Synthesis, characterization, and use of nanocast LaMnO3 perovskites in the catalytic production of imine by the gas-phase oxidative coupling of benzyl alcohol to aniline

We report here a green methodology for the synthesis of imine from a gas-phase oxidative coupling of benzyl alcohol to aniline in a continuous-flow system. These reactions were performed using LaMNO3 perovskites as heterogeneous catalysts. The catalytic performance of these materials was 98% and remained stable for 8 h of reaction. The prepared catalysts were successfully regenerated and reused in five successive catalytic cycles. No organic solvents were used in this process, which represents an important advantage in terms of the environment, simplicity, and safety. Moreover, this approach reduces the need for subsequent physicochemical extraction and purification steps

Structural investigation of cobalt-doped silica derived from sol-gel synthesis

This work investigates the structural properties of cobalt doped silica samples prepared by sol-gel synthesis. Air calcination led to the formation of Co3O4 particles as evidenced by XRD and FTIR tests, although these features were no longer apparent for hydrogen-reduced samples. This behavior suggests the formation of metallic Co and CoO in the reduced samples. The variation of the cobalt content embedded in the silica matrix resulted in a change in texture of the prepared materials from microporous to mesoporous. This was attributed to the agglomeration of particles as observed in TEM micrographs, which led to larger particles and pores. The latter was associated with the formation of hysteresis loop in the nitrogen adsorption isotherms as a function of the [Co/(Si + Co)] molar ratio. This effect was more remarkable for reduced samples, leading to a further broadening of the hysteresis loop that stemmed from the reduction or loss of oxygen from cobalt oxide particles

Magnesium-based bioactive composites processed at room temperature

Hydroxyapatite and bioactive glass particles were added to pure magnesium and an AZ91 magnesium alloy and then consolidated into disc-shaped samples at room temperature using high-pressure torsion (HPT). The bioactive particles appeared well-dispersed in the metal matrix after multiple turns of HPT. Full consolidation was attained using pure magnesium, but the center of the AZ91 disc failed to fully consolidate even after 50 turns. The magnesium-hydroxyapatite composite displayed an ultimate tensile strength above 150 MPa, high cell viability, and a decreasing rate of corrosion during immersion in Hank’s solution. The composites produced with bioactive glass particles exhibited the formation of calcium phosphate after 2 h of immersion in Hank’s solution and there was rapid corrosion in these materials

Broadband transmission spectroscopy of HD 209458b with ESPRESSO: Evidence for Na, TiO, or both

Context. The detection and characterization of exoplanet atmospheres is currently one of the main drivers pushing the development of new observing facilities. In this context, high-resolution spectrographs are proving their potential and showing that high-resolution spectroscopy will be paramount in this field. Aims. We aim to make use of ESPRESSO high-resolution spectra, which cover two transits of HD 209458b, to probe the broadband transmission optical spectrum of the planet. Methods. We applied the chromatic Rossiter-McLaughin method to derive the transmission spectrum of HD 209458b. We compared the results with previous HST observations and with synthetic spectra. Results. We recover a transmission spectrum of HD 209458b similar to the one obtained with HST data. The models suggest that the observed signal can be explained by only Na, only TiO, or both Na and TiO, even though none is fully capable of explaining our observed transmission spectrum. Extra absorbers may be needed to explain the full dataset, though modeling approximations and observational errors can also be responsible for the observed mismatch. Conclusions. Using the chromatic Rossiter-McLaughlin technique, ESPRESSO is able to provide broadband transmission spectra of exoplanets from the ground, in conjunction with space-based facilities, opening good perspectives for similar studies of other planets.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737