Zeolite Cu-ZSM-5: material characteristics and NO decomposition

Zeolite ZSM-5 (SiO(2)/Al(2)O(3) ratio 53:1) ion exchanged with Cu(2+) to 0%, 74% and 160% was characterized by X-ray diffraction (XRD), Thermogravimetric analysis (TGA), infrared (IR) spectroscopy, Electron spectroscopy for chemical analysis (ESCA) and ammonia desorption. A more limited set of data was obtained for Cu-ZSM-5-33, ion exchanged with 0%, 104% and 210% Cu(2+) ions

Conversion and in situ FTIR studies of direct NO decomposition over Cu-ZSM5

Copper ion-exchanged zeolites ZSMS with SiO2:Al2O3 molar ratios 33 and 53 have been subjected to activity tests for direct decomposition of NO (2000 ppm, GHSV 560-5400 h(-1)). In situ infrared measurements were used to follow the reaction and surface and gas phase compositions. IR studies were also done in excess oxygen with rapid NO2 formation in the gas phase. A high level of overexchange of copper in the zeolite in combination with a low concentration of acid sites, concurrent with a high SiO2:Al2O3 ratio, enhances the conversion of NO. A vibrational band at 1631 cm(-1) is observed below the light-off temperature and interpreted as a bridged nitrate group bound to Cu2+-O-Cu2+ dimers. This band disappears above the light-off temperature but the intensity below this temperature correlates with the catalytic activity. We interpret that these bridge bound nitrate groups act as siteblockers on the active sites for NO conversion and that a tentative reaction intermediate, N2O3, also binds in a bridge configuration to the same Cu2+-O-Cu2+ dimers.A second nitrate group with unidentate coordination and vibrational bands at 1598/1575 cm(-1) probes isolated copper ions.A third infrared band at 2130 cm(-1) confirms previous observations of NO2+-ions bound to the zeolite. We conclude that these species are coordinated to deprotonated and negatively charged sites on the zeolite and that these sites for NO2+ adsorption are blocked by Cu2+ ion-exchange. The 2130 cm(-1) species appear to have no role in direct NO decomposition but the adsorption sites are crucial for the stability of the zeolite and intimately related to ion mobility in the lattice.Prolonged immersion of the zeolite in dilute solutions of copper ions improves the catalyst performance by copper hydroxylation leading to enhanced formation of the above dimers.A high SiO2:Al2O3 ratio leads to more stable catalysts, particularly in combination with a modest overexchange of copper ions. Excessive amounts of copper escalates the deactivation of the Cu-ZSM5 catalyst through the migration and sintering of cupric oxide crystallites.</p

Wet clutch transmission fluid for AWD differentials : influence of lubricant additives on friction characteristics

A study on the influence of base oils on friction properties was carried out. The effects of additive interactions must be considered but were hard to predict. This was most notable with EP additives that were hard to combine with other additives without compromising the anti-shudder properties of the clutch. The developed fluid showed that it is feasible to combine anti-shudder properties and hypoid gear lubrication abilities in one fluid. Good anti-shudder properties were realized despite high concentrations of EP additives. This is an abstract of a paper presented at the 15th International Colloquium Tribology-Automotive and Industrial Lubrication (Ostfildern, Germany 1/17-19/2006).</p

Catalyst preparation through ion-exchange of zeolite Cu-, Ni-, Pd-, CuNi- and CuPd-ZSM-5

Ion-exchanged zeolite ZSM-5 is the best known catalyst for direct NOx decomposition and a viable candidate for NOx reduction with methane. The preparation is crucial for the efficiency of the conversion and this paper describes the ion-exchange, with Cu2+, Ni2+ or Pd2+, and the dual exchange, with Cu2+/Ni2+ or Cu2+/Pd2+, under appropriate pH and ion concentrations for maximum dispersion.</p