Titanium Silica Epoxidation Catalyst Stability
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Solution Overview
Problem
Current catalysts for olefin epoxidation, such as titanated silica catalysts, face challenges in stability, activity, and selectivity, particularly in maintaining effectiveness over time and under varying conditions.
Innovation Solution
A method for preparing catalysts involves impregnating an inorganic siliceous solid with titanium tetrachloride, followed by calcination at specific temperatures and subsequent reaction with specific compounds to enhance stability and activity, including a cross-linking step using halogenated hydrocarbons like methylene chloride, resulting in a catalyst with improved performance for epoxidation reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional titanated silica catalysts are used for olefin epoxidation, then the catalytic activity is maintained, but the catalyst stability and selectivity deteriorate over time and under varying conditions
Solution Approach 1:
The patent applies parameter changes by modifying the catalyst preparation conditions, specifically using controlled hydrolysis of alkoxysilane compounds at specific water-to-alkoxysilane ratios (0.5-2.0) and controlled condensation conditions. This results in a more stable silica support structure with improved catalyst reliability while maintaining high activity through optimized titanium loading (0.1-10 wt%).
Solution Approach 2:
The patent creates a composite catalyst system consisting of titanium species dispersed on a modified silica support that has been treated with alkoxysilane compounds. This composite structure combines the high activity of titanium catalysts with the enhanced stability and selectivity of the modified silica support, resolving the contradiction between activity and stability.
2Productivity
If the catalyst is designed for high initial activity, then the epoxidation reaction rate increases, but the catalyst selectivity and long-term effectiveness worsen
Solution Approach 1:
The patent applies local quality by creating specific active sites on the catalyst surface through controlled titanium dispersion on the modified silica support. The alkoxysilane treatment creates localized regions with enhanced stability and selectivity properties, while titanium species are distributed to maintain high reaction activity. This local optimization allows high productivity without sacrificing selectivity.
3Ease of manufacture
If the catalyst structure is simplified for ease of manufacture, then the production process becomes easier, but the catalyst performance and stability deteriorate
Solution Approach 1:
The patent applies preliminary action by pre-modifying the silica support with alkoxysilane compounds before titanium loading. This preliminary modification creates a stable support structure that enhances catalyst reliability. The process remains relatively simple as it uses straightforward impregnation and drying steps, but the preliminary treatment ensures high catalyst effectiveness and stability.
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 method produces catalysts with increased activity for epoxidation reactions, demonstrated by higher tert-butylhydroperoxide conversion rates and improved selectivity, reducing catalyst leaching and maintaining effectiveness over a range of conditions.
Implementation Method 1
contacting an inorganic siliceous solid with titanium tetrachloride to produce a titanium tetrachloride-impregnated solid
Implementation Method 2
calcining the titanium tetrachloride-impregnated solid at a temperature from 500 °C to 1000 °C to produce a pre-catalyst
Implementation Method 3
reacting the pre-catalyst with a compound of the formula: wherein: R 1 , R 2 , R 3 , R 4 , and R 5 are each are each -H; at 100 °C to 300 °C and under conditions suitable for forming the stabilized catalyst
Data Source
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AI summary
Method of preparing epoxidation catalysts are disclosed, including methods comprising reacting an inorganic siliceous solid with a metal complex of the formulas: wherein the variables are defined herein.