Core Technologies

Oxidation

Developed in partnership with The Dow Chemical Company (Dow)

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Oxidation

In terms of organic chemistry, oxidation is defined as a reaction which causes carbon to lose electron density.

This can be caused by a carbon atom forming a bond with a more electronegative atom (e.g. oxygen, nitrogen), or breaking a bond with a less electronegative atom (e.g. hydrogen).

Consequently a hydrocarbon reacting with oxygen to form new C-O bonds constitutes an oxidation reaction.

In Context

JM Davy’s liquid-phase oxidation technology forms part of our purified terephthalic acid (PTA) process, which is based on the COMPRESS™ PTA flowsheet we developed in conjunction with Dow.

COMPRESS™ PTA employs conventional chemistry with a breakthrough combination of proven processes to generate high-quality product with less equipment and a smaller plot space.

The oxidation stage of COMPRESS™ PTA sees para-xylene oxidise to terephthalic acid via the overall reaction shown:

The resulting crude terephthalic acid (CTA) then undergoes a streamlined series of hydrogenation, crystallisation, filtration and drying steps to yield the final purified terephthalic acid (PTA) product.

Oxidation Flowsheet

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Process Description

The Davy oxidation system, based on COMPRESS™ PTA technology, comprises a simple liquid-phase oxidation step followed by crystallisation and drying to yield a solid product.

The process feedstock consists of reactant dissolved in a solvent. Catalysts are also present in the mixture, and will usually include bromide, cobalt and manganese ions.

This feed enters the oxidation vessel at moderate temperature and pressure. As air blows through the reactor, a proprietary agitation system ensures the reactants are well mixed and causes oxidation to proceed.

Solvent, along with water produced by the oxidation reaction, vaporise as they absorb the heat of reaction.

The majority of these vapours are condensed and recycled back to the oxidation reactor. However, to ensure the water content in the reaction vessel remains constant, a portion of these off gasses are sent to distillation, which separates the solvent and water. The recovered solvent recycles back to the reactor while the water is used elsewhere.

The oxidation product is largely insoluble, and consequently the reactor contains significant amounts of solid product crystals which form a slurry with the solvent.

The slurry proceeds through a series of vessels which flash cool the mixture and induce further product crystallisation.

The resulting flash vapours go to the solvent recovery distillation column, while the remaining process slurry proceeds to rotary pressure filtration which recovers the product crystals.

A final drying stage removes residual liquor from the solid product.

The JM Davy Advantage

Davy oxidation is based upon COMPRESS™ PTA technology, a streamlined process using conventional chemistry and the breakthrough combination of demonstrated pressure filtration, solvent recovery and integrated water recycle processes.

Our advanced approach to oxidation offers the following advantages:

+Lower investment cost:

  • COMPRESS™ PTA substantially reduces equipment count by utilization of pressure filtration technology, improved solvent recovery unit operation and simplification of the product drying and feed preparation systems.
  • As a result, the investment cost is approximately 15% lower compared to other technologies.

+Compact process layout:

  • The COMPRESS™ PTA process requires a smaller footprint, with an average reduction in size of approximately 25%.

+Higher process reliability:

  • The simplified process flowsheet for COMPRESS™ PTA incorporates a reduced number of rotating equipment items, fewer control loops and improved metallurgy for a more reliable process that is easier to operate.
  • This, in turn, delivers increased productivity.

+Lower operating costs:

  • Operating costs are approximately 20% lower, due to decreased electrical power consumption, reduced cooling and demin water demands, and lower steam consumption through optimized energy efficiency and heat integration.

+Reduced environmental impact:

  • Lower emissions and liquid waste.
Related Processes

Our oxidation technology forms the core of our purified terephthalic acid (PTA) process.

Explore Davy PTA here:


Related Processes

Our oxidation technology forms the core of our purified terephthalic acid (PTA) process.

Explore Davy PTA here: