Diol Purification via Low-Temperature Vacuum Distillation
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Solution Overview
Problem
Diols produced by existing methods often have poor color quality and contain a high amount of unsaturated aliphatic hydrocarbons.
Innovation Solution
A method involving liquid-phase oxidation of saturated aliphatic hydrocarbons with molecular oxygen in the presence of metaboric acid, followed by esterification, distillation, hydrolysis, saponification, and multiple distillation steps to separate and purify the diols, ensuring a reduced unsaturated hydrocarbon content and improved color quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If distillation is performed at high temperature for extended time to separate diols from the reaction mixture, then separation efficiency is improved, but the color quality deteriorates and unsaturated hydrocarbon content increases
Solution Approach 1:
The patent applies parameter changes by optimizing distillation temperature and residence time parameters. Specifically, it uses reduced pressure distillation at temperatures below 250°C with residence times under 60 minutes, changing the thermal parameters to prevent degradation while maintaining separation efficiency. This resolves the contradiction by finding optimal parameter values that achieve both good separation and color quality.
Solution Approach 2:
The patent segments the purification process into multiple distinct distillation steps: first distillation to remove monoalcohols, then second distillation under controlled conditions to obtain high-purity diols. This segmentation allows each step to be optimized independently, with the first step removing lower-boiling impurities and the second step carefully separating diols without excessive thermal exposure, thus maintaining color quality while achieving separation efficiency.
2Productivity
If conventional distillation conditions are used to obtain diols, then production efficiency is maintained, but the diol quality deteriorates with poor color scale and high unsaturated hydrocarbon content
Solution Approach 1:
The patent changes the distillation parameters from conventional high-temperature, long-duration conditions to reduced pressure conditions with temperature below 250°C and residence time under 60 minutes. This parameter optimization maintains production efficiency by preventing side reactions and material degradation, while simultaneously improving diol quality through better color scale and reduced unsaturated hydrocarbon content.
Solution Approach 2:
The patent introduces reduced pressure as an intermediary condition that enables effective separation at lower temperatures. By operating under vacuum conditions, the boiling points of the components are reduced, allowing efficient distillation without the high temperatures that cause color degradation and unsaturated hydrocarbon formation, thus maintaining both productivity and quality.
3Quantity of substance
If oxidation reaction is performed to produce secondary alcohols and diols, then useful chemical products are obtained, but unsaturated aliphatic hydrocarbons are generated as unwanted byproducts
Solution Approach 1:
The patent converts the harmful effect of high-temperature distillation that generates unsaturated hydrocarbons into a benefit by using reduced pressure distillation. This alternative approach achieves the same separation objective without the harmful thermal effects, eliminating the formation of unsaturated hydrocarbons while maintaining diol yield. The harmful high-temperature condition is replaced with a beneficial low-temperature vacuum process.
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 method effectively produces diols with a favorable color scale and minimized unsaturated aliphatic hydrocarbon content, enhancing their quality.
Implementation Method 1
subjecting the saturated aliphatic hydrocarbon to liquid-phase oxidation with the reaction gas containing molecular oxygen in the presence of metaboric acid to obtain a reaction liquid containing an oxide
Implementation Method 2
esterifying the oxide to obtain a reaction liquid containing a borate compound
Implementation Method 3
distilling the reaction liquid containing a borate compound to separate the reaction liquid into an unreacted saturated aliphatic hydrocarbon and a distillation residue
Implementation Method 4
hydrolyzing the distillation residue to separate it into orthoboric acid and an organic layer
Implementation Method 5
subjecting the organic layer to saponification with an alkali to separate into an alkali aqueous solution layer and a crude alcohol layer
Implementation Method 6
performing first distillation on the crude alcohol layer to remove a monoalcohol therefrom
Implementation Method 7
performing second distillation on the residual liquid under conditions of a temperature of lower than 250° C. and a residence time of shorter than 60 minutes
Data Source
AI summary
[Objective] An object is to provide a method for producing a diol by which diols having a favorable color scale and containing a reduced amount of an unsaturated aliphatic hydrocarbon can be produced.[Solution] A method for producing a diol, including a) supplying metaboric acid, a saturated aliphatic hydrocarbon and a reaction gas containing molecular oxygen to a reactor and performing liquid-phase oxidation of the saturated aliphatic hydrocarbon with the reaction gas containing molecular oxygen in the presence of metaboric acid to obtain a reaction liquid containing an oxide, b) esterifying the oxide to obtain a reaction liquid containing a borate compound, c) separating the reaction liquid containing a borate compound into an unreacted saturated aliphatic hydrocarbon and a distillation residue by distillation, d) separating the distillation residue into orthoboric acid and an organic layer by hydrolysis, e) separating the organic layer into an alkali aqueous solution layer and a crude alcohol layer by saponification with an alkali, and f) performing first distillation on the crude alcohol layer to remove a monoalcohol, and then performing second distillation on the residual liquid under conditions of a temperature of lower than 250° C. and a residence time of shorter than 60 minutes.