Acetic acid via carbonylation

A major use of methanol is the production of acetic acid via carbonylation. 

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... 

Roth JF, Craddock JH, Hershmann A, Paulik FE. (1971, Jan) Low pressure process for acetic acid via carbonylation of methanol. Chemtech, 1 600-605. 

Fig. 10.4. Acetic acid via methanol carbonylation. (Chem Systems Report No. 99/00 SB. Copyright Nexant Chem Systems, Inc. and used by permission of the copyright owner.)... 

The production of carboxylic acids via carbonylation catalysis is the second most important industrial homogeneous group of processes. Reppe developed most of the basic carbonylation chemistry in the 1930s and 1940s. The first commercial carbonylation process was the stoichiometric Ni(CO)4-based hydroxycarbonylation of acetylene to give acrylic acid (see Section 3.5 for details). This discovery has since evolved into a trae Ni-catalyzed process, used mainly by BASF. The introduction of rhodium catalysts in the 1970s revolutionized carboxylic acid production, particularly for acetic acid, much in the same way that Rh/PPhs catalysts changed the importance of hydroformylation catalysis. 

The future of the commercial acetaldehyde processes mainly depends on the availability of cheap ethylene. Acetaldehyde has been replaced as a precursor for 2-ethylhexanol ( aldol route ) or acetic acid (via oxidation cf. Sections 2.1.2.1 and 2.4.4). New processes for the manufacture of acetic acid are the Monsanto process (carbonylation of methanol, cf. Section 2.1.2.1), the Showa Denko one-step gas-phase oxidation of ethylene with a Pd-heteropolyacid catalyst [75, 76], and Wacker butene oxidation [77]. Other outlets for acetaldehyde such as pentaerythritol and pyridines cannot fill the large world production capacities. Only the present low price of ethylene keeps the Wacker process still attractive. 

Monsanto s processes to yield acetic acid via methanol carbonylation [10] or a chiral l-DOPA precursor via hydrogenation of substituted cinnamic acids [11]. 

Acetaldehyde (ethanal) used to be the most important intermediate for the production of acetic acid. However, since 1970 the production of acetaldehyde lost importance as acetic acid production switched increasingly to methanol carbonylation. The reason for this development has to do with the different feedstock base for both processes. While the production of acetaldehyde starts from ethylene, the synthesis of acetic acid via methanol carbonylation uses the significantly cheaper synthesis gas (CO/H2) as feed, from which methanol is made first followed by a carbonylation step (see Section 6.15 for details). 

Celanese has developed the so-caUed TCX process," in which methanol, formed from synthesis gas from the steam reforming of natural gas, is converted via a hydro-carbonylation reaction into acetic acid. The hydrocarbonylation of methanol is the standard method to make acetic acid via the aid of a rhodium-based catalyst as described in UUmann (Ulhnaim s Encyclopedia of Industrial Chemistry (2), 2005) ... 

Thioketals are readily formed by acid-catalyzed reaction with ethane-dithiol. Selective thioketal formation is achieved at C-3 in the presence of a 6-ketone by carrying out the boron trifluoride catalyzed reaction in diluted medium. Selective protection of the 3-carbonyl group as a thioketal has been effected in high yield with A" -3,17-diketones, A" -3,20-diketones and A" -3,l 1,17-triones in acetic acid at room temperature in the presence of p-toluenesulfonic acid. In the case of thioketals the double bond remains in the 4,5-position. This result is attributed to the greater nucleophilicity of sulfur as compared to oxygen, which promotes closure of intermediate (66) to the protonated cyclic mercaptal (67) rather than elimination to the 3,5-diene [cf. ketal (70) via intermediates (68) and (69)]." " ... 

The production of 1,4-butanediol (1,4-BDO) from propylene via the carbonylation of allyl acetate is noted in Chapter 8. 1,4-Butanediol from maleic anhydride is discussed later in this chapter. An alternative route for the diol is through the acetoxylation of butadiene with acetic acid followed by hydrogenation and hydrolysis. 

The wide latitude of structural variation consistent with bioactivity in this series is illustrated by the observation that antiinflammatory activity is maintained even when the second aromatic group is attached directly to the pyrrole nitrogen rather than to the heterocyclic ring via a carbonyl group as in the previous case. Condensation of p-chloroaniline with hexane-2,5-dione (or its dimethoxy-tetrahydrofuran equivalent) affords pyrrole 7. The acetic acid side chain is then elaborated as above. Thus, Mannich reaction leads to the dimethylaminomethyl derivative 8, which is in turn methylated (9) the quaternary nitrogen replaced by cyanide to afford 10. Hydrolysis of the nitrile then gives clopirac (11). 

The addition of a carbonylation step extended a pyrrole synthesis to pyrrole-2-acetic acid derivatives <06ASC2212>. Treatment of enyne amine 1 with palladium diiodide in the presence of CO and methanol produced pyrrole-2-acetic ester 2 via a 5-exo-dig cyclization, oxidative carbonylation, and isomerization. 

Where acetic is the starting acid (eq. 1), homologation selectively yields the corresponding C3+ aliphatic carboxylic acids. Since acetic acid is itself a "syngas" chemical derived from methanol via carbonylation (2,3), this means the higher MW carboxylic acids generated by this technique could also be built exclusively from C0/H2 and would thereby be in-depent of any petroleum-derived coreactant. 

Acetic Acid Production via Low-Pressure, Nickel-Catalyzed Methanol Carbonylation... 

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