OCM Reactor Catalyst Bed Area Expansion
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Solution Overview
Problem
The oxidative coupling of methane (OCM) reaction is inefficient on a commercial scale due to high reaction temperatures and large heat of reaction, which leads to reduced selectivity of ethylene production and requires inefficient gas phase coolants.
Innovation Solution
The design of an oxidative methane coupling (OCM) reactor with a catalyst bed assembly that has an upstream face area exceeding the reactor vessel's cross-sectional area, allowing the feed gases to pass through only one catalyst bed, thereby increasing volumetric productivity and reducing reactor size and number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional multi-tubular fixed bed reactors are used with gas phase coolants, then the reactor can operate at high temperatures, but the cooling efficiency is poor and methane conversion must be limited to less than 8% to avoid runaway reactions
Solution Approach 1:
The patent introduces a liquid heat transfer fluid as an intermediary cooling medium that circulates through channels in the catalyst support structure. This liquid coolant efficiently removes reaction heat from the catalyst beds, maintaining optimal reaction temperatures without the inefficiencies of gas phase cooling. The liquid fluid acts as a thermal intermediary between the exothermic reaction zone and the heat exchanger system.
2Productivity
If the catalyst bed surface area is increased to achieve desired reactor throughput, then the reactor size and number must be increased, but this results in excessively high capital cost
Solution Approach 1:
The patent transitions from a conventional two-dimensional catalyst bed configuration to a three-dimensional structured catalyst support with integrated channels. The catalyst is deposited on the walls of channels within a porous support structure, creating multiple reaction pathways in three dimensions. This allows increased catalyst surface area and reactor throughput without proportionally increasing reactor volume, as the catalyst utilizes the internal surface area of the channel network rather than requiring a large external bed volume.
Solution Approach 2:
The patent embeds the catalyst within a structured porous support matrix, where catalyst-coated channel walls are nested within the three-dimensional framework of the support structure. This nested configuration maximizes the catalyst surface area within a compact volume, allowing high productivity in a smaller reactor footprint.
3Speed
If high temperature is used to overcome the strong C-H bond strength of methane, then the reaction proceeds, but excess heat produces carbon monoxide and carbon dioxide instead of desired C2 hydrocarbons
Solution Approach 1:
The patent implements thermal feedback control through the liquid heat transfer fluid system that circulates through the catalyst support channels. The coolant temperature and flow rate can be adjusted to maintain optimal reaction temperature, preventing excessive temperature rise that would lead to undesired complete combustion products. The system provides continuous thermal feedback to keep the reaction in the optimal temperature window for C2 hydrocarbon selectivity.
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 configuration enhances the yield of C2 hydrocarbons and increases the volumetric productivity of the reactor, making the process more economically viable for commercial-scale OCM operations.
Implementation Method 1
A catalyst bed assembly is positioned within the reactor vessel interior. The catalyst bed assembly has at least one catalyst bed containing a layer of OCM catalyst
Implementation Method 2
As shown in Equations (1) and (2), oxidative conversion of methane to ethylene or ethane is exothermic
Data Source
AI summary
An oxidative methane coupling (OCM) reactor has a reactor vessel that defines a reactor vessel interior. The reactor vessel having opposite ends and a central longitudinal axis that extends between the opposite ends. A catalyst bed assembly is positioned within the reactor vessel interior having a catalyst bed containing a layer of OCM catalyst of a uniform thickness. The catalyst bed assembly divides the reactor vessel interior into an upstream zone and a downstream zone. The catalyst bed has an upstream face for receiving the one or more flowing feed gases of methane and oxygen gas as a flowing mixture from the upstream zone. The upstream face of the catalyst bed is configured to have a total area that exceeds the largest transverse cross-sectional area of the interior of the reactor vessel that is perpendicular to the central longitudinal axis of the reactor vessel. The catalyst bed assembly is configured so that any portion of the flowing mixture passes from the upstream zone to the downstream zone through a single catalyst bed of the catalyst bed assembly.