Investigation on NOx adsorption in [M′]-MAPO-5 (M=Si, Ti; M′=Ag, Cu) by density functional theory calculation

• Published in: Applied surface science Vol. 265; pp. 274 - 280
• Main Authors: Liu, Jiexiang, Zhang, Xiaoguang
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.01.2013; Elsevier
• Subjects: Adsorption; Aluminophosphate molecular sieve; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Copper; Density functional theory; Density functional theory (DFT); Density functional theory, local density approximation; Electron states; Exact sciences and technology; Mathematical models; Methods of electronic structure calculations; Nitrogen dioxide; Nitrogen oxide; Nitrous oxides; Physics; Silver; Solid surfaces and solid-solid interfaces; Surface chemistry; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Titanium; Nitrogen oxide; Silver; Adsorption; Aluminophosphate molecular sieve; Copper; Density functional theory (DFT); Transition elements; Density functional method; Silicon; Molecular sieves; Aluminophosphates
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2012.10.194

▸ [M′]-MAPO-5 (M=Si, Ti; M′=Ag, Cu) has good resistance capability to H2O and SO2. ▸ Adsorption strength follows the decreasing order of NO2>NO>N2O. ▸ [Cu]-MAPO-5 is more effective for the activation of NOx than [Ag]-MAPO-5. ▸ [M′]-MAPO-5 has a stronger adsorption for NO, NO2, SO2and O2 than [M′]-AlMOR. ▸ NBO results are in reasonable agreement with adsorption interaction strengths. NO, N2O and NO2 adsorption in [M′]-MAPO-5 (M=Si, Ti; M′=Ag, Cu) models of the modified aluminophosphate molecular sieves was investigated by density functional theory (DFT) method. The equilibrium structural parameters and adsorption energies were obtained and compared. The structural parameters of NO and NO2 in the adsorbed state had a distinct change than that of N2O compared to their free gas state. [M′]-MAPO-5 was more effective for the activation of NOx molecule compared to [M′]-AlMOR (M′=Ag, Cu) models of the modified mordenite in our previous studies. The adsorption energies data indicated that adsorption strength of NOx followed the decreasing order of NO2>NO>N2O. And adsorption complexes in η1-N mode were much stabler than that in η1-O mode, which was similar to that in [M′]-AlMOR. [Cu]-MAPO-5 had a much stronger adsorption for NOx than [Ag]-MAPO-5. And [M′]-SiMOR had a little stronger adsorption for NOx than [M′]-TiMOR. Furthermore, the resistance capabilities of [M′]-MAPO-5 to SO2, H2O and O2 were studied and analyzed. The interaction mechanism of NOx adsorption in [M′]-MAPO-5 was also discussed by natural bond orbital (NBO) analysis, which was in reasonable agreement with the adsorption interaction strengths.