One-Pot Transformation of Citronellal to Menthol Over H-Beta Zeolite Supported Ni Catalyst: Effect of Catalyst Support Acidity and Ni Loading

Citronellal was converted to menthol in a one-pot approach using H-Beta zeolite-based Ni catalyst in a batch reactor at 80 °C, under 20 bar of total pressure. The effects of H-Beta acidity (H-Beta-25 with the molar ratio SiO2/Al2O3 = 25 and H-Beta-300 with SiO2/Al2O3 = 300) and Ni loading (5, 10 and 15 wt %) on the catalytic performance were investigated. Ni was impregnated on H-Beta support using the evaporation-impregnation method. The physico-chemical properties of the catalysts were characterized by XRD, SEM, TEM, ICP-OES, N2 physisorption, TPR, and pyridine adsorption–desorption FTIR techniques. Activity and selectivity of catalysts were strongly affected by the Brønsted and Lewis acid sites concentration and strength, Ni loading, its particle size and dispersion. A synergetic effect of appropriate acidity and suitable Ni loading in 15 wt.% Ni/H-Beta-25 catalyst led to the best performance giving 36% yield of menthols and 77% stereoselectivity to (±)-menthol isomer at 93% citronellal conversion. Moreover, the catalyst was successfully regenerated and reused giving similar activity, selectivity and stereoselectivity to the desired (±)-menthol isomer as the fresh one. Graphical Abstract: [Figure not available: see fulltext.

Thickness dependent properties of SFMO thin films grown on STO and LSAT substrates

Pure, fully textured and c-axis oriented Sr2FeMoO6, films were deposited on SrTiO3 and (LaAlO3)(0.3)(Sr2AlTaO6)(0.7) substrates with different thicknesses. A decrease in substrate induced strain was observed in films on SrTiO3 with increasing thickness, but the strain in the films on (LaAlO3)(0.3)(Sr2AlTaO6)(0.7) was nearly constant within the whole film thickness range. Despite the differences in the strain, the magnetic properties of the films showed similar thickness dependence on both substrates. The saturation magnetization and Curie temperature increased until around 150 nm thickness was reached. Semiconducting low temperature upturn in resistivity was observed in all the films and it was enhanced in the thinnest films. Thus, the band gap energy increases with increasing film thickness. According to these results, at least 150 nm thickness is required for high quality Sr2FeMoO6 films.</p

Thickness Dependent Properties of Sr2FeMoO6 Thin Films Grown on SrTiO3 and (LaAlO3)0.3(Sr2AlTaO6)0.7 Substrates

Pure, fully textured and c-axis oriented Sr2FeMoO6 films were deposited on SrTiO3 and (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates with different thicknesses. A decrease in substrate induced strain was observed in films on SrTiO3 with increasing thickness, but the strain in the films on (LaAlO3)0.3(Sr2AlTaO6)0.7 was nearly constant within the whole film thickness range. Despite the differences in the strain, the magnetic properties of the films showed similar thickness dependence on both substrates. The saturation magnetization and Curie temperature increased until around 150 nm thickness was reached. Semiconducting low temperature upturn in resistivity was observed in all the films and it was enhanced in the thinnest films. Thus, the band gap energy increases with increasing film thickness. According to these results, at least 150 nm thickness is required for high quality Sr2FeMoO6 films.Peer reviewe

28th International Conference on Low Temperature Physics (LT28) 9–16 August 2017, Gothenburg, Sweden

Pulsed laser deposited Sr2FeMoO6 thin films were investigated for the first time with scanning tunneling microscopy and spectroscopy. The results confirm atomic scale layer growth, with step-terrace structure corresponding to a single lattice cell scale. The spectroscopy research reveals a distribution of local electrical properties linked to structural deformation in the initial thin film layers at the film substrate interface. Significant hole structure giving rise to electrically distinctive regions in thinner film also seems to set a thickness limit for the thinnest films to be used in applications.</p