline petroleum coke used in the production of electrodes for the steel and aluminum industries. Pyrolysis is formally defined as chemical decomposition of organic materials by heating in the absence of oxygen. ... Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ... An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ... Steel framework Steel is a metal alloy whose major component is iron, with carbon being the primary alloying material. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13 (IIIA), 3, p Density, Hardness 2700 kg/m3, 2. ...

Chemistry

"Cracking" breaks larger molecules into smaller ones. This can be done with a thermic or catalytic method. The thermal cracking process follows a homolytic mechanism, that is, bonds break symmetrically and thus pairs of free radicals are formed. The catalytic cracking process involves the presence of acid catalysts (usually solid acids such as silica-alumina and zeolites) which promote a heterolytic (asymmetric) breakage of bonds yielding pairs of ions of opposite charges, usually a carbocation and the very unstable hydride anion. Carbon-localized free radicals and cations are both highly unstable and undergo processes of chain rearrangement, C-C scission in position beta (i.e., cracking) and intra- and intermolecular hydrogen transfer or hydride transfer. In both types of processes, the corresponding reactive intermediates (radicals, ions) are permanently regenerated, and thus they proceed by a self-propagating chain mechanism. The chain of reactions is eventually terminated by radical or ion recombination. In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ... An acid (often represented by the generic formula AH) is typically a water-soluble, sour-tasting chemical compound. ... A catalyst (Greek: καταλύτης, catalytis) is a substance that accelerates the rate of a chemical reaction, at some temperature, but without itself being transformed or consumed by the reaction (see also catalysis). ... Silica-alumina, also known as alumino-silicate(s). ... Zeolite Zeolites (Greek, zein,to boil;lithos,a stone) are minerals that have a porous structure. ... An ion is an elementary particle or system of elementary particles with a net electric charge. ... A cation is an ion with positive charge. ... A Hydride is a chemical compound or form of a bond between hydrogen with a metal usually found in group 1 of the Periodic table, usually with a more electropositive element or group. ... An anion is an ion with negative charge. ... Intramolecular describes a process or characteristic limited within the structure of a single, or each molecule; a property or phenomenon limited to the extent of a single, or each molecule. ... Intermolecular describes a process or characteristic that extends from one molecule to an adjacent one; a property or phenomenon that extends from one molecule to another. ...

Catalytic Cracking

Catalytic cracking uses a catalyst to aid the process of breaking down large hydrocarbon molecules into smaller ones. During this process, less reactive and therefore more stabile and longer lived intermediate cations accumulate on the catalysts' active sites generating deposits of carbonaceous products generally (and in many cases inappropriately) known as coke. Such deposits need to be removed (usually by controlled burning) in order to restore catalyst activity. A catalyst (Greek: καταλύτης, catalytis) is a substance that accelerates the rate of a chemical reaction, at some temperature, but without itself being transformed or consumed by the reaction (see also catalysis). ... The active site of an enzyme is the binding site where catalysis occurs. ... Carbonaceous is the defining attribute of a substance rich in carbon. ... Coke is a solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal from which the volatile constituents (including water, coal-gas and coal-tar) are driven off by baking in an airless oven at temperatures as high as 1,000 degrees Celsius so that the fixed carbon and...

Thermal Cracking

In thermal cracking elevated temperatures are used. 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.

A large number of chemical reactions take place during steam cracking, most of them based on free radicals. Computer simulations aimed at modeling what takes place during steam cracking have included hundreds or even thousands of reactions in their models. The major sorts of reactions that take place, with examples, include: A chemical reaction is a process involving one, two or more substances (called reactants), characterized by a chemical change and yielding one or more product(s) which are different from the reactants. ... In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ... The tower of a personal computer (specifically a Power Mac G5). ... A simulation is an imitation of some real device or state of affairs. ...

Initiation reactions, where a single molecule breaks apart into two free radicals. Only a small fraction of the feed molecules actually undergo initiation, but these reactions are necessary to produce the free radicals that drive the rest of the reactions. In steam cracking, initiation usually involves breaking a chemical bond between two carbon atoms, rather than the bond between a carbon and a hydrogen atom. In chemistry, a chemical bond is the force, which holds together atoms in molecules or crystals. ... General Name, Symbol, Number Hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1, s Density, Hardness 0. ...

CH₃CH₃ → 2 CH₃•

Hydrogen abstraction, where a free radical removes a hydrogen atom from another molecule, turning the second molecule into a free radical.

CH₃• + CH₃CH₃ → CH₄ + CH₃CH₂•

Radical decomposition, where a free radical breaks apart into two molecules, one an alkene, the other a free radical. This is the process that results in the alkene products of steam cracking.

CH₃CH₂• → CH₂=CH₂ + H•

Radical addition, the reverse of radical decomposition, in which a radical reacts with an alkene to form a single, larger free radical. These processes are involved in forming the aromatic products that result when heavier feedstocks are used.

CH₃CH₂• + CH₂=CH₂ → CH₃CH₂CH₂CH₂•

Termination reactions, which happen when two free radicals react with each other to produce products that are not free radicals. Two common forms of termination are recombination, where the two radicals combine to form one larger molecule, and disproportionation, where one radical transfers a hydrogen atom to the other, giving an alkene and an alkane.

CH₃• + CH₃CH₂• → CH₃CH₂CH₃

CH₃CH₂• + CH₃CH₂• → CH₂=CH₂ + CH₃CH₃

History

The first thermal cracking method, the Burton process, was invented by William M. Burton; the oil industry first using it to produce gasoline in 1913. The Burton process is a thermal cracking process invented by William M. Burton; the oil industry first used it to produce gasoline in 1913. ... Petrol (gasoline in the United States and Canada) is a petroleum-derived liquid mixture consisting primarily of hydrocarbons, used as fuel in internal combustion engines. ... 1913 is a common year starting on Wednesday. ...

Catalytic cracking, based upon a process developed by Dr. Alex Golden Oblad at Standard Oil of Indiana has been used from around 1936. Typical catalysts include alumina, silica, zeolites, and various types of clay. Alex Golden Oblad (1909 – 2001) was a prominent chemist and chemical engineer principally recognized for his pioneering work in catalysis and catalytic chemistry. ... Amoco was a United States oil company formed from the dissolution of Standard Oil. ... 1936 was a leap year starting on Wednesday (link will take you to calendar). ... Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Categories: Silicate minerals | Mineral stubs ...

See also

More details about the cracking mechanism are provided in the alkane article. An alkane in organic chemistry is a saturated hydrocarbon, that is, a hydrocarbon in which the molecule has the maximum possible number of hydrogen atoms and so has no double bonds. ...