Development of highly selective Pt-Sn catalysts on mesoporous titania for hydrogenation of citral to unsaturated alcohols

Novel bimetallic catalysts on mesoporous titania containing Pt-Sn nanoparticles derived from a carbonyl complex for selective hydrogenation of citral were developed. The influence of nature of Pt Sn precursor, its concentration, solvent used, Pt Sn solution/TiO2 ratio, adsorption duration, type of catalyst activation treatment on the content, structural and electronic properties of supported metals were studied. Under optimal synthesis conditions high dispersion of Pt3 Sn particles (mean size 1.5 nm) and narrow size distribution (1-3 nm) were achieved. The correlation between synthesis conditions and physicochemical properties of Pt-Sn catalysts has been established. In citral hydrogenation, the bimetallic catalysts showed a TOF of 0.2-3.3 mm-’ and a high selectivity to unsaturated aldehydes (80-90%) even at high conversions

Application of POSS nanotechnology for preparation of efficient Ni catalysts for hydrogen production

\u3cp\u3ePOSS (polyhedral oligomeric silsesquioxanes) nanotechnology was applied for preparation of efficient Ni catalysts for hydrogen production through autothermal reforming of methane (ATR of CH\u3csub\u3e4\u3c/sub\u3e). The novel metal-POSS precursor [Nickel (II) ‒ HeptaisobutylPOSS (C\u3csub\u3e4\u3c/sub\u3eH\u3csub\u3e9\u3c/sub\u3e)\u3csub\u3e7\u3c/sub\u3eSi\u3csub\u3e7\u3c/sub\u3eO\u3csub\u3e9\u3c/sub\u3e(OH)O\u3csub\u3e2\u3c/sub\u3eNi] of Ni nanoparticles was introduced into Ce\u3csub\u3e0.5\u3c/sub\u3eZr\u3csub\u3e0.5\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e support with following calcination and reduction stages of activation. The peculiarity of the genesis of Ni/SiO\u3csub\u3e2\u3c/sub\u3e/Ce\u3csub\u3e0.5\u3c/sub\u3eZr\u3csub\u3e0.5\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e nanomaterials and their characteristics versus deposition mode were studied by X-ray fluorescence spectroscopy, thermal analysis, N\u3csub\u3e2\u3c/sub\u3e adsorption, X-ray diffraction, high-resolution transmission electron microscopy and H2 temperature-programmed reduction. The two kinds of supported Ni-containing particles were observed: highly dispersed Ni forms (1‒2 nm) and large Ni-containing particles (up to 50‒100 nm in size). It was demonstrated that the textural, structural, red-ox and, consequently, catalytic properties of ex-Ni-POSS catalysts depend on the deposition mode. The increase of a portion of difficultly reduced Ni\u3csup\u3e2+\u3c/sup\u3e species is found upon application of intermediate calcination during Ni-POSS deposition that has detrimental effect on the activity of catalyst in ATR of CH4. The Ni/SiO\u3csub\u3e2\u3c/sub\u3e/Ce\u3csub\u3e0.5\u3c/sub\u3eZr\u3csub\u3e0.5\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e catalyst prepared by one-step Ni-POSS deposition exhibits the highest H\u3csub\u3e2\u3c/sub\u3e yield ‒ 80% at T = 800 °C.\u3c/p\u3

Design of highly efficient catalyst for rational way of direct conversion of methane

\u3cp\u3eEffects of composition and preparation method of MnNaW/SiO\u3csub\u3e2\u3c/sub\u3e and LaSr/CaO catalysts on their physical-chemical properties and performance in oxidative coupling of methane (OCM) have been studied. For MnNaW/SiO\u3csub\u3e2\u3c/sub\u3e catalysts the synthesis method and type of SiO\u3csub\u3e2\u3c/sub\u3e have a significant effect on the texture, while the Na/W ratio determines the phase composition. The variation of preparation method and temperature of catalyst calcination allows regulation of the metal surface concentration and mode of metal distribution across the SiO\u3csub\u3e2\u3c/sub\u3e support. For LaSr/CaO catalysts the synthesis method determines the specific surface area, surface and phase composition. Correlations between catalyst performance, preparation method and state of the catalyst were established. The rational preparation procedure and perspective composition of OCM catalyst have been developed. The 20La/CaO catalysts prepared by citrate sol-gel method were shown to provide ~20% C\u3csub\u3e2\u3c/sub\u3e yield and ~40% methane conversion at 800 ºC.\u3c/p\u3

Effect of preparation mode on the properties of Mn-Na-W/ Sio\u3csub\u3e2\u3c/sub\u3e catalysts for oxidative coupling of methane:conventional methods vs. POSS nanotechnology

\u3cp\u3eUsing XPS, BET, XRD, TG-DTA, HRTEM-EDX, TPR and UV-Vis Diffuse Reflectance spectroscopic methods the electronic, redox and structural properties of Mn-Na-W/ SiO\u3csub\u3e2\u3c/sub\u3e catalysts prepared by the incipient wetness impregnation method and mixture slurry method were studied in detail. Since POSS nanotechnology (POSS = polyhedral oligomeric silsesquioxanes) has attracted attention as tooling for synthesis of catalysts with novel properties and functionalities, we expanded this method for the preparation of Mn-Na-W/ SiO\u3csub\u3e2\u3c/sub\u3e catalyst. The physicochemical and catalytic properties of Mn-Na-W/ SiO\u3csub\u3e2\u3c/sub\u3e catalysts prepared by conventional methods and POSS nanotechnology were examined comparatively. In all studied Mn-Na-W/ SiO\u3csub\u3e2\u3c/sub\u3e catalysts both individual oxides (MnO\u3csub\u3ex\u3c/sub\u3e, WO\u3csub\u3e3\u3c/sub\u3e) and bimetal oxide phases (Na\u3csub\u3e2\u3c/sub\u3eWO\u3csub\u3e4\u3c/sub\u3e, MnWO\u3csub\u3e4\u3c/sub\u3e) are found in addition to oxide particles of high dispersion. The UV-Vis Diffuse Reflectance indicates that Na\u3csup\u3e+\u3c/sup\u3e cations facilitates stabilization of octahedrally coordinated Mn\u3csup\u3e3+\u3c/sup\u3e \u3csub\u3eOh\u3c/sub\u3e cations in the isolated state, while Mn\u3csup\u3e3+\u3c/sup\u3e \u3csub\u3eOh\u3c/sub\u3e promote the disordering of W\u3csup\u3e6+\u3c/sup\u3e cations in the supported system. The Mn-Na-W/ SiO\u3csub\u3e2\u3c/sub\u3e prepared using metal-POSS precursors marks out presence of unglobular SiO\u3csub\u3e2\u3c/sub\u3e particles, higher dispersion of MnO\u3csub\u3ex\u3c/sub\u3e and MnWO\u3csub\u3e4\u3c/sub\u3e particles and more easily reducible metal-oxide species. The catalysts prepared by incipient impregnation method and mixture slurry method have practically similar catalytic performance while the catalyst prepared by POSS nanotechnology method shows lower activity and selectivity. At 800−850 °C the increase of C2 hydrocarbons yield from 4 to 15% and the rise of molar ratio C\u3csub\u3e2\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e/C\u3csub\u3e2\u3c/sub\u3eH\u3csub\u3e6\u3c/sub\u3e from 0.2 to 1 are observed when impregnation or mixture slurry method are used for catalyst preparation instead of POSS nanotechnology method.\u3c/p\u3