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Fuel Synthesis from Syngas
Introduction
Nowadays the society we are living in is experiencing high oil prices and global warming threats, which are
mainly caused by extensive use of traditional fossil fuels such as coal and crude oil. In the future, renewable
and environmental friendly sources of energy would be more and more attractive. Synthesis gas (also called
as syngas, which is a mixture of mainly CO and H2) could potentially play a significant role in addressing the
above mentioned problems. Basically it can be derived from any carbon containing raw material: coal,
biomass such as straw and wood or even wastes. Provided that a sustainable and effective way of
electrochemical conversion is found, even CO2 and H2O could serve as initial materials for syngas
production. (Electrochemical fixation of CO2, CASE project). Then, syngas can be converted to various liquid
fuels such as methanol, Fisher-Tropsch oil (FT oil, a mixture of hydrocarbons) and higher alcohols (Figure 1).Alcohols are widely used in our society as solvents, pharmaceuticals, and starting materials for synthesis of
various chemicals, including fuels or fuel additives.1,2,3
. The scope of this project is to develop catalysts for
the direct conversion of syngas to alcohols, either methanol (low pressure synthesis) or higher alcohols.
Opportunities for syngas production and conversion of syngas to variousliquid fuels and chemicals.
Methanol Synthesis
Introduction
Synthesis of methanol from syngas (a mixture of carbon monoxide and hydrogen with small amounts of
carbon dioxide) in an industrial scale is typically carried out at elevated temperatures and pressures (up to
2500C and 100 bar respectively 4
Synthesis of methanol from synthesis gas at lower temperature and pressure are desirable if sustainable
fuel methanol is to be synthesized in decentralized units following biomass gasification or synthesis gas
), which requires high operational and investment costs. The only
commercially used catalyst for methanol production is Cu/ZnO/Al2O3, which is optimized to operate under
conditions mentioned above.
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production by electrolysis. The «Dream Carbon Cycle» is schematically illustrated in the picture below:
carbon dioxide and water are electrochemically converted to syngas (a mixture of CO and H2), which is then
converted into methanol at low pressure and temperature over a catalyst that needs to be developed.
Finally, methanol can be used as a fuel.
Why decrease temperature and pressure?
High pressure processes not only contribute significantly to the total process cost of chemical engineering
plant, but also add up certain degree of complexity to the equipment used, thus increasing the investment
costs. Consequently, low pressure process would make methanol a more sustainable fuel, botheconomically and environmentally.
From thermodynamic point of view, one has to go down in temperature in order to produce methanol from
syngas with reasonable conversion at low pressures, as it can be seen from the figure below (assuming
stoichiometric amounts of CO and H2 and no water-gas shift activity; the same trends apply for CO 2
containing mixtures):
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It is clear that at lower temperatures thermodynamic yield of methanol is sufficiently high even at low
pressures. However, at present no catalyst is known to activate the process at such low temperatures.
Research and development
Based on DFT (Density Functional Theory) calculations performed by the theoretical group at DTU Fysik and
Stanford University (Dep. of Chemical Engineering at Stanford University), it has been proposed that certain
metal alloys should be catalytically active towards methanol synthesis from syngas at lower temperatures
(150-2000C) and pressures close to atmospheric
A limited amount of work has been done in the field of using alloyed catalysts for methanol synthesis. In
the early 80s it has been shown that certain copper-thorium and copper cerium based alloys are active
towards methanol synthesis at industrial conditions 5,6
The main objective of the research is to validate DFT calculations by synthesizing, testing and
characterization of several most interesting alloyed catalysts. Depending on the progress of the research,
one of the catalysts should be optimized
. However, nothing economically more viable than
copper based catalysts has been proposed yet
Higher alcohols synthesis
Introduction
Higher alcohols (C2+OH) are very attractive as fuels or fuel additives because they have a low vapor
pressure, high water tolerance, good solubility in hydrocarbons, high heating value and high commercial
value.7
Currently, higher alcohols such as ethanol are mainly produced according to two processes. The first
process is essentially fermentation of sugars that are derived from sugarcane or corn; 2,8 the second one ishydration of ethylene produced from petroleum. However, Crutzen et al. 9
Syngas can be converted into alcohols in a two step process: first a mixture of CO and H2 is
thermochemically produced by gasification of biomass, and then syngas is converted into higher alcohols
catalytically.
found that corn-ethanol
production process can emit nitrous oxide that contributes to global warming as well. Moreover, food
shortage problems might come up if materials such as sugarcane and corn are utilized for fuel production.
Therefore, an alternative way to produce higher alcohols from syngas is favorable.
http://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://engineering.stanford.edu/research/lab_ctr_dtl.php?org=3http://engineering.stanford.edu/research/lab_ctr_dtl.php?org=3http://engineering.stanford.edu/research/lab_ctr_dtl.php?org=3http://engineering.stanford.edu/research/lab_ctr_dtl.php?org=3http://www.fys.dtu.dk/English.aspx
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The catalysts and process for the higher alcohol synthesis (HAS) can be divided into four catagories10,11,12
1. Modified methanol synthesis catalysts: alkali-doped ZnO/Cr2O3 (high temperature methanolsynthesis catalyst) and alkali-doped Cu/ZnO and Cu/Zn/Al2O3 (low temperature methanol synthesiscatalyst).
:
2. Modified FT catalysts: alkali-doped Co/Fe/Ni-Cu-Al2O3;3. Modified Mo-based catalysts: Carbides and Sulfides;4. Noble metal catalysts, Rh, Pd, Pt, Re: heterogeneous oxide supported metals and homogeneous
metal complexes;
Table 1 illustrates that the higher alcohol synthesis typically takes place at 250-325 °C, 50-200 bar, H2/CO =
1 mol/mol and GHSV = 2000-10000 h-1. In comparison the dedicated methanol synthesis operates at a
lower temperature and pressure (225 °C - 275 °C,
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Challenges
• Catalysts with high selectivity towards higher alcohols.
• Sufficiently active catalysts.
•
Cheap catalysts, i.e. based on abundant elements.• Chemical stability in synthesis gas.
The main problem lies in that the catalyst need to:
• Be efficient in breaking the C-O bond to produce long chain intermediates CxHy*, but retain a
large coverage of intact CO molecules to form CxHyCO*.
• Be efficient in hydrogenating CxHyCO* intermediates into alcohols, but not too good, as high
hydrogenation activity leads to termination as CxHy.
Approaches• Design of catalysts using both density functional theory (DFT) and literature-based prediction.
• Synthesis of catalysts by different methods such as co-precipitation and flame spray pyrolysis.
• High pressure testing of catalysts for activity and selectivity.
• Characterization techniques: BET (DTU KT), H2-TPR (DTU KT), XPS (DTU Fysik), ICP (Haldor Topsøe
A/S), and XRD (DTU Fysik).
• In-situ characterization like TEM (DTU Cen), XAS (ANKA-KIT, Inst. for chem. technol. and polymer
chem. at Univ. Karlsruhe), and XRD (DTU Fysik).
Characterization of new catalysts
The characterization of the catalyst aims at getting to know the traits of a material in many different
aspects. Important for a catalytic material is the performance to convert the Syngas into the desired
product, so a high turnover rate. But also the selectivity, the ability to convert only into the desired product
or with little byproducts is important. Both can be tested at DTU in test facilities at industrial conditions and
in microreactors with a greater control over the gas flow and heat distribution.
To get, however, a deeper insight into the basic function of a catalyst we also use methods to study
changes in the shape and the structure of the catalyst on the atomic level. This is done with x-ray
diffraction (XRD) as well as electron microscopy. What makes our characterization abilities special is thatwe are able to study the catalysts with those methods closer to their working conditions than normal x-ray
diffractometers and electron microscopes. With that, we aim for getting a deeper understanding of the
basic catalytic process on the atomic scale 19
These are some of the devices we have available:
. These information can be used by the CASE participants who
predict and synthesize the catalysts and therefore create a feedback loop to improve the catalysts
systematically.
http://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.topsoe.com/http://www.topsoe.com/http://www.topsoe.com/http://www.topsoe.com/http://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.itcp.uni-karlsruhe.de/english/index.php?PHPSESSID=b2e95a2759877d68a767c53801dd9ca0http://www.itcp.uni-karlsruhe.de/english/index.php?PHPSESSID=b2e95a2759877d68a767c53801dd9ca0http://www.itcp.uni-karlsruhe.de/english/index.php?PHPSESSID=b2e95a2759877d68a767c53801dd9ca0http://www.itcp.uni-karlsruhe.de/english/index.php?PHPSESSID=b2e95a2759877d68a767c53801dd9ca0http://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.itcp.uni-karlsruhe.de/english/index.php?PHPSESSID=b2e95a2759877d68a767c53801dd9ca0http://www.itcp.uni-karlsruhe.de/english/index.php?PHPSESSID=b2e95a2759877d68a767c53801dd9ca0http://www.cen.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.topsoe.com/http://www.topsoe.com/http://www.fys.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspx
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Titan ETEM
This machine is an Environmental Transmission Electron Microscope (ETEM). It features the full capability
of a monochromated, image Cs
aberration corrected TEM with the
possibility to study specimens in a gas
atmosphere and at elevated
temperatures. It is still possible to get
atomic resolution at these conditions
20. Within CASE, this microscope is
mainly used for dynamic studies of
the catalysts focusing on the crystal
structure, particle sizes and other
effects on the nm to Å scale. The
electron microscopes are located atthe Center for Electron Nanoscopy
(DTU Cen).
An example of a catalytic study carried out in the ETEM is CuSn:
During the catalytic process the catalyst undergoes structural changes. In this case it is
CuSn catalyst particles that sinter and get deactivated during the process.
http://www.cen.dtu.dk/English/Research/Instrumentation/TITAN_E-CELL.aspxhttp://www.cen.dtu.dk/English/Research/Instrumentation/TITAN_E-CELL.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English/Research/Instrumentation/TITAN_E-CELL.aspx
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In-situ XRD
This is an X-ray diffractometer equipped with a gas handling system and an in-situ
cell to study specimens in gas atmosphere and at elevated temperatures. The XRD
reveals the crystal structure and changes thereof during the exposure to the gas
and heat. Libraries allow identifying different phases in a mixture and during
changes. In the future it will be possible to treat and investigate the same sample
in the XRD and transfer it over to the TEM for further investigation
This XRD system is also part of DTU Cen.
Equipment for catalyst testing at low pressures at DTU
Fysik. Products are analyzed by Gas Chromatography.
High pressure fixed-bed continuous-flow reactor(maximum 110 bar and 600 °C) at Department ofChemical Engineering (DTU KT)
Diagram illustrating the catalyst testing setup.BFM: Bubble Flow Meter; MF(P)C: Mass Flow(Pressure) Controller; P: Manometer. Heattraced tubing is indicated by sinusoidal curves.
http://www.cen.dtu.dk/English/Research/Instrumentation/PANalytical_XPert_PRO_DIFFRACTOMETER.aspxhttp://www.cen.dtu.dk/English/Research/Instrumentation/PANalytical_XPert_PRO_DIFFRACTOMETER.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English/Research/Instrumentation/PANalytical_XPert_PRO_DIFFRACTOMETER.aspx
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BET-Autosorb-iQ2 (Quantachrome Instruments)
at Department of Chemical Engineering (DTU KT)
H2-TPR on NETZSCH STA-449 at Department of
Chemical Engineering (DTU KT)
Institute for Synchrotron Radiation (ISS – ANKA, Karlsruher Institut für Technologie , Germany)
List of participants
Name Affiliation
Anker Degn Jensen DTU KT
Qiongxiao Wu DTU KT
Jakob Munkholt Christensen DTU KT
Jakob Birkedal Wagner DTU Cen
Christian Danvad Damsgaard DTU Cen
Linus Daniel Leonhard Duchstein DTU Cen
Søren Dahl DTU Fysik
Irek Sharafutdinov DTU Fysik
Christian Fink Elkjær DTU Fysik
Jens Kehlet Nørskov Dep. of Chemical Engineering at Stanford University
Jan-Dierk Grunwaldt Inst. for chem. technol. and polymer chem. at Univ. Karlsruhe
Burcin Temel Haldor Topsøe A/S
http://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://anka.iss.kit.edu/english/index.phphttp://anka.iss.kit.edu/english/index.phphttp://www.kt.dtu.dk/Om_instituttet/Medarbejdere.aspx?lg=showcommon&id=1020&type=personhttp://www.kt.dtu.dk/Om_instituttet/Medarbejdere.aspx?lg=showcommon&id=1020&type=personhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/Om_instituttet/Medarbejdere.aspx?lg=showcommon&id=60115&type=personhttp://www.kt.dtu.dk/Om_instituttet/Medarbejdere.aspx?lg=showcommon&id=60115&type=personhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/Om_instituttet/Medarbejdere.aspx?lg=showcommon&id=17576&type=personhttp://www.kt.dtu.dk/Om_instituttet/Medarbejdere.aspx?lg=showcommon&id=17576&type=personhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English/Staff.aspx?lg=showcommon&id=43950&type=personhttp://www.cen.dtu.dk/English/Staff.aspx?lg=showcommon&id=43950&type=personhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English/Staff.aspx?lg=showcommon&id=9800&type=personhttp://www.cen.dtu.dk/English/Staff.aspx?lg=showcommon&id=9800&type=personhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English/Staff.aspx?lg=showcommon&id=59812&type=personhttp://www.cen.dtu.dk/English/Staff.aspx?lg=showcommon&id=59812&type=personhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.fys.dtu.dk/Medarbejdere/Samlet_medarbejderstab.aspx?lg=showcommon&id=437&type=personhttp://www.fys.dtu.dk/Medarbejdere/Samlet_medarbejderstab.aspx?lg=showcommon&id=437&type=personhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/Medarbejdere/Samlet_medarbejderstab.aspx?lg=showcommon&id=60915&type=personhttp://www.fys.dtu.dk/Medarbejdere/Samlet_medarbejderstab.aspx?lg=showcommon&id=60915&type=personhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://engineering.stanford.edu/research/layout.php?sunetid=norskovhttp://engineering.stanford.edu/research/layout.php?sunetid=norskovhttp://engineering.stanford.edu/research/lab_ctr_dtl.php?org=3http://engineering.stanford.edu/research/lab_ctr_dtl.php?org=3http://www.itcp.kit.edu/grunwaldt/24.phphttp://www.itcp.kit.edu/grunwaldt/24.phphttp://www.itcp.uni-karlsruhe.de/english/index.php?PHPSESSID=b2e95a2759877d68a767c53801dd9ca0http://www.itcp.uni-karlsruhe.de/english/index.php?PHPSESSID=b2e95a2759877d68a767c53801dd9ca0http://www.topsoe.com/http://www.topsoe.com/http://www.topsoe.com/http://www.itcp.uni-karlsruhe.de/english/index.php?PHPSESSID=b2e95a2759877d68a767c53801dd9ca0http://www.itcp.kit.edu/grunwaldt/24.phphttp://engineering.stanford.edu/research/lab_ctr_dtl.php?org=3http://engineering.stanford.edu/research/layout.php?sunetid=norskovhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/Medarbejdere/Samlet_medarbejderstab.aspx?lg=showcommon&id=60915&type=personhttp://www.fys.dtu.dk/English.aspxhttp://www.fys.dtu.dk/Medarbejdere/Samlet_medarbejderstab.aspx?lg=showcommon&id=437&type=personhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English/Staff.aspx?lg=showcommon&id=59812&type=personhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English/Staff.aspx?lg=showcommon&id=9800&type=personhttp://www.cen.dtu.dk/English.aspxhttp://www.cen.dtu.dk/English/Staff.aspx?lg=showcommon&id=43950&type=personhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/Om_instituttet/Medarbejdere.aspx?lg=showcommon&id=17576&type=personhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/Om_instituttet/Medarbejdere.aspx?lg=showcommon&id=60115&type=personhttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/Om_instituttet/Medarbejdere.aspx?lg=showcommon&id=1020&type=personhttp://anka.iss.kit.edu/english/index.phphttp://anka.iss.kit.edu/english/index.phphttp://www.kt.dtu.dk/English.aspxhttp://www.kt.dtu.dk/English.aspx
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