Shell-and-tube reactor with graded catalyst layers
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Solution Overview
Problem
Existing methods for producing unsaturated aldehydes and unsaturated acids, such as (meth)acrolein and (meth)acrylic acid, face challenges with hot spot formation in catalytic reactors, leading to reduced yield and catalyst deactivation due to temperature control issues and inefficient catalyst utilization.
Innovation Solution
A shell-and-tube reactor with multiple catalytic layers, where each layer has a different pore density and/or size in the catalytically active component, allowing the specific surface area to increase from the reactor inlet to outlet, thereby controlling temperature and maintaining catalyst stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single catalytic layer is used in the reactor, then the device complexity is low, but hot spot formation occurs leading to reduced yield and catalyst deactivation
Solution Approach 1:
The catalytic layer is divided into multiple sub-layers with different pore densities and particle sizes. This segmentation allows different regions of the catalyst bed to operate at different temperatures and activity levels, preventing hot spot formation while maintaining high yield. The first catalytic sub-layer has lower pore density and the second has higher pore density, creating a gradient that manages heat generation effectively.
Solution Approach 2:
Different portions of the catalytic layer are given different properties (pore density, particle size) to suit local requirements. The inlet region uses catalyst with lower pore density to manage heat generation, while the outlet region uses catalyst with higher pore density to maintain activity. This local differentiation resolves the contradiction between simplicity and productivity.
2Productivity
If catalyst activity is increased to improve yield, then productivity increases, but hot spot temperature increases causing catalyst deactivation
Solution Approach 1:
The pore density and particle size parameters of the catalyst are varied across different layers. By changing these physical parameters, the heat generation and heat transfer characteristics are optimized. The gradient in pore density creates a corresponding gradient in thermal conductivity and heat capacity, allowing high activity catalyst to operate without causing excessive hot spots that would deactivate the catalyst.
Solution Approach 2:
The catalyst is segmented into multiple layers with different activity levels and thermal properties. This segmentation allows the most active catalyst to be placed where heat dissipation is most effective, while less active catalyst is placed where heat accumulation would be problematic. The result is maintained catalyst stability alongside high productivity.
3Ease of manufacture
If uniform catalyst distribution is used throughout the reactor, then manufacturing is simple, but heat transfer efficiency is reduced leading to hot spots
Solution Approach 1:
The catalyst packing is designed with local quality variations - different pore densities and particle sizes in different regions. This can be achieved through simple sequential packing processes where catalyst mixtures are introduced in stages. The method balances manufacturing simplicity with effective heat transfer by creating natural thermal management zones without complex equipment.
4Productivity
If reaction temperature is increased to improve reaction rate, then productivity increases, but complete oxidation occurs producing by-products
Solution Approach 1:
The catalytic bed is segmented into zones with different temperature profiles and catalytic activities. The segmentation creates a temperature gradient that prevents localized overheating and complete oxidation. By distributing the exothermic reaction heat across multiple layers with different thermal characteristics, the system maintains optimal temperatures for partial oxidation while preventing the harmful complete oxidation side reaction.
Solution Approach 2:
The multi-layer catalyst structure acts as an intermediary that mediates between the reactants and the desired product. The gradient in pore density and particle size creates intermediate zones that control heat transfer and mass transfer, preventing direct contact between highly exothermic reaction zones and the product formation zones, thus preventing complete oxidation.
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 enhances the yield of unsaturated aldehydes and acids while stabilizing the catalyst, reducing by-product formation and extending catalyst lifespan by effectively managing heat distribution and activity across the reactor.
Implementation Method 1
Reaction heat generated during the reaction is removed by heat transfer with a heat transfer medium
Implementation Method 2
heat transfer medium for heat exchange is provided on the outer surface of the reaction tubes to perform heat transfer
Implementation Method 3
a multimetal oxide containing molybdenum and bismuth or vanadium or a mixture thereof is used as a catalyst
Implementation Method 4
propylene or the like is oxidized by oxygen, diluted inert gas, water vapor and an optional amount of catalyst to produce (meth)acrolein 2 as a main product
Implementation Method 5
catalytic vapor phase oxidation is a highly exothermic reaction. Therefore, it is very important to control the reaction temperature in a specific range
Data Source
AI summary
Disclosed is a shell-and-tube reactor that may be used for fixed-bed catalytic partial oxidation, the reactor being characterized by including at least one reaction zone of a first-step reaction zone for mainly producing unsaturated aldehydes and a second-step reaction zone for mainly producing unsaturated acids, wherein at least one reaction zone of the above reaction zones comprises two or more catalytic layers; each of the catalytic layers is packed with a formed product of catalyst that is different in pore density and/or pore size in a catalytically active component; and the pore density and/or pore size is controlled in such a manner that specific surface area of the catalytically active component increases from the inlet of the reactor to the outlet of the reactor. A method for producing unsaturated aldehydes and/or unsaturated fatty acids from olefins using the same reactor is also disclosed. According to the present invention, it is possible to control the temperature efficiently at a hot spot, thereby permitting stable use of a catalyst, and to produce unsaturated aldehydes and/or unsaturated fatty acids with high yield.