Deactivation of a CoMo catalyst during catalytic hydropyrolysis of biomass. Part II: Characterization of the spent catalysts and char

Magnus Zingler Stummann, Martin Høj, Bente Davidsen, Lars Pilsgaard Hansen, Pablo Beato, Jostein Gabrielsen, Peter Arendt Jensen, Anker Degn Jensen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

In this work sulfided CoMo/MgAl2O4 catalysts used in fluid bed catalytic hydropyrolysis for the conversion of biomass to liquid fuels were thoroughly characterized by Raman spectroscopy and scanning (transmission) electron microscopy together with energy dispersive X-ray spectroscopy. Potassium and calcium were transferred from the biomass to the catalyst and the accumulated amounts increased proportionally with the time on stream (TOS) and reached 0.67 and 0.28 wt.% after 16.2 h, respectively, when beech wood was used as biomass feedstock with a feeding rate of approximately 270 g/h beech wood to 50 g of catalyst. The carbon content on the spent catalyst also increased with TOS and was 3.7 wt.% after 3.5 h and 7.2 wt.% after 16.2 h, indicating that the coking rate decreased with time on stream. However, SEM-EDS indicated that the carbon concentration increased more on the surface than in the bulk, thereby increasing the risk of pore blocking. In addition, Raman spectroscopy showed that the initially formed coke was mostly graphitic, but the coke became less ordered as successive layers grew on top. Doping the catalyst with K2CO3, corresponding to a potassium loading of 1.9 wt.%, prior to the sulfidation, led to a higher degree of stacking and increased the slab length of the MoS2 particles. Furthermore, SEM images of the spent catalyst indicated that the catalyst particles were encapsulated by a layer of coke during pyrolysis, but this layer was continuously removed by knock-off. This indicates that potassium acts as a catalyst for polymerization of tar and coking reactions on the catalyst. The effect of using wheat straw, which contains 10 times more potassium than beech wood, as feedstock was also investigated. This led to defluidization due to agglomeration within the first 0.3 h on stream. SEM images showed that agglomerates of char and catalyst particles, with a diameter up to 5 mm, were formed due to polymerization of the metaplast and tar. Additionally, SEM-EDS images showed that potassium was well-distributed in the agglomerates, indicating that potassium catalyzed the formation of these agglomerates.
Original languageEnglish
JournalEnergy and Fuels
Volume33
Issue number12
Pages (from-to)12387-12402
Number of pages16
ISSN0887-0624
DOIs
Publication statusPublished - 2019

Cite this

Stummann, Magnus Zingler ; Høj, Martin ; Davidsen, Bente ; Hansen, Lars Pilsgaard ; Beato, Pablo ; Gabrielsen, Jostein ; Jensen, Peter Arendt ; Jensen, Anker Degn. / Deactivation of a CoMo catalyst during catalytic hydropyrolysis of biomass. Part II: Characterization of the spent catalysts and char. In: Energy and Fuels. 2019 ; Vol. 33, No. 12. pp. 12387-12402.
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title = "Deactivation of a CoMo catalyst during catalytic hydropyrolysis of biomass. Part II: Characterization of the spent catalysts and char",
abstract = "In this work sulfided CoMo/MgAl2O4 catalysts used in fluid bed catalytic hydropyrolysis for the conversion of biomass to liquid fuels were thoroughly characterized by Raman spectroscopy and scanning (transmission) electron microscopy together with energy dispersive X-ray spectroscopy. Potassium and calcium were transferred from the biomass to the catalyst and the accumulated amounts increased proportionally with the time on stream (TOS) and reached 0.67 and 0.28 wt.{\%} after 16.2 h, respectively, when beech wood was used as biomass feedstock with a feeding rate of approximately 270 g/h beech wood to 50 g of catalyst. The carbon content on the spent catalyst also increased with TOS and was 3.7 wt.{\%} after 3.5 h and 7.2 wt.{\%} after 16.2 h, indicating that the coking rate decreased with time on stream. However, SEM-EDS indicated that the carbon concentration increased more on the surface than in the bulk, thereby increasing the risk of pore blocking. In addition, Raman spectroscopy showed that the initially formed coke was mostly graphitic, but the coke became less ordered as successive layers grew on top. Doping the catalyst with K2CO3, corresponding to a potassium loading of 1.9 wt.{\%}, prior to the sulfidation, led to a higher degree of stacking and increased the slab length of the MoS2 particles. Furthermore, SEM images of the spent catalyst indicated that the catalyst particles were encapsulated by a layer of coke during pyrolysis, but this layer was continuously removed by knock-off. This indicates that potassium acts as a catalyst for polymerization of tar and coking reactions on the catalyst. The effect of using wheat straw, which contains 10 times more potassium than beech wood, as feedstock was also investigated. This led to defluidization due to agglomeration within the first 0.3 h on stream. SEM images showed that agglomerates of char and catalyst particles, with a diameter up to 5 mm, were formed due to polymerization of the metaplast and tar. Additionally, SEM-EDS images showed that potassium was well-distributed in the agglomerates, indicating that potassium catalyzed the formation of these agglomerates.",
author = "Stummann, {Magnus Zingler} and Martin H{\o}j and Bente Davidsen and Hansen, {Lars Pilsgaard} and Pablo Beato and Jostein Gabrielsen and Jensen, {Peter Arendt} and Jensen, {Anker Degn}",
year = "2019",
doi = "10.1021/acs.energyfuels.9b02585",
language = "English",
volume = "33",
pages = "12387--12402",
journal = "Energy & Fuels",
issn = "0887-0624",
publisher = "American Chemical Society",
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Deactivation of a CoMo catalyst during catalytic hydropyrolysis of biomass. Part II: Characterization of the spent catalysts and char. / Stummann, Magnus Zingler; Høj, Martin; Davidsen, Bente ; Hansen, Lars Pilsgaard; Beato, Pablo; Gabrielsen, Jostein; Jensen, Peter Arendt; Jensen, Anker Degn.

In: Energy and Fuels, Vol. 33, No. 12, 2019, p. 12387-12402.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Deactivation of a CoMo catalyst during catalytic hydropyrolysis of biomass. Part II: Characterization of the spent catalysts and char

AU - Stummann, Magnus Zingler

AU - Høj, Martin

AU - Davidsen, Bente

AU - Hansen, Lars Pilsgaard

AU - Beato, Pablo

AU - Gabrielsen, Jostein

AU - Jensen, Peter Arendt

AU - Jensen, Anker Degn

PY - 2019

Y1 - 2019

N2 - In this work sulfided CoMo/MgAl2O4 catalysts used in fluid bed catalytic hydropyrolysis for the conversion of biomass to liquid fuels were thoroughly characterized by Raman spectroscopy and scanning (transmission) electron microscopy together with energy dispersive X-ray spectroscopy. Potassium and calcium were transferred from the biomass to the catalyst and the accumulated amounts increased proportionally with the time on stream (TOS) and reached 0.67 and 0.28 wt.% after 16.2 h, respectively, when beech wood was used as biomass feedstock with a feeding rate of approximately 270 g/h beech wood to 50 g of catalyst. The carbon content on the spent catalyst also increased with TOS and was 3.7 wt.% after 3.5 h and 7.2 wt.% after 16.2 h, indicating that the coking rate decreased with time on stream. However, SEM-EDS indicated that the carbon concentration increased more on the surface than in the bulk, thereby increasing the risk of pore blocking. In addition, Raman spectroscopy showed that the initially formed coke was mostly graphitic, but the coke became less ordered as successive layers grew on top. Doping the catalyst with K2CO3, corresponding to a potassium loading of 1.9 wt.%, prior to the sulfidation, led to a higher degree of stacking and increased the slab length of the MoS2 particles. Furthermore, SEM images of the spent catalyst indicated that the catalyst particles were encapsulated by a layer of coke during pyrolysis, but this layer was continuously removed by knock-off. This indicates that potassium acts as a catalyst for polymerization of tar and coking reactions on the catalyst. The effect of using wheat straw, which contains 10 times more potassium than beech wood, as feedstock was also investigated. This led to defluidization due to agglomeration within the first 0.3 h on stream. SEM images showed that agglomerates of char and catalyst particles, with a diameter up to 5 mm, were formed due to polymerization of the metaplast and tar. Additionally, SEM-EDS images showed that potassium was well-distributed in the agglomerates, indicating that potassium catalyzed the formation of these agglomerates.

AB - In this work sulfided CoMo/MgAl2O4 catalysts used in fluid bed catalytic hydropyrolysis for the conversion of biomass to liquid fuels were thoroughly characterized by Raman spectroscopy and scanning (transmission) electron microscopy together with energy dispersive X-ray spectroscopy. Potassium and calcium were transferred from the biomass to the catalyst and the accumulated amounts increased proportionally with the time on stream (TOS) and reached 0.67 and 0.28 wt.% after 16.2 h, respectively, when beech wood was used as biomass feedstock with a feeding rate of approximately 270 g/h beech wood to 50 g of catalyst. The carbon content on the spent catalyst also increased with TOS and was 3.7 wt.% after 3.5 h and 7.2 wt.% after 16.2 h, indicating that the coking rate decreased with time on stream. However, SEM-EDS indicated that the carbon concentration increased more on the surface than in the bulk, thereby increasing the risk of pore blocking. In addition, Raman spectroscopy showed that the initially formed coke was mostly graphitic, but the coke became less ordered as successive layers grew on top. Doping the catalyst with K2CO3, corresponding to a potassium loading of 1.9 wt.%, prior to the sulfidation, led to a higher degree of stacking and increased the slab length of the MoS2 particles. Furthermore, SEM images of the spent catalyst indicated that the catalyst particles were encapsulated by a layer of coke during pyrolysis, but this layer was continuously removed by knock-off. This indicates that potassium acts as a catalyst for polymerization of tar and coking reactions on the catalyst. The effect of using wheat straw, which contains 10 times more potassium than beech wood, as feedstock was also investigated. This led to defluidization due to agglomeration within the first 0.3 h on stream. SEM images showed that agglomerates of char and catalyst particles, with a diameter up to 5 mm, were formed due to polymerization of the metaplast and tar. Additionally, SEM-EDS images showed that potassium was well-distributed in the agglomerates, indicating that potassium catalyzed the formation of these agglomerates.

U2 - 10.1021/acs.energyfuels.9b02585

DO - 10.1021/acs.energyfuels.9b02585

M3 - Journal article

VL - 33

SP - 12387

EP - 12402

JO - Energy & Fuels

JF - Energy & Fuels

SN - 0887-0624

IS - 12

ER -