Temperature-programmed calcination of basic chromium(III) acetate impregnated onto a high surface area silica support and chromium(III) acetylacetonate dry-blended with silica has been studied by quadrupole mass spectrometry and infrared spectroscopy. In both cases the same reactive intermediate has been identified.

Atomic force microscopy has been used to follow the breakup of catalyst particles and the growth of polymer during ethylene polymerization over the Phillips CrO x /silica calalyst.

The ethylene polymerization activities of low-temperature plasma-activated CrO x /SiO2 catalysts prepared from two different types of precursor are compared. Chromium(III) acetate wet impregnated onto high surface area silica is found to yield polyethylene, while chromium(III) acetylacetonate dry blended with silica does not. This is despite both precursors exhibiting good catalytic activity following conventional thermal activation.

Chromium(III) acetate impregnated onto a high surface area silica support and chromium(III) acetylacetonate dry-blended with silica were calcined at 1053 K and cooled. CO reduction of the resultant CrO x /silica materials was monitored by quadrupole mass spectrometry and found to proceed via a Langmuir−Hinshelwood mechanism. Activation energies for CrO x /silica catalyst reduction by CO have been determined from the corresponding Arrhenius plots; these suggest the existence of two types of reactive chromium sites.