NO decomposition in non-reducing atmospheres. Technical progress report, June--August 1996

In the last quarterly technical progress report, it was shown that adsorption of Co and ethylene onto 0.2 wt% Co(II) ion exchanged erionite, with Si/Al molar ratio of 3.6, after dehydration at 350 C significantly altered the optical spectrum of the zeolite. It was also found that the paramagnetic moment of Co(II) in erionite (8 wt% Co(II)) dehydrated at 525 C was higher than that obtained after dehydration to only 350 C. Therefore, adsorption studies have been carried out with the Co(II) erionite samples after dehydration at the higher temperature of 525 C. It was found that adsorption of CO and ethylene onto 0.2 to 6--8 wt% Co(II) erionite zeolites significantly altered the optical spectra of the samples. The band at approximately 24,500 cm{sup {minus}1} that is characteristic of bare Co(II) cations in six-ring window in zeolites disappeared upon adsorption of CO and ethylene, indicating that the Co(II) ions were accessible and underwent complexation by these reductant molecules. At the same time, the intensities of the spectra arising from the complexed Co(II) cations were more intense than those of the dehydration Co(II) centers. Therefore, there is no evidence that Co(II) was reduced by these weak ligands. The siting and accessibility of the Co(II) cations is expected to influence the activity of zeolite catalysts for the selective catalytic reduction of NO by different reductants