Acetic acid by carbonylation of methanol

Acetic Acid and Anhydride. Synthesis of acetic acid by carbonylation of methanol is another important homogeneous catalytic reaction. The Monsanto acetic acid process developed in the late 1960s is the best known variant of the process. 

Monsanto acetic acid A process for making acetic acid by carbonylation of methanol, catalyzed by rhodium iodide. Operated by BP. 

It is now nearly 40 years since the introduction by Monsanto of a rhodium-catalysed process for the production of acetic acid by carbonylation of methanol [1]. The so-called Monsanto process became the dominant method for manufacture of acetic acid and is one of the most successful examples of the commercial application of homogeneous catalysis. The rhodium-catalysed process was preceded by a cobalt-based system developed by BASF [2,3], which suffered from significantly lower selectivity and the necessity for much harsher conditions of temperature and pressure. Although the rhodium-catalysed system has much better activity and selectivity, the search has continued in recent years for new catalysts which improve efficiency even further. The strategies employed have involved either modifications to the rhodium-based system or the replacement of rhodium by another metal, in particular iridium. This chapter will describe some of the important recent advances in both rhodium- and iridium-catalysed methanol carbonylation. Particular emphasis will be placed on the fundamental organometallic chemistry and mechanistic understanding of these processes. 

This direct, oxidative condensation of methane to acetic acid in one-pot could be competitive with the current three-step, capital intensive process for the production of acetic acid based on methane reforming to CO, methanol synthesis from CO, and generation of acetic acid by carbonylation of methanol. Key improvements required with the PdS04/H2S04 system, however, will be to develop more stable, faster, and more selective catalysts. Although it is possible sulfuric acid could be utilized industrially as a solvent and oxidant for this reaction, it would be desirable to replace sulfuric acid with a less corrosive material. This chemistry has recently been revisited, verified, and extended by Bell et al., who used Cu(II)/02 as the oxidizing system [22],... 

On the scene of industrial chemistry, too, many sizable advances have occurred. Among them are processes for production of vinyl acetate from ethyl-ene/02/acetic acid over a heterogeneous Pd-catalyst the manufacture of acetic acid by carbonylation of methanol using a transition metal complex homoge-... 

Monsanto acetic acid A process for making acetic acid by carbonylation of methanol, catalyzed by rhodium iodide. Operated by BP. A variation of this process, the low water process, used added Group 1 metal iodides such as lithium iodide to enhance the productivity this was practiced by Celenese and by Daicel. 

The production of acetic acid by carbonylation of methanol (Equation (1)) can also be traced back to the 1950s when Reppe and coworkers at BASF developed a cobalt iodide catalyst that was effective for this reaction at relatively high temperatures and pressures 250 °C, 600 bar) [1,2]. 

Nowadays, iodine is widely used for the manufacturing of X-ray contrast media, antimicrobial products, as tinctures of polyvinylpyrrolidone-iodine (Povidone-iodine), catalysts in chemical processes (e.g. for the production of acetic acid by carbonylation of methanol in the presence of a rhodium iodide-catalyst (Monsanto process) or an iridium iodide-catalyst (Cativa process)), and also on a smaller scale for the production of pharmaceuticals like thyroid hormones. [ 83 ]... 

Another important and commercially essential example proving the variability of homogeneous catalysis is the synthesis of acetic acid via carbonylation of methanol. Here, too, a breakthrough was achieved by employing milder reaction... 

AO Plus [Acid Optimisation Plus] A process for making acetic acid by carbonylating methanol. Based on the Monsanto Acetic Acid process, but an improved catalyst (rhodium with lithium iodide) permits operation at lower levels of water. Developed by Celanese in the 1980s and operated by that company in Clear Lake, TX. Residual iodide in the product is removed by the Silverguard process. 

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 production of methyl formate by carbonylation of methanol with basic catalysts [134] can be used to separate carbon monoxide from by-product synthesis gas streams, e.g., steel-mill off-gases [135], to generate clean sources of CO for production of acetic acid by methyl formate isomerization. Therefore methyl formate could be produced near cheap CO sources and then transported to an appropriate site for conversion to acetic acid. This route to acetic acid is potentially competitive with a classic grass-roots methanol carbonylation process. Though the process has not been commercialized, numerous companies have patented the isomerization of methyl formate [136]. 

Until 1992, about 10% of the total acetic acid capacity in the United States was still based on oxidation of acetaldehyde. However, Eastman Chemical, the only domestic producer making acetic acid from acetaldehyde, shut down their unit and put it on standby at that time. As a result, all U.S. production is now by carbonylation of methanol. Some large European producers, such as BP Chemicals, are still using naphtha oxidation for acetic acid, but the amount made by acetaldehyde oxidation is nominal. 

Chemistry of Acetic Acid by Carbonylation. Two processes have been commercialized for the carbonylation of methanol to acetic acid. BASF understood the possibility of a methanol and carbon monoxide process for acetic acid, using a cobalt- and iodine-based catalyst, since the early 1920s. But development was held back by the lack of suitable construction materials for the severe operating conditions and corrosive environment necessary. The operating temperature is 250°C (482 F) and the required pressure is 680 bars (10,000 psig). In the late 1950s, development of molyb-... 

Acetic acid is mainly produced by carbonylation of methanol with carbon monoxide [30]. Most of the production of acetic acid is based on the homogeneous liquid phase Monsanto process, employing the [Rh(CO)2l2] complex as the catalyst [31]. 

Monsanto Acetic Acid Process Over a million tons of acetic acid a year are produced by carbonylation of methanol, which happens in >99% selectivity with a rhodium catalyst. The rhodium can be introduced as RhCl3 or as RhCl(CO)(PPh3)2, but the active catalyst is [Rh l2(CO)2]". The net effect is the cleavage of the methanol C-—O bond and insertion of a CO. To be... 

Formic acid is produced mainly by carbonylation of methanol to methyl formate followed by hydrolysis of this ester to formic acid and methanol [route (d) in Topic 5.3.3]. The applied reaction sequence represents formally the hydrolysis of carbon monoxide to formic acid. Owing to the growing worldwide interest in converting CO2 into useful chemicals, the catalytic hydrogenation of CO2 to formic acid has been investigated intensively but no commercial processes has been realized yet. Formic acid is also obtained as one of the side products in the catalytic oxidation of butane and light naphtha to acetic acid (see Section 6.15 for details). 

There are two major areas of commercial application of acetic add today food-grade vinegar, which is largely the product of bacterial oxidative conversion of diluted purified alcohol or alcoholic mashes from various fruits and grains, and chemically synthesized industrial acetic acid, 62 % of which is produced by carbonylation of methanol and the rest by oxidation of -butane. Chemically synthesized acetic acid is a commodity chemical that has become a major feedstock for the United States and worldwide chemical industry. O Figure 1.5 displays the major chemicals derived from acetic acid and their commercial applications. 

Over 8 million tons of acetic acid derivatives a year are produced in >99% selectivity by carbonylation of methanol with a Rh(I) catalyst, [Rhl2(CO)2] (Eq. 12.22). Tlie process is 100% atom economic since all the reactant atoms appear in the acetic acid. The net effect is the cleavage of the methanol H3C-OH bond and insertion of a CO. The methanol substrate requires activation with HI to produce an equilibrium concentration of Mel, which can oxidatively add to the metal in the turnover limiting step (Fig. 12.5). 

Acetic acid 70 000 000 190000 Petrochemical by carbonylation of methanol Biochemically using Acetobacter (aerobic) and Clostridium (anaerobic) spp. Vinyl acetate used for the production of polymers, solvents Food purposes (i.e. vinegar) [4]... 

Methyl Acetate Garbonylation. Anhydride can be made by carbonylation of methyl acetate [79-20-9] (28) in a manner analogous to methanol carbonylation to acetic acid. Methanol acetylation is an essential first step in anhydride manufacture by carbonylation. See Figure 1. The reactions are... 

Formic acid is currently produced iadustriaHy by three main processes (/) acidolysis of formate salts, which are ia turn by-products of other processes (2) as a coproduct with acetic acid ia the Hquid-phase oxidation of hydrocarbons or (3) carbonylation of methanol to methyl formate, followed either by direct hydrolysis of the ester or by the iatermediacy of formamide. 

Acetic acid is produced by direct carbonylation of methanol in the presence of a homogeneous rhodium or cobalt catalyst. 

The advent of a large international trade in methanol as a chemical feedstock has prompted additional purchase specifications, depending on the end user. Chlorides, which would be potential contaminants from seawater during ocean transport, are common downstream catalyst poisons likely to be excluded. Limitations on iron and sulfur can similarly be expected. Some users are sensitive to specific by-products for a variety of reasons. Eor example, alkaline compounds neutralize MTBE catalysts, and ethanol causes objectionable propionic acid formation in the carbonylation of methanol to acetic acid. Very high purity methanol is available from reagent vendors for small-scale electronic and pharmaceutical appHcations. 

Ca.ta.lysis, The readily accessible +1 and +3 oxidation states of rhodium make it a useful catalyst. There are several reviews of the catalytic properties of rhodium available (130—132). Rhodium-catalyzed methanol carbonylation (Monsanto process) accounted for 81% of worldwide acetic acid by 1988 (133). The Monsanto acetic acid process is carried out at 175°0 and 1.5 MPa (200 psi). Rhodium is introduced as RhCl3 but is likely reduced in a water... 

Whereas this reaction was used to oxidize ethylene (qv) to acetaldehyde (qv), which in turn was oxidized to acetic acid, the direct carbonylation of methanol (qv) to acetic acid has largely replaced the Wacker process industrially (see Acetic acid and derivatives). A large number of other oxidation reactions of hydrocarbons by oxygen involve coordination compounds as detailed elsewhere (25). 

Rather than converting methanol direcdy to ethanol, two processes have been aimounced that go through the intermediate step of converting the methanol to acetic acid by rhodium-cataly2ed carbonylation. 

The carbonylation of methanol is currently one of the major routes for acetic acid production. The basic liquid-phase process developed by BASF uses a cobalt catalyst at 250°C and a high pressure of about 70... 

Acetic acid is obtained from different sources. Carbonylation of methanol is currently the major route. Oxidation of butanes and butenes is an important source of acetic acid, especially in the U.S. (Chapter 6). It is also produced by the catalyzed oxidation of acetaldehyde ... 

Currently, the major route for obtaining acetic acid (ethanoic acid) is the carbonylation of methanol (Chapter 5). It may also be produced by the catalyzed oxidation of n-butane (Chapter 6). 

The formation of C-C bonds is of key importance in organic synthesis. An important catalytic methodology for generating C-C bonds is provided by carbonylation. In the bulk chemicals arena this is used for the production of acetic acid by methanol carbonylation (Eqn. (9)) in the presence of rhodium- or, more recently, iridium-based catalysts (Maitlis et al, 1998). 

The carbonylation of methanol was developed by Monsanto in the late 1960s. It is a large-scale operation employing a rhodium/iodide catalyst converting methanol and carbon monoxide into acetic acid. An older method involves the same carbonylation reaction carried out with a cobalt catalyst (see Section 9.3.2.4). For many years the Monsanto process has been the most attractive route for the preparation of acetic acid, but in recent years the iridium-based CATIVA process, developed by BP, has come on stream (see Section 9.3.2) ... 

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