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Dr. Michalis Vasiliades
University of Cyprus

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Review
Published: 03 July 2021 in Sustainability
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It is commonly argued that, despite the tremendous resonance Citizen Science (CS) has shown in recent years, there is still lack of understanding of important aspects defining citizens’ participation and engagement in CS initiatives. While CS initiatives could provide a vehicle to foster forms of participation contributing to the democratization of science, there is still limited attention paid to the “Citizen” component of the Citizen Science term. For the purpose of this work, we systematically reviewed the available literature for empirical studies in respect to citizens’ participation in environmental and nature-based CS initiatives established during the last two decades, using the PRISMA methodology. The participatory facet of the retrieved 119 CS initiatives was analysed on the basis of: (a) exclusion and inclusion demographic factors, (b) CS models and practices, (c) facilitators and constraints of citizen’s participation, and (d) environmental citizenship. Our findings show that the majority of the CS initiatives did not place restrictions on gender participation; however, we have identified that mostly highly educated adults participated in the reviewed initiatives. In addition, most of the CS initiatives reported in the literature were situated in the EU and USA, were mostly limited to the local scale, and primarily followed the contributory model. Academic institutions were found to coordinate the majority of the CS initiatives examined. By using digital technologies, academic scientists were able to control and increase data quality, as well as to engage a broader audience, even though they were mostly treating volunteers as “data collectors”, desiring their long-term engagement. Therefore, it will be of CS benefit to be better aligned with the mentality and needs of citizens. In this direction CS initiatives should trigger citizens’ learning gains and interpersonal/social benefits and personal, environmental, and social motivations, but also to shift their goals towards contributing to science and citizens’ connection with nature. On the other hand, there is a need to overcome any design and implementation barriers, and to enhance democratization through a more participative engagement of active and aware citizens, thus promoting environmental citizenship.

ACS Style

Michalis Vasiliades; Andreas Hadjichambis; Demetra Paraskeva-Hadjichambi; Anastasia Adamou; Yiannis Georgiou. A Systematic Literature Review on the Participation Aspects of Environmental and Nature-Based Citizen Science Initiatives. Sustainability 2021, 13, 7457 .

AMA Style

Michalis Vasiliades, Andreas Hadjichambis, Demetra Paraskeva-Hadjichambi, Anastasia Adamou, Yiannis Georgiou. A Systematic Literature Review on the Participation Aspects of Environmental and Nature-Based Citizen Science Initiatives. Sustainability. 2021; 13 (13):7457.

Chicago/Turabian Style

Michalis Vasiliades; Andreas Hadjichambis; Demetra Paraskeva-Hadjichambi; Anastasia Adamou; Yiannis Georgiou. 2021. "A Systematic Literature Review on the Participation Aspects of Environmental and Nature-Based Citizen Science Initiatives." Sustainability 13, no. 13: 7457.

Journal article
Published: 02 July 2021 in Construction and Building Materials
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The carbonation of air lime mortars modified by the addition of 5% and 15% w/w (in partial replacement to lime) quarry waste, rich in Ca-, Mg- and Fe-silicate minerals, is hereby investigated. Ball milling was initially applied to the waste to reduce its particle size to the nanoscale and increase its reactivity towards CO2. The incorporation of the nano-sized waste at 15% w/w resulted in mortars with denser microstructure and higher compressive strength. This is attributed to the enhanced diffusion of atmospheric CO2 through the mortar pore structure and the improved CO2 uptake of the nano-sized waste additive.

ACS Style

Ioannis Rigopoulos; Loucas Kyriakou; Michalis A. Vasiliades; Theodora Kyratsi; Angelos M. Efstathiou; Ioannis Ioannou. Improving the carbonation of air lime mortars at ambient conditions via the incorporation of ball-milled quarry waste. Construction and Building Materials 2021, 301, 124073 .

AMA Style

Ioannis Rigopoulos, Loucas Kyriakou, Michalis A. Vasiliades, Theodora Kyratsi, Angelos M. Efstathiou, Ioannis Ioannou. Improving the carbonation of air lime mortars at ambient conditions via the incorporation of ball-milled quarry waste. Construction and Building Materials. 2021; 301 ():124073.

Chicago/Turabian Style

Ioannis Rigopoulos; Loucas Kyriakou; Michalis A. Vasiliades; Theodora Kyratsi; Angelos M. Efstathiou; Ioannis Ioannou. 2021. "Improving the carbonation of air lime mortars at ambient conditions via the incorporation of ball-milled quarry waste." Construction and Building Materials 301, no. : 124073.

Research article
Published: 09 April 2021 in ACS Applied Materials & Interfaces
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CO elimination through oxidation over highly active and cost-effective catalysts is a way forward for many processes of industrial and environmental importance. In this study, doped CeO2 with transition metals (TM = Cu, Co, Mn, Fe, Ni, Zr, and Zn) at a level of 20 at. % was tested for CO oxidation. The oxides were prepared using microwave-assisted sol–gel synthesis to improve catalyst’s performance for the reaction of interest. The effect of heteroatoms on the physicochemical properties (structure, morphology, porosity, and reducibility) of the binary oxides M–Ce–O was meticulously investigated and correlated to their CO oxidation activity. It was found that the catalytic activity (per gram basis or TOF, s–1) follows the order Cu–Ce–O > Ce–Co–O > Ni–Ce–O > Mn–Ce–O > Fe–Ce–O > Ce–Zn–O > CeO2. Participation of mobile lattice oxygen species in the CO/O2 reaction does occur, the extent of which is heteroatom-dependent. For that, state-of-the-art transient isotopic 18O-labeled experiments involving 16O/18O exchange followed by step-gas CO/Ar or CO/O2/Ar switches were used to quantify the contribution of lattice oxygen to the reaction. SSITKA-DRIFTS studies probed the formation of carbonates while validating the Mars–van Krevelen (MvK) mechanism. Scanning transmission electron microscopy-high-angle annular dark field imaging coupled with energy-dispersive spectroscopy proved that the elemental composition of dopants in the individual nanoparticle of ceria is less than their composition at a larger scale, allowing the assessment of the doping efficacy. Despite the similar structural features of the catalysts, a clear difference in the Olattice mobility was also found as well as its participation (as expressed with the α descriptor) in the reaction, following the order αCu > αCo> αMn > αZn. Kinetic studies showed that it is rather the pre-exponential (entropic) factor and not the lowering of activation energy that justifies the order of activity of the solids. DFT calculations showed that the adsorption of CO on the Cu-doped CeO2 surface is more favorable (−16.63 eV), followed by Co, Mn, Zn (−14.46, −4.90, and −4.24 eV, respectively), and pure CeO2 (−0.63 eV). Also, copper compensates almost three times more charge (0.37e−) compared to Co and Mn, ca. 0.13e− and 0.10e−, respectively, corroborating for its tendency to be reduced. Surface analysis (X-ray photoelectron spectroscopy), apart from the oxidation state of the elements, revealed a heteroatom–ceria surface interaction (Oa species) of different extents and of different populations of Oa species.

ACS Style

Kyriaki Polychronopoulou; Ayesha A. AlKhoori; Angelos M. Efstathiou; Maguy Abi Jaoude; C. M. Damaskinos; Mark A. Baker; Alia Almutawa; Dalaver H. Anjum; Michalis A. Vasiliades; Abderrezak Belabbes; Lourdes F. Vega; Abdallah Fathy Zedan; Steven J. Hinder. Design Aspects of Doped CeO2 for Low-Temperature Catalytic CO Oxidation: Transient Kinetics and DFT Approach. ACS Applied Materials & Interfaces 2021, 13, 22391 -22415.

AMA Style

Kyriaki Polychronopoulou, Ayesha A. AlKhoori, Angelos M. Efstathiou, Maguy Abi Jaoude, C. M. Damaskinos, Mark A. Baker, Alia Almutawa, Dalaver H. Anjum, Michalis A. Vasiliades, Abderrezak Belabbes, Lourdes F. Vega, Abdallah Fathy Zedan, Steven J. Hinder. Design Aspects of Doped CeO2 for Low-Temperature Catalytic CO Oxidation: Transient Kinetics and DFT Approach. ACS Applied Materials & Interfaces. 2021; 13 (19):22391-22415.

Chicago/Turabian Style

Kyriaki Polychronopoulou; Ayesha A. AlKhoori; Angelos M. Efstathiou; Maguy Abi Jaoude; C. M. Damaskinos; Mark A. Baker; Alia Almutawa; Dalaver H. Anjum; Michalis A. Vasiliades; Abderrezak Belabbes; Lourdes F. Vega; Abdallah Fathy Zedan; Steven J. Hinder. 2021. "Design Aspects of Doped CeO2 for Low-Temperature Catalytic CO Oxidation: Transient Kinetics and DFT Approach." ACS Applied Materials & Interfaces 13, no. 19: 22391-22415.

Journal article
Published: 29 May 2020 in Journal of Catalysis
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SSITKA coupled with transient isothermal (TIH) and temperature-programmed hydrogenation (TPH) were used to investigate the influence of Co particle size (dCo = 11–21 nm) and time-on-stream, TOS (up to 25 h) on important kinetic parameters of CO methanation at 230 °C on Co/γ-Al2O3. TOFCO and TOFCH4 were independent of dCo and decreased with TOS. The θCO and θCHx (active CO-s and CHx-s) slightly increased with dCo as opposed to θCxHy (inactive species), which remained practically constant. On the contrary, θCHx and θCxHy largely decreased and increased, respectively, while θCO stayed practically constant with TOS. An inverse D-KIE independent of dCo was estimated by a novel 13CO/D2-SSITKA experiment, reported for the first time to the best of our knowledge. The reason of catalyst deactivation was the decrease of kCHx (hydrogenation of -CHx) likely because of the influence of -CxHy on the bonding of active species and on θH (a decrease was determined).

ACS Style

Klito C. Petallidou; Michalis A. Vasiliades; Angelos M. Efstathiou. Deactivation of Co/γ-Al2O3 in CO methanation studied by transient isotopic experiments: The effect of Co particle size. Journal of Catalysis 2020, 389, 176 -194.

AMA Style

Klito C. Petallidou, Michalis A. Vasiliades, Angelos M. Efstathiou. Deactivation of Co/γ-Al2O3 in CO methanation studied by transient isotopic experiments: The effect of Co particle size. Journal of Catalysis. 2020; 389 ():176-194.

Chicago/Turabian Style

Klito C. Petallidou; Michalis A. Vasiliades; Angelos M. Efstathiou. 2020. "Deactivation of Co/γ-Al2O3 in CO methanation studied by transient isotopic experiments: The effect of Co particle size." Journal of Catalysis 389, no. : 176-194.

Journal article
Published: 29 May 2020 in Applied Catalysis B: Environmental
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A Co0.5Mn1Fe0.25Al0.75Ox-LDO catalyst was developed which showed excellent performance for the low-temperature NH3-SCR. NOx conversions ∼100% were achieved in the whole 100-250 °C range, while after 10-h operation at 150 °C with 100 ppm SO2/5 vol% H2O in the feed, the NOx conversion was maintained at 80%. This catalyst provided a much better N2-selectivity than the Mn1Fe0.25Al0.75Ox-LDO and Mn1Al1Ox-LDO, especially at 150-300 °C. It was found that Co0.5Mn1Fe0.25Al0.75Ox possessed higher surface acidity and reducibility, while XPS analyses indicated an electron transfer between Co3+/Co2+ and Mn4+/Mn3+ redox cycles, leading to a much lower N2O formation, supported by Density Functional Theory (DFT) calculations. Detailed analysis of gas responses obtained upon various step-gas switches was performed, which allowed to measure the surface concentration and reactivity of preadsorbed NOx-s and NHx-s leading to N2 and N2O. Transient kinetic and DFT studies strongly suggested likely mechanisms of NH3-SCR and the critical role of Co for N2-selectivity enhancement.

ACS Style

Sining Chen; Michalis A. Vasiliades; Qinghua Yan; Guangpeng Yang; Xuesen Du; Cheng Zhang; Yuran Li; Tingyu Zhu; Qiang Wang; Angelos M. Efstathiou. Remarkable N2-selectivity enhancement of practical NH3-SCR over Co0.5Mn1Fe0.25Al0.75Ox-LDO: The role of Co investigated by transient kinetic and DFT mechanistic studies. Applied Catalysis B: Environmental 2020, 277, 119186 .

AMA Style

Sining Chen, Michalis A. Vasiliades, Qinghua Yan, Guangpeng Yang, Xuesen Du, Cheng Zhang, Yuran Li, Tingyu Zhu, Qiang Wang, Angelos M. Efstathiou. Remarkable N2-selectivity enhancement of practical NH3-SCR over Co0.5Mn1Fe0.25Al0.75Ox-LDO: The role of Co investigated by transient kinetic and DFT mechanistic studies. Applied Catalysis B: Environmental. 2020; 277 ():119186.

Chicago/Turabian Style

Sining Chen; Michalis A. Vasiliades; Qinghua Yan; Guangpeng Yang; Xuesen Du; Cheng Zhang; Yuran Li; Tingyu Zhu; Qiang Wang; Angelos M. Efstathiou. 2020. "Remarkable N2-selectivity enhancement of practical NH3-SCR over Co0.5Mn1Fe0.25Al0.75Ox-LDO: The role of Co investigated by transient kinetic and DFT mechanistic studies." Applied Catalysis B: Environmental 277, no. : 119186.

Journal article
Published: 22 May 2020 in Catalysts
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A 20 wt% Co-0.05 wt% Pt/γ-Al2O3 catalyst was investigated to obtain a fundamental understanding of the effect of CO partial pressure (constant H2 partial pressure) on important kinetic parameters of the methanation reaction (x vol% CO/25 vol% H2, x = 3, 5 and 7) by performing advanced transient isotopic and operando diffuse reflectance infrared Fourier transform spectroscopy–mass spectrometry (DRIFTS-MS) experiments. Steady State Isotopic Transient Kinetic Analysis (SSITKA) experiments conducted at 1.2 bar, 230 °C after 5 h in CO/H2 revealed that the surface coverages, θCO and θCHx and the mean residence times, τCO, and τCHx (s) of the reversibly adsorbed CO-s and active CHx-s (Cα) intermediates leading to CH4, respectively, increased with increasing CO partial pressure. On the contrary, the apparent activity (keff, s−1) of CHx-s intermediates, turnover frequency (TOF, s−1) of methanation reaction, and the CH4-selectivity (SCH4, %) were found to decrease. Transient isothermal hydrogenation (TIH) following the SSITKA step-gas switch provided important information regarding the reactivity and concentration of active (Cα) and inactive -CxHy (Cβ) carbonaceous species formed after 5 h in the CO/H2 reaction. The latter Cβ species were readily hydrogenated at 230 °C in 50%H2/Ar. The surface coverage of Cβ was found to vary only slightly with increasing CO partial pressure. Temperature-programmed hydrogenation (TPH) following SSITKA and TIH revealed that other types of inactive carbonaceous species (Cγ) were formed during Fischer-Tropsch Synthesis (FTS) and hydrogenated at elevated temperatures (250–550 °C). The amount of Cγ was found to significantly increase with increasing CO partial pressure. All carbonaceous species hydrogenated during TIH and TPH revealed large differences in their kinetics of hydrogenation with respect to the CO partial pressure in the CO/H2 reaction mixture. Operando DRIFTS-MS transient isothermal hydrogenation of adsorbed CO-s formed after 2 h in 5 vol% CO/25 vol% H2/Ar at 200 °C coupled with kinetic modeling (H-assisted CO hydrogenation) provided information regarding the relative reactivity (keff) for CH4 formation of the two kinds of linear-type adsorbed CO-s on the cobalt surface.

ACS Style

Michalis A. Vasiliades; Konstantina K. Kyprianou; Nilenindran S. Govender; Ashriti Govender; Renier Crous; Denzil Moodley; Angelos M. Efstathiou. The Effect of CO Partial Pressure on Important Kinetic Parameters of Methanation Reaction on Co-Based FTS Catalyst Studied by SSITKA-MS and Operando DRIFTS-MS Techniques. Catalysts 2020, 10, 583 .

AMA Style

Michalis A. Vasiliades, Konstantina K. Kyprianou, Nilenindran S. Govender, Ashriti Govender, Renier Crous, Denzil Moodley, Angelos M. Efstathiou. The Effect of CO Partial Pressure on Important Kinetic Parameters of Methanation Reaction on Co-Based FTS Catalyst Studied by SSITKA-MS and Operando DRIFTS-MS Techniques. Catalysts. 2020; 10 (5):583.

Chicago/Turabian Style

Michalis A. Vasiliades; Konstantina K. Kyprianou; Nilenindran S. Govender; Ashriti Govender; Renier Crous; Denzil Moodley; Angelos M. Efstathiou. 2020. "The Effect of CO Partial Pressure on Important Kinetic Parameters of Methanation Reaction on Co-Based FTS Catalyst Studied by SSITKA-MS and Operando DRIFTS-MS Techniques." Catalysts 10, no. 5: 583.

Journal article
Published: 01 October 2019 in Journal of Catalysis
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Two commercial Co-based catalysts supported on carbon-coated and uncoated γ-Al2O3 (during Co deposition) of different Co particle size (∼7 and 10 nm) and surface structure were investigated to address the effect of preparation route on important kinetic parameters of the methanation reaction (5 vol% CO, H2/CO = 2, P = 1.1 bar) by advanced transient isotopic and operando DRIFTS experiments. 13CO-SSITKA-Mass Spectrometry experiments performed at 230 °C and after 32 h on TOS, showed that the surface coverage (θCO) and mean residence time (τCO, s) of reversibly adsorbed CO-s are not influenced by the different preparation route, while θCHx, TOFCH4 (s−1) and the τCHx (s) related to the active carbonaceous species were slightly increased with increasing Co particle size (in the 7–10 nm range). On the other hand, the kinetic rates of CO conversion and CH4 production (μmol g−1 s−1) were found to increase with decreasing Co particle size. The TOFCH4,ITK (s−1) estimated on the basis of the measured active CHx-s and CO-s species was found very similar for the two Co particle sizes. The effective rate constant of hydrogenation of CHx-s (keff, s−1) after short time on stream (1 h) was found to increase with increasing Co particle size as the result of the different preparation route applied. Transient isothermal hydrogenation (TIH) experiments following the 13CO-SSITKA-MS gas switch measured the concentration of inactive CHx (Cβ) species formed after 32 h of reaction and which were found to be readily hydrogenated at 230 °C. Temperature-programmed hydrogenation (TPH) experiments estimated the concentration of other types of inactive carbonaceous species (Cγ), which were hydrogenated at elevated temperatures (250–600 °C). The amounts of Cβ and Cγ species were found to significantly increase with increasing Co particle size, and their kinetics of hydrogenation was dependent of Co particle size. These results provided evidence for the lower deactivation rate observed under industrial FTS conditions over the Co/γ-Al2O3 (carbon-coated) catalyst. Operando SSITKA-MS-DRIFTS studies followed by transient isothermal hydrogenation coupled with kinetic modeling highlighted the influence of Co particle size on the relative reactivity (keff) of two different types of adsorbed CO-s towards hydrogen. Catalyst characterization was performed by HAADF-STEM, H2-TPR and transient hydrogen chemisorption at 100 °C followed by TPD.

ACS Style

M.A. Vasiliades; C.M. Kalamaras; N.S. Govender; A. Govender; A.M. Efstathiou. The effect of preparation route of commercial Co/γ-Al2O3 catalyst on important Fischer-Tropsch kinetic parameters studied by SSITKA and CO-DRIFTS transient hydrogenation techniques. Journal of Catalysis 2019, 379, 60 -77.

AMA Style

M.A. Vasiliades, C.M. Kalamaras, N.S. Govender, A. Govender, A.M. Efstathiou. The effect of preparation route of commercial Co/γ-Al2O3 catalyst on important Fischer-Tropsch kinetic parameters studied by SSITKA and CO-DRIFTS transient hydrogenation techniques. Journal of Catalysis. 2019; 379 ():60-77.

Chicago/Turabian Style

M.A. Vasiliades; C.M. Kalamaras; N.S. Govender; A. Govender; A.M. Efstathiou. 2019. "The effect of preparation route of commercial Co/γ-Al2O3 catalyst on important Fischer-Tropsch kinetic parameters studied by SSITKA and CO-DRIFTS transient hydrogenation techniques." Journal of Catalysis 379, no. : 60-77.

Journal article
Published: 06 September 2019 in Journal of Environmental Management
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The emerging need for sustainable management of the increasing quantities of urban and industrial organic wastes creates opportunities for the development of alternative strategies for the improvement of degraded soils. The current study was performed to examine the effects of agricultural wastes application on soil bacterial community as well as CO2 and N2O direct gas emissions. Untreated soils were compared with soils, which received the same amount of N (100 μg/g soil) in the form of ammonium nitrate and organic agricultural waste. In particular, soils were incubated with three different organic agricultural wastes, orange (OP), mandarin (MP) and banana peels (BP) and ammonium nitrate (F) after adjusting soil water at 70% of its holding capacity. In the current study, soil chemical characteristics, quantitative PCR of denitrifiers (nirK, nirS, nosZI and nosZII) and16s rRNA amplicon sequencing were assessed to examine the links between the soil microbial communities and short-term soil direct N2O emissions when treated with agricultural wastes. The highest soil direct N2O emissions were recorded in soils received ammonium nitrate while soils received agricultural wastes exhibited substantially lower soil direct N2O emissions. On the contrary, agricultural wastes stimulated CO2 accumulation as well as the growth of copiotrophic bacterial groups like Proteobacteria and Firmicutes. Interestingly, direct soil N2O emissions were decoupled from the density of denitrifier community while agricultural wastes caused a substantial reduction of the relative abundance of bacterial taxa associated with N2O emissions in the soil. This study proves evidence that agricultural wastes could be integrated in a waste management strategy, which inter alia includes their direct use in agricultural ecosystems resulting in reduced N2O emissions.

ACS Style

Ioannis Anastopoulos; Michalis Omirou; Coralea Stephanou; Anastasios Oulas; Michalis A. Vasiliades; Angelos M. Efstathiou; Ioannis M. Ioannides. Valorization of agricultural wastes could improve soil fertility and mitigate soil direct N2O emissions. Journal of Environmental Management 2019, 250, 109389 .

AMA Style

Ioannis Anastopoulos, Michalis Omirou, Coralea Stephanou, Anastasios Oulas, Michalis A. Vasiliades, Angelos M. Efstathiou, Ioannis M. Ioannides. Valorization of agricultural wastes could improve soil fertility and mitigate soil direct N2O emissions. Journal of Environmental Management. 2019; 250 ():109389.

Chicago/Turabian Style

Ioannis Anastopoulos; Michalis Omirou; Coralea Stephanou; Anastasios Oulas; Michalis A. Vasiliades; Angelos M. Efstathiou; Ioannis M. Ioannides. 2019. "Valorization of agricultural wastes could improve soil fertility and mitigate soil direct N2O emissions." Journal of Environmental Management 250, no. : 109389.

Journal article
Published: 21 July 2019 in Catalysts
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The present work discusses the effect of CeO2 synthesis method (thermal decomposition (TD), precipitation (PT), hydrothermal (HT), and sol-gel (SG)) on the carbon pathways of dry reforming of methane with carbon dioxide (DRM) applied at 750 °C over 5 wt% Ni/CeO2. In particular, specific transient and isotopic experiments (use of 13CO, 13CO2, and 18O2) were designed and conducted in an attempt at providing insights about the effect of support’s preparation method on the concentration (mg gcat−1), reactivity towards oxygen, and transient evolution rates (μmol gcat−1 s−1) of the inactive carbon formed under (i) CH4/He (methane decomposition), (ii) CO/He (reverse Boudouard reaction), and (iii) the copresence of the two (CH4/CO/He, use of 13CO). Moreover, important information regarding the relative contribution of CH4 and CO2 activation routes towards carbon formation under DRM reaction conditions was derived by using isotopically labelled 13CO2 in the feed gas stream. Of interest was also the amount, and the transient rate, of carbon removal via the participation of support’s labile active oxygen species.

ACS Style

Constantinos M. Damaskinos; Michalis A. Vasiliades; Vassilis N. Stathopoulos; Angelos M. Efstathiou. The Effect of CeO2 Preparation Method on the Carbon Pathways in the Dry Reforming of Methane on Ni/CeO2 Studied by Transient Techniques. Catalysts 2019, 9, 621 .

AMA Style

Constantinos M. Damaskinos, Michalis A. Vasiliades, Vassilis N. Stathopoulos, Angelos M. Efstathiou. The Effect of CeO2 Preparation Method on the Carbon Pathways in the Dry Reforming of Methane on Ni/CeO2 Studied by Transient Techniques. Catalysts. 2019; 9 (7):621.

Chicago/Turabian Style

Constantinos M. Damaskinos; Michalis A. Vasiliades; Vassilis N. Stathopoulos; Angelos M. Efstathiou. 2019. "The Effect of CeO2 Preparation Method on the Carbon Pathways in the Dry Reforming of Methane on Ni/CeO2 Studied by Transient Techniques." Catalysts 9, no. 7: 621.

Journal article
Published: 15 May 2019 in Applied Catalysis B: Environmental
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There are very few catalysts reported so far to withstand poisoning by the co-presence of SO2, HCl and H2O in the flue gas stream for the NH3-SCR. The purpose of this work was to report for the first time, to the best of our knowledge, the development of a new catalyst, Ce2/Cu4Al1Ox-layered double oxide (LDO) with high low-temperature de-NOx activity and high poisoning resistance in the presence of H2O, HCl and SO2 in the feed gas stream. In particular, Ce2/Cu4Al1Ox-LDO catalyst in the presence of 5% H2O, 100 ppm HCl and 100 ppm SO2 in the NH3-SCR feed gas stream presented after 9 h of continuous reaction at 200 °C a relatively stable NOx conversion (ca. 57.2%), where all other three control catalysts tested, namely: Cu/Al2O3, Cu-Ce/Al2O3 and Cu4Al1Ox showed severe deactivation, where NOx conversion values of ˜ 0, 0 and 5.7%, respectively, were measured. It should be noted that the Ce2/Cu4Al1Ox catalyst achieved NOx conversion of 95.3% at 200 °C in the absence of HCl and SO2 in the feed gas stream. A suit of experimental techniques such as BET, XPS, ICS, in situ DRIFTS, pyridine- and NH3-FTIR, NH3-TPD, H2-TPR and transient NH3 chemisorption and NH3-SCR kinetics were employed to reveal possible reasons for the high activity and poisoning resistance exhibited by the Ce2/Cu4Al1Ox catalytic system. XRD and XPS analyses showed that Ce2/Cu4Al1Ox had highly dispersed Cu2+ and Ce3+ species, which likely promote the rate of NH3-SCR. Py-FTIR, NH3-TPD and H2-TPR results indicated that Ce2/Cu4Al1Ox has a larger concentration of surface acid sites and stronger redox properties. According to H2-TPR, ICS and in-situ DRIFTS analyses, the redox properties of Ce2/Cu4Al1Ox were significantly less affected by the presence of HCl and SO2 gases, and lower amounts of metal sulfate and metal chloride species were formed, thus proving its exhibited poisoning resistance. Transient kinetics experiments revealed that the larger site reactivity (k, s-1) and NO oxidation rate to NO2 and not the surface coverage of adsorbed NHx-s active intermediates dictates the higher rate of NH3-SCR over Ce2/Cu4Al1Ox compared to Cu/Al2O3 and Cu-Ce/Al2O3 non LDO- materials.

ACS Style

Qinghua Yan; Yanshan Gao; Yuran Li; Michalis A. Vasiliades; Sining Chen; Cheng Zhang; Rongrong Gui; Qiang Wang; Tingyu Zhu; Angelos M. Efstathiou. Promotional effect of Ce doping in Cu4Al1Ox – LDO catalyst for low-T practical NH3-SCR: Steady-state and transient kinetics studies. Applied Catalysis B: Environmental 2019, 255, 1 .

AMA Style

Qinghua Yan, Yanshan Gao, Yuran Li, Michalis A. Vasiliades, Sining Chen, Cheng Zhang, Rongrong Gui, Qiang Wang, Tingyu Zhu, Angelos M. Efstathiou. Promotional effect of Ce doping in Cu4Al1Ox – LDO catalyst for low-T practical NH3-SCR: Steady-state and transient kinetics studies. Applied Catalysis B: Environmental. 2019; 255 ():1.

Chicago/Turabian Style

Qinghua Yan; Yanshan Gao; Yuran Li; Michalis A. Vasiliades; Sining Chen; Cheng Zhang; Rongrong Gui; Qiang Wang; Tingyu Zhu; Angelos M. Efstathiou. 2019. "Promotional effect of Ce doping in Cu4Al1Ox – LDO catalyst for low-T practical NH3-SCR: Steady-state and transient kinetics studies." Applied Catalysis B: Environmental 255, no. : 1.

Journal article
Published: 19 April 2019 in Applied Catalysis A: General
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The carbon pathways in the dry reforming of methane with carbon dioxide (DRM) towards syngas at 750 °C have been investigated for the first time over 5 wt% Ni supported on Ti4+-doped ceria using various transient and isotopic experiments. The obtained results revealed important information about the effect of Ce1-xTixO2-δ support chemical composition (x = 0, 0.2 and 0.5) on the transient rates of “carbon” deposition via CH4/He (methane decomposition) and CO/He (Boudouard reaction), and on the rate of “carbon” removal via the participation of labile active oxygen of support under DRM reaction conditions. The alternative path of CO2 activation on the oxygen vacant sites of support was also probed by transient isothermal reduction (use of hydrogen) at 750 °C followed by transient CO2/He reaction. Quantification of the amount (mg C g-1cat) of inactive “carbon” accumulated as a function of time on stream in DRM and support chemical composition as well as of the origin of it (CH4 vs CO2 activation route), was made after conducting temperature-programmed oxidation (TPO) experiments coupled with the use of 13CO2. It was illustrated that 5 wt% Ni (dNi ˜ 20 nm) supported on Ce0.8Ti0.2O2-δ solid solution improves the H2-yield and H2/CO product gas ratio compared to 5 wt% Ni/CeO2 of similar Ni mean particle size but remarkably caused a drastic reduction in the rate of “carbon” deposition. After 12 h of DRM (20% CH4, CH4/CO2 = 1), Ni/Ce0.8Ti0.2O2-δ accumulates ˜ 270 times less “carbon” the origin of which was the CH4 activation and not the CO disproportionation route. The 5 wt% Ni/Ce0.8Ti0.2O2 catalyst developed presented high CH4 and CO2 conversions (75% and 82 %), a H2-yiled of 64% and an H2/CO product gas ratio of 1.3 after 100 h of DRM at 750 °C (40%CH4/40%CO2/He; GHSV = 30,000 h-1) with a relatively low amount (73 mg “C” gcat-1 or 7.3 wt%) of inactive “carbon”, which is considered to the best of our knowledge, as one of the lowest values reported in the literature for monometallic Ni supported catalysts under the examined DRM reaction conditions.

ACS Style

C.M. Damaskinos; M.A. Vasiliades; A.M. Efstathiou. The effect of Ti4+ dopant in the 5 wt% Ni/Ce1-xTixO2- catalyst on the carbon pathways of dry reforming of methane studied by various transient and isotopic techniques. Applied Catalysis A: General 2019, 579, 116 -129.

AMA Style

C.M. Damaskinos, M.A. Vasiliades, A.M. Efstathiou. The effect of Ti4+ dopant in the 5 wt% Ni/Ce1-xTixO2- catalyst on the carbon pathways of dry reforming of methane studied by various transient and isotopic techniques. Applied Catalysis A: General. 2019; 579 ():116-129.

Chicago/Turabian Style

C.M. Damaskinos; M.A. Vasiliades; A.M. Efstathiou. 2019. "The effect of Ti4+ dopant in the 5 wt% Ni/Ce1-xTixO2- catalyst on the carbon pathways of dry reforming of methane studied by various transient and isotopic techniques." Applied Catalysis A: General 579, no. : 116-129.

Review article
Published: 08 April 2019 in Catalysis Today
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The present work extensively discusses the carbon pathways in the dry reforming of methane with carbon dioxide (DRM) at 750 °C towards syngas (CO/H2 ˜ 1) over 5 wt% Ni, 0.5 wt% Pt and their bimetallic alloy (5 wt% Ni-0.5 wt% Pt) supported on the reducible Ce0.8Pr0.2O2-δ carrier for the first time. Various transient and isotopic experiments (use of 13CO2 and 18O2) were designed and performed aiming at providing important information about the effect of insertion of Pt in the Ni/Ce0.8Pr0.2O2-δ solid (one pot wet impregnation) on the amounts (mg gcat-1) and transient rates (μmol gcat-1 s-1) of “carbon” formation via CH4/He (methane decomposition), CO/He (reverse Boudouard reaction) and the combination of the two (CH4/CO/He). Also, the effect of Pt on the amount and transient rate of “carbon” removal via the participation of support’s mobile active oxygen species during DRM was probed. Hydrogen reduction of the Ce0.8Pr0.2O2-δ support alone at 750 °C followed by transient isothermal CO2/He treatment (750 °C) probed the existence of an alternative path of CO2 activation in the presence of support’s oxygen vacant sites. The quantification of the origin of “carbon” in the DRM (CH4 vs CO2 activation route) was performed after using isotopically labelled 13CO2 in the feed gas stream. It was found that “carbon” deposition on supported Ni and Ni-Pt alloy was largely due to the CH4 activation route on the metal surface, whereas for the supported Pt, both activation routes applied. Temperature-programmed oxidation (TPO) was used to estimate the amount and reactivity of the “carbon” deposited as a function of time-on-stream in CH4/He, CO/He, CH4/CO/He and DRM reactions. It was found that even though supported bimetallic Ni-Pt provided a small drop in CH4-conversion compared to the supported monometallic Ni catalyst, a remarkable decrease in the rate of “carbon” accumulation was obtained for the former catalyst. The latter was ˜ 32 times lower after 12 h in DRM (20%CH4, CO2/CH4 = 1) at 750 °C. This is largely due to the reduced rate of “carbon” deposition (via CH4 decomposition) and the enhanced rate of its gasification by lattice oxygen. The supported bimetallic Ni-Pt catalyst presented overall an excellent performance and stability after 50 h in DRM at 750 °C with a low amount of accumulated “carbon” (0.38 wt%), which is considered, to our knowledge, as one of the lowest values reported so far for bimetallic Ni-based supported catalysts.

ACS Style

M.A. Vasiliades; Constantinos Damaskinos; Konstantina Kyprianou; M. Kollia; A.M. Efstathiou. The effect of Pt on the carbon pathways in the dry reforming of methane over Ni-Pt/Ce0.8Pr0.2O2-δ catalyst. Catalysis Today 2019, 355, 788 -803.

AMA Style

M.A. Vasiliades, Constantinos Damaskinos, Konstantina Kyprianou, M. Kollia, A.M. Efstathiou. The effect of Pt on the carbon pathways in the dry reforming of methane over Ni-Pt/Ce0.8Pr0.2O2-δ catalyst. Catalysis Today. 2019; 355 ():788-803.

Chicago/Turabian Style

M.A. Vasiliades; Constantinos Damaskinos; Konstantina Kyprianou; M. Kollia; A.M. Efstathiou. 2019. "The effect of Pt on the carbon pathways in the dry reforming of methane over Ni-Pt/Ce0.8Pr0.2O2-δ catalyst." Catalysis Today 355, no. : 788-803.

Original paper
Published: 07 December 2018 in Topics in Catalysis
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A novel methodology for the analysis of 18O2-transient isothermal isotopic exchange (TIIE) response curves obtained over commercial mixed metal oxides upon the gas switch 16O2/Ar (30 min) → 18O2/Kr/Ar (t) at constant T in a flow CSTR micro-reactor in the absence of external and internal mass transport resistances and grain boundary effects, is presented for the first time. The specific aim of this analysis was to derive quantitative descriptors of the 16O/18O exchange under pseudo-equilibrium conditions for the transfer rates of oxygen between the gas and solid phases, enabling the assessment of differences in the kinetics of bulk oxygen diffusion over a series of commercial OSC materials used in various catalytic applications (e.g. TWC), without the need of performing any mathematical and kinetic modelling of the surface/bulk oxygen diffusion processes. Based on these descriptors, commercial OSC mixed metal oxides prepared by the same chemical synthesis route but varying the value of one of the synthesis parameters, and having the same at.% composition, were proved to possess largely different transient kinetic rates and other features of the transient response curves of 16O/18O exchange strongly related to the bulk oxygen diffusion in the solids. This novel 18O2-TIIE analysis is quick and provides a reliable means for proving or disproving likely infringement of patented commercial mixed metal oxides OSC materials.

ACS Style

Michalis Vasiliades; Deb Harris; Hazel Stephenson; Soghomon Boghosian; Angelos M. Efstathiou. A Novel Analysis of Transient Isothermal 18O Isotopic Exchange on Commercial CexZr1−xO2-Based OSC Materials. Topics in Catalysis 2018, 62, 219 -226.

AMA Style

Michalis Vasiliades, Deb Harris, Hazel Stephenson, Soghomon Boghosian, Angelos M. Efstathiou. A Novel Analysis of Transient Isothermal 18O Isotopic Exchange on Commercial CexZr1−xO2-Based OSC Materials. Topics in Catalysis. 2018; 62 (1-4):219-226.

Chicago/Turabian Style

Michalis Vasiliades; Deb Harris; Hazel Stephenson; Soghomon Boghosian; Angelos M. Efstathiou. 2018. "A Novel Analysis of Transient Isothermal 18O Isotopic Exchange on Commercial CexZr1−xO2-Based OSC Materials." Topics in Catalysis 62, no. 1-4: 219-226.

Journal article
Published: 01 January 2018 in Catalysis Today
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ACS Style

M.A. Vasiliades; P. Djinović; L.F. Davlyatova; A. Pintar; Angelos Efstathiou. Origin and reactivity of active and inactive carbon formed during DRM over Ni/Ce0.38Zr0.62O2-δ studied by transient isotopic techniques. Catalysis Today 2018, 299, 201 -211.

AMA Style

M.A. Vasiliades, P. Djinović, L.F. Davlyatova, A. Pintar, Angelos Efstathiou. Origin and reactivity of active and inactive carbon formed during DRM over Ni/Ce0.38Zr0.62O2-δ studied by transient isotopic techniques. Catalysis Today. 2018; 299 ():201-211.

Chicago/Turabian Style

M.A. Vasiliades; P. Djinović; L.F. Davlyatova; A. Pintar; Angelos Efstathiou. 2018. "Origin and reactivity of active and inactive carbon formed during DRM over Ni/Ce0.38Zr0.62O2-δ studied by transient isotopic techniques." Catalysis Today 299, no. : 201-211.

Journals
Published: 17 August 2017 in Catalysis Science & Technology
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The kinetic rate of inactive and active carbon formation in DRM over CeZrO2-supported NiCo alloy particles depends on the support's oxygen mobility.

ACS Style

Michalis A. Vasiliades; Petar Djinović; Albin Pintar; Janez Kovač; Angelos M. Efstathiou. The effect of CeO2–ZrO2 structural differences on the origin and reactivity of carbon formed during methane dry reforming over NiCo/CeO2–ZrO2 catalysts studied by transient techniques. Catalysis Science & Technology 2017, 7, 5422 -5434.

AMA Style

Michalis A. Vasiliades, Petar Djinović, Albin Pintar, Janez Kovač, Angelos M. Efstathiou. The effect of CeO2–ZrO2 structural differences on the origin and reactivity of carbon formed during methane dry reforming over NiCo/CeO2–ZrO2 catalysts studied by transient techniques. Catalysis Science & Technology. 2017; 7 (22):5422-5434.

Chicago/Turabian Style

Michalis A. Vasiliades; Petar Djinović; Albin Pintar; Janez Kovač; Angelos M. Efstathiou. 2017. "The effect of CeO2–ZrO2 structural differences on the origin and reactivity of carbon formed during methane dry reforming over NiCo/CeO2–ZrO2 catalysts studied by transient techniques." Catalysis Science & Technology 7, no. 22: 5422-5434.

Journal article
Published: 01 December 2016 in Journal of CO2 Utilization
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ACS Style

Ioannis Rigopoulos; Klito C. Petallidou; Michalis A. Vasiliades; Andreas Delimitis; Ioannis Ioannou; Angelos M. Efstathiou; Theodora Kyratsi. On the potential use of quarry waste material for CO2 sequestration. Journal of CO2 Utilization 2016, 16, 361 -370.

AMA Style

Ioannis Rigopoulos, Klito C. Petallidou, Michalis A. Vasiliades, Andreas Delimitis, Ioannis Ioannou, Angelos M. Efstathiou, Theodora Kyratsi. On the potential use of quarry waste material for CO2 sequestration. Journal of CO2 Utilization. 2016; 16 ():361-370.

Chicago/Turabian Style

Ioannis Rigopoulos; Klito C. Petallidou; Michalis A. Vasiliades; Andreas Delimitis; Ioannis Ioannou; Angelos M. Efstathiou; Theodora Kyratsi. 2016. "On the potential use of quarry waste material for CO2 sequestration." Journal of CO2 Utilization 16, no. : 361-370.

Journal article
Published: 08 March 2016 in Applied Catalysis B: Environmental
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The effects of Ce1-xPrxO2-δ support composition (x = 0.0–0.8) and reaction temperature (550–750 °C) on the catalytic activity and selectivity and important features of the mechanism of the dry reforming of methane (DRM) over supported Ni (5 wt%) were investigated. Of particular interest were the effects on the concentration of active and inactive carbon formed, the relative contribution of CH4 and CO2 activation routes towards carbon formation and the structure and morphology of the inactive carbon which was formed. For these carbon characterization studies, steady-state isotopic transient kinetic analysis (13CO2-SSITKA), temperature-programmed oxidation (TPO) following 13CO2/12CH4/He dry reforming, thermal gravimetric analysis coupled with TPO (TGA-TPO), scanning electron miscroscopy (SEM-EDX) and transmission electron microscopy with atomic resolution (HRTEM) and powder X-ray diffraction (XRD) were employed. The relative amount of inactive carbon formed via the CH4 and CO2 activation routes was found to strongly depend on reaction temperature and Pr-dopant support composition. At 550 °C, the contribution of the CO2 activation route to the inactive carbon formation (besides that of the CH4 activation route) was 65.7 and 60.1%, respectively, for Ni supported on CeO2 and Ce0.2Pr0.8O2 carriers, whereas at 750 °C the respective values were 54.0 and 50.9%. Filamentous carbon and thin layers of graphitic carbon were identified as the main morphologies of inactive carbon. The surface coverage of active carbon that truly participates in the formation of CO was found to depend on support composition and reaction temperature (θC = 0.03–0.15 at 550 °C and 0.07–3.4 at 750 °C). A pool of inactive reversibly adsorbed CO2 was measured (θ = 1.5–4.1) for the first time, which was dependent on support composition and reaction T. The introduction of 20 atom-% Pr in the ceria lattice caused a significant reduction in the rate of inactive carbon formation with marginal decrease in catalyst’s activity and stability after 25 h on stream. Further introduction of Pr-dopant (80 atom-%) caused drastic reduction in the deposited carbon after 25 h on the reaction stream at 750 °C (0.07 wt% C) but with appreciable decrease in CH4- and CO2-conversions and H2/CO gas-product ratio (a drop by a factor of 1.85, 1.45 and 1.47, respectively). The latter decrease in catalyst’s performance is correlated with the increase in the pool of inactive adsorbed CO2 in the form of carbonate-like species.

ACS Style

M.A. Vasiliades; M.M. Makri; P. Djinović; B. Erjavec; A. Pintar; A.M. Efstathiou. Dry reforming of methane over 5 wt% Ni/Ce1-xPrxO2-δ catalysts: Performance and characterisation of active and inactive carbon by transient isotopic techniques. Applied Catalysis B: Environmental 2016, 197, 168 -183.

AMA Style

M.A. Vasiliades, M.M. Makri, P. Djinović, B. Erjavec, A. Pintar, A.M. Efstathiou. Dry reforming of methane over 5 wt% Ni/Ce1-xPrxO2-δ catalysts: Performance and characterisation of active and inactive carbon by transient isotopic techniques. Applied Catalysis B: Environmental. 2016; 197 ():168-183.

Chicago/Turabian Style

M.A. Vasiliades; M.M. Makri; P. Djinović; B. Erjavec; A. Pintar; A.M. Efstathiou. 2016. "Dry reforming of methane over 5 wt% Ni/Ce1-xPrxO2-δ catalysts: Performance and characterisation of active and inactive carbon by transient isotopic techniques." Applied Catalysis B: Environmental 197, no. : 168-183.

Journal article
Published: 01 March 2016 in Advanced Powder Technology
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The investigation of potential options for CO2 sequestration is of vital importance for alleviating the ongoing climate problem. This paper presents an efficient method for enhancing the ex situ carbonation of dunites. The ball milling process was applied to a dunite from the Troodos ophiolite (Cyprus), in order to create a new type of material with enhanced CO2 uptake. Through CO2 chemisorption followed by temperature-programmed desorption (CO2-TPD) experiments, optimum ball milling conditions were found (12 h of wet ball milling with 50 wt% ethanol as process control agent), leading to an increase of CO2 uptake of dunite by a factor of 6.9. A further increase of CO2 uptake by 10% was accomplished after 4 h of additional ball milling with smaller balls. Additionally, CO2-TPD along with in situ DRIFTS studies indicated that the CO2 uptake of the dunitic materials can be substantially enhanced by the presence of H2O during CO2 chemisorption. The positive effect of H2O on CO2 chemisorption becomes much more evident after the ball milling process. Specifically, the CO2 uptake of the ball-milled sample (BM45) was enhanced by a factor of 5.8 (from 181.9 to 1047.5 μmol g−1), when CO2 chemisorption was performed in the presence of 20 vol% H2O.

ACS Style

Ioannis Rigopoulos; Michalis A. Vasiliades; Ioannis Ioannou; Angelos M. Efstathiou; Athanasios Godelitsas; Theodora Kyratsi. Enhancing the rate of ex situ mineral carbonation in dunites via ball milling. Advanced Powder Technology 2016, 27, 360 -371.

AMA Style

Ioannis Rigopoulos, Michalis A. Vasiliades, Ioannis Ioannou, Angelos M. Efstathiou, Athanasios Godelitsas, Theodora Kyratsi. Enhancing the rate of ex situ mineral carbonation in dunites via ball milling. Advanced Powder Technology. 2016; 27 (2):360-371.

Chicago/Turabian Style

Ioannis Rigopoulos; Michalis A. Vasiliades; Ioannis Ioannou; Angelos M. Efstathiou; Athanasios Godelitsas; Theodora Kyratsi. 2016. "Enhancing the rate of ex situ mineral carbonation in dunites via ball milling." Advanced Powder Technology 27, no. 2: 360-371.

Journal article
Published: 22 January 2016 in Applied Catalysis B: Environmental
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The impact of CeO2 in the Al2O3-20 wt% CeO2 support prepared by the co-precipitation method on the Ir particle size, morphology and oxidation state, and in turn on the deN2O catalytic activity (1000 ppm N2O) of supported Ir catalysts were investigated in the absence and presence of excess O2 (2 vol%) conditions. It was demonstrated that the deN2O activity of Ir/Al2O3 is notably suppressed by the presence of oxygen in the feed stream, namely, the N2O conversion at 600 °C is declined to 65% in the presence of oxygen as compared to 100% in the absence of oxygen. A similar detrimental catalytic effect was also observed for the Ir/CeO2 solid. On the contrary, the deN2O performance of CeO2-modified Ir/Al2O3 catalyst is only slightly affected by the presence of oxygen. An extensive characterization study involving surface texture analysis (N2 adsorption-desorption at −196 °C), temperature-programmed reduction in H2 (H2-TPR), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption and desorption (CO-DRIFTS) was carried out to gain insight into the origin of the CeO2-induced promotional effect. The characterization results revealed the existence of IrO2 phase (H2-TPR, XRD, HRTEM, EELS and CO-DRIFTS) as well as of very small isolated particles of Ir on the Al2O3, CeO2 and CeO2-Al2O3 supports (STEM) but to a notably different extent. The coexistence of large IrO2 particles of perfect crystallite structure and very small Ir particles located at the Ir-ceria interface was revealed only in Ir/AlCe. The establishment of a certain Irδ+/Ιr0 ratio and oxygen vacant sites (VO) concentration in ceria around very small Ir particles under oxidative reaction conditions seem to largely promote N2O adsorption and subsequent decomposition into N2 and O2 over the CeO2-promoted Ir/Al catalyst. In the case of Ir/Al, a different deN2O decomposition mechanism occurs, where the site reactivity of Irδ+/Ιr0 established under oxidizing conditions is reduced significantly.

ACS Style

E. Pachatouridou; E. Papista; A. Delimitis; M.A. Vasiliades; A.M. Efstathiou; M.D. Amiridis; O.S. Alexeev; D. Bloom; G.E. Marnellos; M. Konsolakis; E. Iliopoulou. N 2 O decomposition over ceria-promoted Ir/Al 2 O 3 catalysts: The role of ceria. Applied Catalysis B: Environmental 2016, 187, 259 -268.

AMA Style

E. Pachatouridou, E. Papista, A. Delimitis, M.A. Vasiliades, A.M. Efstathiou, M.D. Amiridis, O.S. Alexeev, D. Bloom, G.E. Marnellos, M. Konsolakis, E. Iliopoulou. N 2 O decomposition over ceria-promoted Ir/Al 2 O 3 catalysts: The role of ceria. Applied Catalysis B: Environmental. 2016; 187 ():259-268.

Chicago/Turabian Style

E. Pachatouridou; E. Papista; A. Delimitis; M.A. Vasiliades; A.M. Efstathiou; M.D. Amiridis; O.S. Alexeev; D. Bloom; G.E. Marnellos; M. Konsolakis; E. Iliopoulou. 2016. "N 2 O decomposition over ceria-promoted Ir/Al 2 O 3 catalysts: The role of ceria." Applied Catalysis B: Environmental 187, no. : 259-268.

Journal article
Published: 10 July 2015 in Catalysis Today
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Carbon dioxide reforming of methane to synthesis gas in the 550–750 °C range over 5 wt% Ni/Ce1−xMxO2−δ (M = Zr4+, Pr3+) solids has been investigated with respect to the effects of support chemical composition and reaction temperature on the amount, reactivity (towards H2 and O2) and relative contribution of CH4 and CO2 activation routes towards “carbon” formation. For these “carbon” characterisation studies, various transient isothermal and temperature-programmed oxidation (TPO) and hydrogenation (TPH) experiments coupled with the use of 13CO and 13CO2 isotope gases were conducted. TPO following dry reforming (5%13CO2/5%12CH4/45%Ar/45%He) demonstrated that the relative amount of the various kinds of “carbon” formed via the CH4 and CO2 activation routes was strongly dependent on reaction temperature and support chemical composition. At 550 °C, the ratio of 12CO2 to 13CO2 of the 12C-containing and 13C-containing inactive “carbon” formed was 0.4, 0.27 and 0.19, whereas at 750 °C was 1.07, 1.06 and 0.29, respectively, for the 5 wt% Ni supported on Ce0.8Zr0.2O2, Ce0.8Pr0.2O2 and Ce0.5Zr0.5O2 carriers. The origin of “carbon” formation via the CO2 activation route was illustrated to be the Boudouard reaction (2CO-s → CO2(g) + C-s + s) through a transient isotopic experiment with a feed gas containing 13CO and 12CH4. It was also found that CO-s derived from the direct dissociation of CO2 and the CH4 activation route can lead to a number of different kinds of “carbon” which depends on support chemical composition. The present 5 wt% Ni/Ce0.8Pr0.2O2 catalytic system exhibited CO2 conversion of 84%, H2-yield of 48%, and H2/CO ratio of 1.04 after 50 h of dry reforming of methane at 750 °C (20% CH4, 20% CO2, He; GHSV = 30,000 h−1) with a relatively low amount (17.5 mg C/gcat or 1.75 wt%) of accumulated inactive “carbon”. The support chemical composition was found to influence the nickel particle size, which in turn influenced the origin, kinetics and the reactivity of “carbon” deposition under dry reforming reaction conditions.

ACS Style

M.M. Makri; M.A. Vasiliades; K.C. Petallidou; A.M. Efstathiou. Effect of support composition on the origin and reactivity of carbon formed during dry reforming of methane over 5wt% Ni/Ce1−xMxO2−δ (M=Zr4+, Pr3+) catalysts. Catalysis Today 2015, 259, 150 -164.

AMA Style

M.M. Makri, M.A. Vasiliades, K.C. Petallidou, A.M. Efstathiou. Effect of support composition on the origin and reactivity of carbon formed during dry reforming of methane over 5wt% Ni/Ce1−xMxO2−δ (M=Zr4+, Pr3+) catalysts. Catalysis Today. 2015; 259 ():150-164.

Chicago/Turabian Style

M.M. Makri; M.A. Vasiliades; K.C. Petallidou; A.M. Efstathiou. 2015. "Effect of support composition on the origin and reactivity of carbon formed during dry reforming of methane over 5wt% Ni/Ce1−xMxO2−δ (M=Zr4+, Pr3+) catalysts." Catalysis Today 259, no. : 150-164.