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Effect of Pd particle size on activity and cis-trans selectivity in partial hydrogenation of soybean oil-derived FAMEs over Pd/SiO2 catalysts
Author(s)
Prabnasak, Panisa
Prayoonpunratn, Patsakol
Triphatthanaphong, Pholawat
Thunyaratchatanon, Chachchaya
Mochizuki, Takehisa
Chen, Shih Yuan
Luengnaruemitchai, Apanee
Date Issued
June 15, 2020
Type
Article
Abstract
Partial hydrogenation of soybean oil-derived fatty acid methyl esters (FAMEs) was performed to improve oxidative stability of biodiesel. The reaction was tested in a semi-batch reactor at 100 °C, 0.4 MPa. The effect of Pd particle size on activity and cis-trans selectivity was investigated over SiO2- and MCM-41-supported Pd catalysts, with different Pd loadings (0.5 and 1 wt.%). For Pd/SiO2 catalysts with relatively large Pd particle sizes (6.1–7.8 nm), the adsorption of polyunsaturated C18:2 and C18:3 FAMEs was promoted on the flat metal surface, providing 2- to 3-fold higher turnover frequency (TOF) compared with Pd/MCM-41 catalysts. In contrast, the Pd/MCM-41 catalysts with relatively small Pd particle sizes (2.7–4.0 nm), showed higher selectivity towards the desired monounsaturated C18:1 FAMEs due to lower affinity of isolated double bond (presented in C18:1) on the Pd surface. In addition, selectivity towards the desired cis-C18:1 FAMEs was found to be highly sensitive to Pd particle size. The 0.5Pd/MCM-41 catalyst with small Pd particle size (2.7 nm), provided high cis-C18:1 selectivity, resulting in a biodiesel with better cold flow property compared with the trans-isomers. With partial hydrogenation over the prepared Pd catalysts, biodiesel with significantly improved oxidative stability (>10 h) could be obtained.
Citation
Fuel Processing Technology, 203, 2020