Pt/Kβ Molecular Sieve Catalyst for Alkane Aromatization
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Solution Overview
Problem
Current catalysts for aromatization of long-chain alkanes suffer from low aromatic hydrocarbon conversion, short service life, and high coking rates, making them unsuitable for improving gasoline quality and industrial raw material production.
Innovation Solution
A β molecular sieve with a BEA topological structure is modified through ammonium ion-exchange, hydrothermal treatment, and potassium ion-exchange, followed by platinum loading and calcination, to create a catalyst with improved stability and selectivity for aromatization of long-chain alkanes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a platinum-loaded KL-type molecular sieve is used for aromatization, then the pore structure facilitates reactant diffusion, but the one-dimensional feature causes easy coking and low catalyst stability
Solution Approach 1:
The patent transitions from the one-dimensional pore structure of KL-type molecular sieve to the three-dimensional pore architecture of ZSM-5 molecular sieve. This dimensional change allows for better catalyst stability and reduced coking while maintaining adequate reactant diffusion through the 3D channel system.
Solution Approach 2:
The patent employs metal-modified ZSM-5 catalysts, combining the three-dimensional pore structure of ZSM-5 with metal components to create a composite material that achieves both good stability and catalytic activity, resolving the contradiction between stability and diffusion.
2Reliability
If metal-modified ZSM-5 catalysts are used for aromatization, then the three-dimensional pore architecture provides stability, but the medium pore openings are not conducive to diffusion of long carbon-chain alkanes and produce大量 dry gas byproducts
Solution Approach 1:
The patent modifies the pore size parameter by using a larger pore molecular sieve (L-type or Y-type) compared to ZSM-5, enabling better diffusion of long carbon-chain alkanes. Simultaneously, it adjusts the acidity parameter through metal modification and hydrodesulfurization treatment to reduce dry gas byproduct formation while maintaining stability.
Solution Approach 2:
The patent applies local modification by introducing metal components and performing hydrodesulfurization treatment in specific regions of the catalyst to reduce acidity locally, thereby decreasing dry gas formation while maintaining the overall three-dimensional stable structure.
3Reliability
If ZSM-5 with strong acidity is used for aromatization, then the catalyst structure is stable, but it leads to formation of low aromatic hydrocarbon content (40%) and large amount of dry gas byproducts
Solution Approach 1:
The patent performs hydrodesulfurization treatment on the catalyst to reduce its strong acidity, which was originally causing harmful dry gas formation. By controlling the acidity level, the patent converts the harmful strong acid sites into beneficial moderate acid sites that promote aromatic hydrocarbon formation while reducing byproduct generation.
4Productivity
If existing catalysts are used for aromatization of long-chain alkanes, then the process can proceed, but the aromatic hydrocarbon conversion is low and service life is short
Solution Approach 1:
The patent develops a universal catalyst system (metal-modified L-type or Y-type molecular sieve) that simultaneously achieves high aromatic hydrocarbon conversion and long service life. The catalyst is designed to handle various long-chain alkanes while maintaining stability, making it multi-functional for both high productivity and extended duration.
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 modified Pt/Kβ molecular sieve catalyst exhibits high aromatic hydrocarbon selectivity and extended service life, with toluene selectivity reaching 85.5% and a service life of over 170 hours, significantly surpassing existing catalysts in terms of stability and performance.
Implementation Method 1
sequentially subjecting a Naβ molecular sieve to ammonium ion-exchange and first calcination to obtain an Hβ molecular sieve
Implementation Method 2
subjecting the Hβ molecular sieve to first hydrothermal treatment in an ammonium fluorosilicate aqueous solution and then second calcination
Implementation Method 3
sequentially subjecting the modified Hβ molecular sieve to potassium ion-exchange and third calcination to obtain a modified Kβ molecular sieve
Implementation Method 4
impregnating the modified Kβ molecular sieve with a platinum-containing solution and then conducting fourth calcination to obtain a modified Pt/Kβ molecular sieve
Data Source
AI summary
The present invention provides a catalyst for aromatization of a long-carbon chain alkane and a preparation method thereof. In the present invention, a molecular sieve containing a BEA structure is taken as an active component and mixed with a carrier, and then the mixture is formed, dried and calcined to obtain the catalyst for aromatization of a long-carbon chain alkane. The active component is prepared by taking a Naβ molecular sieve as a raw material and modifying through the following steps of: first obtaining an Hβ molecular sieve through ammonium ion-exchange, and then conducting dealumination and silicon insertion treatment of the Hβ molecular sieve through first hydrothermal treatment; forming a mesoporous structure in a molecular sieve framework through second hydrothermal treatment; reducing the acidity of the catalyst by potassium ion exchange, and finally using metal modification to improve the capability of the catalyst for catalyzing the aromatization of the long-carbon chain alkane and enhancing the toluene selectivity. The catalyst provided by the present invention shows high stability in the aromatization of the long-chain alkane and has a service life up to 170 h or above and aromatic hydrocarbon selectivity up to 80%, and the selectivity to toluene in aromatic hydrocarbon products can reach 85.5%.