Carbonylation Hoechst process

The carbonylation reaction in the Hoechst process involves the use of PdCl2(PPh3)2 as the precatalyst, a CO pressure of about 50 bar, and a temperature of about 130°C. It is performed in a mixture of an organic solvent and hydrochloric acid. The mechanism at a molecular level is not known with certainty. On the basis of the known chemistry of palladium, a speculative catalytic cycle is shown in Fig. 4.12. 

This development began to reduce steadily the capacities of acetaldehyde which previously had been made by oxidation of ethylene (Wacker-Hoechst process cf. Section 2.4.1) and converted to acetic acid (cf. Section 2.4.4). Moreover, the Monsanto process, the second-generation process for methanol carbonylation is now being followed by the third generation of highly efficient carbonylation processes, enabling acetic anhydride as well as acetic acid to be produced (cf Scheme 2 Tennessee-Eastman [36] and BP [37] processes). The most advanced process (Hoechst [40]) has so far not been implemented industrially because of neglects... 

On the other hand, process steps which are known in principle (and thus may be verified industrially in due course) but have not yet been applied are referred to as applied processes as well. Examples are special variants of hydroformylation or carbonylation for the manufacture of special chemicals, modifications of oxacyla-tions (in the context of the Wacker-Hoechst process), the copolymerization of ethylene with carbon monoxide (Shell), and several other processes. 

Carbonylation of isobutyl phenyl ethyl alcohol to ibuprofen (Boots-Hoechst process) Pd(PPh3)2Cl2 G-L-L/organic phase catalysis [14]... 

Economic studies by Aquilo et al of the Celanese Chemical Co. have shown that acetaldehyde production via reductive methanol carbonylation is superior to the Wacker—Hoechst process, if reinvestment is considered... 

Butane. Butane LPO has been a significant source for the commercial production of acetic acid and acetic anhydride for many years. At various times, plants have operated in the former USSR, Germany, Holland, the United States, and Canada. Only the Hoechst-Celanese Chemical Group, Inc. plants in Pampa, Texas, and Edmonton, Alberta, Canada, continue to operate. The Pampa plant, with a reported aimual production of 250,000 t/yr, represents about 15% of the 1994 installed U.S. capacity (212). Methanol carbonylation is now the dominant process for acetic acid production, but butane LPO in estabhshed plants remains competitive. 

Propane, 1-propanol, and heavy ends (the last are made by aldol condensation) are minor by-products of the hydroformylation step. A number of transition-metal carbonyls (qv), eg, Co, Fe, Ni, Rh, and Ir, have been used to cataly2e the oxo reaction, but cobalt and rhodium are the only economically practical choices. In the United States, Texas Eastman, Union Carbide, and Hoechst Celanese make 1-propanol by oxo technology (11). Texas Eastman, which had used conventional cobalt oxo technology with an HCo(CO)4 catalyst, switched to a phosphine-modified Rh catalyst ia 1989 (11) (see Oxo process). In Europe, 1-propanol is made by Hoechst AG and BASE AG (12). 

Similarly, Pd/tppts was used by Hoechst (Kohlpainter and Beller, 1997) as the catalyst in the synthesis of phenylacetic acid by biphasic carbonylation of benzyl chloride (Fig. 2.29). The new process replaces a classical synthesis by reaction of benzyl chloride with sodium cyanide, followed by hydrolysis of the resulting benzyl cyanide. Although the new process produces one equivalent of sodium chloride, this is substantially less salt production than in the original process. Moreover, sodium cyanide is about seven times as expensive per kg as carbon monoxide. 

Other companies (e.g., Hoechst) have developed a slightly different process in which the water content is low in order to save CO feedstock. In the absence of water it turned out that the catalyst precipitates. Clearly, at low water concentrations the reduction of rhodium(III) back to rhodium(I) is much slower, but the formation of the trivalent rhodium species is reduced in the first place, because the HI content decreases with the water concentration. The water content is kept low by adding part of the methanol in the form of methyl acetate. Indeed, the shift reaction is now suppressed. Stabilization of the rhodium species and lowering of the HI content can be achieved by the addition of iodide salts. High reaction rates and low catalyst usage can be achieved at low reactor water concentration by the introduction of tertiary phosphine oxide additives.8 The kinetics of the title reaction with respect to [MeOH] change if H20 is used as a solvent instead of AcOH.9 Kinetic data for the Rh-catalyzed carbonylation of methanol have been critically analyzed. The discrepancy between the reaction rate constants is due to ignoring the effect of vapor-liquid equilibrium of the iodide promoter.10... 

One approach which enables lower water concentrations to be used for rhodium-catalysed methanol carbonylation is the addition of iodide salts, especially lithium iodide, as exemplified by the Hoechst-Celanese Acid Optimisation (AO) technology [30]. Iodide salt promoters allow carbonylation rates to be achieved at low (< 4 M) [H2O] that are comparable with those in the conventional Monsanto process (where [H20] > 10 M) while maintaining catalyst stability. In the absence of an iodide salt promoter, lowering the water concentration would result in a decrease in the proportion of Rh existing as [Rh(CO)2l2] . However, in the iodide-promoted process, a higher concentration of methyl acetate is also employed, which reacts with the other components as shown in Eqs. 3, 7 and 8 ... 

The Boots Hoechst Celanese (BHC) ibuprofen process involves palladium-catalyzed carbonylation of a benzylic alcohol (IBPE). More recently, we performed this reaction in an aqueous biphasic system using Pd/tppts as the catalyst (Figure 9.6 tppts = triphenylphosphinetrisulfonate). This process has the advantage of easy removal of the catalyst, resulting in less contamination of the product. 

In the BHC (Boots-Hoechst Celanese) process about 3500 tons of ibuprofen per annum are produced by Pd/PPh3-catalysed carbonylation of IBPE (Figure 9) in the presence of HC1, in organic media.446 447,459 461 However, a shortcoming of this process is the cumbersome separation of the Pd/PPh3 catalyst from the... 

Boots-Hoechst-Celanese process More recently, a shorter three-step catalytic route has been developed and is illustrated in the following scheme. Here, a Pd catalyzed carbonylation reaction is employed in the final step to introduce the carboxyl group. 

In this chapter we discuss the mechanistic and other details of a few industrial carbonylation processes. These are carbonylation of methanol to acetic acid, methyl acetate to acetic anhydride, propyne to methyl methacrylate, and benzyl chloride to phenyl acetic acid. Both Monsanto and BASF manufacture acetic acid by methanol carbonylation, Reaction 4.1. The BASF process is older than the Monsanto process. The catalysts and the reaction conditions for the two processes are also different and are compared in the next section. Carbonylation of methyl acetate to acetic anhydride, according to reaction 4.2, is a successful industrial process that has been developed by Eastman Kodak. The carbonylation of propyne (methyl acetylene) in methanol to give methyl methacrylate has recently been commercialized by Shell. The Montedison carbonylation process for the manufacture of phenyl acetic acid from benzyl chloride is noteworthy for the clever combination of phase-transfer and organometallic catalyses. Hoechst has recently reported a novel carbonylation process for the drug ibuprofen. 

Acetic acid is made by carbonylation of methanol. U.S. 5,001,259 (to Hoechst Celanese) describes changes to the reaction medium that improve catalyst stability and productivity. U.S. 3,769,329 (to Monsanto) describes the conventional process. Is it economically attractive to implement the changes proposed by the Hoechst patent in a new world-scale plant ... 

The concept of co-carbonylation of methanol/methyl acetate mixtures was first introduced by BASF in the early 1950s, but the reaction chemistry was not fully developed to commercial realization [75]. Not until the mid-1980s, after the development of carbonylation processes to produce acetic acid and acetic anhydride, were co-carbonylation processes patented using homogeneous rhodium/iodine catalyst systems (Table 2) [2, 56]. The basic process concept is to manufacture acetic acid and acetic anhydride from methanol and carbon monoxide as the only raw materials and to generate methyl acetate within the process. Similiarly, the suitability of dimethyl ether as a raw material for the generation of the anhydride equivalent in addition to or as a substitute for methyl acetate was revealed by Hoechst [76]. To produce a small fraction of acetic acid besides acetic anhydride as the main product, the carbonylation of methyl acetate could be conducted with small amounts of water or methanol. This variant, first demonstrated by Hoechst [56], is practiced by Eastman Kodak [2]. 

BP Chemicals was the first to commercialize a combination process based on the carbonylation of methyl acetate in the presence of water at the A5 plant complex in Hull, UK, which was completed in 1988 [20]. Due to internal conflicts, Hoechst AG so far has not realized plans for a combination process. 

Based on the palladium-catalyzed carbonylation of l-(4-isobutylphenyl)etha-nol, which is produced via salt-free acylation of isobutylbenzene to 4-isobutyl-acetophenone and subsequent hydrogenation, the former Hoechst Celanese Corporation [33] developed an ecologically superior process to produce ibuprofen in a plant operating since 1992 on a 3500-ton scale (eq. (9) 1 bar = 0.1 MPa) [34]. 

Even though methanol carbonylation is the favored process for new acetic acid capacity today, existing paraffin oxidation plants remain quite competitive where coproducts can be marketed successfully [2, 3]. Over half the original capacity of acetic acid plants based on paraffin oxidation remains in use today. In North America, Hoechst Celanese operates two facilities using the butane oxidation process to make acetic acid. The reported 1994 capacity at Pampa, Texas, is 250000 metric tons/year, while that at monton, Alberta, is 75 000 metric tons/year [4]. There are two plants believed to be using the naphtha oxidation process to make acetic acid BP Chemicals in Hull, England, with a capacity of 210000 metric tons/year [5] and a state complex in Armenia (in the former USSR) with a capacity reported to be 35 000 metric tons/year [6]. 

Apart from the oxo process, a series of other reactions are carried out industrially, even if on a smaller scale. Kuraray carries out the hydrodimerization of butadiene and water to produce n-octanol (or 1,9-nonanediol) on a scale of about 5000 metric tons per year [55]. Applications which are significantly smaller up to now are, for example, the production of vitamin precursors by Rh6ne-Poulenc (cf. Scheme 2, [56]) and the production of substituted phenylacetic acids by carbonylation (Scheme 3) [57]) or of biaryls by Suzuki cross coupling (Scheme 4), both by Hoechst AG (now Clariant AG, [57,58]). 

The oxidation of olefins to carbonyl compoimds (the Wacker process in technical concerns, also called the Hoechst-Wacker process) was of great importance for the recognition of the usefulness of organometalhc homogeneous catalysis in the bulk chemicals industry [32]. The Wacker ethylene oxidation is one of the key steps in industrial homogeneous catalysis. Palladium catalysts are usually applied and have... 

The formation of C-C bonds is of key importance in organic synthesis. An important catalytic process for generating C-C bonds is provided by carbonylation. Most carbonylation reactions have a good atom economy, because most reagent atoms are transferred to the product. Therefore, there are some applications of carbonylation processes in fine chemistry, too. For example, the analgesic ibuprofen is produced by Hoechst-Celanese by carbonylation of a substituted alcohol with 100% atom efficiency according to Eq. (8-20) [7] ... 

A striking example of this is the manufacture of ibuprofen using the Boots Hoechst-Celanese process based on homogeneous catalytic carbonylation of p-isobutylphenyl-ethanol as a key step. 

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