Alternating Catalyst Layers for Syngas Conversion
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Solution Overview
Problem
Current Fischer-Tropsch synthesis processes require separate reactors for synthesis gas conversion and hydrocracking, leading to complex and costly separation schemes and inefficient heat management, resulting in a low yield of naphtha range liquid hydrocarbons and a high yield of wax.
Innovation Solution
A process involving multiple alternating layers of synthesis gas conversion catalysts, hydrocracking catalysts, and hydroisomerization catalysts within a single reactor tube, where synthesis gas is contacted with at least two layers of each type, allowing for sequential reactions under common conditions to produce a hydrocarbon mixture with a high yield of naphtha range hydrocarbons and reduced wax production, while improving heat management through even temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate reactors are used for Fischer-Tropsch synthesis and hydrocracking, then reaction conditions can be optimized for each process, but device complexity and separation cost increase
Solution Approach 1:
The patent combines Fischer-Tropsch synthesis catalyst and hydrocracking catalyst into a single reactor system with alternating catalyst layers. This merging eliminates the need for separate reactors and complex separation schemes while maintaining the ability to optimize reaction conditions for both processes simultaneously within the same reactor environment.
Solution Approach 2:
The reactor is segmented into multiple alternating layers of Fischer-Tropsch synthesis catalyst and hydrocracking catalyst. This segmentation allows each catalyst type to perform its specific function in designated zones while operating under common overall conditions, resolving the contradiction between process optimization and system simplicity.
2Productivity
If Fischer-Tropsch synthesis is performed to produce hydrocarbons, then liquid fuel can be generated, but large quantity of C21+ wax is produced which requires additional hydroprocessing
Solution Approach 1:
The hydrocracking catalyst layers are positioned downstream of the Fischer-Tropsch synthesis catalyst layers, performing preliminary hydrocracking of the wax as it is formed. This preliminary action converts the C21+ wax into desired liquid fuel ranges (C5-C12) within the same reactor, preventing wax accumulation and eliminating the need for separate hydroprocessing units.
Solution Approach 2:
The alternating catalyst layers enable continuous transformation of synthesis gas through Fischer-Tropsch synthesis and subsequent hydrocracking in a single pass. This continuous useful action converts the entire hydrocarbon spectrum from synthesis gas directly into liquid fuel ranges, maintaining high productivity while minimizing unwanted wax production.
3Productivity
If Fischer-Tropsch synthesis is performed under high exothermic conditions, then conversion efficiency increases, but heat removal becomes a primary challenge
Solution Approach 1:
The reactor is divided into multiple alternating layers of synthesis and hydrocracking catalysts, which segments the exothermic reaction zones. This segmentation distributes the heat generation throughout the reactor length, preventing localized overheating and facilitating more effective heat removal while maintaining high overall conversion efficiency.
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 approach results in a high yield of paraffinic hydrocarbons in the naphtha range (C5-C12) with minimal solid wax, achieving efficient heat management and eliminating the need for separate reactors, thus enhancing catalyst life and productivity.
Implementation Method 1
Fischer-Tropsch synthesis is a known means for converting syngas to higher molecular weight hydrocarbon products
Implementation Method 2
Hydrocracking is a known means for cracking hydrocarbons
Implementation Method 3
hydroisomerization catalyst particles including a zeolite component
Implementation Method 4
Fixed bed reactors typically contain many narrow reactor tubes placed within a cooling medium to remove heat
Data Source
AI summary
Disclosed is a process for converting synthesis gas to liquid hydrocarbon mixtures useful in the production of fuels and petrochemicals. The synthesis gas is contacted with at least two layers of synthesis gas conversion catalyst wherein each synthesis gas conversion catalyst layer is followed by a layer of hydrocracking catalyst and hydroisomerization catalyst or separate layers of hydrocracking and hydroisomerization catalysts. The process can occur within a single reactor, at an essentially common reactor temperature and an essentially common reactor pressure. The process provides a high yield of naphtha range liquid hydrocarbons and a low yield of wax.