TBHP Distillation for High Purity Epoxidation
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Solution Overview
Problem
Previous processes for forming tert-butyl hydroperoxide (TBHP) solutions in tert-butyl alcohol (TBA) suffer from yield-lowering impurities and inefficient TBHP loss in distillation overhead streams, leading to lower propylene oxide yields and operational risks due to exothermic reactions during epoxidation.
Innovation Solution
A distillation process that increases TBHP concentration to 65 wt% or higher with a reflux ratio of at least 2:1, reducing impurities to 0.4-1 wt%, followed by controlled introduction of the concentrated TBHP solution into an epoxidation reactor with a molybdenum catalyst for efficient propylene oxide production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If vacuum distillation process is used to increase TBHP concentration to 65 wt% or higher, then TBHP concentration is improved, but impurity levels increase and TBHP loss in overhead streams occurs
Solution Approach 1:
The distillation process is divided into multiple sequential stages: first a debutanizer removes light ends (isobutane, water, methanol, acetone), then a TBA stripper removes heavy ends (TBA, di-TBA ether, water). This segmentation allows each stage to target specific impurities, achieving high TBHP concentration (65 wt% or higher) while maintaining low impurity levels (less than 1 wt%), resolving the contradiction between concentration and purity.
2Productivity
If TBHP concentration is increased to 65 wt% or higher, then epoxidation efficiency is improved, but operational risks increase due to highly exothermic reactions
Solution Approach 1:
The patent performs preliminary purification actions before the epoxidation reaction by removing light ends in the debutanizer and heavy ends in the TBA stripper. This preliminary removal of impurities that could cause unwanted side reactions or safety issues enables the subsequent use of high concentration TBHP (65 wt% or higher) in epoxidation to proceed safely and efficiently, resolving the contradiction between productivity and reliability.
3Productivity
If impurity levels are reduced to less than 1 wt%, then propylene oxide yield is improved, but distillation process complexity increases
Solution Approach 1:
The distillation system uses a universal solvent (tert-butyl alcohol, TBA) that serves multiple functions: it is the reaction medium for TBHP formation, the extractant for purifying TBHP from light and heavy ends, and the catalyst solvent for the epoxidation reaction. This multi-functionality allows the same solvent to be used throughout the process, achieving low impurity levels (less than 1 wt%) and high propylene oxide yield without requiring complex additional purification equipment.
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 achieves a highly concentrated TBHP solution with low impurities, enabling effective epoxidation catalyst formation and increased propylene oxide production efficiency, while minimizing operational risks and impurity-related issues.
Implementation Method 1
a distillation procedure is employed to form a concentrated TBHP in TBA solution
Implementation Method 2
The reflux ratio (D/L) employed alternatively is at least 2:1
Implementation Method 3
an epoxidation catalyst, for a time and under reaction conditions so that a reaction product solution comprised of propylene oxide is formed
Implementation Method 4
epoxidation reactions carried out by direct injection of solutions with TBHP in TBA concentrations of 65 wt% or higher to an epoxidation reactor are highly exothermic
Data Source
Figure 1
AI summary
A process for forming a concentrated solution, including distilling in a distillation zone comprised of 10 or more theoretical distillation stages, at a pressure of no greater than 300 mm Hg and a reflux ratio (D/L) of at least 1:1, an amount of an initial solution comprised of tert-butyl hydroperoxide (TBHP) in tert-butyl alcohol (TBA) having a TBHP concentration of up to 60 wt.% and a total impurity content greater than 0.01 wt.%, for a time and under distillation conditions to form a concentrated solution comprised of TBHP in TBA; and separating an overhead distillate from the distillation zone so that the concentrated solution thereafter has a TBHP concentration greater than 60 wt.%, a TBA concentration less than 40 wt.%, a water impurity content no greater than 0.1 wt.% and a total impurity content of no greater than 1 wt.%. Related epoxidation catalyst formation and epoxidation processes are also described.