Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 31103
Optimization of Reaction Rate Parameters in Modeling of Heavy Paraffins Dehydrogenation

Authors: Leila Vafajoo, Farhad Khorasheh, Mehrnoosh Hamzezadeh Nakhjavani, Moslem Fattahi


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 method utilized a direct-search optimization algorithm along with the numerical solution of the governing differential equations. The usefulness and validity of the method was demonstrated by comparing the predicted values of the kinetic constants using the proposed method with a series of experimental values reported in the literature for different systems.

Keywords: Modeling, Optimization, dehydrogenation, Pt-Sn/Al2O3 Catalyst, Nelder-Mead

Digital Object Identifier (DOI):

Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2370


[1] George A. Olah, Hydrocarbon Chemistry, John Wiley, New York, 2002.
[2] N. A. Gaidai, S. L. Kiperman, Kinetic Models of Catalyst Deactivation in Paraffin Dehydrogenation, Kinetics and Catalysis 42 (2001) 527-532.
[3] Maryam Saeedizad, Saeed Sahebdelfar, Zahra Mansourpour, Deactivation kinetics of platinum-based catalysts in dehydrogenation of higher alkanes, Chemical Engineering Journal 154 (2009) 76-81.
[4] Victor K. Shum, John B. Butt, Wolfgang M. H. Sachtler, The effects of rhenium and sulfur on the activity maintenance and selectivity of platinum/alumina hydrocarbon conversion catalysts, Journal of Catalysis 96 (1985) 371-380.
[5] Robert W. Coughlin, Koei Kwakami, Akram Hasan, Activity, yield patterns, and coking behavior of Pt and PtRe catalysts during dehydrogenation of methylcyclohexane: I. In the absence of sulfur, Journal of Catalysis 88 (1984) 150-62.
[6] M. J. Dees, V. Ponec, On the influence of sulfur on the platinum/iridium bimetallic catalysts in n-hexane/hydrogen reactions, Journal of Catalysis 115 (1989) 347-355.
[7] J. Barbier, P. Marecol, Effect of presulfurization on the formation of coke on supported metal catalysts, Journal of Catalysis 102 (1986) 21- 28.
[8] M.J. Dess, V. Ponec, The influence of sulfur and carbonaceous deposits on the selectivity and activity of Pt/Co catalysts in hydrocarbon reactions, Journal of Catalysis 119 (1990) 376-387.
[9] G. Padmavathi, K. K. Chaudhuri,, D. Rajeshwer, G. Sreenivasa Rao, K.R. Krishnamurthy, P.C. Trivedi, K. K. Hathi, N. Subramanyam, Kinetics of n-dodecane dehydrogenation on promoted platinum catalyst, Chemical Engineering Science 60 (2005) 4119-4129.
[10] M. M. Bhasin, J.H. McCain, B.V. Vora, T. Imai, P.R. Pujado, Dehydrogenation and oxydehydrogenation of paraffins to olefins, Applied Catalysis A: General 221 (2001) 397-419.
[11] Joseph A. Kocal, Bipin V. Vora, Tamotsu Imai, Production of linear alkylbenzenes, Applied Catalysis A: General 221 (2001) 295-301.
[12] S. D. Harris, L. Elliott, D. B. Ingham, M. Pourkashanian, C. W. Wilson, The optimisation of reaction rate parameters for chemical kinetic modelling of combustion using genetic algorithms, Computer Methods in Applied Mechanics and Engineering 190 (2000) 1065-1090
[13] André Bardow, Wolfgang Marquardt, Incremental and simultaneous identification of reaction kinetics: methods and comparison, Chemical Engineering Science 59 (2004) 2673-2684
[14] G. S. G. Beveridge, R. S. Schechter, Optimization: Theory and Practice, New York: McGraw-Hill, 1970.
[15] H. Rabitz, M. Kramer, D. Dacol, Sensitivity Analysis in Chemical Kinetics, Annual Review of Physical Chemistry 34 (1983) 419-461.
[16] Herschel Rabitz, Chemical sensitivity analysis theory with applications to molecular dynamics and kinetics, Computers & Chemistry 5 (1981) 167-180.
[17] Robert Michael Lewis, Virginia Torczon, Michael W. Trosset, Direct search methods: then and now, Journal of Computational and Applied Mathematics 124 (2000) 191-207.
[18] Erwie Zahara, Yi-Tung Kao, Hybrid Nelder-Mead simplex search and particle swarm optimization for constrained engineering design problems, Expert Systems with Applications 36 (2009) 3880-3886.
[19] Rachid Chelouah, Patrick Siarry, Genetic and Nelder-Mead algorithms hybridized for a more accurate global optimization of continuous multiminima functions, European Journal of Operational Research 148 (2003) 335-348.
[20] C. J. Price, I. D. Coope, D. Byatt, A Convergent Variant of the Nelder- Mead Algorithm, Journal of optimization theory and applications 113 (2002) 5-19.
[21] R. Nakamura, M. Shimoji, H. Niiyama, Strategies for using a computeroperated reaction system for the evaluation of catalyst activity by optimization of product yield, Catalysis Today 10 (1991) 119-129.
[22] Jeffrey C. Lagarias, James A. Reeds, Margaret H. Wright, Paul E. Wright, Convergence properties of the Nelder-Mead simplex method in low dimensions, SIAM Journal of Optimization 9 (1998) 112-147.
[23] Marco A. Luersen, Rodolphe Le Riche, Globalized Nelder-Mead method for engineering optimization, Computers and Structures 82 (2004) 2251-2260.
[24] Julian Martinez, J.M. Martinez, Fitting the Sovova-s supercritical fluid extraction model by means of a global optimization tool, Computers and Chemical Engineering 32 (2008) 1735-1745.
[25] Maryam Mohagheghi, Gholamreza Bakeri, Maryam Saeedizad, Study of the Effects of External and Internal Diffusion on the Propane Dehydrogenation Reaction over Pt-Sn/Al2O3 Catalyst, Chemical Engineering & Technology 30 (2007) 1721-1725.
[26] R.B. Bird, W.E. Stewart, E.N. Lightfoot, Transport Phenomena, second edition, John Wily, New York, 2002.
[27] N. George, B.V. Kamath, A.G. Basrur, K.R. Krishnamurthy, Lithium Promoted Pt-Sn/Al2O3 catalysts for dehydrogenation of n-decane: Influence of Lithium metal precursors, Reaction Kinetics and Catalysis Letters 59 (1996) 315-323.
[28] Jose O. Valderrama, The State of the Cubic Equations of State, Industrial & Engineering Chemistry Research 42 (2003) 1603-1618.
[29] G. Zahedi, H. Yaqubi, M. Ba-Shammakh, Dynamic modeling and simulation of heavy paraffin dehydrogenation reactor for selective olefin production in linear alkyl benzene production plant, Applied Catalysis A: General 358 (2009) 1-6.
[30] Curtis F. Gerald, Patrick O. Wheatley, Applied Numerical Analysis, 6th Edition, Addison Wesley, 1999.