Simulation of Propane Dehydrogenation to Propylene in a Radial-Flow Reactor over Pt-Sn/Al2O3as the Catalyst (original) (raw)

3 rd Determination of Operational Condition for Propane Dehydrogenation over a Commercial Pt- Sn-K/Al 2 O 3 Catalyst

2010

2 O 3 ; Propylene production One of the important light alkenes as an advantageous intermediate in the manufacture of polyme s and chemicals is propylene. Nowadays, most of propylene is generated as a byproduct o f gaso line production; therefore, the gasoline market demands determine the quantity of pro pylene production. Catalytic dehydrogenatio n of the pro pane is the most selective and conventional route to pro duce this short-chain alkene which has the potential to compensate the sho rtfall o f propylene left by gasoline plants. Industrial dehydrogenation processes use platinum-based catalysts generally supported on alumina and promo ted h Sn. The biggest dehydrogenation unit in Iran has been established in MTBE plant o f BIPC (Bandar Imam Petrochemical Complex) which producing Isobutene from Isobutane by exploiting a commercial catalyst: Pt-Sn-K/Al 2 O 3 (DP-803). In order to feasibility study of propylene pro ductio n rather than Isobutene in this plant, as a prim ary study, some bench-scale reaction tests were perfo rmed on the mentioned catalyst with H 2 /C 3 H 8 as reactants. Fo r the purpose of obtaining the operational conditions, 6 g catalyst were packed in a fixed-bed quartz reactor with the ID o f 10 mm and the length of 62 cm, and then reduced in mixed H 2 /N 2 with a kind of stepwise method. The effects of temperature, WHSV and H 2 /C 3 H 8 ratio were investigated on conversion and yield of propylene. Designing o f the experiments by choosing of one parameter at a time method, 27 runs were accomplished under the reaction temperature range o f 610 to 630 ? C, WHSVs of 2 to 4, H 2 /C 3 H 8 ratio s of 0.6 to 0.8; and atmospheric pressure. Acco rding to data analysis and obtained results, conversion of reactants, yield o f propylene on Pt-Sn-K /Al 2 O 3 (DP-803) attained a maximum value at 34%, when the operational condition were 630 ? C, H 2 /C 3 H 8 = 0.6; and WH SV= 3 hr -1 . γ γ 3

An investigation on the role of a Pt/Al2O3 catalyst in the oxidative dehydrogenation of propane in annular reactor

Journal of Catalysis, 1999

Oxidative dehydrogenation of propane was studied over a commercial Pt/γ-Al 2 O 3 catalyst using an annular reactor, wherein high space velocities (referred to the catalyst load) and controlled temperature conditions can be realized. The reaction was studied in a wide temperature range. Tests in the presence of the catalyst showed that up to 500 • C, only products of combustion were produced; above this temperature olefins were also formed in large amounts. Comparison with additional experiments which were carried out in the absence of the catalyst showed that: (1) the oxidation of propane at low to medium temperatures was purely catalytic; the reaction rate was so fast that in the present annular reactor the catalytic combustion underwent interphase mass transfer control already at 200 • C oven T; (2) above 500 • C gas-phase oxidative pyrolysis of propane was active and could explain the formation of olefins observed in the catalytic tests. Tests of sensitivity of the product yields upon variation of the catalyst load were performed; while the yields of CO 2 , CO, H 2 O, and H 2 increased with increasing amount of catalyst, the yields of propylene, ethylene, and methane decreased progressively. No positive evidence of heterogeneous formation of olefins was thus provided by the various experiments. The data were coherent with a homogeneous formation of propylene and ethylene.

Influence of the deactivation of an industrial Pt-Sn/Al2O3 catalyst on the performance of the dehydrogenation reactor

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.

Kinetics of long chain n-paraffin dehydrogenation over a commercial Pt-Sn-K-Mg/γ-Al2O3 catalyst: model studies using n-docedane

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

Kinetics of long chain n-paraffin dehydrogenation over a commercial Pt-Sn-K-Mg/γ-Al2O3 catalyst: Model studies using n-dodecane

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

Study of the Effects of External and Internal Diffusion on the Propane Dehydrogenation Reaction over Pt-Sn/Al2O3 Catalyst

Chemical Engineering & Technology, 2007

In the study of a reaction on a heterogeneous catalyst, external and internal mass diffusion play an important role since they can have an inherent affect on the kinetics of the reaction. Therefore, in the study of intrinsic rates of reaction, the effects of external and internal mass diffusion must be eliminated or considered prior to proper kinetic studies. In this study, the effects of external and internal mass diffusion on the propane dehydrogenation reaction over a Pt/Sn catalyst were investigated. Some experiments were performed in a laboratory scale setup and the required data was gathered. The rate of reaction was considered to be first order based on propane. External diffusion was studied using Mears' criterion and internal diffusion was investigated by the Thiele Module and the Internal Effectiveness Factor, based on experimental data.

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 ...

Optimization Of Reaction Rate Parameters In Modeling Of Heavy Paraffins Dehydrogenation

2011

In the present study, a procedure was developed to determine the optimum reaction rate constants in generalized Arrhenius form and optimized through the Nelder-Mead method. For this purpose, a comprehensive mathematical model of a fixed bed reactor for dehydrogenation of heavy paraffins over Pt–Sn/Al2O3 catalyst was developed. Utilizing appropriate kinetic rate expressions for the main dehydrogenation reaction as well as side reactions and catalyst deactivation, a detailed model for the radial flow reactor was obtained. The reactor model composed of a set of partial differential equations (PDE), ordinary differential equations (ODE) as well as algebraic equations all of which were solved numerically to determine variations in components- concentrations in term of mole percents as a function of time and reactor radius. It was demonstrated that most significant variations observed at the entrance of the bed and the initial olefin production obtained was rather high. The aforementioned...

Modeling and Simulation of Mixed-Light Paraffin Dehydrogenation in a Multi-tubular Packed bed Reactors

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.

Effect of Reduction of Pt–Sn/α-Al2O3 on Catalytic Dehydrogenation of Mixed-Paraffin Feed

Catalysts, 2020

The effect of the Pt-Sn/α-Al 2 O 3 catalyst reduction method on dehydrogenation of mixed-light paraffins to olefins has been studied in this work. Pt-Sn/α-Al 2 O 3 catalysts were prepared by two different methods: (a) liquid phase reduction with NaBH 4 and (b) gas phase reduction with hydrogen. The catalytic performance of these two catalysts for dehydrogenation of paraffins was compared. Also, the synergy between the catalyst reduction method and mixed-paraffin feed (against individual paraffin feed) was studied. The catalysts were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) analysis. The individual and mixed-paraffin feed dehydrogenation experiments were carried out in a packed bed reactor fabricated from Inconel 600, operating at 600 • C and 10 psi pressure. The dehydrogenation products were analyzed using an online gas chromatograph (GC) with flame ionization detector (FID). The total paraffin conversion and olefin selectivity for individual paraffin feed (propane only and butane only) and mixed-paraffin feed were compared. The conversion of propane only feed was found to be 10.7% and 9.9%, with olefin selectivity of 499% and 490% for NaBH 4 and hydrogen reduced catalysts, respectively. The conversion of butane only feed was found to be 24.4% and 23.3%, with olefin selectivity of 405% and 418% for NaBH 4 and hydrogen reduced catalysts, respectively. The conversion of propane and butane during mixed-feed dehydrogenation was measured to be 21.4% and 30.6% for the NaBH 4 reduced catalyst, and 17.2%, 22.4% for the hydrogen reduced catalyst, respectively. The olefin selectivity was 422% and 415% for NaBH 4 and hydrogen reduced catalysts, respectively. The conversions of propane and butane for mixed-paraffin feed were found to be higher when compared with individual paraffin dehydrogenation. The thermogravimetric studies of used catalysts under oxygen atmosphere showed that the amount of coke deposited during mixed-paraffin feed is less compared with individual paraffin feed for both catalysts. The study showed NaBH 4 as a simple and promising alternative reduction method for the synthesis of Pt-Sn/Al 2 O 3 catalyst for paraffin dehydrogenation. Further, the studies revealed that mixed-paraffin feed dehydrogenation gave higher conversions without significantly affecting olefin selectivity.