SSZ-95 Molecular Sieve Acid Site Density Control
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Solution Overview
Problem
There is a need for new molecular sieves with enhanced selectivity and acid site properties for applications in hydrocarbon conversion, gas separation, and other catalytic processes, as existing sieves like SSZ-32x have limitations in selectivity and gas make during hydrocarbon conversion.
Innovation Solution
The development of SSZ-95 molecular sieve with a unique acid site density and pore architecture, achieved through a specific process involving pre- and post-calcination steps, which converts hydrocarbons efficiently and reduces gas production, particularly C1-C4 gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional SSZ-32x molecular sieve is used for hydrocarbon conversion, then catalytic activity is achieved, but gas production (C1-C4 gases) increases and selectivity decreases
Solution Approach 1:
The patent applies parameter changes by modifying the acid site density of the molecular sieve through controlled pre-calcination and post-calcination treatments. By adjusting calcination temperature and duration, the acid site density is optimized to reduce gas production while maintaining catalytic activity. This directly addresses the contradiction by changing the chemical parameters of the catalyst to achieve better selectivity.
Solution Approach 2:
The patent employs preliminary action through pre-calcination treatment before the main catalytic process. The pre-calcination step partially removes structure directing agents and adjusts acid site distribution in advance, preparing the molecular sieve for optimal performance. This preliminary treatment reduces subsequent gas production during hydrocarbon conversion while preserving catalytic functionality.
2Reliability
If high temperature calcination is applied to remove extra framework cations, then cation removal is improved, but acid site density and selectivity are reduced
Solution Approach 1:
The patent uses preliminary pre-calcination at moderate temperatures (below full decomposition temperature of structure directing agents) to partially remove cations and adjust acid sites before final treatment. This staged approach allows selective cation removal while preserving the molecular sieve's selectivity properties, avoiding the need for aggressive high-temperature calcination that would destroy acid sites.
Solution Approach 2:
The patent implements periodic action through multiple calcination stages: pre-calcination, ion-exchange, and post-calcination. Each stage serves a specific function - pre-calcination removes some cations and SDAs, ion-exchange further purifies the structure, and post-calcination completes cation removal. This periodic treatment achieves thorough cation removal while maintaining selectivity through controlled, progressive heating rather than single high-temperature exposure.
3Manufacturing precision
If structure directing agents are completely removed through high temperature treatment, then structural purity is improved, but acid site density decreases
Solution Approach 1:
The patent applies preliminary pre-calcination at temperatures below the full decomposition temperature of structure directing agents. This preliminary treatment begins SDA removal and structural purification while preserving acid sites that would be destroyed by immediate high-temperature treatment. The process maintains manufacturing precision through controlled, progressive heating.
Solution Approach 2:
The patent uses periodic multi-stage treatment including pre-calcination, ion-exchange, and post-calcination to progressively remove structure directing agents while preserving acid sites. The ion-exchange step between calcination stages allows removal of decomposed SDA residues without exposing the molecular sieve to prolonged high temperatures that would destroy acid sites, achieving both structural purity and acid site density.
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
SSZ-95 exhibits enhanced selectivity and reduced gas production compared to conventional SSZ-32x materials, making it suitable for various hydrocarbon conversion processes and gas separation applications.
Implementation Method 1
subjecting the molecular sieve to a pre-calcination step at a temperature below the full decomposition temperature of the structure directing agent, for a time sufficient to convert at least a portion of the structure directing agent to a decomposition residue
Implementation Method 2
subjecting the molecular sieve to a post-calcination step at a temperature below the full decomposition temperature of the structure directing agent, for a time sufficient to convert at least a portion of the structure directing agent to a decomposition residue
Implementation Method 3
ion-exchanging the pre-calcined molecular sieve to remove extra-framework cations
Data Source
AI summary
A new crystalline molecular sieve designated SSZ-95 is disclosed, as well as its uses. The molecular sieve has a MTT-type framework, a mole ratio of 20 to 70 of silicon oxide to aluminum oxide, a total micropore volume of between 0.005 and 0.02 cc/g; and a H-D exchangeable acid site density of up to 50% relative to SSZ-32.