1,2-Propanediol Preparation With Sulfate-Assisted Catalyst Retention
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Solution Overview
Problem
Existing methods for producing 1,2-propanediol suffer from significant losses of phase transfer catalyst and tungstate due to hydrolysis and oxidation, leading to the need for continuous replenishment, which affects process efficiency and stability.
Innovation Solution
A method involving the use of a quaternary ammonium salt as a phase transfer catalyst combined with sodium sulfate addition to improve phase separation, reducing catalyst and tungstate loss by recycling the organic phase and maintaining optimal reaction conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If quaternary ammonium ester salts or tertiary amines are used as phase transfer catalyst, then phase transfer catalysis is achieved, but hydrolysis or oxidation occurs leading to catalyst loss and water solubility increase
Solution Approach 1:
The patent changes the chemical structure parameters of the phase transfer catalyst from quaternary ammonium ester salts or tertiary amines to quaternary ammonium salts with specific hydrophobic groups (alkyl chains C12-C20, aryl groups, or alkylaromatic groups). This structural modification reduces water solubility and resistance to hydrolysis and oxidation, thereby reducing catalyst loss during continuous operation.
2Reliability
If quaternary ammonium salt is used as phase transfer catalyst, then catalyst stability improves, but phase separation becomes poor with emulsified droplets forming
Solution Approach 1:
The patent optimizes the hydrophobicity parameters of the quaternary ammonium salt by selecting specific R groups (alkyl chains C12-C20, aryl groups, or alkylaromatic groups) to achieve optimal phase separation. The balanced hydrophobic character prevents emulsification while maintaining catalyst stability and activity.
3Productivity
If extended continuous operation is performed, then production volume increases, but catalyst and tungstate losses accumulate requiring replenishment
Solution Approach 1:
The patent modifies the chemical composition parameters of the phase transfer catalyst to quaternary ammonium salts with enhanced stability against hydrolysis and oxidation. This allows extended continuous operation without significant catalyst degradation or loss, eliminating the need for permanent replenishment and maintaining constant catalytic activity over time.
4Ease of manufacture
If aqueous phase is separated, then product isolation is achieved, but substantial amounts of catalyst and tungstate are lost with the aqueous phase
Solution Approach 1:
The patent changes the solubility parameters of the phase transfer catalyst by using quaternary ammonium salts with hydrophobic R groups (C12-C20 alkyl chains, aryl groups, or alkylaromatic groups). This ensures the catalyst remains predominantly in the organic phase during separation, minimizing losses with the aqueous phase while maintaining effective product isolation.
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 method enables continuous operation with minimal loss of phase transfer catalyst and tungstate, enhancing process stability and efficiency by improving phase separation and catalyst recovery.
Implementation Method 1
reacting propene with hydrogen peroxide in the presence of a catalyst mixture comprising a quaternary ammonium salt and a polytungstophosphate in a liquid reaction mixture comprising an aqueous phase and an organic phase
Implementation Method 2
adding sodium sulfate to the aqueous phase of the resulting reaction mixture, which improves phase separation and reduces loss of phase transfer catalyst and tungstate with the separated aqueous phase
Implementation Method 3
reacting propene with hydrogen peroxide in the presence of a catalyst mixture comprising a quaternary ammonium salt and a polytungstophosphate
Implementation Method 4
reacting propene with hydrogen peroxide
Implementation Method 5
separating the mixture obtained in step b) into an aqueous phase and an organic phase containing propylene oxide, returning the propylene oxide contained in the separated organic phase into the reaction from step a)
Data Source
AI summary
A method for preparing 1,2-propanediol involves continuously reacting propene with hydrogen peroxide in the presence of a catalyst mixture, containing a quaternary ammonium salt and a polytungstophosphate, in a liquid reaction mixture containing an aqueous phase with a maximum apparent pH of 6 and an organic phase containing an alkylaromatic hydrocarbon solvent. The method then involves withdrawing the liquid reaction mixture from the reaction and adding a water-soluble sulfate salt or sulfuric acid to provide a mixture containing from 500 to 10,000 mg/kg of sulfate ions in the aqueous phase. The method further involves separating the mixture obtained into an aqueous phase (Pa) containing 1,2-propanediol and an organic phase (Po), recycling at least a part of the organic phase (Po) to the reaction, and recovering 1,2-propanediol from the aqueous phase (Pa). The method allows for extended operation of the reaction with little loss of tungsten and phase transfer catalyst.