Computational fluid dynamics study of crec riser simulator: mixing patterns

The CREC Riser Simulator Reactor is a novel mini-fluidized reactor. This novel device was invented by de Lasa 1. The applications of this unit has shown to be of great value to establish catalyst performance and kinetic models for a diversity of gas phase catalytic reactions. This has been the case, given that the CREC Riser Simulator is excellent with respect to particle and fluid mixing2. This study establishes using CFD (Computational Fluid Dynamics), the CREC Riser Simulator mixing flow patterns. CFD simulations were developed using the COMSOL Multiphysics® module. Fig.1a reports the geometric characteristics of the CREC Riser Simulator including the impeller, the basket containing the catalyst and the external baffles.The proposed CFD model was validated using experimental data obtained in a basket as shown in Fig.1a. For instance, for an impeller speed of 4000 rpm, the outer annulus experimental gas velocity2 was ~0.9 m/s and the simulated CFD gas velocity2 was ~1.3 m/s. Please click Additional Files below to see the full abstract

Steam promoted mesoporosity in USY zeolites: Structural properties and 1,2,4-TMB reactivity

This work addresses the potential effects of steaming in the case of dealumination of Y zeolites. With this end, the interaction between 1,2,4-trimethylbenzene (1,2,4-TMB) and ultrastable Y zeolite (USY) is analyzed. The zeolite is modeled using the complete exposed USY structure of one unit cell constituted by eight sodalite cages, 16 hexagonal prisms bridging the sodalite cages and the formed supercage. The MM2 method is considered to evaluate the steric energies in a model of the window including the six surrounding complete sodalite cages. The Parametrized Model revision 3 (PM3) method is also used to analyze the changes in enthalpy upon 1,2,4-TMB adsorption and reaction on each cage. Finally, several calculations on the adsorption of the 1,2,4-TMB on different sodalite cages are effected using the Extended Hückel method and this to complete the description about the interactions between the crystalline USY and 1,2,4-TMB molecules. Calculation results reported in this work support the high probability of carbocation formation and overall reaction in fragments removed from the zeolite. This partially destroyed zeolite display some relaxation of the original structure and allows extra accessibility of TMB to the acidic sites.Fil: Tonetto, Gabriela Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: Ferreira, María Luján. Universidad Nacional del Sur. Departamento de Ingeniería Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: de Lasa, Hugo I.. University of Western Ontario; Canad

Butane dehydrogenation on vanadium supported catalysts under oxygen free atmosphere

The present study investigates the catalytic n-butane dehydrogenation under oxygen free atmosphere using VOx supported on USY, NaY, γ-Al2O3 and α-Al2O3. Experiments are developed at 520°C in a fixed bed microreactor. Catalyst characterization via TPR demonstrates the presence of different VOx species with the nature of these species being a function of the catalyst support. The acidic properties of the prepared catalysts are also evaluated using NH3 TPD with the following order of acidity being observed: VOX/γ-Al2O3 > VOxM/α- Al2O3 > VOx/USY. Reactivity experiments show that the VOx/USY provides both the highest catalytic activity and butane selectivity, with the VOx/γ-Al2O3 displaying a lower activity and butane selectivity and the other tested catalyst samples being essentially inactive. The superior performance of the VO x/USY catalyst is assigned to its mild acidity.Fil: Volpe, María Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Tonetto, Gabriela Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. University of Guelph. Biodiversity Institute of Ontario; CanadáFil: De Lasa, Hugo I.. University of Western Ontario; Canad

Coke Formation over a Nickel Catalyst under Methane Dry Reforming Conditions: Thermodynamic and Kinetic Models

The CO2 reforming of methane is studied over a 20 wt% Ni/USY-zeolite, and more specifically, a thermodynamic analysis of the formation of coke is used as a basis for the kinetic modeling of coke phenomena that exist under dry reforming conditions. Two thermodynamic parameters, α and β, are compared to the equilibrium constants for the CH 4 decomposition and the CO disproportionation reactions and defined to determine whether coke formation is favored. This thermodynamic analysis elucidates the significance of the CO disproportionation reaction on the amount of coke deposited over the catalyst under consideration. A kinetic model with negative overall order of one, with respect to the partial pressure of carbon monoxide, is found as the most accurate prediction of the rate of coke formation. This type of kinetics strongly suggests the requirement of three adjacent free catalyst sites for the coking reaction to proceed under allowable thermodynamic conditions.Fil: Ginsburg, Jason M.. University of Western Ontario; CanadáFil: Piña, Juliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: El Solh, Tarek. Imperial Oil Research Center; CanadáFil: De Lasa, Hugo I.. University of Western Ontario; Canad