(684e) Particle-Resolved Fixed-Bed CFD for Methanol Oxidation to Formaldehyde

One of the major production processes for formaldehyde is methanol oxidation on iron molybdate,in which carbon monoxide is produced as a dominant by-product. A detailed surface chemistry model was proposed and validated by Deshmukh et al.¹ The reaction parameters were highly affected by the temperature, species concentrations, and reactor configuration. Therefore it is desirable to study the mechanism under realistic operating conditions. Particle-resolved computational fluid dynamics (PRCFD) in the fluid has been coupled to surface chemistry models and intrapellet transport.² In this work, simulations were carried out for randomly packed beds of several hundreds of particles under industrial conditions. To address the impact of particle shape on this reaction, packings of spheres, cylinders, rings and trilobes were numerically generated.³

It was shown that combustion was favored at lower temperatures. Therefore, formaldehyde mass fraction increased along the tube while inside of the upstream particles (closer to the inlet) formaldehyde concentration decreased. It was also observed that when the oxygen mass fraction approached zero inside the particles the overall reaction rate became zero. However, in the regions where methanol concentration became very low but oxygen and formaldehyde were present, combustion sped up. These observations can be used to guide operation of the reactor to improve selectivity. The advantages and drawbacks of rings compared to other particle shapes are discussed.

References

1. Deshmukh SARK, van Sint Annaland M, Kuipers JAM. Kinetics of the partial oxidation of methanol over a Fe-Mo catalyst. Appl. Catal A Gen. 2005;289:240–255.
2. Dixon AG, Taskin ME, Nijemeisland M, Stitt EH, CFD method to couple three-dimensional transport and reaction inside catalyst particles to the fixed bed flow field. Ind. Eng. Chem. Res. 2010;49:9012-9025.
3. Partopour B; Dixon AG, An integrated workflow for resolved-particle packed bed models with complex particle shapes. Powder Tech. 2017;322:258-272.