"Nanotechnology and nanomaterials"

Natural and acid-modified nanobentonites as supports in palladium(II)-copper(II) catalysts for carbon monoxide oxidation with air oxygen
Rakitskaya T.L., Dzhyga G.M., Kiose T.A., Volkova V.Y.
Department of Inorganic Chemistry and Chemical Ecology, Odessa I.I. Mechnikov National University. Dvoryanskaya St., 2, Odessa-65082, Ukraine
E-mail: tlr@onu.edu.ua

, mg/m3

, мг/м3

τ, min

 Natural bentonites (N-Bents) from three Ukrainian deposits, i.e. Gorbskii, 
N-Bent(G), Kirovogradskii, N-Bent(K), and Dashukovskii, N-Bent(D), as well as their H-forms, 1H-Bent(G,K,D)-1, obtained by acid modification of natural bentonites with 1 M HNO3 for 1 h by reflux procedure were investigated as supports for palladium(II)-copper(II) complexes catalytically active in the reaction of carbon monoxide oxidation with air oxygen. The supports, , and catalysts based on them, Pd(II)-Cu(II)/, were characterized by XRD and SEM methods, FTIR spectroscopy, thermogravimetric (DTG-DTA) analysis, water vapour adsorption, and pH-metry. The montmorillonite phase with crystallite sizes in the range from 14 to 50 nm dominates in both natural and modified bentonites. Judging from the positions of d060 reflection, the Mont phase in the N-Bent(K) and 1H‑Bent(K)-1 samples differs from that in other natural and acid modified bentonites. The lowest pH values, namely, 4.35 and 4.01, are observed for the 1H‑Bent(G)-1 and 1H‑Bent(K)-1 samples, respectively. 
Catalyst samples of 10 g each were tested in the reaction of carbon monoxide oxidation at an initial CO concentration in a gas-air mixture (GAM) of 300 mg/m3, temperature of 20 С, and a GAM flow rate of 1 L/min. Figure shows the time dependences of a final CO concentration, , in the process of CO oxidation with air oxygen over Pd(II)‑Cu(II)/ nanocatalysts, where  are N-Bent(G) (1), 1H‑Bent(G)-1 (2), N-Bent(D) (3), 1H‑Bent(D)-1 (4), N-Bent(K) (5), and 1H‑Bent(K)-1 (6). Some properties of the supports and their effect on the activity of the nanocatalysts obtained from them have been analysed.