Methylacetate carbonylation

Table 2.49 Hydrogen bonding parameters calculated with 6-31G basis set for complex pairing formamide with carbonyl and alkoxy oxygen atoms of methylacetate . Geometry optimized at SCF level. Counterpoise corrections for BSSE added to all energies, reported in kcal/mol.

Propionic Anhydride. Propanoic acid anhydride propanoic anhydride methylacetic anhydride. C4H,03 mol wt 130.14. C 55.37%, H 7.75%, O 36.88%. (CH,CH3O0)jO. Obtained by dehydration of the acid or by carbonylation of its esters Reppe, Friederich, U.S. pat 2,730,546 (1956 to Badische Aniltn- Sc. Soda-Fabrik) from propionaldehyde by air oxidation in the presence of cobalt and copper acetate catalysts McFarlane, U.S. pat, 2,491,572 (1949 to Cela-nese). Other syntheses, e.g., from ethanol and carbon monoxide. 

The hemiacetalic iridoidic intermediate 49 obtained has been successively transformed into the two corresponding enantiomers methylacetals 50 and 50a and the secondary alcoholic function on the cyclopentane ring oxidised to a carbonyl group (enantiomeric mixture 51 and 51a obtained). 

This reaction is carried out over rhodium carbonyls as catalyst using HI as a promoter. Acetic anhydride is produced from the carbonylation of methylacetate over lithium-iodide-promoted rhodium catalyst ... 

The effect of iodide and acetate on the activity and stability of rhodium catalysts for the conversion of methanol into acetic acid have been studied. Iodide salts at low water concentrations (<2 M) promote the carbonylation of methanol and stabilize the catalyst. Alkali metal iodides react with methylacetate to give methyl iodide and metal acetate the acetate may coordinate to Rh and act as an activator by forming soluble rhodium complexes and by preventing the precipitation of Rhl3. A water-gas shift process may help to increase the steady-state concentration of Rh(I). The labile phosphine oxide complex (57) is in equilibrium with the very active methanol carbonylation catalyst (58) see equation (56). 

Table 1. Comparison of Performance of Homogeneous and Heterogeneous Rh Catalysts for Methanol Carbonylation to Methylacetate at 250°C and Atmospheric Pressure ...

Novel catalysts for vapor-phase carbonylation of CH3OH without addition of promoter have been reported (69). Ni(N03)2-SnCl4/C catalyst was found to have a high activity and selectivity after thermal treatment in nitrogen atmosphere. When the reaction temperature was 260°C and space velocity was 2200 L/ (kg cat--h), the conversion of CH3OH was 27.2%, the selectivity for methylacetate was more than 90%, and space-time yield was 1.023 mol/ (kgcat-h). 

Historically, small amounts of acetic acid were also produced as a result of destructive distillation (or carbonization) of hardwoods. Around 80% of acetic acid, however, is actually manufaaured synthetically by methanol carbonylation using various catalysts, another 20% by acetaldehyde, liquid butane/naphtha oxidation, or methylacetate... 

Carbonylations and homologations of alcohols and esters. - The first example of an anionic Co acyl complex of the type postulated in the carbonylation of methanol has been isolated from [(Ph3P)2N][Co(C0) ] and Mel (51).242 A brief review summarises the conversion of methanol to acetic acid over Rh/1 catalysts.243 jhe activity of similar catalysts for the carbonylation of methylacetate to acetic anhydride has also been surveyed.244... 

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