1,4-Cyclohexanedimethanol Process Using Recycled (4-Methylcyclohexyl)methanol
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing process for producing 1,4-cyclohexanedimethanol from dimethyl terephthalate is inefficient due to high energy consumption, equipment costs, and purification challenges, including the formation of solids that reduce heat exchange efficiency and the need for additional purification steps to remove methanol and esterification catalysts.
Innovation Solution
A process involving the esterification of terephthalic acid with (4-methylcyclohexyl)methanol to form bis(4-methylcyclohexyl)methyl) terephthalate, followed by hydrogenation to produce 1,4-cyclohexanedimethanol, where the by-product (4-methylcyclohexyl)methanol is recycled, reducing the introduction of new impurities and simplifying purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dimethyl terephthalate is used as starting material for CHDM preparation, then the hydrogenation process can proceed, but high energy consumption and expensive specialized equipment are required for the esterification step
Solution Approach 1:
The invention changes the esterification parameters by using (4-methylcyclohexyl)methanol instead of methanol, and conducting esterification at lower temperatures (100-200°C) compared to conventional high-temperature processes, thereby reducing energy consumption while maintaining production efficiency
Solution Approach 2:
The invention uses readily available terephthalic acid and (4-methylcyclohexyl)methanol as starting materials, avoiding the need for expensive dimethyl terephthalate, thus reducing both equipment costs and energy requirements for the overall process
2Productivity
If dimethyl terephthalate is prepared by esterification of terephthalic acid with methanol, then CHDM can be produced, but solids form in the reflux zone causing plugging and reducing heat exchange efficiency
Solution Approach 1:
The invention converts the potential harm of solid formation into a benefit by using (4-methylcyclohexyl)methanol as the alcohol reactant, which produces (4-methylcyclohexyl)methyl terephthalate that remains liquid under reaction conditions, eliminating plugging problems while maintaining high productivity
Solution Approach 2:
By changing the chemical structure of the alcohol from methanol to (4-methylcyclohowyl)methanol, the invention alters the physical properties of the esterification product, preventing solid formation and heat exchange surface plugging
3Reliability
If DMT is distilled prior to hydrogenation to remove partial esterification products and catalysts, then catalyst poisoning is avoided, but additional purification equipment and processing steps are required
Solution Approach 1:
The invention extracts the need for complex purification steps by using (4-methylcyclohowyl)methanol as the alcohol reactant, which does not form problematic by-products that require distillation removal, thereby simplifying the overall process while maintaining catalyst reliability
Solution Approach 2:
The invention eliminates expensive distillation equipment and complex purification steps by choosing alternative reactants that naturally avoid catalyst poisoning issues, reducing both device complexity and capital investment
4Productivity
If methanol is released during hydrogenation of DMT, then CHDM is produced, but additional purification and processing steps are required to recover and recycle methanol
Solution Approach 1:
The invention implements self-service by using (4-methylcyclohowyl)methanol as both the esterification reactant and the hydrogenation by-product, which automatically recycles back into the esterification step, eliminating the need for separate methanol recovery and recycling systems
Solution Approach 2:
The invention merges the esterification and hydrogenation cycles by using (4-methylcyclohowyl)methanol as the connecting link, where the by-product of hydrogenation becomes the reactant for esterification, creating an integrated process that eliminates separate purification equipment
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 process reduces equipment needs, energy consumption, and purification complexity, improving the efficiency and cost-effectiveness of 1,4-cyclohexanedimethanol production by utilizing recycled by-products and avoiding the formation of new impurities.
Implementation Method 1
contacting terephthalic acid and (4-methylcyclohexyl)methanol in a mole ratio of alcohol to acid of at least 2:1, in a reaction zone at a temperature of about 200°C to about 300°C under superatmospheric pressure, while removing water from the reaction zone, to form an esterification product mixture
Implementation Method 2
contacting the esterification product mixture with hydrogen in a first hydrogenation zone in the presence of a catalyst effective for hydrogenation of an aromatic ring to produce a liquid effluent comprising bis(4-methylcyclohowyl)methyl) cyclohexane-1,4-dicarboxylate
Implementation Method 3
contacting the effluent from the first hydrogenation zone with hydrogen in the presence of an ester hydrogenation catalyst in a second hydrogenation zone to produce a hydrogenation product comprising 1,4-cyclohexanedimethanol
Data Source
AI summary
Disclosed is a process for the preparation of 1,4-cyclohexanedimethanol from terephthalic acid. Terephthalic acid is esterified with (4-methylcyclohexyl)methanol and the terephthalate ester hydrogenated to 1,4-cyclohexanedimethanol in a 2-stage process. The (4-methylcyclohexyl)methanol that is formed during the hydrogenation step is recycled to the esterification reaction. Also disclosed is a method for purifying and recovering the 1,4-cyclohexanedimethanol product.