Catalyst Regeneration Cycles for Alkane Dehydrogenation
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Solution Overview
Problem
Current processes for dehydrogenating, dehydroaromatization, and dehydrocyclization of alkanes and alkyl aromatic hydrocarbons face challenges in maintaining catalyst activity and stability due to coke deposition and active phase agglomeration, especially at high temperatures, which reduces propylene yield and selectivity.
Innovation Solution
A process involving a hydrocarbon-containing feed being contacted with a Group 8-10 element-based catalyst at controlled temperatures and pressures, followed by oxidative regeneration and reduction cycles to manage coke combustion and catalyst re-dispersion, thereby maintaining catalyst stability and enhancing propylene yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the temperature of the dehydrogenation process is increased to increase conversion, then the equilibrium propylene yield increases, but the catalyst particles deactivate 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 controlled combustion. The catalyst undergoes cycles of dehydrogenation at high temperature followed by regeneration at lower temperature with limited oxygen, preventing complete deactivation while maintaining high propylene yield over extended operation periods
Solution Approach 2:
The patent changes operational parameters during regeneration by controlling oxygen partial pressure, temperature, and steam addition to manage coke combustion rates. These parameter adjustments prevent runaway combustion that would cause active phase agglomeration while effectively removing coke to restore catalyst activity
2Reliability
If the dehydrogenation process is operated at low pressure to maintain catalyst stability, then catalyst deactivation is reduced, but the efficiency of the dehydrogenation process decreases
Solution Approach 1:
The patent performs preliminary protective actions by adding steam during regeneration to suppress excessive coke formation in advance of the next dehydrogenation cycle. This preventive measure allows the catalyst to maintain stability while operating at higher pressures that improve dehydrogenation efficiency
3Object-generated harmful factors
If coke is removed by combustion using oxygen-containing gas, then coke is eliminated from the catalyst, but agglomeration of the active phase is exacerbated, rapidly reducing activity and stability
Solution Approach 1:
The patent carefully controls combustion parameters including limiting oxygen partial pressure to 0.1-10 kPa, maintaining regeneration temperature at 500-900°C, and controlling the rate of coke combustion to prevent thermal runaway. These parameter changes enable effective coke removal while avoiding conditions that cause active phase agglomeration
Solution Approach 2:
The patent uses steam as an intermediary substance during regeneration that moderates the combustion process. Steam helps control the exothermic reaction, distributes heat more evenly, and prevents localized hot spots that would cause sintering and agglomeration of the active phase
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 sustained catalyst activity and stability over multiple cycles, significantly increasing propylene yield and selectivity, with propylene yields reaching up to 70% or higher at optimized conditions.
Implementation Method 1
contacting the oxidant with the coked catalyst to effect combustion of at least a portion of the coke to produce a regenerated catalyst lean in coke and a second effluent comprising a combustion gas
Implementation Method 2
contacting the reducing gas with the regenerated catalyst to produce a regenerated and reduced catalyst and a third effluent
Implementation Method 3
contacting the hydrocarbon-containing feed with a catalyst disposed within the reaction zone to effect at least one of dehydrogenation, dehydroaromatization, and dehydrocyclization
Data Source
AI summary
Processes for upgrading a hydrocarbon. The process can include introducing, contacting, and halting introduction of a hydrocarbon-containing feed into a reaction zone. The feed can be contacted with a catalyst within the reaction zone to effect dehydrogenation, dehydroaromatization, and/or dehydrocyclization of the feed to produce a coked catalyst and an effluent. The process can include introducing, contacting, and halting introduction of an oxidant into the reaction zone. The oxidant can be contacted with the coked catalyst to effect combustion of the coke to produce a regenerated catalyst. The process can include introducing, contacting, and halting introduction of a reducing gas into the reaction zone. The reduction gas can be contacted with the regenerated catalyst to produce a regenerated and reduced catalyst. The process can include introducing and contacting an additional quantity of the feed with the regenerated and reduced catalyst to produce a re-coked catalyst and additional first effluent.