Research and Thesis Projects

3) Shape-controlled nanoparticles for better catalysis

Heterogeneous catalysis is highly surface-sensitive. By using spherical nanoparticles as catalysts, we generally obtain information about the activity of different surface types, which together contribute to the observed catalytic performance. Therefore, to deduce the contribution of particular surfaces to catalytic activity, we aim to engineer metallic nanoparticles with different exposed surfaces, i.e., nanoparticles of different shapes. Nanoparticle shape determines which crystal facets are exposed (e.g., cubic nanoparticles predominantly expose {100} facets), thereby providing model systems for obtaining mechanistic insights into the catalytic activity of different surfaces.

What you will do:

• Synthesize metallic nanoparticles with controlled shapes.
• Test the performance of synthesized catalysts in CO₂ hydrogenation to methanol.
• Characterize materials using X-ray PDF, XRD, electron microscopy, and DRIFTS.
• Correlate shape parameter (exposed surfaces/facets) with catalytic activity and selectivity.

Desired skills.

• Basic chemistry lab skills are desirable.

Contact:
Dr. Diana Piankova

Project 3 together with Dr. Valery Okatenko,

Semester/Bachelor/Master Project

An extensive portfolio of industrial chemicals (acrolein, polypropene, acetone, etc.) uses propene as the starting material. Among various processes that produce propene, direct propane dehydrogenation (PDH), i.e., C₃H₈ → C₃H_{6 +} H₂, stands out as a highly selective method. Industrial PDH typically relies on Pt-containing catalysts (Oleflex or FCDh processes). However, Pt is costly and scarce, which limits its broad utilization. In addition, rapid deactivation of Pt-based catalysts due to sintering (with regeneration cycling) and coke deposition (within a catalytic cycle) lowers their efficiency. Approaches to partially overcome those deactivation pathways include alloying Pt with other metals, modifying the support, or adding promoters.[1]
Model interfaces can be created with methods such as atomic layer deposition (ALD) and surface organometallic chemistry (SOMC) and used to improve our understanding of the role of the different interfaces and speciation in PDH catalysts. In particular, ALD provides atomic-level control of the interface and surface-site engineering.[2,3] The performance in PDH of such tailored materials is assessed in this project, including the recyclability evaluation via dehydrogenation–regeneration tests. Selected catalysts are studied via advanced spectroscopy and microscopy tools to establish a relationship between the local structure and catalytic performance (activity, selectivity, stability with time on stream and after regeneration cycles).

What will you learn

• Applying ALD and SOMC techniques to prepare model PDH catalysts
• Enhancing chemical engineering expertise
• Acquiring hands-on experience in the synthesis and catalytic testing of materials
• Appreciating the complexity of industrially relevant problems and approaches to disentangle challenges in the catalysis research.

References
[1] Chem. Rev. 2014, 114, 10613–10653.
[2] Chem. Mater. 2021, 33, 3335–3348.
[3] Chem. Mater. 2023, 35, 7345–7874.

Contact
Melis Yarar

LEE P225

Over the past century, atmospheric CO₂ levels have steadily risen, driven primarily by the growing reliance on fossil fuels. The increase in CO₂ levels has been unequivocally correlated to global warming. [1] Strategies for CO₂ capture and conversion are essential for mitigating these effects. For example, the direct hydrogenation of CO₂ to methanol is a sustainable alternative to the current industrial production of methanol from synthesis gas (CO and H₂) obtained via reforming of methane (present in natural gas). [2] However, challenges to develop catalysts that are highly active, selective and stable over long operation remain.

For the rational design of effective catalysts, as opposed to the inefficient trial-and-error approaches, a key task is the identification of the relationships that link a catalyst’s geometric and electronic structure to its catalytic performance. Palladium-based catalysts are promising for this reaction exhibiting superior activity and stability compared to Cu-based ones. [3] Although Pd itself cannot activate CO₂ efficiently and hydrogenate it to methanol, the addition of a second metal (such as Ga, Zn or In) can lead to a considerable improvement in the catalytic activity and selectivity, possibly due to modification of the electronic and/or geometric local structure around Pd. [4] However, there is still limited knowledge about the active sites in these bimetallic Pd systems. Thus, this project aims to establish structure-performance relationships in bimetallic Pd-based catalysts for CO₂ hydrogenation to methanol.

We are seeking for motivated students to join our pioneering research on CO₂ hydrogenation, contributing to solutions for combating climate change by developing a fundamental understanding of catalyst behavior. Whether you’re interested in a thesis, a semester project, or a student research assistant position, we welcome your application to be part of our team. Did this spark your interest? Then contact us!

What will you do?
- Conduct daily experiments in the chemical laboratory focused on synthesizing nanomaterials for methanol production.
- Characterize nanomaterials using advanced techniques, including X-Ray Diffraction (XRD), Pair Distribution Function (PDF) analysis, and Diffuse Reflectance Infrared Spectroscopy (DRIFTS).
- Evaluate catalytic performance for CO₂ hydrogenation processes aimed at sustainable methanol synthesis.

Learning Opportunities:
- Develop a foundational understanding of CO₂ utilization technologies.
- Gain practical experience in a chemical engineering laboratory environment.
- Engage at the intersection of chemistry, engineering, and materials science.
- Gain insight into cutting-edge research conducted at ETH Zürich


Contact details
Angelo Bellia
CLA H31

References
[1]: IPCC, 2023: Sections. In: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland, pp. 35-115, doi: 10.59327/IPCC/AR6-9789291691647
[2]: Olah, G. A., Beyond Oil and Gas: The Methanol Economy. Angew. Chem. Int. Ed. 2005, 44 (18), 2636-2639.
[3]: Jiang, X.; Nie, X.; Guo, X.; Song, C.; Chen, J. G., Recent Advances in Carbon Dioxide Hydrogenation to Methanol via Heterogeneous Catalysis. Chem. Rev. 2020, 120 (15), 7984-8034.
[4]: Ojelade, O. A.; Zaman, S. F., A Review on Pd Based Catalysts for CO2 Hydrogenation to Methanol: In-Depth Activity and DRIFTS Mechanistic Study. Catal. Surv. Asia 2020, 24 (1), 11-37.


 

Bachelor thesis / Master thesis / Semester project

Chemical looping (CL) is a concept, which involves the spatial or temporal separation of a desired reaction into sub-reactions with the help of a chemical intermediate. Generally, these chemical intermediates are metal oxides, so-called oxygen carriers (OCs), that are reduced by donating lattice oxygen to a sub-reaction, and that are subsequently re-oxidized during a regeneration step, thus forming a closed loop regarding the overall process. An upcoming, promising field of application for the concept of CL is the production of value-added chemicals, due several of CL’s advantages such as the potential of heat integration, in-situ product separation, and in-situ conversion of by-products to circumvent limitations given by thermodynamic equilibrium¹.


The main challenge in designing competitive CL processes to produce value-added chemicals is the tendency of the OC to over-oxidize the carbon-based feedstock to CO_x, which has been linked to the mobility/diffusivity of oxygen in the metal oxide in several studies^2,3. Hence, this project aims at improving our understanding of the oxygen release and mobility of doped perovskite (ABO₃: A,B = metal cations) metal oxides as OCs and its implications on their selectivity as redox catalysts in chemical looping partial oxidation applications.


As an indicator for the oxygen mobility, the reducibility of the doped perovskites will be assessed by temperature-programmed reduction (TPR). In addition, electrical conductivity relaxation measurements will be carried out to explicitly determine the effect of doping on the oxygen diffusivity within the metal oxide structure. The tendency of the perovskites towards overoxidation of carbonaceous feedstock to CO₂ will be evaluated by catalytic experiments in a fixed-bed reactor. To quantify and understand the structural changes caused by doping, the perovskites will be analyzed by powder X-ray diffraction (XRD). Our goal is to correlate the structural changes imposed by doping to the oxygen mobility and ultimately to the catalytic performance of perovskites for partial oxidation reactions.

Contact:
Alexander Oing
LEE P224


References:
[1] Zhu, X., et al. Energy Environ. Sci. vol. 13 772–804 (2020).
[2] Zhu, X., et al. ACS Catal 8, 8213–8236 (2018).
[3] Zheng, Y. et al., Appl. Catal. B 202, 51–63 (2017).  

Bachelor thesis / Master thesis / Semester project

Anthropogenic CO₂ emissions and the resulting effects of climate change remain as some of the most pressing issues today. Consequently, various carbon capture and storage (CCS) technologies have been proposed to drastically reduce the emission of CO₂. The storage of CO₂, however, still poses a crucial challenge. Furthermore, most bulk products in chemical industry are derived from fossil sources, which results in a considerable carbon footprint of a vast number of everyday consumables. In this regard, carbon capture and utilization (CCU) technologies offer a promising solution to resolve challenges concerning the permanent storage of CO₂, by converting the greenhouse gas into value-added chemicals, which in turn, will also significantly contribute to the carbon neutrality of important chemical products [1].

Among CCU technologies, the hydrogenation of CO₂ to methanol has attracted increasing academic interest, due to the versatile applications of methanol, such as its utilization as a fuel additive or its facile conversion to further value-added bulk chemicals [2].

CO₂ + 3H₂ → CH₃OH + H₂O, ∆_HR,298K = -49.5 kJ/mol

The main challenge of this reaction is the activation of CO₂, which requires high energies and therefore high temperatures (e.g. T > 250 °C at 20 bar), at which the competing reverse water-gas shift (RWGS) reaction becomes thermodynamically favored, converting CO₂ into the undesired by-product CO [3]:

CO₂ + H₂ → CO + H₂O, ∆_HR,298K = +41.1 kJ/mol

Recently, mixed metal oxide catalysts such as ZnZrO_x have been reported to catalyze the hydrogenation of CO₂ at very high methanol selectivity (> 90 %) and good CO₂ conversion (10 %), while showing no sign of deactivation for over 500 hours of time on stream [4].

Our group is interested in attaining a fundamental understanding of catalyzing the hydrogenation of CO₂ to methanol over ZnZrO_x catalysts to fill the gaps where current knowledge is still lacking. We are also looking into finding new mixed metal oxide formulations to further increase the methanol productivity of this type of catalyst. In doing so, we synthesize the catalysts via impregnation or co-precipitation routes and subsequently carry out an in-depth structural characterization. Ultimately, the mixed metal oxides are evaluated catalytically, and the results are correlated to structural findings to establish structure-performance relationships.

What will you learn?
• An introduction to CO₂ conversion technologies
• Strategies on how to synthesize and characterize mixed metal oxide catalysts
• Working at the interface of engineering, materials science, and chemistry
• Improve your engineering skill-set and gain practical insight into state-of-the-art chemical/process engineering

Has this sparked your interest? Please feel free to apply or contact us for more information. The scope of the project can be adjusted to the necessary requirements.

Contact:
Alexander Oing
LEE P224


References:
[1] Ye, RP., et al. Nat. Commun. 10, 5698 (2019)
[2] Sternberg, A. & Bardow, A. Energy Environ. Sci. 8, 389–400 (2015)
[3] Kanuri, S. et al. Int. J. Energ. Res. 46, 5503–5522 (2022)
[4] Wang, J. et al. Sci. Adv. 3, e1701290 (2017)