Kinetic study of propane aromatization over Zn/HZSM-5 zeolite under conditions of catalyst deactivation using genetic algorithm

Abstract

The kinetic studies of propane aromatization reaction over Zn/ /HZSM-5 catalyst at temperature of 500-560 °C and space velocity of 500-2500 cm 3 g cat-1 h-1 , in a plug flow reactor, under catalyst deactivating conditions were performed. A lumped kinetic model consisting of six lumped components and six reaction steps was proposed to describe the aromatization of propane. The kinetic model involves 18 kinetic parameters and one catalyst deactivation constant. The reaction steps orders were obtained by the power law model. Frequency factors and the apparent activation energies of the reaction steps were calculated based on the Arrhenius equation. An exponential function depending on the time-on-stream was applied for the catalyst deactivation model and the kinetic parameters were calculated via a genetic algorithm. The kinetic results indicated that the lumped kinetic model can well estimate the product yields of propane aromatization.

Propane Dehydrogenation and Cracking over Zn/H-MFI Prepared by Solid-State Ion Exchange of ZnCl2

“…Apparent activation energies ( E a,app ) for C 3 H 8 dehydrogenation and cracking were measured as a function of Zn loading and are given in Table , along with the corresponding data for H-MFI. The apparent activation energies for dehydrogenation and cracking are similar to each other for all Zn loadings and consistent with the apparent activation energies reported previously (29.8 and 31.2 kcal/mol for C 3 H 8 dehydrogenation and cracking, respectively) . The apparent activation energies for C 3 H 8 dehydrogenation and cracking generally appear to increase slightly as the Zn/Al ratio of spent catalysts increases from 0.06 to 0.24.…”

“…The apparent activation energies for dehydrogenation and cracking are similar to each other for all Zn loadings and consistent with the apparent activation energies reported previously (29.8 and 31.2 kcal/mol for C 3 H 8 dehydrogenation and cracking, respectively). 84 The apparent activation energies for C 3 H 8 dehydrogenation and cracking generally appear to increase slightly as the Zn/Al ratio of spent catalysts increases from 0.06 to 0.24. The apparent entropies of activation for C 3 H 8 dehydrogenation and cracking also generally appear to increase slightly with increasing catalyst Zn loading, as shown in Figure S14 75 Finally, the decrease in the rate of C 3 H 8 dehydrogenation is not due to an approach to equilibrium; the C 3 H 8 conversion of <2% is significantly lower than the equilibrium conversions of 76 and 65% for this reaction in the absence and presence of cofed H 2 , respectively.…”

The effect of water and zinc loading on LPG catalytic cracking for light olefin production using Response Surface Methodology

“…However, by decreasing the number of stronger acid sites upon zinc impregnation, the coke formation would be limited and consequently the activity of the catalyst will be preserved [10]. It is detected that introducing more than the optimum amount of zinc as an intermediate metal to the catalyst results in decreasing the Bronsted strong acid sites, though maintaining a sufficiently high number to diminish the protolytic cracking reactions [24,34]. Graphical optimization has produced an overlay plot to display the area of feasible response values in the factor space.…”