BP PTA process

The history of the BP PTA process began in 1955 with the discovery by Scientific Design/Mid-Century Corporation of a homogeneous oxidation catalyst of combinations of cobalt(II) and manganese(II) salts and a source of bromide, and thus, the oxidation process is known by the name MC oxidation [3-6]. Patents disclosing the oxidation process were later purchased by the Standard... 

Figure 4.12 Process diagram for the oxidation section of conventional BP PTA process. (From Ref. [1].) (a) Oxidation reactor (b) surge vessel (c) filter (d) dryer (e) residue still and (f) dehydration column.

Prior to polymerization, p-xylene is first oxidized to terephthalic acid (TA) or dimethyl terephtalate (DMT). These diacid or dimethyl ester monomers are then polymerized via a condensation reaction with ethylene glycol to form the polyester. Prior to the development of a method to purify TA to make purified terephtahc acid (PTA, >99% pure) by the Mid-Century Corporation in the 1950s [10], DMT was the primary way to obtain the purified dicarboxylate. The Amoco Oil Company, now part of BP International, made several improvements to the PTA process since its inception [11]. Since the advent of the availability of PTA, it has become the monomer of choice over DMT. PTA avoids the complications of including methanol to enable purification and handling the methanol evolved during the polymerization to polyester. 

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