Accessibility of hydrocarbons into USY zeolites and its effect in the hydrocracking reaction

En este trabajo se estudió el impacto de las propiedades físicas y químicas de las zeolitas USY en el proceso de hydrocracking de hidrocarburos pesados orientado hacia su accesibilidad en zeolitas USY. Las propiedades texturales y morfológicas de las zeolitas USY fueron medidas usando fisisorción de N2, Difracción de Rayos X (DRX), y Microscopía Electrónica de Transmisión (TEM). La acidez de las zeolitas USY fue caracterizada usando quimisorción de piridina medido por espectroscopía infrarroja (FTIR), y quimisorción de isopropilamina medida por análisis termogravimétrico (TGA). La actividad catalítica de catalizadores de platino soportados en zeolitas USY y en soportes no ácidos en el hydrocracking no isotérmico de fluoreno se estudió empleando un analizador térmico simultáneo de alta presión (STA-HP). El hydrocracking no isotérmico en un STA-HP permitió observar de forma cualitativa los pasos de la reacción del hydrocracking. Además, el test evidenció la necesidad de sitios ácidos Brønsted (BAS) en el hydrocracking, mostrando correlaciones positivas entre la entalpía de hydrocracking y la concentración de BAS. Un segundo test consistió en estudiar el hydrocracking de fenantreno usando un reactor Trickle-Bed a diferentes temperaturas. La participación de los BAS a distintas temperaturas fue calculada mediante el Turn-Over Frequency (TOF). El cálculo del TOF permitió correlacionar las propiedades estructurales de las zeolitas USY con su actividad catalítica hacia hydrocracking. Zeolitas con altos volúmenes de mesoporo reportaron más alto TOF de los BAS debido al mejor acceso del fenantreno al interior de las zeolitas. La accesibilidad del fenantreno en zeolitas USY se puede mejorar mediante el uso de agentes de lavado del aluminio amorfo. Mejorar la accesibilidad en las zeolitas USY favorece la actividad catalítica hacia reacciones de hydrocracking y cracking considerablemente, además de favorecer las reacciones de hidrogenación. (Texto tomado de la fuente)The present work is a comprehensive study of the effect of the physical and chemical properties of USY zeolites in the heavy hydrocarbons hydrocracking reaction. The study addresses USY zeolites accessibility for heavy hydrocarbons. Structural and morphological properties of USY zeolites were measured using nitrogen physisorption, X-Ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). The acidity of USY zeolites was characterized using pyridine chemisorption recorded by FTIR, and isopropylamine chemisorption recorded by Thermogravimetric Analysis (TGA). The activity of platinum catalysts supported on USY zeolite and non-acidic support in non-isothermal fluorene hydrocracking was studied in a High-Pressure Simultaneous Thermal Analyzer (HP-STA). Non-isothermal hydrocracking of fluorene allows qualitative observation of the reaction paths over bifunctional catalysts. Besides, catalytic tests proved a positive correlation between hydrocracking enthalpy and BAS concentration. A second catalysis test studied phenanthrene hydrocracking using a Trickle-Bed Reactor (TBR) at different temperatures. BAS participation in the reaction was estimated by means of the Turn-Over Frequency (TOF). USY zeolites with high mesoporous volume showed high TOF of BAS indicating good accessibility of zeolite active sites for phenanthrene molecules. USY zeolites accessibility for phenanthrene can be improved by using chemical agents for amorphous aluminum oxides remotion. Improving the accessibility of USY zeolites favors catalytic activity towards hydrocracking and cracking reactions considerably. Moreover, improved accessibility benefits the hydrogenation reaction by shifting the chemical equilibrium towards the right direction.MincienciasDoctoradoDoctor en IngenieríaPhenanthrene hydrocracking reaction was carried out in (0.85 %wt)Pt/[(40 %wt)USY-γ-Al2O3] catalysts, using three different USY zeolites supports (CBV600, CBV720, and CBV780). The reactions were carried out in a tubular continuous Trickle bed reactor. TBR employed 0.15 g of catalyst diluted in 1.5 g of silicon carbide (SiC) through which flowed 1 mL/min of liquid phenanthrene solution and 10 mL/min of H2 gas flowed. Test reactions were performed at three temperatures: 270 °C, 285 °C, and 300 °C, and 70 bar of pressure. At those operational conditions, phenanthrene solution is kept in the liquid phase. Liquid samples were taken each 30 minutes, and when the temperature was changed, the interval between sampling was 1 h to guarantee that the system achieves stability. Finally, to study the effect of γ-Al2O3 in the reaction, the same reaction was carried out using a (0.85 wt%)Pt/γ-Al2O3 catalyst. All liquid samples were analyzed using a GC Hewlett Packard 5890 series II coupled with an FID detector. For compound separation, a nonpolar DB-5 capillary column (50 m) has been installed. FID detector was calibrated by a curve that correlates the response area of the FID with the concentration of the phenanthrene. Liquid products were also analyzed by gas chromatography coupled to mass spectroscopy (GC-MS) carried out by a collaborator at the Corporación Autonoma Regional de Cundinamarca (CAR). The method of chromatographic separations was identical for both detectors, FID and MS.Catálisis heterogénea y generación de energí