127 research outputs found
Comment on the paper "Diffusion and adsorption selectivities of hydrocarbons over FCC catalysts" by A.M. Ávila, C.M. Bidabehere and U. Sedran [Chem. Eng. J. 132 (2007) 67-75]
No full textIn a letter by Kärger [1] about our paper on the assessment of the diffusivities in fluid catalytic cracking (FCC) catalysts [2], it is mentioned that diffusivities calculated by different methods (macroscopic in one case, or from pulsed field gradient (PFG) NMR technique in the other) are different. It is also pointed out that the results of diffusivities for a given compound obtained from different macroscopic techniques are not explained satisfactorily. Both facts are true. We understand that the letter is not only a valuable contribution to the field, considering its large and laborious data collection, but also an incentive for the search of a better comprehension of the mechanisms controlling the FCC process. Most importantly, the differences observed should not hamper experiments with macroscopic techniques nor lead to disregard results suspected of mass and/or heat transfer limitations. It is important to recognize them as enriched by other type of information, and that they become necessary as design tools. By these reasons, and considering that not too much can be added to the details depicted in Ref. [1], we believe it would be useful to clarify some issues, mainly pointing to a distinct approach in the interpretation of the data.Fil: Bidabehere, Claudia María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Avila, Adolfo María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin
Operation of FCC with mixtures of regenerated and deactivated catalyst
No full textThe operation of FCC with mixtures of coked and regenerated catalyst was studied with a riser simulator reactor on two equilibrium catalysts at 550◦C. The coked catalysts maintain an activity level that enables them to be used in the mixtures. The catalytic performances of the regenerated catalysts were used as references against which the behaviors of 25:75 and 50:50 (coked:regenerated) mixtures were compared. It was observed that overall catoil has to be increased to maintain conversion. While the yields of gases, gasoline and LCO showed to be independent of the operative mode, changes were observed in the selectivity to light olefinsC4?C6that are mainly due to changes in the yields of the isoparaffins in the groups. In turn, these changes could be the consequence of the resulting density of paired acid sites in the zeolite components on hydrogen transfer reactions, due to the contributions by the coked and regenerated portions of catalysts. Coke yields in mixtures of coked and regenerated catalysts are not higher, which would allow increasing catalyst circulation without impacting on heat balance. The particularities of this new operation of FCC are very dependent on catalyst properties.Fil: Spretz, R.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin
Intracrystalline Mesoporosity over y Zeolites: PASCA Evaluation of the Secondary Cracking Inhibition in the Catalytic Cracking of Hydrocarbons
No full textTwo FCC catalyst prototypes were prepared using Y zeolite with different intracrystalline mesoporosity, which were used in the cracking of n-hexadecane (batch fluidized bed reactor, reaction time 4 s, temperatures 500 and 550°C, catalyst/reactant 2.6). The primary and secondary cracking analysis method (PASCA), based on balances of carbon atoms among cracking products, showed that increasing the mesoporosity in Y zeolite decreases the incidence of secondary cracking as compared to primary cracking, thus increasing the selectivity to intermediate products. This positive effect was the consequence of the improvements in the diffusion transport of primary product molecules which, in diffusing faster out of the pores, have fewer chances to suffer further cracking. The experiments at different temperatures, with both the prototypes and the equilibrium commercial FCC catalysts, confirmed that this method is a simple tool that allows characterizing the cracking performance of FCC catalysts under conditions similar to those in commercial plants. (Figure Presented).Fil: García, Juan Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Falco, Marisa Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin
Evaluation of hydrogen transfer in FCC catalysts. A new approach for cyclohexene as a test reactant
No full textThe conversion of cyclohexene over different commercial FCC catalysts in a batch fluidized-bed reactor under very short contact times at 300°C, was described by means of a simple lumped kinetic model that accounted for the observed yield patterns. The main branch of reaction starting from the adsorption of cyclohexene was used to assess an index based on kinetic parameters that defines the relative significance of hydrogen transfer reactions in a set that also includes proton transfer and cracking reactions. Complementary experiments with pulses of reactant on a fixed-bed reactor allowed to establish the best temperature to obtain maximum sensitivity to hydrogen transfer. The same evolutions were observed for the relationships between the index of hydrogen transfer and the paired acid site density with the Y zeolite unit cell size, confirming that two regions can be defined separated by unit cell sizes of about 24.28–24.30 Å, the correlations being stronger at low values of this parameter.Fil: de la Puente, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin
Conversion of pine sawdust bio-oil (raw and thermally processed) over equilibrium FCC catalysts
No full textA raw bio-oil from pine sawdust, the liquid product from its thermal conditioning and a synthetic bio-oil composed by eight model compounds representing the main chemical groups in bio-oils, were converted thermally and over a commercial equilibrium FCC catalyst. The experiments were performed in a fixed bed reactor at 500 C. The highest hydrocarbon yield (53.5 wt.%) was obtained with the conditioned liquid. The coke yields were significant in all the cases, from 9 to 14 wt.%. The synthetic bio-oil produced lesser hydrocarbons and more oxygenated compounds and coke than the authentic feedstocks from biomass. The previous thermal treatment of the raw bio-oil had the positive effects of increasing 25% the yield of hydrocarbons, decreasing 55% the yield of oxygenated compounds and decreasing 20% the yield of coke, particularly the more condensed coke.Fil: Bertero, Melisa Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones En Catalisis y Petroquímica "ing. Jose Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones En Catalisis y Petroquímica "ing. Jose Miguel Parera"; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones En Catalisis y Petroquímica "ing. Jose Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones En Catalisis y Petroquímica "ing. Jose Miguel Parera"; Argentin
Intracrystalline mesoporosity over Y zeolites. Processing of VGO and resid-VGO mixtures in FCC
No full textPrototypes of FCC catalysts containing 30 %wt. Y zeolite with different intracrystalline mesoporosity generated by alkaline desilication, on an inert silica matrix, were tested in cracking a conventional vacuum gasoil (VGO) feedstock, alone and mixed with an atmospheric tower residue (ATR). The experiments were performed in a fluidized bed CREC Riser Simulator reactor (reaction time: 5-30 s, temperature: 550 °C, catalyst/feedstock: 4.5). Independently of the catalyst, the conversions of the ATR-VGO mixture were higher than those of the VGO at the same conditions. With both feedstocks, the catalyst including the zeolite with increased intracrystalline mesoporosity and higher acidity showed a higher observed activity than the catalyst with the parent zeolite. In addition, the catalyst with the modified zeolite showed higher selectivity to LCO, which is an intermediate product in FCC and a contributor to the diesel pool, especially with the ATR-VGO mixture. This effect was the consequence of the enhanced diffusion transport of primary product molecules in the zeolite pore system which, in diffusing faster, have fewer chances to be further cracked. The catalyst with higher mesoporosity showed higher coke selectivity, coke being less condensed, due to the higher free volume in the porous system allowing accommodate precursors of coke.Fil: García, Juan Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Falco, Marisa Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin
Separation of ternary hydrocarbon mixtures on Y zeolite membranes
No full textThe permeation of a mixture of n-hexane, n-decane and toluene through a 40 μm Y zeolite tubular membrane on a support with negligible resistance to the mass transfer at 250 °C was modelled based on the Maxwell-Stefan formulation and the ideal adsorbed solution theory (IAST). Individual adsorption parameters were obtained with a batch fluidized bed reactor and diffusion parameters were taken from the literature. The model allowed to predict the transient fluxes and surface coverages through the membrane, showing that the responses of the components diffusing faster (n-hexane and n-decane) overshoot their steady-state values. The permeance predictions (10-8 mol/s m2 Pa) ranged from 1.2 to 20 for n-decane, from 0.4 to 4.2 for n-hexane and from 0.8 to 4.0 for toluene, according to the feed pressure and composition. The permeance selectivities, defined with n-hexane as the reference, ranged between 3 and 6 for n-decane, and between 1 and 1.8 for toluene. It was also possible to define the association between hydrocarbon coverage profiles in the membrane and the corresponding resulting fluxes.Fil: Avila, Adolfo María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin
Immediate catalytic upgrading of soybean shell bio-oil
No full textThe pyrolysis of soybean shell and the immediate catalytic upgrading of the bio-oil over an equilibrium FCC catalyst was studied in order to define its potential as a source for fuels and chemicals. The experiments of pyrolysis and immediate catalytic upgrading were performed at 550 C during 7 min with different catalysts to oil relationships in an integrated fixed bed pyrolysis-conversion reactor. The results were compared under the same conditions against those from pine sawdust, which is a biomass source commonly used for the production of bio-oil. In the pyrolysis the pine sawdust produced more liquids (61.4%wt.) than the soybean shell (54.7%wt.). When the catalyst was presented, the yield of hydrocarbons increased, particularly in the case of soybean shell, which was four time higher than in the pyrolysis. The bio-oil from soybean shell produced less coke (between 3.1 and 4.3%wt.) in its immediate catalytic upgrading than that from pine sawdust (between 5 and 5.8%wt.), due to its lower content of phenolic and other high molecular weight compounds (three and five times less, respectively). Moreover, soybean shell showed a higher selectivity to hydrocarbons in the gasoline range, with more olefins and less aromaticthan pine sawdust.Fil: Bertero, Melisa Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin
Coprocesamiento de bio-oils en refinerías. Caracterización y pretratamiento térmico
No full textSe estudió la pirólisi de distintas biomasas (aserrín de pino, aserrín de algarrobo y cáscara de trigo) en medio inerte (N2). Los bio-oils se generaron en un reactor de lecho fijo a 550 ºC y con una rampa de 15 ºC/min. La producción más elevada de bio-oil se obtuvo para el aserrín de pino (39 %p). Los bio-oils obtenidos se analizaron por GC/MS luego de someterse a fraccionamiento con agua y éter. Las fracciones contenían principalmente aldehídos, cetonas y fenoles. Se estudió el efecto de un tratamiento térmico sobre la composición de los bio-oils, a fin de evaluar los cambios que podrían ayudar a co-procesarlos en refinerías convencionales, dado su alto potencial de formación de coque. El tratamiento térmico se realizó utilizando una rampa de 12 ºC/min y temperatura final de 500 ºC. Este tratamiento produjo una fuerte disminución en el CCR, del orden de 70 % , y un leve aumento en el contenido de agua.Fil: Bertero, Melisa Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: de la Puente, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin
Use of stirred batch reactors for the assessment of adsorption constants in porous solid catalysts with simultaneous diffusion and reaction. Theoretical analysis
No full textA simple, pseudo-equilibrium model was derived for a catalytic system with a first order chemical reaction and simultaneous diffusive and adsorptive processes, in order to assess the corresponding kinetics and Henry law's-type adsorption parameters. Solutions from this model were compared to exact solutions from a more detailed, general model. It was shown that under most of the experimental conditions used in stirred batch reactors and the usual model considerations, it is only possible to assess apparent adsorption parameters. Also, we observed that a stable relationship between the concentrations in the gas and solid phases is reached. The error produced in assuming that the apparent adsorption constant is the real one was calculated to be very important. The value of the apparent adsorption constant depends on various system properties and experimental conditions, such as the Thiele modulus, the amount of catalyst and the contact time. The ratio between the apparent and real adsorption constants was shown to be the transient effectiveness factor at any moment. This ratio reaches a maximum value for the pseudo-equilibrium state, that is always larger than the steady-state effectiveness factor, becoming closer as long as the system's adsorption capacity decreases. The analysis determines the operative conditions to reduce the parametric correlation. Also a criterion for the applicability of usual approximations in the assessment of kinetics and equilibrium adsorption parameters in porous solid catalysts by means of pulse injection methods is established.Fil: Bidabehere, Claudia María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin
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