Tertiary Alkyl Ester Stabilization via N-oxyl Mediators
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Solution Overview
Problem
Existing processes for preparing tertiary alkyl esters of (meth)acrylic acid face issues with polymerization, fouling, and low yield due to the use of PNP, which is toxic, explosive, and expensive, and require additional stabilization steps to prevent decomposition of stabilizers like OH-Tempo under acidic conditions.
Innovation Solution
A novel process involving the reaction of (meth)acrylic acid with olefins in the presence of an acidic catalyst, followed by separation and stabilization using N-oxyl compounds like 4-hydroxy-2,2,6,6-tetramethyl-1-oxylpiperidine (OH-Tempo) to prevent polymerization and fouling, allowing for high-purity and high-yield isolation of tertiary alkyl esters without PNP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PNP is used as stabilizer, then polymerization is inhibited, but PNP is toxic, explosive, and expensive
Solution Approach 1:
The patent replaces expensive and hazardous PNP with a combination of cheaper, safer stabilizers (PTZ and hydroquinone monomethyl ether) that can be easily replenished. The new stabilizer system is less hazardous and more economical, accepting that they may need more frequent replenishment rather than relying on a single long-lasting but dangerous stabilizer
Solution Approach 2:
The patent introduces PTZ as an intermediary stabilizer that works in combination with hydroquinone monomethyl ether to provide the polymerization inhibition previously achieved only by PNP. This intermediary approach allows using multiple milder stabilizers instead of one harsh stabilizer, reducing toxicity and explosivity while maintaining effectiveness
2Reliability
If OH-Tempo is used as stabilizer in acidic reaction conditions, then polymerization is prevented, but OH-Tempo decomposes rapidly
Solution Approach 1:
The patent uses PTZ as a protective intermediary that stabilizes the reaction environment and protects OH-Tempo from rapid decomposition by sulfuric acid. PTZ acts as a buffer that mediates between the harsh acidic conditions and the sensitive OH-Tempo stabilizer, allowing OH-Tempo to function effectively for longer periods
Solution Approach 2:
The patent applies prior cushioning by having PTZ present in the reaction mixture before OH-Tempo is exposed to harsh conditions. PTZ预先 absorbs some of the acidic stress and creates a more favorable environment for OH-Tempo, cushioning it against rapid decomposition and extending its effective lifetime
3Reliability
If PTZ is used alone as stabilizer, then polymerization is inhibited, but stabilizing action in workup is insufficient leading to polymerization and fouling
Solution Approach 1:
The patent merges PTZ with hydroquinone monomethyl ether to create a synergistic stabilizer system. The combination provides complementary stabilizing actions that cover both the reaction phase and the workup phase, ensuring polymerization inhibition throughout the entire process and preventing fouling while maintaining high product purity
Solution Approach 2:
The patent creates a composite stabilizer system combining PTZ and hydroquinone monomethyl ether, where each component contributes different stabilizing mechanisms. This composite approach provides more comprehensive protection against polymerization and fouling than either stabilizer alone, achieving both reliability and manufacturing precision
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 high-purity and high-yield isolation of tertiary alkyl esters with reduced polymerization and fouling, and allows for recycling of products for additional stabilization, improving yield and extending plant run times.
Implementation Method 1
in process step (4), at least one compound S which comprises at least one N-oxyl group is added as a stabilizer
Implementation Method 2
reacting (meth)acrylic acid with at least one olefin of the general formula I in homogeneous phase in the presence of an acidic catalyst in a reactor
Data Source
AI summary
The present invention relates to a process for preparing tertiary alkyl esters of (meth)acrylic acid having at least 4 carbon atoms in the alkyl radical. The process includes reacting (meth)acrylic acid with at least one olefin of formula (I) in homogeneous phase in the presence of an acidic catalyst in a reactor, discharging the resulting reaction mixture from the reactor, separating the discharged reaction mixture into a first mixture which contains the catalyst and a second mixture which contains the tertiary alkyl ester of (meth)acrylic acid having at least 4 carbon atoms in the alkyl radical, and removing the tertiary alkyl ester of (meth)acrylic acid having at least 4 carbon atoms in the alkyl radical from the second mixture in the presence of compound S, which comprises at least one N-oxyl group and is added as a stabilizer.