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Iliopoulou E.F.,Greek Chemical Process Engineering Research Institute | Stefanidis S.D.,Greek Chemical Process Engineering Research Institute | Stefanidis S.D.,University of Western Macedonia | Kalogiannis K.G.,Greek Chemical Process Engineering Research Institute | And 3 more authors.
Applied Catalysis B: Environmental | Year: 2012

The main objective of the present work was the study of different ZSM-5 catalytic formulations for the in situ upgrading of biomass pyrolysis vapors. An equilibrium, commercial diluted ZSM-5 catalyst was used as the base case, in comparison with a series of nickel (Ni) and cobalt (Co) modified variants at varying metal loading (1-10wt.%). The product yields and the composition of the produced bio-oil were significantly affected by the use of all ZSM-5 catalytic materials, compared to the non-catalytic flash pyrolysis, producing less bio-oil but of better quality. Incorporation of transition metals (Ni or Co) in the commercial equilibrium/diluted ZSM-5 catalyst had an additional effect on the performance of the parent ZSM-5 catalyst, with respect to product yields and bio-oil composition, with the NiO modified catalysts being more reactive towards decreasing the organic phase and increasing the gaseous products, compared to the Co 3O 4 supported catalysts. However, all the metal-modified catalysts exhibited limited reactivity towards water production, while simultaneously enhancing the production of aromatics and phenols. An interesting observation was the in situ reduction of the supported metal oxides during the pyrolysis reaction that eventually led to the formation of metallic Ni and Co species on the catalysts after reaction, which was verified by detailed XRD and HRTEM analysis of the used catalysts. The Co 3O 4 supported ZSM-5 catalysts exhibited also a promising performance in lowering the oxygen content of the organic phase of bio-oil. © 2012 Elsevier B.V.

Martavaltzi C.S.,Aristotle University of Thessaloniki | Martavaltzi C.S.,Greek Chemical Process Engineering Research Institute | Lemonidou A.A.,Aristotle University of Thessaloniki | Lemonidou A.A.,Greek Chemical Process Engineering Research Institute
Chemical Engineering Science | Year: 2010

This study presents the development and the evaluation of a new hybrid material, NiO-CaO-Ca12Al14O33, which functions simultaneously as reforming catalyst and CO2 sorbent for application in sorption enhanced reforming. CaO-Ca12Al14O33 acts as an effective CO2 sorbent and also as a support for the active metallic Ni particles. This idea aims to overcome the complex problems related with handling of the two different solids (catalyst and CO2 sorbent) required for sorption enhanced reforming and also to increase the industrial potential of the process by decreasing the cost of the total solid material used. The CO2 fixation ability of the new material (56% carbonation conversion) remains unchanged for 45 cycles of sorption-desorption. It is assumed that the presence of NiO acts synergetically with Ca12Al14O33 to the excellent stability of the novel material compared with other CaO-based sorbents. The effect of NiO loading on the catalytic functionality of the material, under methane sorption enhanced reforming conditions was studied and the results showed that conversion goes through a maximum (80%) in the presence of the hybrid material with 16 wt% Ni loading. The hybrid material with the optimum metallic loading was tested at 650 °C and methane to steam ratio equal to 3.4. The presence of free CaO resulted in the capture of CO2 formed, producing a stream rich in H2 (90%) and poor in CO2 (2.8%) and CO (2%). © 2010 Elsevier Ltd. All rights reserved.

Zacharopoulou V.,Aristotle University of Thessaloniki | Vasiliadou E.S.,Aristotle University of Thessaloniki | Lemonidou A.A.,Aristotle University of Thessaloniki | Lemonidou A.A.,Greek Chemical Process Engineering Research Institute
Green Chemistry | Year: 2015

This work presents a novel, one-step catalytic process, enabling highly selective propylene formation via glycerol hydro-deoxygenation (HDO) reactions. Fe-Mo catalysts, supported on black and activated carbons, are selective towards C-O bond cleavage, thus converting glycerol to propylene with high yields. BET, XRD, TPD-NH3 and TPD-He methods have been employed for the characterization of the samples. Molybdenum oxide, at its reduced state, is essential for driving selectively the reaction towards complete deoxygenation. The only product of glycerol HDO is propene, in the gas phase, while 2-propenol, propanols and propylene glycol have been detected, among others, in the liquid phase. Under the standard reaction conditions (300°C temperature, 8.0 MPa hydrogen pressure), glycerol conversion exceeds 88% and selectivity to propene reaches 76% after 6 hours of reaction. This study includes the investigation of the operating conditions effect (i.e. reaction time, reaction temperature, catalyst loading and H2 pressure) regarding glycerol HDO towards propene formation. This journal is © The Royal Society of Chemistry. The Royal Society of Chemistry 2015.

Vasiliadou E.S.,Aristotle University of Thessaloniki | Vasiliadou E.S.,Greek Chemical Process Engineering Research Institute | Lemonidou A.A.,Aristotle University of Thessaloniki | Lemonidou A.A.,Greek Chemical Process Engineering Research Institute
Applied Catalysis A: General | Year: 2011

Selective hydrogenolysis of glycerol to propylene glycol was performed over monometallic (5 and 20 wt%Cu) and a bimetallic (5 wt%Ru-Cu) catalyst. The catalytic materials used, were supported on commercial silica and synthesized hexagonal mesoporous silica (HMS). The catalysts (fresh and used) were characterized employing XRD, ICP, BET surface area, N2O chemisorption, TEM, TGA and TPR techniques. The performance of 5 wt%Cu monometallic catalysts is characterized by high propylene glycol selectivity (>90%) and relatively low activity. Increase of Cu loading to 20 wt% results in satisfactory activity. At 240 °C and 8 MPa hydrogen pressure, the 20 wt%Cu/HMS catalyst exhibits 43% glycerol conversion along with 91% propylene glycol selectivity and TOF 148 h-1. The bimetallic Ru-Cu catalyst supported on silica combines both good selectivity and activity providing evidence for synergetic effect between the two metals. Silica type (commercial or mesoporous) affects mainly the dispersion and hence the active copper metal area with the HMS supported monometallic catalysts exhibiting higher activity than those supported on commercial silica. Present results indicate that glycerol hydrogenolysis over Cu catalysts is a structure sensitive reaction. Partial loss of activity in consecutive glycerol hydrogenolysis tests was observed with the best performing 20 wt%Cu/HMS catalyst. Based on characterization results of the reused catalyst, the deactivation was attributed to a number a factors like partial collapse of the mesoporous network, agglomeration of the active metallic phase, presence adsorbed species on the catalytic surface and/or formation of coke during the reaction. No indication of Cu leaching to the liquid phase was provided. © 2011 Elsevier B.V. All rights reserved.

Tzanetis K.F.,Aristotle University of Thessaloniki | Martavaltzi C.S.,Aristotle University of Thessaloniki | Lemonidou A.A.,Aristotle University of Thessaloniki | Lemonidou A.A.,Greek Chemical Process Engineering Research Institute
International Journal of Hydrogen Energy | Year: 2012

Exergy efficiency analysis tool is used to evaluate sorption enhanced steam reforming in comparison with the industrial hydrogen production route, steam reforming. The study focuses on hydrogen production for use in high pressure processes. Thermodynamic sensitivity analysis (effect of reforming temperature on hydrogen yield and reforming enthalpy) was performed to indicate the optimum temperature (650 °C) for the sorption enhanced reforming. The pressure was selected to be, for both cases, 25 bar, a typical pressure used in the industrial (conventional) process. Atmospheric pressure, 1000 °C and CO 2 as inert gas were specified as the optimum operating parameters for the regeneration of the sorbent after performing exergy efficiency analysis of three realistic case scenarios. Aspen Plus simulation process schemes were built for conventional and sorption enhanced steam reforming processes to attain the mass and energy balances required to assess comparatively exergy analysis. Simulation results showed that sorption enhanced reforming can lead to a hydrogen purity increase by 17.3%, along with the recovery of pure and sequestration-ready carbon dioxide. The exergy benefit of sorption enhanced reforming was calculated equal to 3.2%. Analysis was extended by adding a CO 2 separation stage in conventional reforming to reach the hydrogen purity of sorption enhanced reforming and enable a more effective exergy efficiency comparison. Following that analysis, sorption enhanced reforming gained 10.8% in exergy efficiency. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Vasiliadou E.S.,Greek Chemical Process Engineering Research Institute | Eggenhuisen T.M.,University Utrecht | Munnik P.,University Utrecht | de Jongh P.E.,University Utrecht | And 3 more authors.
Applied Catalysis B: Environmental | Year: 2014

The performance of Cu/SiO2 (commercial silica gel, SBA-15 and SBA-15 treated at 900°C) catalysts for the hydrogenolysis of glycerol to propylene glycol is investigated with emphasis on the stability characteristics. Cu catalysts with large crystals, small monodisperse crystallites or a highly dispersed XRD amorphous copper phase were obtained after calcination in stagnant air, in a flow of NO/N2 or a flow of air, respectively. Analysis by XRD, N2O surface oxidation and TEM confirmed the variation of the Cu specific surface area by the calcination conditions and the type of silica support used. The different dispersion characteristics resulted in different activities (20-50% glycerol conversion), while all the catalysts proved to be highly selective towards propylene glycol (92-97%). Present results indicate that glycerol hydrogenolysis over Cu-based catalysts is a structure sensitive reaction as significant variations in initial TOF were observed as a function of varying Cu crystallites. It is shown here that the presence of a solvent greatly influences the intrinsic reaction rate and the nature of structure sensitivity. The deactivation behaviour of all catalysts was studied, and based on detailed characterization of the spent samples it was attributed to Cu sintering and the presence of strongly adsorbed species on the catalytic surface. The 18wt%Cu/silica gel (air) catalyst presented only moderate deactivation (~20%) while the catalyst supported on SBA-15 calcined at 900°C (SBA900C) proved to be the most stable with negligible deactivation after three consecutive runs. © 2013 Elsevier B.V.

Triantafyllidis K.S.,Aristotle University of Thessaloniki | Peleka E.N.,Aristotle University of Thessaloniki | Komvokis V.G.,Greek Chemical Process Engineering Research Institute | Mavros P.P.,Aristotle University of Thessaloniki
Journal of Colloid and Interface Science | Year: 2010

Highly efficient sorbents for phosphate removal from aqueous solutions based on the calcined forms of Fe(III)-substituted Layered Double Hydroxides (LDH) materials have been developed in this study. Hydrotalcite-like materials with Mg/M3+ ∼3 (where M = Al3+, Fe3+ or combined) have been synthesized following simple co-precipitation method and were subsequently calcined in air at 450 °C. Both as-synthesized and calcined materials were characterized by means of X-ray Diffraction (XRD), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), elemental (C) analysis, N2 porosimetry, Scanning Electron Microscopy (SEM). All the materials were evaluated for the sorption of phosphates by batch equilibrium sorption experiments and kinetic measurements (effect of contact time). It was shown that chlorides or nitrates, being the charge-balancing anions in the LDH structure, are more easily exchanged by phosphates compared to carbonates. In the Fe(III)-modified LDHs, an increase of the Fe loading led to the decrease of the sorption efficiency. The maximum uptake of phosphates for both the Mg-Al LDH and Mg-Fe LDH samples containing mainly carbonates as charge-balancing anions was relatively low (ca. ≤25 mg P/g sorbent) while it was higher for the LDH samples containing mainly chlorides (∼80 mg P/g). On the other hand, the maximum sorption capacity for the calcined Mg-Al LDHs and the calcined Fe(III)-substituted sorbents were very high, ca. ∼250 and ∼350 mg P/g, respectively. The sorption data of both the as-synthesized and calcined LDHs was best fitted by the Freundlich model. Both the Mg-Al and Fe-substituted LDH sorbents were regenerated with mixed aqueous solution of NaCl and NaOH and were reused with a small loss of removal efficiency. © 2009 Elsevier Inc. All rights reserved.

Diamantopoulou Ir.,Aristotle University of Thessaloniki | Skodras G.,Institute for Solid Fuels Technology and Applications | Sakellaropoulos G.P.,Aristotle University of Thessaloniki | Sakellaropoulos G.P.,Greek Chemical Process Engineering Research Institute
Fuel Processing Technology | Year: 2010

The purpose of the current study is to evaluate the mercury removal ability of F400 and Norit FGD activated carbons, through fixed bed adsorption tests at inert atmosphere (Hg° + N2). Additionally, adsorption tests were realized on F400 activated carbon, in the presence of HCl, O2, SO2 and CO2 in nitrogen flow. The obtained results, revealed that F400 activated carbon, with a high-developed micropore structure and increased BET area, exhibit larger Hg° adsorptive capacity compared to Norit. HCl and O2, can strongly affect mercury adsorption, owing to heterogeneous oxidation and chemisorption reactions, which is in accordance with the assumptions of some researchers. Additionally, SO2 presence enhances mercury adsorption, in contrast with the conclusions evaluated in other studies. The above result could be attributed to the possible formation of sulphur spaces on activated carbon surface and consist of a clarification for the role of SO2 on mercury adsorption. On the contrary, the mercury adsorption efficiency of F400 activated carbon showed a decrease at about 25%, with increasing CO2 concentration from 0 to 12%. © 2009 Elsevier B.V. All rights reserved.

Kouvaris P.,Aristotle University of Thessaloniki | Delimitis A.,Greek Chemical Process Engineering Research Institute | Zaspalis V.,Aristotle University of Thessaloniki | Papadopoulos D.,Aristotle University of Thessaloniki | And 2 more authors.
Materials Letters | Year: 2012

Metallic nanoparticles have received great attention from chemists, physicists, biologists and engineers who wish to use them for the development of a new generation of nanodevices. In the present study silver nanoparticles were synthesized from aqueous silver nitrate through a simple and eco-friendly route using leaf broth of Arbutus unedo, which acted as a reductant and stabilizer simultaneously. The aqueous silver ions when exposed to the leaf broth were reduced and stabilized over long periods of time resulting in the green synthesis of surface functionalized silver nanoparticles. The bio-reduced silver nanoparticles were appropriately characterized. The results revealed the formation of single crystalline Ag nanoparticles with a narrow size distribution for each sample. The particles, although discrete, were predominately coated with the organic leaf extract forming small aggregates, which makes them stable over long time periods and highly appropriate for coatings or biotechnology applications. © 2012 Elsevier B.V. All rights reserved.

Vasiliadou E.S.,Aristotle University of Thessaloniki | Vasiliadou E.S.,Greek Chemical Process Engineering Research Institute | Lemonidou A.A.,Aristotle University of Thessaloniki | Lemonidou A.A.,Greek Chemical Process Engineering Research Institute
Organic Process Research and Development | Year: 2011

The production of 1,2-propanediol from renewable glycerol in hydrogen atmosphere is of high interest. In this study the reaction was performed in the presence of 5 wt %Ru/SiO2 catalyst and the effects of reaction temperature, hydrogen pressure and glycerol concentration were investigated. The catalytic results indicate that increased temperature and pressure favor glycerol conversion and propylene glycol selectivity. Glycerol conversion remains almost constant with water dilution, but 1,2-propanediol selectivity increases due to the function of water as a solvent and the suppression of side reactions, such as degradation and polymerization. At the optimum reaction conditions (T = 240 °C, P = 8 MPa H2, pure glycerol feedstock, catalyst/glycerol ratio = 0.006, reaction time = 5 h) glycerol conversion reaches the value of 21.7% along with 60.5% 1,2-propanediol selectivity. The activity of the catalyst does not change in two consecutive runs, while propylene glycol selectivity slightly decreases due to the formation of overhydrogenolysis products (propanols). The reaction pathways over Ru/SiO 2 catalyst were explored using intermediate and final products as reactants. The production of 1,2-propanediol is favorable as it is formed with high selectivity from acetol and its overhydrogenolysis to propanols is very limited. The results suggest that ethylene glycol is a primary product originating from the direct degradation of glycerol. © 2011 American Chemical Society.

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