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Catalytic conversion of biomass-derived synthesis gas to liquid fuels
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.ORCID iD: 0000-0002-5815-960X
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 [en]
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: urn:nbn:se:kth:diva-182690ISBN: 978-91-7595-862-0 (print)OAI: oai:DiVA.org:kth-182690DiVA: diva2:905561
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
List of papers
1. Catalytic conversion of biomass-derived synthesis gas to fuels
Open this publication in new window or tab >>Catalytic conversion of biomass-derived synthesis gas to fuels
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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
Series
Catalysis, ISSN 0140-0568 ; 27
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-167768 (URN)10.1039/9781782622697-00062 (DOI)2-s2.0-84926505246 (Scopus ID)978-1-78262-054-9 (ISBN)978-1-78262-269-7 (ISBN)
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
2. Higher alcohol synthesis over nickel-modified alkali-doped molybdenum sulfide catalysts prepared by conventional coprecipitation and coprecipitation in microemulsions
Open this publication in new window or tab >>Higher alcohol synthesis over nickel-modified alkali-doped molybdenum sulfide catalysts prepared by conventional coprecipitation and coprecipitation in microemulsions
2015 (English)In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 258, 294-303 p.Article in journal (Refereed) Published
Abstract [en]

Ethanol and higher alcohols are one of the most interesting alternatives to replace fossil fuels in the transportation sector. Nickel-modified alkali-doped molybdenum sulfide is a potential catalyst for the conversion of syngas to mixed alcohols. In this work, K-Ni-MoS2 catalysts were synthetized by coprecipitation in aqueous solution or in microemulsions, followed by alkali doping. The influence of the preparation route in CO hydrogenation was investigated at 91 bar, 340/370 degrees C and GHSV= 2000-14,000 NmL/h g(catalyst). The catalysts were also characterized by TGA, ICP, XPS, nitrogen adsorption, XRD, SEM-EDX and TEM. The novel microemulsion catalyst outperformed the conventional one, resulting in higher yields of ethanol and higher alcohols. The higher activity and selectivity was attributed to a higher concentration of promoters on the microemulsion catalyst surface, together with a lower degree of crystallinity.

Place, publisher, year, edition, pages
Elsevier, 2015
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-179232 (URN)10.1016/j.cattod.2014.12.003 (DOI)000364438700011 ()2-s2.0-84945493340 (Scopus ID)
Note

QC 20160128

Available from: 2015-12-14 Created: 2015-12-14 Last updated: 2017-12-01Bibliographically approved
3. Effect of methanol addition on higher alcohol synthesis over modified molybdenum sulfide catalysts
Open this publication in new window or tab >>Effect of methanol addition on higher alcohol synthesis over modified molybdenum sulfide catalysts
2015 (English)In: Catalysis communications, ISSN 1566-7367, E-ISSN 1873-3905, Vol. 67, 103-107 p.Article in journal (Refereed) Published
Abstract [en]

One of the main problems in higher alcohol synthesis is the poor product distribution. Cofeeding of methanol, together with the synthesis gas, has been suggested in order to increase the yield of ethanol and higher alcohols. In this work, the effect of methanol addition on K-MoS<inf>2</inf> and K-Ni-MoS<inf>2</inf> catalysts was studied at 71 bar, 340 °C and GHSV = 6000 N mL/h · g<inf>catalyst</inf>. Under these conditions methanol recycle is not a viable option for boosting higher alcohol production. The main result was an increase in methane yield, while the effect in higher alcohols was negative or not significant.

Keyword
Higher alcohols, K/MoS<inf>2</inf>, Methanol cofeeding, Nickel, Syngas, Catalysts, Methane, Molybdenum compounds, Synthesis gas, Co-feeding, Higher alcohol synthesis, Methane Yield, Molybdenum sulfide, Product distributions, Syn-gas, Methanol
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-167692 (URN)10.1016/j.catcom.2015.04.018 (DOI)000355062500023 ()2-s2.0-84928007122 (Scopus ID)
Note

QC 20150602

Available from: 2015-06-02 Created: 2015-05-22 Last updated: 2017-12-04Bibliographically approved
4. Deactivation of a Pt/Silica–Alumina Catalyst and Effecton Selectivity in the Hydrocracking of n-Hexadecane
Open this publication in new window or tab >>Deactivation of a Pt/Silica–Alumina Catalyst and Effecton Selectivity in the Hydrocracking of n-Hexadecane
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2013 (English)In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, no 9-10, 594-601 p.Article in journal (Refereed) Published
Abstract [en]

The deactivation behavior of a bifunctionalcatalyst consisting of platinum on amorphous silica–aluminawas studied in the hydrocracking of n-hexadecane.The initial decline in activity and the change in selectivitywere monitored at the following reaction conditions:pressure = 30 bar; temperature = 310 C; hydrogen-tohexadecanefeed molar ratio = 10. Initially, hexadecaneconversion and selectivity to cracking products decreasedrapidly with time-on-stream, and stabilized after 40 h onstream. This could be related to an initial loss of metalsurface area, which decreased the activity of monofunctionalhydrogenolysis generating cracking products. Theacidic function seemed to be unaffected under these reactionconditions. The stable catalyst was exposed to a lowerhydrogen-to-hexadecane ratio to accelerate deactivation bycoking. A decline in the activity of both functions wasobserved. The activity of the acidic function could bealmost completely recovered by oxidative regeneration,while the metal activity was only partially recovered.

Keyword
Hydrocracking, Platinum, Amorphous silica-alumina, Hexadecane, Bifunctional catalyst, Deactivation
National Category
Other Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-129964 (URN)10.1007/s11244-013-0011-8 (DOI)000320500200011 ()2-s2.0-84879858815 (Scopus ID)
Note

QC 20131007

Available from: 2013-10-07 Created: 2013-10-07 Last updated: 2017-12-06Bibliographically approved
5. Hydroconversion of paraffinic wax over platinum and palladium catalysts supported on silica–alumina
Open this publication in new window or tab >>Hydroconversion of paraffinic wax over platinum and palladium catalysts supported on silica–alumina
Show others...
2016 (English)In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 275, 141-148 p.Article in journal (Refereed) Published
Abstract [en]

Two bifunctional catalysts consisting of platinum or palladium supported on amorphous silica–alumina were prepared and tested in hydrocracking/hydroisomerization of paraffinic wax. The performance of both noble metals was studied at the following reaction conditions: P = 35 bar; T = 300–330 °C; H2/wax = 0.1 wt/wt; WHSV = 1–4 h−1. The platinum sample was more active in hydrocracking of C22+ compounds and more selective to middle distillates. On the other hand, the palladium-based catalyst resulted in a higher isomerization degree of the products and lower amounts of methane and ethane. The higher production of light compounds over platinum is attributed to a monofunctional hydrogenolysis mechanism, in addition to the classical bifunctional route. Characterization studies showed that both catalysts had comparable metal and acid site distributions. These observations would indicate that the different catalyst performance is due to the different nature of platinum and palladium as hydrogenation/dehydrogenation function.

Keyword
Hydrocracking, Hydroisomerization, Wax, Fischer–Tropsch, Platinum, Palladium
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:kth:diva-182348 (URN)10.1016/j.cattod.2015.11.026 (DOI)000382420300020 ()2-s2.0-84982276972 (Scopus ID)
Note

QC 20160926

Available from: 2016-02-18 Created: 2016-02-18 Last updated: 2017-11-30Bibliographically approved

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