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Energy & Fuels 01/2012; 26:1353-1362. · 2.72 Impact Factor
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ABSTRACT: Biomass autothermal flash pyrolysis has been carried out by adding oxygen to the reaction environment in a bench-scale plant provided with a conical spouted bed reactor, at 500 C and using two oxygen concentrations in the inlet gas stream (2.5 and 4.1 vol %, which correspond to equivalence ratios of 15 and 25, respectively). An increase in the oxygen concentration leads to an increase in gas and water yields, whereas there is a decrease in the yield of both char (partially burned), and organic compounds in the bio-oil, albeit only slightly in the latter case. Bio-oil composition undergoes only minor changes for certain individual components. The experimental results' highlight the advantages of the conical spouted bed reactor (CSBR), for scaling up the autothermal operation. A study on energy requirements reveals that the oxygen concentration needed to achieve autothermal operation decreases as the scale is larger. The oxygen content required in the inlet gas stream for autothermal operation in an industrial-scale plant of 500 kg h(-1) is 2.7 vol %, and neither bio-oil yield nor composition is significantly affected, being similar to the case of operating in an inert atmosphere.
Energy & Fuels. 01/2012; 26(2):1353-1362.
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Drying Technology 01/2012; 30(2):207-216. · 2.08 Impact Factor
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Resources Conservation and Recycling 01/2012; 59:23-31. · 1.76 Impact Factor
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Journal of Analytical and Applied Pyrolysis 01/2012; 94:230-237. · 2.49 Impact Factor
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Chemical Engineering Journal. 01/2012; 207-208:27-34.
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Chemical Engineering & Technology 06/2011; 34(7):1130 - 1135. · 1.60 Impact Factor
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ABSTRACT: The continuous flash pyrolysis of lignocellulosic biomass under atmospheric and vacuum conditions (0.25 atm) has been studied in a bench-scale plant provided with a conical spouted bed reactor. A previous kinetic study has been carried out in thermobalance, and the kinetic data have been fitted to a three parallel and independent reaction model by deconvolution of the differential thermogravimetry (DTG) curve. The influence of vacuum on product yields, compositions, and properties has been carried in a bench-scale plant at 400 and 500 degrees C. Vacuum operation in a conical spouted bed is advantageous for biomass pyrolysis because of the reduction in the N(2) mass flow rate required for the spouted bed regime. Consequently, the energy requirements for heating Nz and the problems related to the condensation of the outlet stream are significantly reduced. The yields obtained and the composition of the bio-oil provide evidence that the vacuum operation does not affect the good gas-solid contact and the excellent performance of the conical spouted bed reactor for lignocellulosic biomass flash pyrolysis. High bio-oil yields are obtained, 77% at 500 degrees C and under 0.25 atm. Vacuum leads to a slightly heavier and less oxygenated bio-oil and a char fraction with improved surface characteristics.
Energy & Fuels. 01/2011; 25(9):3950-3960.
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Chemical Engineering Research and Design 01/2011; 89(10):2054-2062. · 1.97 Impact Factor
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Industrial and Engineering Chemistry Research. 01/2011; 50(11):6650-6659.
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ABSTRACT: The effect of the zeolite structure (HZSM-5, H beta and HY) on coke deposition during the cracking of high-density polyethylene has been studied by combining the results of multiple spectroscopic and analytical techniques: FTIR, Raman, UV-vis, (13)C NMR and coke extraction, followed by GC-MS and (1)H NMR analysis. In addition, by combining FTIR and temperature programmed oxidation (TPO) analysis we obtained information on the coke: properties, burn-off, and changes in composition during catalyst regeneration. Samples of the spent catalysts were obtained in a state-of-the-art pilot plant (conical spouted bed reactor) after the continuous treatment of 900 g (1 g min(-1), 15 h) of high-density polyethylene at 500 degrees C, using 30 g of catalyst. The results show that as the pore diameter of the zeolite is increased, bimolecular reactions (hydrogen transfer and oligomerizations), condensations and cyclizations are enhanced, yielding more aromatic coke. Furthermore, the pore topology of the HZSM-5 zeolite improves the flow of coke precursors (also favored by the high flow rate of N(2)) to the outside of the catalyst: viz. HZSM-5 catalyst preserves its activity for longer. (C) 2011 Elsevier B.V. All rights reserved.
Applied Catalysis B-Environmental. 01/2011; 104(1-2):91-100.
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ABSTRACT: The deactivation of noble metal catalysts has been studied in the hydrocracking of the Light Cycle Oil (LCO) obtained as a byproduct in FCC units. The catalyst metallic functions are Pd, Pt, and Pt-Pd, which are supported on acid materials of different porous structure and acidity (HY zeolite, H beta zeolite, amorphous alumina, and an FCC catalyst). The reaction conditions are 350 degrees C; 50 bar; H(2)/LCO molar ratio (n(H2)), 8.9 molH(2) (mol(LCO))(-1); space velocity (WHSV), 4 h(-1); time on stream, 300 min. The roles of the metallic function, porous structure of the support, and, particularly, catalyst acidity in the deactivation by coke deposition have been studied. Deactivation leads the catalyst to a pseudostable state, with significant activity remaining when a support with high acidity is used (a HY zeolite with SiO(2)/Al(2)O(3) = 5) and a better performance of the Pt-Pd metallic function.
Energy & Fuels. 01/2011; 25(8):3389-3399.
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ABSTRACT: The deactivation by coke of a HZSM-5 zeolite catalyst has been studied in the transformation of methanol into hydrocarbons by cofeeding butane (n-butane). This reaction is of interest as an energy-neutral integrated process that enhances the activity in the cracking reaction and upgrades the paraffins formed as byproducts. The process was carried out in a fixed-bed reactor under the following conditions: temperature, 550 degrees C; pressure, 1 bar; space time, 2.4 and 4.8 (g of catalyst) h (mol of CH(2))(-1); time on stream, 5 h; methanol/butane molar ratio, up to 16/1. The coke was characterized using several analytical techniques (TG-TPO, FTIR, Raman, and NMR spectroscopies), and the effects of cofeeding butane on the coke composition and structure were determined. The results in terms of coke content and composition, are explained in terms of the different pathways of methanol and butane transformation.
Industrial & Engineering Chemistry Research. 01/2011; 50(17):9980-9988.
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ABSTRACT: The deactivation of three different catalysts used in the cracking of high density polyethylene (HDPE) has been compared. The catalysts used are HZSM-5, H beta and HY zeolites agglomerated with bentonite and alumina. The reactions have been carried out in a conical spouted bed reactor at 500 degrees C, and plastic (high density polyethylene) has been fed in continuous mode (1 g min(-1)) for up to 15 h of reaction. The HZSM-5 zeolite catalyst gives way to high yields of C(2)-C(4) olefins (57 wt%) and, moreover, it is the one least influenced by deactivation throughout the run, which is explained by the lower deterioration of its physical properties and acidity. The results of temperature program combustion and transmission electron microscopy show that coke growth is hindered in the HZSM-5 zeolite pore structure. The high N(2) flow rate used in the conical spouted bed reactor enhances coke precursor circulation towards the outside of the zeolite crystal channels. (C) 2010 Elsevier By. All rights reserved.
Applied Catalysis B-Environmental. 01/2011; 102(1-2):224-231.
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ABSTRACT: Hydrocracking of secondary interest refinery streams (high aromatic content) can yield valuable products for transportation and petrochemical industry. In order to promote the hydrogenation and cracking steps, a bifunctional catalyst (metal + acid function) is required. We have studied the effect of the operating conditions on cycloalkane (product of aromatic hydrogenation) ring opening over a monofunctional HZSM-5 zeolite, by focusing on the effect of hydrogen in the cracking mechanisms. Methylcyclohexane has been selected as the test reactant and the conditions used corresponds to temperature, 250-450 degrees C; space velocity, 0.7-1.1 h(-1); pressure, 2-80 bar; hydrogen/methylcyclohexane molar ratio, 1-79; conversion, 0-100% (integral reactor). At these conditions the zeolite catalyses hydrogenation as well as cracking (bifunctional capabilities), thus the cracking mechanisms are directly affected by hydrogen as products (alkenes) and intermediates (carbenium ions) are saturated. The overall effect of rising hydrogen partial pressure is an enhancement of (hydro)isomerization and monomolecular cracking, that is, an increase of the yield/selectivity of methane, ethane, penthane and isoalkanes. (C) 2009 Elsevier B.V. All rights reserved.
Catalysis Today. 01/2010; 150:363-367.
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ABSTRACT: The continuous pyrolysis of waste tires under vacuum conditions (25 and 50 kPa) has been studied in a pilot plant equipped with a conical spouted bed reactor and operating with continuous feed at 425 and 500 degrees C. The effects of vacuum on product distribution and properties have been studied. The main effect of vacuum is an increase in the diesel fraction yield of the liquid product. A remarkable yield of isoprene has been obtained operating under vacuum, reaching yields of higher than 7 wt % Moreover, a positive effect on the quality of the residual carbon black has been observed, given that a decrease in pore blockage gives way to higher surface areas of the carbon blacks obtained. The results show that vacuum operation does not limit the good perspectives for waste tire valorization by pyrolysis in a conical spouted bed, and energy requirements for heating the inert gas and the condensation section are significantly reduced.
Industrial & Engineering Chemistry Research. 01/2010; 49(19):8990-8997.
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ABSTRACT: Continuous pyrolysis of scrap tyres has been carried out in a conical spouted bed reactor and the results (yields, composition of the volatile fraction and carbon black properties) have been compared with those obtained operating in batch mode in a previous study. Continuous operation in the 425-600 degrees C range gives way to a yield of 1.8-6.8 wt.% of gases, 44.5-55.0 wt.% of liquid fraction (C(5)-C(10) range hydrocarbons, with a maximum yield of limonene of 19.3 wt.% at 425 degrees C), 9.2-11.5 wt.% of tar (C(11)(+)) and 33.9-35.8 wt.% of char. The main differences between the continuous and batch processes are in the yield of light aromatics, which is higher in the continuous process, and in that of the heavy liquid fraction or tar, which is higher in the batch process. These are the advantages of the continuous process, although hydrogenation of the liquid fraction is required even in this case in order to use it as fuel. The high yield of limonene, the flexibility in the operating conditions and the capacity for a continuous removal of the residual carbon black from the reactor are the advantages of conical spouted bed technology. The excellent performance of the conical spouted bed reactor for the tyre pyrolysis process is due to the solid cyclic movement, the good contact between phases, the high heating rate and the reduced residence time of the volatile products. (C) 2010 Elsevier Ltd. All rights reserved.
Fuel. 01/2010; 89(8):1946-1952.
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ABSTRACT: BACKGROUND: The catalytic processes for valorizing the bio-oil obtained from lignocellulosic biomass pyrolysis face the problem that a great amount of carbonaceous material is deposited on the catalyst due to the polymerization of phenol-derived compounds in the crude bio-oil. This carbonaceous material blocks the catalytic bed and contributes to rapid catalyst deactivation. This paper studies an on-line two-step process, in which the first one separates the polymerizable material and produces a reproducible material whose valorization is of commercial interest.RESULTS: The establishment of a step for pyrolytic lignin deposition at 400 °C avoids the blockage of the on-line catalytic bed and attenuates the deactivation of a HZSM-5 zeolite based catalyst used for hydrocarbon production. The origin of catalyst deactivation is coke deposition, which has two fractions (thermal and catalytic), whose content is attenuated by prior pyrolytic lignin separation and by co-feeding methanol. The morphology and properties of the material deposited in the first step (pyrolytic lignin) are similar to lignins obtained as a by-product in wood pulp manufacturing.CONCLUSIONS: The proposed reaction strategy, with two steps (thermal and catalytic) in series, valorizes the crude bio-oil by solving the problems caused by the polymerization of phenolic compounds, which are obtained in the pyrolysis of the lignin contained in lignocellulosic biomass. Given that a by-product (pyrolytic lignin) is obtained with similar properties to the lignin from wood pulping manufacturing, the perspectives for the viability of lignocellulosic biomass valorization are promising, which is essential for furthering its implementation in biorefinery processes. Copyright © 2009 Society of Chemical Industry
Journal of Chemical Technology & Biotechnology 11/2009; 85(1):132 - 144. · 2.17 Impact Factor
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ABSTRACT: A study has been carried out on spouting performance in conical spouted beds at high temperatures and under vacuum by using materials of different textures, densities and particle diameters. The applicability of existing correlations for determining the minimum spouting velocity has been checked and, based on a statistical analysis to assess the influence of the dimensionless modulus, a new one has been proposed for the prediction of the minimum spouting velocity under vacuum and at high temperatures. This correlation provides good predictions in the pyrolysis of tyres under vacuum.Une étude a été effectuée sur le rendement en matière de jaillissement dans les lits jaillissants coniques à des températures élevées et sous vide en utilisant des matières ayant différentes textures et densités et différents diamètres de particules. L'applicabilité des corrélations existantes en vue de déterminer la vitesse de jaillissement minimale a été vérifiée et, en s'appuyant sur une analyse statistique visant à évaluer l'influence du module adimensionnel, une nouvelle corrélation a été proposée en ce qui a trait à la prédiction de la vitesse de jaillissement minimale sous vide et à des températures élevées. Cette corrélation offre de bonnes prédictions en ce qui concerne la pyrolyse des pneus sous vide.
The Canadian Journal of Chemical Engineering 07/2009; 87(4):541 - 546. · 0.75 Impact Factor
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ABSTRACT: A model of general application that is based on the definition of streamlines and that is in agreement with the bed geometry has been proposed in order to describe the gas flow in a jet spouted bed in conical contactors. The model quantifies the dispersion in the direction of the streamlines by using a characteristic modulus.The validity of the model has been experimentally proven on the basis of the measurement and analytical correlation of gas velocity profiles at different radial and longitudinal positions in the contactor, and of the application of the stimulus response technique for the calculation of the residence time distribution function.On propose un modèle ďapplication générale basé sur la définition des lignes de courant et compatible avec la géométrie du lit pour décrire ľécoulement du gaz dans un lit jaillissant à jet dans des contacteurs coniques. Le modèle quantifie la dispersion dans la direction des lignes de courant au moyen ďun module caractéristique.On a prouvé de façon expérimental la validité du modèle en s'appuyant, ďune part, sur la mesure et la corrélation analytique des profils de vitesse de gaz à des positions radiales et longitudinales diférentes dans le contacteur et, ďautre part, sur ľapplication de la technique des réponses aux stimulations pour le calcul de la fonction de distribution de temps de séjour.
The Canadian Journal of Chemical Engineering 03/2009; 71(2):189 - 194. · 0.75 Impact Factor
