مطالعه سينتيك واكنش‌هاي هيدروژن‌گيري از پارافين‌هاي راست زنجير C10 تا C13، سينتيك غيرفعال شدن كاتاليست و مدل‌سازي رياضي راكتور بستر ثابت جريان شعاعي مربوطه

Study of kinetics of C10-C13 normal paraffin dehydrogenation, deactivation kinetics of catalyst an‎d mathematical modeling of the relevant radial flow fixed-bed reactor

مهندسي شيمي

This research aimed to investigate the intrinsic kinetics of the dehydrogenation reactions of C10–C13 linear paraffins for the production of mono-olefins over the industrial NDC-10 catalyst, to develop a catalyst deactivation kinetic model, an‎d to simulate the industrial reactor of the Pacol unit. Laboratory-scale experiments were conducted using a small-scale packed-bed reactor containing approximately 10 g of catalyst. In addition, the effects of operating conditions, including temperature, pressure, weight hourly space velocity (WHSV), hydrogen-to-hydrocarbon ratio, an‎d feed quality, on catalyst performance were investigated. For the reaction kinetic study, the temperature, pressure, WHSV, hydrogen-to-hydrocarbon ratio, an‎d feed quality were varied within the ranges of 465–485 K, 1.1–1.2 barg, 25–45 h⁻¹, 3–7, an‎d 0.81–0.91, respectively. Since catalyst deactivation proceeds relatively slowly under normal operating conditions, an accelerated deactivation approach was employed by decreasing the hydrogen-to-hydrocarbon ratio an‎d increasing the inlet hydrocarbon flow rate in order to reduce the time an‎d cost associated with the deactivation experiments. Accordingly, for the catalyst deactivation study, the temperature, pressure, WHSV, an‎d hydrogen-to-hydrocarbon ratio were varied within the ranges of 465–485 K, 1.1–1.4 barg, 25–35 h⁻¹, an‎d 1–2, respectively. A reaction network comprising 12 reactions an‎d 17 chemical species was developed to investigate the reaction kinetics. The results indicated that catalyst deactivation occurs through a chemical mechanism associated with coke formation via parallel reactions. Aromatic compounds an‎d diolefins were identified as the major coke precursors, whereas mono-olefins exhibited a comparatively lower contribution to coke formation. Statistical analysis demonstrated that the kinetic parameters provided an appropriate fit to the experimental data. Comparison plots further showed that the developed model was capable of predicting the outlet concentrations of paraffins, mono-olefins, diolefins, an‎d aromatics in the laboratory-scale reactor with errors of approximately 5%, 10%, 15%, an‎d 25%, respectively. The effect of steam injection on catalyst performance an‎d deactivation was also investigated. The results demonstrated that stepwise steam injection, with the steam concentration gradually increased from 1000 to 3000 ppm, enabled the catalyst to maintain an adequate production yield for a longer period. The developed model for the industrial Pacol reactor predicted the total paraffin conversion, mono-olefin selec‎tivity, an‎d overall mono-olefin production yield with accuracies of 30%, 15%, an‎d 20%, respectively. Furthermore, the model was employed to determine the distributions of velocity, pressure, temperature, an‎d species concentrations throughout different regions of the reactor, an‎d to investigate the effects of operating conditions on mono-olefin production performance.

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