Hydroformylation current catalyst

Three commercial homogeneous catalytic processes for the hydroformyla-tion reaction deserve a comparative study. Two of these involve the use of cobalt complexes as catalysts. In the old process a cobalt salt was used. In the modihed current version, a cobalt salt plus a tertiary phosphine are used as the catalyst precursors. The third process uses a rhodium salt with a tertiary phosphine as the catalyst precursor. Ruhrchemie/Rhone-Poulenc, Mitsubishi-Kasei, Union Carbide, and Celanese use the rhodium-based hydroformylation process. The phosphine-modihed cobalt-based system was developed by Shell specih-cally for linear alcohol synthesis (see Section 7.4.1). The old unmodihed cobalt process is of interest mainly for comparison. Some of the process parameters are compared in Table 5.1. 

The first step in the synthesis of nonvolatile plasticizers - which are of increasing importance - is hydroformylation of a long-chain olefin, for which rhodium phosphite catalysts have very useful properties. The current use of sterically hindered phosphites as antioxidants for polyalkenes together with their much simpler... 

Industrial hydroformylation is currently performed in two basic variants the homogeneous processes, where the catalyst and substrate are in the same liquid phase (Shell, UCC, BASF, etc.), and the two-phase process with a water-soluble catalyst (RCH/RP). These processes will be discussed in detail in Section 2.1.1.4. Gas-phase hydroformylation with heterogeneous catalysts plays no role today. The immobilization of homogeneous catalysts will be discussed in Section 3.1.1. Special applications such as SLPC (supported /iquid-phase catalysts) [43] and SAPC (supported aqueous-/7hase catalysts) [44] are not considered further here. Heterogeneous oxo catalysts are not within the scope of this book they are discussed further elsewhere [267]. 

Likewise, a thermoregulated phase transfer process within the aqueous/organic two-phase system has been reported by Jin and co-workers (cf. Section 3.1.1.1) [290]. A water-soluble supramolecular Rh catalyst based on functionalized /1-cyclodextrin was also described [291]. In a two-phase system this catalyst may function as a carrier for the transfer of both the starting material and the product between the different phases. As an alternative to polar media for biphasic hydroformylation, Chauvin et al., used ionic liquids based on imidazolium salts which are well known for dimerization reactions (cf. Sections 2.3.1.4 and 3.1.1.2.2) [270, 271, 292]. For introduction into technical processes the currently availability and price of ionic liquids could be a drawback, especially for bulk chemicals such as 0x0 products. 

Double-bond isomerization has been exploited as a desired reaction in organic synthesis examples include the synthesis of steroids. It is also an undesired side reaction of industrially relevant reactions such as hydroformylation (cf. Section 2.1.1), hydrogenation (cf. Section 2.2), and hydrosilyation (cf. Section 2.6), it is a subject of current interest [34—36]. Two promising developments are worth mentioning here because they yielded highly selective catalysts which are, at the same time, easy to handle. 

Roughly at the same time (in contradiction to a misleading publication by Papado-gianakis [2]) and parallel to work done by Joo [3] and others [4], one of us (EK, then at Rhone-Poulenc) devoted time and effort to starting practical work on biphasic catalysis with organometallic catalysts (especially hydroformylation), developing the biphasic principle and the current well-known standard ligand triphenyl-phosphine trisulfonate (TPPTS, cf. Section 3.2.1). 

Other Systems. - The commercial application of Rh hydroformylation catalysts is currently limited to alkenes of relatively low molecular weights where the product can be removed by distillation. Similar constraints apply to SLPC systems and for chemically immobilized systems low activites can be expected for high molecular weight alkenes because of problems connected with reactant diffusion. A number of publications have appeared over the past five years which address this problem. 

---