Double-Component Modified Molecular Sieve for Hydrothermal Stability
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Solution Overview
Problem
The existing molecular sieves, particularly ZSM-5 zeolites, suffer from deactivation under hydrothermal conditions, affecting their stability and selectivity in catalytic cracking, and introducing a second modifying constituent via ion exchange often results in the washing away of phosphorus, compromising the modification's purpose and catalytic activity.
Innovation Solution
A double-component modified molecular sieve is prepared by adding a molecular sieve to an aqueous solution containing phosphorus, followed by filtering, drying, and calcining, and then reacting with silver ions under controlled pH and temperature conditions, enhancing the diffusion of modifying constituents into the molecular sieve's pores and improving hydrothermal stability and catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ZSM-5 zeolite molecular sieve is used for catalytic cracking, then light olefin yield is increased, but hydrothermal stability deteriorates under catalytic cracking conditions
Solution Approach 1:
The patent modifies the molecular sieve by changing its chemical composition parameters - specifically incorporating phosphorus and silver components in controlled amounts (0.1-10 wt% P2O5, 0.01-2 wt% Ag2O) to alter its hydrothermal stability while maintaining catalytic activity for light olefin production
Solution Approach 2:
The patent creates a composite modified molecular sieve by combining ZSM-5 zeolite with phosphorus and silver components. This composite structure integrates multiple functional elements: the base ZSM-5 provides shape-selective catalysis for light olefin yield, phosphorus enhances hydrothermal stability, and silver contributes to catalytic activity, achieving synergistic effects that resolve the stability-productivity contradiction
2Reliability
If phosphorus modification is performed to improve hydrothermal stability, then stability is enhanced, but catalytic activity deteriorates due to acid site loss
Solution Approach 1:
The patent applies local quality modification by introducing phosphorus and silver at specific locations and concentrations within the molecular sieve structure. The phosphorus primarily targets hydrothermal stability enhancement, while silver is distributed to maintain and enhance catalytic activity at acid sites, creating regions with different functional properties that collectively resolve the stability-activity contradiction
Solution Approach 2:
The patent optimizes the concentration parameters of phosphorus (0.1-10 wt% P2O5) and silver (0.01-2 wt% Ag2O) to achieve the desired balance. By precisely controlling these compositional parameters, the modification enhances hydrothermal stability while the silver component compensates for any acid site loss, maintaining catalytic activity
3Productivity
If double-component modification with phosphorus and silver is performed, then hydrothermal stability and catalytic activity are improved, but manufacturing complexity increases
Solution Approach 1:
The patent employs preliminary action by pre-mixing phosphorus and silver compounds in an aqueous solution before impregnation. This preliminary preparation of the modifying solution simplifies the subsequent impregnation process, as both components are introduced simultaneously in a single step rather than requiring separate sequential treatments, thus reducing manufacturing complexity while achieving double-component modification
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 molecular sieve with enhanced hydrothermal stability and catalytic activity, preventing phosphorus loss during ion exchange and increasing the yields of light olefins by maintaining acid site reservation and facilitating free radical reactions.
Implementation Method 1
adding a molecular sieve to an aqueous solution containing phosphorus, followed by filtering, drying, and calcining
Implementation Method 2
enhancing the diffusion of modifying constituents into the molecular sieve's pores
Implementation Method 3
reacting with silver ions under controlled pH and temperature conditions
Implementation Method 4
facilitating free radical reactions
Implementation Method 5
the primary process for traditional production of ethylene and propylene, i.e. steam pyrolysis, is performed by the free radical reactions
Implementation Method 6
maintaining acid site reservation and facilitating free radical reactions
Data Source
AI summary
A method for producing double-component modified molecular sieve comprises adding molecular sieve to an aqueous solution containing phosphorus to form a mixture, allowing the mixture to react at pH of 1-10, temperature of 70-200° C. and pressure of 0.2-1.2 MPa for 10-200 min, and then filtering, drying and baking the resultant to obtain phosphorus-modified molecular sieve, and then adding the phosphorus-modified molecular sieve to an aqueous solution containing silver ions, allowing the phosphorus-modified molecular sieve to react with silver ions at 0-100° C. in dark condition for 30-150 min, and then filtering, drying and baking. The obtained double-component modified molecular sieve contains 88-99 wt % molecular sieve with a ratio of silica to alumina between 15 and 60, 0.5-10 wt % phosphorus (based on oxides) and 0.01-2 wt % silver (based on oxides), all based on dry matter. A catalyst produced from the double-component modified molecular sieve has improved hydrothermal stability and microactivity.