Chromium Oxide Catalyst Activation Fluidization Velocity Control
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Solution Overview
Problem
The challenge lies in achieving a balance of desirable properties in ethylene (co-) polymers, such as environmental stress crack resistance, creep behavior, and high catalyst activity, while avoiding catalyst fragmentation issues during gas phase polymerization using supported chromium oxide based catalysts, particularly in fluidized bed reactors.
Innovation Solution
A process involving a two-stage fluidization velocity control in a fluidized bed activation reactor, where the initial fluidization velocity is maintained below 6.5 cm/sec until the reactor reaches at least 200°C, then increased by at least 1 cm/sec, and subsequent thermal treatments are conducted under inert and oxidizing atmospheres to prevent catalyst fragmentation and enhance polymer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fluidization velocity is increased to improve catalyst activity and productivity, then the production rate increases, but catalyst fragmentation occurs
Solution Approach 1:
The patent applies preliminary action by conducting a pre-activation treatment at low fluidization velocity (below 6.5 cm/sec) before the actual polymerization process. This preliminary step stabilizes the catalyst structure and prevents fragmentation before high-velocity operation begins, allowing subsequent high productivity without catalyst breakdown
Solution Approach 2:
The patent employs dynamics by implementing a two-stage fluidization velocity strategy: initially maintaining low velocity (below 6.5 cm/sec) during activation, then increasing to higher velocity (above 6.5 cm/sec) during polymerization. This dynamic adjustment optimizes both catalyst stability and productivity at different process stages
2Productivity
If the thermal treatment temperature is increased to activate the catalyst, then catalyst activity improves, but catalyst fragmentation increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thermal treatment temperature profile - heating to activate the catalyst while maintaining fluidization velocity below 6.5 cm/sec to prevent fragmentation. The temperature is increased sufficiently for activation but the low-velocity condition prevents mechanical stress-induced fragmentation
3Productivity
If the fluidization velocity is maintained high throughout the process, then productivity is maximized, but catalyst stability decreases
Solution Approach 1:
The patent applies preliminary action by stabilizing the catalyst at low fluidization velocity during the activation phase before introducing high velocity for production. This ensures catalyst structural integrity is established before high-productivity operation begins
Solution Approach 2:
The patent employs dynamics by switching from low to high fluidization velocity at the appropriate process stage. The velocity is maintained below 6.5 cm/sec during activation for stability, then increased above 6.5 cm/sec during polymerization for maximum productivity, optimizing both stability and productivity at different times
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 approach successfully produces ethylene (co-) polymers with desired properties, including high environmental stress crack resistance and creep behavior, while maintaining high catalyst activity and preventing fragmentation, suitable for various applications like pipe extrusion and blow molding.
Implementation Method 1
a catalyst bed being fluidised by a fluidisation gas
Implementation Method 2
treatment at temperatures above 500° C.
Implementation Method 3
thermally treating the catalyst precursor being carried out for at least part of the time in an oxidizing atmosphere
Data Source
AI summary
Process for the activation of a supported chromium oxide based catalyst in a fluidized bed activation reactor which has a catalyst bed being fluidized by a fluidization gas. The activation includes treatment at temperatures above 500° C., in which in an initial stage, where there is an initial temperature increase, the fluidization velocity (Vf1) of the fluidization gas is maintained below 6.5 centimeters per second (cm/sec) until the temperature inside the activation reactor reaches at least 200° C., and the fluidization gas is then brought to a value (Vf2) which is at least 1 cm/sec higher than Vf1.