MAPD Selective Hydrogenation in Propylene Purification
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Solution Overview
Problem
The conventional Catofin process for propylene production suffers from propylene production losses due to MAPD-induced catalyst deactivation and fouling, leading to reduced product quality, increased safety risks, and shortened catalyst life, as MAPD decomposition causes excessive pressure and temperature in the splitter column.
Innovation Solution
A process involving the selective hydrogenation of methyl acetylene and propadiene (MAPD) using a high-selectivity catalyst followed by low-selectivity catalysts to convert MAPD into propylene, reducing MAPD concentration and eliminating the need for a propylene slip stream, thereby preventing coke formation and extending catalyst life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a propylene slip stream is used to control MAPD concentration in the C3 Catofin Process, then MAPD concentration is reduced, but propylene production is lost and catalyst life is shortened
Solution Approach 1:
The patent extracts and removes MAPD from the process stream through selective hydrogenation in a dedicated reactor unit, separating this function from the main propylene production stream. This allows MAPD control without requiring propylene slip stream, thereby preventing propylene loss and extending catalyst life in the dehydrogenation reactors.
Solution Approach 2:
The patent introduces hydrogen as an intermediary substance to enable selective hydrogenation of MAPD to propylene in a separate reactor. This intermediary approach allows MAPD conversion without directly using propylene slip stream, thus avoiding the trade-off between MAPD control and propylene production.
2Productivity
If MAPD is present in the recycle stream, then propylene can be produced, but coke formation increases and catalyst deactivation accelerates
Solution Approach 1:
The patent applies preliminary action by removing MAPD from the recycle stream through selective hydrogenation in a dedicated reactor before the stream re-enters the dehydrogenation process. This preliminary MAPD removal prevents coke formation during subsequent dehydrogenation reactions, thereby protecting catalysts while maintaining propylene production.
3Reliability
If propylene slip stream is cracked and dehydrogenated in the reactors, then MAPD concentration is controlled, but additional coke is formed and catalyst life is reduced
Solution Approach 1:
The patent extracts MAPD from the process stream through selective hydrogenation in a dedicated reactor unit, separating this function from the main propylene production stream. This allows MAPD control without requiring propylene slip stream, thereby preventing propylene loss and extending catalyst life in the dehydrogenation reactors.
4Productivity
If conventional dehydrogenation process is used, then propylene is produced, but MAPD decomposition causes excessive pressure and temperature in the splitter column
Solution Approach 1:
The patent applies preliminary action by removing MAPD from the recycle stream through selective hydrogenation in a dedicated reactor before the stream re-enters the dehydrogenation process. This preliminary MAPD removal prevents coke formation during subsequent dehydrogenation reactions, thereby protecting catalysts while maintaining propylene production.
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 effectively reduces propylene losses, enhances catalyst stability, improves safety by preventing thermal oxidation, and increases the operational life of the Catofin catalyst, while maintaining the specificity of the propylene production process.
Implementation Method 1
contacting the first hydrocarbon stream with a first catalyst bed in the presence of hydrogen to at least partially hydrogenate the methyl acetylene and the propadiene to propylene
Implementation Method 2
contacting the second hydrocarbon stream with a second catalyst bed to at least partially remove unreacted hydrogen from the second stream
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A propane dehydrogenation and propylene purification process in which a stream comprising propylene, propane, and methyl acetylene and propadiene (MAPD) is mixed with a hydrogen stream then reacted in at least three distinct reaction zones in a hydrogenation reactor system where MAPD is hydrogenated by a high-selectivity hydrogenation catalyst in a first reaction zone, and a second and a third reaction zones each have a low-selectivity hydrogenation catalyst to remove unreacted hydrogen. The outlet stream leaving the hydrogenation reactor system is MAPD-free and can be fed to a splitter column, which now mainly serves to separate propylene from propane. Various embodiments of reaction zone arrangements in a single or multiple reactors are also provided.