A Model for the Phosphorus Dynamics of VPO Catalysts during the Selective Oxidation of <i>n</i>‐Butane to Maleic Anhydride in a Tubular Reactor

Diedenhoven, Jelka; Reitzmann, Andreas; Mestl, Gerhard; Turek, Thomas

doi:10.1002/cite.201100248

Cited by 14 publications

(6 citation statements)

References 3 publications

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“…The results observed in the step tests suggest that the phosphorus does not simply enter a sorption equilibrium where it covers active sites, such as proposed by Diedenhoven et al 13 and Lesser et al 19 If this were the case, after sufficiently long times, all phosphorus would have desorbed, returning the catalyst to its initial state; however, it was clearly observed that this is not the case. Instead, the phosphorus must be somehow incorporated into the catalyst structure following initial adsorption on the surface.…”

Section: ■ Resultsmentioning

confidence: 66%

“…As the total oxidation of n -butane releases significantly more heat than the partial oxidation to MA, the total heat released increases, which can ultimately lead to thermal runaway. The loss of phosphorus is countered by adding organophosphorous species (1–3 ppm, usually trimethyl phosphate) to the reactor feed to replace the lost phosphorus and maintain a constant activity of the catalyst. − ,,− …”

Section: Introductionmentioning

confidence: 99%

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Phosphorus Dosing during Catalytic n-Butane Oxidation in a μ-Reactor: A Proof of Concept

Anderson,

Kutscherauer,

Nickel

et al. 2023

Ind. Eng. Chem. Res.

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The selective oxidation of n-butane to maleic anhydride over vanadium−phosphorus oxide catalysts is subject to a dynamic change in the catalyst activity. This phenomenon is called phosphorus dynamics and plays a vital role in the prediction of catalytic reaction rates, but to date, no models measured under transport limitation free conditions have been published. This study presents the first investigation of the phosphorus dynamics over extended periods of time (multiple days on stream) under transport limitation free conditions in a μ-fixed-bed reactor. Initially, temperature variation experiments are conducted to investigate whether phosphorus dynamics takes place in a μreactor and to determine the onset of phosphorus loss. Then, a setup for dosing of liquid organophosphorous species on the scale of nL min −1 is proposed, and functionality is demonstrated via step test experiments. Results of the temperature variation showed that phosphorus loss occurs in the μ-reactor but starts at temperatures exceeding those of industrial scale reactors by 30−80 K. It was further observed that addition of steam to the feed increases the intensity of the phosphorus dynamics and lowers the onset temperature.Step test results demonstrated the functionality of the dosing setup if a suitable inert material is chosen and the metal surfaces downstream the dosing are treated according to a passivation procedure proposed in this study. The addition of steam appears to be required for appropriate distribution of the dosed organophosphorous species over the catalyst bed.

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Section: ■ Resultsmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Phosphorus Dosing during Catalytic n-Butane Oxidation in a μ-Reactor: A Proof of Concept

Anderson,

Kutscherauer,

Nickel

et al. 2023

Ind. Eng. Chem. Res.

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“…Studies have also shown that VPO catalyst performance could decrease with time due to a loss of phosphorus from the catalyst. A simple LHHW kinetic model for phosphorus dynamics has been suggested, based on reversible sorption processes, which has shown good agreement with data. This was developed into a more complex VPO surface chemistry scheme, based on the authors' own experiments and results from the literature.…”

Section: Introductionmentioning

confidence: 83%

n‐butane partial oxidation in a fixed bed: A resolved particle computational fluid dynamics simulation

Partopour

Dixon

2018

Can J Chem Eng

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Maleic anhydride (MA) is an important chemical intermediate, which is mainly produced by the highly exothermic partial oxidation of n-butane in fixed bed reactors. Production of maleic anhydride is limited by problems of temperature control and loss of selectivity. Here we present threedimensional resolved-particle computational fluid dynamics (CFD) simulations of n-butane partial oxidation in a randomly packed bed of 807 spherical catalyst particles. We used a semi-empirical two-site surface mechanism from the literature and obtained distributions of temperature, gas phase species, and surface species in the bed. The local selectivity patterns are strongly controlled by the changes in the gas phase flow field, the temperature in the fixed bed, and the weakly adsorbed oxygen surface coverage fraction (l O ) profiles inside the particles. Most of the selectivity loss due to product combustion happens in the interior of the catalyst particles, as opposed to the production of MA, which is mainly in the near-surface layers. We observed loss of selectivity and yield in the centre of the bed at increased bed depths, because of the temperature increase and decrease in gas phase oxygen there. The simulations show sharp l O gradients inside the particles. Near the cooled tube wall l O is strongly affected by the temperature, while at the bed centre gas phase oxygen diffusion limitations contribute to a depleted oxygen surface resulting in lower selectivity.

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“…Vanadium pyrophosphate (VPP) converts n ‐butane into maleic anhydride at 675 K . Mixtures of V 2 O 5 –MgO oxidatively dehydrogenate croton aldehyde to produce MA .…”

Section: Introductionmentioning

confidence: 99%

“…on alumina or silica are the most selective oxidative catalysts for AA. [19] Vanadium pyrophosphate( VPP) converts n-butanei nto maleic anhydridea t675 K. [22][23][24] Mixtures of V 2 O 5 -MgO oxidatively dehydrogenatec roton aldehyde to produceM A. [25] Benzene wast he main feedstockf or MA before 1980.…”

Section: Introductionmentioning

confidence: 99%

Gas‐Phase Partial Oxidation of Lignin to Carboxylic Acids over Vanadium Pyrophosphate and Aluminum–Vanadium–Molybdenum

2015

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Lignin is a complex polymer that is a potential feedstock for aromatic compounds and carboxylic acids by cleaving the β-O-4 and 5-5' linkages. In this work, a syringe pump atomizes an alkaline solution of lignin into a catalytic fluidized bed operating above 600 K. The vanadium heterogeneous catalysts convert all the lignin into carboxylic acids (up to 25 % selectivity), coke, carbon oxides, and hydrogen. Aluminum-vanadium-molybdenum mostly produced lactic acid (together with formic acid, acrylic acid, and maleic anhydride), whereas the vanadium pyrophosphate catalyst produced more maleic anhydride.

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A Model for the Phosphorus Dynamics of VPO Catalysts during the Selective Oxidation of n‐Butane to Maleic Anhydride in a Tubular Reactor

Cited by 14 publications

References 3 publications

Phosphorus Dosing during Catalytic n-Butane Oxidation in a μ-Reactor: A Proof of Concept

Phosphorus Dosing during Catalytic n-Butane Oxidation in a μ-Reactor: A Proof of Concept

n‐butane partial oxidation in a fixed bed: A resolved particle computational fluid dynamics simulation

Gas‐Phase Partial Oxidation of Lignin to Carboxylic Acids over Vanadium Pyrophosphate and Aluminum–Vanadium–Molybdenum

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