Hydroformylation industrial operations

Quite new ideas for the reactor design of aqueous multiphase fluid/fluid reactions have been reported by researchers from Oxeno. In packed tubular reactors and under unconventional reaction conditions they observed very high space-time yields which increased the rate compared with conventional operation by a factor of 10 due to a combination of mass transfer area and kinetics [29]. Thus the old question of aqueous-biphase hydroformylation "Where does the reaction takes place " - i.e., at the interphase or the bulk of the liquid phase [23,56h] - is again questionable, at least under the conditions (packed tubular reactors, other hydrodynamic conditions, in mini plants, and in the unusual,and costly presence of ethylene glycol) and not in harsh industrial operation. The considerable reduction of the laminar boundary layer in highly loaded packed tubular reactors increases the mass transfer coefficients, thus Oxeno claim the successful hydroformylation of 1-octene [25a,26,29c,49a,49e,58d,58f], The search for a new reactor design may also include operation in microreactors [59]. 

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. 

The rate of hydroformylation increases with increasing hydrogen and decreases with increasing carbon monoxide partial pressures (9), suggesting that rates of hydroformylation would be satisfactory at high H2 and low CO partial pressures. In industrial practice, however, high pressures of both H2 and CO ate required in order to stabilize the HCo(CO)4 catalyst at the temperatures necessary for practical rates (10). Commercial processes, for example, operate at >24 MPa (3480 psi) and >140 C. 

Ligand-Modified Rhodium Process. The triphenylphosphine-modified rhodium oxo process, termed the LP Oxo process, is the industry standard for the hydroformylation of ethylene and propylene as of this writing (ca 1995). It employs a triphenylphosphine [603-35-0] (TPP) (1) modified rhodium catalyst. The process operates at low (0.7—3 MPa (100—450 psi)) pressures and low (80—120°C) temperatures. Suitable sources of rhodium are the alkanoate, 2,4-pentanedionate, or nitrate. A low (60—80 kPa (8.7—11.6 psi)) CO partial pressure and high (10—12%) TPP concentration are critical to obtaining a high (eg, 10 1) normal-to-branched aldehyde ratio. The process, first commercialized in 1976 by Union Carbide Corporation in Ponce, Puerto Rico, has been ficensed worldwide by Union Carbide Corporation and Davy Process Technology. 

The ionic liquid investment could be further reduced if future research enables the application of ammonium based alkylsulfate or arylsulfonate ionic liquids. For these systems bulk prices around 15 /kg are expected. Ammonium based alkylsulfate or arylsulfonate ionic liquids usually show melting points slightly above room temperature but clearly below the operating temperature of the hydroformylation reaction. Therefore these systems may be less suitable for the liquid-liquid biphasic process in which the ionic liquid may be involved in process steps at ambient temperature (e.g. phase separation or liquid storage). In contrast, for the SILP catalyst a room temperature ionic liquid is not necessarily required as long as the film becomes a liquid under the reaction conditions. Assuming an ammonium based SILP catalyst, the capital investment for the ionic liquid for the industrial SILP catalyst would add up to 105,000 . 

For this reaction, the early investigations of Reppe pointed out the need for catalyst precursors to operate at high pressure [2], It is necessary to work at 150-300 bar of CO in order to stabilize the two catalytic species [Co(H)(CO)4] or [Ni(H)(X)(CO)2] that adopt a mechanism analogous to the cobalt-catalyzed hydroformylation [44,45]. Many industrial applications have been reported [28,46,47] for the synthesis of plasticizers and detergents. Similarly, the two-step methoxycarbonylation of 1,3-butadiene has been explored by BASF and other companies to produce dimethyl 1,6-hexanedioate (adipate) directly from the C4 cut [28,48]. The first step operates at 130 °C and... 

On the industrial level, aqueous two-phase systems are used more often than nonaqueous two-phase systems. The Kuraray Co. operates a pilot plant for the hydrodimerization of 1,3-butadiene in a two-phase system with a Pd/tppms catalyst (140). The reaction is carried out in sulfolane-water, from which the products, the octadienols, separate. The final products can be octanol or nonanediol made by subsequent isomerization and hydroformylation. The capacity of the Kuraray process is about 5000 tons/year. 

Union Carbide invented the industrial use of highly active ligand-modified rhodium complexes.90-93 [RhH(CO)(PPh3)3], the most widely used catalyst, operates under mild reaction conditions (90-120°C, 10-50 atm). This process, therefore, is also called low-pressure oxo process. Important features of the rhodium-catalyzed hydroformylation are the high selectivity to n-aldehydes (about 92%) and the formation of very low amounts of alcohols and alkanes. Purification of the reactants, however, is necessary because of low catalyst concentrations. 

The crucial problem associated with the use of homogeneous rhodium catalysts in industrial hydroformylation is catalyst recovery. Because of the high cost of rhodium, it is necessary to recover rhodium at the ppm level to ensure economical operation. A highly successful solution to this problem was the development and application of the aqueous biphasic catalysis concept. 

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... 

Industrial problems have, in some instances, been solved either by a proper choice of construction materials and suitable process design or by development of heterogeneous catalytic systems using supported complexes or by generating active complexes in situ on a support material which avoid some of the problems of liquid-phase operation. For example, a number of the problems in liquid-phase vinyl acetate processing have been overcome by development of supported Pd catalysts (106). Vapor-phase hydroformylation has been carried out on supported rhodium complexes (107). 

Surprisingly little information is available about the kinetics of hydroformylation reactions. For several decades Natta s equation served as a basic explanation however, in the last few years the application of reaction models of the Lang-muir-Hinshelwood type, even to biphasic systems, has been successfully demonstrated. This contribution (see Section 2.1.1) puts more emphasis on this area than has been usual in reviews on hydroformylation (see Section 2.1.1.3.2). In addition, the fundamentals of the oxo synthesis are discussed, along with the most important recent developments. The industrial processes in operation today are described as well. Due to its importance, the hydroformylation reaction has already been extensively reviewed elsewhere. For information beyond and in addition to this contribution, see [4, 7-12, 293]. 

These few examples may show that the hydroformylation mechanism is still under investigation, even after more than 50 years of successful operation in industrial plants. 

Catalyst performance has of course been a permanent theme in industry. For example, the catalytic activity of oxo catalysts (in hydroformylation) has improved in the past 50 years by a factor of 10 000 change from diadic and triadic process technology to continuous plant operation, replacement of cobalt by rhodium, tailoring of the ligand sphere (phosphines), change of phase application (from mono- to two-phase processes). At the same time, an improvement of selectivity has been achieved, apart from the ease of product/catalyst separation [132]. A similar development seems to occur in the Monsanto acetic acid process [49]. 

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