Enhancement of Stability and Activity of Pt-LoadedHSiW/UiO-66 Acid Catalyst and Kinetic Modeling for <i>n</i>‑Butane Hydroisomerization

In this work, the microporous support UiO-66 was synthesized using the hydrothermal method, and its structure was improved by the impregnation of silicotungstic acid (HSiW) and platinum, resulting in a bifunctional catalyst. The catalyst features acidic and metallic active sites established by the presence of HSiW and Pt in its structure. Various analyses including XRD, FT-IR, FE-SEM, EDS, XRF, BET, NH₃-TPD, and TGA were conducted to assess the chemical properties, surface structure, acidity, and thermal stability. The impact of different concentrations of HSiW on this support was evaluated during the <i>n</i>-butane hydroisomerization process, in which the sample containing 70%HSiW/UiO-66 gave the most favorable results. The addition of Pt (0.5 wt %) as a promoter increased the activity and stability of the catalyst in this process. The 0.5%Pt/70%HSiW/UiO-66 sample demonstrated superior stability against deactivation compared with other modified samples. After 7 h of reaction, it achieved an <i>n</i>-butane conversion of 56.8% and an isobutane selectivity of 74%. Furthermore, the influence of various operating conditions, including the reaction temperature and weight hourly space velocity (WHSV), on catalyst activity, specifically in terms of <i>n</i>-butane conversion and isobutane selectivity, was investigated. The kinetic behavior of the 0.5%Pt/70%HSiW/UiO-66 catalyst in the <i>n</i>-butane hydroisomerization reaction was explained by using the Langmuir–Hinshelwood mechanism. This model was employed to investigate how hydrogen and <i>n</i>-butane pressure influence the reaction rate. The apparent activation energy determined from the Langmuir–Hinshelwood model was found to be 38.51 kJ mol^–1. The value of <i>R</i>² indicated that this model provided a reasonable fit to the experimental data, thereby enabling accurate determination of the kinetic parameters.