JPH02138136A - Selective separation of aromatic hydrocarbon from mixture of aromatic hydrocarbon and saturated hydrocarbon using polyethylene glycol-impregnated hydrophilic membrane - Google Patents

Abstract

PURPOSE: To transmit a feed soln. containing a mixture of an aromatic hydrocarbon and an aliphatic hydrocarbon through a specially treated hydrophilic polymeric membrane to selectively separate the mixture into a phase rich in an aromatic component and a phase poor in the aromatic component.

CONSTITUTION: A feed soln. containing a mixture of an aromatic hydrocarbon and an aliphatic hydrocarbon is applied to a hydrophilic polymeric membrane impregnated with 5-30 wt.%, pref., 10-15 wt.% of polyethylene glycol to transmit the aromatic component selectively under pervaporation to be separated into a phase rich in the aromatic component and a phase reduced in the aromatic component. Separation temp. and pressure are respectively set to a temp. range of 0-100°C and a pressure range of 0-1,000 PSIG (70.31 kg/cm²) and a vacuum is adapted to the downstream of the membrane so as to make pressure less than the equilibrium vapor pressure of the liquid feed. A mol.wt. of polyethylene glycol infiltrated into the membrane is pref. about 600-14,000.

COPYRIGHT: (C)1990,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION BRIEF DESCRIPTION OF THE INVENTION A hydrocarbon feed stream containing aromatic and saturated components is
Specially treated hydrophilic membranes selected from regenerated cellulose and cellulose acetate are subjected to barvaporation.
By selectively infiltrating the aromatic component under aporation), the aromatic component is selectively separated into an aromatic-rich phase and an aromatic-poor phase. Regenerated cellulose as such has a low flux which makes it highly selective for aromatic hydrocarbons over non-aromatic components of the feed stream. However, it has been discovered that regenerated cellulose membranes can be made selective and permeable to aromatic hydrocarbons by impregnating them with carefully controlled amounts and types of polyethylene glycol prior to use. Cellulose acetate membranes containing polyethylene glycol likewise exhibit very high selectivity for aromatic hydrocarbons.

The hydrocarbon feed stream that is separated in a preferred embodiment consists of a mixture of aromatic and saturated hydrocarbons, most typically a reformate oil stream such as a reformate gasoline stream.
te stream). This stream is then separated by solvent extraction using solvents such as sulfolane, glycols, 802, etc., but can be enriched in aromatics by distillation.

The method of using regenerated cellulose and cellulose acetate impregnated with polyethylene glycol allows selective removal of aromatics from these mixed feed streams, relieving the burden of solvent extraction or subtractive distillation. Adding to or replacing the present membrane separation process reduces the need for high energy consumption of conventional processes.

[Background of the invention]

Separation of aromatic hydrocarbons from saturated hydrocarbons is desired in many processes. Increasing the aromatic content in the reformate results in a high octane automobile fuel. Aromatics are also recovered from other similar streams for the production of various aryl alkylates and for the production of aromatic solvents.

The separation of aromatic hydrocarbons from saturated hydrocarbons is currently carried out using various techniques, for example distillation (conventional, vacuum, extraction- or azeotropic distillation); sulfolanes, glycols or SO
Solvent extraction using molecular sieves such as natural or synthetic zeolites; adsorption using molecular sieves such as natural or synthetic zeolites. Complexation of aromatic components with various chemicals such as cyclodextrin (c
Other technologies have also been proposed, including OA+plexation) and membrane separation processes.

Membrane separation processes are attractive because of their simplicity and low energy consumption. In separating aromatic hydrocarbons from saturated hydrocarbons, various constraints are placed on the membrane depending on the nature of the feed streams, such as physical and chemical similarity.

In light of these constraints and obstacles, low molecular weight hydrocarbon streams (
Barbaporation has come to be recognized as a suitable membrane separation process for the separation of aromatic hydrocarbons in CO2. Barbaporation is a process in which certain components of a liquid feed stream dissolve into and diffuse into a thin film. Downstream of the film, these components are removed by evaporating them from the surface using a vacuum or by washing with an inert fluid.

Various polymeric films were used under pervaporation. These include hydrophobic polymers such as polyethylene, polypropylene, and polyvinylidene fluoride, wood-loving polymers such as ethylcellulose and cellulose acetate, and polyethylene/styrene copolymers, aromatic polyurethanes, crosslinked polystyrene, and aromatic polyphosphonate-cellulose acetate polymers. Includes aromatic-containing polymers such as alloys. Separation factors are 1~
20, the flow rate is I X I Q-Z×I Q-'m
/n (day.
,043,891.2.958,656.2,947,
687 and 2,958,657, West German Patent 2,626
, 629, and U.S. Pat. No. 3,930,990).

The use of liquid membranes to remove aromatic hydrocarbons from saturated hydrocarbons is an alternative to barvaporation through polymeric films. The liquid film is composed of a hydrocarbon/surfactant/water emulsion in heavy mineral oil. The hydrocarbon mixture is emulsified in a filtered aqueous phase consisting of a surfactant (eg, saponin), a water-soluble polar compound (eg, glycerol, polyethylene glycol), and water. When this emulsion is dispersed in a heavier oil solvent, stable drops are formed, forming a thin film of aqueous phase between the two hydrocarbon phases.

Glycerol (or PEG) is used to increase droplet stability and overall separation efficiency.

Glycerol (or PEG) also increases the solubility of aromatic hydrocarbons in the aqueous phase and thus their migration through the liquid film. Up to 20 separation examples (separation
5ectors) was achieved. Disadvantages of this method include low droplet stability, operational complexity, and problems with recovery and circulation of the components forming the liquid film droplets. Immobilization of liquid films in porous matrices has been developed to overcome the problems and limitations associated with liquid films while maintaining the benefits of high selectivity. An immobilized liquid film is an extractable liquid trapped in a porous matrix of a solid, such as a polymeric membrane, or on the surface of such a solid.

Several methods of immobilizing liquids in membrane matrices are described in the prior literature, e.g. Chemistry Letter
s % 1980. pages 1445-1448; US Patent 3.
625,734 and 4+039,499; Fr1
edlander and Lutz, 'Membrane
s for Pressure Permeation
Membrane Process (pressure osmosis membrane)
es 1nIndustry and Biomedi
cine (Membrane Processes in Industrial and Biomedical Medicine) Section, HiroerklA, PlenuIIIPress
, NY-London, 1971 (7399
page); U.S. Patent 3,447.286 and 3,335,5
45; Recent Development i
n 5eparation 5science (Recent Developments in Separation Science), Volume CRC
Press (1973), p. 153ff; Vol.
umeV (1979), p. 11ff; US Patent 3,4
50,631 and 4,060,566; Ind, I
Eng, Chew, Process Dis, Dev
lop 12(3), 1973; and JP-A-1973 (
1978)-70084. These methods are as follows.

1. A porous unwet substrate
backing) to support the liquid film on.

2. Supporting the liquid film on a non-interactive polymer film.

3. Swelling the polymer film with liquid.

4. Casting the polymer and liquid together into a film (
casting).

5. Forming a gel using a liquid.

6. Supporting the liquid film in a porous polymer film.

Immobilized liquid membranes have been used for aromatic/saturated hydrocarbon separation by barbey boration. This membrane is produced by casting a mixture of polyvinylidene fluoride 3-methylsulfolane, which is an aromatic extractant (J, of Applied Polymer
5science, Volua+e26.489-
497 (1981)). Pure polyvinylidene fluoride membranes have high selectivities (1B for benzene/cyclohexane) but exhibit low fluxes (1o at 60°C).
-'rrr/rrr day), by adding 3-methylsulfolane to 25 wt, %, the selectivity decreases to 8, but the flow rate is 104 n? at 60 °C. /mday
increases to

Schordinger Ct- and β-cyclodextrins in hydroxypropyl methylcellulose membranes have also been used for the separation of aromatic components by barbey boration (J, Applied Po.
lya+er 5science 26.489-497
(1981)).

Polyethylene glycol has been frequently used for membrane processing and as an immobilizing liquid in various polymeric membranes. Polyethylene glycol and glycerol cause drying and pore collapse (p
It has been used as a pore stabilizer to prevent ore collapse (U.S. Pat. No. 3,772,072).

The wet membrane from the casting solution is treated with an aqueous solution of PEG or glycerol and dried leaving the PEG or glycerol in the pores of the membrane.

Polyethylene glycol has also been used as a swelling agent or non-solvent replacement in casting solutions for reverse osmosis cellulose acetate membrane production (U.S. Pat. No. 3,878,27
6). Polyethylene glycol is also used in low flow cellulose acetate membranes and hollow fibers (U.S. Pat. No. 3,873,653).
) and several other synthetic organic polymer membranes (US Pat. No. 4,087,388) have been used as plasticizers to improve flux.

From the gas mixture a polar gas, e.g. S02 or CO2
Several examples have been carried out using immobilized polyethylene glycol to separate . Briefly, polyethylene glycol (MW 300-4000) was cast with cellulose nitrate in tetrahydrofuran to produce a membrane used to selectively separate CO□ (Chemist
ry Letters.

1980, pgs, 1445-1448), an immobilized membrane of polyethylene glycol supported on a porous polymer membrane was used to separate S02 from a gas stream (U.S. Pat.
25,734), diethylene glycol on a silicone rubber membrane was used for the separation of CO□ from 02 (US Pat. No. 3,335,545). Porous base material (a porous
A stiff gel of polyethylene glycol supported on a backing and Cabosil or Cellosize was used for S02 separation (RecenL Developments).
in 5eparationScience, V
olui+e I, CRC Press, 19
73pg, 153ff). A polyhydric alcohol containing polyethylene glycol was immobilized in a porous polymer membrane and used to separate unsaturated compounds from a mixture of organic compounds (Japanese Patent Application Laid-open No. 53-70084.1978). A semipermeable membrane concept using a porous absorbent barrier containing a selective solvent to separate aromatic hydrocarbons from saturated hydrocarbons (among other things) is described in U.S. Pat. No. 3,244,763. ing.

In summary, aromatic/saturated hydrocarbon separation through membranes has been investigated using various techniques. These include the extraction of aromatic hydrocarbons from saturated hydrocarbons by percolation through polymeric membranes, barbeyboration through emulsion liquid membranes and immobilized liquid membranes. Although high selectivity was obtained in these cases, the cost was high due to the low flow rate. The present invention provides the opportunity to achieve high selectivity at higher flow rates.

[Present invention]

The present invention uses about 5 to 30 ivt of polyethylene glycol having a molecular weight in the range of about 200 to 100,000.
Selective separation of low molecular weight aromatic hydrocarbons from saturated hydrocarbons using a hydrophilic polymer membrane selected from regenerated cellulose or cellulose acetate, preferably regenerated cellulose, impregnated with . Regarding how to.

This separation method using a PEG-impregnated membrane has a high flow rate and high separation rate (
high 5 separation factors). This process using a PEG-impregnated hydrophilic membrane has the widest application in modified oil streams (ref.
aromatic content (orn+ates treaa+s)
aromatics). Such separation is important and useful in the production of high octane motor fuels, aromatic solvent production, and the like.

Aromatic hydrocarbons (aroma t 1cs) through the membrane
) selectivity and flow rate are determined by the weight percent of polyethylene glycol in the membrane, the membrane pore size (pore 5ize)
, was found to be affected by changing the molecular weight of polyethylene glycol and temperature.

Membranes suitable for impregnation with polyethylene glycol are hydrophilic, such as the regenerated cellulose membranes and cellulose acetate membranes described above. Regenerated cellulose membranes that provide the strongest hydrogen bonding between the glycol and polymer are preferred as they resist leaching of the glycol from the membrane.

Hydrophobic membranes do not hydrogen bond polyethylene glycol.

The stability of the latter in the membrane matrix is therefore low. Therefore, these membranes are not useful in the present invention.

Useful hydrophilic membranes, preferably regenerated cellulose membranes, generally have a dry thickness of about 10-25 microns, measured using an aqueous solution.
Cut molecular weight
cut offs) from 10.000 to 50.000. membrane permeation rate
e) (Flow rate) (flux) is inversely proportional to the film thickness, and a thinner film is preferable.

The MWCO of the regenerated cellulose membrane is pretreated with a caustic compound (e.g. NaOH) prior to impregnation with PEG.
Or a pore modifier such as ZnC1t solution (pore n+o
can be modified and controlled by infiltration of This is important for controlling flow rate and selectivity, as detailed in the examples below. Such processing
It increases the flow rate at G load, but on the other hand decreases the separation selectivity.

The molecular weight of PEG impregnated into the membrane is approximately 200 to 100.0.
00, preferably in the range of about 600 to 14,000. A useful concentration range of polyethylene glycol to impregnate the membrane is about 5-30% by weight, preferably about 10% by weight.
~25wt,%, most preferably about 10-15w
t, over %. Polyethylene glycol (PEG) impregnated regenerated cellulose membranes, useful for the separation of aromatic hydrocarbons from saturated hydrocarbons in the present invention, can be produced in a variety of ways. Regenerated cellulose membranes are typically supplied by manufacturers and are plasticized with glycerol or glycerin to prevent the membrane from drying out. This glycerol or glycerin must be removed prior to PEG impregnation, for example by water soaking. In a preferred method, PEG is soaked into a commercially available regenerated cellulose membrane after removal of the glycerol or glycerin plasticizer.

immersion, dipping), spray (s
(praying), passing glycerol across the membrane, etc. Immersing (immers 1on)
) is the preferred method.

Typically, the membrane is soaked in the PEG solution for a period of time, generally until equilibrium is achieved. Impregnation is a physical and not a chemical phenomenon, and neither temperature changes nor soak times above the equilibrium point affect the final loading of PEG into the membrane. The amount of PEG captured on the membrane (loading level) is determined by the amount of PEG in the soaking bath solution.
Controlled by G concentration and immersion time. However, once equilibrium is reached, longer soaking times have little effect and the PEG loading becomes constant.

At high PEGO loading, small pore membranes are more selective for aromatic hydrocarbons than large pore membranes.

The critical load of PEG (ie, the upper limit above which separation performance decreases) decreases as the membrane pore size increases. As the weight percent of PEG in the membrane increases, the flow rate increases and the selectivity decreases until a critical concentration level is reached. Above a critical concentration level, membrane performance deteriorates. P.E.
For 0600, this critical load ranges from about 13-25 wt.% depending on membrane size.

A polyethylene glycol-impregnated cellulose acetate membrane is prepared by dissolving cellulose acetate and polyethylene glycol in a solvent such as methylene chloride, and adding a suitable substrate.
Or casting plate
) Cast a thin film of the solution onto (e.g. polished metal, glass, etc.) and evaporate the solvent to produce a transparent flexible film.

The modified oil streams subjected to the process of the present invention using PEG-impregnated regenerated cellulose or cellulose acetate membranes contain aromatic and saturated components and typically have a molecular weight of no greater than C9-C2 and no greater than about 150. Become. The reformate is thus advantageously upgraded by use of the present invention to provide a high octane motor fuel.

The method of the present invention removes aromatic hydrocarbons from the feed stream with permeation rates on the order of 10-''g/m day and separation factors of 7 or higher. The flow rates and separation factors are dependent on membrane size, PEG molecular weight. , PEG loading level, and operating temperature and pressure. These relationships are described in more detail in the Examples.

Separation is carried out under perturbation conditions. The feed is in liquid phase, temperature and pressure are 0-100℃ and O-10
00PSIG (70,31kg/cnl), more preferably 0-100℃ and 0-5Q 0PSIG (3
5.16 kg/cd). A vacuum is applied downstream of the membrane such that the pressure is less than the equilibrium vapor pressure of the liquid feed. Separation is achieved by molecules diffusing through the membrane under concentration gradient driving forces caused by a downstream vacuum. The feed flow rate must be sufficient to ensure that a stagnant layer of feed does not build up on the membrane surface.

A typical experimental unit for this method is shown in Figure 1.

A hydrocarbon feed consisting of aromatic hydrocarbons and saturated hydrocarbons is fed to a feed tank (feed reserve).
r) Put it in ■. The feed is circulated across the membrane holder 4 via pump 2 and line 3. The feed returns from the membrane holder to the tank via line 5. The membrane holder has a flat framework design in which the feed flows along the top surface of the membrane and the permeate is removed under vacuum from the downstream side of the membrane via line 6. The permeate is trapped in the permeate trap 7 over liquid nitrogen. Valve operation allows the next permeate sample to be collected.

A more complete demonstration of the invention is obtained through the following examples, which are for illustrative purposes and are not intended to limit the scope of the invention.

The following examples illustrate that hydrophobic polymeric porous membranes are not suitable for the present invention. PEG600 was prepared by spreading PEG600 on the surface of a polycarbonate porous membrane (pore size -〇, 2X O, 04μ) and a polypropylene porous membrane (pore diameter = 0.05μ).
Impregnated with. The selectivity of these membranes for aromatic hydrocarbons was then tested under typical pervaporation conditions (overflow pressure - 0 PSIG (Okg/cd), downstream vacuum - 10 mmHg) at 22°C. The feed used was a toluene/heptane mixture. The results are listed in Table 1. All PEG was strained from the membrane as indicated by very high flow rates and no selectivity.

The following examples demonstrate the selective permeation of aromatic hydrocarbons into polyethylene glycol-impregnated regenerated cellulose membranes under barvaporation conditions and the membrane performance.
It is shown to be influenced by both 0 degrees and membrane pore size. Table 2 shows the physical properties of the regenerated cellulose membrane used in these tests. The wet membrane is coated with PE on the regenerated cellulose membrane.
PEG was impregnated by immersion in an aqueous solution with varying G concentration at different times. After treatment, the membrane was heated to 60°C.
The water was removed by drying and the weight percent of PEG-600 in the membrane was determined as follows.

After drying in an oven, the membranes were soaked in toluene for 15 minutes to remove excess glycol, dried, and weighed. The membrane was then soaked in water, dried and weighed.

The weight difference gives the percentage of PEG in the membrane.

Regenerated cellulose membrane type 5 (PMloo from Enka A, G) was treated with zinc chloride to enlarge the pores as follows. That is, the wet membrane was immersed in a concentrated aqueous solution of zinc chloride for 15 minutes at room temperature. The use of zinc chloride to enlarge the pores of regenerated cellulose is well known (J, Phys, Chen+, 2257(40)19
36). After this treatment, the membrane is soaked in water for at least one day to remove zinc chloride. The membrane was then treated with polyethylene glycol as described above. The selectivity of these membranes for aromatic hydrocarbons was then determined under typical pervaporation conditions (about 2-3 mm) downstream pressure of Ig and 22
Tested at ℃. The feed used was a toluene/heptane mixture. In both of these experiments using PEG-600 impregnated regenerated cellulose, PEG-60
There was no leaching from the 0 membrane. The results are shown in Table 3 below.

Tables 4 and 5 show PEG-600 impregnation type 1 (50,
Table 6 shows the results of studying the effects of temperature and aliphatic component concentration on the performance of regenerated cellulose membranes (000MWCO).
and 7 show the effect of temperature and aliphatic component concentration on the performance of ZnCl z-treated type 5 (PMloo) regenerated cellulose membranes.

Table 1 1 50.000 16.5 2
5.0 292 25.000
15.5 25.0 233
15.000 14.7 25.0
19.7 Control blank experiments were conducted using membrane type 1 (50,000 MWCO) without PEG-600 (see Table 3). Flow rates were very low and there was no selectivity for this membrane. Other membrane samples in this example were impregnated with various weight loads of PF, G-600. As seen there, PEG-600 in each film
As the weight percent decreased, the flow rate decreased and the selectivity increased for each membrane until an optimum loading level was reached. Furthermore, since flow rate is inversely proportional to membrane thickness, it can be seen that for a given PEG loading and selectivity, the thinner the membrane, the higher the flow rate. Type 4 membrane (PM250,
17.5μ thick), the flow rate is the same as the selectivity and PE
Type 3 membrane (approximately 25μ thick) for G load (approximately 24%)
) is almost twice the flow rate.

Table 1 50.0 0.04 2.3 55.0 1↓ m1kn! -12! PEG600 + 1z impregnated regenerated cell C
1-7,1'1WCG50,000 feed -44%
Hebraf 156% toluene red m1 membrane - 11,1 χ i' Ec 600, deviation ± 1.3 wl χ impregnated regenerated cellulose MWCO 50000 Temperature = 23°C Feed - toluene/heptane 29.9 30.5 36.8 40.2 41.0 45 .0 45.1 50.0 50.2 72.91 69.8 94.9 92.5] 99.6 131.7 +23.9 200.7 34.0 36.0 34.3 35.6 35. 6 37.8 36.9 35.6 37.4 1.53 1.40 1.51 1.43 1.43 1.30 1.35 1.43 1.32 17.1 26.3 23.9 33 .8 32.9 37.6 48.6 44.1 75.1 33.1 46.6 45.9 61.1 62.0 83.1 78.8 125.6 44.1 54.9 64.4 74.0 85.6 31.7 18.0 13.5 11.0 7.3 28.3 36.8 44.5 52.0 70.9 2.00 2.09 2.26 2.58 2. 44 22.7 11.4 7.5 5.3 2.2 2 Tables” - Table 1 44, I Q, 025 1.9644
．． 1 0.0013 2.2744.1
0.008 2.9243.9
0.008 3.1343.9 0.
008 3.3843.9 0.00B
3.4743.9 0.008
3.2943.7 0.048
3.0243.7 0.025 3.0
242.7 0.05 2.5742
．． 7 0.0g 2.6443.2
0.015 2.82 membrane = PM +0
0, ZnCl, treatment, 14S=3.1 Feed Nitoluene/Heptane Vacuum - 305 Tsuru Hg 1 26.8 2 26.8 3 26.8 4 26.8 5 26.8 6 26.8 7 26.8 8 35.0 9 35.0 10 50.0 11 50.0 +2 27.2 8% PEG 600°46.9 0.448 0.09
9 2.1151.5 0.494
0.091 2.3354.5
0.524 Q, 050
3.1554.7 0.526
0.054 3.1661.9
0.593 0.038 4.0B7
1.1 0.693 0.018
5.26 membrane P? I IQ(1, ZnC(1
, Processed, 19.4% PEG 600 Feed Toluene/Heptane Temperature 22°C Vacuum 3-5+uHg Loss]l liter type l, indicating that the membrane performance of the membrane is inferior to that of the same membrane impregnated with PEC,-600.
and ZnCβ2-treated type 5 regenerated cellulose were impregnated with various amounts of PEG of molecular weights 200 and 600. A ZnC12-treated Type 5 regenerated cellulose membrane was also impregnated with diethylene glycol. Diethylene glycol is quickly strained from the membrane (Ieacbe
d), the membrane became impermeable over time.

The aromatic hydrocarbon selectivity of these membranes was tested at 22° C. under typical perturbation conditions. The feed was a toluene/heptane mixture.

The results are shown in Tables 8.9 and 10 below. Comparing these results with Example 2 shows that the low molecular weight glycol impregnated membrane is inferior to the PEG-600 impregnated membrane.

■ 43.9 43.9 43.9 43.9 43.9 43.9 43.9 43.9 43.9 43.9 43.9 46.1 45.5 43.9 45.0 49.5 0 .025 0.025 0.023 0.037 0.075 0.21 0.25 Negligible 0, 002 0.11 0.17 0.23 1.54 1.51 1.43 1.27 1.20 1 .12 1.08 1.05 5.2 1.32 1.3 1.23 10.8 12.9 14.1 15.1 16.2 11.4 13.3 14.0 16.0 16.8 22.5 9.3 14.2 13.9 (T=293K, feed-toluene/heptane T=2
93, feed-toluene/heptane, vacuum-3-5
■mt1g Tang''-Sara diethylene glycol (1) IEG) PM 1004
3.9 43.9 43.9 43.9 43.9 43.9 43.9 43.9 43.9 43.9 48.2 43.9 46.9 43.9 0.013 0.18 0. 21 0.01 0.008 0.099 0.14 1.64 1.40 1.12 4.4 5.0 18.4 22.8 20.8 33.8 24.2 8.5 8.6 14 .1 16.9 12.7 14.8 19.4 25.6 3.1 0.2 T=293K.

Feed - Heptane 43.95gt0%/Toluene 56
．． 05 tons 1% Vacuum - 1,3ml 11g Tenshin l Tsuji 1 The following example uses a regenerated cellulose membrane impregnated with polyethylene glycol with a molecular weight higher than 600 to separate aromatic hydrocarbons from saturated hydrocarbons at a temperature above room temperature. This shows that it can be used for At temperatures above 50°C, PEG-600 is leached from the regenerated cellulose membrane.

Higher molecular weight glycols are more resistant to leaching at higher temperatures. In particular, the PEG 14,000 impregnated membrane showed stable performance at higher temperatures. The aromatic hydrocarbon selectivity of these membranes was tested at elevated temperatures under typical pervaporation conditions. The feed was a toluene/heptane mixture. The results are listed in Table 11.

1 Upper soil a 74 14 55.9 0
．． 005b 78 23 55.9
The following example shows that a polyethylene glycol-impregnated regenerated cellulose membrane selectively permeates aromatics from an actual reformate stream under barbey aboration conditions. The membranes used in this example were Type 5 regenerated membranes treated with zinc chloride and impregnated with 18% PEG-600, indicating that aromatics up to 10 carbon atoms permeate selectively into these membranes. It is a cellulose membrane. The aromatics selectivity of this membrane was tested at 23°C under typical barvaporation conditions.Table 12 shows the composition of the feed and permeate streams; death,
The overall selectivity to aromatics is close to that expected from the PEG concentration in this membrane.

Tang' - Kagesu country l Kumi polyethylene glycol impregnated cellulose acetate membrane, cellulose acetate (acetyl content 39.8 ± 0.5%, viscosity (
ASTM) 3±1 seconds) and polyethylene glycol 600 by dissolving it in methylene chloride. A thin film of the solution was cast onto a glass plate and the solvent was evaporated to produce a film (20μ thick). The membrane was heated at 50±1°C under pervaporation conditions.
A feed of 53±1% toluene/47±1% butane was tested. The results are listed in Table 13 below.

13χPEG 600 12 3X1
0-'16.7χPEG 600 7
6X10 bow 20χPl! G 600 9
6X10-”29.9χ PEG 600 8
6x10 bow

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the laboratory unit used to evaluate membranes for this process.

Claims (1)

Claims: 1. A feed stream containing a mixture of aromatic and aliphatic hydrocarbons of 5 to 30 wt. A method of separating aromatic components into an aromatic-rich phase and an aromatic-poor phase by selectively permeating the aromatic component into a hydrophilic polymer membrane impregnated with % of polyethylene glycol. 2. The method according to claim 1, wherein the separation is carried out under pervaporation. 3. The method of claim 1, wherein the hydrophilic polymer membrane has a dry film thickness of about 10-25 microns and a cut molecular weight in the range of about 10,000-50,000. 4. Polyethylene glycol is about 200 to 100,000
2. The method of claim 1, having a molecular weight in the range of 0. 5. Polyethylene glycol is about 200 to 100,000
4. The method of claim 3, having a molecular weight in the range of 0. 6. Polyethylene glycol is about 600 to 14,000
The method according to claim 4 or 5, having a molecular weight in the range of . 7. 10 to 25 wt. % of polyethylene glycol. 8. 10-25 wt. 7. The method according to claim 6, wherein the method is impregnated with % of polyethylene glycol. 9. Claims 1, 2, and 3, wherein the hydrophilic membrane is made of regenerated cellulose.
, 4 or 5. 10. The method according to claim 8, wherein the hydrophilic membrane is regenerated cellulose. 11. The method according to claim 10, wherein the hydrophilic membrane is regenerated cellulose. 12, the polyethylene glycol has a molecular weight of about 600, the hydrophilic membrane is regenerated cellulose, and the membrane has a molecular weight of about 13-2.
5wt. % of polyethylene glycol.