Propylene Production via Segmented Cracking-Dehydrogenation Packed Beds
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Solution Overview
Problem
Current processes for producing propylene from hydrocarbon feedstocks, such as those obtained from FCC processes, are complex and prone to high coke formation, making them inefficient and inflexible in terms of yield control, especially when using dual riser FCC units or fluidized bed reactors with separate regeneration steps.
Innovation Solution
A process involving a mixture of heterogeneous cracking and dehydrogenation catalysts in packed beds, where the catalysts are arranged in an in-series configuration with a graded distribution along the flow path, reducing coke formation and simplifying the process by using fixed beds instead of fluidized beds, allowing for efficient propylene production with reduced catalyst degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a medium pore zeolite catalyst is added to the FCC catalyst in dual riser configuration to increase propylene yield, then propylene yield is improved, but the process complexity increases and the medium pore zeolite catalyst undergoes degeneration during regeneration
Solution Approach 1:
The reaction system is divided into two separate risers: one for FCC cracking and another for dehydrogenation. This segmentation allows each catalyst type to operate in its optimal environment without interfering with the other, eliminating the complexity of mixing catalysts and avoiding degeneration issues while maintaining high propylene yield
Solution Approach 2:
A separate dehydrogenation riser acts as an intermediary unit between the FCC unit and the separation system. This intermediary handles the dehydrogenation function specifically, allowing the FCC catalyst to focus on cracking without the complications of combined catalyst management, thus simplifying the overall process control
2Object-generated harmful factors
If dehydrogenation is performed in a fluidized bed reactor with separate regeneration to reduce coke formation, then coke formation is reduced, but the process becomes complex
Solution Approach 1:
The system separates cracking and dehydrogenation into different risers with各自 optimized catalyst systems. The dehydrogenation riser uses a catalyst specifically designed for that function, managing coke formation through targeted catalyst selection rather than complex fluidized bed-regeneration systems, thereby reducing overall process complexity
Solution Approach 2:
Each riser is equipped with catalysts having specific properties optimized for their respective functions. The dehydrogenation riser uses a catalyst with appropriate dehydrogenation activity and coke resistance, allowing localized optimization without requiring complex global regeneration systems
3Productivity
If FCC units operate at higher severity to increase propylene yield from 10-12 wt% to 20 wt%, then propylene yield is improved, but catalyst degradation increases and process flexibility decreases
Solution Approach 1:
By separating the dehydrogenation function into a dedicated riser with its own catalyst, the FCC catalyst is protected from operating at excessively high severity conditions. The dehydrogenation catalyst handles the severe conditions, while the FCC catalyst operates in a more favorable environment, maintaining stability and reliability
Solution Approach 2:
The separate dehydrogenation riser acts as a buffer that allows the system to achieve high propylene yields without subjecting the FCC catalyst to damaging high-severity conditions. This intermediary unit protects the FCC catalyst from degradation while maintaining process flexibility
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 significantly reduces coke formation, simplifies the process, and allows for higher propylene yields with improved flexibility in response to changing economic conditions, extending catalyst life and reducing the complexity of the process compared to traditional methods.
Implementation Method 1
contacting the feedstock with a mixture of a heterogeneous cracking catalyst and a heterogeneous dehydrogenation catalyst as present in one or more packed beds thereby obtaining propylene and other reaction products
Data Source
AI summary
The invention is directed to a process to prepare propylene from a hydrocarbon feedstock comprising olefin hydrocarbon compounds by contacting the feedstock with a mixture of a heterogeneous cracking catalyst and a heterogeneous dehydrogenation catalyst as present in one or more packed beds thereby obtaining propylene and other reaction products.