Nowadays, efficient thermal insulation is a principal requirement for buildings and, accordingly, huge amounts of insulators are applied in the constructions, particularly for external walls, radiant floor, roofs, etc. Acoustic insulation is another of the most stringent parameters to be taken into account both in the construction of new buildings or their rejuvenation in order to obtain good internal comfort. Notwithstanding these needs, only few materials are marketed which feature reasonably good both thermal and acoustic insulation properties. More often, materials with good sound insulation proprieties show poor thermal efficiency and vice versa. Further, most of materials which have good both acoustic and thermal properties are thicker than either acoustic or thermals insulators which creates technical difficulties in their use, particularly in the buildings’ renovation. Nano-structured materials such as, for example, microporous or aerogel materials, are characterised by highly efficient thermal insulation power, in spite of their reduced thickness compared to conventional systems.

In relation with the applications of CeO2-ZrO2 mixed oxides in catalysis, new synthetic routes aim at preparing materials with improved performances in terms of durability and high temperature textural and chemical resistance [1]. Barium-doped alumina (BDA) as well as Barium hexaaluminates (BHA), BaO·6Al2O3, present high thermal stability, this making them suitable supports of highly dispersed catalytic active phases, e.g. in combustion processes [2]. Thus, these materials seem appropriate to prepare supported CeO2-ZrO2 catalysts with improved high temperature stability.

The effects of ZrO2 content on the CO oxidation activity in a series of CuOx/CexZr1−xO2 (x=0, 0.15, 0.5, 0.7 and 1) catalysts were investigated, both in the absence and in the presence of H2, i.e. preferential CO oxidation—PROX. The investigation was performed under light-off conditions to focus the effects of transients and shut-down/start-up cycles on the performance; such phenomena are expected to affect the activity of PROX catalysts in small/delocalised fuel reformers. Evidence has been obtained for a transition from an “oxidized” towards a “reduced” state of the catalyst under the simulated PROX reaction conditions as a function of the reaction temperature, leading to different active species under the reaction conditions. Both CO oxidation activity and PROX selectivity appear to be affected by this process. IR characterisation of the surface copper species suggests an important role of reduced cerium sites in close contact with copper clusters on the CO oxidation activity at low temperatures.

Nanostructured CeO2–ZrO2 mixed oxides have attracted great interest in the past 10 years, in particular as redox or oxygen storage promoters in the three-way catalysts. However, it has now became clear that both the chemistry of the simple oxides and the complex metal–CeO2-based oxide interactions can play a critical role in developing novel and highly active materials for a number of processes, ranging from catalysts for H2 production from fuels up to ceramic materials and solid state conductors for fuel cells. Despite the apparent simplicity of these systems, extreme variability of their chemical and textural properties has been observed. An attempt is made here to rationalise the various factors and the inter-connections to the structure, the texture, and the effects of the nanometre scale, which all contribute to the properties of these materials.

Evidence is presented that the well-established phenomenon of promotion of Ce0.5Zr0.5O2 reduction by suitable treatment procedures may be controlled by adjusting the conditions; and that such reduction leads to the formation of the pyrochlore structure at extremely low temperature.

In this paper we report on the laser-excited Raman and luminescence spectroscopy of a series of ceria-zirconia mixed oxides, containing trivalent lanthanide ions as unintentional impurities, using 488.0-, 514.5-, and 1064.0-nm excitation wavelengths. We assigned the main bands located at Stokes shifts higher than 800 cm(-1) from the laser lines to f-f emission transitions of Pr3+, Nd3+, Ho3+, and Er3+ ions. These ions can also be used as spectral probes of the cation sites in the solid solutions as their transition intensities are found to be dependent on the local symmetry of the sites in which they are accommodated. f-f emission transitions have also been found to overlap the vibrational Raman bands for Stokes shifts lower than 800 cm(-1) from the laser lines. To overcome possible ambiguities in the structural information extracted from the Raman spectra, at least two laser excitation lines must be used.

Thermal stability and dispersion of CeO2 supported on Al2O3 is greatly improved by insertion of ZrO2 into the CeO2 lattice. It is shown that homogeneous nanosized CexZr1-xO2 solid solutions can be prepared on the Al2O3 surface by using a citrate complexation synthesis method. Investigation of effects of CexZr1-xO2 composition and loading of the Ce0.2Zr0.8O2 phase on thermal stability and nanostructure of the prepared materials revealed that strong interactions between the supported phase and Al2O3 are induced by the high-temperature treatment. High contents of ZrO2, choice of the CexZr1-xO2 precursors, and loading of the mixed oxide are critical factors leading to nanocomposite systems with high thermal and structural stability, consisting of particles of Ce0.2Zr0.8O2 as small as 9-20 nm in close contact with a theta-AI(2)O(3) matrix even after calcination at 1373 K. The enhanced stability of the present materials was confirmed also under hydrothermal conditions.

A deactivated (aged under redox-cycled model TWC feed-stream) Pd/Ce(0.68)Zr(0.32)O(2) catalyst is remarkably reactivated when subjected to a high temperature oxidising treatment whereas this effect is only marginal for Pd/Al(2)O(3), which indicates the key role of such treatment in restoring the Pd-Ce(0.68)Zr(0.32)O(2) interactions leading to highly active catalysts.

Single phase homogeneous CeO2–ZrO2 solid solutions with various compositions were synthesized using a citrate complexation route. Investigation of the sintering behaviour disclosed important modifications of the textural and, in particular, structural properties, which apparently create a strongly defective structure that could explain the unusual redox properties of these catalytic systems.

Adsorption of CO-, NO- and CO/NO-containing mixtures was investigated by in situ IR spectroscopy under flow conditions over Pd/δ-Al2O3 and Pd/Ce0.6Zr0.4O2/δ-Al2O3. The attention is focused on the effects of Ce0.6Zr0.4O2 addition to Pd/Al2O3 on the catalytic properties and reaction intermediates. Linearly bonded and bridged CO species adsorbed on palladium were clearly identified on Pd/Al2O3 while CO adsorption is inhibited under reaction conditions in the presence of Ce0.6Zr0.4O2. Addition of Ce0.6Zr0.4O2 affects the nature of the Pd sites by stabilizing oxidized dispersed Pd species. Evidence is obtained that the presence of the Ce0.6Zr0.4O2 solid solution modifies the adsorption properties of the supported Pd species and promotes the reduction of NO below 500 K via an alternative mechanism. This presumably involves reactive oxygen species at the Pd–Ce0.6Zr0.4O2 interface generated by the redox Ce4+/Ce3+ couple.

The effects of redox-ageing on the temperature-programmed reduction and dynamic oxygen storage were investigated on two samples of Ce0.6Zr0.4O2 prepared under different synthesis conditions. It was observed that a high-temperature reduction/mild oxidation redox cycle can generate temperature-programmed reduction (TPR) profiles featuring a reduction peak at a temperature as low as 537 K. However, despite such favourable reduction behaviour, a strong deactivation of the oxygen storage is observed under dynamic conditions, indicating the limitations of the TPR method for investigation of oxygen storage.

By impregnating γ-Al 2 O 3 with cerium/zirconium citrate solutions and subsequent calcination nanostructured Ce m Zr 1−m O 2 mixed oxides supported on Al 2 O 3 are obtained, which feature remarkably high oxygen storage even after a calcination at 1373 K for 24 h. Mutual thermal stabilisation between alumina and solid solutions has been observed, which prevents formation of α-alumina and sintering effects after a severe ageing.

Pd-loaded Ce0.6Zr0.4O2 solid solutions supported on Al2O3 are investigated as catalysts for the reduction of NO by CO. The attention is focused on the role of the Ce0.6Zr0.4O2 and of the Pd dispersion on the catalytic activity. The system shows a very high activity below 500 K, which is almost independent on the Pd dispersion. The high activity is attributed to a promoting effect of the Ce0.6Zr0.4O2 on the NO conversion. Investigation of the influence of high temperature treatments disclosed a thermal stabilisation of both Ce0.6Zr0.4O2 and Al2O3 in the Ce0.6Zr0.4O2/Al2O3 system.

By impregnating gamma -Al2O3 with cerium/zirconium citrate solutions and subsequent calcination, nanostructured CemZr1-mO2 mixed oxides supported on Al2O3 are obtained, which feature remarkably high oxygen storage even after calcination at 1100 degreesC for 24 h.

Reduction behaviour and oxygen storage capacity (OSC) of Rh-loaded and metal-free Ce 0.5 Zr 0.5 O 2 mixed oxides is investigated. It is shown that use of different synthetic methods and the homogeneity of the solid solution strongly affect both the reduction behaviour and the total- OSC. Presence of supported noble metal (NM) minimises the differences between the different samples due to the ability of the NM to promote reduction of the Ce 0.5 Zr 0.5 O 2 by activating hydrogen.