JPS60125206A - Membrane separation method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to separating a mixture into a first fraction relatively enriched in a first component and a second fraction relatively enriched in a second component. More particularly, the present invention relates to the separation of petroleum processing feed streams, particularly filtrate, extract or raffinate streams, from dewaxing or extraction zones.

One or more unit operations are often used in separating the mixture. A particular unit operation is often chosen after considering several variables, including the desired purity of the fraction to be separated, capital cost of the equipment - 4i reliability of the equipment, and operating costs. When producing lubricating oils from base stocks, the stocks are treated to remove undesirable aromatic and waxy compounds. Typically, these compounds are removed by an extraction operation. In an extraction operation, a solvent having the desired affinity for one of the feedstock components is passed through the feedstock in parallel, cross-current, or countercurrent to separate, for example, an aromatic compound from a lubricating oil feedstock. When separating raw oil, phenol,
Solvents such as furfural, acetone, and N-methylpyrrolidone may be contacted, each of which is selectively miscible with the aromatics to be removed. In the case of separating substances, purification is performed by converting Taichi oil feedstock into methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), methyl ethyl ketone/toluene, or acetone/methylene chloride, etc., which selectively removes Rouga compounds. Contact with a solvent or solvent mixture is often used. Traditionally, efforts have been made to process the extract and raffinate streams from the extraction zone in stages to further purify the bath agent separation 1 and the lubricant base stock, typically consisting of the raffinate. It has been.

U.S. Pat. No. 2,252,772 discloses dewaxing, an energy-intensive process in which the solution is cooled and decanted to separate the filtrate into two liquid phases and recycled and/or with additional treatment of vaporization. It is aimed at U-Nanasu. A solvent may additionally be added to the solution to facilitate phase separation.

U.S. Pat. No. 4,725.257 and U.S. Pat. No. 985,644
Both issues are directed to methods for extractive separation of aromatic-rich streams from petroleum fractions. The extract is then cooled and separated into an aromatic-rich hydrocarbon phase and a solvent-rich phase. The solvent-rich phase is recycled to either the midpoint or the top of the extractor, while the hydrocarbon-rich phase is passed to the steaming zone. This process has the disadvantage that the solvent returned to the extractor contains large amounts of aromatic hydrocarbons. That is, by recycling this recovered solvent to the top of the extractor, significantly more solvent will be required to effectively remove aromatics from an aromatics-containing feedstock.

Also, US Pat. No. 2,754,249 discloses extracting hydrocarbon fractions to remove non-paraffinic thread compounds. The extract is deoiled by adding materials that can reduce the solubility of the extracted hydrocarbon compounds in the solvent. The extract is then decanted and the layer containing the solvent and antisolvent is distilled to separate the antisolvent.

The substantially antisolvent-free solvent is then mixed with the solvent recovered from the raffinate phase and recycled to the extraction system. This process uses large amounts of antisolvent to achieve the desired separation. This requires distillation of the solvent-rich phase to remove large amounts of antisolvent, making the process energy intensive.

US Pat. No. 5,549,991 is directed to a method for removing aromatic hydrocarbons from petroleum fractions by solvent extraction.

In this process, the extract is passed through a membrane separation zone having a membrane that is permeable to aromatic hydrocarbons but not to solvents. The residual solvent is then passed through the r region to further purify the solvent. Although the membrane separation zone removes some of the solvent, a significant amount of the solvent must be removed during the distillation process.

Therefore, it would be desirable to provide a method that is reliable and has low operating and maintenance costs.

It would also be desirable to provide a process that requires relatively low capital expense and that can be retrofitted to existing separation equipment to improve production rates and/or product quality.

The subject invention separates the permeate (psr) by decanting and separating the mixture prior to passing the mixture through a membrane separation zone.
The present invention is directed to the discovery that the flux and/or resolution of msate is improved. Thereby, the method can reduce the number of membrane separation zones required for a given throughput and/or reduce the load on downstream equipment, such as a distillation zone.

SUMMARY OF THE INVENTION The subject invention is directed to a method of separating a mixture of a plurality of compounds into a first fraction relatively enriched in a first compound and a second fraction relatively depleted in the first compound. The method consists of first passing the mixture through a decantation zone where the mixture is separated into a first fraction relatively enriched in the first compound and a second fraction relatively depleted in the first compound. next,
At least one of the fractions from the decantation zone is passed to a membrane separation zone where the fraction is further separated into a retentate and a permeate having unequal concentrations of the first compound. Depending on the special requirements of the thread,
The permeate and/or residue can be recycled to the extraction and/or depuration zone, and if necessary, the permeate and/or residue can be recycled, such as by passing the permeate and/or residue to the distillation zone. things and/
Or the residue can be further purified. The subject method can be applied to the separation of petroleum fractions, particularly filtrate, raffinate and/or extract streams, from dewaxing or solvent extraction processes. Depending on the particular composition of the solvent used, it may be advantageous to add an antisolvent to the filtrate, extract or raffinate to further facilitate separation of the streams in the decantation zone.

3. Detailed Description of the Invention The subject invention selectively separates a mixture of two or more compounds by using a semipermeable membrane, that is, a membrane that selectively allows only a certain maple compound to pass through the membrane. Can be used in any process. When processing petroleum fractions, particularly lube oil feedstocks, aromatics and waxy compounds are removed in part using dewaxing and solvent extraction techniques well known in the art.

Referring to the figure, a conventional separation zone, e.g. solvent dewaxing zone 1
0 is shown. A feed stream 12, such as a hydrocarbon feedstock, is shown entering the denitrification zone 10, while recovered solvent is returned to the dewaxing zone by line 14. De-nu area 1
At 0, feed stream 12 is separated into wax cake and solvent/oil mixture by filtration or centrifugation. The wax cake is removed from denitrification zone 10 by line 16, and a solvent/oil stream, usually consisting of filtrate, exits denitrification zone 10 by line 1B. To facilitate phase separation, the filtrate is cooled prior to and/or during residence in the decanterizer. In this embodiment, the two filtrate streams include a heat removal zone 20;
For example, it passes through a heat exchanger and exits from the pipe 22. As will be explained more fully below, an anti-solvent can optionally be added to the filtrate via line 24. The filtrate with or without anti-solvent passes to a decantation zone 30 where it is separated into two layers.

The first solvent-rich layer, which is depleted in undesirable compounds, is removed through line 32, and the second Ω layer, which is relatively rich in undesirable compounds and has a reduced concentration of solvent, is removed through line 34. The solvent-rich stream in line 32 passes to membrane separation zone 40 . Membrane separation zone 40 includes a semipermeable membrane 42 through which, in the illustrated process, a relatively pure solvent stream passes and exits through conduit 44 . The residue is reduced in concentration of the solvent! It passes through Route 46. In the illustrated OS, streams 34 and 46 combine to form stream 48 and pass to distillation zone 50.

A distillation zone 50 separates a column 48 into a relatively pure solvent stream 52 and a bottoms stream 5 relatively concentrated in undesirable compounds.
Separate into 4. The melt, side streams 52 and 44 are combined to form stream 1
4 is formed, and n+1 is circulated to the rice removal area 10 as described above.

Distillation zone 50 may or may not be required depending on the desired purity of permeate and/or residue. For example, if the distillation zone is a rate-limiting operation, the present invention can increase the overall production rate without adversely affecting the product from the distillation zone.

The following examples demonstrate the usefulness of the subject invention in increasing the flow rate through membrane 42. In this example, the solvents were 25% acetone, 81% by weight, and 75% Tokei methylene chloride.
It consisted of a mixture of. The mixture is useful for solvent extraction of waxy compounds in demineralization operations. A typical representative filtrate juice was made consisting of 20% by weight hydrocarbon compounds and about 80% by weight solvent. When this solution was cooled to -29°C and decanted for about 5 minutes, about 4%
0 volume 1! This resulted in a hydrocarbon-rich bottle consisting of Ilt% and about 6-0 volume N% of solvent. The solvent-rich lower layer is hydrocarbon
°9 volume 11% and solvent 91 volume Ni! It consisted of %.

The upper and lower layers each consisted of approximately 50% filtrate by volume. The upper layer was taken over, and the lower layer was 400 paig (28
Spectrapore (Sp
*etrapore) 3500 semipermeable membrane was passed through the membrane separation zone 40. The membrane was manufactured by Spectrum Medical Industries, Los Angeles, California, USA, and consisted of a regenerated cellulose membrane with a pore size of approximately 15 mm. This membrane was preconditioned for use in the subject process by permeating the water-containing membrane followed by methanol and then methyl ethyl ketone. The feed solution was mixed with the membrane at 400 pmig (28 kg'/crt?
G) and contacted at ambient temperature. As shown in &I, removal of the hydrocarbon top layer significantly increased the flux rate and at the same time decreased the oil content in the permeate. The system requires fewer membrane separation units for a given treatment hoe and/or improves the quality of the permeate.

Table 1 In actual industrial denitrification operations, the membrane separation zone 40 would be expected to be maintained at a much lower temperature, such as the -29° C. temperature used in the decantation zone SO. Although the hot water rate will decrease due to the increased viscosity of the permeate at lower temperatures, the relative flux and purity of the permeate using the decantation zone will still be lower at similar operating conditions. It will be higher than the system without decantation.

Although a pretreated cellulose membrane was used in this example, it is clear that other membranes are also suitable. Similarly, although this example aimed at separating arm wax oil from lubricating stock oil, the present invention can also be applied to other yarns by using a semipermeable membrane with an appropriate pore size and chemical resistance. can.

Depending on the particular characteristics of the system, it may be desirable to add antisolvent to the stream prior to or during residence of the antisolvent in decantation zone 30 to improve separation of components between the two layers. Antisolvents added to avoid the introduction of additional compounds into the system often consist of a solvent that has a lower solubility in the solvent system for the compound to be removed. For example, MEK/MIBK or M E
In the removing solvent system consisting of K/) luene or acetone/methylene methylene, it is advisable to add a solvent with lower solubility in oil, ie MEK or acetone, as an anti-solvent. Furthermore, for example, in extraction, it is advisable to add water as an anti-solvent.

Although Table I was directed to the separation of a solvent-lubricating oil-quad system, the present invention provides the 41r! It is clear that it is equally applicable to the system. Similarly, although the feedstock to the decantation and/or membrane separation zone in this example is the liquor from the deropping field cess, it is equally clear that the invention can be practiced on the extract or raffinate stream from the extraction process. It is.

It is also possible to apply the invention to other separation processes where the feed to the decantation zone is not the effluent stream from the extraction zone.

[Brief explanation of drawings]

The accompanying drawings are a simplified schematic of one method of carrying out the subject invention.
- Mutsumi. 10: Solvent dewaxing zone 20: Heat removal zone 30: Decantation zone 40: Membrane separation zone 42: Semipermeable membrane 50: Distillation zone

Claims (1)

[Claims] 1. A method for separating a first compound from a mixture of a plurality of compounds: (b) passing at least one of the liquid fractions from the decantation zone to a membrane separation zone, where the fraction 2. A process according to claim 1, characterized in that the mixture comprises the effluent from the extraction and/or dewaxing zone. Method described. (5) The method according to claim 1 or 2, wherein at least a part of the second fraction from the decantation zone is recycled to the extraction and/or denitrification zone. 4. [The method according to any one of claims 1 to 3, in which the permeate from the separation zone is recycled to the extraction and/or depuration zone.5. Claims 1 to 4 circulating from the separation zone to the extraction and/or depuration zone
The method described in any one of paragraphs. & A method according to any one of claims 1 to 5, wherein the residue from the membrane separation zone is passed through a distillation zone to further separate the first compound from the mixture. 1. Process according to any one of claims 1 to 6, characterized in that the temperature of the mixture is lowered prior to and/or during residence of the mixture in the decantation zone. 8. A process as claimed in any one of claims 1 to 7, in which an anti-solvent is added to the mixture to facilitate separation of the mixture into a first fraction and a second fraction in a decantation zone. 9. Any one of claims 1 to 8g4, wherein the mixture consists of an extract from an extraction and/or de-rice area.
The method described in section. 1α The method according to any one of claims 1 to 9, wherein the first compound is a hydrocarbon.