Authors:Viorel Chihaia, Karl Sohlberg, L. Ilieva, P. Petrova, T. Tabakova, R. Zanella, and Z. Kaszkur
Gold catalysts supported on ceria doped with different metal oxides (Fe, Mn, Co and Sn) were synthesized using two techniques: CP and mechanochemical activation. The catalytic activity in complete benzene oxidation (CBO) was studied. The samples were characterized by means of XRD and high resolution transmission electron microscopy, and non-significant differences in the average size and the distribution of gold particles were observed. This means that the main reason for the different catalytic behavior in CBO has to be searched in the composition and structure of the supports. In spite of the higher hydrogen consumption (e.g., higher oxygen mobility) estimated by means of TPR, the gold catalysts on ceria doped with transition metal oxides generally are less active than gold/ceria catalyst. This observation could be explained taking into consideration that the key factor for the high oxidation activity is not the oxygen supplying but the activation of the very stable benzene molecule. The higher catalytic activity in comparison with that of the gold/ceria catalyst was observed only using a mixed ceria–CoOx support mechanochemically prepared. Very high and stable catalytic activity in CBO was obtained over this sample.
Authors:L. Ilieva, G. Munteanu, P. Petrova, T. Tabakova, N. Velinov, and I. Mitov
Gold catalysts supported on ceria doped with FeOx were studied. The mixed supports were synthesized by two methods: co-precipitation (CP) or mechanochemical activation (MA). Depending on the preparation method, the structure of the mixed supports was different: using CP, only a Fe-modified ceria phase exists, while supplementary to ceria, a second hematite phase presents in the case of MA preparation. The reduction behavior of the gold catalysts and the initial supports was commented on the basis of hydrogen consumption and kinetic parameters of the individual reduction process. Their assignment was proposed using also the data of Mössbauer measurements. It was established that the existing separate Fe-containing phase could participate in a redox process at relatively low temperatures (LTs) and it could be promising for improvement of the catalytic performance of the mechanochemically prepared gold catalyst.
Authors:M. Subchev, T. Toshova, R. Andreev, V. Petrova, V. Maneva, T. Spasova, N. Marinova, P. Minkov, and D. Velchev
Field investigations with CSALOMON® floral-chemical baited color traps for scarab beetles (Coleoptera: Scarabaeidoidaea) were organized in eight sites in different regions in Bulgaria during 2009–2010. As a result data about distribution and seasonal flight were obtained for the target species Cetonia aurata L. and Protaetia cuprea (Fabricius) and two other non-target species, Valgus hemipterus L. and Blitopertha lineolata (Fischer von Waldheim). Catches of C. aurata were recorded in all of the sites where observations were organized but the number of the beetles caught was relatively low. The earliest catches of this pest were registered in the middle-end of April and the latest ones in early August. Single catches of P. cuprea, not allowing doing conclusions about seasonal flight for this species, were recorded only in Dryanovo, Knezha, Plovdiv and Troyan. Catches of V. hemipterus, were registered in all of the sites with the exception of Petrich. The flight period of this species, as established by catches in the traps, was middle-end of April — early June. Significant number of B. lineolata was caught in Dryanovo in 2009 and single catches in Plovdiv in 2009 and Kyustendil in 2009 and 2010. The earliest catches for the two years in Dryanovo were registered in the middle-end of May and the latest ones in the middle of June. This is the first report about floral-chemical attractant for this species. For all four species the relative catches in traps for C. aurata/P. cuprea, Tropinota (Epicometis) hirta (Poda) and Oxythyrea funesta (Poda), operating simultaneously in the investigated sites, were presented and analyzed.