CS256086B1 - Three component solvent for aromatic extraction - Google Patents

Abstract

A three-component solvent for the extraction of aromatics, consisting of N-methylpyrrolidone, diethylene glycol and monoethylene glycol or N-methylpyrrolidone, triethylene glycol and monoethylene glycol, where the weight concentration of N-methylpyrrolidone is 25 to 40 parts, diethylene glycol 5 to 50 parts and monoethylene glycol 35 to 50 parts or triethylene glycol 20 to 50 parts.

Description

The invention relates to a solvent for the extraction of aromatics from a mixture containing non-aromatic hydrocarbons.

Several solvents are known for the extraction of aromatic hydrocarbons from mixtures containing non-aromatics. In practice, the following are used: diethylene glycol - water, a mixture of lower glycols and lower polyalkylene glycols, sulfolane, dipropylene glycol, N-methyl-ε-caprolactam, N-methylpyrrolidone, a mixture of N-methylpyrrolidone and monoethylene glycol.

With multi-component solvents, their mutual ratio is very important. This has a decisive influence on the aromatics yields during extraction, their concentration in the extract and thus the economics of the entire process.

When using a solvent consisting of N-methylpyrrolidone and monoethylene glycol, their mutual ratio is 6 to 5 : 4 to 5 and the extraction temperature is 60 to 70 ° C. Increasing the concentration of N-methylpyrrolidone at the expense of monoethylene glycol increases the yields of aromatics, but significantly reduces the selectivity, and conversely, increasing the concentration of monoethylene glycol at the expense of N-methylpyrrolidone leads to higher selectivity, but the yields of aromatics are lower.

A disadvantage of using an aromatic extraction solvent consisting of N-methylpyrrolidone and monoethylene glycol is that N-methylpyrrolidone, which constitutes 50 to 60% of the solvent, is very expensive.

We have found that by replacing part of the N-methylpyrrolidone in the two-component solvent N-methylpyrrolidone-monoethylene glycol with diethylene glycol or triethylene glycol, it is possible to achieve the same and higher aromatic yields and selectivity as when using the two-component solvent N-methylpyrrolidone-monoethylene glycol. In the two-component solvent, N-methylpyrrolidone is replaced with diethylene glycol or triethylene glycol so that the resulting concentration of N-methylpyrrolidone is 25 to 40 %.

The advantages of the new solvent are evident from the following examples:

Example no. 1: comparative

Per 100 g of the mixture used for the extraction of aromas, the composition:

non-aromatics benzene toluene Ce-aromatics higher aromatics

34.63% wt. 18.18% wt. 17.29% wt. 29.08% wt. 0.82% wt.

total 100.00% by weight.

100 g of a solvent consisting of 50% N-methylpyrrolidone and 50% monoethylene glycol is added. The mixture is stirred in a mixer at 60 degrees Celsius for 2 min and at a speed of 1,200 ^rpm , then the sample is left to stand for 20 min and the extract phase containing the solvent and aromatics is separated from the extracted substance. The extract phase is then distilled in order to separate the solvent from the extracted aromatics. The amount of distilled aromatics is weighed and analyzed chromatographically.

The amount of distillate from the extract phase and the concentration of aromatics are monitored.

The results are shown in Table 1:

amount of distillate amount of aromatics 22g 19.06g composition of the distillate nonaromatics benzene toluene Ce-aromatics higher aromatics 13.33% wt. 26.05% wt. 24.54% wt. 33.98% wt. 2.13% wt. together 100.00% wt. Example No. 2: Under the conditions given in Example No. 1, a solvent with the following composition was used: N-methylpyrrolidone monoethylene glycol diethylene glycol 40% wt. 47% wt. 13% wt. The results of the experiments are shown in Table 2: Table No. 2: amount of distillate grams of aromatics 22g 19.51g composition of the distillate nonaromatics benzene toluene Ce-aromatics higher aromatics 10.73% wt. 25.04% wt. 25.23% wt. 37.61% wt. 1.30% wt. together 100.00 % by weight Example q 3: Under the conditions given in Example No. 1 in accordance with the given quantitative data, a solvent with the following composition was used for extraction: N-methylpyrrolidone monoethylene glycol diethylene glycol 25% wt. 33% wt. 42% wt. The results are shown in table no. 3. Table No. 3: amount of distillate grams of aromatics 22.3g 20.1g

composition of the distillate Table No. 4: non-aromatic 10.55% by weight amount of distillate 21.8 grams benzene 15.35% by weight grams of aromatics 19.4 grams toluene 27.22% by weight Cs-aromatics 44.23% by weight composition of the distillate higher aromas 2.68% by weight non-aromatic 11.2 % wt. together 100.00% wt. benzene 24.3 % wt. toluene 26.4 % wt. Example No. 4: Cs-aromatics 36.5 % wt. higher aromas 1.6 % wt.

In accordance with the quantitative data given in the example and under similar conditions, a solvent with the following composition was used for extraction:

N-methylpyrrolidone 30% by weight

monoethylene glycol 35% by weight.

triethylene glycol 35 °/o wt.

The measurement results are shown in Table 4:

total 100.00% by weight.

As can be seen from examples No. 1 as a comparison and 2 to 4 according to the invention, by replacing part of N-methylpyrrolide with diethylene glycol or triethylene glycol, it is possible to achieve the same or slightly higher yields of aromatics with unchanged selectivity under the same conditions and at lower costs.

Claims (2)

A three-component solvent for extracting aromatics from a mixture comprising non-aromatic hydrocarbons, characterized in that it contains N-methylpyrrolidone in an amount of 25 to 40 parts by weight, diethylene glycol in an amount of 5 to 50 parts by weight, monoethylene glycol in an amount of 35 to 50 parts by weight. 2. A three-component solvent according to claim 1, characterized in that, instead of diethylene glycol, it contains triethylene glycol in an amount of 20 to 50 parts by weight.