Colorimetric oxygen detectors

Claim 1

The method of claim 1 in which said metal is chromium and said compound of said metal is at least one selected from the group consisting of halides, sulfates, nitrates, oxides, oxyhalides, oxysulphates, phosphates, carbonyls and bis-cyclopentadienyls.

Claim 4

A method for determining the presence of oxygen in an olefin-containing stream in the absence of substantial polymerization of the olefin, said oxygen being present in said stream in the form of molecular oxygen, SO2, N2O and NO2, which comprises contacting said stream at ambient temperatures with a colorimetric oxygen detector composition comprising a supported metal oxide which undergoes a color change upon contact with said olefin-containing stream, said color change being quantitatively related to the quantity of oxygen present in said stream, said colorimetric oxygen detector composition having been prepared by: a. impregnating a particulate silica-containing support with a solution comprising a compound of a metal selected from the group consisting of chromium, molybdenum, tungsten, niobium, and tantalum in an amount sufficient to deposit 0.01 to about 10 weight percent of said metal on said support; b. calcining the impregnated support by heating in the presence of air to convert said compound to an oxide of said metal; c. reducing the metal oxide obtained in (b) by contacting with carbon monoxide, at least a portion of said metal being in a lower valence state so that said detector undergoes a color change upon contact with oxygen or said oxygen-containing compound; and d. contacting the carbon monoxide reduced metal oxide formed in step (c) with a gas selected from the group consisting of flue gas, steam and nitrogen to inactivate said metal oxide for the polymerization of olefins and produce said colorimetric oxygen detector composition.