Ruhrchemie/Rhone-Poulenc propene hydroformylation

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. 

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 For propene hydroformylation, they have been replaced by rhodium (Union Carbide, Mitsubishi, Ruhrchemie-Rhone Poulenc).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. 

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] ... 

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],... 

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. 

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,... 

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. 

Catalyst decomposition is, overall, receiving little attention in academic work on homogeneous catalysis, and only in recent years has research on decomposition and stabilization of organometallic catalysts started to expand (116), with emphasis on reactions of significant commercial interest such as hydroformylation (117), metathesis 118), crosscoupling, and polymerization 119). Ligand decomposition seems to be a key issue for industrial application, because it affects the total number of turnovers, TON. Phosphine decomposition is an unavoidable side reaction in metal-phosphine complex-catalyzed reactions and the main barrier for commercial application of homogeneous catalysts. There are a few exceptions to this statement for example, the rhodium tppts-catalyzed hydroformylation of propene, a process developed by Ruhrchemie-Rhone Poulenc (now Celanese). 

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 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],... 

The opposite of entry 2 is the phase combination of entry 5, a fully organic reaction in the presence of an aqueous phase which contains the catalyst. This type of reaction system is the most often used for the technical realization of aqueous-phase organometallic-catalyzed reactions, for instance in the oligomerization of ethylene using the SHOP process (cf. Section 7.1) or in the Ruhrchemie/Rhone-Poulenc process (cf. Section 6.1.1) of propene hydroformylation (see also Section 4.2.2). 

The most important process with the solvent water is the hydroformylation of propene to butyraldehydes, known as the Ruhrchemie/Rhone-Poulenc process. This reaction is catalyzed by a rhodium complex containing the water-soluble ligand triphenylphosphane trisulfonate (TPPTS). The aldehydes are formed with an annual capacity of approx. 3000001. 

The Ruhrchemie/Rhone-Poulenc [1] process for the hydroformylation of short-chain alkenes such as propene and butene (cf. Section 6.1.3.1) combines a facile catalyst recycling with high selectivity and sufficiently high conversion rates to provide a commercially viable large-scale manufacturing process for butyraldehyde [2] and valeraldehyde [3]. Higher alkenes (> C8) are not suited for the RCH/RP process as run in Oberhausen. 

The thermal instability of rhodium-based hydroformylation catalysts has already been overcome commercially in the Ruhrchemie/Rhone-Poulenc process for propene hydroformylation in which the sodium salt of a sulfonated triphe-nylphosphine ligand (TPPTS, la) is used to solubilize the catalyst in the aqueous phase. In this process, the second phase is toluene and the reaction is carried out as a batch process with rapid stirring to intimately mix the two immiscible phases. After reaction, the system is allowed to separate and the organic phase is simply decanted from the aqueous catalyst phase. Both water-soluble polymers and PAMAM dendrimers have been reported as supports for rhodium-catalyzed hydroformylation under aqueous biphase conditions, but reactivities and regioselec-tivities were only comparable to or worse than those obtained with the reference TPPTS ligand. The aqueous biphase approach has found limited application for the hydroformylation of longer-chain alkenes, because of their very low solubility in water leading to prohibitively slow reaction rates, but there have been a variety of approaches directed at the solution of this problem. 

The aqueous biphasic hydroformylation of propene, namely the Ruhrchemie/ Rhone Poulenc (RCH/RP) process, has been widely used to produce n-butanal and many attempts have been proposed to improve this catalytic system, such as a thermoregulated phase transfer (TRPT) Rh(I) complex catalyst [74]. Moreover, Bonnemann et al. [75] have proved the in situ formation of Rh colloids when such a catalyst was applied to the aqueous biphasic hydroformylation of 1-octene. 

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... 

The most important large-scale aqueous-organic biphasic process is the hydroformylation of propene into butanal (Scheme 14) catalyzed by [HRh(CO)-(TPPTSlsl, that is the Ruhrchemie-Rhone Poulenc process (63,139,140). The catalyst is dissolved in water, whereas the substrate and product(s) comprise the organic phase. In the heart of this technology is a continuously stirred tank reactor connected to a phase separator. Complete insolubility of the rhodium-phosphine catalyst in the organic phase together with the lack of surfactant behavior of TPPTS assures a full recovery of rhodium by perfect phase separation. The catalytic reaction takes place at 120°C and 5 MPa (CO H2 = 1.01 1)—such conditions are milder than those of the so-called low pressure oxo processes. Propene reacts... 

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