RU2214443C1 - Method for deparaffination of paraffinaceous oil fractions - Google Patents

Abstract

FIELD: petroleum processing. SUBSTANCE: paraffinaceous fraction is mixed with methyl tert-butyl ether-based selective solvent containing ion-forming additive. Mixture is cooled and filtered, after which dewaxed oil and petrolatum are obtained. Ion-forming additive is preferably compound selected from NaCl, NaOH, Na₂CO₃, Na₂SO₄, KCl, KOH, FeCl₃, FeSO₄, CuSO₄, or their mixture in the form of aqueous solution taken in amounts 0.1 to 3% based on the volume of solvent. EFFECT: increased yield of dewaxed oil with improved viscosity index and increased filtration velocity. 6 cl, 6 tbl, 5 ex

Description

 The invention relates to a method for dewaxing paraffinic hydrocarbon oils by crystallization in a solution of selective solvents and can be used in the refining industry.

 When dewaxing raffinates and de-oiling gachets, a mixed solvent is currently widely used, which is a mixture of methyl ethyl ketone (MEK) and toluene in a ratio of 60:40 by volume [Kazakova L.P., Crane S.E. Physico-chemical fundamentals of the production of petroleum oils. M .: Chemistry, 1978, p. 143].

 One of the disadvantages of this solvent is the high specific energy costs during the regeneration of the solvent. A significant reduction in specific energy consumption can be achieved by replacing toluene with a solvent with a lower pour point, in particular methyl tert-butyl ether (MTBE).

A known method of dewaxing of oil raffinates using MTBE together with a number of polar solvents, in particular with ketones C ₃ -C ₆ [US patent US 4444648 from 04.24.1984].

 One of such compositions, MEK-MTBE 60:40 by volume, provides a higher filtration rate, a higher yield of oil and a lower gradient of dewaxing compared to the traditional solvent MEK-toluene 60:40 (by volume).

 Table 1 presents the main quality indicators of the used and proposed solvents.

 An analysis of the main quality indicators of the solvents presented shows that acetone-MTBE is preferred.

 The ingredients of this solvent have the lowest viscosity, which will provide the lowest energy costs for its regeneration.

 The disadvantage of solvents based on a mixture of MTBE and precipitant and, in particular, acetone-MTBE is that they do not provide a high yield of oil and high filtration rates.

 The task is to increase the yield of dewaxed oil, improve its quality (viscosity index), increase the filtration rate.

 The problem is solved in that when applying to a solvent based on a mixture of methyl tert-butyl ether with a precipitant of an ion-forming additive, the performance of the dewaxing process of oil raffinates improves.

It is preferable to use C ₃ -C ₆ ketone or methanol or toluene or N-methyl pyrrolidone or a mixture thereof as precipitant.

 It is more preferable to use a mixture of acetone and methyl tert-butyl ether in a ratio of 40:60 by volume as a solvent.

It is preferable to use, as an ion-forming additive, a compound from the group comprising NaCl, NaOH, Na ₂ CO ₃ , Na ₂ SO ₄ , KCl, KOH, FeCl ₃ , FeSO ₄ , CuSO _4, or a mixture thereof.

 More preferred is the use of an ion-forming additive in the form of an aqueous solution in an amount of from 0.1 to 5% by volume per solvent.

 Most preferred is the use of a mixture of acetone and methyl tert-butyl ether in a ratio of 40:60 by volume with the addition of a 25% aqueous NaOH solution in an amount of 0.8% by volume per solvent.

 Water-soluble salts and alkalis, creating ion fields, contribute to the separation of crystals of solid hydrocarbons, which leads to a noticeable increase in the rate of filtration and the release of oil.

 In addition, there is an increase in the adsorption of resinous substances on the surface of growing crystals of solid hydrocarbons, as a result of which the resulting oil has a higher viscosity index.

 As the feedstock, all oil raffinates were used, the qualities of which are presented in table 2.

Example 1 (applied method)
In a flask equipped with a mechanical stirrer, pour 100 ml of raffinate. The raffinate is heated to +70 ^o C, and then, with constant stirring, the raffinate is cooled to a temperature of +50 ^o C. To the raffinate cooled to +50 ^o C is added the solvent MEK: toluene in a ratio of 60:40 (by volume) in the following amounts:
1) for raffinates of the III fraction (350-420 ^o C) and the IV fraction (420-500 ^o C) - 300 ml;
2) for raffinate II fraction (300-400 ^o C) and residual raffinate - 400 ml.

The resulting solution is cooled with constant stirring at a speed of 60 ^o C / hour to a temperature of minus 20 ^o C. The suspension obtained at a temperature of minus 20 ^o C is poured into a funnel with a filter cooled to minus 20 ^{o C.} After filtration, the precipitate of crystals of solid hydrocarbons on the filter is washed with 100 ml of solvent, cooled to minus 20 ^o C.

From the obtained filtrate (solution of dewaxed oil) and precipitate (cake of gacha or petrolatum), the solvent is distilled off and the yield of dewaxed oil and gacha (petrolatum) is determined. For raffinate II oil fraction 300-400 ^o With the temperature of the final cooling of the solution of raw materials (suspension), the temperature of the filter funnel and washing is minus 52 ^o C.

Example 2 (known method, prototype)
The dewaxing is carried out under the conditions of example 1 using a solvent according to the known method [3] of the following composition, vol.%:
Methyl ethyl ketone - 60
Methyl tert-butyl ether - 40.

Example 3 (the proposed method)
The dewaxing is carried out under the conditions of example 1 using a solvent of the following composition, vol.%:
Acetone - 40
Methyl tert-butyl ether - 60.

 The acetone solvent: MTBE = 40: 60 (by volume) additionally contains 0.8% (by volume) of an aqueous NaOH solution with a concentration of 25%.

Example 4
The dewaxing is carried out under the conditions of example 1 using a solvent of the following composition, vol.%:
Acetone - 40
Methyl tert-butyl ether - 60.

Example 5
The dewaxing is carried out under the conditions of example 1 using a solvent of the following composition, vol.%:
Acetone - 40
Methyl tert-butyl ether - 60.

 The solvent additionally contains 0.8% (by volume) of water.

 The results of dewaxing are presented in tables 3, 4, 5 and 6.

 From the above data it is seen that the proposed method (example 3 for each raffinate) in comparison with the known method allows to obtain dewaxed oil with an equal pour point, provides a higher filtration rate, a greater yield of dewaxed oil with a higher viscosity index.

Claims (6)

 1. The method of dewaxing paraffinic oil fractions by mixing them with a selective solvent based on a mixture of methyl tert-butyl ether with a precipitant, cooling the mixture and filtering the resulting suspension, isolating the dewaxed oil and hatch (petrolatum), characterized in that they use a solvent with addition to him ion-forming additives - water-soluble salts, or alkalis, or mixtures thereof. 2. The method according to claim 1, characterized in that C ₃ -C ₆ ketone, or methanol, or toluene, or N-methyl-pyrrolidone, or a mixture thereof is used as precipitant.  3. The method according to p. 1, characterized in that as a selective solvent using a mixture of acetone and methyl tert-butyl ether in a ratio of 40:60 by volume. 4. The method according to claim 1, characterized in that as an ion-forming additive using a compound from the group including NaCl, NaOH, Na ₂ CO ₃ , Na ₂ SO ₄ , KCl, KOH, FeCl ₃ , FeSO ₄ , CuSO ₄ or their mixture.  5. The method according to claim 4, characterized in that the ion-forming additive is added in the form of an aqueous solution in an amount of from 0.1 to 5% by volume per solvent.  6. The method according to claim 3, characterized in that as an ion-forming additive using a 25% aqueous solution of NaOH in an amount of 0.8% by volume per solvent.

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