CO2 effect on activity and stability of NOx storage reduction catalysts

A catalyst for NO_x storage/reduction was prepared to improve the activity of Ba–Pt/γ-Al₂O₃ by replacing Ba with a mixture of Ba and Mg. The catalyst was prepared by impregnating Pt and then co-impregnating Ba and Mg (Mg:Ba molar ratio = 1) on commercial γ-Al₂O₃. The tests have been carried out in the presence of CO₂ at temperatures between 200 and 400 °C in order to understand the role of both the feed and various alkaline-earth metals. The storage capacity of the two catalysts was different like the mechanism in the reduction process.     

NOx storage-reduction catalysts based on hydrotalcite: Effect of Cu in promoting resistance to deactivation

Novel NO_x storage-reduction (NO_xSR) catalysts prepared by Pt and/or Cu impregnation of Mg–Al (60:40) hydrotalcite (HT)-type compounds show better performances in NO_x storage than Pt–Ba/Al₂O₃ Toyota-type NO_xSR catalysts at reaction temperatures lower than 250 °C. The presence of Pt or Cu considerably enhances the activity, with the former more active. The nature of the HT source, however, also influences performance. The co-presence of Pt and Cu slightly worsens the low temperature activity, but considerably promotes the resistance to deactivation after severe hydrothermal treatment and in the presence of SO₂. This effect is attributed to both the possibility of formation of a Pt–Cu alloy after reduction, and the modification of the HT induced during the deposition of Cu. The overall Pt–Cu/HT performances are thus superior to those of the Pt–Ba/Al₂O₃ Toyota-type NO_xSR catalysts.     

Nano-to-macroporous TiO2 (anatase) by cold sintering process

Cold Sintering Process (CSP) was applied on commercial nanopowders to produce nanostructured TiO₂ anatase with nano-to-macro porosity. Nanoporous TiO₂ based materials were obtained by applying CSP at 150 °C and pressures up to 500 MPa on three TiO₂ nanopowders with different specific surface area (s.s.a. = 50, 90 and 370 m²/g), using water as transient aqueous environment. Although TiO₂ is insoluble in water, a density of 68% and s.s.a. = 117 m²/g were achieved from the powder with the highest specific surface area. A post annealing process at 500 °C increased the density up to 73% with a s.s.a. = 59 m²/g, and the crystallites dimensions passed from 110 Å in the powder to 130 Å in CSP material and 172 Å after post annealing. Finally, macroporosity was produced by using thermoplastic polymer beads as sacrificial templates within TiO₂ nanopowder during CSP, followed by a debonding at 500 °C.     

Si/Zr mesoporous catalysts for the vapour phase synthesis of alkylindoles

Si/Zr mesoporous MCM-41 catalysts were investigated in the vapour phase synthesis of 7-ethylindole (7-ETI) starting from 2-ethylaniline (2-ETAN) and ethylene glycol (EG). The catalysts were prepared from the corresponding alkoxides in the presence of a cationic surfactant, which acts as a structure-directing agent. After removal of the surfactant, the resulting mesoporous solids were characterised by X-ray diffraction, N₂ adsorption–desorption, temperature programmed desorption (TPD) of NH₃ and pyridine adsorption coupled with FTIR spectroscopy. As the amount of ZrO₂ increased in the catalysts, the BET surface area decreased, while an enhancement of the acidity took place. The activation of EG to 2-hydroxyacetaldehyde and its attack on 2-ETAN, leading to the formation of 7-ETI, was favoured by increasing the amount of ZrO₂ The maximum yield for the catalyst was obtained with ca. 50 wt.% of ZrO₂, which promoted the presence of Lewis and Brönsted acid sites of suitable strength and concentration, although mesoporous catalysts exhibited very good regenerability.     

Detection of geophysical features in InSAR point cloud data sets using spatiotemporal models

In this article, we introduce an approach for detecting evolving geophysical features within interferometric synthetic aperture radar (InSAR)-derived point cloud data sets. This approach is based on the availability of models describing both spatial and temporal behaviours of the geophysical features of interest. The model parameters are used to generate a multidimensional space that is then scanned with a user-defined resolution. For each point in the parameter space, a spatiotemporal template is reconstructed from the original model. This template is then used to scan the point cloud data set for regions matching the spatiotemporal behaviour.

We also introduce a proportional measure where the residual for each point in the data set is compared to both the data and the template to provide a scale invariant measure of the behavioural matching. The matching is evaluated for every point in the parameter over a region of influence determined by the parameters. The resulting multidimensional space is then collapsed onto geographical coordinates to produce an overlay map identifying regions whose spatiotemporal behaviour matches the feature of interest.

We tailored our approach to the detection of subsidence behaviour, indicative of the development of sinkholes, modelled as Gaussian with amplitude linearly increasing with time. We verified the validity of our model using both synthetic and actual InSAR data sets. The latter was obtained by processing imagery of a region near Wink, Texas, containing ground truth sinkhole data.

We applied this framework to a 40 km × 40 km area of interest located in western Virginia and performed ground validation on a subset of the identified regions. The results show good agreement between the locations detected by our algorithm and the evidence of subsidence observed during the ground validation campaign.     

Environmentally friendly vapour phase synthesis of alkylquinolines

2-methyl-8-ethylquinoline (MEQUI) was synthesized from ethylene glycol and an excess of 2-ethylaniline, operating in the vapour phase on K10 montmorillonite. Its structure was confirmed by ¹H-NMR (200 MHz) spectra recorded in CDCl₃ and DMSO. The synthesis of MEQUI is favoured by increasing the reaction temperature and amount of ethylene glycol, operating in a partially reducing atmosphere and feeding small amounts of water inside the organic feed. A possible reaction pathway proposed was confirmed by feeding a 2-ethylaniline/crotonaldehyde mixture. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fundamentals in the preparation of heterogeneous catalysts

The preparation of heterogeneous catalysts has by now lost all empirical aspects. The approach is scientific and involves a wide number of specific competencies of solid state chemistry, analytical chemistry, physical chemistry, kinetics, rheology, etc. The fundamental aspects in the preparation of heterogeneous catalysts starting from catalyst design up to the catalyst in its final form are briefly reviewed, with focus on the key factors in each preparation step and the main differences between laboratory and industrial scale preparations. The main properties of monolithic catalysts and their preparation methods are also reported, considering their relevance for environmental applications.