Showing papers by "Tanya Tsoncheva published in 2007"
TL;DR: In this article, mesoporous CeO2 was synthesized by using CMK-3 carbon as a structure matrix, and the obtained products exhibit uniform pore walls with a diameter of ca. 5nm in a two-dimensional hexagonal periodic arrangement, as well as interparticle porosity.
119 citations
TL;DR: In this paper, several SBA-15 type mesoporous silicas, where different means of surfactant removal have been used, have been modified by copper and iron oxide, and tested as catalyst for methanol decomposition.
Abstract: Several SBA-15 type mesoporous silicas, where different means of surfactant removal have been used, have been modified by copper and iron oxide, and tested as catalyst for methanol decomposition. The materials were thoroughly characterized by nitrogen physisorption, X-ray diffraction, Moessbauer spectroscopy and temperature programmed reduction with hydrogen. The different means of template removal results in SBA-15 materials different in mesopore size and degree of microporosity. These parameters have a strong influence on the reductive and catalytic properties of the obtained composite materials.
37 citations
TL;DR: In this article, a nanosized nickel ferrite/silica composites are synthesized using the sol-gel method using X-rays diffraction, Mossbauer and infrared spectroscopies, magnetic measurements and thermo-programmed reduction with hydrogen.
Abstract: Nanosized nickel ferrite/silica composites are synthesized using the sol–gel method. X-rays diffraction, Mossbauer and infrared spectroscopies, magnetic measurements and thermo-programmed reduction with hydrogen are used for their characterization. Significant differences in their catalytic activity and selectivity in methanol decomposition to CO and methane, depending on the ferrite/silica ratio, the annealing temperature and the phase transformations of the samples by the reaction medium are observed.
26 citations
TL;DR: In this article, the dispersion and intimate contact between the obtained gold and iron particles are affected not only by the preparation method and pretreatment temperature used, but also by the pore accessibility of the host matrix.
17 citations
TL;DR: In this article, phase composition and structural properties of iron-nickel oxides are investigated by X-ray diffraction and Mossbauer spectroscopy, and their catalytic behavior in methanol decomposition to CO and methane is tested.
Abstract: Iron-nickel spinel oxide NiFe2O4 nanoparticles have been prepared by the combination of chemical precipitation and subsequent mechanical milling. For comparison, their analogue obtained by thermal synthesis is also studied. Phase composition and structural properties of iron-nickel oxides are investigated by X-ray diffraction and Mossbauer spectroscopy. Their catalytic behavior in methanol decomposition to CO and methane is tested. An influence of the preparation method on the reduction and catalytic properties of iron-nickel samples is established.
12 citations
TL;DR: In this paper, a comparison of manganese and rhenium modified activated carbon materials as catalysts in methanol decomposition to CO and hydrogen is presented. But the determining role of the Mn(II) ions in the improvement of the catalytic properties is assumed.
Abstract: Bicomponent manganese and rhenium modified activated carbon materials, prepared by different methods, are studied and compared with the corresponding monocomponent materials as catalysts in methanol decomposition to CO and hydrogen. The best catalytic activity and stability is observed for the sample obtained by simultaneous deposition of Mn and Re precursors. The complex character of the catalytic active centre, including manganese and rhenium irons in various oxidative states, is discussed. The determining role of the Mn(II) ions in the improvement of the catalytic properties is assumed.Key words: rhenium, manganese, activated carbon, methanol decomposition.
11 citations