Photochemical reactions of titanium dioxide

Abstract

The extremely high degree to which titanium dioxide reflects light has led to its large scale use as a pigment in the paint and paper industries and as a delustering agent for artificial fibres in the textile industries. Although ideal in physical properties titanium dioxide has adverse chemical properties in such respects that its use is accompanied by the flaking of paints and the tendering of fabrics, actions largely induced on exposure to light. (1, 2, 3, 4, 5).

Among the various objects of this present work is the establishing of the common factors between oxygen and nitric oxide uptakes, and both oxygen-titanium dioxide and nitric oxide-titanium dioxide systems have been further investigated. In addition, processes occurring between titanium dioxide and ammonia also mixtures have examined.

The foregoing discussion has established the photochemical reactions of titanium dioxide to occur on the surface. Although the postulated nature of the "photo-activated" surface has successfully explained the observed reactions it still remains to be further established. Study of the adsorption of unsaturated hydrocarbons, in particular acetylene and ethylene, and other simple organic molecules such as formaldehyde and acetaldehyde might yield interesting results.

The problem of preventing photochemical properties in commercial titanium dioxide pigments still remains to be solved. It was not possible during the present work to determine whether they sponsored the same photo processes. If, however, they do, then it is obvious that the pigment must, in some way, b e prevented from having oxygen or hydroxyl deficiencies on the surface. It would be interesting to see if phosphine (PH₃) would displace water- in the same manner as ammonia and if it did, whether the subsequent uptake of oxygen would be photo or thermal.

Possible uses of titanium dioxide as a specific catalyst may arise from the proton donating and accepting properties resulting from the ammonia displacement of water, e.g. would it be possible to hydrogenate ethylene by illumination of hydrogen and ethylene? By working at elevated temperatures it might be possible to accomplish this thermally.