Epoxidation of palm oil-derived fatty acid methyl esters over TiO2-based catalysts in the absence of acid assistance for green rubber process oil application

The increasing demand for sustainability in the tire and rubber industries has driven the development of eco-friendly rubber process oils to replace petroleum-derived aromatic extracts restricted for their high polycyclic aromatic hydrocarbon content. In this study, palm oil–derived fatty acid methyl ester (FAME) was epoxidized to produce epoxidized FAME (EFAME) as a green rubber process oil. Titanium-based catalysts with varying silica/titanium (Si/Ti) molar ratios were synthesized via hydrothermal method and compared with commercial titanium dioxide (TiO 2 -C). Comprehensive characterization revealed that hydrothermal TiO 2 (TiO 2 -H, Si/Ti = 0) possessed a mesoporous, channel-like morphology with moderate surface area and exposed multiple Ti species, enhancing accessibility for bulky FAME molecules. In FAME epoxidation with hydrogen peroxide (H 2 O 2 ) and tert -butanol, TiO 2 -H exhibited the best performance, achieving 71% FAME conversion, 1.9 wt% oxirane oxygen content, and 68% relative conversion to oxirane under the optimized conditions (70 °C, 24 h, 4 wt% catalyst). In contrast, titanium silicalite-1 (TS-1) catalyst suffered from diffusion limitations, while TiO 2 -C was limited by its low surface area. Studies on reaction parameters highlighted the importance of balancing conversion and selectivity to suppress epoxide ring-opening. Application tests showed that EFAME provided cure behavior and mechanical properties in nitrile rubber (NBR) and styrene-butadiene rubber (SBR)/butadiene rubber (BR) blends comparable to petroleum-based plasticizers, offering a sustainable alternative. This work provides both catalytic and application insights for bio-based rubber process oils, contributing to the development of greener tire and rubber technologies. • Epoxidation of palm oil-derived FAME achieved over TiO 2 without acid addition. • Hydrothermal TiO 2 -H showed higher activity for bulky substrates than TS-1. • Channel-like mesoporosity of TiO 2 -H improved diffusion and Ti site accessibility. • Epoxidized FAME served as a green process oil for both low- and high-polar rubbers. • NBR plasticized by epoxidized FAME had higher rebound and abrasion resistance.