Luděk Kaluža

High activity of highly loaded MoS2 hydrodesulfurization catalysts supported on organised mesoporous alumina

Abstract Organised mesoporous alumina-supported Mo sulfide catalysts were prepared by the conventional impregnation with solution of ammonium heptamolybdate and by the method of thermal spreading of MoO3. The mesoporous alumina (surface area 400–600 m 2 g −1 , pore diameter 3–4.5 nm) exhibited much higher capacity for dispersion of Mo species than the conventional alumina. The activity in thiophene hydrodesulfurization of highly loaded mesoporous alumina-supported catalysts with the MoO3 content of 30 wt.% was almost two times higher than the activity of the conventional industrial Mo/Al2O3 containing 15 wt.% of MoO3

Carbon-supported Mo catalysts prepared by a new impregnation method using a MoO3/water slurry: saturated loading, hydrodesulfurization activity and promotion by Co

Abstract MoO 3 /activated carbon catalysts were prepared by a new impregnation method: Mo species were adsorbed from a MoO 3 /water slurry. The maximum achieved loading was 27–34 wt.% MoO 3 for various carbons and the deposited phase was X-ray amorphous. The surface area and volume of micropores of the carbon supports dropped by about 40% after saturation of the supports with molybdenum trioxide. For the support Norit RX, the point of zero charge decreased from an initial 8.2 to about 2.6 as the MoO 3 loading increased up to about 15% and then levelled off. The catalytic activity for the hydrodesulfurization of thiophene increased linearly with loading up to about 15% and then almost levelled off. A strong synergistic effect in activity was achieved by addition of Co to the 15% MoO 3 /C catalyst; however, the synergism observed when adding Co to a saturated 33% MoO 3 /C catalyst was small. It was concluded that molybdenum trioxide is chemisorbed in a highly dispersed ‘monolayer’ form up to a loading of about 15% MoO 3 . Further adsorption between about 15% and the saturation loading occurs by ‘physisorption’ in micropores and leads to a ‘multilayer’ form. The ‘multilayer’ form does not contribute to the surface properties (e.g. catalytic activity) and is not accessible to promotion by cobalt. Carbon-supported catalysts were much more active than their alumina-supported counterparts.

NiMo/γ-Al2O3 Catalysts from Ni Heteropolyoxomolybdate and Effect of Alumina Modification by B, Co, or Ni

A hydrotreating NiMo/γ-Al2O3 catalyst (12 wt% Mo and 1.1 wt% Ni) was prepared by impregnation of the support with the Anderson-type heteropolyoxomolybdate (NH4)4Ni(OH)6Mo6O18. Before impregnation of the support, it was modified with an aqueous solution of H3BO3, Co(NO3)2, or Ni(NO3)2. The catalysts were investigated using N2 adsorption, O2 chemisorption, X-ray diffraction, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, temperature-programmed reduction, temperature-programmed desorption, and X-ray photoelectron spectroscopy. The addition of Co, Ni, or B influenced the Al2O3 phase composition and gave increased catalytic activity for 1-benzothiophene hydrodesulfurization (HDS). X-ray photoelectron spectroscopy confirmed that the prior loading of Ni, Co or B increased the degree of sulfidation of the NiMo/γ-Al2O3 catalysts. The highest HDS activity was observed with the NiMo/γ-Al2O3 catalyst with prior loaded Ni.

Preparation of MoO3/Al2O3 Catalysts with Sharp Eggshell Mo Distribution by Slurry Impregnation

MoO3/Al2O3 catalysts with eggshell Mo concentration profiles were prepared by reaction of Al2O3 extrudates or balls with slurry of MoO3 in water. The Mo concentration wave penetrating Al2O3 particles during this slurry impregnation was almost rectangular. Its height was close to the filled monolayer loading. The thickness of the shell was regulated either by impregnation time or by the MoO3 amount in the slurry. The hydrodesulfurization activity of Mo species deposited by slurry impregnation was about the same or better (depending on the Al2O3 used) as in industrial MoO3/Al2O3 catalyst.

The rearrangement of 1-methylcyclohex-1-ene during the hydrodesulfurization of FCC gasoline over supported Co(Ni)Mo/Al2O3 sulfide catalysts: the isolation and identification of branched cyclic C7 olefins

In the study of the simultaneous hydrodesulfurization of 1-benzothiophene and the olefin hydrogenation of 1-methylcyclohex-1-ene (1-MCH), we encountered a rearrangement of 1-MCH during the first step of catalytic hydrogenation, which yielded various branched cyclic olefins; mainly ethylcyclopentene and dimethylcyclopentene isomers. The volatile isomerization products were isolated directly from the diluted reaction mixture via the combination of chromatographic techniques including preparative gas chromatography, and were undoubtedly assigned by NMR spectroscopy. The precise identification of the isomerization products was required for a detailed kinetic study.

CoMo/ZrO2 Hydrodesulfurization Catalysts Prepared by Chelating Agent Assisted Spreading

The novel Mo/ZrO2 and CoMo/ZrO2 catalysts were prepared by impregnation of the monoclinic ZrO2 by the chelating agent nitrilotriacetic acid (NTA) assisted spreading of MoO3 with CoCO3·xH2O and compared with samples prepared conventionally. The catalysts were characterized by X-ray diffraction, N2 physisorption, O2 chemisorption and activity in 1-benzothiophene hydrodesulfurization (HDS). The application of NTA during the catalysts preparation systematically increased the HDS activity by the factor 1.2–1.7.Graphical Abstract

Total oxidation of ethanol and toluene over ceria—zirconia supported platinum catalysts

The effect of platinum loading (0.09–1.00 mass %) on the performance of ceria-zirconia supported catalysts in the total oxidation of ethanol and toluene in air was investigated. The introduction of platinum promoted the reduction of surface cerium and decreased the acidity of the catalysts. In ethanol oxidation, the temperature of 50 % conversion decreased with increasing platinum content. This increase in catalytic performance was more pronounced for the catalysts with 0.59 mass % and 1.00 mass % Pt. On the other hand, higher amount of by-products (mainly acetaldehyde) was observed at increased platinum loadings. For all catalysts, a correlation between their H2-TPR profiles and catalytic performance was revealed. In toluene oxidation, only the catalysts with 0.59 mass % and 1.00 mass % Pt exhibited a lower temperature of 50 % conversion than pristine ceria-zirconia. The effect of platinum loading was less pronounced than in ethanol oxidation and a correlation between reduction behaviour and catalytic performance was not observed. The superior catalytic performance of the catalysts with 0.59 mass % and 1.00 mass % of Pt in both ethanol and toluene oxidation was ascribed to the presence of large platinum nanoparticles, which were not observed at lower Pt loadings.

Synthesis of Pt/C Fuel Cell Electrocatalysts: Residual Content of Chloride and Activity in Oxygen Reduction

Graphical AbstractTransmission electron micrographs (TEM), the corresponding Pt particle size distribution histograms, and chemical analysis for residual Cl content by instrumental neutron activation analysis (INAA) and X-ray photoelectron spectroscopy (XPS) of selected representative Pt/C fuel cell catalysts.

Development of tailored high-performance and durable electrocatalysts for advanced PEM fuel cells

Abstract A family of novel carbon materials with intermediate surface area and varying morphology and surface chemistry were used to prepare Pt/C catalysts by two different preparation procedures; a chemical impregnation method and a microwave-assisted polyol method. The catalysts were thoroughly characterized, and their electrochemical performance and stability were investigated with rotating disc electrode (RDE) cyclic voltammetric (CV) measurements. The intermediate-surface-area carbon supports gave catalysts with much greater support stability than a widely used standard catalyst. The novel catalysts had lower electrochemical surface area than the reference, but their specific electrocatalytic activity towards the oxygen-reduction reaction (ORR) was much higher, and some of them also featured higher mass-specific ORR activity than the reference. The series of catalysts prepared by the microwave-assisted polyol method featured smaller Pt nanoparticles and higher activities than those prepared by impregnation. On the other hand, the impregnated catalysts showed better durability of the Pt particles. The most promising catalysts were selected and elaborated in further optimized preparation procedures to obtain quantities sufficient for their use in proton-exchange membrane fuel cells (PEMFCs).