Fluidized Bed Reactor Zone Segmentation for Nitrile Yield
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Solution Overview
Problem
In fluidized bed reactors, unsaturated nitriles produced in the dense catalyst zone are prone to decomposition when passing through the sparse catalyst zone, leading to reduced yield due to catalyst deterioration and reaction conditions.
Innovation Solution
A process optimizing the fluidized bed reactor by defining a dense zone with a catalyst concentration of 150 kg/m3 or more and a sparse zone with less than 150 kg/m3, controlling gas residence time in the sparse zone to 5-50 seconds, maintaining a superficial gas velocity below 1 m/s, and adjusting oxygen concentration in the reaction product gas to 0.1-5.0 vol%, with specific relations between gas residence time and oxygen concentration to prevent decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gas residence time in the sparse zone is extended to ensure complete reaction, then the conversion rate improves, but the unsaturated nitrile decomposes due to prolonged exposure to catalyst
Solution Approach 1:
The fluidized bed reactor is divided into two distinct zones: a dense zone for the ammoxidation reaction and a sparse zone for product separation. This segmentation allows the reaction and decomposition processes to be spatially separated, enabling high conversion in the dense zone while minimizing decomposition in the sparse zone by controlling residence time to 5-50 seconds.
Solution Approach 2:
The patent applies the 'rushing through' principle by minimizing the gas residence time in the sparse zone to 5-50 seconds. This allows the reaction product gas to quickly pass through the sparse zone after being produced in the dense zone, reducing the exposure time to catalyst that would otherwise cause decomposition of the unsaturated nitrile product.
2Productivity
If the catalyst concentration is increased to enhance reaction efficiency, then the production rate improves, but the decomposition of unsaturated nitrile increases in the sparse zone
Solution Approach 1:
The patent applies local quality by creating distinct catalyst concentration zones within the reactor. The dense zone maintains high catalyst concentration (≥150 kg/m³) to ensure efficient reaction, while the sparse zone maintains low catalyst concentration (<150 kg/m³) to minimize product decomposition. This spatial variation in catalyst density optimizes both production rate and product stability.
3Productivity
If the oxygen concentration is increased to accelerate the ammoxidation reaction, then the reaction rate improves, but the decomposition reaction of unsaturated nitrile is promoted
Solution Approach 1:
The patent segments the reactor into zones with different oxygen concentration requirements. The dense zone maintains high oxygen concentration to drive the ammoxidation reaction forward, while the sparse zone controls oxygen concentration to prevent decomposition reactions, thereby achieving both high reaction rate and product stability.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting oxygen concentration based on the spatial location within the reactor. Oxygen concentration is optimized for the ammoxidation reaction in the dense zone and controlled to prevent decomposition in the sparse zone, demonstrating parameter optimization across different operational zones.
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 the yield of unsaturated nitriles by minimizing decomposition, ensuring stable production over time by carefully managing catalyst distribution, gas flow, and oxygen concentration within the reactor zones.
Implementation Method 1
a reaction step of subjecting the hydrocarbon to a vapor phase catalytic ammoxidation reaction in the presence of the catalyst in the internal space to produce the corresponding unsaturated nitrile
Implementation Method 2
a fluidized bed reactor comprising an internal space comprising a catalyst capable of being fluidized therein
Data Source
AI summary
A process for producing unsaturated nitrile, using a fluidized bed reactor having an internal space having a catalyst capable of being fluidized therein, a feed opening to feed a starting material gas comprising hydrocarbon to the internal space, and a discharge port to discharge a reaction product gas from the internal space, the process comprising a reaction step of subjecting the hydrocarbon to a vapor phase catalytic ammoxidation reaction in the presence of the catalyst in the internal space to produce the corresponding unsaturated nitrile, wherein when in the internal space, a space where an existing amount of the catalyst per unit volume is 150 kg/m3 or more is defined as a dense zone and a space where an existing amount of the catalyst per unit volume is less than 150 kg/m3 is defined as a sparse zone in the reaction step, a gas residence time in the sparse zone is 5 to 50 sec.