Chromium Catalyst Activation via Oxygen-Enriched Fluidization
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Solution Overview
Problem
The activation of large quantities of supported chromium catalysts in commercial practice results in relatively low conversion to Cr(VI), which is undesirable.
Innovation Solution
Contacting a supported chromium catalyst with a gas stream comprising 25 to 60 vol % oxygen at a peak activation temperature of 550° C. to 900° C. to produce an activated chromium catalyst, with linear and oxygen linear velocities within specific ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional air streams are used for catalyst activation, then equipment and pressure limitations are maintained, but Cr(VI) conversion remains relatively low
Solution Approach 1:
The patent changes the oxygen concentration parameter in the fluidization gas from conventional air levels (21% O2) to enriched levels (25-60 vol% O2). This parameter change enables achieving high Cr(VI) conversion (comparable to conventional air streams) while operating at lower gas velocities that respect equipment and pressure limitations, thereby resolving the contradiction between manufacturing precision and productivity
Solution Approach 2:
The patent employs oxygen-enriched fluidization gas (25-60 vol% O2) as a strong oxidizing atmosphere to accelerate the oxidation of chromium to Cr(VI) state. This accelerated oxidation enables high conversion efficiency without requiring excessive gas flow rates, thus maintaining equipment constraints while improving activation efficiency
2Manufacturing precision
If gas stream velocity is increased to improve Cr(VI) conversion, then oxidation efficiency improves, but equipment and pressure limitations are exceeded
Solution Approach 1:
The patent changes the oxygen concentration parameter in the fluidization gas from conventional air levels (21% O2) to enriched levels (25-60 vol% O2). This parameter change enables achieving high Cr(VI) conversion (comparable to conventional air streams) while operating at lower gas velocities that respect equipment and pressure limitations, thereby resolving the contradiction between manufacturing precision and productivity
Solution Approach 2:
The oxygen-enriched gas acts as an intermediary medium that provides sufficient oxidizing capacity at lower flow rates. The enriched oxygen concentration compensates for the reduced gas velocity, maintaining effective oxidation while reducing mechanical stress and pressure on the activation equipment
3Manufacturing precision
If activation time is extended to improve Cr(VI) conversion, then oxidation completeness improves, but overall cycle time increases
Solution Approach 1:
The patent employs oxygen-enriched fluidization gas (25-60 vol% O2) as a strong oxidizing atmosphere to accelerate the oxidation of chromium to Cr(VI) state. This accelerated oxidation enables high conversion efficiency without requiring excessive gas flow rates, thus maintaining equipment constraints while improving activation efficiency
Solution Approach 2:
The patent maintains continuous exposure of the chromium catalyst to the oxygen-enriched fluidization gas at optimized velocities (0.18-0.4 ft/sec gas linear velocity, 0.05-0.15 ft/sec oxygen linear velocity). This continuous oxidation action at enhanced oxygen concentration achieves complete Cr(VI) conversion within the standard cycle time, preventing time loss
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process achieves higher Cr(VI) conversions comparable to conventional air streams, even under mechanical equipment and pressure limitations, without increasing overall cycle times or peak activation temperatures.
Implementation Method 1
activation of supported chromium catalysts often results in relatively low conversion to Cr(VI), which is undesirable
Implementation Method 2
contacting a supported chromium catalyst with a gas stream comprising from 25 to 60 vol % oxygen at a peak activation temperature of from 550° C. to 900° C.
Data Source
AI summary
Processes for producing an activated chromium catalyst are disclosed, and these processes comprise contacting a supported chromium catalyst with a gas stream containing from 25-60 vol % oxygen at a peak activation temperature of 550-900° C. to produce the activated chromium catalyst. The linear velocity of the gas stream is 0.18-0.4 ft/sec, and the oxygen linear velocity of the gas stream is 0.05-0.15 ft/sec. The resultant activated chromium catalyst and an optional co-catalyst can be contacted with an olefin monomer and an optional olefin comonomer in a polymerization reactor system under polymerization conditions to produce an olefin polymer.