Infrared Spectroscopic Study of NO and NH3 Adsorption on Alumina-Supported Nickel Oxide Catalysts

Abstract

The surface changes of alumina due to supported nickel oxide species (samples are prepared by step-wise pore volume impregnation with formate solutions) are studied in the high frequency region (OH stretches) by the method of in situ FTIR spectroscopy. A hypothesis is made that the nickel species deposite predominatingly on the surface neutral OH groups via hydrogen bonds. The deposition of the nickel oxide species on the coordinatively unsaturated Al 3+ ions (obtained as result of the dehydroxylation) is also discussed. The metal concentration increase does not lead to the change in the alumina surface, while the calcination temperature appears to change it. The adsorption and desorption of ammonia species on the nickel-supported samples reveal that the nickel concentration increase results in the increase of the number of the nickel species and in the intensity increase of the bands corresponding to ammonia more weakly bonded to the nickel species. The analysis of the spectra reveals that the sample containing 1.7% NiO and heated at 870 K displays the highest activity with respect to NO oxydation as compared to other samples studied.

Hydrogen by glycerol steam reforming on a nickel–alumina catalyst: Deactivation processes and regeneration

“…Bands at 1620 and 1470 cm À1 were previously assigned to Al 2 O 3 support [36]. Nevertheless, several species formed between deposited metal ions and support phase were reported above 1700 cm À1 [34].…”

“…At high frequencies (4000-3000 cm À1 ), an intense band centered at 3500 cm À1 , which decreased for Ni/Al 2 O 3 , and another weak band at 3780 cm À1 , were observed. The broad band at 3500 cm À1 has been assigned to interaction between hydroxyls groups and/or chemisorbed water on the support through hydrogen bonding [34]; the intensity reduction of that band was related to a decrease in the hydration degree of support surface [35]. At low frequencies (2000-1000 cm À1 ), a medium band at 1630 cm À1 and a weak one at 1440 cm À1 appeared on Al 2 O 3 with and without Ni.…”

Hydrogen production by glycerol steam-reforming over nickel and nickel-cobalt impregnated on alumina

“…A weak band at 3780 cm À1 was also showed, being weakly visible in catalyst with lower Co loading. The broad band at 3500 cm À1 correspond to interactions through hydrogen bonding between hydroxyls groups and chemisorbed water groups on g-Al 2 O 3 surface [24]. The 3780 cm À1 band was mainly attributed to acidic, neutral, and basic OH groups [25].…”

Catalizadores de cobre soportado parareducción selectiva de glicerol

“…La Figura 3 presenta espectros FTIR de Cu/Al 2 O 3 , que exhiben en la región de alta frecuencia una banda intensa centrada en 3500 cm -1 , debida a interacciones de OH del soporte y/o agua quimisorbida al soporte [15], y una banda débil a 3780 cm -1 , atribuida a grupos OH ácidos, neutros y básicos [16]; la banda a 1300 cm -1 se asigna a especies Cu. Pt/WO 3 /ZrO 2 presenta la banda centrada a 3400 cm -1 , asignada a grupos OH con enlaces hidrógeno; la calcinación provoca pérdida de OH generando una disminución de la intensidad de dicha banda [17].…”