Gas‐phase catalytic isomerization of n‐heptane using Pt/(CrOx/ZrO2)‐HMS catalysts: A kinetic modeling

Abstract

AbstractA systematic study has been conducted to optimize the process conditions and to evaluate the kinetic parameters for the isomerization reaction of n‐heptane on the novel platinum‐chromium/zirconium‐ hexagonal mesoporous silica (Pt/(CrOx/ZrO2)‐HMS) catalysts (PCZH). The kinetic experiments were performed in a fixed‐bed reactor at the reaction temperatures of 200–350°C, Cr/Zr molar ratio of 5–35, the n‐C7 flow rate of 2–4.5 cc h−1, and H2 flow rate of 20–45 cc min−1. The statistical analysis of all experimental data was carried out using analysis of variance to optimize the operating conditions for n‐heptane reactions. The results show that the incorporation of Cr into the Pt‐Zr‐HMS structure promotes the kinetic rate of the isomerization reaction. Sharp elevation from 0.08 to 0.3 mol g−1 s−1 in the isomerization kinetic rates can be observed in the PCZH(35) and a temperature of 350 °C, when the H2 flow rate increases from 20 to 45 cc min−1 at a constant flow rate of n‐C7 (4.5 cc h−1). The surface and contour plot verifies that the kinetic rate does not significantly vary with respect to studied temperatures and Cr/Zr ratio when the flow rate of isomerization feeds is considerably low. The experimental kinetic rate obtained on the optimum condition is in good agreement with the prediction of the response surface method. The kinetic model of Langmuir–Hinshelwood as well as a power‐law model was developed for this reaction. A reasonably good fit of the obtained data shows that the Langmuir–Hinshelwood model has a better performance to define the isomerization of the n‐heptane process.