Alkenes Shell higher olefins process

Alkenes. At present alkene isomerization is an important step in the production of detergent alkylates (Shell higher olefin process see Sections 12.3 and 13.1.3).264 265 Ethylene oligomerization in the presence of a nickel(O) catalyst yields terminal olefins with a broad distribution range. C4-C6 and C2o+ alkenes, which are not suitable for direct alkylate production, are isomerized and subsequently undergo metathesis. Isomerization is presumably carried out over a MgO catalyst. 

The first large-scale application was the Phillips Triolefin Process (1966) in which propene was converted into ethene and 2-butene. Due to market changes the reverse process, in which propene is produced, became more attractive later. This process has been in operation since 1985. Another process is the Shell Higher Olefin Process (SHOP) in which ethene is oligomerized and the products are metathesized into detergent range olefins. The same company developed a process in speciality chemicals in which alpha-, omega-dienes are formed from cyclic alkenes. 

The Ni complex incorporating mixed-donor P/O-ligands find industrial application in the Shell Higher Olefin Process (SHOP) to yield a-alkenes, while the complex (71) has been shown to be active in the polymerization of olefins and will also tolerate functionalized monomers such as methyl methacrylate. Grubbs and coworkers have adapted the standard SHOP catalyst to yield a highly active family of catalysts (eg. 72) for the polymerization of low-branched polyethylene. This is in contrast to the diimine catalysts (Section 5.2) which lead to a more highly branched polyethylene. 

The alkene metathesis reaction see Alkene Metathesis) exchanges alkylidene groups between different alkenes, and is catalyzed by a variety of high oxidation state, early transition metal species (equation 40). The reaction is of interest because it is the strongest bond in the alkene, the C=C bond, that is broken during the reaction. It is also commercially important in the Shell higher olefins process and in the polymerization of cycloalkenes. It is relevant to this article because carbenes are the key intermediates, and the best-known catalyst, (1), is a carbene complex. 

In the Shell Higher Olefin Process (SHOP), ethylene is oligomerized by single-component nickel catalysts which make a-alkenes of very high linearity (almost 99%) and high... 

Hydroformylations catalyzed by ECo(CO) are typically run at high temperature (120-170 °C) and high pressure of a 1 1 mixture of CO E, (200-300 atm "synthesis gas"). These reactions are typically conducted with alkenes, sudi as propene, 1-octene, or a mixture of internal and alkenes generated as part of the Shell higher olefin process (SHOP). 

It is still unclear how the initiation step in alkene metathesis occurs and how the initial carbene forms. Commercial applications of metathesis include the triolefin process, in which propylene is converted to ethylene and butene, the neohexene process, in which the dimer of isobutylene, Me3CCH=CMe2, is metathesized with ethylene to give Me3CCH=CH2, an intermediate in the manufacture of synthetic musk, and a 1,5-hexadiene synthesis from 1,5-cy-clooctadiene and ethylene. Two other applications, SHOP and ROMP (Shell higher olefins process and ring-opening metathesis polymerization), are discussed in the next section. 

FIGURE 11.5 A schematic description of the Shell higher olefins process (SHOP). Keim s nickel catalyst gives 1-alkenes of various chain lengths. The subsequent steps allow the chain lengths to be manipulated to maximize the yield of C10-C14 products. Finally, SHOP alkenes are often hydroformylated, in which case the internal alkenes largely give the linear product, as discussed in Chapter 9. 

In the Shell Higher Olefins Process (SHOP) a much more efficient catalyst based on transition metal compounds (probably nickel) is used to effect the oligomerization. Initially about 30% of the ethene is converted into the desired olefins. The remainder (C -Cj and above are isomerized to internal alkenes and then converted into more useful fractions by metathesis. 

Figure 7.5 The four steps of Shell s higher olefin process (SHOP). Four- and 22-carbon-atom alkenes are taken as representative examples.

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