Ethylidene diacetate carbonylation

In the carbonylation of MeOAc to AC2O, little or no reaction corresponding to the vater gas shift takes place. Indeed it may be advantageous to feed small amounts of H2 to the process to increase catalyst activity [5]. This is also associated with the formation of ethylidene diacetate, CH3CH(OAc)2, (EDA) (Eq. (6)). 

By adjusting the C0 H2 ratio, catalytic systems for the reductive carbonylation of methyl acetate can be tuned to the production of acetic anhydride, ethylidene diacetate or acetaldehyde. 

The single step conversion of methyl acetate to ethylidene diacetate is catalyzed by either a palladium or rhodium compound, a source of iodide, and a promoter. The mechanism is described as involving the concurrent generation of acetaldehyde and acetic anhydride which subsequently react to form ethylidene diacetate. An alternative to this scheme involves independent generation of acetaldehyde by reductive carbonylation of methanol or methyl acetate, or by acetic anhydride reduction. The acetaldehyde is then reacted with anhydride in a separate step. 

Reductive Carbonylation of Methanol. As discussed earlier, rhodium based catalysts are capable of catalyzing the reductive carbonylation of methyl acetate to ethylidene diacetate ( 1), as well as the carbonylation of methyl acetate to acetic anhydride (16). These reaction proceed only, wjjen, tjie reaction environment... 

Hydride shift, as in olefin oxidation in aqueous medium, forming carbonyl compounds (see eq. (20) in Section 2.4.1) is completed under conditions in which, instead of vinyl compounds, ethylidene diacetate or acetals are formed, since using deuterated acids or alcohols, e. g., AcOD or ROD, the respective products do not contain any deuterium [3]. According to eqs. (13) and (14) with R = OAc", 0-alkyl , the step leading to these products can be interpreted as reductive elimination. 

The reaction mechanism and rates of methyl acetate carbonylation are not fully understood. In the nickel-catalyzed reaction, rate constants for formation of methyl acetate from methanol, formation of dimethyl ether, and carbonylation of dimethyl ether have been reported, as well as their sensitivity to partial pressure of the reactants (32). For the rhodium chloride [10049-07-7] catalyzed reaction, methyl acetate carbonylation is considered to go through formation of ethylidene diacetate (33) ... 

An extension of the technology associated with carbonylation of methyl acetate, namely the use of synthesis gas rather than CO alone, enables the production of other members of the acetyl chemicals family, in particular ethyl acetate, and the important monomer, vinyl acetate, via a pivotal intermediate ethylidene diacetate (1,1-diacetoxyethane). 

In chemistry developed particularly by Halcon (37) ethylidene diacetate production is catalyzed by both Rh and Pd complexes in the presence of iodide promoters. In addition, an organic promoter (tertiary phosphine or N-base (pyridine or amine)) is required for catal3d ic activity under rather higher pressures than those used for methyl acetate carbonylation, namely, 140 bar CO/H2 (1 2) and 150° C Cr complexes are also found to have an important promotional effect. Se-lectivities of up to 50% ethylidene diacetate have been claimed. However, none of this chemistry has progressed toward commercialization beyond the pilot plant stage, possibly because of the requirement for extensive acetic acid recycle in the carbonylation reactor (see also the preceding section ). 

The carbonylation of acetaldehyde dimethyl acetal or the hydrocarbonyla-tion of methyl acetate by use of rhodium catalysts yields ethylidene diacetate, which can be cracked thermally to give vinyl acetate ... 

Two processes of direct methanol carbonylation are well established already The direct carbonylation of methanol yielding acetic acid, the Monsanto process and carbonylation of methyl acetate giving acetic anhydride, a technology commercialized by Tennessee Eastman Kodak. By adjusting the CO H2 ratio, catalytic systems for the reductive carbonylation of methyl acetate can be tuned to the production of acetic anhydride, ethylidene diacetate or acetaldehyde. 

Carbonylation acetic acid, acetic anhydride, methyl acetate, methyl formate Reductive carbonylation acetaldehyde, ethanol, ethyl acetate, ethylidene diacetate Oxidative carbonylation dimethyl carbonate, dimethyl oxalate... 

At an excess of methanol in the presence of acidic catalysts and zeolites, it is possible to S5mthesize methyl acetate [287], which, when subjected to carbonylation, yields ethylidene diacetate [288] and, further, vinyl acetate monomer, one of the most important petrochemical products [289] ... 

These S5mtheses were first proposed by Halcon Company in 1980 and turned out to be 30—40% more economical than the traditional methods of producing these products. Numerous modifications of carbonylation processes aimed at producing both methyl acetate and ethylidene diacetate were patented by different companies in many coimtries aroimd the world. 

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