Bimetallic Pd-Pt catalyst was successfully prepared via conventional heating (CH), microwave (MW), and ultrasonic irradiation (US) methods. Bimetallic Pd-Pt nanoparticles stabilized with polyvinylpyrrolidone (PVP) were prepared with molar ratio of PVP to metal, 40:1. Smaller particles sizes with narrow distribution obtained after 30min and 10min with US and MW methods respectively. All the particles are spherical or near spherical in shape.
The average particles size and size distribution for Pd-Pt (US) nanoparticles was 1.28 ± 0.29 nm, while for Pd-Pt (MW) nanoparticles was 1.05 ± 0.21 nm. The average particles sizes of these bimetallic nanoparticles are comparable with the classical CH method, which was 1.23 ± 0.25 nm. Based from the XPS analysis, surface compositions of Pd and Pt show that PdPt(CH) and PdPt(MW) catalyst were enriched with Pd, meanwhile PdPt (US) composition was comparable and it might be in alloy structure formation. The activity of these three catalysts for the hydrogenation reaction of palm olein was studied. The reaction conducted under ambient temperature and atmospheric pressure. A molar ratio of palm olein to catalyst of 25000:1 has been used in the hydrogenation reaction to determine the conversion of linoleate, selectivity of trans-isomer and iodine value (IV) in the hydrogenated palm olein. After 180 min of reaction, full conversion achieved with Pd-Pt (MW) catalyst, while only 91.4% and 80.6% conversion achieved with Pd-Pt (US) and Pd-Pt (CH) respectively. However, the Pd-Pt (MW) catalyst shows the highest elaidate selectivity after 180 min, which was up to 13.1%, meanwhile the elaidate selectivity of 11.82% and 8.1% for both Pd-Pt (US) and Pd-Pt (CH) respectively. Even though higher conversion of linoleate achieved in short time and lower trans selectivity produced with Pd-Pt bimetallic catalyst. The IV calculated shows that Pd-Pt (MW) catalyst has the lowest IV then followed by Pd-Pt (US) and Pd-Pt (CH) catalysts.