Hydroformylation propene

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 For propene hydroformylation, they have been replaced by rhodium (Union Carbide, Mitsubishi, Ruhrchemie-Rhone Poulenc).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

Equation 2.7. Formation of a poisoning phosphite during propene hydroformylation... 

It was recognized during the development of propene hydroformylation that propene provided some stabilization for the catalyst. In the absence of the alkene, but in the presence of carbon monoxide and hydrogen, the catalyst can undergo what has been termed intrinsic deactivation. [3 3] Apparently after oxidative addition of triphenyl-phosphine to rhodium, diphenylphosphido bridged rhodium complexes are formed. 

Figure 7.11. Set-up for the continuous, Rh-catalysed propene hydroformylation using an impregnated SILP-catalyst...

A wide variety of new approaches to the problem of product separation in homogeneous catalysis has been discussed in the preceding chapters. Few of the new approaches has so far been commercialised, with the exceptions of a the use of aqueous biphasic systems for propene hydroformylation (Chapter 5) and the use of a phosphonium based ionic liquid for the Lewis acid catalysed isomerisation of butadiene monoxide to dihydrofuran (see Equation 9.1). This process has been operated by Eastman for the last 8 years without any loss or replenishment of ionic liquid [1], It has the advantage that the product is sufficiently volatile to be distilled from the reactor at the reaction temperature so the process can be run continuously with built in product catalyst separation. Production of lower volatility products by such a process would be more problematic. A side reaction leads to the conversion of butadiene oxide to high molecular weight oligomers. The ionic liquid has been designed to facilitate their separation from the catalyst (see Section 9.7)... 

By adding up to 36% ethylene glycol to the aqueous catalyst phase, the space-time yield could be boosted up to approx. 3 mt m-3 h-1 for propene hydroformylation, a factor of 20 in comparison to the conventional two-phase process without changing the reaction conditions. Because of this surprising speed-up, higher alpha-olefins up to 1-octene are converted with high to acceptable space-time yield (Fig. 22). Up to date this process is not commercialized, but has been tested in a continuous pilot plant. 

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 fourth generation process for large-scale application still has to be selected from the potential processes that have been nominated . In the chapters to follow several of these candidates will be discussed. The fourth generation will concern higher alkenes only, since for propene hydroformylation there are hardly wishes left [13], Many new phosphite-based catalysts have been reported that will convert internal alkenes to terminal products [6,7,14] and recently also new diphosphines have been reported that will do this [15,16,17],... 

LPO process. Propene hydroformylation can be done with a rhodium triphenylphosphine catalyst giving a linearity ranging from 60 to 96 % depending on the phosphine concentration. At very high phosphine concentration the rate is low, but the linearity achieves its maximum value. The commercial process (Union Carbide Corporation, now Dow Chemicals) operates presumably around 30 bar, at 120 °C, at high triphenylphosphine concentrations, and linearities around 92%. The estimated turnover frequency is in the order of only 300 mol(product).mol 1 (Rh).h Low ligand... 

Abstract The principle of catalytic SILP materials involves surface modification of a porous solid material by an ionic liquid coating. Ionic liquids are salts with melting points below 100 °C, generally characterized by extremely low volatilities. In the examples described in this paper, the ionic liquid coating contains a homogeneously dissolved Rh-complex and constitutes a uniform, thin film, which itself displays the catalytic reactivity in the system. Continuous fixed-bed reactor technology has been applied successfully to demonstrate the feasibility of catalytic SILP materials for propene hydroformylation and methanol carbonylation. 

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... 

A water-soluble diphosphine ligand with large bite angle was prepared by controlled sulfonation of XANTHPHOS. The rhodium complex of the resulting (2,7-bis(S03Na)-XANTHPHOS (51) showed a catalytic activity in propene hydroformylation comparable to Rh/TPPTS (TOF 310 vs 500 h" at 120 °C, 9 bar propene and 10 bar CO/H2 = 1/1) [70]. The regioselectivity... 

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. 

Table 8 Comparison of various industrial propene hydroformylation processes... 

In 1995, nearly 80% of all oxo products and over 90% of the propene hydroformylation products were produced using rhodium-based catalysts.48... 

These assembly ligands will be tested in suitable catalytic reactions that leave the assemblies intact. Salt-forming reactions are not attractive as the salts might interact with the assembly, nor is the use of catalytic metals that compete with the assembly metal for the salen type positions in the ditopic ligand ideally, all potential problems can be avoided if the same metal could be used. Rhodium-catalyzed hydroformylation of 1-octene is a suitable reaction, with the only disadvantage that high pressures are needed, but hydrogen or CO do not interfere with our assemblies. Metal salts do not interfere with the rhodium hydrides involved in the hydroformylation catalysis, as for instance the most effective industrial process today for propene hydroformylation... 

A major improvement in both catalytic activity and selectivity of propene hydroformylation in the organic-aqueous biphasic system was achieved by using the newly synthesized BINAS-Na ligand 10 in combination with rhodium(III) acetate (65). 

Another, similar propene hydroformylation process with rhodium and monosulfonated triphenylphosphane (tppms) was reported recently by Union Carbide (139). Capacity data are not available. 

The only substrate which has been hydroformylated using chiral cobalt catalysts with an optical yield comparable to those obtained with other metals is styrene (Table 1) in fact, in this case, optical yields up to 15% were obtained working in the presence of ethyl orthoformate15) to avoid racemization of 2-phenylpropanal. The changes in the prevailing absolute configuration of the synthesized aldehyde observed both in the styrene and 2-phenyl-1-propene hydroformylation upon... 

Fig. 15. Effect of the size of precursor ZnO-supported Rh carbonyl clusters on the activities and selectivities toward n-CjHsCHO in propene hydroformylation at 120°C. The following precursors were used RhCpICO), RhjCpjfCOlj, Rh4(CO),2, Rh (CO),, [NBu4]2[Rh,(CO) j], and [NBu4]2[Rh,3(CO)24H,]. The ZnO-supported Rh carbonyl clusters were oxidized to remove CO, followed by reduction at 200°C. The conventional Rh metal catalyst ( Rh ) was prepared from RhCl3-ZnO by reduction at 200°C.

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