George I. Siakavelas

George I. Siakavelas
University of Western Macedonia | UOWM · Department of Chemical Engineering

BSc, MSc Environmental Engineering, PhD

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51
Publications
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1,160
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Publications

Publications (51)
Article
The present work reports on the investigation of the catalytic performance for the methanation of CO2 over Ni catalysts based on CeO2, and for the first time, of Ni catalysts supported on binary CeO2-based oxides, namely, Sm2O3-CeO2, Pr2O3-CeO2 and MgO-CeO2. The supports were obtained using the microwave assisted sol-gel method under reflux, while...
Article
In the study presented herein, nickel catalysts supported on CeO2 and, for the first time in the literature, on La2O3-Sm2O3-CeO2, La2O3-Pr2O3-CeO2 and La2O3-MgO-CeO2 were prepared and evaluated for the reaction of CO2 methanation. The carriers were prepared through a sol-gel microwave assisted method and the catalysts were obtained following wet im...
Article
The work presented herein reports on the oxidative coupling of methane (OCM) performance of a series of Li-free and Li-doped CeO2 and CeO2 modified with Sm³⁺ and La³⁺ catalysts. The supporting materials (Ce, Sm-Ce and La-Sm-Ce metal oxides) were synthesized using the microwave assisted sol-gel method in order to achieve nanophase complex materials...
Article
The work presented herein reports on the oxidative coupling of methane (OCM) performance of a series of Li-free and Li-doped CeO2 and CeO2 modified with Mg²⁺ and La³⁺ catalysts. The supporting materials (Ce, Mg-Ce and La-Mg-Ce metal oxides) were synthesized using the microwave assisted sol-gel method, while lithium ions were added using the wet imp...
Article
Full-text available
The present review focuses on the production of renewable hydrogen through the catalytic steam reforming of bio-oil, the liquid product of the fast pyrolysis of biomass. Although in theory the process is capable of producing high yields of hydrogen, in practice, certain technological issues require radical improvements before its commercialization....
Article
Full-text available
The work presented herein studies the adsorption of C2H4 from a mixture simulating the products obtained during the oxidative coupling of CH4 (OCM), using a commercial molecular sieve (MOS). A joint experimental and theoretical approach has been employed. The adsorbent's trapping capacity decreases at higher temperatures, while the breakpoint time...
Article
Full-text available
Ni catalysts based on Al2O3 and Al2O3 modified with CaO-MgO were tested for the dry reforming of biogas (BDR). Time-on-stream experiments were carried out between 600 and 800 °C, and the spent catalysts were examined using a variety of characterization techniques including, N2 adsorption/desorption, thermogravimetric analysis (TGA), Raman spectrosc...
Article
Full-text available
A promising route for the energetic valorisation of the main by-product of the biodiesel industry is the steam reforming of glycerol, as it can theoretically produce seven moles of H 2 for every mole of C 3 H 8 O 3. In the work presented herein, CeO 2-Al 2 O 3 was used as supporting material for Ir, Pd and Pt catalysts, which were prepared using th...
Article
Full-text available
The tackling of carbon deposition during the dry reforming of biogas (BDR) necessitates research of the surface of spent catalysts in an effort to obtain a better understanding of the effect that different carbon allotropes have on the deactivation mechanism and correlation of their formation with catalytic properties. The work presented herein pro...
Article
Full-text available
In this study, a critical comparison between two low metal (Ni) loading catalysts is presented, namely Ni/Al2O3 and Ni/AlCeO3 for the glycerol steam reforming (GSR) reaction. The surface and bulk properties of the catalysts were evaluated using a plethora of techniques, such as N2 adsorption/desorption, Inductively Coupled Plasma Atomic Emission Sp...
Article
In the study presented herein, the catalytic activity and stability of a Ni catalyst supported on Y2O3-ZrO2 was examined for the first time in the glycerol steam reforming reaction and compared with a Ni/ZrO2. The addition of Y2O3 stabilized the ZrO2 tetragonal phase, increased the O2 storage capacity of the support and the medium strength acid sit...
Article
A series of Ce-Sm-xCu, (x=5, 7, 10 at.%) catalysts were prepared using coupling of microwave radiation with sol-gel method and were evaluated for the glycerol steam reforming reaction in the 400-750oC temperature range. Some critical comparison with co-precipitation catalysts is also discussed. The catalysts were characterized using BET, Raman, XRD...
Article
Nickel-based catalysts Ceria or lanthana modified zirconia Catalytic stability Carbon deposition Multiwall carbon nanotubes a b s t r a c t The dry reforming of biogas on a Ni catalyst supported on three commercially available materials (ZrO 2 , La 2 O 3 eZrO 2 and CeO 2 eZrO 2), has been investigated, paying particular attention to carbon depositi...
Conference Paper
The dry reforming of biogas is a process that makes use of the main greenhouse gases and provides a renewable resource (syngas) with zero carbon footprint. The process benefits from high temperatures as the main reaction is highly endothermic, which means that the use of cheap transition metals, such as nickel, is inhibited by metal particle sinter...
Conference Paper
The rapid development of the biodiesel industry, and its forecasted growth, mean that glycerol, the main by-product of the process (10 wt. % of the weight of oil undergoing the transesterification reaction) is fast becoming a considerable waste stream1. However, glycerol may be utilized for the production of hydrogen via steam reforming, as theoret...
Conference Paper
Although the biodiesel industry has grown at a phenomenal 23% per annum during the past decade, its sustainable use is threatened by the production of increasing amounts of the main by-product of the transesterification reaction, i.e., unrefined glycerol (10 wt.% of the oil undergoing the reaction). However, glycerol could also be used for the prod...
Article
The glycerol steam reforming (GSR) reaction for H2 production was studied comparing the performance of Ni supported on ZrO2 and SiO2-ZrO2 catalysts. The surface and bulk properties were determined by ICP, BET, XRD, TPD, TPR, TPO, XPS, SEM and STEM-HAADF. It was suggested that the addition of SiO2 stabilizes the ZrO2 monoclinic structure, restricts...
Conference Paper
As is well understood, humanity’s overreliance on fossil fuels threatens the planet with an ecological catastrophe that is unprecedented in scale. Amongst the most promising renewable energy technologies is the dry reforming of biogas, as in essence, the process makes uses of the main greenhouse gases (CH4 and CO2) and has the potential to have a z...
Conference Paper
The development of biodiesel industry has experienced a tremendous increase in the past decade and a half, with production reaching approximately 32 billion liters in 2015. Biodiesel, currently produced through the transesterification of vegetable oils and/or fats with alcohols, is thought of as a renewable, biodegradable, environmentally-friendly...
Conference Paper
Full-text available
Η διαρκώς αυξανόμενη παραγωγή του βιοντίζελ κατά την διάρκεια των τελευταίων χρόνων έφερε στο προσκήνιο την ανάγκη της ενεργειακής αξιοποίησης της γλυκερόλης η οποία αποτελεί το κύριο παραπροϊόν της αντίδρασης της μετεστεροποίησης. Σαν αποτέλεσμα, η εύρεση νέων εναλλακτικών εφικτών χρήσεων για τη γλυκερόλη θεωρείται επιτακτική, καθώς τέτοιου είδους...
Article
Full-text available
The time-on-stream catalytic performance and stability of 8wt% Ni catalyst supported on two commercially available catalytic supports, ZrO2 and 15wt% WO3-ZrO2, was investigated under the biogas dry reforming reaction for syngas production, at 750oC and a biogas quality equal to CH4/CO2=1.5, that represents a common concentration of real biogas. A n...
Conference Paper
Full-text available
The increase in biodiesel production has resulted in an oversupply of glycerol, which is the main byproduct (10 wt. %); thus, its utilization is fast becoming an economic, as well as, an environmental necessity. In the present work, a comparative study of Ni (8 wt. %) catalysts supported on commercially available Al2O3 and AlCeO3 carriers was under...
Article
The catalytic efficiency and bench scale time on steam stability of Ni dispersed on three commercially available catalytic supports (ZrO2, La2O3-ZrO2 and CeO2-ZrO2) has been studied for the dry reforming of methane (DRM) in the temperature range of 500-800 oC and a CH4/CO2 ratio equal to 1.5, simulating typical biogas quality. Ni supported on LaZr...
Conference Paper
Full-text available
Η αντίδραση της ξηρής αναμόρφωσης του βιοαερίου έχει ως στόχο την παραγωγή υδρογόνου ή/και αερίου σύνθεσης. Περιλαμβάνει την απομάκρυνση, μέσω της μετατροπής τους, αερίων του θερμοκηπίου που περιέχουν άνθρακα, δηλαδή CH4 και CO2, δημιουργώντας παράλληλα προϊόντα προστιθέμενης αξίας [1,2]. Το οξείδιο του αργιλίου ή αλουμίνα (Al2O3) χρησιμοποιείται ε...
Conference Paper
Η γλυκερόλη είναι το κύριο παραπροϊόν της αντίδρασης μετεστεροποίησης εφόσον για κάθε 100gr ελαίου παράγονται 10gr γλυκερόλης ως παραπροϊόν, ενώ η συνεχώς αυξανόμενη ζήτηση σε βιοντίζελ, φέρνει στο προσκήνιο την ανάγκη αξιοποίησής μέσω της ανάπτυξης νέων διεργασιών [1,2]. Η αναμόρφωση της γλυκερόλης με ατμό (Glycerol Steam Reforming) έχει προσελκύσ...
Article
In the present work, a comparative study of Ni catalysts supported on commercially available alumina and lanthana-alumina carriers was undertaken for the glycerol steam reforming reaction (GSR). The supports and/or catalysts were characterized by PZC, BET, ICP, XRD, NH3-TPD, CO2-TPD, TPR and SEM. Carbon deposited on the catalytic surface was charac...
Article
Full-text available
The aim of the work was to investigate the influence of support on the catalytic performance of Ni catalysts for the glycerol steam reforming reaction. Nickel catalysts (8 wt. %) supported on Al2O3, ZrO2, SiO2 were prepared by the wet impregnation technique. The catalysts’ surface and bulk properties, at their calcined, reduced and used forms, were...
Article
Catalysts with active phase Ni, Co or Cu supported on γ- alumina were synthesized at constant loading (8 wt. %) and tested for the glycerol steam reforming reaction (GSR). The synthesized samples, at their calcined and/or their reduced form, were characterized by BET, ICP, XRD, DRS, NH3-TPD, CO2-TPD, TPR and SEM. The carbon deposited on their surfa...
Article
Full-text available
The influence of the synthesis method parameters used to prepare nickel-based catalysts on the catalytic performance for the glycerol steam reforming reaction was studied. A series of Al2O3-supported Ni catalysts were synthesized, with nickel loading of 8 wt. %, using the incipient wetness, wet impregnation, and modified equilibrium deposition filt...
Article
Full-text available
The performance of nickel, cobalt, and copper supported on silica as catalysts was evaluated for the glycerol steam reforming (GSR) reaction. The samples were characterized by nitrogen-porosimetry according to Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), and inductively coupled plasma atomic emission spectroscopy (ICP-AES), while t...
Conference Paper
Conversion of glycerol to hydrogen has been carried out by several techniques, such as aqueous-phase reforming, pyrolysis, supercritical water reforming, steam reforming, partial oxidation reforming, and oxidative steam reforming. Many researchers focused on steam reforming process of pure glycerol which were studied on operating parameters and per...
Conference Paper
In order to have a better control of the biogas reforming reaction’s products and a deeper understanding of the aluminum oxide (Al2O3) modification with various dopants as CeO2 and/or La2O3 mechanism, a systematic study of the Ni/CeAl, Ni/LaAl and Ni/CeLaAl catalysts synthesized via the wet impregnation method at a constant nickel loading (8wt%) wa...
Conference Paper
Full-text available
Raw biogas contains 55–65% methane (CH4), 30–45% carbon dioxide (CO2), traces of hydrogen sulphide (H2S) and fractions of water vapour. Since both methane and carbon dioxide are the main greenhouse gases, the reformation between these two gases is of significance; not only in tackling global warming, but also in providing a renewable fuel as hydrog...
Conference Paper
Full-text available
Hydrogen can be produced from a wide variety of primary energy sources and by applying quite different technologies. For a long period of time it has been considered as a sustainable and environmentally friendly alternative to conventional fossil fuels, with a large potential that can meet energy requirements, ensuring future supplies. At present,...
Conference Paper
Full-text available
(in Greek) Η περιορισμένη φύση των ορυκτών καυσίμων, δημιουργεί την αναγκαιότητα για μεταστροφή του σημερινού ενεργειακού συστήματος σε ένα μακροπρόθεσμα αειφορικό σύστημα, στο οποίο θα πρέπει να ληφθούν υπόψη όλες οι πηγές ενέργειας. Το βιοαέριο (biogas), που αποτελείται κυρίως από μεθάνιο (40-70% κ.ο.) και διοξείδιο του άνθρακα (30-60% κ.ο.), μπο...
Conference Paper
Full-text available
(in Greek) Η εξεύρεση εναλλακτικών εφικτών χρήσεων για την γλυκερόλη θεωρείται επιτακτική ανάγκη καθώς τέτοιου είδους διεργασίες δεν θα επιλύσουν μόνο περιβαλλοντικά προβλήματα που σχετίζονται με την διάθεσή της, αλλά επίσης, η ανακάλυψη νέων και καινοτόμων χρήσεων θα αυξήσει σημαντικά την παγκόσμια ζήτησή της. Ως εκ τούτου, η ανάπτυξη νέων τρόπων...
Book
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Στις μέρες μας, πραγματοποιείται εκτεταμένη μελέτη όσο αναφορά την αντίδραση της ξηρής αναμόρφωσης (DR) του βιοαερίου έχοντας ως στόχο την παραγωγή υδρογόνου ή αερίου σύνθεσης Η παραπάνω αντίδραση περιλαμβάνει τη μετατροπή δύο φθηνών και σε αφθονία πρώτων υλών που περιέχουν άνθρακα δηλαδή του μεθανίου (CH4) και του διοξειδίου του άνθρακα (CO2), σε...
Conference Paper
Full-text available
(in Greek) Εκτεταμένες ερευνητικές προσπάθειες έχουν επικεντρωθεί τις τελευταίες δεκαετίες στη μελέτη της αντίδρασης αναμόρφωσης του βιοαερίου (biogas), έχοντας ως στόχο την παραγωγή υδρογόνου ή/και αερίου σύνθεσης. Η παραπάνω αντίδραση περιλαμβάνει τη μετατροπή δύο φθηνών και σε αφθονία πρώτων υλών που περιέχουν άνθρακα, δηλαδή του μεθανίου (CH4)...

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Projects (2)
Project
Glycerol steam reforming for hydrogen production
Project
Biogas dry reforming for syngas production