Industrial Monsanto process

A.sahi Chemical EHD Processes. In the late 1960s, Asahi Chemical Industries in Japan developed an alternative electrolyte system for the electroreductive coupling of acrylonitrile. The catholyte in the Asahi divided cell process consisted of an emulsion of acrylonitrile and electrolysis products in a 10% aqueous solution of tetraethyl ammonium sulfate. The concentration of acrylonitrile in the aqueous phase for the original Monsanto process was 15—20 wt %, but the Asahi process uses only about 2 wt %. Asahi claims simpler separation and purification of the adiponitrile from the catholyte. A cation-exchange membrane is employed with dilute sulfuric acid in the anode compartment. The cathode is lead containing 6% antimony, and the anode is the same alloy but also contains 0.7% silver (45). The current efficiency is of 88—89%, with an adiponitrile selectivity of 91%. This process, started by Asahi in 1971, at Nobeoka City, Japan, is also operated by the RhcJ)ne Poulenc subsidiary, Rhodia, in Bra2il under Hcense from Asahi. 

UCB-MCI [Union Chimique—Chemische Bedrijven and Ministry of Chemical Industry for the USSR] An EHD process for making adiponitrile, differing from the Monsanto process in using an emulsion of acrylonitrile and in not using a membrane. 

Whatever the source of synthesis gas, it is the starting point for many industrial chemicals. Some examples to be discussed are the hydroformylation process for converting alkenes to aldehydes and alcohols, the Monsanto process for the production of acetic acid from methanol, the synthesis of methanol from methane, and the preparation of gasoline by the Mobil and Fischer-Tropsch methods. 

As mentioned in the previous section, the carbonylation of methanol to acetic acid is an important industrial process. Whereas the [Co2(CO)s]-catalyzed, iodide-promoted reaction developed by BASF requires pressures of the order of 50 MPa, the Monsanto rhodium-catalyzed synthesis, which is also iodide promoted and which was discovered by Roth and co-workers, can be operated even at normal pressure, though somewhat higher pressures are used in the production units.4,1-413 The rhodium-catalyzed process gives a methanol conversion to acetic acid of 99%, against 90% for the cobalt reaction. The mechanism of the Monsanto process has been studied by Forster.414 The anionic complex m-[RhI2(CO)2]- (95) initiates the catalytic cycle, which is shown in Scheme 26. 

Transition-metal-catalyzed carbonylation reactions are useful one-carbon homologation techniques in organic synthesis, involving industrially important processes, for example, Fisher-Tropsch reaction, Monsanto acetic acid process, and hydroformylation (oxo reaction) [25]. 

The industrial organic electrosynthesis reaction of greatest impact must be the Monsanto process for the hydrodimerization of acrylonitrile to... 

The application of electrochemistry in organic synthesis had already served to bring on stream in the United States in 1965 Monsanto s first industrial adiponitrile process from acrylonitrile. This was followed in 1977 by a similar installation in Seal Sands, England, which was later bought up by BASF. 

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. 

The relevance of the water-gas shift reaction in the petrochemical industry has already been discussed (see Section 1.1). The significance of the water-gas shift reaction in homogeneous systems is twofold. First, it plays a crucial role in stabilizing the rhodium catalyst in the Monsanto process. Second, studies carried out in homogeneous systems employing metals other than rhodium have provided useful mechanistic insights into the heterogeneous water-gas shift reaction. We first discuss the catalytic cycle with 4.1 as one of the catalytic intermediates, and then mechanistic results that are available from an iron-based catalytic system. 

The chemistry of acetyl-CoA synthesis is thought to resemble the Monsanto process for acetate synthesis in that a metal center binds a methyl group and CO and the CO undergoes a carbonyl insertion into the methyl-metal bond. Elimination of the acetyl group is catalyzed by a strong nucleophile, iodide in the industrial process and CoA in the biochemical one. Currently, there are two views of the catalytic mechanism. 

One of the few industrial-scale processes that produces organic compounds electrochemically is used by the Monsanto Company to produce 1,4-dicyanobutane. The reduction reaction is... 

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... 

Acetic acid is a key commodity building block [1], Its most important derivative, vinyl acetate monomer, is the largest and fastest growing outlet for acetic acid. It accounts for an estimated 40 % of the total global acetic acid consumption. The majority of the remaining worldwide acetic acid production is used to manufacture other acetate esters (i.e., cellulose acetates from acetic anhydride and ethyl, propyl, and butyl esters) and monoehloroacetic acid. Acetic acid is also used as a solvent in the manufacture of terephthalic acid [2] (cf. Section 2.8.1.2). Since Monsanto commercially introduced the rhodium- catalyzed carbonylation process Monsanto process ) in 1970, over 90 % of all new acetic acid capacity worldwide is produced by this process [2], Currently, more than 50 % of the annual world acetic acid capacity of 7 million metric tons is derived from the methanol carbonylation process [2]. The low-pressure reaction conditions, the high catalyst activity, and exceptional product selectivity are key factors for the success of this process in the acetic acid industry [13]. 

The Monsanto process, one of the most successful industrial homogeneous catalytic processes, uses a Rh complex and catalytic HI to carbonylate MeOH to MeC02H. A Rh precatalyst (almost any Rh complex will do) is converted into Rh(CO)2l2, the active catalyst, under the reaction conditions. The mechanism of the reaction involves three steps. In the first step, MeOH and HI are converted to Mel and H20 by an Sn2 mechanism. In the second step, Mel and CO are converted to MeCOI under Rh catalysis. In the third step, H2O (generated in the first step) hydrolyzes MeCOI to afford MeC02H and to regenerate HI. 

Because acetic anhydride is more useful to the chemical industry than acetic acid, there was economic incentive to develop a process that would yield the anhydride directly without first producing the acid as a separate operation. By the early 1980s, Eastman Chemicals, in conjunction with Halcon Chemical Company, developed a procedure that provided acetic anhydride using technology similar to the Monsanto process, and since 1991 a plant run by Eastman has produced anhydride in excess of 500,000 metric tons per year.89 The Eastman-Halcon (E-H) operation amounts formally to inserting CO into the C-0 bond of methyl acetate according to equation 9.36.90... 

With the permission of the author [3], we borrow here data (Table 1) which indicates the production capacity of the major industrial processes using oxygen for functionalizing hydrocarbons. The production of acetic acid should be added to the list, although 60% of its 6.1 million t/year total world capacity (to reach 67% in the next future) is due to the Monsanto process (methanol carbonylation) [4]. Only the rest (2.4 million t/year) is produced by oxidation of butane or other alkanes or acetaldehyde or, for a small proportion, hy the Showa Denko process (oxidation of ethylene). 

The insertion of CO into M—Caikyi bonds is well exemplified in organometallic chemistry, and one industrial example (equation 23.36) is a step in the Monsanto process for the production of acetic acid (see Section 26.4). 

Transition metal salts and complexes also serve as homogeneous catalysts. In the Monsanto process, rhodium salts plus iodide convert methanol and carbon monoxide into an industrially useful carboxylic acid, acetic acid. The rhodium metal serves as the primary reaction site it binds the reactants and subsequently unbinds the products. The key reactions at the metal reaction site are called oxidative addition and reductive elimination. 

In 1968 Knowles at Monsanto Company, St. Louis showed that a chiral transition metal based catalyst could transfer chirality to a nonchiral substrate resulting in a chiral product with one of the enantiomers in excess. Knowles s aim was to develop an industrial synthesis process for the rare amino acid LDOPA which had proved useful in the treatment of Parkinson s... 

Another important process involving oxidative addition of alkyl halide is found in the hrst step in Monsanto process, an important industrial process to convert methanol into acetic acid with carbon monoxide at 150-200°C under 30-60 bar of CO [24]. In the Monsanto process methyl iodide is formed first from methanol and hydrogen iodide, added as the promoter to the catalytic system. The subsequent reaction of methyl iodide with a rhodium(I) species forms a methylrhodium(III) iodide species hy oxidative addition (Eq. 1.2). 

The Wacker process, the oxidation of ethylene to acetaldehyde, lost its original importance over the past 30 years. While at the beginning more than 40 factories with a total capacity of more than 2 million tons of acetaldehyde per year were installed, acetaldehyde as an industrial intermediate was replaced successively by other processes. For example, compounds such as butyraldehyde/butanol are produced by the oxo process from propylene, and acetic acid by the Monsanto process from methanol and CO or by direct oxidation of ethane. The way via acetaldehyde to these products is dependent on the price of ethylene. Petrochemical ethylene from cracking processes became considerably more expensive during these years. Thus, only few factories would be necessary to meet the demand for other derivatives of acetaldehyde such as alkyl amines, pyridines, glyoxal, and pentaerythritol. 

All known ACS enzymes are bifunctional in that they possess a C cluster with COdFI activity in addition to an A cluster (the ACS active site. Scheme 9). In the enzymes, a CO tunnel is described through which GO can pass directly from the C cluster, where it is generated from CO2, to the A cluster, where acetyl GoA synthesis takes place. Again, two mechanisms were proposed that differ in the order of binding events and redox states involved. In essence, however, GO binds to an Ni-GHs species, followed by insertion and generation of an Ni-acetyl species, which upon reaction with GoA liberates the acetyl GoA product. It is interesting to note that methylation of Ni occurs by reaction with methyl cobalamin (Scheme 7). In M. thermoacetica, the cobalamin is the cofactor for a rather unique protein called the corrinoid iron sulfur protein (GFeSP). The above process, even if mechanistic details still remain in question, resembles the industrial Monsanto acetic acid synthesis process (Scheme 9, bottom). In this case, however, the reaction is catalyzed by a low-valent Rh catalyst. 

The conversion of MeOH to MeC02H (equation 27.15) is carried out on a huge industrial scale, and 60% of the world s acetyls are manufactured using the Monsanto process. Currently, 7Mt per year of acetic acid are... 

From a historical perspective, the Monsanto process for the preparation of (l.)-DOPA in 1974 laid the foundation stone for industrial enantioselective catalysis. Since then it has been joined by a number of other asymmetric methods, such as enantioselective Sharpless epoxidation (glycidol (ARCO) and disparlure (Baker)), and cyclopropanation (cilastatin (Merck, Sumitomo) and pyre-throids (Sumitomo)). Nevertheless, besides the enantioselective hydrogenation of an imine for the production of (S)-metolachlor(a herbicide from Syngenta), the Takasago process for the production of (-)-menthol remains since 1984 as the largest worldwide industrial application of homogeneous asymmetric catalysis. [124]... 

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