The aim of this paper was to investigate the physicochemical properties of palladium catalyst containing basic support MgO which was used in hydrodechlorination reaction with carbon tetrachloride. In order to characterize the investigated sample the catalyst was put to tests of XRD, TOF - SIMS, TG-DTA-MS and TPRH2 measurements, activity tests were also performed. The XRD and TPR results demonstrated the presence of PdOxCly species whose decomposition takes place above 700°C. The calcination of the Pd/MgO catalyst at 700°C resulted in the transformation of PdOxCly to PdO.
Nb2O5/Al2O3 materials prepared by sol-gel method using aluminium hydroxychloride and potassium niobate solutions were used as supports for nickel catalyst. 2 wt. % Ni catalysts were investigated by temperatureprogrammed reduction, TEM, X-ray diffraction, hydrogen chemisorption and high-resolution transmission electron microscopy (HRTEM). Hydrodechlorination (HDC) of 1,2-dichloroethane (1,2-DCA) over alumina modified by niobia supported nickel catalysts led to formation of ethylene as desired product. Selectivity toward C2H4 increases from ~35% for 2%Ni/Al2O3 up to 90% for Ni/Nb2O5- Al2O3. This phenomenon is an effect of the coexistence of Nb2O5 and Al2O3. Niobia is preferentially located over alumina, shaping the overall catalytic behavior of Nb2O5 – Al2O3 supported catalysts. This phenomenon could be related with the changes between Brönsted and Lewis acidic active sites ratio. Temperature programmed hydrogenation (TPH) of post-reaction deposits showed that during HDC on catalysts surface both carbon and chlorine-containing species were formed. Application of regeneration procedure (3h, 10%H2/Ar, 600°C) for spent samples led to efficient reconstruction of active sites.
Two step modification of Norit CNR115 active carbon led to formation of mesoporous turbostratic carbon structure. Ni-Pd catalysts were prepared by incipient wetness impregnation of turbostratic active carbon with an aqueous solution of nickel and palladium chloride salts and were investigated by the Temperature-Programmed Reduction (TPR), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), X-Ray Diffraction (XRD) and Temperature- Programmed Hydrogenation (TPH). The aqueous-phase hydrodechlorination of 1,1,2-trichloroethene (TCE) were carried out in a batch reactor at room temperature. Addition of palladium to nickel catalysts resulted in increasing of TCE conversion from 85% for Ni100 to more than 90% for Ni95Pd05 after 150 minutes of reaction. Aqueous-phase hydrodechlorination of TCE led to the formation of hydrocarbons (ethane and ethene) as the main products. Temperature-programmed hydrogenation of the catalysts after kinetic run have shown that during reactions with TCE only a small amount of carbon species were deposited on the catalysts surface and that chloride species were not observed.
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used in order to obtain the information about the surface composition of Pd/ZrO2-TiO2 catalyst and to estimate the changes in the concentration of particular components on its surface during the hydrodechlorination of CCl4. The results demonstrated that the hydrodechlorination process led to the increase in the concentration of chlorine and the drop in the amount of surface accessible palladium, while the quantity of Pd-Cl bounds did not change considerably. It suggested that the presence of ZrO2 protected the surface of the studied catalyst against the formation of PdCl2.
Here, we report the results of screening of the catalytic activity of Pd-containing chitosan beads and cryogels in the cross-coupling reaction, hydrogenation of alkenes, nitro-, and carbonyl compounds and the hydrodechlorination of chlorophenols. Pd0-containing chitosan beads and cryogels show moderate catalytic activity in the reduction of alkenes and nitroaromatics. The conversion of nitroaromatics decreases for substrates with electron-withdrawing substituents, while the conversion of alkenes increases with the activation of carbon-carbon double bonds. For several substrates, a significant difference in kinetics and conversion degrees was observed for Pd nanoparticles supported on chitosan beads and cryogels. It was found that conversion in the hydrodechlorination reaction depends on substrate structure, being higher for substrates containing substituents with a positive mesomeric effect. Pd2+-chitosan catalysts showed high catalytic activity in cross-coupling (Heck reaction) offering the following advantages over known catalytic systems: lower reaction temperature, the selective functionalisation of C-I bonds, and the possibility to perform reactions with iodobenzene without base addition.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.