Modeling of the molybdenum loss in iron molybdate catalyst pellets for selective oxidation of methanol to formaldehyde

Kristian Viegaard Raun, Jeppe Johannessen, Kaylee McCormack, Charlotte Clausen Appel, Sina Baier, Max Thorhauge, Martin Høj, Anker Degn Jensen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The loss of molybdenum from industrial iron molybdate (Fe2(MoO4)3) catalyst pellets with an excess of molybdenum oxide was studied during selective oxidation of methanol to formaldehyde for up to about 10 days on stream at varying reaction conditions (MeOH = 1.6–4.5%, O2 = 2.5–10%, H2O = 0–10.2 vol% in N2 and temperature = 250, 300 and 350 °C). The changing morphology and the local elemental composition in the pellets were followed for increasing time on stream. Molybdenum was shown to volatilize, leaving a depleted zone starting at the pellet surface and moving inwards with time. For temperatures ≤ 300 °C only volatilization of the excess MoO3 phase was observed. Increasing concentration of MeOH and temperature enhanced the rate of volatilization, the oxygen concentration had negligible effect, while increasing the H2O concentration decreased the volatilization rate. At 350 °C (MeOH = 4.5%, O2 = 10%, H2O = 0% in N2) Mo in the Fe2(MoO4)3 phase was furthermore volatilized leading to the formation of the reduced ferrous molybdate (FeMoO4). A dynamic 1D mathematical model for a single pellet, in which methanol oxidation to formaldehyde and simultaneous volatilization of free MoO3 takes place, was developed. The model parameters were fitted using experimental data of the pellet weight loss while the evolution of the MoO3 depletion layer thickness was used to validate the model. The model describes the data well and additionally predicts that deposition of MoO3 behind the depletion layer front occurs under certain conditions, leading to a MoO3 deposition layer, which was verified by scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). Simulations with the model show that the overall loss of molybdenum is significantly slower for large pellets compared to small pellets, which is a key parameter for the success of the industrial process.
Original languageEnglish
JournalChemical Engineering Journal
Volume361
Pages (from-to)1285-1295
ISSN1369-703X
DOIs
Publication statusPublished - 2019

Keywords

  • Methanol
  • Formaldehyde
  • Iron molybdate
  • Volatilization
  • Modeling

Cite this

Raun, Kristian Viegaard ; Johannessen, Jeppe ; McCormack, Kaylee ; Appel, Charlotte Clausen ; Baier, Sina ; Thorhauge, Max ; Høj, Martin ; Jensen, Anker Degn. / Modeling of the molybdenum loss in iron molybdate catalyst pellets for selective oxidation of methanol to formaldehyde. In: Chemical Engineering Journal. 2019 ; Vol. 361. pp. 1285-1295.
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title = "Modeling of the molybdenum loss in iron molybdate catalyst pellets for selective oxidation of methanol to formaldehyde",
abstract = "The loss of molybdenum from industrial iron molybdate (Fe2(MoO4)3) catalyst pellets with an excess of molybdenum oxide was studied during selective oxidation of methanol to formaldehyde for up to about 10 days on stream at varying reaction conditions (MeOH = 1.6–4.5{\%}, O2 = 2.5–10{\%}, H2O = 0–10.2 vol{\%} in N2 and temperature = 250, 300 and 350 °C). The changing morphology and the local elemental composition in the pellets were followed for increasing time on stream. Molybdenum was shown to volatilize, leaving a depleted zone starting at the pellet surface and moving inwards with time. For temperatures ≤ 300 °C only volatilization of the excess MoO3 phase was observed. Increasing concentration of MeOH and temperature enhanced the rate of volatilization, the oxygen concentration had negligible effect, while increasing the H2O concentration decreased the volatilization rate. At 350 °C (MeOH = 4.5{\%}, O2 = 10{\%}, H2O = 0{\%} in N2) Mo in the Fe2(MoO4)3 phase was furthermore volatilized leading to the formation of the reduced ferrous molybdate (FeMoO4). A dynamic 1D mathematical model for a single pellet, in which methanol oxidation to formaldehyde and simultaneous volatilization of free MoO3 takes place, was developed. The model parameters were fitted using experimental data of the pellet weight loss while the evolution of the MoO3 depletion layer thickness was used to validate the model. The model describes the data well and additionally predicts that deposition of MoO3 behind the depletion layer front occurs under certain conditions, leading to a MoO3 deposition layer, which was verified by scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). Simulations with the model show that the overall loss of molybdenum is significantly slower for large pellets compared to small pellets, which is a key parameter for the success of the industrial process.",
keywords = "Methanol, Formaldehyde, Iron molybdate, Volatilization, Modeling",
author = "Raun, {Kristian Viegaard} and Jeppe Johannessen and Kaylee McCormack and Appel, {Charlotte Clausen} and Sina Baier and Max Thorhauge and Martin H{\o}j and Jensen, {Anker Degn}",
year = "2019",
doi = "10.1016/j.cej.2018.12.142",
language = "English",
volume = "361",
pages = "1285--1295",
journal = "Biochemical Engineering Journal",
issn = "1369-703X",
publisher = "Elsevier",

}

Modeling of the molybdenum loss in iron molybdate catalyst pellets for selective oxidation of methanol to formaldehyde. / Raun, Kristian Viegaard; Johannessen, Jeppe; McCormack, Kaylee; Appel, Charlotte Clausen; Baier, Sina; Thorhauge, Max; Høj, Martin; Jensen, Anker Degn.

In: Chemical Engineering Journal, Vol. 361, 2019, p. 1285-1295.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Modeling of the molybdenum loss in iron molybdate catalyst pellets for selective oxidation of methanol to formaldehyde

AU - Raun, Kristian Viegaard

AU - Johannessen, Jeppe

AU - McCormack, Kaylee

AU - Appel, Charlotte Clausen

AU - Baier, Sina

AU - Thorhauge, Max

AU - Høj, Martin

AU - Jensen, Anker Degn

PY - 2019

Y1 - 2019

N2 - The loss of molybdenum from industrial iron molybdate (Fe2(MoO4)3) catalyst pellets with an excess of molybdenum oxide was studied during selective oxidation of methanol to formaldehyde for up to about 10 days on stream at varying reaction conditions (MeOH = 1.6–4.5%, O2 = 2.5–10%, H2O = 0–10.2 vol% in N2 and temperature = 250, 300 and 350 °C). The changing morphology and the local elemental composition in the pellets were followed for increasing time on stream. Molybdenum was shown to volatilize, leaving a depleted zone starting at the pellet surface and moving inwards with time. For temperatures ≤ 300 °C only volatilization of the excess MoO3 phase was observed. Increasing concentration of MeOH and temperature enhanced the rate of volatilization, the oxygen concentration had negligible effect, while increasing the H2O concentration decreased the volatilization rate. At 350 °C (MeOH = 4.5%, O2 = 10%, H2O = 0% in N2) Mo in the Fe2(MoO4)3 phase was furthermore volatilized leading to the formation of the reduced ferrous molybdate (FeMoO4). A dynamic 1D mathematical model for a single pellet, in which methanol oxidation to formaldehyde and simultaneous volatilization of free MoO3 takes place, was developed. The model parameters were fitted using experimental data of the pellet weight loss while the evolution of the MoO3 depletion layer thickness was used to validate the model. The model describes the data well and additionally predicts that deposition of MoO3 behind the depletion layer front occurs under certain conditions, leading to a MoO3 deposition layer, which was verified by scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). Simulations with the model show that the overall loss of molybdenum is significantly slower for large pellets compared to small pellets, which is a key parameter for the success of the industrial process.

AB - The loss of molybdenum from industrial iron molybdate (Fe2(MoO4)3) catalyst pellets with an excess of molybdenum oxide was studied during selective oxidation of methanol to formaldehyde for up to about 10 days on stream at varying reaction conditions (MeOH = 1.6–4.5%, O2 = 2.5–10%, H2O = 0–10.2 vol% in N2 and temperature = 250, 300 and 350 °C). The changing morphology and the local elemental composition in the pellets were followed for increasing time on stream. Molybdenum was shown to volatilize, leaving a depleted zone starting at the pellet surface and moving inwards with time. For temperatures ≤ 300 °C only volatilization of the excess MoO3 phase was observed. Increasing concentration of MeOH and temperature enhanced the rate of volatilization, the oxygen concentration had negligible effect, while increasing the H2O concentration decreased the volatilization rate. At 350 °C (MeOH = 4.5%, O2 = 10%, H2O = 0% in N2) Mo in the Fe2(MoO4)3 phase was furthermore volatilized leading to the formation of the reduced ferrous molybdate (FeMoO4). A dynamic 1D mathematical model for a single pellet, in which methanol oxidation to formaldehyde and simultaneous volatilization of free MoO3 takes place, was developed. The model parameters were fitted using experimental data of the pellet weight loss while the evolution of the MoO3 depletion layer thickness was used to validate the model. The model describes the data well and additionally predicts that deposition of MoO3 behind the depletion layer front occurs under certain conditions, leading to a MoO3 deposition layer, which was verified by scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). Simulations with the model show that the overall loss of molybdenum is significantly slower for large pellets compared to small pellets, which is a key parameter for the success of the industrial process.

KW - Methanol

KW - Formaldehyde

KW - Iron molybdate

KW - Volatilization

KW - Modeling

U2 - 10.1016/j.cej.2018.12.142

DO - 10.1016/j.cej.2018.12.142

M3 - Journal article

VL - 361

SP - 1285

EP - 1295

JO - Biochemical Engineering Journal

JF - Biochemical Engineering Journal

SN - 1369-703X

ER -