Janusz Trawczyński

Some catalytic properties of hydrothermally synthesised zinc aluminate spinel

Abstract Two samples of zinc aluminate were hydrothermally synthesised from zinc acetate and different aluminium sources: basic aluminium nitrate or aluminium hydroxide. The textural properties of the prepared ZnAl 2 O 4 samples are different from these one of the zinc aluminate prepared by conventional way. Powder XRD and TEM measurements reveal that samples are single-phase material or mixture of ZnAl 2 O 4 with small amount of γ-Al 2 O 3 , with morphology of quasi-spherical shape. Catalytic properties of the hydrothermally obtained zinc aluminate and Pt (Pd) catalysts supported on them were investigated in the reactions of cyclohexene isomerisation and combustion of trichloroethylene, respectively. It was evidenced that activity and selectivity of the investigated materials could be qualitatively correlated with the part of the strong acid centres measured by TPD of NH 3 .

Catalytic combustion of trichloroethylene over TiO2-SiO2 supported catalysts

Combustion of trichloroethylene (TCE) on Cr2O3, V2O5, Pt or Pd catalysts supported on TiO2-SiO2 as a carrier has been investigated. It was found that oxide catalysts are very active but their activity quickly diminishes due to loss of the active component, especially at higher reaction temperatures and/or at high concentrations of TCE in the feed. Addition of water to the feed results in slower deactivation. The noble metal-based catalysts have a lower activity than the oxidic ones, but they are stable during the test and can be used under more severe conditions: higher temperature and high concentration of chlorine. Pt/SiO2-TiO2 is mildly and reversibly poisoned during the reaction. TiO2-SiO2 appears to be a stable and resistant support of catalysts for TCE combustion.

Noble metals supported on carbon black composites as catalysts for the wet-air oxidation of phenol

Abstract Pt, Pd and Ru catalysts supported on carbon black composites (CBC) were characterized in the wet air oxidation of phenol solution using a fixed-bed reactor working in a trickle-flow regime under relatively mild conditions: temperature, 393–433 K; pressure, 50–80 bar; liquid hourly space velocity (LHSV), 0.5–6 h −1 . The activity of the catalysts decreases in the following order: Pt/CBC>Pd/CBC≈Ru/CBC≫CBC. The physicochemical properties of the CBC are affected by its reaction with oxygen during the oxidation process. Combustion of the CBC material in the aqueous phase proceeds at a lower temperature than that in the gas phase; its surface properties change according the same rules as during low temperature oxidation by gaseous air.

Effect of synthesis conditions on the hydrodesulfurization and hydrodenitrogenation activities of alumina supported Mo and CoMo nitrides

Abstract The catalytic activity of alumina-supported molybdenum as well as cobalt–molybdenum nitrides for simultaneous hydrodesulfurisation (HDS) and hydrodenitrogenation (HDN) of vacuum gas oil (VGO) doped with quinoline was investigated. The relationship between nitriding parameters and activity was studied. Catalytic activities of nitrided and sulfided form of Mo as well as CoMo catalysts were compared. Nitrided Mo/Al 2 O 3 proved to be significantly more active in the HDN than the sulfided form of this catalyst. Nitrided Mo/Al 2 O 3 is also slightly more active in HDS than sulfided Mo/Al 2 O 3 . On the other hand, sulfidation of CoMo/Al 2 O 3 leads to a catalyst with a higher HDS activity than nitriding. The HDN activities of both forms of CoMo are almost the same. Addition of cobalt to Mo/Al 2 O 3 improves the HDS and HDN activities in its sulfided form, but has a negligible effect in the nitrided form.

Effect of support activation on the kinetics of indole hydrodenitrogenation over mesoporous carbon black composites-supported molybdenum carbide

Abstract The catalytic activity of supported molybdenum carbide was examined versus activation of the carbon support. A mesoporous carbon black composite (CBC) support was used and activated with either HNO 3 or H 2 O 2 for 0.5 h. After impregnation and carburisation, the β-Mo 2 C hexagonal compact crystallographic phase was obtained as the unique active phase. Several techniques (porosity measurements, X-ray diffraction (XRD), elemental analysis) were used in order to characterise the catalysts physical properties. The temperature-programmed reduction (TPR) analysis and CO titration performed on these samples underlined an effect of oxidative treatment with H 2 O 2 and HNO 3 on the active phase dispersion. The kinetic study of the hydrodenitrogenation (HDN) of indole on these carbon materials-supported molybdenum carbide was improved when the support was activated.

Effect of synthesis conditions on the molybdenum nitride catalytic activity

Abstract Properties of the molybdenum nitrides supported on alumina as well as on active carbon has been investigated in the reactions of thiophene and vacuum gas oil (VGO) hydrodesulfurization (HDS) as well as in the reaction of cyclohexene with hydrogen. Supported molybdenum nitride was more active in thiophene hydrogenolysis than sulfided Mo/Al 2 O 3 . Also in the reaction of VGO HDS alumina supported molybdenum nitride was more active than sulfided counterpart, however Mo 2 N supported on active carbon exhibit low activity. In the products of the cyclohexene reaction over supported Mo 2 N methyl-cyclopentanes and benzene has been found.

Effect of ammonium salts on alumina surface properties

Abstract Aluminium hydroxides were precipitated from sodium aluminate using ammonium salt solutions. The effect of the kind of ammonium salt used for the aluminium hydroxide precipitation on the surface properties of the related alumina was investigated. It was stated that kind of ammonium salt affects the aluminium hydroxide phase composition as well as the Lewis acid site surface concentration and the concentration of anionic OH − groups; the specific acidity was measured by means of TPD NH 3 and the specific rate of cyclohexene isomerization. DRS spectra of the Mo catalyst supported on investigated aluminas as well as the HDS activity vary with the kind of ammonium salt. The obtained results are explained on the basis of processes both during polycondensation of aquo-ions Al III and during ageing of amorphous hydrogel of aluminium hydroxide. Results are discussed on the basis of the literature.

Surface acidity of the activated CBC

Carbon black composites (CBC) has been prepared from a commercial soot Carbex-330 and were activated according to the following procedures: oxidation by nitric acid, oxidation by hydrogen peroxide, gasification with water steam, ammoxidation, doping with quinoline or silica gel. Surface properties of the above prepared materials were characterized by means of: TPD NH3, acid/base neutralization, TPD in helium, cyclohexene (CHX) reaction in hydrogen. The point of zero charge of the activated CBC was also determined. The effect of the activation procedure on the acid/base surface properties of CBC is discussed.

Reaction of thiophene with hydrogen over CoMo/γ-Al2O3 catalysts. The role of cobalt.

Abstract The reaction of thiophene (T) and hydrogen on sulfided Mo/γ-Al2O3 and CoMo/γ-Al2O3 catalysts is described. The organic sulfur compounds were found in the product. The level of cobalt content in catalyst influences the composition of the products. Different types of active centers have been postulated.

Catalytic combustion of soot

Vanadium pentoxide as well as vanadium + copper and vanadium + molybdenum mixed oxides were supported either on alumina or titania and tested in soot combustion. Effect of support and catalyst composition on catalytic soot combustion was studied.