FT-IR study of the adsorption and transformation of formaldehyde on oxide surfaces

TLDR: The adsorption of formaldehyde on different oxides (silica, pure and fluorided alumina, magnesia, titania, thoria, zirconia, and iron oxide) has been studied by FT-IR spectroscopy in the temperature range 170-570 K as mentioned in this paper.

Abstract: The adsorption of formaldehyde on different oxides (silica, pure and fluorided alumina, magnesia, titania, thoria, zirconia, and iron oxide) has been studied by FT-IR spectroscopy in the temperature range 170-570 K. The following adsorbed species have been identified and characterized spectroscopically: (i) physisorbed HCHO, (ii) coordinated HCHO, (iii) dioxymethylene, (iv) polyoxymethylene, (v) formate ions, and (vi) methoxy groups. On silica at 170 K formaldehyde physisorbs on surface OH groups and, by warming, polymerizes producing linear polyoxymethylene. On ionic oxides at about 250 K dioxymethylene is always observed, generally together with variable amounts of the linear polymer that has been isolated on magnesia at 170 K. Heating up to or above room temperature results in the disproportionation of dioxymethylene into formate and methoxide groups, probably via a Cannizzaro-type mechanism. Such a route probably parallels an oxidative route, involving direct oxidation of dioxymethylene into formates, as observed on iron oxide.