FCC Dehydrogenation Zone for Propylene Yield
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Solution Overview
Problem
Current catalysts in light olefin production, such as propylene, have limited selectivity and yield, with increased additive levels reducing cracking activity and catalyst life, and resulting in higher undesirable dry gas yields.
Innovation Solution
A process that involves passing hydrocarbon streams through a cracking unit, followed by fractionation, dehydrogenation, and oligomerization, with a recycle system to enhance light olefin production by selectively converting heavier hydrocarbons into olefins, thereby increasing ethylene and propylene yields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the temperature is increased to increase propylene yield, then the propylene production increases, but the coking of the catalyst increases, reducing catalyst life and yields
Solution Approach 1:
The patent introduces a dehydrogenation zone that operates at different temperature conditions than conventional FCC processes. By adding this new reaction zone with controlled temperature parameters, the system achieves higher propylene yields through selective dehydrogenation reactions without subjecting the entire catalyst system to excessively high temperatures that would cause rapid coking and deactivation.
2Manufacturing precision
If shape selective additives are used to enhance propylene yields, then the selectivity improves, but the cracking activity is reduced at high additive levels
Solution Approach 1:
The patent divides the cracking function into two separate zones: a conventional FCC riser that maintains high cracking activity for overall hydrocarbon conversion, and a new dehydrogenation zone that provides selective propylene enhancement. This segmentation allows each zone to operate with optimized catalyst formulations - the FCC riser uses catalysts optimized for cracking activity while the dehydrogenation zone uses catalysts optimized for propylene selectivity, eliminating the need to compromise overall cracking activity for additive benefits.
3Productivity
If more catalyst additive is used to increase propylene production, then the propylene yield reaches maximum at 10% crystalline shape selective zeolite content, but the cracking activity is reduced and conversion decreases
Solution Approach 1:
The patent combines two distinct processing functions in a unified system: the conventional FCC cracking process and the new dehydrogenation process. By merging these functions into a single integrated system with a dehydrogenation zone, the process achieves enhanced propylene production through both cracking and dehydrogenation pathways, thereby increasing overall propylene yield without sacrificing conversion of the feedstock.
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 process effectively increases light olefin yields by optimizing the conversion of hydrocarbons, reducing catalyst degradation, and minimizing undesirable by-products, thus addressing the limitations of existing catalysts and meeting growing market demands for propylene.
Implementation Method 1
Catalytic cracking is the process of breaking larger hydrocarbon molecules into smaller hydrocarbon molecules through contacting the larger hydrocarbon molecules with a catalyst at reaction conditions
Implementation Method 2
passing the propane recycle stream to a dehydrogenation unit to generate a fourth stream
Implementation Method 3
passing the sixth stream to an oligomerization unit to generate a seventh stream
Data Source
AI summary
A process is presented for the production of light olefins. The process provides for the separation of the effluent stream from a catalytic cracking process into a stream having light olefins and a stream having heavier hydrocarbons. The heavier stream is oligomerized to generate an oligomer stream having heavier hydrocarbons, and then separated into a stream to be passed to the catalytic cracking process, and a stream to be passed to a reforming unit.