Olefins are important industrial chemicals. Elfarra, in Advances in Molecular Toxicology, 2018 Abstract Following several expansions, the current SHOP operating capacity is 330 000 metric tons per year at Shell’s Stanlow (UK) site, and 920 000 mt yr −1 at Geismar, Louisiana, giving an overall capacity of roughly 1.25 million mt of Neodene® per year. The initial SHOP capacity in 1977 was 104 000 mt yr −1 of linear olefins, which Shell currently markets under the trade name Neodene®. 6 By reengineering the process, Shell can use SHOP to tailor its otherwise fixed product distribution to meet changes in market demand. Internal olefins between C11 and C18 are collected and the remaining heavy and light olefins are recycled back into the isomerization unit. The metathesized products are linear internal olefins with a broad chain-length distribution. The mixed olefin stream from the isomerization unit is fed to a MoO 3/Al 2O 3 metathesis catalyst operating at 100–125 ☌ and 10 bar. The heavier and lighter olefins are recombined in an isomerization unit that converts the terminal olefins to internal positions, providing a mixture comprised of linear internal olefins containing fewer than 6 carbons or greater than 18 carbons. The linear olefins then enter a distillation unit that isolates the highest value products (C6–C18). These olefins are immiscible with the polar solvent and are readily separated from the catalyst solution. In the first step of the process, ethylene is oligomerized with a homogeneous nickel catalyst in 1,4-butanediol solvent to form a fixed distribution of linear alpha olefins with even carbon numbers from C4–C40. Overall, SHOP converts ethylene into linear olefins. Next to OCT®, olefin metathesis finds its largest scale application as a component in the multistep Shell Higher Olefins Process (SHOP). Edgecombe, in Polymer Science: A Comprehensive Reference, 2012 4.30.2.2 SHOP Alternatively, products such as some varnishes or wood floor finishes purposely incorporate molecules with double bonds, so that a polymerization reaction will occur and form the desired hard film on the surface.Ī. For the same reason, it is not usually desirable to have alkenes in finished products, as they could react, affecting the viscosity and other properties of the fuel. Because of this tendency to react, alkenes are not commonly found in crude oils. Double bonds are more reactive than their single bond counterparts, and are particularly susceptible to addition reactions, including polymerization. Another important property of double bonds is their reactivity. The double bond is a shorter, and therefore stronger, bond than the analogous single bond a greater amount of energy is required to break a double bond than to break a single bond. Using butene as an example, there are four isomers for the alkene (1-butene, cis-2-butene, trans-2-butene, and isobutene), whereas there are only two for the corresponding alkane (n-butane and isobutane).Īlkenes are defined by the carbon-to-carbon double bond, and it is this bond that is responsible for many of the specific properties of the alkenes. The presence of a double bond therefore will result in a significantly greater number of isomers as compared with the analogous alkane. The difference between these isomers depends on whether the methyl groups are on the same side (cis) of the double bond, or on opposite sides (trans). Example of stereoisomerism with cis- and trans-2-butene. The naming system for alkenes is similar to that for alkanes, with the termination -ene indicating that the compound is an alkene.įIGURE 3-10. The simplest molecule in the alkene series is ethene, more commonly known as ethylene (C 2H 4) it is followed by propene, also commonly referred to as propylene (C 3H 6), butene, also known as butylene (C 4H 8), pentene (C 5H 10), and so on. Alkadienes often are encountered in fire debris analysis as pyrolysis products of some polymers (see Subsections 4.4 and 12.3 for more detail).Īs with alkanes, alkenes form a homologous series consisting of molecules of increasing molecular weight by the addition of methylene (–CH2–) units. When an alkene has more than one double bond, the nomenclature changes to alkadiene, alkatriene, and so on. As a matter of fact, olefins include all aliphatic (both acyclic and cyclic) hydrocarbons having one or more carbon-to-carbon double bonds: alkenes, cycloalkenes, and polyenes (compounds exhibiting more than one double bond). Olefins encompass a larger set of compounds as shown in Figure 3-6, including alkenes. According to IUPAC, alkenes include all aliphatic hydrocarbons exhibiting one and only one double bond. The terms alkenes and olefins often are used interchangeably however, this is not quite accurate.
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