Adsorption and surface reactions of pyridine on pure and doped ceria catalysts as studied by infrared spectroscopy

Pyridine sorption from aqueous solution by rice husk ash (RHA) and granular activated carbon (GAC): Parametric, kinetic, equilibrium and thermodynamic aspects

“…The peak around 1400 cm −1 is the characteristic band of Py bonded to Lewis site. The peaks in the range of 1600-1650 cm −1 are due to the bond of pyridine to the Brönsted site [25,26]. These peaks are normally attributed to adsorbed bound water onto the sorbent surface.…”

Silica–zirconia mixed oxide samples by an hybrid materials based innovative preparation procedure: Influence of preparation procedure and composition on active sites

“…In the broad band between 1680-1610 cm À1 (Fig. 5(a)) both the pyridine interacting with Lewis acidic sites (1640-1610 cm À1 ) [27,[52][53] and with Brønsted acidic sites (1680-1640 cm À1 ) can be observed. The presence of Brønsted acidic sites is confirmed by the signals at 1549-1543 cm À1 .…”

Lanthanum oxides for the selective synthesis of phytosterol esters: Correlation between catalytic and acid–base properties

“…It is well known that the position and the multiplicity of the ν 8a ring vibration of chemisorbed pyridine (1579 cm −1 in the liquid phase) is related to the strength and the number of the different types of Lewis acid sites [30]. According to various studies [31][32][33][34][35], the occurrence of the ν 8a mode at two different frequency values (1618 and 1593 cm −1 ) indicates that the Lewis acid sites belong to two different populations with different acidity strengths. As already reported for other oxides [36], the spectra of pyridine chemisorbed on the lanthanum oxide can be interpreted by considering that two types of species are formed, corresponding to La 3+ in different structural environments (e.g., defects, corners), characterized by the ν 8a bands at 1618 and 1593 cm −1 .…”