Adsorption and reaction of hydrogen cyanide on chromia and copper oxide-chromia surfaces.

Abstract

Studies have been made of the adsorption and interaction of hydrocyanic acid with chromium oxide and copper oxide-chromium oxide mixtures. The adsorption and desorption was followed using gravimetry, gas chromatography, mass spectrometry and infra-red spectroscopy. The adsorption of HON on to chromia at 298K was found to be dependent upon the surface pretreatment. It was found that almost twice as much HCN could be adsorbed onto an oxidised surface compared to a reduced surface. All the surface treatments were found to bring about the decomposition of HCN, with the release of products to the gas phase at 298K. Gas chromatographic and mass spectrometric analyses showed that the HCN was oxidised to CO2, N2 and H2O; with most of the CO2 being retained on the surface. Desorption produced mainly CO2 with some N2 and HCN. Identical studies carried out using infra-red spectroscopy showed only absorption bands that could be assigned to a reacted form of HCN, Several different types of surface species were identified, and their transformation followed at elevated temperatures. Possible reaction mechanisms for the observed behaviour are discussed. Similar studies were carried out following the addition of small amounts of cupric oxide to the chromia. In addition to the formation of N2, CO2 and H2O, C2N2 was also liberated. The amount of C2N2 found to be dependent on the Cu2+ concentration. Infra-red absorption bands were observed due to copper-cyanide species. Mechanisms for their formation and transformation at elevated temperatures are discussed.

Date of Award	1981
Original language	English
Awarding Institution	University of Bath