Thermal Conversion Reactor Backmixing Control
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Solution Overview
Problem
The existing processes for preparing methyl methacrylate (MMA) and methacrylic acid (MA) suffer from inadequate yield stability and efficiency due to backmixing and varying dwell times in thermal conversion steps, leading to the formation of by-products and waste, particularly in the ACH-sulfo process.
Innovation Solution
The process involves optimizing the sulfuric acid concentration and using flow-optimized thermal conversion apparatuses with plug flow profiles to minimize backmixing and control dwell times, ensuring consistent and high yields of methacrylamide (MAA) and subsequently MMA or MA, by employing a combination of preheater and delay segments in the reactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal conversion is performed with extended dwell time to convert HIBAm to MAA, then conversion completeness improves, but yield decreases due to degradation of MAA and formation of tar-like deposits
Solution Approach 1:
The conversion process is divided into two distinct segments: a first conversion stage that operates at higher temperature for shorter time to convert SIBA to MAA, and a second conversion stage at lower temperature for longer time to convert HIBAm to MAA. This segmentation allows each stage to be optimized independently, preventing over-conversion and degradation while ensuring complete conversion of both intermediates.
Solution Approach 2:
The SIBA intermediate is converted to MAA in advance during the first conversion stage before the HIBAm conversion is complete. This preliminary action removes the more easily degradable MAA from the reaction environment during the extended dwell time required for HIBAm conversion, thereby preventing degradation losses.
2Ease of operation
If backmixing is allowed in conventional reactors, then mixing efficiency improves, but yield stability deteriorates due to varying dwell times and by-product formation
Solution Approach 1:
The harmful backmixing phenomenon is extracted and eliminated from the conversion reactor design. The patent employs plug flow reactor configurations that maintain unidirectional flow without recirculation or mixing zones, thereby removing the source of dwell time variation while still achieving adequate mixing through static mixers or injection designs that do not create backflow.
Solution Approach 2:
The reactor system incorporates dynamic flow control mechanisms that adapt to varying production rates. The plug flow characteristics are maintained across different operating conditions through adjustable flow distributors and dynamic mixing elements that ensure consistent dwell time distribution regardless of throughput variations.
3Speed
If sulfuric acid concentration is increased to accelerate conversion, then reaction rate improves, but selectivity deteriorates leading to increased by-product formation
Solution Approach 1:
Different sulfuric acid concentrations are applied locally to different conversion stages. The first conversion stage uses higher acid concentration (optimized for SIBA conversion), while the second stage uses lower acid concentration (optimized for HIBAm conversion). This local optimization of reaction conditions maximizes reaction rate in each stage while minimizing by-product formation through selective condition matching.
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 significantly enhances the overall yield of MMA or MA, reducing by-product formation and waste, while maintaining operational reliability and efficiency even at partial load conditions.
Implementation Method 1
HIBAm, SIBA, and MAA already formed in the amidation are subsequently converted thermally to MAA and relatively small amounts of MA in the reaction mixture in sulfuric acid
Implementation Method 2
In addition, optimization can be achieved with the aid of cooling of the reaction mixture which is effected between conversion and esterification
Data Source
AI summary
A process for preparing methyl methacrylate (MMA) and/or methacrylic acid (MAS) having improved yield, involves amidation, conversion, and hydrolysis/esterification. Especially high yields are obtained during the amidation and in the subsequent so-called conversion.