Selective catalytic reduction of NO to N2 with copper and cobalt exchanged ZSM-5 zeolites: the effect of calcium addition

Abstract

Zeólitas ZSM-5 contendo cobre ou cobalto, ou simultaneamente cobre e cálcio, ou cobalto e cálcio foram preparadas por troca-iônica e testadas como catalisadores na redução de NO a N 2 na presença de metano ou propano. . Nestes catalisadores a presença de cálcio não provocou diferenças significativas na atividade específica para a redução de NO ou para a oxidação do metano.ZSM-5 catalysts containing either Cu or Co cations individually or Cu/Ca or Co/Ca cation combinations were prepared by ion exchange. These materials were tested as catalysts for the reduction of NO to N 2 in the presence of propane or methane. Cu 2+ and [Cu-O-Cu] 2+ species were identified in ion exchangeable sites in the copper-containing catalysts. The amount of the latter cation increased with increasing copper content and in the presence of Ca 2+ and was the most active in the reduction of NO. However, at temperatures higher than 400 ºC its activity decreased markedly. For cobalt-exchanged zeolites, Co 2+ in charge-compensation sites or Co 3+ in extra-framework precipitates were present in the catalysts. It was verified that the amount of Co 3+ diminished with the presence of Ca 2+. For the catalysts prepared in this study no significant differences in specific activity for the reduction of NO or for methane oxidation were observed in the presence of calcium.

Reactive adsorption of hydrogen sulfide by promoted sorbents Cu‐ZnO/SiO2: active sites by experiment and simulation

“…In the promoted sorbent Cu 0.10 Zn 0.90 O/SiO 2 , the intensity of this absorption band is higher than that in the sorbent Cu 0.01 Zn 0.99 O/SiO 2 . The similar absorption band was reported in the UV–vis DRS spectra of the Cu‐containing zeolites at 600–850 nm . This absorption band was attributed to the Cu 2+ cations in octahedral coordination environment.…”

Synthesis and functionalization of SSZ-13 as an NH3-SCR catalyst

“…The first band, at wavelengths around 270 nm, is assigned to oxygento-metal charge transfer related to Cu(I) or Cu(II) species stabilized in the zeolite framework. [30][31][32] The origin of the broad band at wavelengths above 550 nm has been interpreted differently in the open literature. [32][33][34][35] On the one hand, Bennici et al 33 suggested that the position of the absorption maximum of this band is dependent on the nuclearity of CuO x clusters, i.e.…”

“…[30][31][32] The origin of the broad band at wavelengths above 550 nm has been interpreted differently in the open literature. [32][33][34][35] On the one hand, Bennici et al 33 suggested that the position of the absorption maximum of this band is dependent on the nuclearity of CuO x clusters, i.e. the lower the wavelength of the absorption, the larger the clusters and vice versa.…”

Cu and Co exchanged ZSM-5 zeolites: activity towards no reduction and hydrocarbon oxidation

“…For the |Na|[Si 12 Al]-MFI and |Na|[Si 25 Al]-MFI zeolites an additional signal at 0 ppm is observed, which increases corresponding to peak 2 (A2) does not correspond to the total hydrogen consumption (H 2 /Me total). This difference in the H 2 consumption might be attributed to the presence of CuO, whose content in each catalyst (show in Table 5 CuO can be formed during calcination from hydroxylated species generated during the ion exchange 19 , such as Cu n+ (OH) n , Cu (n+m)+ (OH) m (O-CO-CH 3 ) n or Cu n+ (OH) m (n-m)+ , resulting in a pH decrease from 5.5 to 4.9.…”