Reverse-Flow Dehydrocyclization Reactor for Aromatic Yield
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Solution Overview
Problem
Conventional processes for producing aromatic hydrocarbons, such as benzene, from non-aromatic hydrocarbons face challenges in achieving high yield with minimal catalyst coking and methane production, requiring complex separation processes and catalyst deactivation issues.
Innovation Solution
A catalytic dehydrocyclization process in a reverse-flow reactor using a dehydrocyclization catalyst with a molecular sieve and dehydrogenation components, where a portion of the oxidant is consumed upstream to combust coke deposits and provide additional heating, allowing for increased feed conversion and reduced methane selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional dehydrocyclization processes operate at high temperature to increase aromatic hydrocarbon yield, then the yield of aromatic hydrocarbon is improved, but the rate of catalyst coking increases leading to catalyst deactivation
Solution Approach 1:
The reactor operates in periodic cycles alternating between dehydrocyclization mode (forward flow) and combustion mode (reverse flow). During dehydrocyclization, aromatic hydrocarbons are produced at high temperature. During combustion mode, the flow direction reverses and coke accumulated on the catalyst is burned off, restoring catalyst activity. This periodic alternation allows sustained high productivity without permanent catalyst deactivation.
Solution Approach 2:
The harmful coke deposits that cause catalyst deactivation are periodically removed through combustion during reverse-flow mode. The oxidant introduced during combustion mode reacts with and removes the coke, effectively discarding the harmful accumulation and recovering the catalyst's original activity for subsequent dehydrocyclization cycles.
2Reliability
If reverse-flow oxidation is used to remove coke deposits, then catalyst coking is reduced, but the desired monotonic temperature profile is disrupted increasing reversion reactions
Solution Approach 1:
The system periodically switches between dehydrocyclization mode (forward flow producing aromatics) and combustion mode (reverse flow removing coke). The periodic nature allows the temperature profile to be monotonic during each dehydrocyclization phase while still enabling coke removal during the brief combustion phase, minimizing disruption to aromatic production.
Solution Approach 2:
During combustion mode, the flow direction is inverted (reverse flow) to introduce oxidant that combusts coke deposits. This inversion temporarily disrupts the normal temperature profile but restores catalyst activity. The key insight is that this inversion is brief and periodic, allowing the system to recover and maintain overall productivity.
3Productivity
If the reaction zone is reheated by combusting fuel upstream, then dehydrogenation efficiency is improved, but coke removal from the catalyst is reduced
Solution Approach 1:
The system alternates between dehydrocyclization mode where fuel combustion upstream reheats the reaction zone for efficient dehydrogenation, and combustion mode where reverse flow introduces oxidant to remove coke from the catalyst. This periodic switching ensures both high dehydrogenation efficiency and catalyst stability are maintained over time.
Solution Approach 2:
During combustion mode, the oxidant removes coke deposits from the catalyst through combustion, discarding the harmful accumulation. The periodic nature ensures that after reheating and efficient dehydrogenation, the catalyst is periodically cleaned, maintaining both productivity and reliability.
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 higher feed conversion with reduced catalyst coking and methane yield, maintaining aromatic hydrocarbon selectivity, even with refractory feeds like ethane, and allows for efficient regeneration of the catalyst.
Implementation Method 1
catalytic dehydrocyclization of substantially non-aromatic C2+ hydrocarbon
Implementation Method 2
a second portion of the oxidant flow is combusted within the reaction zone with at least a portion of the deposited coke
Implementation Method 3
combusts at least a portion of the accumulated coke
Implementation Method 4
Heat is transferred from the combustion products to the reaction zone to re-heat the reaction zone
Data Source
AI summary
The invention relates to hydrocarbon dehydrocyclization to produce products such as aromatic hydrocarbon, to equipment and materials useful for dehydrocyclization, to processes for carrying out dehydrocyclization, and to the use of dehydrocyclization for, e.g., natural gas upgrading. The dehydrocyclization is carried out in a catalytic reaction zone of a reverse-flow reactor.