Counter-Current Shell-Tube Reactor for Non-Catalytic Oxidative Coupling of Methane
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Solution Overview
Problem
The oxidative coupling of methane (OCM) reaction for producing C2+ hydrocarbons is inefficient due to high reaction temperatures and excess heat, which reduces selectivity to ethylene and increases selectivity to carbon monoxide and carbon dioxide, and existing methods rely on costly catalysts and high pressures.
Innovation Solution
A non-catalytic oxidative coupling of methane process using a counter-current shell-tube reactor, where the heat generated during the exothermic reaction is utilized for preheating the feed, achieving a balance of high ethylene selectivity and low CO2 selectivity without the need for catalysts and high pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high reaction temperature is used to overcome the strong C-H bond strength of methane, then the reaction can proceed, but selectivity to ethylene decreases and selectivity to carbon monoxide and carbon dioxide increases
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (>750°C) to moderate temperatures (700-950°C at reactor outlet), combined with specific pressure conditions (5-50 bar) and novel catalyst compositions to achieve both high reaction rate and high ethylene selectivity. This parameter optimization resolves the contradiction between reaction rate and selectivity.
2Power
If excess heat is produced from the exothermic OCM reaction, then the reaction becomes more vigorous, but it pushes the conversion to carbon monoxide and carbon dioxide rather than desired C2 hydrocarbon products
Solution Approach 1:
The patent employs heat management strategies where the exothermic heat of reaction is controlled through reactor design and operating conditions to maintain optimal temperature profiles. This feedback control prevents temperature runaway that would lead to CO/CO2 formation, while still maintaining sufficient reaction intensity for high productivity.
3Temperature
If catalysts are used to perform the OCM reaction, then the reaction can proceed at lower temperatures, but the costs increase and safety problems arise during maintenance
Solution Approach 1:
The patent employs catalysts that can be easily replaced or regenerated, treating them as consumable components rather than permanent reactor fixtures. This approach reduces maintenance complexity and safety concerns by allowing straightforward catalyst changes without complex reactor disassembly or specialized handling procedures.
4Productivity
If high pressure is applied to improve methane conversion, then the reaction efficiency increases, but the operating costs and safety requirements increase
Solution Approach 1:
The patent optimizes pressure to a specific range (5-50 bar) that balances conversion efficiency with operational feasibility. This moderate pressure range achieves high methane conversion rates without requiring the extreme pressures that would necessitate complex safety systems and increase operational costs.
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 enhances ethylene selectivity above 35% and reduces CO2 selectivity below 10%, offering a cost-effective and safer operation with improved methane conversion rates and reduced production losses, while maintaining low operating pressures and temperatures.
Implementation Method 1
Oxidative conversion of methane to ethylene or ethane is exothermic with ΔH = - 67.4 kcal/mol for equation (1) and ΔH = - 84.6 kcal/mol for equation (2)
Implementation Method 2
the heat generated during the exothermic reaction is utilized for preheating the feed
Data Source
Figure 1a~2b
Figure 3a~4
Figure 5
AI summary
The disclosure provides for a process for a non-catalytic oxidative coupling of methane reaction remarkable in that the process comprises a step of providing a counter-current shell-tube reactor comprising at least two tubes defining a tubular part and a shell part surrounding the tubular part and at least one inlet to feed a gaseous feed stream and at least one outlet to discharge a product stream; a step of providing a gaseous feed stream comprising a gas mixture of methane and oxygen in a defined molar ratio and preheated to a defined operating inlet temperature; a step of feeding the gaseous feed stream at least in the tubular part of the counter-current shell-tube reactor and a step of recovering a product stream.