p-Aminobenzoic Acid-2-Ethylhexyl Ester Hydrogenation for High Purity
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Solution Overview
Problem
Existing processes for preparing p-aminobenzoic acid-2-ethylhexyl ester, a precursor for the UV filter ethylhexyl triazone, suffer from low purity, require additional purification steps, and are not economically or environmentally optimal for large-scale industrial applications.
Innovation Solution
The process involves reacting p-nitrobenzoic acid-2-ethylhexyl ester with hydrogen in the presence of a catalyst in water or a mixture of water and 2-ethylhexanol, utilizing a catalyst like palladium, and incorporating a ripening time under hydrogen pressure to achieve high purity and yield, thereby simplifying purification and reducing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If catalytic hydrogenation is performed in protic solvents like water or alcohol, then the reaction proceeds with good heat dissipation and high yield, but unwanted side reactions occur and additional purification steps are required
Solution Approach 1:
The patent changes the chemical parameter of the solvent system from traditional aprotic solvents to a specific mixture of water and 2-ethylhexanol. This parameter change enables the reaction to proceed with excellent heat dissipation while achieving high product purity (99.5-99.8%) by eliminating side reactions, thus resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent uses 2-ethylhexanol as a solvent that can be directly carried over from the preceding esterification step without removal. This 'copying' approach eliminates the need for intermediate solvent removal and replacement steps, maintaining high productivity while ensuring product purity through the specific properties of the carried-over solvent
2Manufacturing precision
If additional purification steps are implemented to remove side products, then product purity is improved, but process complexity and costs increase
Solution Approach 1:
The patent extracts and eliminates the source of side reactions by using a specific water-2-ethylhexanol solvent system that prevents side product formation altogether. This extraction of the harmful chemical environment eliminates the need for subsequent purification steps, reducing process complexity while maintaining high product purity
Solution Approach 2:
The reaction system is designed to be self-purifying by selecting solvent conditions that inherently prevent side reactions. The water-2-ethylhexanol mixture creates a reaction environment where only the desired hydrogenation occurs, and the catalyst can be easily removed by filtration, making the system self-sufficient without requiring complex additional purification equipment
3Manufacturing precision
If conventional solvents are used and removed, then side reactions are minimized, but additional solvent removal steps and waste treatment are required
Solution Approach 1:
The patent implements a solvent recovery strategy where 2-ethylhexanol is carried over from the esterification step and directly used in the hydrogenation step without removal. The solvent is then recovered and recycled in subsequent steps, eliminating waste while maintaining product purity. This approach transforms what would be waste solvent into a useful process asset
Solution Approach 2:
The patent merges the solvent systems of two separate process steps (esterification and hydrogenation) by using 2-ethylhexanol as a common solvent. This consolidation eliminates the need for intermediate solvent removal and replacement, reducing both waste and process complexity while ensuring product purity through consistent solvent quality
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 method results in p-aminobenzoic acid-2-ethylhexyl ester with high purity and yield, reducing complexity, waste, and costs, making it suitable for large-scale industrial applications.
Implementation Method 1
reacting p-nitrobenzoic acid-2-ethylhexyl ester with hydrogen in the presence of a catalyst
Implementation Method 2
the reduction of p-nitrobenzoic acid esters either by catalytic hydrogenation
Implementation Method 3
performing the reaction in water or in a mixture of water and 2-ethylhexanol is advantageous with respect to the heat dissipation due to the beneficial specific heat capacity provided by water
Implementation Method 4
the reduction of p-nitrobenzoic acid esters either by catalytic hydrogenation in a mixture of ethanol and methanol or using a catalyst and a reducing agent
Data Source
AI summary
The present invention relates to a process for preparing p-aminobenzoic acid-2-ethylhexyl ester comprising reacting p-nitrobenzoic acid-2-ethylhexyl ester with hydrogen in the presence of a catalyst, wherein the reaction is performed in water or in a mixture of water and 2-ethylhexanol. Further, the present invention relates to the p-aminobenzoic acid-2-ethyl hexylester obtained by the process and having high purity.