Ti-SiO2 Catalyst Preparation via Liquid Ammonia Molding
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Solution Overview
Problem
Existing methods for preparing Ti—SiO2 composite oxide catalysts for propylene epoxidation suffer from poor dispersibility of Ti active species on SiO2 surfaces, leading to ineffective oxidant decomposition and reduced selectivity to propylene oxide, and require expensive template agents, increasing catalyst costs.
Innovation Solution
A sol method is used to prepare the catalyst by molding in liquid ammonia, followed by pore broadening, drying, calcination, and silanization, without the need for template agents, incorporating Re and Zn modifications to enhance catalyst activity and selectivity, resulting in improved Ti species dispersion and reduced production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chemical vapor deposition method is used to prepare Ti—SiO2 catalyst, then the catalyst can be obtained through vapor phase reaction, but Ti active species have poor dispersibility on SiO2 surface and free TiO2 is easily formed, resulting in reduced selectivity to propylene oxide
Solution Approach 1:
The invention changes the preparation method from chemical vapor deposition to sol-gel method, altering the physical and chemical parameters of the preparation process. The sol-gel method uses liquid precursors that can be uniformly mixed at molecular level, enabling better dispersion of Ti species on SiO2 surface and preventing formation of free TiO2, thereby improving selectivity to propylene oxide
Solution Approach 2:
The invention creates a composite Ti—SiO2 catalyst where titanium species are intimately dispersed within the silica matrix at the molecular level. The sol-gel process forms a homogeneous composite structure where Ti and Si components are mixed at molecular level before gelation, ensuring uniform distribution and preventing aggregation of Ti species
2Manufacturing precision
If sol-gel method is used to prepare Ti—SiO2 catalyst, then different components can be miscible at molecular level and titanium active centers with nano-phase regions can be obtained, but expensive quaternary ammonium salt template agent must be added, resulting in higher catalyst costs
Solution Approach 1:
The invention extracts and removes the expensive quaternary ammonium salt template agent from the preparation process. By using a template-free sol-gel method with appropriate control of hydrolysis and condensation conditions, the invention achieves the desired porous structure and molecular-level mixing without requiring the template agent, thereby significantly reducing catalyst production cost while maintaining high dispersibility of Ti active species
Solution Approach 2:
The invention replaces the expensive quaternary ammonium salt template agent with inexpensive, easily removable substances or no template at all. The temporary structures formed during gelation can be removed by simple washing or low-temperature treatment, eliminating the need for costly template agents while achieving the desired catalyst structure
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 achieves high selectivity to propylene oxide with reduced catalyst costs, improved activity, and simplified production, with selectivity up to 97.5% and cost savings by eliminating the need for template agents.
Implementation Method 1
dissolving a silicon source and a titanium source respectively in alcohol solvents, adding a quaternary ammonium ion (such as cetyl ammonium bromide) as a template agent, and forming a gel by hydrolysis, polymerization, and aging
Implementation Method 2
forming a gel by hydrolysis, polymerization, and aging
Implementation Method 3
molding in liquid ammonia
Implementation Method 4
pore broadening
Implementation Method 5
calcinating at high temperature
Implementation Method 6
calcination and silanization treatment
Implementation Method 7
calcination and silanization treatment
Implementation Method 8
Re and Zn are used to modify the catalyst, which is obtained by molding in liquid ammonia, pore broadening, drying, calcination at high temperature and silanization treatment; by using Re and Zn to modify the catalyst, the synergistic effect of Re, Zn, and Ti can improve the activity of the catalyst and the selectivity to propylene oxide
Data Source
AI summary
A preparation method for a propylene epoxidation catalyst: pre-hydrolyzing a silicon source, adding a titanium source and reacting to form a sol, atomizing the sol and then spraying it into liquid ammonia for molding, implementing pore broadening, and performing drying, calcination, and silanization treatment to obtain a Ti—SiO2 composite oxide catalyst. The present catalyst can be used in the chemical process of preparing propylene oxide by epoxidation of propylene, the average propylene oxide selectivity being up to 97.5%, having prospects for industrial application.