CHDM Preparation via Two-Step Reduction and Isomerization
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Solution Overview
Problem
Current methods for preparing 1,4-cyclohexanedimethanol (CHDM) face challenges in achieving a high trans isomer rate, with existing processes being complex, costly, and inefficient, particularly due to issues with catalyst performance and crystallization in fixed bed reactors.
Innovation Solution
A method involving two-step reduction reactions using terephthalic acid as a starting material, with an isomerization process in between, employing specific hydrogenation and isomerization catalysts to stabilize and increase the trans isomer rate of CHDM, simplifying the process and maintaining reaction temperature to avoid heat energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed bed reactor is used for hydrogenation of phthalate, then the reaction can proceed continuously, but temperature control and gradient of phthalate and intermediate product CHDA are not constant, causing crystallization in the middle and deteriorating catalyst performance
Solution Approach 1:
The patent divides the reaction process into two separate batch hydrogenation steps instead of one continuous fixed bed reaction. The first step converts phthalate to CHDA, and the second step converts CHDA to CHDM. This segmentation allows better control of temperature and reactant gradients in each step, preventing crystallization and maintaining catalyst performance while still achieving continuous production through sequential batch operations.
2Productivity
If trans esterification reaction using methanol is used to prepare CHDM from DMT, then CHDM can be produced, but reaction and separation processes are complicated and additives should be used for isomerization
Solution Approach 1:
The patent extracts and eliminates the trans esterification step using methanol from the traditional process. By starting directly with phthalate and using hydrogenation reactions, the process removes the complicated separation processes and isomerization additives that were required in the DMT-based route, while still achieving high CHDM production.
3Manufacturing precision
If Korean Registered Patent No. 0943872 method is used to produce trans CHDA separately, then trans CHDM rate can be increased, but process of removing water solvent is required and heat used in reduction process should be removed, making it not economical
Solution Approach 1:
The patent merges the isomerization process with the second hydrogenation step. Instead of separately producing trans CHDA and then removing water solvent and recovering heat, the process directly hydrogenates the CHDA mixture (containing both cis and trans isomers) to CHDM in the presence of a selective catalyst that favors trans CHDM formation. This integration eliminates the energy-intensive solvent removal and heat recovery steps while maintaining high trans CHDM selectivity.
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 allows for the stable preparation of CHDM with a high yield and high trans isomer rate, simplifying the process and reducing costs by eliminating the need for additional purification or separation steps.
Implementation Method 1
conducting a hydrogenation reaction of terephthalic acid in the presence of a first hydrogenation catalyst to prepare 1,4-cyclohexanedicarboxylic acid(CHDA)
Implementation Method 2
conducting an isomerization reaction of the reaction product of the step 1 in the presence of an isomerization catalyst to isomerizes at least a part of the cis isomers of CHDA into trans isomers
Implementation Method 3
conducting a hydrogenation reaction of the reaction product of the step 2 in the presence of a second hydrogenation catalyst to prepare 1, 4-cyclohexanedimethanol(CHDM)
Data Source
Figure 1~2
Figure 3
AI summary
The present disclosure relates to a method for preparation of 1,4-cyclohexanedimethanol. According to the present disclosure, two step reduction reactions are conducted using terephthalic acid as starting material, and an isomerization process for increasing the rate of trans isomers of CHDA is introduced therebetween, thereby providing a method capable of stably preparing CHDM with high rate of trans isomers.