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An unusual occurrence of asbestiform sepiolite, filling veins in the antigorite serpentinites of the Voltri Unit exposed in a borrow pit (now reclaimed) in the Deiva forest, near Sassello, NW Italy, was investigated with an in-depth analytical approach aimed at studying its crystal-chemistry and structure and evaluating its possible hazards for human health. Optical microscopy and scanning electron microscopy (energy-dispersive spectroscopy mode) proved that these sepiolite fibres, apparently up to several cm long, are made up of bundles of thinner fibrils (or laths: average length > 100 µm; thickness ≈ 80 nm), with a composition consistent to that reported in the literature. The dehydration process was monitored through thermo-gravimetric analyses and Fourier-transform infrared spectroscopy, performed at increasingT; the latter, in particular, showed the presence of moderate amounts of aliphatic hydrocarbons – not yet identified thoroughly – associated with the sample. The crystal structure refinement with the Rietveld method showed no relevant difference from the literature models, although a peculiar distribution of zeolitic H2O molecules was observed. The geological context suggests that the Sassello sepiolite precipitated from hydrothermal fluids, which were saturated in Mg and silica by the interaction of the host serpentinites. The same setting favoured formation of abiotic hydrocarbons, by means of the Fischer–Tropsch reaction. The extremely long and flexible fibrils (length/width aspect ratio >> 3) of this sepiolite specimen could represent a serious hazard for human health if air dispersed and inhaled; also, its atypical association with hydrocarbons (only reported once previously) might even favour further fragmentation in thinner units.

Multivariate XAS analysis and in situ FTIR enable an unprecedented quantitative understanding of the composition impact on temperature-dependent Cu-speciation and reducibility in Cu-CHA zeolite catalysts., The small pore Cu-CHA zeolite is attracting increasing attention as a versatile platform to design novel single-site catalysts for deNOx applications and for the direct conversion of methane to methanol. Understanding at the atomic scale how the catalyst composition influences the Cu-species formed during thermal activation is a key step to unveil the relevant composition–activity relationships. Herein, we explore by in situ XAS the impact of Cu-CHA catalyst composition on temperature-dependent Cu-speciation and reducibility. Advanced multivariate analysis of in situ XANES in combination with DFT-assisted simulation of XANES spectra and multi-component EXAFS fits as well as in situ FTIR spectroscopy of adsorbed N2 allow us to obtain unprecedented quantitative structural information on the complex dynamics during the speciation of Cu-sites inside the framework of the CHA zeolite.

We report about the synthesis and characterization of a microporous CoAPO-5 catalyst. Diffuse Reflectance UV-Vis spectroscopy was employed to follow the changes upon oxidation and reduction treatments, showing that a small fraction of Co2+ ions can be reversibly oxidized to Co3+, responsible for the change of colour from blue to green. A large fraction of Co2+ ions are not oxidized in the employed conditions, in agreement with literature reports. FTIR spectroscopy of adsorbed probe molecules was employed to monitor the surface properties of Co ions. NO adsorption resulted in the formation of two stable Co2+(NO)(2) complexes (bands at 1890/1812 cm(-1) and at 1880/1798 cm(-1)), assigned to two unoxidized framework Co2+ with an adjacent oxygen vacancy. A labile Co2+(NO) adduct adsorbing at 1845 cm(-1) could be assigned to Co2+ ions on small extraframework clusters. CO adsorption confirmed the presence of defective Co2+ ions with strong Lewis character that could not be oxidized in the present conditions. Upon reduction, highly dispersed Coo clusters were formed within the microporous channels. In the presence of CO, surface Co-0 atoms were extracted from the clusters to form volatile Coo(CO), (n = 2 or 4) complexes and bridged (Co-0)(n)(CO) species (bands at 2047 and 2008/1990 cm(-1), respectively). These results show that the insertion of heteroatoms in large pore AFI structure is strongly sensitive upon the synthetic conditions and metal loading, that have to be carefully tuned to get the desired catalytically active sites

FTIR spectroscopy of adsorbed molecules such as CO and NO was used to monitor the nature of cobalt centres in Co-containing aluminophosphates (AlPOs) and silicoaluminophosphates (SAPOs) with chabasite-like structures. The samples were synthesized by following a facile route during which the cobalt ions were directly inserted in the synthesis gels. These studies show that Co2+ ions are located in framework positions in CoAPO-34, where they substitute for some Al3+ ions, whilst in CoAPSO-34, where Si4+ ions replacing for some phosphorous lead to negative charges in the aluminophosphate framework, are contemporarily present both in framework and extra-framework positions. It is likely that, in the latter case, some cobalt ions act as counter ions compensating the negative structure