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Biomass pyrolysis gas conditioning over an iron-based catalyst for mild deoxygenation and hydrogen production
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. KTH.ORCID iD: 0000-0002-5395-599X
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.ORCID iD: 0000-0001-9831-6633
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.ORCID iD: 0000-0002-6326-4084
2017 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 211, 149-158 p.Article in journal (Other academic) Published
Abstract [en]

Bio-crude is a renewable source for production of valuable energy carriers. Prior to its utilization, a conditioning step of the raw pyrolysis gas can be beneficial before the bio-crude is converted via catalytic hydrodeoxygenation (HDO) into liquid hydrocarbon products, or via steam reforming (SR) to synthesis gas/hydrogen. An experimental small industrial scale study for the chemistry of atmospheric pressure pyrolysis gas conditioning resulting in bio-crude deoxygenation and a hydrogen-rich gas using an iron-based catalyst without addition of hydrogen or steam is presented and discussed. Following a short catalyst stabilization period with fluctuating bed temperatures, the catalyst operated near 450°C at a space velocity of 1100 h-1 for 8 hours under stable conditions during which no significant catalyst deactivation was observed. Experimental results indicate a 70-80% reduction of acetic acid, methoxy phenols, and catechol, and a 55-65% reduction in non-aromatic ketones, BTX, and heterocycles. Alkyl phenols and phenols were least affected, showing a 30-35% reduction. Conditioning of the pyrolysis gas resulted in a 56 % and a 18 wt% increase in water and permanent (dry) gas yield, respectively, and a 29 % loss of condensable carbon. A significant reduction of CO amount (-38 %), and production of H2 (+1063 %) and CO2 (+36 %) over the catalyst was achieved, while there was no or minimal change in light hydrocarbon content. Probing the catalyst after the test, the bulk phase of the catalyst was found to be magnetite (Fe3O4) and the catalyst exhibited significant water gas shift (WGS) reaction activity. The measured gas composition during the test was indicative of no or very limited Fischer-Tropsch (FT) CO /CO2 hydrogenation activity and this infers that also the active surface phase of the catalyst during the test was Fe-oxide, rather than Fe-carbide. The results show that iron-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way of generating a hydrogen-enriched gas without the need for bio-crude condensation.

Place, publisher, year, edition, pages
2017. Vol. 211, 149-158 p.
Keyword [en]
Bio-crude conditioning, bio-crude upgrading, gas conditioning, deoxygenation, water-gas shift
National Category
Other Chemical Engineering Other Chemistry Topics
Research subject
Chemical Engineering; Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-213136DOI: 10.1016/j.fuel.2017.09.062ISI: 000413449600017Scopus ID: 2-s2.0-85029589987OAI: oai:DiVA.org:kth-213136DiVA: diva2:1136835
Projects
Energiforsk
Funder
Swedish Energy Agency
Note

QC 20170830

Available from: 2017-08-29 Created: 2017-08-29 Last updated: 2017-11-14Bibliographically approved
In thesis
1. Catalytic Conversion of Undesired Organic Compounds to Syngas in Biomass Gasification and Pyrolysis Applications
Open this publication in new window or tab >>Catalytic Conversion of Undesired Organic Compounds to Syngas in Biomass Gasification and Pyrolysis Applications
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Reliable energy supply is a major concern and crucial for development of the global society. To address the dependency on fossil fuel and the negative effects of this reliance on climate, there is a need for a transition to cleaner sources. An attractive solution for replacing fossil-based products is renewable substitutes produced from biomass. Gasification and pyrolysis are two promising thermochemical conversion technologies, facing challenges before large-scale commercialization becomes viable. In case of biomass gasification, tar is often and undesired by-product. An attractive option to convert tar into syngas is nickel-based catalytic steam reforming (SR). For biomass pyrolysis, catalytic SR is in early stages of investigation as a feasible option for bio-crude conversion to syngas.

The focus of the thesis is partly dedicated to describe research aimed at increasing the knowledge around tar reforming mechanisms and effect of biomass-derived impurities on Ni-based tar reforming catalyst downstream of gasifiers. The work focuses on better understanding of gas-phase alkali interaction with Ni-based catalyst surface under realistic conditions. A methodology was successfully developed to enable controlled investigation of the combined sulfur (S) and potassium (K) interaction with the catalyst. The most striking result was that K appears to lower the sulfur coverage and increases methane and tar reforming activity. Additionally, the results obtained in the atomistic investigations are discussed in terms of naphthalene adsorption, dehydrogenation and carbon passivation of nickel.

Furthermore, the thesis describes research performed on pyrolysis gas pre-conditioning at a small-industrial scale, using an iron-based catalyst. Findings showed that Fe-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way for generating a hydrogen-enriched gas without the need for bio-crude condensation.

Abstract [sv]

Tillförlitlig energiförsörjning är en stor utmaning och avgörande för utvecklingen av det globala samhället. För att ta möta beroendet av fossil råvara och de negativa effekter som detta beroende medför för klimatet finns ett stort behov av en övergång till renare energiråvaror. En attraktiv lösning är att ersätta nuvarande fossil råvara med produkter från biomassa. Förgasning och pyrolys är två lovande teknologier för termokemisk omvandling av biomassa. Kommersialisering av dessa teknologier är inte helt problemfritt. I fallet förgasning så behöver, bl.a. oönskade tyngre kolväten (tjära) hanteras innan den producerade orenade produktgasen kan användas i syntesgastillämpningar. Ett effektivt alternativ för detta är gaskonditionering vid höga temperaturer, baserade på katalytisk ångreformering med en nickelkatalysator. Katalytisk ångreformering är en möjlig teknik för omvandling av bioråvara, producerad från pyrolys av biomassa, till syntesgas.

Avhandlingen fokuserar delvis på att beskriva den forskning som utförts för att öka kunskapen kring mekanismer för tjärreformering och effekterna av föroreningar från biomassan på en nickelkatalysator nedströms förgasare. Arbetet bidrar till en bättre förståelse av hur alkali i form av kalium (K) i gasfasen upptas, jämviktas och växelverkar med ytan hos nickelkatalysatorn under fullt realistiska förhållanden. Inledningsvis utvecklades en metod för att möjliggöra kontrollerade studier av den kombinerade effekten av S och K, vilken inkluderar exakt dosering av alkali till en produktgas, eliminering av transienter i katalysatoraktiviteten samt katalysatorkarakterisering. Det mest lovande resultatet är att K både sänker ytans svavelinnehåll och ökar aktiviteten för omvandlingen av metan och tjära. För att ytterligare fördjupa kunskaperna i mekanismerna för tjärnedbrytning utfördes experimentella och teoretiska ytstudier på en enkristallnickelyta med naftalen som modellförening. Resultat avseende naftalenadsorption, dehydrogenering av naftalen och kolpassivering av nickelytan diskuteras.

Därutöver så beskriver avhandlingen den forskning som utförts inom förkonditionering av pyrolysgas med en järnkatalysator för varsam deoxygenering av biooljan och vätgasproduktion. Detta utfördes vid en småskalig industriell anläggning. De experimentella studierna visar att den undersökta järnkatalysatorn resulterar i en vätgasberikad gas och att den är en potentiell kandidat för tillämpning i ett förkonditioneringssteg.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. 126 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:36
Keyword
tar reforming, biomass gasification, Ni-based catalyst, potassium, sulfur, pyrolysis gas, bio-crude conditioning, gas conditioning, Fe-based catalyst, tjärreformering, biomassaförgasning, Ni-baserad katalysator, kalium, svavel, pyrolysgas, konditionering bio-råolja, gaskonditionering, Fe-baserad katalysator
National Category
Chemical Process Engineering Other Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-213368 (URN)978-91-7729-509-9 (ISBN)
Public defence
2017-09-29, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170830

Available from: 2017-08-30 Created: 2017-08-30 Last updated: 2017-09-07Bibliographically approved

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H. Moud, PouyaKantarelis, EfthymiosEngvall, Klas

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