1,2-Propanediol Catalysis with Pre-Formed Polytungstophosphate
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Solution Overview
Problem
The catalytic activity of the catalyst mixture used in the production of 1,2-propanediol deteriorates over time when the phosphoric acid concentration in the aqueous phase is low, leading to reduced efficiency in the oxidation of propene.
Innovation Solution
A separate step of reacting tungstate with hydrogen peroxide and phosphoric acid in the presence of a phase transfer catalyst forms a peroxopolytungstophosphate, which is then introduced into the reaction mixture to maintain high catalytic activity, even at low phosphoric acid concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a low phosphoric acid concentration is used in the aqueous phase, then the process is more economical and environmentally friendly, but the catalytic activity deteriorates over time
Solution Approach 1:
The patent applies preliminary action by pre-forming the peroxopolytungstophosphate catalyst in a separate activation step before the main propene oxidation reaction. This pre-formed catalyst is then introduced into the reaction system, allowing the main reaction to proceed with high catalytic activity even at low phosphoric acid concentrations. The preliminary catalyst preparation eliminates the need for high phosphoric acid concentrations during the main reaction process.
2Reliability
If a high phosphoric acid concentration is used in the aqueous phase, then the catalytic activity is maintained, but the process becomes less economical and more environmentally harmful
Solution Approach 1:
The patent segments the catalyst formation and reaction processes into two distinct stages: (1) catalyst activation step where peroxopolytungstophosphate is formed from tungstate, hydrogen peroxide, and phosphoric acid, and (2) main oxidation reaction step where the pre-formed catalyst is used. This segmentation allows phosphoric acid to be consumed primarily in the catalyst formation step, enabling the main reaction to proceed with low phosphoric acid concentration while maintaining high catalytic activity.
3Productivity
If the catalytic activity deteriorates over time, then the reaction efficiency decreases, but increasing phosphoric acid concentration to maintain activity increases process complexity and cost
Solution Approach 1:
The patent ensures continuity of useful action by implementing a catalyst regeneration system where the peroxopolytungstophosphate catalyst is continuously regenerated in situ during the reaction process. Hydrogen peroxide continuously reacts with tungstate species to replenish the active catalyst, maintaining sustained catalytic activity without requiring frequent catalyst replacement or process interruption, thereby maintaining high productivity with simple continuous operation.
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 maintains sustained catalytic activity and improves the conversion of hydrogen peroxide, resulting in higher yields of 1,2-propanediol over extended periods.
Implementation Method 1
reacting propene with hydrogen peroxide in the presence of a catalyst mixture comprising a phase transfer catalyst and a polytungstophosphate
Implementation Method 2
reacting propene with hydrogen peroxide in the presence of a catalyst mixture comprising a phase transfer catalyst and a polytungstophosphate
Implementation Method 3
separating the reaction mixture into an aqueous phase (Pa) comprising 1,2-propanediol and an organic phase (Po)
Data Source
AI summary
1,2-propanediol is prepared by a method involving reacting propene with hydrogen peroxide at 50 to 110° C. in the presence of a catalyst mixture, containing a phase transfer catalyst and a polytungstophosphate, 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 containing 1,2-propanediol and an organic phase; recycling at least part of the separated organic phase to the reaction; and recovering 1,2 propanediol from the aqueous phase. The method further involves reacting a tungstate with hydrogen peroxide and phosphoric acid at 5 to 40° C., in the presence of the phase transfer catalyst, in a liquid mixture containing an aqueous and an organic phase, followed by passing at least a part of the resulting organic phase containing the polytungstophosphate and phase transfer catalyst to the initial reaction.