Marina Lindblad

Preparation of Ni/Al2O3 catalysts from vapor phase by atomic layer epitaxy

Ni/Al2O3 catalysts were prepared by saturating gas-solid reactions as an atomic layer epitaxy (ALE) process. Vaporized Ni(acac)2 was chemisorbed on a porous alumina support, and the produced surface complex was then air treated to remove the ligand residues. The nickel content could be precisely controlled by repeating this reactor cycle. On alumina preheated at 800°C, the nickel content varied from 3 to 21 wt%, when the number of reaction cycles was increased from one to ten. The performance of the Ni-catalysts was evaluated in the gas-phase hydrogenation of toluene. The preheat temperature of alumina influenced the activity of the catalyst, and a maximum in the activity was observed for catalysts prepared from alumina preheated at 875°C. Catalysts prepared by four reaction cycles, containing about 10 wt% nickel, gave the highest utilization of nickel.

The utilization of saturated gas-solid reactions in the preparation of heterogeneous catalysts

Abstract Saturated gas-solid reactions known from Atomic Layer Epitaxy (ALE) were used to processvarious catalysts. Good homogeneity of metal species was verified both along the entire catalyst bed and inside the particles. A variety of volatile metal compounds including metal chlorides, alkoxides and β-diketonates were successfully used as reactants. The ALE processing is described with reference to examples demonstrating the achievement of surface saturation, reproducibility of processes, selection of process parameters, growth of oxides to modify the support and the binding of two metal compounds.

Preparation of noble metal catalysts by atomic layer deposition: FTIR studies

Alumina-supported iridium and platinum samples were prepared from organometallic precursors using the ALD (atomic layer deposition) technique. Removal of precursor-originated ligands by oxidative and reductive treatments were monitored in situ by FTIR/MS. Surface species at different stages of the treatments as well as the gaseous products were identified. The results are used to find an optimal precursor-removal procedure and to investigate a possible solution to control (small) metal concentrations when preparing noble metal catalysts by ALD.

Deposition of platinum into beta-zeolite

Abstract Platinum was deposited into beta zeolites with different techniques. Platinum was well-dispersed when the catalyst was prepared by ion exchange and Atomic Layer Epitaxy (ALE) deposition methods. In impregnation, the source material of platinum and post-treatments affected for the dispersion. Platinum dispersion was low when trimethyl(methylcyclopentadienyl)platinum impregnated beta zeolite was calcined prior to reduction. In calcination at 623 K in air most platinum was reduced. Platinum was totally reduced with hydrogen at 573 K. In pulsing of carbon monoxide at 300 K on platinum ALE catalyst, carbon dioxide formation was observed. Trimethyl(methylcyclopentadienyl)platinum impregnated beta zeolite produced selectively cinnamyl alcohol at low conversion whereas with other catalysts several different products were formed.

Hydrodeoxygenation of Isoeugenol over Alumina Supported Ir-, Pt- and Re Catalysts

Hydrodeoxygenation (HDO) of isoeugenol (IE) was investigated using bimetallic iridium–rhenium and platinum–rhenium catalysts supported on alumina in the temperature and pressure ranges of 200–250 °C and 17–40 bar in nonpolar dodecane as a solvent. The main parameters were catalyst type, hydrogen pressure, and initial concentration. Nearly quantitative yield of the desired product, propylcyclohexane (PCH), at complete conversion in 240 min was obtained with Ir–Re/Al2O3 prepared by the deposition–precipitation method using 0.1 mol/L IE initial concentration. High iridium dispersion together with a modification effect of rhenium provided in situ formation of the IrRe active component with reproducible catalytic activity for selective HDO of IE to PCH. The reaction rate was shown to increase with the increasing initial IE concentration promoting also HDO and giving a higher liquid phase mass balance. Increasing hydrogen pressure benefits the PCH yield.