Laboratory of Alternative Fuels & Environmental Catalysis - LAFEC

09/05/2023

We are immensely proud with the new work that has come out of our laboratory, published in the reputed Catalysis Today journal (IF: 6.562).
The work is titled “CO2 hydrogenation for the production of higher alcohols: Trends in catalyst developments, challenges and opportunities” and constitutes our first foray at this new and exciting scientific field.

Higher alcohol (HA) synthesis via the hydrogenation of CO2 has the potential to help towards the de-carbonization of the energy sector however, it poses formidable challenges, as it demands the formation of at least one C-C bond, when CO2 is thermodynamically stable, fully oxidized and kinetically inert. This work provides a comprehensive and critical literature review of the catalytic formulations that have been employed, in both fixed-bed and batch reactors, which include noble metal catalysts, transition metal-based systems, post-transition metal catalysts, bimetallic, multimetallic/multifunctional catalysts, Metal Organic Frameworks (MOFs), perovskite-, and zeolite-based catalysts. The critical role of promoters and supports and the effect that the reaction conditions have on performance are also discussed. Emphasis has been given to single atom catalysts (SACs), as the high specific activity of these systems seems to hold great promise for the reaction at hand. Breakthroughs made by employing the concept of tandem catalysis are also critically analyzed. This review paper also discusses the thermodynamic aspects of the reaction and the insights that have been gained regarding the reaction mechanism. Finally, it provides an overview of the direction that research may move to into the future.

Higher alcohol (HA) synthesis via the hydrogenation of CO2 constitutes a relatively new and exciting field of research that has the potential to help …

23/01/2023

We are excited with the newest work that has come out of our Laboratory, published in ‘Advanced Science’ a journal that has the very high impact factor of 17.521.

The work has the title “Nanoparticle exsolution from nanoporous perovskites for highly active and stable biogas dry reforming catalysts” and presents a quantitative description of the exsolution of Ni nanoparticles from nanoporous perovskite oxides and their effective application in the biogas dry reforming. The exsolution process is studied between 500 and 900 °C in nanoporous and sintered La0.52Sr0.28Ti0.94Ni0.06O3±𝜹. Using temperature-programmed reduction (TPR) and X-ray absorption spectroscopy (XAS), it is shown that the faster and larger oxygen release in the nanoporous material is responsible for twice as high Ni reduction than in the sintered system. For the nanoporous material, the nanoparticle formation mechanism, studied by in situ TEM and small-angle X-ray scattering (SAXS), follows the classical nucleation theory, while on sintered systems also small endogenous nanoparticles form despite the low Ni concentration. Biogas dry reforming tests demonstrate that nanoporous exsolved catalysts are up to 18 times more active than sintered ones with 90% of CO2 conversion at 800 °C. Time-on-stream tests exhibit superior long-term stability (only 3% activity loss in 8 h) and full regenerability (over three cycles) of the nanoporous exsolved materials in comparison to a commercial Ni/Al2O3 catalyst.

This work has come about as a result of the collaboration that we enjoy (LAFEC/UOWM) with the University of Hamburg in Germany. Enjoy reading!!!

The design of nanoporous oxides represents an appealing strategy for the development of exsolved materials. Herein, the process of metal exsolution from nanoporous perovskite oxides is thoroughly des...

21/09/2022

Another work has just come out of our Laboratory, this time in the reputed Nanomaterials journal (IF= 5.719), titled “Carbon Nanostructure/Zeolite Y Composites as Supports for Monometallic and Bimetallic Hydrocracking Catalysts”.
In this study, we examine the effect of integrating different carbon nanostructures (carbon nanotubes, C**s, graphene nanoplatelets, GNPs) into Ni- and Ni-W-based bi-functional catalysts for hydrocracking of heptane performed at 400 °C. The effect of varying the SiO2/Al2O3 ratio of the zeolite Y support (between 5 and 30) on the heptane conversion is also studied. The results show that the activity, in terms of heptane conversion, followed the order CNT/Ni-ZY5 (92%) > GNP/Ni-ZY5 (89%) > CNT/Ni-W-ZY30 (86%) > GNP/Ni-W-ZY30 (85%) > CNT/Ni-ZY30 (84%) > GNP/Ni-ZY30 (83%). Thus, the CNT-based catalysts exhibited slightly higher heptane conversion as compared to the GNP-based ones. Furthermore, bimetallic (Ni-W) catalysts possessed higher BET surface areas (725 m2/g for CNT/Ni-W-ZY30 and 612 m2/g for CNT/Ni-ZY30) and exhibited enhanced hydrocracking activity as compared to the monometallic (Ni) catalyst with the same zeolite support and type of carbon structure. It was also shown that CNT-based catalysts possessed higher regeneration capability than their GNP-based counterparts due to the slightly higher thermal stability of the CVD-grown C**s.
The work was carried out with our collaborators in Khalifa University and the University of Surrey.

In this study, we examine the effect of integrating different carbon nanostructures (carbon nanotubes, C**s, graphene nanoplatelets, GNPs) into Ni- and Ni-W-based bi-functional catalysts for hydrocracking of heptane performed at 400 °C. The effect of varying the SiO2/Al2O3 ratio of the zeolite Y...

20/09/2022

Below you can find the latest scientific work coming out of our laboratory, with the title “Enhancing CO2 methanation over Ni catalysts supported on sol-gel derived Pr2O3-CeO2: An experimental and theoretical investigation” which was published in the Applied Catalysis B: Environment journal (IF= 24.319).
For this work we prepared Ni-based catalysts supported on sol-gel prepared Pr-doped CeO2 with varied porosity and nanostructure and tested them for the CO2 methanation reaction. We found that the use of ethylene glycol in the absence of H2O during a modified Pechini synthesis led to a metal oxide support with larger pore size and volume, which was conducive toward the deposition of medium-sized Ni nanoparticles confined into the nanoporous structure. The high Ni dispersion and availability of surface defects and basic sites acted to greatly improve the catalyst’s activity. CFD simulations were used to theoretically predict the catalytic performance given the reactor geometry, whereas COMSOL and ASPEN software were employed to design the models. Both modelling approaches (CFD and process simulation) showed a good validation with the experimental results and therefore confirm their ability for applications related to the prediction of the CO2 methanation behaviour.
Once again, we choose to collaborate with colleagues (and friends) from international institutions to enhance the multidisciplinary aspect of our work. The collaborating institutions were: (i) Cyprus University of Technology, (ii) University College London, (iii) Khalifa University (UAE), (iv) University of Zaragoza, and (v) University of Surrey.
Warm congratulations to all those involved!!

Ni-based catalysts supported on sol-gel prepared Pr-doped CeO2 with varied porosity and nanostructure were tested for the CO2 methanation reaction. It…

08/07/2022

The latest scientific work coming out of our lab is titled "Effect of SiO2/Al2O3 ratio in Ni/Zeolite-Y and Ni-W/Zeolite-Y catalysts on hydrocracking of heptane" and has been published to the prestigious Molecular Catalysis journal (IF = 5.089).

In this study we investigated the effect of the SiO2/Al2O3 ratio in the range of 5-80 in zeolite Y (ZY) as a support for the bi-functional reaction of heptane hydrocracking. Bi-metallicity impact, through the addition of W on Ni in the supported metal catalysts was also examined. The catalytic activity was assessed at 350°C and 400°C in order to deduce an optimized composition of the catalyst in terms of metal composition and Si/Al ratio. The results were correlated to the catalysts’ surface and bulk properties, the latter after employing a number of material characterization techniques. It was shown that Ni-W bimetallic catalysts demonstrated better catalytic activity (conversion, 78% to 91%) than Ni-based monometallic counterpart catalysts (conversion, 74.2% to 82.7%), with NiO-WO3-ZY30 (SiO2/Al2O3 ratio equal to 30) exhibiting the highest conversion. This was attributed to the bimetallic's enhanced metal dispersion and smaller particle size, evaluated using temperature-programmed desorption (TPD) of H2 and high-resolution transmission electron microscopy (HR-TEM) imaging. The stronger acidity, as quantified by total acidity calculations, of zeolite Y having higher Si/Al ratio, and their balanced ratio of micro- and meso-porosity played a vital role in their catalytic performance. This study provides useful design guidelines on how to adjust both the Si/Al ratio in the zeolite Y support and the catalyst's bimetallicity for enhanced hydrocracking performance.

The work is yet another international collaboration between LAFEC/UOWM, Khalifa University of Science and Technology (KUST) and the University of Surrey.

This study investigated the effect of the SiO2/Al2O3 ratio in the range of 5-80 in zeolite Y (ZY) as a support for the bi-functional reaction of hepta…

17/06/2022

Below you can find the link to our latest work, which has been published to the highly prestigious ACS Nano (IF = 15.881) journal; its title is "Bimetallic Exsolved Heterostructures of Controlled Composition with Tunable Catalytic Properties".

This work is the result of yet another international collaboration of our laboratory (LAFEC/UOWM), this time with the University of Hamburg (Germany), the University of Padua (Italy) and KAIST, the top science and technology university in South Korea.

In this paper, we show how the composition of bimetallic Fe−Ni exsolution can be controlled by the nature and concentration of oxygen vacancies in the parental matrix and how this is used to modify the performance of CO2-assisted ethane conversion. Mesoporous A-site-deficient La0.4Sr0.6−αTi0.6Fe0.35Ni0.05O3±δ (0 ≤ α ≤ 0.2) perovskites with substantial specific surface area (>40 m2 /g) enabled fast exsolution kinetics (T < 500 °C, t < 1 h) of bimetallic Fe−Ni nanoparticles of increasing size (3−10 nm). Through the application of a multitechnique approach we found that the A-site deficiency determined the concentration of oxygen vacancies associated with iron, which controlled the Fe reduction. Instead of homogeneous bimetallic nanoparticles, the increasing Fe fraction from 37 to 57% led to the emergence of bimodal Fe/Ni3Fe systems. Catalytic tests showed superior stability of our catalysts with respect to commercial Ni/Al2O3. Ethane reforming was found to be the favored pathway, but an increase in selectivity toward ethane dehydrogenation occurred for the systems with a low metallic Fe fraction. The chance to control the reduction and growth processes of bimetallic exsolution offers interesting prospects for the design of advanced catalysts based on bimodal nanoparticle heterostructures.

In this paper, we show how the composition of bimetallic Fe–Ni exsolution can be controlled by the nature and concentration of oxygen vacancies in the parental matrix and how this is used to modify the performance of CO2-assisted ethane conversion. Mesoporous A-site-deficient La0.4Sr0.6−αTi0.6F...

31/05/2022

Αύριο (Τετάρτη 01/06, 12:30 & 18:30), το έργο του εργαστηρίου μας θα προβληθεί στους "Άξονες Ανάπτυξης" στην ΕΡΤ3.

Συντονιστείτε!!

https://www.facebook.com/AksonesAnaptiksis/?ref=page_internal

13/05/2022

Below is the latest work from our group titled “Towards maximizing conversion of ethane and carbon dioxide into synthesis gas using highly stable Ni-perovskite catalysts”, published in the prestigious Journal of CO2 Utilization (IF = 7.132).
Dry ethane reforming (DER) aims to utilize captured CO2 and ethane, which is found in large quantities in shale gas, towards the production of high-value synthesis gas. During the dry reforming of hydrocarbons, the interaction between the active metal and the underlying support, along with the choice of the operating temperature, are considered to be the main factors influencing a catalyst’s stability and coking resistance.
In this work, the DER catalytic performance and stability of Ni-doped perovskite systems is compared with that of a typical impregnated Ni/Al2O3 catalyst. The calcined, reduced and spent catalysts are assessed using the ICP, XRD, N2 physisorption, H2-TPR, CO2-TPD, TEM, HAADF-STEM, EDS Mapping, XPS and TPO techniques. Ni-CaZrO3 (CZNO) consisting of partly exsolved Ni nanoparticles with a strong metal-support interaction is shown to be particularly stable and accumulate only a fraction of the coke that is deposited on the impregnated Ni/Al2O3 catalyst, which suffers from severe and rapid degradation under the reactant stream. By increasing the operating temperature to 750 °C, Ni-CaZrO3 can achieve almost total conversion of ethane and around 90% conversion of carbon dioxide towards synthesis gas, with no apparent loss of catalytic activity.
https://www.sciencedirect.com/science/article/pii/S2212982022001652

11/04/2022

For our newest article, published in the prestigious Journal of the Energy chemistry (IF = 9.676, ranking it 2 out of 74 in Chemistry, Applied), Ni catalysts supported on Pr-doped CeO2 were studied for the CO2 methanation reaction.
For this work, a thorough evaluation of the effect of Pr doping on the physicochemical properties of the produced materials and on their catalytic performance was carried out. We were able to show that Pr3+ ions can substitute the Ce4+ ones in the support lattice, thereby introducing a high population of oxygen vacancies, which act as active sites for CO2 chemisorption. Pr doping can also act to reduce the crystallite size of metallic Ni, thereby promoting the active metal dispersion. Catalytic performance evaluation evidenced the promoting effect of low Pr loadings (5 at% and 10 at%) towards a higher catalytic activity and lower CO2 activation energy. On the other hand, higher Pr contents negate the positive effects on the catalytic activity by decreasing the oxygen vacancy population, thereby creating a volcano type trend towards an optimum amount of aliovalent substitution.
This is yet another collaborative work carried out between LAFEC/UOWM, Khalifa University of Science and Technology (Abu Dhabi), University of Surrey (UK) and the University of Zaragoza (Spain). Moreover, for this work, our team also included the University of Delft.
We gratefully acknowledge the project “Development of new innovative low carbon energy technologies to improve excellence in the Region of Western Macedonia” (MIS 5047197) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Program "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).

In this study, Ni catalysts supported on Pr-doped CeO2 are studied for the CO2 methanation reaction and the effect of Pr doping on the physicochemical…

30/03/2022

We would like to offer our warmest congratulations to Giorgos Siakavelas ( Siakavelas), for successfully defending today his PhD thesis!!!
Dear George, the road was long, but you kept patient, working hard day and night!! As you very well know, earning a PhD degree is a huge steppingstone towards a brighter future!! You deserve the best and we are so proud of you!!!!

25/03/2022

Χρόνια Πολλά Ελλάδα !!!!!