Metal-Modified Molecular Sieve Catalysts for Linear Alkylbenzene Selectivity
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Solution Overview
Problem
Current catalysts for producing long-chain alkylbenzenes face challenges such as high safety and environmental risks, short catalytic cycle life, low product linearity, and high production costs, with existing molecular sieves struggling to inhibit skeletal isomerization and achieve high selectivity and stability in alkylation reactions.
Innovation Solution
A metal-modified silica-alumina molecular sieve with a specific amount and distribution of extra-framework modifying metals, prepared through multiple ion exchanges and calcinations, is used to inhibit skeletal isomerization and improve product linearity and selectivity, combined with a heat-resistant inorganic oxide to form a solid acid catalyst suitable for various reactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional catalysts (hydrofluoric acid or aluminum chloride) are used for alkylation reaction, then high catalytic activity is achieved, but safety and environmental risks increase
Solution Approach 1:
The patent replaces conventional corrosive catalysts with a solid acid catalyst system based on metal-modified molecular sieves. This solid catalyst can be easily replaced and regenerated without causing environmental pollution or safety hazards, effectively solving the contradiction between catalytic activity and safety/environmental risks
Solution Approach 2:
The patent modifies the molecular sieve structure by introducing metal components (such as La, Ce, Sr) to change the catalytic properties. This parameter change enables the solid catalyst to achieve high catalytic activity comparable to conventional catalysts while maintaining safety and environmental benefits
2Duration of action of stationary object
If fluorine-containing SiO2-Al2O3 solid acid catalyst is used, then long-term stable operation is achieved, but equipment corrosion and safety risks remain
Solution Approach 1:
The patent uses a solid acid catalyst based on metal-modified molecular sieves that can be easily replaced and regenerated. This eliminates the use of fluorine-containing catalysts that cause equipment corrosion, while maintaining long-term stable operation through catalyst regeneration
Solution Approach 2:
The patent creates a composite catalyst system by combining metal-modified molecular sieves with heat-resistant inorganic oxide carriers. This composite structure provides both long-term stability and resistance to equipment corrosion
3Productivity
If molecular sieve catalysts are used for long-chain olefin alkylation, then alkylation reaction performance is improved, but product linearity decreases
Solution Approach 1:
The patent introduces metal components (La, Ce, Sr) into specific positions within the molecular sieve structure to create local active sites with different properties. This local modification enables the catalyst to promote alkylation reaction while suppressing skeletal isomerization, thereby improving product linearity
Solution Approach 2:
The patent changes the catalytic parameters by introducing metal modifiers that alter the acid strength and distribution within the molecular sieve. This parameter change enables selective promotion of alkylation while inhibiting isomerization, achieving high product linearity
4Productivity
If conventional molecular sieve catalysts are used, then catalytic activity is achieved, but catalytic cycle life is short
Solution Approach 1:
The patent performs preliminary modification of the molecular sieve structure by introducing metal components before use. This preliminary action creates a more stable and active catalyst structure that maintains high catalytic activity over extended periods, significantly extending the catalytic cycle life
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 metal-modified molecular sieve significantly enhances product linearity and selectivity, extends catalytic cycle life, and allows for long-term continuous operation in industrial processes, achieving high conversion rates and selectivity in alkylation reactions.
Implementation Method 1
The metal-modified molecular sieve, and preparation and use thereof... used to inhibit skeletal isomerization and improve product linearity and selectivity... achieves high conversion rates and selectivity in alkylation reactions
Implementation Method 2
contains a specific amount of extra-framework modifying metal, which can effectively inhibit the skeletal isomerization of long-chain hydrocarbon-based aromatic compound products
Implementation Method 3
prepared through multiple ion exchanges and calcinations
Implementation Method 4
prepared through multiple ion exchanges and calcinations
Data Source
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AI summary
A metal-modified molecular sieve, preparation and use thereof are disclosed. The metal-modified molecular sieve comprises a silica-alumina molecular sieve and a modifying metal selected from an alkaline earth metal, a Group IIIB metal, a Group IIIA metal, or combinations thereof, wherein at least a portion of the modifying metal exists in the form of an extra-framework compensation cation of the molecular sieve, and the modifying metal as element represents from 8 wt.% to 30 wt.% based on the total amount of the metal-modified molecular sieve; in the metal-modified molecular sieve, the ratio of the weight percentage of the surface-layer modifying metal measured by X-ray photoelectron spectroscopy to the weight percentage of the bulk modifying metal measured by X-ray fluorescence does not exceed 1.45, calculated on the basis of the weight percentage of the element. When being used in the preparation of a long-chain hydrocarbon-based aromatic compound, the molecular sieve can effectively inhibit the skeletal isomerization of the target long-chain hydrocarbon-based product, improve the product linearity and the product selectivity, and simultaneously, its catalytic cycle life is also greatly extended.