1-octene selectivity

McGuiness, D., Rucklidge, A., Tooze, R. and Slawin, A. (2007) Cocatalyst influence in selective oligomerization effect on activity, catalyst stability, and 1-hexene/1-octene selectivity in the ethylene trimerization and tetramerization reaction. Organometallics, 26, 2561-2569. 

Table 2. Compared selectivity for 1-octene self-metathesis Solvent Conversion of 1-octene Selectivity toward 7-tetradecene...

Dimersol X A process for dimerizing mixed butenes to mixed octenes. Selective hydrogenation, catalyzed by a soluble Ziegler catalyst, is used. The spent catalyst is discarded. The process was developed by IFP and first operated at Kashima, Japan, in 1980. BASF has used the process in Ludwigshafen since 1985. 

Cyclic carbonate [wt.%] Extraction agent [wt.%] NOP [wt.%] Conversion of trans-4-octene [%] Selectivity to M-nonanal [%] Rh leaching [%] P leaching [%]... 

After 48 hours a conversion of 63 was obtained with an octene selectivity of 97.3. At low conversions, the octene selectivity was 99.8. ... 

This is illlustrated in the Figure. A conversion of 93 with an octene selectivity of 91.0 was observed after 25 hours. 

The butene conversion level is highly dependent on its initial concentration. For instance, today commercial Dimersol-X technology achieves 80% conversion of butenes with up to 85% octene selectivity. A process flow diagram is depicted in Figure 1. The reaction takes place at low temperature (40-60 °C) in three or four consecutive well-mixed reactors. The pressure of 1.5 MPa is sufficient to maintain all reactants and products in the liquid state. Mixing and heat removal are ensured by an external recirculation loop over a heat exchanger system. The two components of the catalytic system are injected separately into this reaction loop under precise flow control. The residence time is between 5 and 10 h. 

In the Difasol technology, the catalyst is dissolved in IL reaction products are poorly soluble. The reactants miscibility remains adequate to ensure reaction. Batch laboratory experiments on butene dimerization demonstrated that no reaction occurs in the organic phase. This indicates that the reaction takes place at the interface or in the ionic liquid phase. Experiments also proved that rising the mixing efficiency increases the reaction rate but does not change the octene selectivity. So excellent mixing is necessary to ensure good conversion by rapid mass transfer and efficient interaction of the ionic catalyst with the substrate. 

A continuous test-run engaging an industrially representative rafEnate-2 feed (70% n-butenes, 2% isobutene, and 25% butanes) was then conducted. A productivity of 30 kg butenes converted/g Ni and 12 kg butenes converted/g IL was easily maintained over a period of 5500 h. During the whole test, butene conversion and octene selectivity were steady. The Difasol system achieved more than 70% butene conversion with 95% octene selectivity. This is five selectivity points higher than the classical Dimersol system. Moreover, unlike what is observed with Dimersol, octene selectivity remained higher than 90%, even at 80% butene conversion, which was easily obtained by increasing the catalyst concentration. 

Both butene conversion and octene selectivity are clearly improved using Dimersol + Difasol arrangement, while Standalone Difasol appears to be able to achieve the best octene selectivity with the lowest butene conversions. 

In fact this last remark results from the constraint on iso-Capex per ton of octenes. Of course, Standalone Difasol can achieve higher butene conversion (more than 85% is feasible), still with 91% octene selectivity. 

As early as 1972 Parshall described the platinum-catalyzed hydroformylation of ethene in tetraethylammonium trichlorostannate melts [1]. [NEt4][SnCl3], the ionic liquid used for these investigations, has a melting point of 78 °C. Recently, platinum-catalyzed hydroformylation in the room-temperature chlorostannate ionic liquid [BMIM]Cl/SnCl2 was studied in the author s group. The hydroformylation of 1-octene was carried out with remarkable n/iso selectivities (Scheme 5.2-13) [66]. 

After ten consecutive runs the overall turnover number reaches up to 3500 mol 1-octene converted per mol Rh-catalyst. In agreement with these recycling experiments, no Rh could be detected in the product layer by AAS or ICP, indicating leaching of less then 0.07 %. In all experiments, very good selectivities for the linear aldehyde were obtained, thus proving that the attachment of the guanidinium moiety onto the xanthene backbone had not influenced its known positive effect on... 

The selective, Ni-catalyzed, biphasic dimerization of 1-butene to linear octenes has been studied in the author s group. A catalytic system well loiown for its ability to form linear dimers from 1-butene in conventional organic solvents - namely the square-planar Ni-complex (q-4-cycloocten-l-yl](l,l,l,5,5,5,-hexafluoro-2,4-pen-tanedionato-0,0 )nickel [(H-COD)Ni(hfacac)] [103] - was therefore used in chloroaluminate ionic liquids. 

For this specific task, ionic liquids containing allcylaluminiums proved unsuitable, due to their strong isomerization activity [102]. Since, mechanistically, only the linkage of two 1-butene molecules can give rise to the formation of linear octenes, isomerization activity in the solvent inhibits the formation of the desired product. Therefore, slightly acidic chloroaluminate melts that would enable selective nickel catalysis without the addition of alkylaluminiums were developed [104]. It was found that an acidic chloroaluminate ionic liquid buffered with small amounts of weak organic bases provided a solvent that allowed a selective, biphasic reaction with [(H-COD)Ni(hfacac)]. 

The Institut Fran ais du Petrole has developed and commercialized a process, named Dimersol X, based on a homogeneous catalyst, which selectively produces dimers from butenes. The low-branching octenes produced are good starting materials for isononanol production. This process is catalyzed by a system based on a nickel(II) salt, soluble in a paraffinic hydrocarbon, activated with an alkylalumini-um chloride derivative directly inside the dimerization reactor. The reaction is sec-... 

This arrangement ensures more efficient overall catalyst utilization and a significant increase in the yield of octenes. As an example, dimer selectivity in the 90-92 % range with butene conversion in the 80-85 % range can be obtained with a C4 feed containing 60 % butenes. Thanks to the biphasic technique, the dimerization... 

A similar catalytic dimerization system has been investigated [40] in a continuous flow loop reactor in order to study the stability of the ionic liquid solution. The catalyst used is the organometallic nickel(II) complex (Hcod)Ni(hfacac) (Hcod = cyclooct-4-ene-l-yl and hfacac = l,l,l,5,5,5-hexafluoro-2,4-pentanedionato-0,0 ), and the ionic liquid is an acidic chloroaluminate based on the acidic mixture of 1-butyl-4-methylpyridinium chloride and aluminium chloride. No alkylaluminium is added, but an organic Lewis base is added to buffer the acidity of the medium. The ionic catalyst solution is introduced into the reactor loop at the beginning of the reaction and the loop is filled with the reactants (total volume 160 mL). The feed enters continuously into the loop and the products are continuously separated in a settler. The overall activity is 18,000 (TON). The selectivity to dimers is in the 98 % range and the selectivity to linear octenes is 52 %. 

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