Process control in the presence of chromium based catalysts

A continuous process for the polymerization of one or more alpha-olefins in the gas phase in the presence of a chromium based catalyst, under polymerization conditions including the reaction temperature, the pressure, and the target oxygen to alpha-olefin molar ratio operating point required for desired resin properties, comprising the following steps:

• (i) establishing limits on (a) the amount of catalyst and (b) the oxygen to alpha-olefin molar ratio;
• (ii) establishing a desired resin production rate in pounds per hour;
• (iii) determining the actual production rate as the polymerization progresses;
• (iv) determining the amount of catalyst required (a) to bring the actual production rate into line with the desired production rate and (b) to bring the oxygen to alpha-olefin molar ratio to the target oxygen to alpha-olefin molar ratio operating point;
• (v) determining the oxygen to alpha-olefin molar ratio required to bring the actual production rate into line with the desired production rate;
• (vi) determining the amount of oxygen required for the oxygen to alpha-olefin molar ratio;
• (vii) introducing catalyst, alpha-olefin, and oxygen into a reactor in the amounts necessary to satisfy the preceding steps;
• and
• (viii) adjusting the target oxygen to alpha-olefin molar ratio operating point as indicated by analysis of the polymer produced for the desired resin properties.