Selective partial biodiesel hydrogenation using highly active supported palladium nanoparticles in imidazolium-based ionic liquid

The low oxidative stability of biodiesel derived from polyunsaturated oils is one of the great challenges to be overcome in biodiesel technology. Here, we use a high activity catalyst Pd/ImS3-12@Al2O3, prepared by adsorption of water-prepared palladium nanoparticles on aluminum oxide, for partial biodiesel hydrogenation. The catalyst shows higher hydrogenation activity than conventional Pd/C, leading in the absence of ionic liquid (IL) to fully hydrogenated product. In the presence of BMIM·NTf2 (1-butyl-3-methylimdazolium bis(trifluoromethylsulfonyl)imide) IL the activity of the Pd/ImS3-12@Al2O3 catalyst could be controlled and selective reduction to monoene product, with large preference for formation of the cis isomer, could be achieved at low temperature and pressure, with very low catalyst loading, no detectable metal leaching and good recyclability. The partially hydrogenated biodiesel is far more stable to oxidation than the crude, without compromising its cold-flow properties.

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► Heterogeneous catalyst with surfactant stabilized palladium nanoparticles on Al2O3.
► This catalyst is used for partial biodiesel hydrogenation.
► Ionic liquid as a reaction media allows selective hydrogenation of polyenes.
► Partially hydrogenated biodiesel if more stable against oxidation.
► The ionic liquid allows simple separation of products and catalyst recovery.