Liquid Phase Hydrogenation for 1,2-Propanediol Purity
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Solution Overview
Problem
Vapour phase hydrogenation processes for converting glycerol to 1,2-propanediol suffer from impurities like hydroxypropanone and 2,4-dimethyl-2-methanol-1,3-dioxolanes, which are difficult to separate from the desired product using conventional distillation due to similar boiling points and reactive nature, leading to impurities formation during purification.
Innovation Solution
Passing the crude vapour phase hydrogenation product stream over a liquid phase hydrogenation using a heterogeneous catalyst under suitable conditions to convert hydroxypropanone and reduce 2,4-dimethyl-2-methanol-1,3-dioxolanes to low ppm levels, allowing high-purity 1,2-propanediol production through conventional distillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional distillation is used to separate hydroxypropanone from 1,2-propanediol, then separation is attempted, but impurities are formed due to similar boiling points and reactive nature of the compounds
Solution Approach 1:
The patent applies preliminary action by performing hydrogenation of hydroxypropanone to 1,2-propanediol before the distillation separation step. This converts the problematic intermediate (hydroxypropanone) into the desired product, eliminating the source of impurity formation during subsequent distillation and enabling high-purity product recovery
Solution Approach 2:
The patent converts the harmful reactive nature of hydroxypropanone into a benefit by utilizing its hydrogenation to 1,2-propanediol. Instead of attempting to separate the reactive intermediate, the process transforms it into the stable desired product, thereby eliminating impurity formation while maintaining high manufacturing precision
2Productivity
If vapour phase hydrogenation is used to convert glycerol to 1,2-propanediol, then reaction rate and selectivity are improved, but impurities like hydroxypropanone and dioxolanes are formed that are difficult to separate
Solution Approach 1:
The patent performs a second hydrogenation step on the crude vapour phase product to convert remaining hydroxypropanone intermediate into 1,2-propanediol before distillation. This preliminary conversion action ensures that the feedstock for distillation contains minimal impurities, enabling high-purity product recovery while maintaining the high reaction rate benefits of vapour phase hydrogenation
Solution Approach 2:
The patent maintains continuity of useful action by implementing a sequential process where vapour phase hydrogenation is followed by liquid phase hydrogenation of the crude product. This continuous treatment ensures complete conversion of intermediates to desired product, eliminating impurities while preserving the high productivity achieved in the first hydrogenation step
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 process effectively reduces hydroxypropanone and its reaction products to near zero levels, enabling the production of high-purity 1,2-propanediol, suitable for pharmaceutical grades, by preventing unwanted compound formation during distillation.
Implementation Method 1
contacting the crude product phase in the liquid phase with a stream of a hydrogen-containing gas in the presence of a heterogeneous catalyst at suitable temperatures and pressures such that hydroxypropanone present in the crude product stream is converted to the desired propanediol
Implementation Method 2
contacting the crude product phase in the liquid phase with a stream of a hydrogen-containing gas in the presence of a heterogeneous catalyst
Implementation Method 3
condensing the crude product stream
Data Source
AI summary
A process for the removal of hydroxypropane from a crude product stream from the hydrogenation of glycerol, the crude product stream comprising 1,2-propanediol and hydroxypropanone as impurity, the process comprising: (a) where required condensing the crude product stream; and (b) contacting the crude product phase in the liquid phase with a stream of a hydrogen-containing gas in the presence of a heterogeneous catalyst at suitable temperatures and pressures such that hydroxypropanone present in the crude product stream is converted to the desired propanediol.