Oligomerization of higher a-olefins

The system TiCl4-R AlCl3 (n = 1-3, R = alkyl) oligomerizes 1-hexene [940]. Modification with halogenohydrocarbons, phosphoro- and sulfuroorganic compounds, alkali metal hydrides, and nickel salts gave relative catalysts in the 1-decene [783], CH2=CH-(CH2) -CH3 (n = 1-5) [941], Cg-Cna-olefins [942], and Cj-Cg a-olefin oligomerizations [943]. 

The mixed catalytic system TiCl4-Ti(OBu)4-Zr(OBu)4—EtsAljCU (1 2 1 10) oligomerizes with high-yield 1-decene to a product having an average molecular weight of M = 356 [784,838]. 

Octene trimers are the main products of the 1-octene oligomerization in the presence of the system TiCl4-Et3Al2Cl3, and ZrCU modified with AICI3 oligomerizes 1-decene to trimers and tetramers with a yield of 93% [944]. All of these titanium and zirconium catalysts have one deficiency they promote alkylation of olefins with aromatic solvents [944]. 

The sulfonated ylide nickel complex 4 (see structures 1—4, reactions 64A) activated with Et2AlOEt co-oligomerizes ethylene with higher olefins, for example, 1-hexene, 1-heptene, 1-octene, and 1-decene. Olefin insertion into the Ni—H bond is nonselective. The chain propagation step, a-olefin insertion into the nickel-alkyl bond, is also nonselective. The Ni—C bond reactivity in the olefin insertion reaction depends on the structure of an alkyl group bonded to the nickel ion. 

CoNH2(PPh3)3Co(N2)(PPh3)3 2-methyl-l-pentene (65.3%), 4-methyl-2-pentene (17%), 2-methyl-2-pentene (2.7%), trans-3-methyl-2-pentene (2.2%) 682 

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Catalysts of type I containing 00 chelate ligands are effective catalysts for the linear oligomerization of higher a-olefins. Using (3 R =R =Cp3), 1-butene can be dimerized in 82% yield to linear octenes . The bulky olefin neohexene can be converted selectively into linear dimers with the same catalyst activated by BF3. 

With increasing reaction pressure, the molecular weight of oligomers as well as conversion to linear a-olefins increases. An increase in the ethylene pressure also inhibits the ethylene co-oligomerization with higher a-olefins. 

Shell Higher Olefin Process) plant (16,17). C -C alcohols are also produced by this process. Ethylene is first oligomerized to linear, even carbon—number alpha olefins using a nickel complex catalyst. After separation of portions of the a-olefins for sale, others, particularly C g and higher, are catalyticaHy isomerized to internal olefins, which are then disproportionated over a catalyst to a broad mixture of linear internal olefins. The desired fraction is... 

A related study used the air- and moisture-stable ionic liquids [RMIM][PFg] (R = butyl-decyl) as solvents for the oligomerization of ethylene to higher a-olefins [49]. The reaction used the cationic nickel complex 2 (Figure 7.4-1) under biphasic conditions to give oligomers of up to nine repeat units, with better selectivity and reactivity than obtained in conventional solvents. Recycling of the catalyst/ionic liquid solution was possible with little change in selectivity, and only a small drop in activity was observed. 

Another approach is to separate the products from the homogeneous catalyst using a two phase liquid system. For example, this method is used in the oligomerization step of the Shell Higher Olefins Process for the manufacture of linear a-olefins.5,9-11,330 A polar nickel catalyst containing a P- chelate ligand is dissolved in a polar solvent e.g. 1,4-butanediol, which is immiscible with higher oc-olefins, and recovery of the catalyst is easily achieved by simple phase separation. 

The oligomerization of ethylene to higher a-olefins is catalyzed by nickel(II) chelate complexes such as (22-XXXIV). The active species is a nickel hydride, generated in situ,... 

The first oligomerization step uses a catalytic one-step process similar to Chevron s process. This is operated at 160-275 °C and 13-27 MPa of ethylene pressure. After the reaction, the catalyst is destroyed by hydrolysis. The product mixture, consisting mainly of C4-C10 a-olefms, is distilled and separated into the C4-C10 and C12-C18 fractions. The latter can be used directly. The lower a-olefms are subjected to transalkylation with higher aluminium alkyls, liberating the higher a-olefins. The higher aluminium alkyls are produced in the stoichio-... 

Propene and higher a-olefins also may be dimerized or oligomerized by these catalysts. Generally, reactivity is much lower than that of ethylene and decreases in the order ethylene propylene > 1-butene > 1-hexene > 1-octene > 1-decene. Also the selectivity is lower and mainly branched dimers or oligomers are formed. ... 

In the present review attention is only paid to heterogeneous catalysts. Table 4 (page 268) constitutes a summary of heterogeneous catalyst systems in oligomerization of higher olefins. 

P—0)NiEt(PCy3)]/ The related P—0 nickel chelate complex (7) in the presence of EtjAlOEt at 90 C co-oligomerizes ethylene with higher a -olefins. Analysis of the products reveals that the insertion of olefins gives both primary and secondary... 

Ethylene could also be oligomerized to normal a-olefins in aqueous CHjOH containing 0.5-20% water in the presence of nickel ylide [214]. The water improved the separation of the catalyst phase from the olefin-rich product phase, increased the purity of the a-olefin product, shifted the product distribution toward higher a-olefins and not affect the catalytic activity. 

When co-oligomerization of ethylene and higher a-olefin takes place, all these steps (reactions 71-73) result in the formation of heterogeneous reaction products. The structure of these products depends on the position of the higher olefin unit in an oligomer chain and on the mode of olefin insertion into Ni-H of Ni-C bonds, primary or secondary. 

This reaction occurred in all cases of ethylene-higher a-olefin oligomerization the added a-olefin was partially isomerized to cis- and trans-2-olefins. Conversions in these isomerization reactions varied from 2.5 to 6%. Cis- and trans-2-olefins with linear chains are also formed in ethylene homooligomerization reaction [227]. Their presence in ethylene oligomers can be similarly explained as a secondary reaction (reaction 81) with the participation of the ethylene oligomers. Olefins with other internal double bonds cannot be formed in reaction (14) from a-olefins. Their possible formation from other olefins with internal double bonds (e.g., formation of 3-olefins from 2-olefins, etc.) in reactions analogous to reaction... 

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