Titanium Silicalite Synthesis via Merged Silicon Sources
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Solution Overview
Problem
The existing methods for synthesizing titanium silicalite molecular sieves face challenges such as high costs due to the use of organic silicon sources, lower effective component content, and reduced activity when using inorganic silicon sources or organic quaternary ammonium salts as template agents, along with an imbalance in micropore and mesopore volumes.
Innovation Solution
A process involving the mixing of a titanium source, a template agent, an organic silicon source, water, and an optional inorganic amine source, followed by hydrolysis and aging, then crystallization with a solid silicon source, to produce a titanium silicalite molecular sieve with a higher surface silicon to titanium ratio and balanced micropore and mesopore structures, using a combination of organic and inorganic components to reduce costs and enhance activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If organic silicon source (TEOS) is used for synthesis, then the molecular sieve can be produced, but the cost is high and the solid content in crystallization product is low
Solution Approach 1:
The patent combines organic silicon source (TEOS) and inorganic silicon source (silica gel) in a specific molar ratio (0.1-2:1) to achieve synergistic effects. This merging allows the mixture to form a gel structure that increases solid content while maintaining cost-effectiveness, resolving the contradiction between using expensive organic sources alone and cheap inorganic sources alone.
Solution Approach 2:
The invention creates a composite gel system consisting of organic silicate (TEOS) and inorganic silica gel particles dispersed in alkaline solution. This composite material approach allows the benefits of both organic and inorganic silicon sources to be combined, achieving high solid content crystallization products at reduced cost compared to using pure organic silicon source.
2Reliability
If organic quaternary ammonium salt is used as template agent, then the molecular sieve can be synthesized, but the activity is lower
Solution Approach 1:
The patent changes the chemical composition parameters of the template agent by combining organic quaternary ammonium salt with inorganic ammonium salt in specific molar ratios. This parameter modification maintains the template function while improving catalytic activity, as the inorganic component enhances the titanium species distribution and accessibility in the molecular sieve structure.
Solution Approach 2:
The invention uses a composite template agent system comprising both organic quaternary ammonium salt and inorganic ammonium salt. This composite approach allows the organic component to provide structural template function while the inorganic component enhances catalytic activity, resolving the contradiction between template effectiveness and catalytic performance.
3Ease of manufacture
If inorganic silicon source is used to substitute organic silicon source, then the cost is reduced, but the activity and effective component content are lower
Solution Approach 1:
The patent merges inorganic silicon source (silica gel) with organic silicon source (TEOS) in optimized molar ratios to create a synergistic gel system. This combination allows the inorganic component to reduce cost while the organic component maintains high reactivity and effective titanium incorporation, achieving both cost reduction and activity preservation.
Solution Approach 2:
The invention optimizes the molar ratio parameters between inorganic and organic silicon sources, as well as the ratio of organic to inorganic template agents, to achieve the optimal balance between cost and catalytic activity. By precisely controlling these parameters, the patent ensures that the reduced cost from inorganic silicon source does not compromise the catalytic performance.
4Shape
If conventional synthesis method is used, then the molecular sieve is produced, but the micropore volume is high and mesopore volume is low
Solution Approach 1:
The patent changes the synthesis parameters by using a gel system with specific molar ratios of silicon sources and template agents, along with controlled aging temperature (15-50°C) and time (1-48 hours). These parameter modifications result in a more balanced pore structure with increased mesopore volume while maintaining appropriate micropore volume, improving overall catalytic performance for bulk molecule reactions.
Solution Approach 2:
The invention introduces a preliminary aging step (15-50°C for 1-48 hours) before crystallization to allow the gel structure to develop optimally. This preliminary action prepares the precursor structure with balanced pore distribution, which then directs the formation of the final molecular sieve structure with improved micropore-mesopore balance during the subsequent crystallization process.
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 process results in a titanium silicalite molecular sieve with improved activity and increased solid content, reduced waste emission, and a more efficient use of template agents, achieving a higher surface silicon to titanium ratio and balanced pore volumes, thus enhancing its catalytic performance and reducing production costs.
Implementation Method 1
a titanium source, a template agent, an organic silicon source, water and an optional inorganic amine source are mixed and subjected to hydrolyzation
Implementation Method 2
the aged product obtained in the step (2) and a solid silicon source are mixed homogeneously, then subjected to crystallization in a close reaction vessel
Data Source
AI summary
The present invention relates to a titanium silicalite molecular sieve, wherein the crystal grain of the titanium silicalite molecular sieve has a ratio of (surface Si/Ti ratio):(bulk Si/Ti ratio) being larger than 1.1 and less than 5.