Cross-Flow Naphtha Reforming in Stacked-Bed Radial Reactors with Continuous Solid Circulation: Catalyst Deactivation and Solid Circulation between Reactors

A naphtha-reforming reactor system, consisting of four stacked-bed reactors with cross-flow of gas and circulation of catalyst, was simulated. Commercial and micropilot plant data were used to adjust the kinetics and deactivation constants, based on previous results obtained in fixed-bed operations with another catalyst. The simulation of radial commercial reactors was performed using mixing zones for the intervessel solid transfer and a second zone through which the solids move downward and within which reactions take place. The mass and energy differential equations were solved in the radial and axial direction point by point, using the Runge–Kutta–Fehlberg (RKF) numerical method. The effects of solid mixing on catalyst profiles of coke were determined in a cold model. Sequential deactivation and partial mixing tests were performed to verify their effects on catalyst activities. Spent catalysts were characterized and tested under different operating conditions. The feed and reformate were characterized using an extended PIONA-MS method to obtain additional information about the isomers for different carbon numbers. Temperature, yields, activities and pressure are predicted by the model and compared to commercial data. The results show the importance of considering the effect of solid mixing, the two-dimensional pressure-drop temperature, and the variation in catalyst activity across and along the reactors

Catalyst Deactivation during Upgrade of Light Catalytic Cracking Gas Oil to Ultralow-Sulfur and Low-Aromatic Diesel

Diesel fuels containing 50 and 15 ppm sulfur were produced in a pilot plant by upgrading light catalytic cracking gas oil (LCO) during 10 weeks of continuous operation. At the end of the run, the catalysts were characterized before and after soluble coke extraction by CH₂Cl₂. The cokes were characterized by ¹³C NMR, TPO, GC-MS, and elemental analysis. Catalyst surfaces were characterized by XPS, CO adsorption, pyridine adsorption, and chemical reactions. The results indicate important differences in the amount and composition of soluble coke recovered from the two deactivated catalysts. In the two cases, the soluble coke affected the accessibility of catalytic active sites in different ways. Catalyst deactivation was higher, and the rate of ring opening was lower, under the more severe hydrotreatment conditions needed to produce fuel with 15 ppm sulfur, compared to the conditions required for production of fuel with 50 ppm sulfur

Solid Catalyst Alkylation of C₂–C₃ Olefins with Isobutane in the Presence of Hydrogen Using a Slurry Transport Reactor–Hydrocyclone-Regenerator System and PtSO₄TiZr/SiO₂ Catalyst: Part 1. Alkylation in Continuous Pilot Plant Operation and Simulation of a Slurry Transport Reactor–Hydrocyclone Settler System

A continuous alkylation plant was simulated to evaluate the capability of a newly designed acid solid catalyst PtSO₄TiZr/SiO₂ to convert light olefins (C₂ and C₃) and isobutane into alkylate in the presence of hydrogen. This part of the process consists in a three-phase slurry transport reactor (STR) and a hydrocyclone settler (HCS) operating in series with the recycling of unconverted reactant and regenerated and fresh catalysts. Data for alkylation were obtained in batch reactor and in pilot plant tests at different gas flow rates, temperatures, pressures, and catalyst particle sizes. Kinetic and deactivation rates and fluid dynamic data were obtained using the pilot plant continuous operation. Fresh, spent, and regenerated catalyst were characterized using different techniques to explain its selectivity and deactivation. Commercial size plant was designed and then simulated to determine the impacts STR operating variables in the alkylate cost. The study determined the kinetic and deactivation rates parameter for the main reactions as well as the effect of operating variables and particle size in the performance of the catalysts. Simulation provides information with which to discuss the behavior of STR reactor and the impacts of the operating variables in the cost of alkylate. The rates of apparent in-series alkylate production depend on order 1 in intermediates and olefin concentration, catalyst activity, and rate of diffusion in mesopores; the rates of soluble coke production depend on order 1 in intermediaries and 1.5 in olefin concentration and is inversely proportional to hydrogen partial pressure. The kinetic and deactivation model is independent of the reactor used. Catalyst aged with the number of cycles of alkylation and regeneration; its activity is inversely proportional to the soluble coke content. Inlet temperature, olefins-to-isobutene mole ratio, hydrogen-to-olefins mole ratio, and catalyst makeup are the main operational variables that impact the cost of alkylate. Sensitivity to kinetic rate parameters, fluid dynamic model, and particle size are analyzed. There is an optimal coke build-up in solid alkylation that minimizes the alkylate cost

Solid Catalyst Alkylation of C₂–C₃ Olefins with Isobutane in the Presence of Hydrogen Using a Slurry Transport Reactor–Hydrocyclone–Regenerator System and PtSO₄TiZr/SiO₂ Catalyst: Part 2. Regeneration of Spent Catalysts in Pilot Plants and a Simulation of a Fluidized Bed Reactor

A continuous regeneration process was developed to treat spent PtTiZrSO₄/SiO₂ alkylation catalyst with hydrogen in a fluidized-bed reactor. Catalyst that alkylated isobutane with olefins (C₂⁼ and C₃⁼) in a pilot plant accumulated soluble and insoluble coke on the surface in several passes through the system. It was regenerated on a small scale and in a pilot plant fluidized-bed reactor (FBR). Tests in semibatch reactors generated data to develop the apparent kinetic rate and the stoichiometry of the reaction. The information obtained in the pilot plant was used to determine fluid dynamic correlations, a new set of kinetic rate constants, the number of compartments in the dense phase, and the catalyst efficiency factor and to confirm the effects of operating variables. Simulations of the pilot plant and commercial size fluidized-bed reactor were performed using three fluid dynamic models, the kinetic rate equation, and the new fluid dynamic correlations. The effect of operating variables in alkylation cost were analyzed for a commercial-size reactor and auxiliary equipment, integrated to the alkylation and fractionation stages of the process. The results indicated that apparent hydrocracking rate of soluble coke follows an order of 1 in soluble coke and 0.5 in hydrogen in the range of 60 to 80% of coke conversion. Soluble coke aged with the number of passes. Hold-up, bubble size and frequencies, and solid backmixing measured in hydrogen at high pressure and temperature are different than those in air. A new set of fluid dynamic equations were determined. The continuous operation of the pilot plant confirms the effect of operating variables in soluble-coke conversion. The best fit of pilot plant coke conversion was obtained using a model composed of 1 compartment at the inlet, 10 compartments for the bubble moving up, and 2 compartments in series for the dense phase; the last two zones are connected by a cross-flow. The simulation of the integration process, alkylation regeneration, determines that 533 K and a gas residence time of 0.2 h produce the minimum alkylate cost. Alkylate cost is driven by the amount of soluble coke formed and regenerated