Infrared Spectroscopic Study of ClCN Adsorption on Clean and Triethylenediamine-Precovered γ-Al2O3

The effect of triethylenediamine (TEDA) (also named 1,4-diazabicyclo [2.2.2]octane, DABCO) on the adsorption of ClCN on a γ-Al2O3 absorbent has been investigated. Both Fourier transform infrared (FTIR) and theoretical studies indicate that no direct interaction between amine groups of TEDA and ClCN molecules takes place. Instead, we found that TEDA competes with ClCN for active surface sites on γ-Al2O3. In addition, the adsorption behavior of cyanogen chloride (ClCN) on a clean γ-Al2O3 surface has been studied. The sequence of the thermally activated processes of diffusion, adsorption, desorption, and decomposition of ClCN molecules on the clean γ-Al2O3 surface following icelike ClCN layer formation at lower temperature was observed. One of the decomposition products, Al−NCO, was assigned by using an Al−18OH labeled surface for reaction with ClCN. In addition, Al−CN and Al2−OCN species were also detected upon ClCN decomposition. Good correlation of the calculated vibrational frequencies for the adsorbed s...