Hydrodechlorination Reactor Segmentation for Mass Transfer
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Solution Overview
Problem
Current methods for purifying monochloroacetic acid from crude monochloroacetic acid containing dichloroacetic acid are inefficient due to high energy consumption, costly separation processes, and limited conversion rates in industrial-scale reactors, particularly in vertical tubular reactors, which face challenges in hydrodynamics and catalyst separation.
Innovation Solution
A process for catalytic hydrodechlorination in an industrial-scale vertical tubular reactor with a diameter of 0.4 m or greater, where the liquid feed is trickled over a fixed bed of a heterogeneous catalyst with a specific range of superficial mass and gas velocities, achieving a high average axial pressure gradient, and using a catalyst with metals from Group VIII of the Periodic Table, such as palladium on an activated carbon carrier, to convert dichloroacetic acid into monochloroacetic acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If catalytic hydrodechlorination is performed in conventional vertical tubular reactors, then dichloroacetic acid is converted to monochloroacetic acid, but mass transfer rates are limited and conversion is incomplete
Solution Approach 1:
The catalyst bed is segmented into multiple zones with different catalyst compositions and activities. The upper zone contains a first catalyst composition optimized for certain conditions, while the lower zone contains a second catalyst composition optimized for other conditions. This segmentation allows different regions to perform different functions, improving overall mass transfer rates and conversion efficiency.
Solution Approach 2:
Different portions of the catalyst bed are given different local qualities through varying catalyst compositions, particle sizes, and distributions. The catalyst composition is tailored locally to match the specific requirements of different zones in the reactor, optimizing both mass transfer and conversion at each location.
2Manufacturing precision
If crystallization is used to purify monochloroacetic acid, then dichloroacetic acid concentration is reduced, but space and time requirements are considerable
Solution Approach 1:
The process changes the fundamental approach by using catalytic hydrodechlorination instead of crystallization. This chemical conversion method operates at much faster rates than physical separation methods, achieving high purity product within minutes rather than requiring extended crystallization time.
3Manufacturing precision
If distillation is used to remove dichloroacetic acid, then separation is achieved, but energy consumption is high and the process is uneconomical
Solution Approach 1:
The patent replaces the energy-intensive mechanical separation process of distillation with a catalytic chemical conversion process. By using catalysts to convert dichloroacetic acid into monochloroacetic acid, the process eliminates the need for high-energy separation operations while achieving the desired purification.
4Productivity
If conventional catalytic hydrodechlorination is used, then some conversion is achieved, but catalyst inventory is high and process complexity increases
Solution Approach 1:
The catalyst bed is segmented into multiple zones with different catalyst compositions. This allows each zone to be optimized for specific functions, improving conversion rates while using less total catalyst material. The segmented structure also simplifies catalyst separation and reuse.
Solution Approach 2:
The patent optimizes catalyst parameters including composition, particle size, and distribution to maximize conversion efficiency. By carefully controlling these parameters, the process achieves high conversion rates with reduced catalyst inventory and simplified 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 enhances mass transfer rates, achieves conversion close to plug flow, and minimizes catalyst inventory, resulting in a higher purity of monochloroacetic acid production while reducing energy consumption and operational complexities.
Implementation Method 1
catalytic hydrodechlorination step by contacting it with a source of hydrogen to convert the dichloroacetic acid into monochloroacetic acid in the presence of a solid heterogeneous hydrogenation catalyst
Implementation Method 2
contacting it with a source of hydrogen to convert the dichloroacetic acid into monochloroacetic acid
Implementation Method 3
enhances mass transfer rates
Implementation Method 4
achieving a high average axial pressure gradient
Data Source
AI summary
The process of the present invention pertains to a process wherein a liquid feed comprising monochloroacetic acid, dichloroacetic acid,and optionally acetic acid and/or trichloroacetic acid is subjected to a catalytic hydrodechlorination step by contacting it with a source of hydrogen in the presence of a solid heterogeneous hydrogenation catalyst situated in a fixed catalyst bed, wherein the liquid feed is fed to the top of avertical tubular reactor at a superficial mass velocity of between and 10 kg/s per square meter of the horizontal cross-section of the vertical tubular reactor and a rate of between 250 and 3,000 kg/hr per m of said catalyst bed, wherein the source of hydrogen is fed to the top or bottom of the vertical tubular reactor at a rate of between 0.025 to 0.25 Nm/s per square meter of the horizontal cross-section of the vertical tubular reactor, so as to obtain an average axial pressure gradient of at least 2 kPa per meter of said catalyst bed, and wherein the temperature in the top of the vertical tubular reactor is between 100 and 200°C, and wherein the pressure in the top of the vertical tubular reactor is between 0.2and 1.0 MPa.