Catalyst Regeneration for Alkane Dehydrogenation
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Solution Overview
Problem
Current processes for dehydrogenating, dehydroaromatizing, and dehydrocyclizing alkanes and alkyl aromatic hydrocarbons face challenges in achieving high propylene yields without rapid catalyst deactivation due to coke deposition and active phase agglomeration, especially at elevated temperatures.
Innovation Solution
A process involving contacting a hydrocarbon feed with a Pt-based or Group 8-10 element catalyst supported on a specific metal oxide, followed by combustion to regenerate the catalyst, allowing for repeated cycles with maintained activity and stability, achieving high propylene yields under controlled temperature and pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the temperature of the dehydrogenation process is increased to increase propylene conversion, then the equilibrium propylene yield increases, but the catalyst deactivates rapidly due to coke deposition and active phase agglomeration
Solution Approach 1:
The patent implements periodic regeneration cycles where the catalyst is alternately used for dehydrogenation and then regenerated by combustion of deposited coke. This periodic action restores catalyst activity without requiring continuous operation at temperatures that would cause rapid deactivation, thereby maintaining both high propylene yield and catalyst stability over extended periods
Solution Approach 2:
The patent employs temperature modulation as a key parameter change strategy. During the dehydrogenation phase, the catalyst operates at elevated temperatures (560-650°C) to achieve high propylene conversion. During the regeneration phase, the temperature is increased further (600-750°C) to combust coke deposits. This dynamic parameter adjustment allows the system to achieve high productivity while managing catalyst stability through controlled thermal cycles
2Productivity
If the pressure is reduced to increase dehydrogenation efficiency, then the propylene selectivity improves, but the process operates at very low pressure requiring additional equipment complexity
Solution Approach 1:
The patent utilizes pressure as a controllable parameter that can be adjusted between different operating phases. During dehydrogenation, pressure is reduced to 20-50 kPa absolute to maximize propylene selectivity. During regeneration, pressure can be increased to facilitate coke combustion. This flexible parameter adjustment allows optimization of propylene selectivity without permanently requiring complex low-pressure operation
3Reliability
If combustion is used to remove coke from the catalyst, then the catalyst activity is restored, but the agglomeration of the active phase is exacerbated reducing catalyst stability
Solution Approach 1:
The patent applies prior cushioning by carefully controlling the combustion conditions to prevent excessive agglomeration before it occurs. The regeneration is conducted at controlled temperatures and oxygen partial pressures that are sufficient to remove coke but limited enough to prevent severe sintering of the platinum active phase. This preventive approach cushions against the harmful effects of agglomeration while still achieving catalyst regeneration
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 process achieves stable catalyst performance over multiple cycles with enhanced propylene yields, exceeding 90% selectivity, and maintains catalyst activity, overcoming the limitations of rapid deactivation and agglomeration in existing methods.
Implementation Method 1
contacting a hydrocarbon-containing feed with a catalyst that can include Pt disposed on a support to effect one or more of dehydrogenation, dehydroaromatization, and dehydrocyclization
Implementation Method 2
contacting at least a portion of the coked catalyst with an oxidant to effect combustion of at least a portion of the coke
Implementation Method 3
contacting at least a portion of the coked catalyst with an oxidant to effect combustion of at least a portion of the coke
Implementation Method 4
Catalytic dehydrogenation, dehydroaromatization, and dehydrocyclization of alkane and/or alkyl aromatic hydrocarbons are industrially important chemical conversion processes that are endothermic and equilibrium-limited
Data Source
AI summary
Processes for upgrading a hydrocarbon. The process can include (I) contacting a hydrocarbon-containing feed with a catalyst that can include a Group 8-10 element or a compound thereof disposed on a support to effect one or more of dehydrogenation, dehydroaromatization, and dehydrocyclization of at least a portion of the hydrocarbon-containing feed to produce a coked catalyst and an effluent. The process can also include (II) contacting at least a portion of the coked catalyst with an oxidant to effect combustion of at least a portion of the coke to produce a regenerated catalyst. The process can also include (III) contacting an additional quantity of the hydrocarbon-containing feed with at least a portion of the regenerated catalyst. A cycle time from the contacting the hydrocarbon-containing feed with the catalyst in step (I) to the contacting the additional hydrocarbon-containing feed with the regenerated catalyst in step (III) can be ≤5 hours.