Effect of polyvinylpyrrolidone on the catalytic properties of Pd/gamma-Fe2O3 in phenylacetylene hydrogenation

Maghemite nanoparticles modified with polyvinylpyrrolidone were synthesized using the chemical co-precipitation method. Palladium ions have then been immobilized on the PVP/gamma-Fe(2)O(3)magnetic support. The Pd-PVP/gamma-Fe(2)O(3)catalyst obtained was characterized using X-ray diffraction, thermogravimetry coupled with differential scanning calorimetry and quadrupole mass spectrometry, scanning electron microscopy combined with energy dispersive X-ray analysis, transmission electron microscopy, nitrogen adsorption-desorption and vibrating sample magnetometry. Morphology, microstructure, particle sizes and textural properties of the Pd-PVP/gamma-Fe(2)O(3)were compared with those of the unmodified Pd/gamma-Fe(2)O(3)catalyst, synthesized using the same method. The polymer has affected the size of gamma-Fe(2)O(3)nanoparticles and their agglomeration, forming compact microstructure with decreased mesopores (4.5 nm). Palladium nanoparticles with size of 3-5 nm were found both on the surface of the PVP/gamma-Fe(2)O(3)particles (6-10 nm) and inside the pores formed by them. The Pd-PVP/gamma-Fe(2)O(3)has demonstrated improved catalytic properties in phenylacetylene hydrogenation under mild conditions of 40 degrees C and 0.1 MPa, compared to Pd/gamma-Fe(2)O(3)and similar catalysts prepared using polyethylene glycol and pectin. The hydrogenation rate of C-C triple bond on Pd-PVP/gamma-Fe(2)O(3)achieved 2.8 x 10(-6) mol s(-1)and selectivity to styrene was 92%. The catalyst showed weak ferromagnetic and soft magnetic properties (M-S = 51 emu g(-1), M-r = 5.4 emu g(-1), and H-C = 71 Oe) and, therefore, can be easily recovered with an external magnet and reused for at least 11 runs without significant degradation in the catalytic activity.