Ruhrchemie/Rhone-Poulenc hydroformylation

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-... 

Figure 4.24 a A general process schematic for aqueous biphasic catalysis, and examples ofwater-soluble phosphine ligands b the catalytic cycle for the Ruhrchemie/Rhone-Poulenc hydroformylation of propene. 

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

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

The technically most important biphasic process in the Ruhrchemie/Rhone-Poulenc hydroformylation of propene using the in situ Rh(I) catalyst HRh(CO)-(TPPTS)3 [6, 37]. Its formation from Rh(CO)2(acac) and TPPTS in a syngas atmosphere has been studied in detail [38, 39]. The BINAS-Na (ll)/Rh catalyst showed an outstanding performance in propene hydroformylation [15]. Binudear thiolato bridged rhodium complexes 12 have been used in 1-octene hydroformylation as precatalysts [41], For details of the hydroformylation, cf. Section 6.1 [15, 40, 41],... 

Ruhrchemie/ Rhone-Poulenc Hydroformylation of olefins (6.1) Rh Water [10-20]... 

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... 

The technically most important biphasic process in the Ruhrchemie/Rhone-Poulenc hydroformylation of propene uses the in-situ Rh(I) catalyst HRh(CO)-(TPPTS)3 Its formation from Rh(CO)2(acac) and TPPTS in a syngas... 

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). 

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... 

An example of a large scale application of the aqueous biphasic concept is the Ruhrchemie/Rhone-Poulenc process for the hydroformylation of propylene to n-butanal (Eqn. (15)), which employs a water-soluble rhodium(I) complex of trisulphonated triphenylphosphine (tppts) as the catalyst (Cornils and Wiebus, 1996). 

Cobalt carbonyls are the oldest catalysts for hydroformylation and they have been used in industry for many years. They are used either as unmodified carbonyls, or modified with alkylphosphines (Shell process). For propene hydroformylation, they have been replaced by rhodium (Union Carbide, Mitsubishi, Ruhrchemie-Rhone Poulenc). For higher alkenes, cobalt is still the catalyst of choice. Internal alkenes can be used as the substrate as cobalt has a propensity for causing isomerization under a pressure of CO and high preference for the formation of linear aldehydes. Recently a new process was introduced for the hydroformylation of ethene oxide using a cobalt catalyst modified with a diphosphine. In the following we will focus on relevant complexes that have been identified and recently reported reactions of interest. 

Biphasic techniques for recovery and recycle are among the recent improvements of homogeneous catalysis - and they are the only developments which have been recently and successfully applied in the chemical industry. They are specially introduced into the hydroformylation (or "oxo") reaction, where they form a fourth generation of oxo processes (Figure 5.1 [1]). They are established as the "Ruhrchemie/Rhone-Poulenc process" (RCH/RP) [2] cf. also Section 5.2.4.1), with annual production rates of approximately 800,000 tonnes y"1 (tpy). 

The hydroformylation reaction is highly exothermic, which makes temperature control and the use of the reaction heat potentially productive and profitable (e.g, steam generation). The standard installation of Ruhrchemie/Rhone-Poulenc s aqueous-phase processes is heat recovery by heat exchangers done in a way that the reboiler of the distillation column for work-up of the oxo products is a falling film evaporator... 

The synthesis of aldehydes via hydroformylation of alkenes is an important industrial process used to produce in the region of 6 million tonnes a year of aldehydes. These compounds are used as intermediates in the manufacture of plasticizers, soaps, detergents and pharmaceutical products [7], While the majority of aldehydes prepared from alkene hydroformylation are done so in organic solvents, some research in 1975 showed that rhodium complexes with sulfonated phosphine ligands immobilized in water were able to hydroformylate propene with virtually complete retention of rhodium in the aqueous phase [8], Since catalyst loss is a major problem in the production of bulk chemicals of this nature, the process was scaled up, culminating in the Ruhrchemie-Rhone-Poulenc process for hydroformylation of propene, initially on a 120000 tonne per year scale [9], The development of this biphasic process represents one of the major transitions since the discovery of the hydroformylation reaction. The key transitions in this field include [10] ... 

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. 

In Chapter 8 we will discuss the hydroformylation of propene using rhodium catalysts. Rhodium is most suited for the hydroformylation of terminal alkenes, as we shall discuss later. In older plants cobalt is still used for the hydroformylation of propene, but the most economic route for propene hydroformylation is the Ruhrchemie/Rhone-Poulenc process using two-phase catalysis with rhodium catalysts. For higher alkenes, cobalt is still the preferred catalyst, although recently major improvements on rhodium (see Chapter 8) and palladium catalysts have been reported [3],... 

The third generation process concerns the Ruhrchemie/Rhone-Poulenc process utilizing a two-phase system containing water-soluble rhodium-tppts in one phase and the product butanal in the organic phase. The process has been in operation since 1984 by Ruhrchemie (or Celanese, nowadays). The system will be discussed in section 8.2.5. Since 1995 this process is also used for the hydroformylation of 1-butene. 

Rhodium-catalyzed biphasic hydroformylation of olefins. The Ruhrchemie-Rhone Poulenc process for manufacturing... 

In 1975 Kuntz has described that the complexes formed from various rhodium-containing precursors and the sulfonated phosphines, TPPDS (2) or TPPTS (3) were active catalysts of hydroformylafion of propene and 1-hexene [15,33] in aqueous/organic biphasic systems with virtually complete retention of rhodium in the aqueous phase. The development of this fundamental discovery into a large scale industrial operation, known these days as the Ruhrchemie-Rhone Poulenc (RCH-RP) process for hydroformylation of propene, demanded intensive research efforts [21,28]. Tire final result of these is characterized by the data in Table 4.2 in comparison with cobalt- or rhodium-catalyzed processes taking place in homogeneous organic phases. 

As mentioned earlier, in the Ruhrchemie-Rhone Poulenc process for propene hydroformylation the pH of the aqueous phase is kept between 5 and 6. This seems to be an optimum in order to avoid acid- and base-catalyzed side reactions of aldehydes and degradation of TPPTS. Nevertheless, it has been observed in this [93] and in many other cases [38,94-96,104,128,131] that the [RhH(CO)(P)3] (P = water-soluble phosphine) catalysts work more actively at higher pH. This is unusual for a reaction in which (seemingly) no charged species are involved. For example, in 1-octene hydroformylation with [ RhCl(COD) 2] + TPPTS catalyst in a biphasic medium the rates increased by two- to five-fold when the pH was changed from 7 to 10 [93,96]. In the same detailed kinetic studies [93,96] it was also established that the rate of 1-octene hydroformylation was a significantly different function of reaction parameters such as catalyst concentration, CO and hydrogen pressure at pH 7 than at pH 10. 

The Ruhrchemie/Rhone-Poulenc process is performed annually on a 600,000 metric ton scale (18). In this process, propylene is hydroformylated to form butyraldehyde. While the solubility of propylene in water (200 ppm) is sufficient for catalysis, the technique cannot be extended to longer-chain olefins, such as 1-octene (<3 ppm solubility) (20). Since the reaction occurs in the aqueous phase (21), the hydrophobicity of the substrate is a paramount concern. We overcame these limitations via the addition of a polar organic co-solvent coupled with subsequent phase splitting induced by dissolution of gaseous CO2. This creates the opportunity to run homogeneous reactions with extremely hydrophobic substrates in an organic/aqueous mixture with a water-soluble catalyst. After C02-induced phase separation, the catalyst-rich aqueous phase and the product-rich organic phase can be easily decanted and the aqueous catalyst recycled. 

A breakthrough in the hydroformylation of propene was achieved following the synthesis of the water soluble ligand tppts for the preparation of the RhH(CO)(tppts)3 catalyst345 which formed the basis for the development of the Ruhrchemie/Rhone-Poulenc two phase process. This process operates under mild reaction conditions giving excellent n/i ratios and easy separation of products from the catalyst by decantation with virtually no catalyst leaching. 

Hydroformylation of Propene the Ruhrchemie/Rhone-Poulenc (RCH/RP) Process - The industrial process for the hydroformylation of propene in a two phase system was developed by Ruhrchemie AG after a period of successful scale up tests in pilot plants.31 34 35-38-42 48 50 52-57 61 64-6 70-7 74,132-134,224,307.322,323,... 

The prototype industrial process based on this concept is the Ruhrchemie-Rhone Poulenc process for the hydroformylation of propylene to butanal94,219,220 (see Section 7.3.1). Because of the use of appropriately modified water-soluble ligands, the catalyst resides and operates in the aqueous phase. The particular features of this process are the positive energy balance and easy catalyst recovery, namely, the simply circulation of the aqueous catalyst solution. New types of water-soluble Ir and Rh complexes with tris(hydroxymethyl)phosphine222 were described, and the biphasic hydroformylation of 1-hexene was accomplished in ionic liquids.223 A cationic sugar-substituted Rh complex displays high regioselectivity to branched aldehydes.224... 

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. 

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