Process for recovering aromatic monocarboxylic acids
A monocarboxylic acid and aromatic technology, applied in the separation/purification of carboxylic acid compounds, carboxylate preparation, chemical instruments and methods, etc., can solve the problems of benzoic acid production loss and other issues
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example 1
[0103] An artificial aqueous feed (500 g) was prepared to simulate the aqueous phase from the solids extraction step, i.e. from step (iii) / (III) of the process of the invention (in other words, from Comparative Example 1 and figure 1 The composition of stream 9). The feed was heated to 80°C and any undissolved solids were filtered off.
[0104] The filtrate was then mixed with hot toluene (200 g). Samples of the aqueous and organic layers were taken at regular intervals and analyzed by HPLC for mass transfer of benzoic acid and p-toluic acid from the aqueous phase to the organic phase. These data are shown in Image 6 and Figure 7 middle. The data show the extraction in organic liquid of organic by-products derived from the aqueous stream of the solids extraction step.
[0105] The water:toluene weight ratio in the above experiments was 1.9. In practice, the amount of water present may vary depending on the amount of water added to the residue and the amount of water us...
example 2
[0107] The first experiment simulated a process with a water:toluene weight ratio of 0.92. The results are shown in Figure 8 and Figure 10 middle.
example 3
[0109] A second experiment simulated a process with a water:toluene weight ratio of 6. The results are shown in Figure 9 and Figure 11 middle.
[0110] The recovery data for benzoic acid and p-toluic acid in each of the experiments of Examples 1 to 3 showed that the extraction was complete within 30 seconds. These 30 seconds consisted of 15 seconds mixing and 15 seconds standing, so it can be concluded that a simple inline mixer with a 15 second residence time followed by a decanter would be more than sufficient to complete the extraction.
[0111] Under normal conditions (instance 1), 70% benzoic acid ( Image 6 ) and 90% p-toluic acid ( Figure 7 ). Thus, combined with the single stage solids extraction of Comparative Example 1, this equates to a total recovery over two steps of approximately 94% benzoic acid and 68% p-toluic acid.
[0112] At reduced water content (Example 2), the benzoic acid recovery was raised to approximately 80% ( Figure 8 ), while at increas...
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