Search

We report the first experimental investigation of porous organic cages (POCs) for the demanding challenge of SO2 capture. Three structurally related N‐containing cage molecular materials were studied. An imine‐functionalized POC (CC3) showed modest and reversible SO2 capture, while a secondary‐amine POC (RCC3) exhibited high but irreversible SO2 capture. A tertiary amine POC (6FT‐RCC3) demonstrated very high SO2 capture (13.78 mmol g−1; 16.4 SO2 molecules per cage) combined with excellent reversibility for at least 50 adsorption–desorption cycles. The adsorption behavior was investigated by FTIR spectroscopy, 13C CP‐MAS NMR experiments, and computational calculations. [ABSTRACT FROM AUTHOR]

X-ray diffraction, 27Al MAS NMR, and FTIR spectra along with results of molecular dynamics simulations were used to characterise LaxEu1-xAlO3 perovskites for x = 0.3, 0.1. Experimental and simulation results show that local changes in the perovskite-like structure can be achieved as lanthanum ions substitute europium ones. The introduction of La3+ ions in the EuAlO3 parent causes an increase in the mobility of oxygen network. [ABSTRACT FROM AUTHOR]

A critical step in designing conservation strategies for earth architecture is the adequate identification of all mineral constituents into a given piece. Of particular importance is the accurate identification of amorphous components, which is normally achieved by well-proved and standardized procedures. However, a lot of difficulties often appear mainly by the severe restrictions imposed when samples involved with cultural heritage are concerned. This allows us to follow a methodology for identifying with accuracy allophane and other amorphous materials as components in micro-samples of archeological adobe earth bricks from Cholula, which is described here. These short-range-order components are relevant because of the properties that they give to the adobe earth bricks as structural material. A set of multi-spectroscopic analysis including both long-range (XRD) and short-range order techniques (FTIR and 29 Si and 27 Al MAS-NMR); as well as thermal analyses (TGA-DSC); combined with optical microscopy and electron microscopy (SEM and FE-SEM); allowed us to the identification of not only allophane but also other semi-crystalline and amorphous phases like opal-CT, diatoms and volcanic glass. [ABSTRACT FROM AUTHOR]

Abstract: Activated Mg–Al layered double hydroxides (LDHs) with varying Mg/Al molar ratios are tested as heterogeneous catalysts for the cyanoethylation of methanol and 2-propanol. The activation procedure is performed by calcination of the LDH precursors, followed by gas-phase rehydration on an H2O/N2 flow. In this case, rehydration is carried out at 80°C, instead of room temperature as usual. Increased temperature has a very significant effect on the reconstruction speed, shortening the process from ∼12 to 0.5h. Good conversions and yields to alkoxypropionitriles are obtained with thus activated LDHs. Correlations are established between basic strength, as determined by CDCl3 adsorption followed by FTIR, and catalytic activity. Depending on alcohol acidity, greatest conversions are obtained over catalysts with Mg/Al molar ratios of 2 or 3. Solids are further characterized by X-ray diffraction, thermal gravimetric analyses, and 27Al MAS NMR. [Copyright &y& Elsevier]