Modified Catalyst for Olefin Aromatization via Segmentation
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Solution Overview
Problem
Current one-step processes for converting ethane to aromatic hydrocarbons face limitations due to high temperature requirements, leading to catalyst deactivation, low carbon utilization, and excessive production of low-value methane and heavy fractions, with noble metal catalysts prone to migration and sintering.
Innovation Solution
A modified catalyst with a specific acidic molecular sieve and olefin aromatization active metal component, subjected to steaming treatment, is used in a two-step process for dehydrogenation and aromatization, reducing acid amount and extending catalyst life, while improving BTX product yield and carbon utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high temperature (above 750°C) is used for alkane dehydrogenation, then dehydrogenation activity is improved, but catalyst deactivation due to coking and cracking increases
Solution Approach 1:
The patent divides the conversion process into two separate steps: dehydrogenation in a first reactor and aromatization in a second reactor. This segmentation allows each reactor to operate under optimized conditions - the first reactor can use high temperature for dehydrogenation while the second reactor uses lower temperature (400-500°C) for aromatization, avoiding the catalyst deactivation problem that would occur if both reactions were combined in one reactor at high temperature.
2Reliability
If temperature is reduced to 400-500°C for olefin aromatization, then catalyst stability is improved, but dehydrogenation activity decreases
Solution Approach 1:
The patent separates the dehydrogenation and aromatization reactions into two distinct reactors, allowing the aromatization reactor to operate at the optimal temperature range of 400-500°C for catalyst stability, while the dehydrogenation reactor operates at higher temperature to maintain dehydrogenation activity. The segmented approach eliminates the need to compromise on either front.
3Device complexity
If one-step process is used for direct conversion, then process complexity is reduced, but carbon utilization decreases due to high methane and heavy fraction production
Solution Approach 1:
The patent implements a two-step process with separate reactors for dehydrogenation and aromatization. This segmentation allows precise control over reaction conditions in each step, enabling the aromatization reactor to operate under conditions that maximize BTX selectivity and minimize methane and heavy fraction formation, thereby improving carbon utilization despite the increased process complexity.
Solution Approach 2:
The patent changes the operating parameters between the two reactors - the first reactor operates at high temperature for dehydrogenation, while the second reactor operates at lower temperature (400-500°C) with optimized space velocity and pressure conditions for aromatization. These parameter changes enable better control over product distribution and reduce unwanted byproducts.
4Productivity
If noble metal catalysts are used for dehydrogenation, then dehydrogenation activity is improved, but catalyst reliability decreases due to metal migration and sintering
Solution Approach 1:
The patent separates the dehydrogenation and aromatization functions into different reactors. The dehydrogenation reactor can use noble metal catalysts when needed, while the aromatization reactor uses a non-noble metal catalyst (such as iron-based) that is stable at the lower operating temperature of 400-500°C. This segmentation reduces the overall risk of noble metal migration and sintering by limiting their exposure to high-temperature conditions.
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 catalyst significantly reduces methane and ethane selectivity, increases BTX product selectivity, and extends catalyst cycle life, achieving higher economic efficiency and stability compared to unmodified Ga/ZSM-5 catalysts.
Implementation Method 1
subjecting a catalyst containing an acidic molecular sieve and an olefin aromatization active metal component to a steaming treatment with flowing steam or a mixed stream of flowing steam and an inert gas
Implementation Method 2
ethane first needs to be dehydrogenated and activated to the intermediate ethylene which has high reactivity
Implementation Method 3
the ethylene is oligomerized/aromatized on the acid sites to convert into the aromatic hydrocarbon compounds
Implementation Method 4
oligomerized/aromatized on the acid sites to convert into the aromatic hydrocarbon compounds
Implementation Method 5
oligomerization/aromatization is usually performed on a zeolite catalyst such as ZSM-5
Data Source
AI summary
The present disclosure provides a modified catalyst, and preparation method and a method for producing aromatic hydrocarbons by aromatization of olefins using the modified catalyst. The modified catalyst comprises an acidic molecular sieve and an olefin aromatization active metal component, the total acid amount of the catalyst as measured by NH3-TPD method is not higher than 0.35 mmol/g, and ratio of the strong acid to weak acid is within a range of 0.8-1.2.