Enhancement of Stability and Activity of Pt-Loaded HSiW/UiO-66 Acid Catalyst and Kinetic Modeling for n-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 n-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 n-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 n-butane conversion and isobutane selectivity, was investigated. The kinetic behavior of the 0.5%Pt/70%HSiW/UiO-66 catalyst in the n-butane hydroisomerization reaction was explained by using the Langmuir–Hinshelwood mechanism. This model was employed to investigate how hydrogen and n-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 R2 indicated that this model provided a reasonable fit to the experimental data, thereby enabling accurate determination of the kinetic parameters.