Transformations of Formaldehyde Molecules in Cu−ZSM-5 Zeolites

Abstract

The activation of CdO bond in formaldehyde molecule was followed by IR spectroscopy. IR studies showed that the interaction of formaldehyde with Cu + weakens of the CdO bond and results in a red shift of the CdO IR band (∆ν ) 56 cm -1 ). The activation of the CdO bond is the result of π back-donation of d electrons of Cu + to π * antibonding orbitals of the molecule. Experiments on coadsorption of formaldehyde and CO on the same Cu* showed that formaldehyde acts as electron donor to the Cu + -CO system, resulting in stronger π back-donation to antibonding orbitals of CO. IR studies showed that formaldehyde molecules sorbed in zeolite Cu-ZSM-5 are oxidized to formate ions. Cu 2+ ions, which survived the self-reduction to Cu + during the pretreatment of zeolite under vacuum, were oxidant. Such Cu 2+ ions are reduced to Cu + during the reaction with formaldehyde molecules.

Pathways of Methane Transformation over Copper‐Exchanged Mordenite as Revealed by In Situ NMR and IR Spectroscopy

“…Group (4), together with the various C−H vibrations, shows the presence of the bands at 1696 and 1685 cm −1 , which are characteristic of carbonyl compounds having a C=O group. Taking the chemistry of the process into account, these bands may correspond to different forms of adsorbed formaldehyde, small amounts of which form from methanol or methoxy species during oxidation at low temperature . Formaldehyde is unstable at high temperature and decomposes rapidly, as visible in the IR spectra (Figure ).…”

Pathways of Methane Transformation over Copper‐Exchanged Mordenite as Revealed by In Situ NMR and IR Spectroscopy

“…Forschungsartikel 1685 cm À1 ,w hich are characteristic of carbonyl compounds having aC =Ogroup.T aking the chemistry of the process into account, these bands may correspond to different forms of adsorbed formaldehyde,s mall amounts of which form from methanol or methoxy species during oxidation at low temperature. [61,62] Formaldehyde is unstable at high temperature and decomposes rapidly,a sv isible in the IR spectra ( Figure 4). Thel ast group (5) shows the superposition of several bands due to adsorbed water and asymmetric vibrations of formate species.…”

New Air Cleaning Strategies for Reduced Commercial Building Ventilation Energy

“…Zeolites are highly porous aluminosilicates with strong affinity for certain gases and organic vapors, including formaldehyde (Qian et al 2001;Aguado et al 2004). Research has shown that formaldehyde adsorbs strongly to zeolites, where its oxidation can be catalyzed (Okachi and Onaka 2004;Kukulska-Zajac and Datka 2007;Gora-Marek and Datka 2008). Formaldehyde sorption and desorption studies (Matthews et al 1987) demonstrate that gypsum board has a substantial storage capacity for sorbed formaldehyde vapor that buffers sudden changes in formaldehyde concentration in the surrounding atmosphere but appears to cause only a minor, permanent loss mechanism for formaldehyde.…”