Selectivity vinyl acetate monomer process

A gold-palladium catalyst which includes potassium acetate is very well established for the production of vinyl acetate monomer (VAM) from ethene, acetic acid and oxygen in selectivities as high as 96% (see Section 8.4). VAM is an important intermediate used in the production of polyvinyl acetate, polyvinyl butyral and a variety of other polymers, and the gold-catalysed process followed many years of industrially focused research and patent activity in a number of large industrial companies 39-43... 

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]. 

Selectivity and activity of a catalyst has a profound influence on the economics of a commercial process. Selectivity of a reaction can be of different types. These types are explained in Figure 1.1 using the examples of reactions of vinyl acetate monomer. 

Monomers are of principal interest in emulsion polymerisation, and must be chosen based on the performance requirements of the intended application. Cost is another critical factor in the selection of an appropriate monomer. The monomer cannot be completely miscible with the water phase (otherwise it would be a dispersion polymerisation), nor can it be completely insoluble (or polymerisation by conventional emulsion polymerisation could not proceed). Most monomers are sparingly soluble in water and fall within these guidelines. Typical monomers used in emulsion polymerisation processes are the styrenics (149, 353), acrylics (141), methacrylics (309), vinyl acetate (164), vinyl chloride (363), acrylonitrile (152), butadiene (307), ethylene (114), as well as various speciahty (100) and functional monomers (332). 

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