1,2-Propanediol Recovery via Alkaline Aqueous-Phase Distillation

Solution Overview

Problem

The existing methods for producing 1,2-propanediol result in the accumulation of formic acid and acetic acid in the reaction mixture, complicating the purification process and making it difficult to separate valuable products like dipropylene glycol and tripropylene glycol.

Innovation Solution

Adjusting the apparent pH of the separated aqueous phase to a value of at least 9 prior to distillation, followed by hydrogenation to convert unwanted by-products, simplifies the purification process and reduces the content of formic acid and acetic acid in the 1,2-propanediol fraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If propene is reacted with hydrogen peroxide using the HPPO process, then 1,2-propanediol is produced efficiently, but formic acid and acetic acid accumulate in the reaction mixture complicating purification

Engineering Contradiction:

Improveproduction efficiency of 1,2-propanediolVSAvoidpurification process complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by adjusting the pH of the aqueous phase to at least 9 before the distillation step. This pre-treatment converts formic acid and acetic acid into their salt forms (formates and acetates), which have different volatility characteristics, thereby simplifying the subsequent purification process and enabling efficient separation of 1,2-propanediol from these byproducts

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent utilizes parameter changes by modifying the pH parameter of the aqueous phase from its initial value (≤6) to at least 9. This chemical parameter change transforms the state of formic acid and acetic acid, converting them into salts that can be more easily separated during distillation, thus resolving the purification complexity while maintaining high productivity

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If formic acid and acetic acid are present in the aqueous phase, then they accumulate during distillation, but this makes it difficult to separate valuable products like dipropylene glycol and tripropylene glycol

Engineering Contradiction:

Improveyield of valuable productsVSAvoidpurification quality

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by adjusting the pH of the aqueous phase to at least 9 before the distillation step. This pre-treatment converts formic acid and acetic acid into their salt forms (formates and acetates), which have different volatility characteristics, thereby simplifying the subsequent purification process and enabling efficient separation of 1,2-propanediol from these byproducts

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent utilizes parameter changes by modifying the pH parameter of the aqueous phase from its initial value (≤6) to at least 9. This chemical parameter change transforms the state of formic acid and acetic acid, converting them into salts that can be more easily separated during distillation, thus resolving the purification complexity while maintaining high productivity

Inventive Principle:

Principle #35Parameter changes

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 allows for the efficient recovery of high-purity 1,2-propanediol with reduced levels of formic acid and acetic acid, thereby simplifying the purification process and improving the yield of valuable products.

Implementation Method 1

adjusting the apparent pH of the separated aqueous phase to a value of at least 9 prior to recovering 1,2-propanediol by distillation

Methodology Applied

Scientific EffectpH adjustment:

Implementation Method 2

recovering 1,2-propanediol and dipropylene glycol from the separated aqueous phase (Pa) wherein in step d) 1,2-propanediol is separated from the aqueous phase (Pa) by distillation

Methodology Applied

Scientific EffectDistillation: Distillation

Implementation Method 3

reacting propene with hydrogen peroxide in the presence of a catalyst mixture comprising a phase transfer catalyst and a heteropolytungstate

Methodology Applied

Scientific EffectPhase transfer catalysis:

Implementation Method 4

reacting propene with hydrogen peroxide in the presence of a catalyst mixture comprising a phase transfer catalyst and a heteropolytungstate

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS12479783B2Method for the preparation of 1,2-propanediol

Publication Date: 2025.11.25 EVONIK OPERATIONS GMBH

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 process then involves separating the reaction mixture into an aqueous phase (Pa) containing 1,2-propanediol and an organic phase (Po); recycling at least part of the separated organic phase (Po) to the reaction; and recovering 1,2 propanediol from the separated aqueous phase (Pa). In the recovery, 1,2-propanediol is separated from the aqueous phase (Pa) by distillation and the apparent pH of the separated aqueous phase (Pa) is adjusted to at least 9 prior to the distillation to reduce the content of formic acid and acetic acid in the recovered 1,2-propanediol.