SUZ-4 Zeolite Catalyst Si/Al Ratio Modification
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Solution Overview
Problem
Current SUZ-4 zeolite-based catalysts for the conversion of oxygenates to olefins have a limited lifespan, requiring continuous regeneration at elevated temperatures and leading to irreversible damage, similar to other catalysts like silicoaluminophosphate molecular sieves (SAPO-34).
Innovation Solution
The catalyst's Si/Al ratio is increased to at least 20 by modifying the zeolite acidity through partial ion-exchange of alkali counter-ions and treating the zeolite with water vapor at elevated temperatures, followed by washing with an aqueous acid solution, to enhance its stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard SUZ-4 zeolite is used for MTO catalysis, then catalytic activity is achieved, but catalyst lifespan is very limited requiring continuous regeneration
Solution Approach 1:
The patent changes the Si/Al ratio parameter from standard values to at least 20, and modifies the acidity parameter through partial ion-exchange of alkali counter-ions. These parameter changes directly address the contradiction by improving catalyst lifespan and stability while maintaining sufficient catalytic activity for continuous operation.
Solution Approach 2:
The patent performs preliminary modification of the zeolite structure before catalysis by increasing the Si/Al ratio and conducting partial ion-exchange to reduce alkali counter-ion content. This preliminary action enhances the catalyst's resistance to deactivation and coke formation, enabling extended operation between regenerations.
2Reliability
If SUZ-4 zeolite undergoes continuous regeneration at elevated temperature, then catalyst activity is restored, but irreversible damage occurs
Solution Approach 1:
By increasing the Si/Al ratio to at least 20, the patent creates a more thermally stable zeolite structure that better withstands regeneration conditions. The modified structure maintains crystallinity and framework integrity even after multiple regeneration cycles, preventing irreversible damage.
3Productivity
If zeolite acidity is increased to improve catalytic activity, then conversion efficiency improves, but catalyst deactivation accelerates
Solution Approach 1:
The patent optimizes the acidity parameter by conducting partial ion-exchange to reduce alkali counter-ion content rather than increasing overall acidity. This approach maintains sufficient catalytic activity while reducing the rate of coke formation and catalyst deactivation, thereby extending catalyst lifespan.
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 modified SUZ-4 zeolite catalyst exhibits improved lifespan and selectivity for light olefins (ethylene and propylene) with reduced aromatic hydrocarbon production, offering a more stable and efficient conversion process for oxygenates to olefins.
Implementation Method 1
partial ion-exchange of alkali counter-ions
Implementation Method 2
treating the zeolite with water vapor at elevated temperatures
Data Source
AI summary
A catalyst for the conversion of oxygenates, such as alcohols or ethers, to olefins consists essentially of a selected SUZ-4 zeolite that has a Si/Al ratio of at least 20, preferably between 20 and 500, especially between 20 and 100. The basic SUZ-4 zeolite is prepared in a manner known per se, whereafter the Si/Al ratio is increased to the desired value. The selected SUZ-4 zeolite catalyst of the invention has a longer life time and a better product selectivity than the conventional/standard SUZ-4 zeolite catalysts.