Optimized kinetic study of the isomerization reaction over composite catalysts by applying response surface methodology

The Pt/HZSM-5-(KCC-1, KIT-6, and SBA-3) catalysts were successfully used for the isomerization reaction of n-heptane. These catalysts were used to optimize this process at response surface methodology combined with central composite design. The effects of temperature, contact time, and flow rates of n-heptane and hydrogen, as some important variables, on the response (reaction rate) were studied. The analysis of variance gave a significant quartic model with good accuracy for estimating the reaction rates for these catalysts. The optimum conditions were obtained for the Pt/HZSM-5-SBA-3 catalyst at a temperature of 350 °C, contact time of 6 h, an H₂ flow rate of 20 cc min⁻¹ and an n-C₇ flow rate of 2 cc h⁻¹ with a reaction rate of 5.7 mol g⁻¹s⁻¹. The modeling results also showed that both the power law and Langmuir–Hinshelwood models agreed with the data obtained from catalytic performance (R² > 0.9). The results show that the Pt/HZSM-5-SBA-3 catalyst has the lowest activation energy (13.64 kJ mol⁻¹) and the highest reaction rate. The reaction order for hydrogen is in the range of − 0.03 to − 0.25 and that for n-C₇ is 0.88–1.19.