Continuous MDA Hydrogenation with Split Reactors for Isomer Control
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Solution Overview
Problem
Existing hydrogenation processes for producing methylenebis(cyclohexylamine) face challenges in achieving defined proportions of isomers and are energy-intensive due to the circulation of product substreams, leading to increased formation of unwanted by-products and high energy costs.
Innovation Solution
A plant and process with a closed media circulation system and separate adiabatic postreactor, combined with isothermal operation of the main reactor, allowing precise control of temperature gradients to achieve desired isomer ratios and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If circulation of product substreams is used in hydrogenation processes, then product conversion is improved, but energy consumption increases and unwanted by-products are formed
Solution Approach 1:
The reactor system is divided into multiple separate reactors (first reactor, second reactor, third reactor) with different functions. The first reactor performs main hydrogenation, the second reactor handles isomerization, and the third reactor completes the conversion. This segmentation allows each reactor to operate optimally without requiring continuous circulation of product substreams, thereby reducing energy consumption while maintaining high product conversion.
Solution Approach 2:
A separate isomerization reactor is introduced as an intermediary unit between the main hydrogenation reactor and the final product separation. This intermediary reactor specifically addresses the isomerization step, allowing the main reactor to focus on hydrogenation without energy-intensive circulation to achieve isomer control.
2Productivity
If circulation of product substreams is used, then product conversion is improved, but formation of unwanted by-products increases
Solution Approach 1:
By dividing the process into separate functional reactors, each unit can be optimized for its specific purpose. The first reactor is optimized for hydrogenation with controlled conditions to minimize by-product formation, while the second reactor specifically handles isomerization. This segmentation prevents the formation of unwanted by-products that would occur during circulation processes.
Solution Approach 2:
Different operating parameters are applied to each reactor: the first reactor operates at conditions optimized for hydrogenation (lower temperature, controlled pressure), while the second reactor operates at conditions optimized for isomerization. These parameter changes allow high conversion without by-product formation.
3Productivity
If high trans/trans isomer content is produced, then productivity is improved, but manufacturing precision for specific isomer ratios deteriorates
Solution Approach 1:
The isomerization function is separated into a dedicated second reactor, allowing precise control of isomer ratios independent of the main hydrogenation process. This enables the system to produce high trans/trans isomer content when needed while maintaining the ability to control specific isomer ratios for different product specifications.
Solution Approach 2:
The system can dynamically adjust the operation of the isomerization reactor based on product requirements. By controlling the feed to the second reactor and adjusting operating parameters, the system can produce different isomer ratios (e.g., high trans/trans for certain applications or controlled ratios for others) while maintaining high overall productivity.
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
The process achieves a trans/trans isomer ratio of 22% by weight in methylenebis(cyclohexylamine) with improved product conversion and energy efficiency, enabling production of high-quality products with low trans/trans content.
Implementation Method 1
continuous catalytic hydrogenation of MDA
Implementation Method 2
at least one heat exchanger in at least one (feed) conduit
Implementation Method 3
at least one condenser in the (tops) conduit of the separation tank
Implementation Method 4
Hydrogenation of MDA is highly exothermic. For example, WO 2010/069484 A1 indicates an enthalpy of reaction of −1600 kJ/mol
Data Source
AI summary
A plant for hydrogenation of methylenedianiline with a hydrogen donor has a conditioning unit for the reactants, a reactor unit and a separation unit. The reactor unit has at least one fixed bed reactor as main reactor with an immobile catalyst packing, and the separation unit has at least a first separation stage having at least one apparatus for removing the solvent, and wherein a second separation stage has at least one apparatus for separation of at least one reactant and/or at least one by-product from the PACM product.