High Silica Zeolite Production from Fly Ash
Solution Overview
Problem
The synthesis of high silica content zeolites from fly ash is hindered by the presence of non-reactive phases and the need for external silica sources, limiting commercialization and applications.
Innovation Solution
A process involving the fusion of fly ash in a basic medium, followed by treatment with a mineral acid, selective chelating agents to remove impurities, and mineralizing agents to form an aluminosilicate gel, which is then crystallized hydrothermally to produce high silica content zeolites like ZSM-5 without external silica sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If external silica sources are added to increase the Si:Al molar ratio, then high silica content zeolites can be produced, but non-reactive phases such as mullite and quartz appear in the final product
Solution Approach 1:
The patent extracts and removes non-reactive phases (mullite and quartz) from the fly ash through selective dissolution in basic medium followed by acid treatment. This extraction process separates the harmful non-reactive components from the reactive aluminosilicate phases, allowing high silica content zeolites to be produced without the contamination of non-reactive phases that would otherwise form when external silica sources are added.
Solution Approach 2:
The patent changes the chemical parameters of the fly ash by controlling the Si:Al molar ratio through selective removal of aluminum rather than adding silica. By adjusting the basic medium composition and treatment conditions, the process transforms the fly ash composition in-situ, achieving the desired high silica content while avoiding the formation of non-reactive phases associated with external silica addition.
2Quantity of substance
If external silica sources are added to alter the Si:Al molar ratio, then the desired zeolite product can be obtained, but the commercialization and applications of fly ash-based zeolite are limited
Solution Approach 1:
The patent enables fly ash to serve itself by using the aluminosilicate phases already present in the fly ash to produce high silica content zeolites. The process requires no external silica sources, making fly ash a self-sufficient feedstock. This self-service approach eliminates the need for additional raw materials, reduces manufacturing complexity, and enhances commercial viability by directly valorizing the available fly ash resources.
Solution Approach 2:
The patent achieves the desired Si:Al molar ratio through parameter changes in the treatment process rather than by adding external materials. By controlling the basic medium composition, temperature, and treatment time, the process selectively modifies the fly ash composition in-situ, making the manufacturing process simpler and more commercially attractive by eliminating the need for external silica sources and associated processing steps.
3Ease of manufacture
If fly ash is used as starting material, then cost reduction is achieved, but the presence of non-reactive phases hinders the synthesis of high silica content zeolites
Solution Approach 1:
The patent extracts non-reactive phases (mullite and quartz) from the fly ash through selective dissolution and acid treatment. This extraction process removes the components that hinder zeolite synthesis while preserving the reactive aluminosilicate phases. By taking out the harmful non-reactive phases, the process maintains the cost advantage of using fly ash while significantly improving synthesis efficiency and reliability.
Solution Approach 2:
The patent performs preliminary treatment of fly ash through basic medium dissolution and acid processing before the actual zeolite synthesis. This preliminary action pre-conditions the fly ash by removing non-reactive phases and adjusting the composition, ensuring that the subsequent zeolite synthesis proceeds efficiently. This preliminary preparation resolves the contradiction by enabling reliable high silica content zeolite production from low-cost fly ash without the interference of non-reactive phases.
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
This method effectively increases the Si:Al molar ratio, reducing impurities and achieving high purity zeolites like ZSM-5, enhancing the commercial viability of fly ash-based zeolite production.
Implementation Method 1
fusing a fly ash containing starting material in the presence of a basic medium to form a fused reaction mixture
Implementation Method 2
which mixture is brought into contact with a mineral acid, then separated to produce a first fly ash material
Implementation Method 3
treating the first fly ash material with a selective chelating agent to produce an impurity depleted zeolite feedstock
Implementation Method 4
treating the zeolite feedstock with a mineralising agent; optionally further treating the zeolite feedstock with a structure directing agent to form an aluminosilicate containing gel
Implementation Method 5
crystallising the aluminosilicate containing gel in a hydrothermal crystallisation step to form the aluminosilicate zeolite
Data Source
AI summary
The present invention provides for a process for the production of an aluminosilicate zeolite from fly ash, and in particular but not exclusively, to a process for producing a high silica content zeolite from fly ash without the addition of an external silica source, such as sodium silicate.