Multilayer Catalyst Segmentation for Hot Spot Control in Alkene Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Industrial-scale production of unsaturated aldehydes and carboxylic acids from alkenes via gas-phase catalytic oxidation faces challenges with hot spot temperature generation, leading to reduced catalyst life and yield instability due to variations in reactor structure, heat removal, and gas flow distribution, posing a risk of runaway reactions.
Innovation Solution
A method involving a fixed bed multitubular reactor with multiple catalyst layers, where the hot spot temperature change relative to reaction bath temperature is regulated to a specified value, using a complex metal oxide catalyst formulation to maintain stable yield and prevent excessive hot spot formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gas-phase catalytic oxidation is used to produce unsaturated aldehyde and/or carboxylic acid from alkene, then productivity is improved, but hot spot temperature increases causing catalyst deterioration and yield reduction
Solution Approach 1:
The catalyst layer is divided into multiple segments with different activities arranged in sequence from the inlet side to the outlet side of the reaction tube. The first catalyst layer has lower activity to suppress hot spot formation, while subsequent layers have progressively higher activity to maintain productivity. This segmentation resolves the contradiction by distributing the oxidation reaction across multiple zones with controlled temperature profiles.
Solution Approach 2:
Different portions of the catalyst layer are given different local qualities (activities) to address different requirements. The inlet portion uses low-activity catalyst to control temperature, while downstream portions use high-activity catalyst to maximize conversion. This local differentiation allows simultaneous achievement of temperature control and high productivity.
2Productivity
If catalyst activity is increased to maintain yield, then productivity is improved, but hot spot temperature increases leading to runaway reaction risk
Solution Approach 1:
The catalyst system is segmented into multiple layers with progressively increasing activity. The first layer operates at lower activity to ensure safety and temperature control, while subsequent layers gradually increase activity to achieve high yield. This segmented approach prevents runaway reactions while maintaining productivity.
Solution Approach 2:
The low-activity catalyst layer is placed at the inlet side to perform preliminary oxidation at controlled temperatures before the gas stream enters the high-activity zones. This preliminary action prevents excessive temperature rise that could lead to runaway reactions, while still achieving the desired yield through subsequent catalytic stages.
3Reliability
If catalyst activity is decreased to suppress hot spot, then reaction safety is improved, but productivity and yield decrease
Solution Approach 1:
Instead of using a single low-activity catalyst throughout, the system segments the catalyst into multiple layers with increasing activity. The first layer provides safety through lower activity, while subsequent layers progressively increase activity to restore and maintain high productivity and yield.
Solution Approach 2:
Different local qualities (catalyst activities) are assigned to different positions in the reaction tube. The inlet region uses low-activity catalyst for safety, while downstream regions use high-activity catalyst for productivity. This spatial differentiation of quality resolves the contradiction between safety and yield.
4Device complexity
If scattering in reaction tube diameter and heat removal capability exists, then device complexity is reduced, but temperature distribution uniformity worsens causing catalyst deterioration
Solution Approach 1:
The catalyst layers are designed with different local qualities (activities) that compensate for the inherent non-uniformities in heat removal capability across different reaction tubes. By adjusting catalyst activity locally, the system maintains stable temperature profiles and prevents catalyst deterioration despite variations in reactor geometry and heat transfer.
Solution Approach 2:
The catalyst activity parameter is changed across different layers to compensate for variations in heat removal. The progressive increase in catalyst activity from inlet to outlet compensates for the non-uniform temperature distribution caused by scattering in reaction tube diameter and heat removal capability, maintaining stable operation.
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 ensures a high and stable yield over a long period by controlling hot spot temperature fluctuations, reducing thermal stress on the catalyst and preventing runaway reactions, thereby enhancing operational safety and efficiency in industrial plants.
Implementation Method 1
gas-phase catalytic oxidation in the presence of molecular oxygen or a molecular oxygen-containing gas, thereby producing an unsaturated aldehyde and/or an unsaturated carboxylic acid each corresponding to the alkene
Implementation Method 2
the generation of a local high-temperature portion (hot spot) in a catalyst layer is of a serious problem
Data Source
AI summary
Provided is a method of subjecting an alkene to partial oxidation by using a fixed bed multitubular reactor, thereby producing an unsaturated aldehyde and/or an unsaturated carboxylic acid each corresponding to the alkene, wherein a plurality of catalyst layers formed by N division (N is N≧2) with respect to a gas flow direction of a reaction tube are provided, and when a change (° C.) of hot spot temperature per 1° C. change of reaction bath temperature in the catalyst layer is designated as Sn, at least one of the plurality of catalyst layers is regulated to Sn≦6.