Optimization Of Reaction Rate Parameters In Modeling Of Heavy Paraffins Dehydrogenation (original) (raw)
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International Conference on Recent Advances in Chemical Environmental and Energy Engineering, 2014
Fluidized Catalytic Cracking (FCC) units convert high molecular compounds (from atmospheric distillation and vacuum distillation units) to light gases. The major compounds in the light gases are methane, ethane, propane and butane. These light gases are then converted to highly reactive propylene (raw material for polypropylene) and butylene (raw material for butadiene and polybutadiene) via dehydrogenation. Propane and butane are always available as mixture along with traces of methane and ethane. In any commercial dehydrogenation process, the propane and butane are separated first and then dehydrogenated separately. This certainly leads to high fixed and operating costs. In this study, mixed-feed dehydrogenation of propane and butane is proposed. An isothermal model for a multi-tubular fixed bed reactor using Pt-Sn/Al 2 O 3 as a catalyst for the dehydrogenation of mixed-paraffin feed is developed considering the axial and radial variation of concentration (2D model). The 2D model is solved using central difference scheme. The simulations were carried out using MATLAB and the developed model is tested for the effect of space velocity, reactor temperature, reactor pressure, and propane to butane ratio in the feed on total paraffin conversion and olefin yield.
Modeling and Simulation of Mixed-Light Paraffin Dehydrogenation in Multi-Tubular Fixed Bed Reactor
Fluidized Catalytic Cracking (FCC) units convert high molecular compounds (from atmospheric distillation and vacuum distillation units) to light gases. The major compounds in the light gases are methane, ethane, propane and butane. These light gases are then converted to highly reactive propylene (raw material for polypropylene) and butylene (raw material for butadiene and polybutadiene) via dehydrogenation. Propane and butane are always available as mixture along with traces of methane and ethane. In any commercial dehydrogenation process, the propane and butane are separated first and then dehydrogenated separately. This certainly leads to high fixed and operating costs. In this study, mixed-feed dehydrogenation of propane and butane is proposed. An isothermal model for a multi-tubular fixed bed reactor using Pt-Sn/Al 2 O 3 as a catalyst for the dehydrogenation of mixed-paraffin feed is developed considering the axial and radial variation of concentration (2D model). The 2D model ...
Chemical Engineering & Technology, 2015
Catalytic paraffin dehydrogenation for manufacturing olefins is considered to be one of the most significant production routes in the petrochemical industries. A reactor kinetic model for the dehydrogenation of propane to propylene in a radial-flow reactor over Pt-Sn/Al 2 O 3 as the catalyst was investigated here. The model showed that the catalyst activity was highly time dependent. In addition, the component concentrations and the temperature varied along the reactor radius owing to the occurring endothermic reaction. Moreover, a similar trend was noticed for the propane conversion as for the propylene selectivity, with both of them decreasing over the time period studied. Furthermore, a reversal of this trend was also revealed when the feed temperature was enhanced or when argon was added into the feed as an inert gas.
Applied Catalysis A: General, 2019
A kinetic modeling study on long chain n-paraffin dehydrogenation using a commercial Pt-Sn-K-Mg/γ-Al 2 O 3 catalyst was carried out in a continuous flow setup using n-dodecane as a model component at various temperatures (450-470°C), pressures (0.17-0.30 MPa), H 2 /paraffin mole ratios (3:1-6:1) and space times (0.22-1.57 g h mol −1). The commercial catalyst was characterized by XRD, BET, MIP, SEM and CO chemisorption. An empirical exponential equation was found to predict the mono-and di-olefin yields very well. In addition, 6 mechanistic models based on the LHMW mechanism were derived and tested by non-linear least squares fitting of the experimental data. The model which assumes that surface reactions and particularly the dehydrogenation of the metal-alkyl chain to the adsorbed mono-olefin and di-olefin as the rate determining steps was found to give the best fit with the experimental data. In addition, activation energies and adsorption enthalpies for each elementary reaction were obtained. The kinetic testing and modeling have shown that the high mono-olefins selectivity for long chain paraffin dehydrogenation can be obtained by operating at low space time (when P, T and m are same), high pressure (when τ, T and m are same) and high H 2 /paraffin ratio (when τ, P and T are same), as well as low reaction temperature (when τ, P and m are same) but with little effect. Recently, a Pt-Sn-K-Mg/γ-Al 2 O 3 catalyst has been commercialized in PetroChina, PR China [18], which is characterized by longer lifetime (72 vs. 58 days), higher operation temperature (490 vs. 481°C) and higher daily production (333.6 vs. 321.5 tons day −1), as compared to Pt-Sn-K/γ-Al 2 O 3 catalyst. The better performance of Pt-Sn-K-Mg/γ-Al 2 O 3 catalyst was attributed to the higher mechanical strength and better thermal stability of Mg-Al-O support, as well as the moderated
Applied Catalysis A: General, 2019
A kinetic modeling study on long chain n-paraffin dehydrogenation using a commercial Pt-Sn-K-Mg/γ-Al 2 O 3 catalyst was carried out in a continuous flow setup using n-dodecane as a model component at various temperatures (450-470°C), pressures (0.17-0.30 MPa), H 2 /paraffin mole ratios (3:1-6:1) and space times (0.22-1.57 g h mol −1). The commercial catalyst was characterized by XRD, BET, MIP, SEM and CO chemisorption. An empirical exponential equation was found to predict the mono-and di-olefin yields very well. In addition, 6 mechanistic models based on the LHMW mechanism were derived and tested by non-linear least squares fitting of the experimental data. The model which assumes that surface reactions and particularly the dehydrogenation of the metal-alkyl chain to the adsorbed mono-olefin and di-olefin as the rate determining steps was found to give the best fit with the experimental data. In addition, activation energies and adsorption enthalpies for each elementary reaction were obtained. The kinetic testing and modeling have shown that the high mono-olefins selectivity for long chain paraffin dehydrogenation can be obtained by operating at low space time (when P, T and m are same), high pressure (when τ, T and m are same) and high H 2 /paraffin ratio (when τ, P and T are same), as well as low reaction temperature (when τ, P and m are same) but with little effect. Recently, a Pt-Sn-K-Mg/γ-Al 2 O 3 catalyst has been commercialized in PetroChina, PR China [18], which is characterized by longer lifetime (72 vs. 58 days), higher operation temperature (490 vs. 481°C) and higher daily production (333.6 vs. 321.5 tons day −1), as compared to Pt-Sn-K/γ-Al 2 O 3 catalyst. The better performance of Pt-Sn-K-Mg/γ-Al 2 O 3 catalyst was attributed to the higher mechanical strength and better thermal stability of Mg-Al-O support, as well as the moderated
Light paraffins dehydrogenation in a fluidized bed reactor
Catalysis Today, 1999
The FBD-4 (¯uid bed dehydrogenation) technology for the dehydrogenation of isobutane to isobutene is described, including the scenario in which the development of this technology was decided and the scale-up procedure used. The paper is then particularly focused on the efforts to develop a reliable mathematical model for design and simulation of the¯uid bed reactor. # 0920-5861/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 0 -5 8 6 1 ( 9 9 ) 0 0 0 8 0 -2
Reactor performance and stability in an alternating reaction-reheat paraffin dehydrogenation system
The Canadian Journal of Chemical Engineering, 1996
The classical fixed bed C3-C4 paraffin dehydrogenation process is a cyclic operation in which the reactor alternates between reaction and reheat cycles. During the reheat cycle, the necessary energy for the dehydrogenation reaction is stored in the fixed bed by passing hot air through it. In this established technology, both the hydrocarbon reactant and the reheat hot air are fed into the fixed bed from the same end (top) of the reactor. This is termed parallel flow (cocurrent) operation. An alternative feeding fixed bed has the hydrocarbon reactant and the reheat air entering from the opposite ends of the reactor. This is termed reverse flow (countercurrent) operation. This alternate creates an ideal temperature profile for an equilibrium limited endothermic reaction (rising temperature profile along the reactor). The transient flow behavior of both parallel and reverse flow reactors has been modelled and the dynamics of temperature profile development for both concepts have been analyzed. Based upon the model predictions, the characteristics as well as the reactor stability of the both concepts have been discussed. ~~ Le procede classique de deshydrogenation des paraffines C,-C, en lit fixe est un procede cyclique dans lequel le reacteur alterne entre le mode reactif et les cycles de rechauffement. Durant le cycle de rechauffement, I'energie necessaire pour la reaction de deshydrogenation est emmagasinee dans le lit fixe par de l'air chaud circulant dans le lit. Dans cette technologie qui est bien etablie, le reactif d'hydrocarbure et I'air chaud entre dans le lit fixe par la mCme extremite (superieure) du reacteur. On parle alors d'ecoulement parallele (cocourant). Une autre methode d'alimentation du lit consiste a entrer le reactif d'hydrocarbure et l'air de rechauffement par les extremites opposees du lit. II s'agit d'un I'ecoulement inverse (a contre-courant). Cette maniere de proceder donne un profil de temperature ideal pour une reaction endothermique limitee a I'equilibre (profil de temperature augmentant le long du reacteur). On a modelise le comportement en ecoulement transitoire des reacteurs a ecoulement parallele et inverse et analyse la dynamique du developpement du profil de temperature pour les deux concepts. Les caracteristiques et la stabilite du reacteur pour les deux concepts sont analysees a partir des predictions du modele.
Fuel, 2012
The dehydrogenation of C 12-C 14 paraffins on PtCu/meso-structured Al 2 O 3 catalysts for linear alkylbenzene (LAB) production was simulated to evaluate the effect of process variables. The new process consisted of a first stage where the paraffin is desulfurized, followed by second stage that used a novel dehydrogenation catalyst operating at high pressure and low temperature in trickle bed reactor. The dehydrogenation took place in the presence of an aromatic solvent, which helped control the catalyst deactivation. The process was modeled using Excel with a macro written in VB6. The hydrogen, C 12 and benzene concentration in liquid phase was calculated using the Peng Robinson state equation. The kinetic rates and deactivation constants were previously determined and verified here with independent experiments. Analysis of mass and heat transfer controls indicated the presence of important diffusional limitations of the reactions in the pores at the inlet of the reactor operating conditions. The simulation confirmed that the system operates with low conversion ($14-20%) and high selectivity, with only moderate deactivation. The use of a swing reactor helped to extend the cycle length without deteriorating the selectivity for one year cycle length commercial application; several options were evaluated to optimize the reactors system.
Chemical Engineering Science, 1994
Methylcyclohexane (MCH) has been proposed as a potentially attractive vector for hydrogen storage. For use in transportation, hydrogen when stored as MCH, needs to he liberated by dehydrogenation (endothermic reaction) in a compact catalytic reactor. By coupling the reactor with the engine, the waste heat could be utilized to run the reaction. Industrial Pt-Sn]Al203 catalyst was chosen as suitable for the reaction_ In this paper, a global model for the performance of the dehydrogenation reactor is developed. This model combines the kinetic models for the MCH dehydrogenation, and for the deactivation of the industrial Pt-Sn/AI203 catalyst, and the bidimensional model for a tubular reactor. In addition, new experimental data, compared with those predicted by the global model are presented.