Interfacial Synergy in <scp>ZSM</scp> ‐5/ <scp> TiO ₂ </scp> Heterogeneous Catalysts for Enhanced Stability in Rubber Seed Oil Epoxidation

ABSTRACT Catalytic epoxidation of vegetable oil commonly possesses a reduction of relative conversion to oxirane (RCO%) over reaction time due to the ring‐opening of epoxide groups that can be overcome by controlling pore structure and reactant diffusion control. This research was conducted to tailor heterogeneous catalyst composite surface area by combining ZSM‐5 with titanium dioxide (TiO 2 ) via impregnation method to improve the reaction stability of the catalyst in the epoxidation of rubber seed oil (RSO). Five different ratios of ZSM‐5 to TiO 2 were studied to observe the catalyst's efficacy in the epoxidation process by measuring the relative conversion to oxirane (RCO%), surface area (BET), and structural characteristics (XRD). The 1:3 ZSM‐5/TiO 2 ratio showed the most constant RCO% during the reaction (20 min) compared to single stage catalyst which RCO% inclined rapidly and decline afterwards, even though the epoxide yield was a little lower (below 15%). Next, the calcination conditions (temperature and time) of the catalyst were studied to improve the RCO%. Catalyst calcined at temperature of 300°C within 6 h produced the highest RCO% of 35% compared to initial RCO% of 15%, the lowest BET surface area and the biggest pore volume. XRD characterization showed that TiO 2 was successfully added to the ZSM‐5 framework without changing the way the crystals looked. The hybrid catalyst also maintained catalytic activity throughout the multi‐cycle evaluation, with all RCO values remaining comfortably above the 40% threshold. The combination of ZSM‐5's microporous structure and TiO 2 's reactive surface managed to suppress the ring‐opening of epoxide groups and maintained high RCO% at the longest period during the catalytic rubber seed oil epoxidation. This custom‐made composite is an effective alternative catalyst to improve quality of epoxide groups produced from vegetable oil epoxidation for making bio‐based materials and green polymers.