Ruhrchemie hydroformylation process

As described in the introductory chapter, biphasic catalysis has been around for a long time, but despite a few notable successes such as the Shell Higher Olefin Process (SHOP) and the Rhone-Poulenc-Ruhrchemie hydroformylation process, very few biphasic processes have made it into the industrial arena. The limitations of the solvents used so far in biphasic (or multiphasic) catalysis appear to be overcome by ionic liquids, and even if the perfect ionic liquid is not yet available, then there seems to be almost no limit to the number of new ionic liquids that can be made. It has been estimated that up to 1018 different ionic liquids may exist[1 2] and with such a vast number to choose from it is essential that understanding increases in order to allow accurate predictions of their properties and functions, opening up the possibility of designer solvents. 

The simultaneous process shown in Figure 1 (a) can be divided into two sequential units, shown in Figure 1 (b), as realized in the Rhone-Poulenc/Ruhrchemie hydroformylation process of propene. The reaction takes place in a continuous stirred tank reactor (CSTR) while the phase separation is carried out in a decanter. 

Aqueous two-phase hydrogenation may be a method of choice for synthetic purposes when no incompatibility problems between water and the substrates, products, or catalyst arise. It has already been proven by the success of the Ruhrchemie-Rhone-Poulenc hydroformylation process, that the catalyst can be retained in the aqueous phase with very high efficiency, and that aqueous-organic biphasic processes using organometallic catalysts are suitable for indus-... 

A few years later, Ruhrchemie joined forces with Rhone-Poulenc to develop a continuous biphasic hydroformylation process since Rhone-Poulenc had no... 

Shell higher olefin process (organic/organic) and the Ruhrchemie-Rhone Poulenc propene hydroformylation process (aqueous/organic). The diversity of the applications may confuse the newcomer but it is not easy to comprehend even by the more experienced. A guide to this field may help a lot, and this is why the book of Adams, Dyson and Tavener is most welcome. 

A very elegant solution to solve this problem is the introduction of either a permanent or a temporary phase boundary between the molecular catalyst and the product phase. The basic principle of multiphase catalysis has already found implementation on an industrial scale in the Shell higher olefin process (SHOP) and the Ruhrchemie/Rhdne-Poulenc propene hydroformylation process. Over the years, the idea of phase-separable catalysis has inspired many chemists to design new families of ligands and to develop new separation... 

An important development in the past 15 years in hydroformylation technology was the introduction of biphasic homogeneous catalysis. Kuntz (62) expressed the basic idea of a new generation of water-soluble oxo catalysts with triphenylphosphane trisulfonate (tppts as the sodium salt) as a ligand for a rhodium-complex-catalyzed hydroformylation process. Ruhrchemie AG adapted the idea on the basis of research done at Rhone-Poulenc and developed it into an industrially viable process, which was... 

The discovery of the oxo (or more accurately, hydroformylation) process was by Ruhrchemie s Roelen who applied for a German patent in 1938. This turned out to be a breakthrough method for both higher and lower alcohols production from the aldehydes. Exploitation of the process, however, was delayed by World War II. It was not until 19 8 that commercialization occurred with the manufacture of isooctyl alcohol by Enjay Chemical Company (1 ). 

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. 

Table 10.1 Summary of environmental benefits of the aqueous biphasic Ruhrchemie-Rhone-Poulenc hydroformylation process. ...

The first generation of hydroformylation processes (e.g., by BASF, ICI, Kuhlmann, Ruhrchemie) was exclusively based on cobalt as catalyst metal. As a consequence of the well-known stability diagram for cobalt carbonyl hydrides, the reaction conditions had to be rather harsh the pressure ranged between 20 and 35 MPa to avoid decomposition of the catalyst and deposition of metallic cobalt, and the temperature was adjusted according to the pressure and the concentration of the catalyst between 150 and 180 °C to ensure an acceptable rate of reaction. As the reaction conditions were quite similar, the processes differed only in the solution of the problem of how to separate product and catalyst, in order to recover and to recycle the catalyst [4]. Various modes were developed they largely yielded comparable results, and enabled hydroformylation processes to grow rapidly in capacity and importance (see Section 2.1.1.4.3). 

Figure 2.3 Ruhrchemie/Rhone-Poulenc hydroformylation process. Source adapted from Sheldon et a . [2].

Hydroformylation is one of the mildest and most efficient methods of producing aldehydes and hence it has a wide range of applications in the petrochemical industry. The cleanest, industrially important hydroformylation process is the aqueous biphasic system developed by Ruhrchemie/Rhone-Poulenc [63]. However, the applicability of this system is limited to substrates which have a low solubility in water, such as propene and 1-butene. It is advantageous to use scC02 because there is no gas-liquid phase boundary and because of the ability of scC02 to dissolve gases in high concentrations, combined with effective product and catalyst separation [64]. 

The Ruhrchemie/Rhone-Poulenc oxo process has been reviewed repeatedly (cf. Section 6.1 and [2, 3, 6]). This two-phase hydroformylation process using catalysts dissolved in water, and also the scientific work on this subject untertaken by universities, have resulted in hundreds of publications and patents [7] and extensive experience with the first large-scale implementation. 

Hydroformylation is a very important industrial process. Olefins are converted to aldehydes, which can be further transformed into acids, alcohols or amines. The Ruhrchemie/Rhone-Poulenc hydroformylation process is an aqueous-organic biphasic process which uses an easily separable water-soluble rhodium... 

In total, RCH/RP s process - although neither company still exists Ruhrchemie went its way through Hoechat AG and Celanese to the present owner Blackstone and the j oint venture European Oxo Rhone-Poulenc became a part of the late Aventis SA and now Sanofi - is still the only oxo version of the fifth-generation hydroformylation processes. 

For the different hydroformylation processes described above, the catalyst separation and recycling remain a constant preoccupation. This point is particularly crucial when a very expensive metal is used as catalyst (rhodium). The recycling is either operated by chemical transformation or by direct distillation, depending on the catalyst and its stability. In that way, the development of the aqueous biphasic process can be considered as an important breakthrough (4-6). The separation is operated by decantation, which simplifies the process scheme and limits the risks of catalyst decomposition during distillation. Even if the 0x0 Ruhrchemie/Rhone-Poulenc process presents undeniable advantages, this process remains limited to short-chain olefins (C2-C5) because of the low solubility of higher olefins in water which renders the reaction rates too low for viable processes [7]. 

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. 

Tris-m-sulfonatophenylphosphine (tppts) plays an important role in the history of homogeneous catalysis [39], mainly due to its use in the Ruhrchemie/Rhone-Poulenc hydroformylation process [40], now operated by Celanese (see 1.2 and Chapter 7). It is also used in a number of fine chemical processes, such as selective hydrogenation with ruthenium [41], carbon-carbon bond formation with rhodium [42], and the Heck reaction [43]. Monosidfonated triphenylphosphine (tppms) is used for the preparation ofnonadienol [44] (see Figure 5). 

Biphasic techniques for recovery and recycle are among the recent improvements of homogeneous catalysis, and they are the only developments that have been recently and successfully applied in the chemical industry. Among the hydroformylation processes they form a fourth generation of oxo processes.They are estabhshed as the Ruhrchemie/Rhone-Poulenc process (RCH/RP process), with aimual production rates of approximately 800,000 tons/year (tpy). 

Ruhrchemie and Rhone Poulenc introduced a two-phase modification to the basic propylene hydroformylation process in 1984. The aqueous phase contained the rhodium catalyst, and a phosphine derivative was circulated through the reactor with the propylene and synAesis gas. The specific phosphine used was triphenylphosphine in which the meta-position of the phenyl group had been substituted by the sodium salt of the sulphonic acid. The products formed an organic layer that was separated by decantation when the two immiscible liquid phases were removed from the reactor. The aqueous layer was returned to the reactor for further use. The catalyst is not affected by sulfur poisons, and can... 

Bach H, Gick W, Konkol W and Wiebus E 1988 The Ruhrchemie/Rhone-Poulenc (RHV/RP) process-latest variant of the fifty-year-old hydroformylation reaction Proc. 9th Int. Congr. on Catalysis vol 1, pp 254-9... 

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