Multilayer Catalyst for Stable Alkene Oxidation
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Solution Overview
Problem
In gas-phase catalytic partial oxidation of alkenes to produce unsaturated aldehydes and carboxylic acids, conventional methods face challenges such as catalyst deterioration, reduced yield, and short catalyst life due to high reaction bath temperatures, especially under high-load conditions, and the mechanical strength of catalysts is insufficient, leading to hot spots and reduced selectivity.
Innovation Solution
A method involving a multitubular oxidation reactor with complex metal oxide catalysts, where the bismuth to molybdenum ratio decreases and the iron to molybdenum ratio increases along the reactor axis, ensuring high selectivity and activity on the inlet side and long catalyst life, while maintaining low reaction bath temperatures through multilayer filling and specific catalyst formulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the reaction bath temperature is increased to maintain high catalyst activity under high-load conditions, then the productivity increases, but the catalyst deterioration is accelerated and catalyst life becomes short
Solution Approach 1:
The catalyst layer is segmented into multiple zones with different catalyst compositions and activities along the axial direction. The first zone contains catalyst with lower activity to reduce hot spot formation, while subsequent zones contain catalyst with progressively higher activity to maintain overall productivity. This segmentation allows the system to operate at high load without excessive temperature increase that would degrade the catalyst.
Solution Approach 2:
Different regions of the catalyst layer are given different local properties through varying catalyst composition and activity. The inlet region uses catalyst formulations optimized for stability and hot spot suppression, while outlet regions use catalyst formulations optimized for high conversion. This local quality differentiation enables the system to achieve high productivity without subjecting the entire catalyst layer to temperatures that would reduce catalyst life.
2Productivity
If the reaction bath temperature is increased to maintain high catalyst activity, then the reaction rate increases, but excessive oxidation reaction is promoted and the yield of target product is lowered
Solution Approach 1:
The catalyst layer is divided into zones with different oxidation activities. The first zone uses catalyst with controlled activity to prevent excessive oxidation, while subsequent zones progressively increase activity to achieve high conversion. This segmentation ensures that the reaction proceeds through controlled stages, maintaining high yield while achieving the required reaction rate for high productivity.
Solution Approach 2:
The catalyst composition parameters are changed along the axial direction to control the oxidation reaction. By varying the catalyst formulation (e.g., metal oxide ratios, promoters) in different zones, the system achieves different local reaction rates and selectivities, allowing high overall productivity while maintaining high target product yield through controlled oxidation at each stage.
3Temperature
If catalysts with high activity are used to decrease reaction bath temperature, then the productivity can be maintained at low temperature, but the selectivity is lowered due to high activation of the catalyst
Solution Approach 1:
Instead of using a single high-activity catalyst throughout, the system segments the catalyst layer into zones with progressively increasing activity. The first zone uses lower-activity catalyst to maintain high selectivity at the reaction onset, while subsequent zones use higher-activity catalyst to drive conversion to completion. This allows the system to operate at lower overall temperatures while maintaining both selectivity and productivity.
Solution Approach 2:
Different local catalyst qualities are employed in different regions. The inlet region uses catalyst formulations optimized for high selectivity and moderate activity, while outlet regions use formulations optimized for high conversion. This local quality differentiation enables the system to achieve low operating temperatures without sacrificing selectivity, as each zone performs its specific function optimally.
4Reliability
If the supporting amount of catalyst is increased from inlet to outlet to suppress hot spot, then the conversion is improved, but the layer thickness increases and reaction heat accumulates within the catalyst
Solution Approach 1:
The catalyst layer is segmented into zones with different supporting amounts and compositions. The first zone has lower catalyst supporting amount to facilitate heat dissipation and prevent hot spot formation. Subsequent zones have progressively higher supporting amounts to increase conversion. This segmentation allows the system to suppress hot spots in the inlet region while achieving high conversion in outlet regions without excessive heat accumulation.
Solution Approach 2:
The catalyst supporting amount and composition parameters are changed along the axial direction. By progressively increasing the catalyst loading and optimizing the formulation in each zone, the system achieves better heat management in inlet regions while maintaining high conversion capability in outlet regions. This parameter variation allows hot spot suppression without sacrificing overall conversion efficiency.
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 approach allows for stable, high-yield production of unsaturated aldehydes and carboxylic acids even under high-load conditions, with controlled reaction temperatures and extended catalyst life, reducing production costs and maintaining catalytic performance.
Implementation Method 1
gas-phase catalytic partial oxidation with molecular oxygen in the presence of the complex metal oxide catalyst
Implementation Method 2
gas-phase catalytic partial oxidation with molecular oxygen
Implementation Method 3
since the gas-phase catalytic partial oxidation of propylene or the like is an exothermic reaction, a local high-temperature portion (hot spot) is generated in a catalyst layer
Data Source
AI summary
Provided is a method capable of producing acrolein and/or acrylic acid, or methacrolein and/or methacrylic acid, stably in a high yield over a long period of time advantageously even in a high-load reaction, and the method is a method in which when preparing two or more kinds of catalysts having different formulations and stacking two or more layers in the axial direction of the tube, the catalysts are filled in such a manner that not only the component amount of bismuth relative to molybdenum decreases from the gas inlet side toward the gas outlet side, but also the component amount of iron relative to molybdenum increases from the gas inlet side toward the gas outlet side.