Influence of the synthesis method on THE DTG-TPR profiles of Pt/WOx–ZrO2 bifunctional catalysts

Structural and Morphological Characterization of Pt/WO x –ZrO2 Catalysts

“…In these samples the platinum crystalline phase was identified by two peaks in 2h equal to 39.8°and 65.6°. Metallic platinum was also previously found in other works when the platinum was added before calcination [4,10,15].…”

“…The preparation of solid acids catalysts of the type WO x -ZrO 2 usually is made by impregnation of precipitated zirconium hydroxide with a solution of ammonium metatungstate or by co-precipitation with ammonia from a solution containing zirconium oxychloride and ammonium metatungstate [9][10][11][12]. Other methods have been also used to prepare this oxide, including the sol-gel [13], hydrothermal synthesis [14], polymeric precursor method [15] and using reverse micelles [12]. In accordance with previous works by Arata and Hino [1,9] the hydrous zirconia precursor is required for the anchoring of tungstate anions.…”

Acid and redox properties of tungstated zirconia catalysts

“…Table 1 shows the weight loss at 200, 400, 700, 900°C respectively. Analyzing the TGA results, a calcination temperature of 700°C confirms that most of the OH groups physically or chemically adsorbed on the surface were removed and that this temperature is high enough to decompose any precursor eventually still present, and facilitate the adhesion and condensation of tungstated species on the ZrO 2 surface [15]. More or less significant differences in the surface properties between the tungstated zirconia samples and the bare ZrO 2 support emerged from the various techniques used for characterizing the samples.…”

“…Reduction profiles reported in Fig. 3 show a reduction peak centered around 480°C which could be attributed to the first step of WO 3 reduction, while the other broad reduction peak centered around 910°C can be related to the complete reduction of WO 3 and to the reduction of tetrahedrally coordinated WO x species (amorphous and non-stoichiometric oxides) strongly anchored to the zirconia surface [24].…”

Activation of ZrO2–WO3 solid acid catalysts in a Friedel–Crafts reaction through post-hydrothermal treatment

“…6). While, two peaks of ZrO 2 -WO 3 -AH sample, about 640 C and 720 C, ascribed to reduction of WO 3 species (amorphous and non-stoichiometric WO 3 ) 36,37 shi to lower reduction temperature, compared with the peak above 800 C of ZrO 2 -WO 3 . The two reduction step suggested a growth of WO x with W-O-W linkages; because linked WO x are reduced at lower temperatures than isolated WO x species.…”