Infrared spectroscopy above atmospheric pressure: support effects on the adsorption of dinitrogen on rhodium

Abstract

High-pressure infrared spectroscopy has been used to study the interaction of N2 with supported Rh films as a function of temperature and pressure. Adsorption equilibrium constants for N2 on Rh/X (X = Ti02, A1203, SO2) at 298 K were 0.376, 0.206, and 0.193 atm-I, respectively. The heat of adsorption for N2/Rh/Ti02 extrapolated to zero coverage was -10.2 kcal/mol.A sample film of Rh/Ti02 pretreated so as to approach SMSI conditions adsorbed N2 more tenaciously, with an adsorption equilibrium constant at 298 K of 0.541 atm-I. This work demonstrates the utility of high-pressure infrared measurements in obtaining useful surface thermodynamic data.

Anomalous valence changes and specific dinitrogen adsorption features of copper ion exchanged in ZSM-5 zeolite prepared from an aqueous solution of [Cu(NH3)2]+

“…Even for the Rh/TiO 2 -N 2 system, where Rh metal is well-known as one of the effective N 2 -activation catalysts, the adsorption heat is only 50 kJ mol À1 . [61][62][63] The large adsorption heats observed in the present system are comparable to the values observed for the copper ion-exchanged samples obtained by employing a solution involving acetate ions as counter ions in solution. 64 Such large heat values decrease with increasing amounts of adsorbed N 2 and approach the value of 35 kJ mol À1 after the establishment of monolayer coverage.…”

From atoms to crystallites: adsorption on oxide-supported metal particles

“…In a study of an oxidized Rh/alumina catalyst, for instance, a band at D2125 cm~1 has been attributed to a Rh2`CO species. 80 To clear up the origin of the signal at 2117 cm~1 in the present case, the following questions have to be answered :…”

Ab InitioStudy of the Interaction of Rhodium with Dinitrogen and Carbon Monoxide

“…There have been numerous experimental studies, primarily utilizing infrared spectroscopy, of the interaction of CO and N 2 − with supported Rh. A limited number of theoretical investigations at various levels of theory on CO/Rh species have also been reported, − but to our knowledge, N 2 /Rh species have not yet been studied by computational procedures.…”