Ethylene Trimerization Catalyst Solvent Selection
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Solution Overview
Problem
Existing catalyst systems for ethylene oligomerization struggle with high benzene content in hexene products and require pre-distillation of ethylbenzene solvents, which complicates the process and increases costs.
Innovation Solution
A catalyst composition comprising a pyrrole compound, a chromium compound, an organoaluminum compound, and an aromatic hydrocarbon solvent comprising xylenes or C9 substituted benzenes, which simplifies the process by reducing benzene content and eliminating the need for pre-distillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ethylbenzene solvent is used in the catalyst system, then high catalytic activity is achieved, but high benzene content in the hexene product and complex pre-distillation process occur
Solution Approach 1:
The patent changes the solvent parameter from ethylbenzene to xylenes or C9 substituted benzenes. This parameter change maintains the aromatic hydrocarbon solvent category (preserving catalytic activity) while altering the specific chemical composition to reduce benzene content in products and eliminate the need for pre-distillation, thus resolving the contradiction between productivity and process complexity
2Productivity
If ethylbenzene solvent is used in the catalyst system, then high catalytic activity is achieved, but high benzene content in the hexene product occurs
Solution Approach 1:
The patent changes the solvent composition parameter from ethylbenzene to xylenes or C9 substituted benzenes. This substitution maintains the aromatic hydrocarbon properties necessary for high catalytic activity while inherently reducing benzene content in the hexene product stream, as xylenes and C9 substituted benzenes have different degradation pathways that produce less benzene
Solution Approach 2:
The patent converts the potential harm of using aromatic solvents (which can produce benzene contaminants) into a benefit by selecting specific aromatic solvents (xylenes or C9 substituted benzenes) that maintain the necessary catalytic activity while producing minimal benzene content, thus turning a harmful effect into a beneficial outcome
3Object-generated harmful factors
If pre-distillation of ethylbenzene solvent is performed, then benzene content is reduced, but process complexity and costs increase
Solution Approach 1:
The patent applies preliminary action by pre-selecting solvents with inherently low benzene-forming characteristics (xylenes or C9 substituted benzenes) before the oligomerization process begins. This preliminary selection eliminates the need for subsequent pre-distillation steps, as the solvent choice itself prevents high benzene content formation, thereby reducing process complexity while maintaining low benzene content in products
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
The use of xylenes or C9 substituted benzenes as solvents in the catalyst composition maintains high 1-hexene product purity and productivity while minimizing polymer byproducts and reducing benzene content in the hexene product stream.
Implementation Method 1
contacting ethylene, an organic reaction medium, optionally hydrogen, and any of the catalyst compositions disclosed herein in an oligomerization reactor, forming an oligomer product in the oligomerization reactor
Data Source
AI summary
Catalyst compositions containing a pyrrole compound, a chromium compound, an organoaluminum compound, and an aromatic hydrocarbon solvent comprising xylenes or C9 substituted benzenes are disclosed. Related ethylene oligomerization processes utilizing the catalyst compositions to produce oligomer products containing 1-hexene also are described.