Chromia/silica–titania cogel catalysts for ethene polymerisation. Infrared study of nitric oxide adsorption

Abstract

Infrared spectroscopy has been used to study the adsorption of NO on a chromia/silica–titania cogel (4.2% Ti) reduced in carbon monoxide. A mononitrosyl surface complex gave a band at 1807 cm^–1. Four types of dinitrosyl complexes have been identified by pairs of infrared bands at 1856/1742, 1868/1736, 1875/1755 and 1886/1766 cm^–1 and are ascribed to Cr^II sites of differing structural type. A Cr^III site also gave infrared bands at 1875/1755 cm^–1 due to a dinitrosyl complex. The effects of reduction conditions, chromia content, water, oxygen and ethene on NO adsorption have been investigated.