Dialkyl Terephthalate Ring Hydrogenation With Two-Stage Conversion Control
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Solution Overview
Problem
Existing ring hydrogenation processes for dialkyl terephthalates are economically less efficient and produce more by-products compared to dialkyl phthalates, making them less attractive for industrial use.
Innovation Solution
A two-stage hydrogenation process is employed, where the first reaction unit is controlled to limit conversion to 85-93%, using a heterogeneous catalyst with specific parameters, and the second unit operates in straight pass mode to achieve a total conversion of >99.7% with <1.3% by-products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ring hydrogenation of dialkyl terephthalates is performed using conventional single-stage processes, then the reaction proceeds to completion, but by-product formation increases and production efficiency decreases
Solution Approach 1:
The hydrogenation process is divided into two distinct reaction units: a first reaction unit that performs partial hydrogenation (85-93% conversion) to minimize by-products, and a second reaction unit that completes the hydrogenation to >99.7% conversion. This segmentation allows each unit to operate under optimized conditions for its specific function, resolving the contradiction between purity and efficiency.
Solution Approach 2:
The first reaction unit deliberately operates at partial conversion (85-93%) rather than complete conversion, which minimizes by-product formation. The second reaction unit then provides the remaining conversion to achieve overall >99.7% conversion. This partial action approach in the first stage resolves the contradiction by preventing excessive reaction that would generate by-products.
2Productivity
If ring hydrogenation of dialkyl terephthalates is performed to achieve high conversion, then total conversion exceeds 99.7%, but by-product formation increases to over 1.3%
Solution Approach 1:
The process segments the hydrogenation into two stages: first achieving 85-93% conversion in a controlled environment that minimizes by-products, then completing the conversion in a second unit. This segmentation prevents the harmful effect of by-product formation that would occur in a single-stage high-conversion process.
Solution Approach 2:
The patent converts the potential harm of high conversion (by-product formation) into a benefit by using the first reaction unit to achieve controlled partial conversion that actually reduces by-products, while the second unit completes the conversion. The 'harm' of requiring high conversion is transformed into a two-stage process that achieves high conversion with minimal by-products.
3Productivity
If conventional hydrogenation processes are used for dialkyl terephthalates, then the reaction is slower and less efficient, but implementing optimized processes requires precise control of multiple parameters
Solution Approach 1:
The process divides the hydrogenation into two reaction units with different operational modes: the first unit operates in recirculating mode with controlled conversion (85-93%), while the second unit operates in straight-pass mode for complete conversion. This segmentation simplifies control by giving each unit a specific, optimized function rather than requiring complex control for a single high-conversion process.
Solution Approach 2:
The patent optimizes specific parameters for each reaction unit: the first unit uses recirculating mode with controlled residence time and temperature to achieve 85-93% conversion, while the second unit uses straight-pass mode with adjusted parameters to achieve >99.7% conversion. These parameter changes resolve the contradiction by tailoring conditions to each stage's specific requirements.
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 significantly reduces by-products and increases production efficiency, allowing higher purity products to be produced with minimal additional purification, thus enhancing economic viability.
Implementation Method 1
Dialkyl 1,2- and 1,4-cydohexanedicarboxylates can be prepared by hydrogenation (hereinafter used synonymously with the term ring hydrogenation) of the aromatic ring of the corresponding phthalates or terephthalates
Implementation Method 2
a heterogeneous hydrogenation catalyst is present in the reactors of each of the two reaction units of the hydrogenation unit
Data Source
AI summary
A process for ring hydrogenation of dialkyl terephthalates having C3- to C16-alkyl groups can be performed in a hydrogenation unit composed of two reaction units in series. In the process, a suitable process parameter in relation to the first reaction unit is adjusted so that a certain reaction conversion is achieved.