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Stefanidis S.D.,Chemical Process and Energy Resources Institute | Stefanidis S.D.,University of Western Macedonia | Karakoulia S.A.,Chemical Process and Energy Resources Institute | Kalogiannis K.G.,Chemical Process and Energy Resources Institute | And 4 more authors.
Applied Catalysis B: Environmental | Year: 2016

The thermal and catalytic fast pyrolysis of biomass aims at the production of pyrolysis oil (bio-oil), which can be utilized as a source of chemicals or as a bio-crude for the production of hydrocarbon fuels. We investigated low-cost, naturally derived basic MgO materials as catalysts for the catalytic fast pyrolysis of lignocellulosic biomass as alternatives to classical acidic zeolite catalysts. The MgO catalysts were produced from natural magnesite mineral without any significant treatment besides calcination, crushing and sieving. Their structure, composition, porosity, morphology and surface properties were thoroughly examined by XRD, XRF, N2 porosimetry, SEM, TEM, TPD-CO2 and TPD-NH3. The physicochemical characteristics of the MgO catalysts depended mainly on the different production conditions (duration and temperature of calcination). Despite their negligible acidity, the MgO catalysts effectively reduced the oxygen content of the produced bio-oil and exhibited similar or even better performance compared to that of an industrial ZSM-5 catalyst formulation (i.e. non-catalytic pyrolysis: 38.9 wt.% organic bio-oil with 38.7 wt.% O2; ZSM-5 based catalyst: 20.7 wt.% organic bio-oil with 30.9 wt.% O2; selected natural MgO catalysts: 25.7 wt.% organic bio-oil with 31.0 wt.% O2 or 21.1 wt.% organic bio-oil with 28.4 wt.% O2). The basic sites of the MgO catalysts favored reduction of acids and deoxygenation via ketonization and aldol condensation reactions, as indicated by the product distribution and the composition of the bio-oil. Oxygen was removed mainly via the preferred pathway of CO2 formation, compared to CO and water as in the case of ZSM-5 zeolite. On the other hand, reaction coke slightly increased over the MgO catalysts as compared to ZSM-5; however, the MgO formed coke was oxidized/burnt at significantly lower temperatures compared to that of ZSM-5, thus enabling MgO regeneration by relatively mild calcination in air. A systematic correlation of product yields and oxygen content of bio-oil with the physicochemical properties of the MgO catalysts has been established. © 2016 Elsevier B.V.


Stefanidis S.,Chemical Process and Energy Resources Institute | Stefanidis S.,University of Western Macedonia | Kalogiannis K.,Chemical Process and Energy Resources Institute | Iliopoulou E.F.,Chemical Process and Energy Resources Institute | And 5 more authors.
Green Chemistry | Year: 2013

Mesopore-modified mordenite zeolitic materials with different Si/Al ratios have been prepared and tested in the biomass pyrolysis and catalytic cracking of vacuum gasoil. Alkaline treatment was carried out to generate mesoporosity. Severity of alkaline treatment was found to be of paramount importance to tune the generated mesoporosity, while it significantly affected the crystallinity of treated mordenites. It was moreover observed that the alkaline treatment selectively extracted Si decreasing the Si/Al ratio of treated samples. Catalytic activity of parent and alkaline treated mordenites was studied in the pyrolysis of biomass. All zeolitic based materials produced less amounts of bio-oil but of better quality (lowering the oxygen content from ∼40% to as much as 21%) as compared to the non-catalytic pyrolysis experiments. On the other hand, it was found that the combination of mesopore formation and high surface area after alkaline treatment of the mordenite with a high Si/Al ratio resulted in the enhancement of its catalytic activity, despite the reduction of its acidity. The increment of the decarboxylation and dehydration reactions, combined with a reduction of carbon deposition on the catalyst, resulted in a remarkable decrease in the oxygen content in the organic fraction and therefore, resulted in a superior quality liquid product. Alkaline treated mordenites were additionally acid treated targeting dealumination and removal of the extra framework debris, thus generating mesopore-modified mordenite samples with stronger acid sites and higher total acidity, as candidate catalysts for catalytic cracking of vacuum gasoil. Desilicated and especially desilicated and dealuminated mordenites exhibited the highest activity and selectivity towards LCO with the best olefinicity in gases and higher bottoms conversion. Therefore, an optimized desilicated-dealuminated mordenite additive could be an interesting candidate as a component of the FCC catalyst for a high LCO yield. © 2013 The Royal Society of Chemistry.


Iliopoulou E.F.,Chemical Process and Energy Resources Institute | Stefanidis S.,Chemical Process and Energy Resources Institute | Stefanidis S.,University of Western Macedonia | Kalogiannis K.,Chemical Process and Energy Resources Institute | And 4 more authors.
Green Chemistry | Year: 2014

The main objective of the present work was the evaluation of commercial ZSM-5 catalysts (diluted with a silica-alumina matrix) in the in situ upgrading of lignocellulosic biomass pyrolysis vapours and the validation of their bench-scale reactor performance in a pilot scale circulating fluidized bed (CFB) pyrolysis reactor. The ZSM-5 based catalysts were tested both fresh and at the equilibrium state, and were further promoted with cobalt (Co, 5% wt%) using conventional wet impregnation techniques. All the tested catalysts had a significant effect on product yields and bio-oil composition, both at bench-scale and pilot scale experiments, producing less bio-oil but of better quality. Incorporation of Co exhibited no additional effect on water or coke production induced by ZSM-5, compared to non-catalytic fast pyrolysis. On the other hand, Co addition significantly increased the formation of CO2 compared to the CO increase which was favored by the use of ZSM-5 alone. These changes in CO2/CO yields are indicative of the different decarbonylation/decarboxylation mechanism that applies for Co3O 4 compared to ZSM-5 zeolite, due to the differences in their acidic properties (mainly type of acid sites). Co-promoted ZSM-5 catalysts simultaneously enhanced the production of aromatics and phenols with a more pronounced performance in the pilot-scale experiments resulting in the formation of a three phase bio-oil, rather than the usual two phase catalytic pyrolysis oil (aqueous and organic phases). The third phase produced is even lighter than the aqueous phase and consists mainly of aromatic hydrocarbons and phenolic compounds. Addition of Co in ZSM-5 is thus suggested to strongly enhance aromatization reactions that result in selectivity increase towards aromatics in the bio-oil produced. Possible routes of catalyst deactivation in the pilot plant's continuous operation process have been suggested and are related to pore blocking and masking of acid sites by formed coke (reversible deactivation), partial framework dealumination of the fresh zeolitic catalyst, and accumulative ash deposition on the catalyst that depends on the nature of biomass (content of ash). © 2014 The Royal Society of Chemistry.


Alexopoulos A.H.,Chemical Process and Energy Resources Institute | Pladis P.,Chemical Process and Energy Resources Institute | Kiparissides C.,Aristotle University of Thessaloniki | Kiparissides C.,Chemical Process and Energy Resources Institute | Kiparissides C.,The Petroleum Institute
Industrial and Engineering Chemistry Research | Year: 2013

The present study describes the development of a nonhomogeneous two-compartment model for the prediction of particle size distribution in a semibatch emulsion ter-polymerization reactor. The multicompartment model accounts for spatial variations of particle size distribution (PSD) in the reactor due to nonideal mixing conditions. A comprehensive emulsion polymerization model is applied to each compartment, which allows the calculation of the various species concentrations in the aqueous and particle phases in each compartment. Moreover, a particle population balance equation is solved for each compartment to determine the individual PSDs as well as the overall PSD in the reactor. The effects of the two-compartment nonhomogeneous model parameters, that is, the volume ratio of the two compartments, the compartment exchange flow rates, and the partitioning of the monomer and initiator feed streams into the two compartments, on the overall polymerization rate and PSD are analyzed in detail. It is shown that depending on the selected values of the two-compartment model parameters, the overall PSD in the reactor can significantly vary (i.e., from a narrow and/or broad unimodal distribution to a bi- and/or multimodal PSD). Small compartment exchange flow rates, uneven monomer and initiator feed partitioning, or unequal compartment volumes can result in very different PSDs in the two compartments. Moreover, it is shown that for a range of parameter values in the two-compartment model (i.e., reflecting the degree of reactor nonhomogeneity), the calculated overall PSD in the industrial-scale reactor can be unimodal but significantly broader than the respective PSD calculated by the homogeneous one-compartment model. © 2013 American Chemical Society.


Gkementzoglou C.,Aristotle University of Thessaloniki | Kotrotsiou O.,Chemical Process and Energy Resources Institute | Kiparissides C.,Aristotle University of Thessaloniki | Kiparissides C.,Chemical Process and Energy Resources Institute | Kiparissides C.,The Petroleum Institute
Industrial and Engineering Chemistry Research | Year: 2013

Novel molecularly imprinted polymer (MIP) composite membranes for the selective removal of triazine herbicides from polluted water sources were synthesized using two different approaches. According to the first method, sandwich-type composite membranes were prepared that consisted of a middle packed layer of MIP nanoparticles (NPs) confined between two microfiltration membranes. The highly selective MIP NPs were synthesized in the presence of atrazine, acting as template molecule, via the mini-emulsion polymerization method. In the second approach, MIP thin films, formed via an in situ polymerization method in the presence of the template molecule (desmetryn), were deposited on the top surface of ceramic support membranes using 2,2′-azobis (N,N′-dimethylene) isobutyramidine as initiator. The rebinding capacity of the synthesized MIP-ceramic composite membranes toward the template molecules was initially tested in batch-wise guest binding experiments. Subsequently, the synthesized composite membranes were tested in continuous dead-end filtration experiments to assess their binding efficiency, specificity, and their ability to adsorb the template molecules from water samples, at very low concentrations (i.e., down to 1 ppb). A series of experiments were also carried out to assess the binding capacity of the regenerated composite membranes and their long-term performance. The present results clearly demonstrate that the synthesized MIP composite membranes can remove the triazine herbicides of atrazine and desmetryn from water samples at very low concentrations (i.e., down to 1 ppb). Finally, it was found that the MIP composite membranes could be regenerated and reused without loss of their binding capacity and "memory effect", which underlines their outstanding stability and reusability features in a continuous filtration process. © 2013 American Chemical Society.


Antzara A.,Aristotle University of Thessaloniki | Heracleous E.,Chemical Process and Energy Resources Institute | Heracleous E.,International Hellenic University | Lemonidou A.A.,Aristotle University of Thessaloniki | Lemonidou A.A.,Chemical Process and Energy Resources Institute
Energy Procedia | Year: 2014

A promising concept for post-combustion CO2 capture is carbonate looping, in which CO2 is captured at high temperature using calcium-based sorbents. The process suffers from degradation of the materials and decrease of CO2 capacity after multiple calcination/carbonation cycles. In this paper, we report the development of stable synthetic and natural mixed CaO-based sorbents for post-combustion CO2 capture from industrial plans flues gases. The promoted synthetic sorbents, synthesized via a sol-gel auto-combustion method, exhibited very stable performance for 100 consecutive sorption/desorption cycles and an increased CO2 uptake capacity. Promising performance was also achieved with a natural sorbents consisting of industrial watertreated hydrated lime mixed with a kaolin and/or MgO binder. © 2014 The Authors Published by Elsevier Ltd.


Pladis P.,Chemical Process and Energy Resources Institute | Alexopoulos A.H.,Chemical Process and Energy Resources Institute | Kiparissides C.,Chemical Process and Energy Resources Institute | Kiparissides C.,Aristotle University of Thessaloniki | Kiparissides C.,The Petroleum Institute
Industrial and Engineering Chemistry Research | Year: 2014

In the present study a comprehensive model is employed to describe the dynamic behavior of an industrial scale reactor for the emulsion polymerization of vinylidene fluoride (VDF) under different initiator and chain transfer agent (CTA) addition policies. A comprehensive kinetic model combined with a thermodynamic and a particle population model were simultaneously solved to calculate the VDF addition rate, reactor pressure, molecular weight properties, and the particle size distribution of polyvinylidene fluoride produced in a semibatch emulsion polymerization reactor. The proposed emulsion polymerization model takes into account the gas-liquid equilibrium of VDF to determine the aqueous phase VDF concentration and the changes in operating pressure. The effects of particle crystallinity on radical entry and coagulation rate were also considered. The computational model results (cumulative monomer feed and feed rate, reactor pressure, molecular weights, and particle size distribution) are found to be in agreement with available experimental data. © 2014 American Chemical Society.


Skoufa Z.,Aristotle University of Thessaloniki | Antzara A.,Aristotle University of Thessaloniki | Heracleous E.,Chemical Process and Energy Resources Institute | Heracleous E.,International Hellenic University | And 2 more authors.
Energy Procedia | Year: 2016

Carbonate Looping is a post-combustion CO2 capture technology in which CO2 is captured by a CaO-based sorbent. In this work, we report the development, preliminary evaluation and bench-scale testing of synthetic and natural sorbents. After preliminary screening, the most promising materials were studied in a fixed bed reactor under realistic flue gas feed composition. Zr and Al-doped synthetic CaO based sorbents exhibited very high sorption capacity and stability, due to their porous structure that is retained after 20 consecutive carbonation/calcination cycles. The natural sorbents presented inferior results, however their regeneration via hydration seems possible. The presence of steam in the flue gases seems to enhance sorption capacity and stability. © 2016 The Authors.


Koutsonikolas D.E.,Chemical Process and Energy Resources Institute | Kaldis S.P.,Chemical Process and Energy Resources Institute | Pantoleontos G.T.,UOWM | Zaspalis V.T.,Chemical Process and Energy Resources Institute | Sakellaropoulos G.P.,AUTh
Chemical Engineering Transactions | Year: 2013

In the present study, the integration of membrane technology in an Integrated Gasification Combined Cycle (IGCC) system has been considered, in order to reduce the power plant's CO2 emissions. In this respect three different membrane materials was examined (polymeric, ceramic and metallic) taking into account the latest advances in membranes' development. The simulation of membranes separation performance was conducted in a Visual Fortran code and this was incorporated in an Aspen Plus flow diagram for the overall performance assessment. The energy analysis of the alternative cases show that CO2 capture in this hybrid IGCC scheme is technically feasible but with an accompanying energy penalty in the power plant's output. Taking into account both technical and economic issues the most promising scenario seems to be the integration of a 2-staged ceramic membranes system for H2 separation and CO2 capture. Copyright © 2013, AIDIC Servizi S.r.l.


Thegarid N.,CNRS Research on Catalysis and Environment in Lyon | Fogassy G.,CNRS Research on Catalysis and Environment in Lyon | Schuurman Y.,CNRS Research on Catalysis and Environment in Lyon | Mirodatos C.,CNRS Research on Catalysis and Environment in Lyon | And 4 more authors.
Applied Catalysis B: Environmental | Year: 2014

Previous research showed that hydrodeoxygenated (HDO) pyrolysis-oils could successfully be co-processed with vacuum gasoil (VGO) in a labscale fluid catalytic cracking (FCC) unit to bio-fuels. Typically the hydrodeoxygenation step takes place at ~300. °C under 200-300. bar of hydrogen. Eliminating or replacing this step by a less energy demanding upgrading step would largely benefit the FCC co-processing of pyrolysis oils to bio-fuels. In this paper a bio-oil that has been produced by catalytic pyrolysis (catalytic pyrolysis oil or CPO) is used directly, without further upgrading, in catalytic cracking co-processing mode with VGO. The results are compared to the co-processing of upgraded (via HDO) thermal pyrolysis oil. Though small but significant differences in the product distribution and quality have been observed between the co-processing of either HDO or CPO, they could be corrected by further catalyst development (pyrolysis and/or FCC), which would eliminate the need for an up-stream hydrodeoxygenation step. Moreover, the organic yield of the catalytic pyrolysis route is estimated at approximately 30. wt.% compared to an overall yield for the thermal pyrolysis followed by a hydrodeoxygenation step of 24. wt.%. © 2013 Elsevier B.V.

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