Ti-MWW Molecular Sieve Crystallization for Fixed-Bed Strength
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Solution Overview
Problem
Ti-MWW molecular sieve catalysts in the prior art suffer from low mechanical strength and poor catalytic performance due to the presence of amorphous binders and extra-framework titanium species that hinder catalytic activity.
Innovation Solution
A method involving shaping, crystallization, and treatment with organic amine and acid solutions to convert Ti-MWW molecular sieve powders into a fully crystalline structure with modified extra-framework hexacoordinated titanium species, enhancing mechanical strength and catalytic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Ti-MWW molecular sieve powders are directly loaded into fixed bed reactors, then the catalytic performance can be maintained, but the mechanical strength is insufficient causing pipeline blockage and difficult separation
Solution Approach 1:
The patent combines Ti-MWW molecular sieve powder with an amorphous aluminosilicate binder to form a composite catalyst. The binder matrix provides mechanical strength and structural integrity, allowing the catalyst to withstand fixed bed reactor conditions without pulverizing, while the dispersed Ti-MWW crystallites maintain catalytic activity. This composite structure resolves the contradiction between mechanical strength and catalytic performance.
2Strength
If amorphous binders are used to improve mechanical strength, then the catalyst can be shaped for fixed bed operation, but the catalytic performance deteriorates due to extra-framework titanium species
Solution Approach 1:
The patent removes extra-framework titanium species from the catalyst structure through selective dissolution treatment. By extracting these inactive titanium species that hinder catalytic activity, the treatment restores the catalytic performance while preserving the amorphous binder matrix that provides mechanical strength. This extraction process resolves the contradiction between mechanical strength and catalytic reliability.
Solution Approach 2:
The patent applies chemical treatment parameters (acid concentration, temperature, time) to modify the catalyst structure. The treatment changes the oxidation state and coordination environment of titanium species, converting extra-framework titanium into more active forms or removing them entirely, thereby improving catalytic performance while maintaining the mechanical strength provided by the binder matrix.
3Strength
If the molecular sieve structure is modified to improve mechanical strength, then the catalyst can withstand reactor conditions, but the channel size and diffusion properties are altered affecting catalytic performance
Solution Approach 1:
The patent segments the catalyst into two functional components: Ti-MWW crystallites that provide catalytic activity through their well-defined channel structures, and an amorphous binder that provides mechanical strength. By separating these functions into distinct segments, the Ti-MWW crystallites can maintain their optimal pore structure for olefin diffusion and epoxidation, while the binder handles the mechanical support role, avoiding the need to modify the crystalline structure itself.
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 resulting Ti-MWW molecular sieve catalyst exhibits high mechanical strength, excellent catalytic activity, and stability in olefin epoxidation, with improved conversion and selectivity for epoxides.
Implementation Method 1
treating the shaped product with an organic amine solution to crystallize the shaped product, thereby obtaining a catalyst precursor
Implementation Method 2
treating the catalyst precursor with an acid solution to obtain a catalyst
Implementation Method 3
crystallizing the shaped product in the presence of an organic amine solution, to obtain a catalyst precursor
Data Source
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AI summary
The present disclosure relates to a Ti-MWW molecular sieve catalyst, a preparation method therefor, and the application thereof. An X-ray photoelectron energy spectrum of the catalyst involves peaks at 458.9±0.2 eV and 464.8±0.2 eV, preferably at 458.9±0.2eV 460.3±0.2 eV, 464.8±0.2 eV and 465.9±0.2 eV. When used in epoxidation of olefins, the Ti-MWW molecular sieve catalyst shows advantages such as high conversion for olefins, high selectivity for epoxides, and good catalytic stability.