Faujasite Zeolite Mesoporosity Through Sequential Acid–Base Treatment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods fail to effectively convert steamed USY zeolites with bulk Si/Al < 5 and unit cell size < 24.58 Å into high-quality mesoporous zeolites with preserved intrinsic properties.
Innovation Solution
A sequence of acid and base treatments using specific salts that form multi-ligand complexes with aluminum, followed by controlled pH adjustments, to introduce mesoporosity in faujasite zeolites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional acid-base treatments are applied to steamed USY zeolites, then some mesoporosity is formed, but the intrinsic zeolite properties (crystallinity, microporosity, acidity) are severely reduced
Solution Approach 1:
The treatment process is divided into distinct sequential steps: acid treatment with citric acid to form aluminum complexes, followed by base treatment with NaOH to dissolve these complexes and create mesopores. This segmentation allows controlled modification while preserving intrinsic properties through the specific sequence and conditions of each step.
Solution Approach 2:
The invention uses specific parameter ranges: citric acid concentration (0.1-5 mmol/g zeolite), base treatment pH (10-13), treatment temperatures (room temperature to 100°C), and treatment times (1-24 hours). These controlled parameter changes enable the formation of mesoporosity while maintaining crystallinity and intrinsic zeolite characteristics.
2Stability of the object's composition
If aluminum is removed from the zeolite framework during steam treatment, then the Si/Al ratio increases and stability improves, but the catalytic activity and acidity are reduced
Solution Approach 1:
The invention selectively extracts aluminum from the zeolite framework using citric acid, which forms stable aluminum-citrate complexes that can be dissolved. This controlled extraction creates mesopores and adjusts the Si/Al ratio while preserving the essential catalytic properties through the specific conditions and subsequent base treatment.
Solution Approach 2:
Citric acid acts as an intermediary agent that selectively complexes with aluminum in the zeolite framework. This intermediary forms soluble complexes that can be removed without damaging the zeolite structure, enabling controlled modification of aluminum content while maintaining catalytic activity.
3Stability of the object's composition
If the unit cell size is reduced through steam treatment, then the zeolite becomes more stable, but the pore dimensions change and access to active sites is limited
Solution Approach 1:
The invention introduces a second dimension of porosity (mesopores of 2-50 nm) in addition to the existing micropores. This dimensional expansion provides additional pathways for reactant access to active sites while maintaining the stable framework structure created by steam treatment.
Solution Approach 2:
The mesoporous structure is nested within the zeolite framework, creating a hierarchical pore structure where mesopores provide external access channels while the internal micropores maintain the stable framework. This nested architecture combines the stability of the reduced-unit-cell structure with enhanced accessibility.
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 process yields zeolites with enhanced mesoporosity, higher Brønsted acidity, and preserved microporosity, crystallinity, and BET surface area, suitable for industrial catalytic applications.
Implementation Method 1
The process comprises contacting the to be treated zeolite with an acid, in particular citric acid, which is able to form multi-ligand complexes with aluminum
Implementation Method 2
The process comprises subsequently contacting the acid-treated solid with a base, in particular NaOH
Implementation Method 3
During steam treatment of Y zeolites aluminum from the zeolite framework is expulsed to the bulk of the zeolite
Data Source
AI summary
The invention is broadly drawn to a process to introduce mesoporosity in faujasite zeolites with Si/Al<5 and unit cell sizes below 24.58 Angstrom by an inventive sequence of acid and base treatments, yielding superior physico-chemical and catalytic properties compared to the materials prepared according to the teachings known in the state of the art. Part of the invention relates to the acid step which is executed in the presence of a salt of which the anion is able to form multi-ligand complexes with aluminum, and of which a specific amount of cations are protonic (ca. 90% to 20% of the total cations with −3<pK<6). The superior properties may be the combination of an enhanced mesoporosity with a higher Brønsted acidity, a higher microporosity, a higher mesoporosity, a higher crystallinity, and/or combinations hereof.