2,6-Dimethylnaphthalene Purification via Melt Crystallization
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Solution Overview
Problem
Current methods for separating and purifying 2,6-dimethylnaphthalene (2,6-DMN) face challenges in achieving high yield and purity due to the close boiling points of DMN isomers and the complexity and cost of solvent-based crystallization processes.
Innovation Solution
A method combining distillation, liquid state isomerization using a hydrogen-ion-exchanged zeolite beta catalyst, and a two-step crystallization process involving melting and solution crystallization to separate and purify 2,6-DMN, optimizing conditions such as temperature, pressure, and solvent usage to enhance separation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solvent-based crystallization process is used to separate 2,6-DMN, then purity can be improved, but device complexity and production cost increase
Solution Approach 1:
The patent extracts and removes the solvent from the crystallization process, achieving purification through melt crystallization alone. This eliminates the complexity associated with solvent handling, recovery, and contamination while maintaining high purity of 2,6-DMN product.
Solution Approach 2:
The patent eliminates the need for expensive solvents and complex crystallization equipment by using simple melt crystallization. The process uses only the product material itself as the 'solvent' (molten state), dramatically reducing equipment requirements and operational complexity.
2Manufacturing precision
If conventional crystallization process is used to purify 2,6-DMN, then purity can be achieved, but energy consumption and production cost increase
Solution Approach 1:
The patent changes the physical state parameter from solid-to-liquid-to-solid (conventional crystallization) to liquid-to-solid (melt crystallization). This parameter change eliminates the energy-intensive solvent evaporation and heating steps, significantly reducing overall energy consumption while achieving the same purification effect.
Solution Approach 2:
By eliminating the need for solvents and complex heating systems, the melt crystallization process dramatically reduces energy consumption. The process uses the product's own melting point as the separation criterion, avoiding the energy costs associated with solvent recovery and high-temperature processing.
3Manufacturing precision
If distillation is used to separate DMN isomers, then separation can be achieved, but energy consumption increases due to close boiling points
Solution Approach 1:
The patent changes the separation parameter from boiling point (distillation) to melting point (crystallization). Since 2,6-DMN has a distinct melting point compared to other DMN isomers, this parameter change enables effective separation without the high energy consumption associated with distilling components with close boiling points.
Solution Approach 2:
The patent utilizes the phase transition from liquid to solid during cooling to achieve separation. By controlling the temperature to just below the melting point of 2,6-DMN, the desired isomer crystallizes out of the liquid mixture, providing an energy-efficient separation method that avoids the continuous heating required for distillation.
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 efficient separation and purification of high-purity 2,6-DMN with a high yield, reducing energy consumption and production costs while simplifying the process, making it industrially viable.
Implementation Method 1
liquid state isomerization using a hydrogen-ion-exchanged zeolite beta catalyst
Implementation Method 2
subjecting the dimethylnaphthalene isomer mixture to separation, using a distillation column
Implementation Method 3
a first crystallization step of cooling the product of liquid state isomerization with a refrigerant without a solvent to form crystals
Data Source
Figure 1
AI summary
The present invention relates to a method for preparation, separation and purification of high-purity 2,6-dimethylnaphthalene. The method according to the present invention comprises a step of subjecting a dimethylnaphthalene isomer mixture rich in 1,5-dimethylnaphthalene, high boiling point materials, unreacted 1,5-dimethyltetralin, and low boiling point materials, which are produced from a dehydrogenation reaction of 1,5-dimethyltetralin, to separation, using a distillation column; a step of subjecting the dimethylnaphthalene mixture separated by the distillation column to liquid state isomerization in the presence of an isomerization catalyst; a first crystallization step (melt crystallization process) of cooling the product of liquid state isomerization with a refrigerant without a solvent to form crystals; and a second crystallization step (solution crystallization process) of mixing the product of the first crystallization step with a solvent to form crystals.