Silica-Supported Chromium Oxide Catalyst for Higher Resin Bulk Density
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Solution Overview
Problem
Chromium-based ethylene polymerization catalysts in gas phase reactors struggle to produce polyethylene with high resin bulk density, leading to reduced reactor bed weight, fluidized bulk density, and production rates, along with issues in heat removal and conversion efficiency.
Innovation Solution
A silica-supported chromium oxide catalyst system with specific particle diameter, pore volume, and surface area characteristics, combined with chromium, titanium, and aluminium compounds, is used to enhance resin bulk density and productivity in fluidized bed gas phase reactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional chromium-based catalysts are used in gas phase reactors, then polymerization activity is maintained, but resin bulk density decreases leading to reduced reactor bed weight and production rate
Solution Approach 1:
The patent applies parameter changes by optimizing the silica support properties (particle diameter 2-10 μm, pore volume 0.5-2.0 ml/g, surface area 200-500 m²/g) and chromium loading (0.1-1.0 wt%) to achieve the desired resin bulk density range of 300-600 kg/m³ while maintaining high productivity
Solution Approach 2:
The patent uses a composite catalyst system consisting of chromium oxide dispersed on silica support, combining the catalytic activity of chromium with the structural properties of silica to control resin bulk density and improve reactor performance
2Reliability
If resin bulk density is reduced, then catalyst activity is maintained, but reactor bed weight and fluidized bulk density decrease causing operational issues
Solution Approach 1:
The patent optimizes the silica support pore volume (0.5-2.0 ml/g) and particle diameter (2-10 μm) to control resin bulk density within 300-600 kg/m³, ensuring adequate fluidized bulk density for stable reactor operation while maintaining catalyst activity
3Productivity
If superficial gas velocity is reduced to avoid resin carry over, then resin bulk density issues are mitigated, but heat removal capacity and production rate decrease
Solution Approach 1:
The patent increases resin bulk density to 300-600 kg/m³ through optimized catalyst formulation, which increases fluidized bulk density and allows operation at higher superficial gas velocities, thereby improving both production rate and heat removal capacity simultaneously
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 increases resin bulk density, reactor bed weight, and fluidized bulk density, resulting in higher production rates, improved mechanical properties, and enhanced heat removal capabilities, with a 25% increase in space-time yield and increased superficial gas velocity.
Implementation Method 1
Chromium oxide catalyst system for the production of polyethylene in fluidized bed gas phase reactors
Implementation Method 2
supported chromium oxide catalyst system
Data Source
AI summary
The invention relates to a solid catalyst system comprising a chromium compound, a metal compound, an aluminium compound and a silicon oxide support, wherein the silicon oxide support has an average particle diameter in the range between ≥20 and ≤50 μm, a pore volume in the range between ≥1.7 ml/g and ≤3 ml/g, and a surface area in the range between ≥400 m2/g and ≤800 m2/g and wherein the aluminium alkoxide compound has the formula R1-AI-OR2 wherein R1 is selected from (C1-C8) alkyl groups and OR2 is selected from (C1-C8) alkoxyl groups.