Propylene Epoxidation Catalyst Preparation via Sol-Gel and Silylation
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Solution Overview
Problem
Existing propylene epoxidation catalysts have poor selectivity and high production costs due to complex preparation methods, high template costs, and difficulties in solvent removal from silica gel supports, leading to inefficient oxidizing agent decomposition and high environmental impact.
Innovation Solution
A method involving dissolving titanate and ammonium molybdate in low-carbon alcohol with silica gel, followed by rotary evaporation, calcination under an ammonia atmosphere, and silylation to create a propylene epoxidation catalyst with improved Ti and Mo dispersion and selectivity, eliminating the need for expensive templates and simplifying the production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the chemical vapor deposition method is used to prepare Ti-SiO2 catalyst, then the catalyst can be obtained through a standardized process, but the titanium active species has poor dispersibility on the SiO2 surface and easily forms free TiO2, resulting in ineffective decomposition of the oxidizing agent and reduction of PO selectivity
Solution Approach 1:
The patent changes the preparation parameters from chemical vapor deposition to sol-gel method, altering the chemical state and dispersion characteristics of titanium species. This parameter change enables molecular-level mixing of Ti and Mo precursors with silica gel, preventing TiO2 aggregation and improving PO selectivity while maintaining preparation standardization
Solution Approach 2:
The patent creates a composite catalyst system where Ti and Mo species are simultaneously incorporated into the silica gel matrix through sol-gel processing. This composite approach allows synergistic interaction between Ti active centers and Mo promoters, enhancing both oxidizing agent decomposition efficiency and PO selectivity
2Manufacturing precision
If the sol-gel method is used to prepare Ti-SiO2 catalyst, then different components can be miscible at the molecular level to obtain nano-phase region or even the molecularly dispersed titanium active center, but expensive quaternary ammonium salts need to be added as a template and the template cannot be recovered, resulting in high catalyst costs
Solution Approach 1:
The patent extracts and removes the expensive quaternary ammonium salt template from the sol-gel process by replacing it with ammonia as a simpler, recoverable alkaline agent. This extraction of the problematic template substance eliminates the need for expensive template materials while maintaining the molecular-level dispersion of titanium active centers through controlled hydrolysis and condensation
Solution Approach 2:
The patent substitutes expensive, non-recoverable quaternary ammonium salts with cheap, recoverable ammonia. Although ammonia is consumed during the process, its low cost and ease of recovery make it an economically viable alternative, dramatically reducing catalyst production costs while achieving the same molecular-level mixing effect
3Manufacturing precision
If Mo is supported on the silica gel support followed by solvent washing, then the Ti-Mo-SiO2 catalyst can be prepared, but the silica gel support has a large specific surface area and a small pore size, making it difficult to wash off all of the solvent, thereby affecting the performance of the catalyst and requiring cumbersome separation steps
Solution Approach 1:
The patent performs preliminary action by incorporating the Mo precursor directly into the silica gel matrix during the sol-gel process before any solvent washing is required. The Mo species are uniformly distributed and fixed within the gel structure during gelation, eliminating the need for subsequent solvent removal steps that would be necessary if Mo were added as a separate solution to pre-formed silica gel
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 results in a highly selective and active propylene epoxidation catalyst with reduced production costs, easy recyclability of solvents, and enhanced synergistic effects from nitrogen incorporation into the SiO2 skeleton, improving PO selectivity and catalyst activity.
Implementation Method 1
titanate and ammonium molybdate are dissolved in a low-carbon alcohol, and mixed with a silica gel support to perform a rotary evaporation treatment to remove the low-carbon alcohol
Implementation Method 2
a calcination treatment is performed on the catalyst precursor obtained in step (1) at elevated temperature to obtain an oxide catalyst
Implementation Method 3
a silylation treatment is performed on the oxide catalyst obtained in step (2) using a silylating reagent to obtain the propylene epoxidation catalyst
Data Source
AI summary
Provided are a preparation method for a propylene epoxidation catalyst, and a use thereof. During the preparation, an alkoxide solution of a prepared active component and a silica gel support are mixed, then a rotary evaporation treatment is performed on the mixture to remove a low-carbon alcohol to obtain a catalyst precursor, and then the obtained catalyst precursor is subjected to calcination and silylation treatments to obtain the propylene epoxidation catalyst. The catalyst is prepared in a simple process, can be applied to the chemical process of preparing propylene oxide by propylene epoxidation, has high average selectivity to propylene oxide, and has industrial application prospect.