1,2-Propanediol Preparation With Partial Oxygen Desorption
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Solution Overview
Problem
The existing process for producing 1,2-propanediol from propene and hydrogen peroxide is hazardous due to the formation of a flammable gas phase containing oxygen, which poses an explosion risk, and requires additional steps to recover unreacted propene and propane.
Innovation Solution
The process is modified by operating steps a) and b) in vessels flooded by the liquid reaction mixture at high pressure to suppress gas desorption, using a catalyst mixture of phase transfer catalyst and heteropolytungstate, and desorbing only a portion of dissolved oxygen into a non-flammable gas, allowing for the recycling of the oxygen-depleted organic phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the process is operated at high pressure to suppress gas desorption in flooded vessels, then explosion risk is reduced, but propene loss increases due to desorption along with oxygen
Solution Approach 1:
The patent applies partial action by desorbing only a portion (10-75%) of the dissolved oxygen from the organic phase rather than complete desorption. This selective partial desorption removes sufficient oxygen to prevent flammable gas phase formation while minimizing co-desorption of propene to only a few percent of fed propene, thus resolving the contradiction between explosion risk reduction and propene loss prevention
Solution Approach 2:
The patent changes the pressure parameter during the process: operating at high pressure during reaction and separation steps a) and b) to suppress gas desorption and prevent explosion, then reducing pressure during step c) oxygen desorption to enable controlled oxygen removal. This dynamic parameter adjustment allows both explosion risk reduction and propene loss minimization at different process stages
2Loss of substance
If additional equipment is added for recovery of non-reacted propene, then propene loss is reduced, but device complexity increases
Solution Approach 1:
The patent converts the harmful effect of oxygen dissolution in the organic phase into a beneficial separation mechanism. By allowing controlled oxygen desorption into a non-flammable gas carrier, the process simultaneously removes oxygen (preventing explosions) and recovers propene (reducing loss) without requiring additional complex recovery equipment. The oxygen desorption step itself becomes the propene recovery mechanism
Solution Approach 2:
The organic phase serves dual functions: it extracts propene oxide from the aqueous phase and simultaneously acts as a carrier for oxygen removal. The system uses its own organic phase to perform the separation function that would otherwise require additional equipment, simplifying the overall process while maintaining propene recovery
3Quantity of substance
If chemical grade propene containing propane is used, then feedstock cost is reduced, but separation of propane and propene becomes necessary
Solution Approach 1:
The patent uses a non-flammable gas (inert atmosphere) to desorb oxygen from the organic phase. This inert gas environment allows propane to accumulate in the recycle stream without creating flammable mixtures, eliminating the need for propane-propene separation equipment while maintaining process safety. The inert gas acts as a safe carrier that tolerates propane presence
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 method reduces the risk of explosions and minimizes propene loss while efficiently converting propene to 1,2-propanediol, enriching propane in the recycle stream, and eliminating the need for additional recovery steps.
Implementation Method 1
carrying out steps a) and b) in vessels which are flooded by the liquid reaction mixture and applying a pressure high enough to suppress desorption of gas from the liquid reaction mixture
Implementation Method 2
desorbing only a part of the oxygen dissolved in the organic phase (P o ) needs to be desorbed to prevent formation of a flammable gas phase
Implementation Method 3
contacting the organic phase (P o ) separated in step b) with a stream of a non-flammable gas at a flow rate of non-flammable gas, a temperature and a pressure effecting desorption of from 10 to 75 % of the oxygen dissolved in the organic phase (P o ) into the stream of non-flammable gas
Data Source
AI summary
In a method for preparing 1,2-propanediol by the steps of reacting propene with hydrogen peroxide in the presence of a phase transfer catalyst and a heteropolytungstate in a liquid two phase reaction mixture with an organic phase comprising an alkylaromatic hydrocarbon solvent, separating the reaction mixture into an aqueous phase comprising 1,2-propanediol and an organic phase, recycling the oxygen depleted organic phase (Pd) to the reaction step, and recovering 1,2-propanediol from the aqueous phase, the reaction and separation steps are carried out in liquid flooded vessels at a pressure high enough to suppress desorption of gas from the liquid reaction mixture and the separated organic phase is contacted with a stream of a non-flammable gas to desorb from 10 to 75 % of the oxygen dissolved in the organic phase into the stream of non-flammable gas before recycling the organic phase, which purges oxygen safely with little loss of propene.