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Catalytic conversion of biomass-derived synthesis gas to fuels
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.ORCID iD: 0000-0002-5815-960X
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.ORCID iD: 0000-0001-8488-4429
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.ORCID iD: 0000-0003-3826-1858
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
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2015 (English)In: Catalysis. Volume 27, Royal Society of Chemistry, 2015, 62-143 p.Chapter in book (Refereed)
Abstract [en]

Biomass-derived fuels constitute a promising alternative for diversifying the fuel supply and reducing the consumption of fossil fuels, leading to a reduction in greenhouse gas emissions and thus mitigating global warming. Biomass can be converted to synthesis gas, which can serve as a source for various liquid and gaseous fuels. Although significant progress has been achieved in the overall process, both economic and technical challenges still need to be overcome. Many pilot plants are already in operation and the first demonstration and semi-commercial installations are under construction or starting to operate. Catalysis is a key parameter in the conversion of synthesis gas to fuels. The aim of this work is to present the latest advances in the catalytic conversion of synthesis gas to Fischer-Tropsch gasoline and diesel, synthetic natural gas, ethanol and mixed alcohols. The syntheses of methanol and dimethyl ether are also briefly reviewed.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2015. 62-143 p.
Series
Catalysis, ISSN 0140-0568 ; 27
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-167768DOI: 10.1039/9781782622697-00062Scopus ID: 2-s2.0-84926505246ISBN: 978-1-78262-054-9 (print)ISBN: 978-1-78262-269-7 (print)OAI: oai:DiVA.org:kth-167768DiVA: diva2:814583
Funder
Sida - Swedish International Development Cooperation AgencyEU, FP7, Seventh Framework Programme, FP7/2013
Note

QC 20161123

Available from: 2015-05-27 Created: 2015-05-22 Last updated: 2017-10-04Bibliographically approved
In thesis
1. Catalytic conversion of biomass-derived synthesis gas to liquid fuels
Open this publication in new window or tab >>Catalytic conversion of biomass-derived synthesis gas to liquid fuels
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Climate change is one of the biggest global threats of the 21st century. Fossil fuels constitute by far the most important energy source for transportation and the different governments are starting to take action to promote the use of cleaner fuels.

Biomass-derived fuels are a promising alternative for diversifying fuel sources, reducing fossil fuel dependency and abating greenhouse gas emissions. The research interest has quickly shifted from first-generation biofuels, obtained from food commodities, to second-generation biofuels, produced from non-food resources.

The subject of this PhD thesis is the production of second-generation biofuels via thermochemical conversion: biomass is first gasified to synthesis gas, a mixture of mainly H2 and CO; synthesis gas can then be catalytically converted to different fuels. This work summarizes six publications, which are focused on the synthesis gas conversion step.

Two processes are principally examined in this summary. The first part of the PhD thesis is devoted to the synthesis of ethanol and higher alcohols, which can be used as fuel or fuel additives. The microemulsion technique is applied in the synthesis of molybdenum-based catalysts, achieving a yield enhancement. Methanol cofeeding is also studied as a way of boosting the production of longer alcohols, but a negative effect is obtained: the main outcome of methanol addition is an increase in methane production.

The second part of the PhD thesis addresses wax hydroconversion, an essential upgrading step in the production of middle-distillate fuels via Fischer-Tropsch. Bifunctional catalysts consisting of noble metals supported on silica-alumina are considered. The deactivation of a platinum-based catalyst is investigated, sintering and coking being the main causes of decay. A comparison of platinum and palladium as catalyst metal function is also carried out, obtaining a fairly different catalytic performance of the materials in terms of conversion and selectivity, very likely due to dissimilar hydrogenation power of the metals. Finally, a kinetic model based on the Langmuir-Hinshelwood-Hougen-Watson formalism is proposed to describe the hydroconversion reactions, attaining a good fitting of the experimental data.

Abstract [sv]

Klimatförändringarna är ett av de största globala hoten under det tjugoförsta århundradet. Fossila bränslen utgör den helt dominerande energikällan för transporter och många länder börjar stödja användning av renare bränslen.

Bränslen baserade på biomassa är ett lovande alternativ för att diversifiera råvarorna, reducera beroendet av fossila råvaror och undvika växthusgaser. Forskningsintresset har snabbt skiftat från första generationens biobränslen som erhölls från mat-råvaror till andra generationens biobränslen producerade från icke ätbara-råvaror.

Ämnet för denna doktorsavhandling är produktion av andra generationens biobränslen via termokemisk omvandling. Biomassa förgasas först till syntesgas, en blandning av i huvudsak vätgas och kolmoxid; syntesgasen kan sedan katalytiskt omvandlas till olika bränslen. Detta arbete sammanfattar sex publikationer som fokuserar på steget för syntesgasomvandling.

Två processer är i huvudsak undersökta i denna sammanfattning. Den första delen av doktorsavhandlingen ägnas åt syntes av etanol och högre alkoholer som kan användas som bränsle eller bränsletillsatser. Mikroemulsionstekniken har använts vid framställningen av molybden-baserade katalysatorer, vilket gav en höjning av utbytet. Tillsatsen av metanol har också studerats som ett sätt att försöka få en högre koncentration av högre alkoholer, men en negativ effekt erhölls: huvudeffekten av metanoltillsatsen är en ökad metanproduktion.

Den andra delen av doktorsavhandlingen handlar om vätebehandling av vaxer som ett viktigt upparbetningssteg vid framställning av mellandestillat från Fischer-Tropsch processen. Bifunktionella katalysatorer som består av ädelmetaller deponerade på silica-alumina valdes. Deaktiveringen av en platinabaserad katalysator undersöktes. Sintring och koksning var huvudorsakerna till deaktiveringen. En jämförelse mellan platina och palladium som funktionella metaller genomfördes också med resultatet att det var en ganska stor skillnad mellan materialens katalytiska egenskaper vilket gav olika omsättning och selektivitet, mycket sannolikt beroende på olika reaktionsmönster hos metallerna vid vätebehandling. Slutligen föreslås en kinetisk modell baserad på en Langmuir-Hinshelwood-Hougen-Watson modell för att beskriva reaktionerna vid vätebehandling. Denna modell ger en god anpassning till experimentella data.

Abstract [es]

El cambio climático es una de las mayores amenazas del siglo XXI. Los combustibles fósiles constituyen actualmente la fuente de energía más importante para el transporte, por lo que los diferentes gobiernos están empezando a tomar medidas para promover el uso de combustibles más limpios.

Los combustibles derivados de biomasa son una alternativa prometedora para diversificar las fuentes de energía, reducir la dependencia de los combustibles fósiles y disminuir las emisiones de efecto invernadero. Los esfuerzos de los investigadores se han dirigido en los últimos años a los biocombustibles de segunda generación, producidos a partir de recursos no alimenticios.

El tema de esta tesis de doctorado es la producción de biocombustibles de segunda generación mediante conversión termoquímica: en primer lugar, la biomasa se gasifica y convierte en gas de síntesis, una mezcla formada mayoritariamente por hidrógeno y monóxido de carbono; a continuación, el gas de síntesis puede transformarse en diversos biocombustibles. Este trabajo resume seis publicaciones, centradas en la etapa de conversión del gas de síntesis. Dos procesos se estudian con mayor detalle.

En la primera parte de la tesis se investiga la producción de etanol y alcoholes largos, que pueden ser usados como combustible o como aditivos para combustible. La técnica de microemulsión se aplica en la síntesis de catalizadores basados en molibdeno, consiguiendo un incremento del rendimiento. Además, se introduce metanol en el sistema de reacción para intentar aumentar la producción de alcoholes más largos, pero los efectos obtenidos son negativos: la principal consecuencia es el incremento de la producción de metano.

La segunda parte de la tesis estudia la hidroconversión de cera, una etapa esencial en la producción de destilados medios mediante Fischer-Tropsch. Los catalizadores estudiados son bifuncionales y consisten en metales nobles soportados en sílice-alúmina. La desactivación de un catalizador de platino se investiga, siendo la sinterización y la coquización las principales causas del problema. El uso de platino y paladio como componente metálico se compara, obteniendo resultados catalíticos bastante diferentes, tanto en conversión como en selectividad, probablemente debido a su diferente capacidad de hidrogenación. Finalmente, se propone un modelo cinético, basado en el formalismo de Langmuir-Hinshelwood-Hougen-Watson, que consigue un ajuste satisfactorio de los datos experimentales.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. xiv, 91 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:9
Keyword
biofuels, Fischer-Tropsch wax, higher alcohols, hydroconversion, kinetic modelling, methanol cofeeding, microemulsion, MoS2, noble metal, syngas
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-182690 (URN)978-91-7595-862-0 (ISBN)
Public defence
2016-04-15, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160308

Available from: 2016-03-08 Created: 2016-02-22 Last updated: 2016-03-08Bibliographically approved
2. Catalytic conversion of syngas to ethanol and higher alcohols over Rh and Cu based catalysts
Open this publication in new window or tab >>Catalytic conversion of syngas to ethanol and higher alcohols over Rh and Cu based catalysts
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The thermochemical process converts almost any kind of biomass to a desired final product, i.e. gaseous or liquid transportation fuels and chemicals. The transportation fuels obtained in this way are renewable biofuels, which are alternatives to fossil fuels. During the last few years, thermochemical plants for the production of bioethanol have been launched and another is under construction. A total of about 290 million liters of ethanol are expected to be processed per year, mostly using municipal solid waste. Considerable efforts have been made in order to find a more selective catalyst for the conversion of biomass-derived syngas to ethanol.

The thesis is the summary of five publications. The first two publications (Papers I and II) review the state of the art of ethanol and higher alcohols production from biomass, as well as the current status of synthetic fuels production by other processes such as the Fischer-Tropsch synthesis. Paper III analyses the catalytic performance of a mesoporous Rh/MCM-41 (MCM-41 is a hexagonal mesoporous silica) in the synthesis of ethanol which is compared to a typical Rh/SiO2 catalyst. Exhaustive catalytic testing including the addition of water vapor and modifying the hydrogen partial pressure in the syngas feed-stream which, in addition to the catalyst characterization (XRD, BET, XPS, chemisorption, TEM and TPR) before and after the catalytic testing, have allowed concluding that some water vapor can be concentrated in the pores of the Rh/MCM-41 catalyst. The concentration of water-vapor promotes the occurrence of the water gas shift reaction, which in turn induces some secondary reactions that change the product distribution, as compared to results obtained from the typical Rh/SiO2 catalyst. These results have been verified in a wide range of syngas conversion levels (1-68 %) and for different catalyst activation procedures (catalyst reduction at 200 °C, 500 °C and no-reduction) as shown in Paper IV. Finally, similar insights about the use of mesoporous catalyst have been found over a Cu/MCM-41 catalyst, shown in Paper V. Also in Paper V, the effect of metal promoters (Fe and K) has been studied; a noticeable increase of ethanol reaction rate was found over Cu-Fe-K/MCM-41 catalyst as compared to Cu/MCM-41. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. 98 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:2
Keyword
thermochemical process, ethanol, higher alcohols, mesoporous catalysts, rhodium, copper, metal promoters
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-196808 (URN)978-91-7729-206-7 (ISBN)
Public defence
2017-01-27, Q2, Osquldas väg 10, Våning 2, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation Agency
Note

QC 20161125

Available from: 2016-11-25 Created: 2016-11-22 Last updated: 2017-02-03Bibliographically approved
3. Cobalt catalyst supports for Fischer-Tropsch synthesis
Open this publication in new window or tab >>Cobalt catalyst supports for Fischer-Tropsch synthesis
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the Fischer-Tropsch (FT) synthesis, CO and H2 (synthesis gas) are converted into hydrocarbons that can be further upgraded to high-quality fuels and chemicals. Different carbon sources such as natural gas, coal and biomass can be used as feed-stocks for the synthesis gas. In commercial applications, supported cobalt catalysts are commonly used in the FT synthesis, especially when the synthesis gas emanates from natural gas and when the desired final product is diesel. The activity and selectivity of a cobalt catalyst is dependent on several parameters, one of them being the support.

The present thesis is focused on the design, synthesis and characterization of alumina and silica materials (with and without Ce and Zr promoters) with non-conventional morphology, and evaluation of their feasibility as cobalt supports in the FT synthesis.

Ce- and Zr-alumina nanoparticles were synthesized by co-precipitation in water-in-oil microemulsion. The obtained product is amorphous alumina with highly dispersed promoters, resulting in strong cobalt-support interactions and low cobalt reducibility. By increasing the calcination temperature of the Ce-promoted support, crystalline CeO2 is obtained which apparently increases the cobalt reducibility and thereby the catalytic activity (per gram catalyst). The small pore size of the materials may induce diffusion limitations on the reactants arrival and/or result in very small cobalt particles, which favour methane over long-chain hydrocarbons. 

Successful preparations of pore expanded mesoporous silicas with 1D, 2D and 3D pore structures via the atrane route, combined with the addition of swelling agents, have been demonstrated. The advantage of this method is that pore expansion can be achieved at mild conditions and there is no need for a post-synthesis process using an autoclave system. In larger silica support pores, larger cobalt particles will be formed and the weaker the cobalt-support interactions will be. This generally results in a higher cobalt reducibility for larger-pore supports and thereby a higher catalytic activity.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017
Series
TRITA-CHE-Report, ISSN 1654-1081
Keyword
Silica, alumina, zirconium, cerium, mesoporous materials, nanoparticles, microemulsion, atrane route, cobalt catalyst, Fischer-Tropsch synthesis
National Category
Engineering and Technology
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-215121 (URN)978-91-7729-548-8 (ISBN)
Public defence
2017-10-26, L1, Drottning Kristinas väg 30, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20171004

Available from: 2017-10-04 Created: 2017-10-02 Last updated: 2017-10-05Bibliographically approved

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