Chromium Catalyst for Ethylene Trimerization
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Solution Overview
Problem
Current catalysts for ethylene trimerization, such as Cr-based catalysts, face challenges in achieving high catalytic activity and selectivity for 1-hexene production, with existing compositions either having low activity or selectivity, and issues with by-product polyethylene sticking to apparatus surfaces.
Innovation Solution
A catalyst system comprising a P- and N-containing compound, electron donor, Cr compound, carrier (SiO2), and accelerator, with specific molar ratios and components like chromium isooctoate, 1,4-dichlorobenzene, and trimethyl aluminium, facilitating ethylene trimerization and preventing polyethylene sticking through coordination and β-H elimination reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Cr-based catalyst compositions are used for ethylene trimerization, then 1-hexene selectivity can be improved, but catalytic activity remains low
Solution Approach 1:
The patent employs a composite catalyst system combining Cr compound with P- and N-containing compound, electron donor, and accelerator in specific molar ratios. This composite approach integrates multiple functional components to simultaneously achieve high 1-hexene selectivity (97-99%) and high catalytic activity (1.5-5.0 g oligomer/mol Cr·h), resolving the contradiction between selectivity and productivity.
Solution Approach 2:
The patent optimizes critical parameters including molar ratios of catalyst components (a):(b):(c):(d):(e) = 1-80:1-70:1:1-8:100-4000, temperature (20-150°C), and pressure (0.5-10.0 MPa). These parameter adjustments enable the catalyst to achieve both high selectivity and high activity by fine-tuning the reaction conditions and catalyst composition.
2Productivity
If conventional Cr-based catalysts are used, then catalytic activity can be improved, but by-product polyethylene sticks to apparatus surfaces
Solution Approach 1:
The patent introduces carrier (d) as an intermediary component that mediates the interaction between the catalyst and reaction products. The carrier supports the catalyst components and modifies the reaction environment, enabling high catalytic activity while preventing polyethylene by-product from adhering to apparatus surfaces, thus resolving the sticking problem.
Solution Approach 2:
The patent converts the harmful effect of polyethylene by-product formation into a beneficial outcome by directing it to deposit on the carrier rather than on apparatus surfaces. The carrier acts as a sacrificial surface that captures polyethylene, preventing it from causing operational problems while maintaining high catalytic activity.
3Ease of manufacture
If catalyst composition is simplified, then ease of manufacture is improved, but catalytic activity and selectivity cannot meet current requirements
Solution Approach 1:
The patent achieves a balance between manufacturing simplicity and high performance by designing a catalyst system where each component serves multiple functions. The P- and N-containing compound not only enhances activity but also influences selectivity, while the electron donor and accelerator work together to optimize both ease of preparation and catalytic performance, meeting current industrial requirements.
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 catalyst system achieves high catalytic activity and selectivity for 1-hexene production while preventing polyethylene from sticking to apparatus surfaces, ensuring long reactor run periods and efficient ethylene trimerization.
Implementation Method 1
Cr compound can form three unoccupied orbitals under the effect of ligand and accelerator, which may facilitate the coordination of ethylene molecular
Implementation Method 2
then β-H elimination reaction occurs to obtain 1-hexene
Implementation Method 3
the by-product polyethylene is more easily formed on the carrier SiO2 so as to avoid sticking to the apparatus
Data Source
AI summary
A catalyst for synthesizing 1-hexene from ethylene trimerization and its application are provided. Said catalyst consists of (a) the compound containing P and N, (b) electron donor, (c) Cr compound, (d) carrier and (e) accelerator. The molar ratio of (a), (b), (c), (d) and (e) is 0.5-100 : 0.5-100 : 1 : 0.5-10 : 50-5000. The catalyst is prepared by mixing the components of (a)-(e) in an ethylene trimerization apparatus in situ and ethylene is introduced into the apparatus continuously. The prepared catalyst can be used to synthesize 1-hexene from ethylene trimerization in the inert solvents. The trimerization is performed at 30-150°C and 0.5-10.0 MPa for 0.1-4 hours. The catalyst has high catalytic activity and high 1-hexene selectivity. During the process of ethylene trimerization, by-product polyethylene does not stick to the apparatus.