1,2-Propanediol Preparation Through Phosphate Ester Hydrolysis
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Solution Overview
Problem
The existing method for producing 1,2-propanediol forms phosphoric acid esters of 1,2-propanediol as side products, which reduces the selectivity and efficiency of the process.
Innovation Solution
A method involving the use of a catalyst mixture comprising a phase transfer catalyst, phosphoric acid, and a heteropolytungstate, with a controlled pH and temperature conditions, followed by heating the aqueous phase to convert phosphoric acid esters of 1,2-propanediol into 1,2-propanediol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If propene is reacted with hydrogen peroxide in the presence of phosphoric acid, then the epoxidation reaction proceeds efficiently, but phosphoric acid esters of 1,2-propanediol are formed as side products reducing selectivity
Solution Approach 1:
The process is divided into two distinct stages: first the epoxidation reaction to form propylene oxide, then a separate hydrolysis step to convert phosphoric acid esters to 1,2-propanediol. This segmentation allows each stage to be optimized independently, maintaining high reaction efficiency while improving product selectivity through the dedicated hydrolysis treatment.
Solution Approach 2:
The phosphoric acid esters, which are harmful side products reducing selectivity, are converted into beneficial 1,2-propanediol through the hydrolysis step. The harmful by-product is transformed into the desired product, thereby converting a negative effect into a positive outcome and improving overall process selectivity.
2Device complexity
If phosphoric acid esters are not converted, then the process is simpler, but the yield and selectivity of 1,2-propanediol are reduced
Solution Approach 1:
The hydrolysis step is performed as a preliminary treatment on the aqueous phase before final product isolation. By converting phosphoric acid esters to 1,2-propanediol in advance, the process ensures high yield and selectivity are achieved before the complexity of product separation and purification begins.
Solution Approach 2:
The hydrolysis step utilizes specific parameter changes (temperature, pH, reaction time) to selectively convert phosphoric acid esters to 1,2-propanediol. By controlling these parameters, the process achieves high conversion efficiency while managing the added complexity through systematic parameter optimization.
3Manufacturing precision
If the aqueous phase is heated to convert phosphoric acid esters, then selectivity improves, but energy consumption increases
Solution Approach 1:
The heating and hydrolysis treatment is applied locally only to the aqueous phase containing phosphoric acid esters, rather than heating the entire reaction mixture. This localized treatment reduces energy consumption while maintaining high selectivity improvement, as only the necessary portion of the system receives thermal energy.
Solution Approach 2:
Instead of completely processing all phases or using excessive heating, the method applies partial action by treating only the aqueous phase with controlled heating sufficient to achieve hydrolysis. This partial treatment optimizes the balance between energy input and selectivity improvement, avoiding unnecessary energy expenditure.
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
Improves the selectivity and yield of 1,2-propanediol by effectively converting phosphoric acid esters into the desired product, enhancing the overall process efficiency.
Implementation Method 1
heating all or a part of the aqueous phase separated from the oxidation reaction mixture to a temperature of more than 140° C. at a pressure sufficient to maintain a substantial part of the water as a liquid phase, which hydrolyzes the phosphoric acid esters of 1,2-propanediol to give 1,2-propanediol
Data Source
AI summary
A method for preparing 1,2-propanediol involves reacting propene with hydrogen peroxide in the presence of a catalyst mixture, containing a phase transfer catalyst and a heteropolytungstate, in a liquid reaction mixture containing an aqueous phase with a maximum apparent pH of 6 and an organic phase. The method then involves separating the reaction mixture into an aqueous phase (Pa), containing 1,2-propanediol and phosphoric acid esters of 1,2-propanediol, and an organic phase (Po). The method further involves recycling at least part of the separated organic phase (Po) to the reaction; heating at least a part of the separated aqueous phase (Pa) to a temperature of more than 140° C. at a pressure sufficient to maintain at least part of the aqueous phase as a liquid; and recovering 1,2-propanediol from the heated aqueous phase. The heating cleaves phosphoric acid esters of 1,2-propanediol into 1,2-propanediol and phosphoric acid.