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, the potential commercial cobalt catalysts are typically composed of four components: Co metal, a small amount of a second metal, oxide promoters (alkali, rare earth, and/or transition metal oxide such as ZrO 2 ) and supports (silica, alumina or titania
(where Me x O y is SnO 2 , WO 3 , Cr 2 O 3 and ZrO 2 ) have been investigated in a work [ 4 ]. It has been found that zirconium dioxide can inhibit the polymorphic transformation of anatase to rutile [ 4 – 7 ]. As is shown in [ 8 , 9 ], the ZrO 2
Abstract
The pigments used in ceramic applications are of nature predominantly inorganic and they should be thermally stable, insoluble in glazing, resistant to the chemical and physical agents' attacks. This work aimed at the synthesis by the polymeric precursor method of ZrO2-based inorganic pigments, doped with Fe, Ni, Co, Cr and Cu cations. The fired pigments were characterized by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction (XRD). Among the metals used to zirconium-doping, the best result was achieved with the cations Cu, which presented the monophase pigment, even as 20 mol% of dopant. Up to the temperature of 1000C the pigments presented a good thermal stability.
The behaviour of zirconium oxide ZrO2 during its heating in the temperature range 300–2670 K under high-vacuum conditions and at different heating rates has been studied.
compounds are used in fire retardant systems as synergistic agent because they can act as the solid acids that catalyze their dehydrogenation of the polymer. In this article, nano-ZrO 2 is employed to improve flame retardancy of PMMA together with TPP. The
/H 2 O, due to the high deactivation rate of the catalyst, it has hardly undergone successful application in commercial plants. In our previous investigations for the CDR reaction [ 3 ], we have reported that CeO 2 –ZrO 2 is a very effective promoter
Preparations were characterized by specific surface area, thermogravimetry, and X-ray diffractometry. Thermal effects observed were (a) sulfur loss, (b) sintering, (c) crystallization and transformation of the crystalline phase(s). Thermoanalytical curves indicate that decomposition of the sulfate occurs in two distinct steps. Decrease of surface area due to (b) and (c) is concomitant to decomposition of sulfate. Sulfate was found to hinder sintering, crystallization and phase transformations of ZrO2 and TiO2. In low-titania and -zirconia sulfated TiO2-ZrO2 the minor component enhances the effect of sulfate. In equimolar TiO2-ZrO2 sulfate decomposition is accompanied by rapid formation of crystalline TiZrO4.
Abstract
Zirconia samples with different structures (monoclinic, tetragonal or a mixture of the two) was prepared by different methodologies, including a novel procedure involving the precipitation of an oxalate precursor and the formation of pure tetragonal ZrO2. The different precursors obtained by varying the preparative procedure (ex oxychloride, ex oxalate, and ex gel) were studied by means of differential thermal analysis and thermogravimetric analysis under air and under N2, while the final oxides were characterized by BET, porosimetry and XRD analysis. The surface acid-base properties of the different oxides were assessed via the catalytic decomposition isopropanol. A prevalence of acid sites found for the ex-oxalate ZrO2 seems to justify the different mechanism of chain growth observed in the carbonylation of methanol with CO/H2 mixtures in the presence of Rh.
of the support, which plays an important role in the palladium–support interaction. In recent years, Al 2 O 3 –ZrO 2 based materials have been employed as catalysts in numerous catalytic applications [ 17 – 19 ]. In fact, zirconia is one such
Abstract
The reaction of direct transformation of ethanol to ethyl acetate was investigated on reduced Cu/ZrO2 catalysts prepared by a co-precipitation procedure. The catalytic performances of these Cu–Zr mixed oxides were considerably influenced by changing the molar ratio of Cu to Zr. The highest selectivity to ethyl acetate was found over Cu/ZrO2(1) catalyst (molar ratio of Cu to Zr was 1). A variety of characterization techniques, such as N2 adsorption, XRD, XPS, TPR and NH3-TPD were carried out on the catalysts. The results revealed that the presence of a certain amount of Cu+ species may play very important role in improving the selectivity to ethyl acetate of the Cu/ZrO2 catalysts.
