Hydrothermally Stable Molecular Sieve Catalyst via Phosphate Modification
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Solution Overview
Problem
Porous molecular sieve catalysts face structural breakdown and reduced catalytic activity due to dealumination when exposed to high-temperature and humid environments, with existing methods failing to provide sufficient hydrothermal stability and selective modification of acid sites.
Innovation Solution
A method involving the modification of surface pores of the molecular sieve with hydrothermally stable phosphate ions stabilized by water-insoluble metal ions, using specific metal salts and phosphate compounds to maintain the structural integrity and activity of the catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If porous molecular sieve catalyst is used in high-temperature and humid environment, then catalytic activity is high, but structural breakdown occurs due to dealumination
Solution Approach 1:
The patent combines molecular sieve catalyst with phosphate compounds and metal compounds to form a composite material system. The phosphate layer forms on the external surface of the molecular sieve, creating a protective composite structure that prevents steam from attacking the Al-O-Si framework while preserving the internal porosity and catalytic sites.
Solution Approach 2:
The modification is applied locally to the external surface of the molecular sieve rather than throughout the entire structure. The phosphate compound selectively modifies the outer surface where steam attack occurs most intensely, leaving the internal framework and pores intact to maintain catalytic function.
2Reliability
If phosphate compound modification is applied to improve hydrothermal stability, then structural stability improves, but acid sites are reduced
Solution Approach 1:
The phosphate modification is localized to the external surface of the molecular sieve, ensuring that acid sites within the internal pores remain unaffected. This selective surface modification protects against hydrothermal degradation while preserving the bulk catalytic activity.
Solution Approach 2:
The phosphate compound acts as an intermediary layer between the steam environment and the molecular sieve framework. It provides protective function against hydrothermal attack while the metal compound further stabilizes this protective layer, allowing the system to maintain both stability and activity.
3Ease of manufacture
If conventional water-soluble metal salt is used for modification, then metal ions are easily introduced, but acid sites are lost due to ion exchange with protons
Solution Approach 1:
The patent changes the chemical form of metal compound from water-soluble salts to water-insoluble forms. This parameter change prevents dissolution and subsequent ion exchange reactions that would consume protons and reduce acid sites, while still allowing the metal compound to provide structural stabilization.
Solution Approach 2:
The water-insoluble metal compound serves as a stable, non-leaching modifier that provides lasting protection without requiring continuous replenishment. Unlike soluble salts that leach and require re-addition, the insoluble form remains permanently fixed on the surface.
Data Source
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AI summary
Disclosed are a hydrothermally stable porous molecular sieve catalyst and a preparation method thereof. The catalyst consists of a product obtained by the evaporation of water from a raw material mixture comprising a molecular sieve having a framework of Si-OH-Al-, a water- insoluble metal salt and a phosphate compound. The catalyst maintains its physical and chemical stabilities even in an atmosphere of high temperature and humidity. Accordingly, the catalyst shows excellent catalytic activity even when it is used in a severe process environment of high temperature and humidity in heterogeneous catalytic reactions, such as various oxidation/reduction reactions, including catalytic cracking reactions, isomerization reactions, alkylation reactions and esterification reactions.