Acid–base properties and catalytic activity of nanophase ceria–zirconia catalysts for 4-methylpentan-2-ol dehydration

Abstract

The room-temperature high energy ball-milling technique was used to prepare nanophase (x \ 0 ; Ce 1~x Zr x O 2 0.2 ; 0.5 ; 0.8 ; 1) catalysts. The acidÈbase properties of these catalysts were investigated by means of adsorption microcalorimetry, using and as probe molecules. The catalytic activity for 4-methylpentan-2-ol NH 3 CO 2 dehydration was tested at atmospheric pressure in a Ðxed-bed Ñow microreactor. The inclusion of increasingly high contents of zirconium into the ceria lattice has a complex inÑuence on the acidity and basicity of the pure parent oxide, in terms of both number and strength of the sites. A maximum in 1-alkene selectivity is observed for the ceria-rich catalyst and a minimum for the zirconia-rich sample. Catalytic results are correlated with the acidÈbase properties and can be interpreted in the light of the mechanism formerly proposed for zirconia, ceria and lanthania. Surface conditioning of the zirconia-rich catalyst occurs during the run, resulting in a remarkable variation of selectivity.

Ceria‐Based Solid Catalysts for Organic Chemistry

“…The unsupported mixed oxides CeO 2 -ZrO 2 [41][42][43] and CeO 2 -La 2 O 3 , [42,44,45] and CeO 2 -ZrO 2 supported on SiO 2 [46][47][48] have been used for this reaction, in the vapor phase under normal atmospheric pressure of N 2 between 250 8C and 400 8C. It was observed that these catalysts exhibit high and stable catalytic activities.…”

Catalytic Efficiency of Ceria–Zirconia and Ceria–Hafnia Nanocomposite Oxides for Soot Oxidation

“…This modification has often been attributed to changes in the redox properties and the creation of oxygen vacancies [5,6]. Incorporation of Zr 4+ into CeO 2 lattice has been reported to improve the physicochemical characteristics of ceria and this combination has been applied for various reactions such as preferential oxidation of CO [7,8], steam reforming of ethanol [9], synthesis of dimethyl carbonate from methanol and CO 2 [10], direct conversion of methane to synthesis gas [11], iso-synthesis [12], dehydration of alcohols [13][14][15][16][17], oxidative dehydrogenation of ethylbenzene [18] and low-temperature water-gas shift reaction [1], apart from the conventional TWC applications to reduce the emissions of noxious pollutants such as CO, NO x and hydrocarbons from automobile exhausts [2,19].…”

Investigation of 12-Tungstophosphoric Acid Supported on Ce0.5Zr0.5O2 Solid Solution

“…Ce 4+ charge transfer transitions in UV region, and the combination and overtone bands of surface hydroxyl species in NIR region [2]. This is an evidence for the presence of surface O 2--Ce 3+ , O 2--Ce 4+ sites and -OH groups attached primarily to Zr 4+ ions giving rise to both acid and base properties [10]. The surface structural changes and non-stoichiometry introduced by Zr 4+ incorporation can lead to surface acid-base pair sites.…”

“…To our knowledge, there has been one report where the removal of NO x is studied on H 3 PW 12 O 40 Á 6 H 2 O supported on Ce x Zr 4-x O 8 [21]. We chose to investigate Ce 0.5 ZrO 0.5 O 2 solid solution which contains mild Lewis acid and base sites on the surface [2,10] and is expected to show balanced acid-base properties due to statistically equal number of Zr 4+ and Ce 4+ ions present in the lattice. These surface sites along with oxygen ion vacancies associated with Ce 3+ /Ce 4+ redox centers can interact with heteropoly anion species.…”