Dimerization of ethylene to butenes

Feed and product quality from dimerization of ethylene to 1-butene ... 

The 7r-back donation stabilizes the alkene-metal 7c-bonding and therefore this is the reason why alkene complexes of the low-valent early transition metals so far isolated did not catalyze any polymerization. Some of them catalyze the oligomerization of olefins via metallocyclic mechanism [25,30,37-39]. For example, a zirconium-alkyl complex, CpZrn(CH2CH3)(7/4-butadiene)(dmpe) (dmpe = l,2-bis(dimethylphosphino)ethane) (24), catalyzed the selective dimerization of ethylene to 1-butene (Scheme I) [37, 38]. 

Ta1 adducts with ethylene have been obtained as highly air sensitive solids by reduction of the corresponding Ta111 compounds under argon (equation 85),292 or by reductive elimination of H2 from [TaH2ClL4] (Scheme 9). A similar procedure, but under dinitrogen, gave Tav nitrenes (Section 34.2.3.6). The same Tam precursor (60) provided o alkyl derivatives (equation 86). Complex (63) catalyzes the selective dimerization of ethylene to 1-butene. 

Ceder, R., Muller, G., Saleh, J. and Vidal, J. Catalytic dimerization of ethylene to 1-butene by square-planar nickel-complexes. J. Mol. Catal., 1991, 68, 23-31. 

Dimerization of Ethylene to 1-Butene Catalyzed by Titanium Complexes... 

Dimerization of ethylene. Rhodium(IlI) chloride supported on silica gel is an active heterogeneous catalyst for dimerization of ethylene to 1-butene and then to 2-butene the transfcis ratio is 2.9. The active catalyst may have the structure depicted in (1). ... 

As the next example of soft catalysis, we shall discuss the dimerization of ethylene to 1-butene, which is catalyzed by rhodium complexes in a redox cycle (Scheme 2-6). The active Rh catalyst A undergoes oxidative addition of HCl and insertion of ethylene into the Rh-H bond to give the Rh alkyl complex B. The following ethylene insertion reaction is the rate-determining step and is favored by the medium-hard Rh center. The resulting Rh butyl complex C has a hard-soft dis-... 

The dimerization of ethylene to form a mixture of butene isomers is not particularly useful in the field of commodity chemicals at this time because this mixture of butenes is usually cheaper than ethylene. Selective dimerization of ethylene to 1-butene using a titanium catalyst is practiced, but this chemistry occurs through metallacycles and is described in the next section. The dimerization of propylene by migratory insertion chemistry typically produces the mixture of isomeric olefins shown in Equation 22.32. Four skeletal isomers of the intermediate metal alkyl can arise from the two different directions of M-H insertion, followed by two different inodes of M-R insertion. The dimerization of ethylene is particularly fast when catalyzed by the combination of NiBr(-r) -C3H5)(PCy3) and EtAlCl this dimerization in chlorobenzene at 25 °C occurs witii turnover frequencies up to 60,000 per second. The more selective dimerization of propene to 2,3-dimethylbutene is conducted on an industrial scale with titanium catalysts, again via metallac clic intermediates described in the next section. 

Alkene and Alkyne Dimerization and Trimerization. The low-valent mono-Cp zirconium compound CpZrMe(DMPE)2 (DMPE = l,2-bis(di-methylphosphino)ethane) catalyzes the dimerization of ethylene to 1-butene at low frequency (3 t.o./d), a process wherein the 1,3-butadiene complex 64 is presumed to be the catalyst (256). The clean dimerization of olefins using the Cp2ZrCl2/MAO (Al/Zr = 1) catalyst has recently been reported (257). Recently,... 

R.R. Schrock - Rapid Selective Dimerization of Ethylene to 1-Butene by a Tantalum Catalyst and a New Mechanism for Ethylene Oligomerization,/. Am. Chem. Soc. 101, 5099, 1979 S.J. McLain, J. Sancho, R.R. Schrock - Metallacyclopentane to Metallacyclobutane Ring Contraction, J. Am. Chem. Soc. 101,5451,1979 ... 

Depending on the solvent Ni(PPR3)2(ethylene) catalyzes the dimerization of ethylene to 1-butene (chlorobenzene) or to cyclobutane (toluene). It is the only case of cyclodimer formation from an unstrained olefin (R. H. Grubbs). 

Immobilization of ions on supports may be an elegant way to stabilize unusual oxidation states and/or coordination numbers. A particular system to mention here is the preparation of a well-defined Ni(l) complex coordinated to two surface oxygen atoms on silica, for the selective dimerization of ethylene to 1-butene. In this system it is possible to control the selectivity to 1-butene by coordination of two alkylphosphine ligands at a Ni(l) center which has been smoothly reduced from a Ni(II) precursor complex. 

Titanium alkoxide complexes in the presence of triethylaluminium as activator have been reported as selective catalyst systems for the dimer-isation of ethylene to 1-butene with a selectivity higher than 99% towards 1-butene. It was observed that the bulkier the substituent at the ortho position, the lower the catalytic activity of the complex compared to... 

Dimerization of ethylene to butene-1 has been developed recently by using a selective titanium-based catalyst. Butene-1 is finding new markets as a comonomer with ethylene in the manufacture of linear low-density polyethylene (LLDPE). 

Alphabutol Also called IFP-SABIC. A process for dimerizing ethylene to 1-butene. It operates under pressure at 80°C, using a complex Ziegler-Natta catalyst, a titanium alkoxide. Developed by the Institut Frangais du Petrole. First operated in Thailand in 1987. Seven plants had been licensed by 1993, of which three were operating. 

The simplest possible alkene oligomerization reaction, the dimerization of ethylene to butenes, is a well-studied reaction, and an industrial process was also developed for the selective formation of 1-butene42 (IFP Alphabutol process). 

The catalytic cycle of the Ni-catalysed dimerization of ethylene to give 1-butene (65) is explained by the insertion of ethylene to the nickel hydride 62 twice to form the ethyl complex 63 and the butyl complex 64. The elimination of /1-hydrogen gives 1-butene (65), and regenerates the Ni—H species 62. The reaction is chemoselective. Curiously, no further insertion of ethylene to 64 occurs. 

Mixtures of A1(C2H5)3 and Ti(0-iC3H7)4 will dimerize ethylene to 1-butene but they do not catalyze the isomerization of the 1-butene produced (129). Under the right set of conditions, only small amounts of polyethylene are produced with this latter mixture. On the other hand, solutions of compound 10 or 3 have been found to catalytically convert ethylene to ethane and butadiene (130). 

In 1953, Ziegler and Holzkamp (7) observed that the Aufbaureaktion (2) of triethylaluminum and ethylene [Eq. (1)] changed to a dimerization of ethylene to butene in the presence of traces of nickel salts [Eq. (2)]. This fundamental discovery, which has become known as the nickel effect, led to the development of Ziegler catalysts (3) and was the starting point for the organonickel chemistry of Wilke et al. (4, 5). 

Ziegler and coworkers at the Max Planck Institut fiir Kohlenforschung (Coal Research) in what was then Mulheim, West Germany were working to expand the scope and utility of the aufbau reaction. It was during this endeavor in 1953 that they accidentally discovered the "nickel effect." This term stemmed from the observation that nickel in combination with triethylaluminum catalyzes dimerization of ethylene to produce 1-butene. Accounts vary on the source of nickel in the formative experiments. It was ultimately attributed to trace nickel extracted from the surface of the stainless steel reactor in which early reactions were conducted. 

Catalyst Ratio CAl/Til. The molar ratio of aluminum alkyl to titanium alkoxide is recognized as an important parameter in the dimerization of ethylene to butene-1. A molar ratio less than 10 favors dimerization while a ratio higher than 10 favors polymerization [1]. An optimal catalyst activity was found to exist at Al/Ti range of (2- 4) (subject to the reaction temperature), where it was also noticed that there was no remarkable increase in the polymer formation. 

We have reviewed the processes for dimerization of ethylene to butene-1. IFP-SABIC Alphabutol process as yet remains the only commercially proven process. A plant based on this technology has been in operation since 1987. This plant has achieved targeted capacity of 50,000 metric tons/year and has met design requirements. 

The catalyst solution contains 30 to 50 mg/1 of palladium ions. A higher concentration would favor the dimerization of ethylene to butenes. The copper ion content is 3 to 6 g/L The presence of chlorine ions is necessary to maintain catalyst activity, but it leads to the formation of chlorinated by-products. The remaining by-products are mainly oxalic add, which yields copper oxalate, esters (acetate), formic add and carbon dioxide. 

The Ta"" complex, formulated as Ta(C2H4)2(Bu)(PMe3)2 (except R = Cl, Me), catalytically dimerizes ethylene to 1-butene, confirming the tendency of these complexes to undergo 8-hydrogen transfer. 

Al-Sa doun, A. (1993) Dimerization of ethylene to butene-1 catalyzed by Ti(OR )4—A1R3. Applied Catalysis A General, 105,1-40. 

It is claimed that very high yields of pure 1-butene are obtained at low conversions of ethylene [23-26]. Thus it is possible to dimerize ethylene to 1-butene to a 10% extent and use the resulting mixture for the production of ethylene copolymers [25]. At higher conversions of ethylene (>20%), appreciable amounts of Q and Cg alkenes are produced along with 1-butene [27]. 

Interestingly, the analogous niobium system fails to dimerize ethylene to 1-butene because of its inability to form a metallacyclopentane complex. 

Rh(SnCl3)2014] immobilized on AV-17-8 anion-exchange resin is a highly active, stable, and selective catalyst for the dimerization of ethylene to cis- and trans-2-butene in acidic media [244], A mathematical model has been derived to describe the process in terms of the ethylene pressure, temperature, and reaction time. The optimum yield of butenes is 88%. A cis/trms ratio of 1 2.7 is obtained after 6 h at 75°C and 42 atm of ethylene. 

Grubbs, R. H., and Miyashita, A., Dimerization of ethylene to cyclobutene and 1-butene under the influence of tris(triphenylphosphine)tetramethylenenickel(ll), J. Amer. Chem. Soc., 100, 7416, 1978. 

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