Extractive Distillation of Phenol and Cyclohexanone Using Diol Solvents
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Solution Overview
Problem
The production of phenol via the cyclohexylbenzene route faces challenges due to the formation of an azeotropic mixture with cyclohexanone, requiring alternative separation methods like extractive distillation, where solvents such as diols and glycols can react with cyclohexanone to form hemiketals and enol-ethers, affecting separation efficiency.
Innovation Solution
The use of diols and glycols with non-adjacent hydroxyl groups as solvents in extractive distillation processes to separate phenol and cyclohexanone, where hemiketals and enol-ethers are formed, allowing for effective separation by altering the relative volatilities of the components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If extractive distillation is used to separate phenol and cyclohexanone, then separation efficiency is improved, but solvents react with cyclohexanone to form hemiketals and enol-ethers causing side reactions
Solution Approach 1:
The patent introduces a specific solvent (ethylene glycol) as an intermediary that mediates the separation process. The solvent forms hemiketals and enol-ethers with cyclohexanone, which are then separated through distillation. This intermediary approach enables effective separation while managing the side reactions through controlled conditions and subsequent hydrolysis steps.
Solution Approach 2:
The patent utilizes parameter changes by controlling temperature, pressure, and solvent-to-feed ratio during extractive distillation. By adjusting these parameters, the relative volatility between phenol and cyclohexanone is modified, enabling separation. The parameters are optimized to minimize unwanted side reactions while maintaining separation efficiency.
2Device complexity
If simple distillation is used to separate phenol and cyclohexanone, then process complexity is reduced, but separation purity is insufficient due to azeotropic mixture
Solution Approach 1:
The patent employs an extractive distillation process where a solvent acts as an intermediary to break the azeotropic mixture. The solvent selectively interacts with one component (cyclohexanone), altering the relative volatilities and enabling separation that simple distillation cannot achieve. This approach maintains reasonable process complexity while significantly improving separation purity.
3Productivity
If diols and glycols are used as solvents in extractive distillation, then separation effectiveness is improved, but hemiketal and enol-ether formation affects separation efficiency
Solution Approach 1:
The patent performs preliminary action by pre-mixing the solvent with the phenol-cyclohexanone mixture before distillation. This allows the solvent to interact with cyclohexanone and form hemiketals/enol-ethers under controlled conditions, facilitating subsequent separation. The preliminary mixing optimizes the separation effectiveness while minimizing cyclohexanone loss through controlled reaction conditions.
Solution Approach 2:
The patent converts the harmful side reaction (hemiketal and enol-ether formation) into a beneficial separation mechanism. By allowing controlled reaction between the solvent and cyclohexanone, the process creates distinct chemical species with different volatilities, enabling effective separation. The reaction products are then hydrolyzed to recover cyclohexanone, converting what was initially a loss into a separable and recoverable form.
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 enables the efficient separation of phenol and cyclohexanone, avoiding undesirable side reactions and improving the purity of both products, with the solvent being recycled to maintain process efficiency.
Implementation Method 1
solvents such as diols and glycols can react with cyclohexanone to form hemiketals and enol-ethers
Implementation Method 2
solvents such as diols and glycols can react with cyclohexanone to form hemiketals and enol-ethers
Implementation Method 3
extractive distillation process for separating a mixture of phenol and cyclohexanone
Data Source
AI summary
In a process for separating a mixture comprising cyclohexanone and phenol, at least a portion of the mixture is distilled in the presence of a solvent including at least two alcoholic hydroxyl groups attached to non-adjacent saturated carbon atoms and at least one hemiketal defined by the formula (I) or the formula (II):wherein R1, the same or different at each occurrence, is independently an alkylene group having from 2 to 10 carbon atoms, R2 is an alkylene group having from 4 to 10 carbon atoms, and R3 is hydrogen or the following group:and/or an enol-ether derived from the hemiketal defined by the formula (I) or the formula (II), wherein the total concentration of the hemiketal and the enol-ether, expressed in terms of weight percentage on the basis of the total weight of the feed to the distilling step (a), is at least 0.01%.