Oligomerization biphasic process

Figure 2.5 (a) Scheme of the SHOP process (b) flow-sheet of the oligomerization biphasic process. Source adapted from Hagen [60],... 

The first biphasic process which has been commercialized uses Ziegler s Aufbaureaktion ("growing reaction") of ethene yielding oligomeric alkenes (Equation 5.7, [65]). 

Biphasic catalysis is not a new concept for oligomerization chemistry. On the contrary, the oligomerization of ethylene was the first commercialized example of a biphasic, catalytic reaction. The process is known under the name Shell Higher Olefins Process (SHOP) , and the first patents originate from as early as the late 1%0 s. 

Probably the first example of a process employing the biphasic concept is the Shell process for ethylene oligomerization in which the nickel catalyst and the ethylene reactant are dissolved in 1,4-butanediol, while the product, a mixture of linear alpha olefins, is insoluble and separates as a second (upper) liquid phase (see Fig. 7.1). This is the first step in the Shell Higher Olefins Process (SHOP), the largest single feed application of homogeneous catalysis [7]. 

The oligomerization reaction is carried out in a polar solvent in which the nickel catalyst is dissolved but the nonpolar products, the a-olefins, are nearly insoluble. Preferred solvents are alkanediols, especially 1,4-butanediol. This was one of the first examples of a biphasic liquid/liquid system to be used in catalysis and is one of the key features of the process. The nickel catalyst is prepared in situ from a nickel salt, e.g., nickel chloride, and a chelating PnO ligand like o-diphenylphosphinobenzoic acid (Structure 1) by reduction with sodium boro-hydride [30, 39]. Suitable ligands are the general type of diorganophosphino acid derivatives (2). 

The other process based on Manassen/Joo s ideas of liquid supports [19, 20] goes back to Keim s developments of organic-organic biphase systems for the Ni-catalyzed conversion of olefins to medium- and long-chain alpha- and internal olefins [38] by a combination of various process steps, among them oligomerization, metathesis, and isomerization. This is described in Chapter 3. 

Using such a catalytic system implies identifying a solvent that can achieve selective catalyst solubilization, with no impact on its activity. Two of these solvents are now used in industrial liquid-liquid biphasic catalytic processes butane-1,4-diol in Shell s SHOP oligomerization process and water in Ruhrchemie/Rhone-Poulenc s olefin hydroformylation process. 

These unusual properties were the basis of the fluorous biphasic catalysis process (FBC) first published in 1994 by Horvdth and Rdbai and demonstrated using hydroformylation chemistry as a pertinent example (7, 2) in a 1991 Ph.D. thesis, that was unfortunately not readily available to the homogeneous catalysis community nor published in the open literature, M. Vogt, under the guidance of his Ph.D. advisor, W. Keim, of the Rheinisch-WestflUischen Technischen Hochschule in Aachen, Germany, presented the first conceptual aspects of the FBC approach with an emphasis on oligomerization of alkenes, oxidation of alkenes, hydroformylation of olefins, and telomerization of dienes (5, 4). 

Chauvin Y, De Souza R, Olivier H (1998) Catalytic composition for biphase catalysis, in particular using nickel complexes, and a process for the oligomerization of olefins. US patent 5723712... 

Olivier-Bourbigou Lecocq, 2003) Chloroaluminate ILs and Ni(COD)(2) with a Bronsted acid ILs Biphasic ethylene oligomerization or butene and higher olefins dimerization (Difasol process). These solvents stabilize and activate nickel catalysts, even without ligand, and greatly enhance the reaction activity. The presence of a diimine ligand allows the production of C4-C6 linear olefins with improved alpha-selectivities. 

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