Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-I-21DEACTIVATION KINETICS OF PLATINUM-BASED CATALYSTS INDEHYDROGENATION OF HIGHER ALKANESMaryam Saeedizad, Saeed Sahebdelfar, Zahra MansourpourCatalyst Research Group, Petrochemical Research and Technology Company,National Petrochemical Company, P.O. Box 14358, Tehran, IranAbstract: The deactivation of promoted Pt /Al 2 O 3 catalyst in dehydrogenation of C 10 -C 14normal alkanes to the corresponding mono-olefins was studied. A simple kinetic model forcatalyst decay was obtained. The model was based on a reversible main reaction andconcentration-independent, nth-order decay law. It was checked both through integral analysisof experimental data and nonlinear estimation functions of temperature-time data of acommercial plant and the model parameters were evaluated. The results of both approacheswere consistent. The deactivation rate law was found to be of the second-order. The activationenergies of the dehydrogenation and catalyst decay were found to be E A =60 kJ/mol andE d =230 kJ/mol, respectively.Keywords: Dehydrogenation of alkanes; Pt/Al 2 O 3 catalyst; Kinetics; Catalyst deactivation.Introduction: In commercial practice, the activity of dehydrogenation catalyst dropsslowly with time on stream. To achieve a constant conversion, the reaction rate is maintainedby a programmed increase of the feed temperature.The previous deactivation modeling by temperature-time trajectories were based on asingle irreversible primary reaction and nth-order, concentration–independent deactivation [1,2, 3]; however, in this work the main reaction was considered to be reversible and itsconsequence on the interpretation of the results was considered. The kinetic parameters wereestimated using commercial temperature-time data and the results were compared with thoseof integral method of analysis of experimental data.Experimental: The reactor tests were performed in a fixed-bed, isothermal reactor at743 K and 0.7 barg using industrial feedstock with a H 2 /hydrocarbon molar ratio of six.HP/PONA column of 50 m length, 0.2 mm diameter and 0.5 µm fill thickness and FIDdetector were used for liquid product analysis. The industrial data were provided by acommercial plant for three sets of runs, with start of run and end of run temperatures of 743and 768 K, respectively.Modeling: To achieve a constant conversion, Eq. (1) should be satisfied:kA( T ) a(t,T )XAe( T ) ln( 1−XA( T ) / XAe( T ))= kA0X ( T ) ln( 1−X ( t = 0, T ) / X ( T ))Eq. (1)Ae0A0Ae065