Trimellitic Acid Production via Staged Oxidation
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Solution Overview
Problem
Current processes for producing trimellitic acid from pseudocumene suffer from low yield and poor quality due to high concentrations of pseudocumene at the beginning of the oxidation, leading to difficult control and formation of undesired byproducts like isophthalic and terephthalic acids, which are catalyst poisons and complicate catalyst recovery.
Innovation Solution
The process is modified to perform the first part of the reaction semi-continuously, limiting oxygen consumption to 5-25% of the theoretical value, and completing the reaction without additional catalyst in the second stage, using a catalyst composition of cobalt, manganese, and bromine in acetic acid solvent at controlled temperatures and pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If batch oxidation is used to achieve high trimellitic acid concentration, then product concentration is improved, but byproduct formation increases and catalyst deactivation occurs
Solution Approach 1:
The oxidation process is divided into multiple stages with different oxygen feed rates. The first stage uses limited oxygen (5-25% of theoretical value) to prevent excessive byproduct formation, while subsequent stages increase oxygen supply to complete the oxidation to trimellitic acid. This temporal segmentation of the oxidation process resolves the contradiction between achieving high product concentration and minimizing harmful byproducts.
2Productivity
If high pseudocumene concentration is used at the beginning of oxidation, then reaction rate is improved, but control difficulty increases and undesired reactions occur
Solution Approach 1:
The oxygen feed rate is dynamically adjusted during the oxidation process. Initially, oxygen is limited to 5-25% of the theoretical value required for complete oxidation, preventing runaway reactions and making the process controllable. As the reaction progresses and pseudocumene concentration decreases, the oxygen supply is increased to maintain productivity. This dynamic control strategy resolves the contradiction between reaction rate and ease of operation.
3Productivity
If additional metals are added to increase catalyst activity, then oxidation efficiency is improved, but catalyst complexity and recovery difficulty increase
Solution Approach 1:
The invention removes additional metals from the catalyst composition, using only cobalt, manganese, and bromine. This simplification maintains adequate catalyst activity for the oxidation process while reducing catalyst complexity and facilitating easier recovery. The contradiction between oxidation efficiency and catalyst complexity is resolved by demonstrating that a simpler catalyst system is sufficient for the process.
4Productivity
If staged catalyst addition is used to maintain activity, then oxidation efficiency is improved, but process complexity and catalyst recovery difficulty increase
Solution Approach 1:
The catalyst is added continuously or in a single dose at the beginning of the reaction, rather than in staged additions. This maintains adequate catalyst activity throughout the oxidation process without requiring complex staged addition procedures. The continuous presence of the catalyst system simplifies the overall process while maintaining oxidation efficiency, resolving the contradiction between productivity and process complexity.
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 approach achieves high yields of trimellitic acid with reduced formation of bifunctional byproducts, simplifies catalyst handling, and allows for catalyst recovery, resulting in improved crude trimellitic acid quality and increased efficiency.
Implementation Method 1
catalytic oxidation of pseudocumene... in the presence of acetic acid as a solvent and of a catalyst which includes as basic components cobalt, manganese and bromine
Implementation Method 2
oxidation of pseudocumene to trimellitic acid... Air is fed to the reactor till the oxidation of pseudocumene is completed
Data Source
AI summary
Trimellitic acid is produced by oxidation of pseudocumene in acetic acid at temperatures between 130 and 240° C. in the presence of a catalyst composition containing cobalt, manganese and bromine. The process comprises the stages of:(i) simultaneously feeding pseudocumene and air or an oxygen-containing gas into a solution containing acetic acid and the catalyst composition, at an addition rate resulting in an oxygen concentration in the off-gas of less than 8 vol %, and at a temperature and a pressure sufficient to result in 5 to 25 mol % of the total amount of oxygen required to oxidize the pseudocumene to trimellitic acid being consumed, and(ii) feeding air or an oxygen-containing gas into the reaction mixture obtained in stage (i) until essentially all of the pseudocumene has been consumed and a molar yield of trimellitic acid of at least 90% has been obtained.There is no supplementation of catalyst after stage (i).