Daniela Gulková

Silica-ceria as support for the preparation of NiMo(P) hydrodesulfurization and hydrodenitrogenation catalysts

Abstract New macroporous silica-ceria support was synthesised and tested in the preparation of NiMo(P) sulfide catalysts differing in the way of Mo and phosphorus introduction. Activity of catalysts in parallel HDN of pyridine and HDS of thiophene was compared with activity of a commerical NiMoP/alumina catalyst. Catalysts prepared from silica-ceria have higher HDS and HDN activities, produce a significantly lower amount of intermediate piperidine and possess the HDN/HDS selectivity comparable with the alumina supported catalyst. These properties can be ascribed both to the specific properties of support and phosphorus. Deposition of MoO 3 was accompanied by consumption of OH groups of silica-ceria support; it was found that phosphorus facilitates significantly this raction. The higher consumption of OH groups was in relation with increased activity of NiMoP catalysts; we suppose this behaviour is connected with a higher dispersion of the Mo phase.

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

Preparation and properties of Pt-Mo sulfide system supported on mesoporous silica-alumina

The preparation and properties of Mo and Pt-Mo systems (14 wt.% Mo, ∼ 0.5 wt.% Pt) on a mesoporous silica-alumina (MSA) were studied. The Mo catalysts were characterized by X-Ray diffraction, N2 adsorption-desorption and transmission electron microscopy (TEM). The sulfided catalysts were tested in the simultaneous HDS of thiophene and HDN of pyridine. Deposition of ammonium heptamolybdate on MSA followed by sulfidation at 400°C for 4 h gave a well dispersed MoS 2 phase, as confirmed by TEM. The addition of about 0.5 % Pt to the sulfided Mo(S)/MSA led to the significant improvements of HDS and HDN activities. Pt(acac) 2 was more efficient Pt precursor than H 2 PtCl 6 and Pt(NH 3 ) 4 Cl 2 . The temperature of the sulfidation and the composition of the sulfiding gas during activation of the Pt promoted catalyst had only smaller influence on activity.

Effect of support on the synergy in HDS of thiophene and HDN of pyridine over Mo sulfide catalysts promoted by Rh

The effect of support (SiO2-Al2O3, Al2O3,MgO) of the Rh-Mo(S) sulfide catalysts on the synergy in hydrodesulfurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine was studied. The synergy in HDS was between 7–10 regardless of the kind of support used. The synergy in HDN varied from none over the MgO supported sample to about 3 over SiO2-Al2O3 supported catalyst, in accord with the positive effect of increasing support acidities.

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).