US3312749A - Removal of aromatic compounds from coke oven gas - Google Patents

Description

C. J. HESS ET AL April 4, 1967 REMOVAL OF AROMATIC COMPOUNDS FROM COKE OVEN GAS 2 sheets-sheet 1 Filed July 24, 1963 April 4, 1967 C, J, HESS ETA. 3,312,749

REMOVAL OFAROMATIC COMPOUNDS FROM COKE OVEN GAS Filed July 24, 1963 2 Sheets-Sheet 2 INVENToRs CU/l//n Ll. Hess BY W/Y//bm M. Perry United States Patent O 3,312,749 REMOVAL F ARMATIC COMPOUNDS FROM CKE VEN GAS Calvin J. Hess and William M. Perry, Bethlehem, Pa., as-

signors to Bethlehem Steel Company, a corporation of Pennsylvania Filed July 24, 1963, Ser. No. 297,286 1t) Claims. (Cl. 260-674) This invention relates to the removal of artomatic compounds from coke oven gas, and more particularly, to the recovery of the aromatic compounds in a high state of purity.

It is a major object of the invention to recover a benzene product having a high freeze point.

Another object is to recover a pure benzene product from coke oven gas by a method which utilizes conventional gas scrubbing equipment.

A further object is to recover a high-freeze -point benzene product from coke oven gas wherein additional purifying steps, ordinarily required for such recovery, are eliminated.

In coke oven gas, resulting from the distillation of coal in the manufacture of coke, light oils contained in the gas are ordinarily removed from the gas by means of a light oil scrubber. After the tar, ammonia, phenol and substantially all of the naphthalene h-ave been removed from the gas, the gas enters a scrubber, or scrubbers, wherein light oil is removed from the gas stream. When the gas enters the scrubber, it contains, besides light oil, considerable amounts of aliphatic and alicyclic compounds. The aliphatics so contained comprise, primary, certain paratiins and olens, while the alicyclics are represented by naphthenes such as cyclohexane and methyl cyclohexane. The aromatic compounds contained in the gas at this point are mono-cyclic, except for possibly trace amounts of naphthalene, and are represented by benzene, toluene, and xylene, known in the trade as BTX. By far, the greater percentage of the BTX is in the form of benzene.

In prior practice, the coke oven gas has been treated in the light oil scrubber by countercurrent washing, or scrubbing, with a hydrocarbon wash oil, familiarly known as straw oil. The function of the straw oil is to absorb and remove the aromatics from the gas. For certain industrial uses, the light oil aromatics recovered in this manner are quite satisfactory. However, with known scrubbing practices, a clean cut separation between aromatics on the one hand, and aliphatics and alicyclics on the other, is never attained, as straw oil tends to absorb some of the aliphatics and naphthenes. Certain aliphatics and alicyclics, i.e. benzene contaminants, cannot be distilled from benzene because they form azeotropes with benzene and the said azeotropes have boiling points close to benzene. Table I lists some of these azeotropes.

TAB LE I Azeotrope Composition Many present `day industrial requirements for benzene, as wel-l as for toluene and xylene, as, for example, in the production of aniline, styrene, etc., require an aromatic material of high purity. In light oil scrubbing practice with straw oil, the benzene product obtained therefrom will have a freeze point not higher than 4.8 C. average.

Because the benzene market today requires a larger percentage of high quality product-benzene having a freeze point of 5.3 C., or above-it has become increasingly difficult for the producer of benzene from coal to meet present day requirements, with the methods and equipment which are a well-known part of a coke oven byproduct plant. The difficulty begins with the scrubbing operation, for the prior methods of scrubbing will not produce a crude BTX from which a refined benzene of high freeze point can be produced, with the conventional rening steps to be found in most coke works. The foregoing applies to toluene production, as well, although toluene is generally marketed under different quality specifications.

We have found that by scrubbing coke oven gas with certain glycols, a light oil product can be obtained which is substantially free of aliphatics and alicyclics, and from such light oil a benzene of high purity is obtainable. If thiophene is present in the benzene at this point, thiophene can be removed by a relatively inexpensive subsequent step, as will be explained, so that production of a benzene having a freeze point of 5.4 C. is entirely feasible with our method.

Essentially, the method is one in which -a coke oven gas is introduced into a light oil scrubber, and contacted therein counter-currently with a glycol of the class which we shall refer to as polyoxyalkylene glycol terminal monoether. A quantity of water is mixed with the glycol. By scrubbing at low temperature and pressure, or at atmospheric pressure, a light oil product can be obtained which has a much lower analysis of the usual contaminants found in light oil than that produced by prior scrubbing practice.

The type of scrubbing medium which may be used to elfect eicient separation of the aromatics from the coke oven gas, is typified by a glass of polyoxyalkylene glycols which have a terminal monoether group. These compounds have the following constitutional formula: y

The compounds of this class have average gram molecular weights ranging from about 250 to 1000. The x and y components occur in about equal molar concentrations and in a block and/ or random distribution manner. The terminal alkoxy group, wherein n may be an integer of from 1 to 5, includes the butoxy, propoxy, ethoxy, etc. forms. The viscosity of this class of compounds ranges from about 55 to 300 Saybolt Universal seconds at F.

The glycol is mixed with about 1 to about 10 weight percent of water, and introduced into the scrubber, preferably `in a downwardly direction, where it meets incoming coke oven gas in countercurrent fashion. The scrubbing operation is performed at atmospheric temperature or higher, preferably in a range of from about 20 F. to about F. The pressure in the scrubber may be atmospheric, or slightly higher, but preferably not to exceed 25 pounds per sq. in. gage.

In prior methods of scrubbing, the varying composition of the gas had a direct effect on the quality of the resultant light oil product. This was so due to the low degree of selectivity of the straw oil absorbent as between aromatics and non-aromatics. In treating a gas relatively high in non-aromatics with straw oil, a greater amount of non-aromatics nd their way into the light oil product. In our process, the light oil product will contain a low amount of non-aromatics yregardless of the amount of these constituents in the gas before treatment.

In the drawings:

FIG. 1 is a flow diagram of a light oil scrubber located 3 .n in a coke oven by-product line immediately following the final coolers, and subsequent light oil refining steps.

FIG. 2 is a flow diagramindicating :testing procedure in making comparative light oil recovery tests.

The following example describes one method by which our invention may be performed continuously for recovering light oil, and ultimately, a refined benzene Vproduct, from coke oven gas.

Referring to FIG. l, coke oven gas, from which essentially all of the tar, ammonia, phenol and naphthalene have been removed, is led from final cooler 1 through line 2 and introduced into scrubber 3 under the normal pressure of the gas main. The gas enters the scrubber at a rate of about 500 cu. ft./sec. The absorbing or scrubbing medium is composed of a solution of a polyoxyalkylene glycol monoether and three weight percent of water. The specific glycol monoether used in this case is the butoxy form of a polyoxyethylene-polyoxypropylene glycol monoether polymer. This compound can be obtained under the trade name of Ucon 50-HB- 100, and is manufactured by Union Carbide Chemicals Co. The scrubbing mixture passes through sprays 4 and contacts the upfiowing gas. During the scrubbing action, the scrubbing liquid removes aroma-tics from the gas. The temperature maintained in the scrubber is abou-t 20-30`C., while a pressure of about 26 to 35 inches of water is maintained. The de-aromatized gas leaves the scrubber at 32. This gas still contains aliphatics and naphthenes. The liquid collected at the bottom of the scrubber is withdrawn a-t line 5. This liquid, benzolized absorbent, contains scrubbing solution, forerunnings, primary light oil and secondary light oil. At this point, the scrubbing operation has been completed, and the valuable benzene-toluene-xylene (BTX) has been separated from the coke oven gas.

However, in order to obtain a refined benzene, or toluene and xylene, product, it is necessary to process the benzolized absorbent through a series of additional steps.

Referring again to FIG. l, the liquid mixture from scrubber 3 is directed through line 5 via heat exchanger 6 to stripping column 7, wherein the total light oil, i.e. hydrocarbon mixture, is stripped from the glycol monoether-water absorbent. The glycol monoether, having a relatively high boiling point, remains as liquid in the still, and is withdrawn from the bottom of column 7, through line 8 and heat exchanger 6 to storage tank 30, from whence it may be withdrawn through line 31, and, when mixed with the proper amount of water, re-introduced into Vscrubber 3 for the scrubbing of additional coke oven gas.

The total light oil leaves column 7 via pipeline 9 and enters column 10 wherein the secondary oil (benzene, toluene, and xylene) is separated from the primary oil (coumarone, indene, naphthalene, etc.). The secondary oil or crude BTX leaves column 10 via line 12 and enters forerun removal column 13, In column 13, the forerunnings (carbon disulfide, cyclopentadiene, etc), are separated Afrom the BTX by distillation and are removed via line 14. The forerun-free BTX is withdrawn from column 13 via line 15 and is pumped to agitator 16 by way of valve 15. In the agitator, the BTX is washed with 66 B. sulfuric acid to remove oleiins and thiophenes. The acid-washed BTX is then neutralized by washing with an 18% by weight aqueous solution of sodium hydroxide in the same agitator. The neutralization step is followed by a Water wash. After discharging acid sludge, waste caus-tic, and Water, in turn, from the bottom of the agitator by means of valve 17 and line 19, the refined BTX is withdrawn via line 18 and sent to residue column 20. During the sequence of operations in agitator 16, the main, forerun-free, BTX stream is diverted into agitator 16 which acts as a reservoir for the incoming BTX while the treating steps are being performed in agitator 16; in addition, the residues are being removed lfrom agitator 16 and treated BTX is being pumped to residue column 20. After these operations are completed, the main stream is again directed to agitator 16, and the same sequence of steps is performed in agitator 16 while agitator 16 is being refilled. In column 20 the BTX is withdrawn as overhead vapor through line 21. Residue is removed through line 22 and the BTX is introduced into distillation col-umn 23. In this column benzene is separated from the remainder of the BTX and leaves the column as refined benzene at line 24. The remaining liquid toluene and Xylene are removed `from the column by way 4of line 25, and sent to fractionating column 26.

Y In lcolumn 26 the toluene is first volatilized and rremoved as overhead vapor by way of line 28 and valve 29. Xylene is then distilled off by way of line 28 and valve 29. Toluene and Xylene are sent to storage by way of lines 33 and 33' respectively. Residue in column 26 is removed at line 27.

If desired, oleum may be used in the acid washing step at agitator 16, in place of concentrated sulfuric acid. Oleum will effect a more ecient removal of the thiophene from the BTX at this point, but with some small loss of benzene.

To obtain a benzene product low enough in thiophene to meet any and all specifications for commercial use, the benzene withdrawn yfrom still 23 should be given an oleum wash, in addi-tion'to the Wash at 16. Sulfuric acid of 66 B.r gravity may be substituted for the oleum in the washv at this point, but removal of the thiophene will not be as efficient. The oleum washed benzene will have a freeze point above 5.3 C., and, under efficient operating conditions, it is possible to obtain a benzene product having a freeze point as high as 5.45 C. The thiophene in the benzene treated with concentrated sulfuric acid would probably be no higher than 300 ppm. Benzene which has been -oleum washed will have a thiophene content of about 1.0 ppm. or less.

The polyoxyalkylene glycol monoether absorbent used for scrubbing must be in the liquid condition at the point of use. These liquid glycol ethers have viscosities between 55 and 3-00 S.U.S. at 100 F., and have no `substantial fractions boiling below 230 C. Certain glycol monoethers which fall within this group, can be ascertained and identified by `reference to Union Carbide Chemicals Catalog No. F-6500G, entitled Ucon Fluids and Lubricants, at page 24 (1960). Ucons in the catalog, and range from Ucon 50-I-IB-55 to Ucon 50HB300. The digits following I-IB, in each case, represent the S.U.S. vviscosity a-t F. The molecular weight of these compounds will-range between 250 and 2000. It has also been found that the glycol monoether-s, or Ucons, described, mixed with the proper quantity of water (1 to 10 weight percent), can be used efficiently as scrubbing aagents when diluted with up to as much as 25% by weight of diethylene glycol.

In the scrubbing operation, single or multiple units may be used, depending on the capacity required to scrub the existing gas volume. Units may be inserted in parallel, series, or parallel-series combinations to suit the requirements of individual plants. The individual units themselves may vary in operational details, and useful types include venturi scrubbers, unpacked spray towers, with or without recirculation, packed and packed-spray combination towers, and tray columns. In practice, the loose packings are usually metal turnings, and the trays are wooden grids (hurdles). The absorption efficiency of the scrubbing operation will be affected to some extent, by the type of scrubbing unit used. However, the variations in absorption eiciency as between the different types of conventional scrubbing units is not great, and the type of scrubber selected will generally be a factor of availability and individual choice on the part of the operator.

In order to establish, clearly, the advantage of our scrubbing process, in terms of refined product, over prior conventional scrubbing procedure, two tests were made, each with a different scrubbing medium. In test A, the

The compounds are designated asl V5V scrubbing medium was the hydrocarbon wash oil known as straw oil, and produced by Atlantic Refining Company under the name of Atlantic A. In test B, the scrubbing medium was polyoxyethylene-polyoxypropylene glycol monobu-tyl ether (Ucon 50-HB-100) mixed with 3% water by weight. Except for the diiference in scrubbing liquid, the two tests were run under conditions as nearly identical as it was possible to make them. The two tests were made simultaneously, test A being made in absorber A, and test B in absorber B. As this was an experiment l designed strictly for the purpose of comparing results from two different absorption systems, conventional scrubbing equipment was not used. The apparatus employed is shown diagrammatically in FIG. 2.

In conducting the tests, inlet gas temperature, the

`amount of gas treated per unit of time in each absorber,

and the water bath temperature for each absorber were recorded for each hour during the entire test, which ran continuously for 55 hours. It is deemed suiciently signicant to record these figures here in the form of ve hour increments. These data are shown in Table II, as follows:

charged with 7760 grams of the glycol monoether and 240 grams of distilled water. This scrubber was also sealed and connected to the gas main through plastic tubing 37 and copper tubing 34. In order to provide uniform, relative temperature in the absorption reactions during the entire test period, scrubbers A and B were maintained immersed in water baths 38 and 38', respectively.

At the start of the test, stopcocks 41 and 41 were opened, and coke oven gas was introduced into the system by way of copper tube 34. Part of the tubing, in coiled form, was surrounded by a water bath 35 to control the temperature of the incoming gas. The cop-per tubing led from the water bath to a moisture trap 42 containing glass wool. The coke oven gas, leading from the trap, entered plastic hose 36. This hose had a Y-joint leading to branches 37 and 37'. By means of the branched inlet tubes, it was possible to permit equal quantities of the gas to liow through each scrubber simultaneously, and to thus produce identically controlled operating conditions. As shown in Table II, these conditions were checked routinely during the test run. The gas exhausting TABLE II Temp. nt Temp. of Water Bath Water Bath Time, Inlet Gas Absorber A, Absorber B, Surrounding Surrounding l'lours Temp., F. cn. it. gas cu. it. gas Absfoirger A, AbsorCber B,

86 22 22 96 23.0 20.8 24 24 94 52. 6 51. 2 24 24 78 83.2 82. 3 23 23 82 107. 2 105. 6 23 23 S2 135. 4 135. (l 23 23 S0 163. 4 102. 3 23 23 82 192. 8 191. 7 23 23 88 214. 8 213. 8 24 24 90 244. 7 242. 4 23 23 82 270. 4 275. 6 23 23 84 300. 0 300. 0 24 24 The coke oven gas used in the tests had a proximate analysis, based on analyses made at times prior to, and subsequent to, the test runs, as follows:

TABLE III Components: Percent by vol. Methane 30.51 2.5 Ethylene 2,. 3 1 0. 3 Ethane 1.610,2 Propene 0.3 1 0.05 Propane 0.3 10.05 Butenes 0. 0710.02 n-Butane 0.0210002 Cyclopentene and/ or cyclopentadienes A'0.01-10.001 Pentanes or cyclopentanes 0.01 1 0.001 Methyl cyclopentane Y Cyclohexane 0.011 0.005 44AIHeptane.. i .Benzene 0,510.10 Toluener 0.210.105 Xylene 0.05 10.0011 Hydrogen 51.1140 Nitrogen 4.9 11.0 Carbon monoxide 6.111.5 Carbon dioxide 2411.0 Hydrogen `.sulfide 0.5 10.02

Carbonyl sulfide 0.0110002 Referring to FIG. 2, scrubber A, a five gallon countercurrent, Agas-liquid absorber, or scrubber, shown at 39, was charged with 8000 grams of the hydrocarbon wash oil. The scrubber was sealed and connected to the coke oven gas main by way of plastic tubing 37 and a 3/8 inch v(Ld.) copper tube 34.. Scrubber B, shown at 39', was

from each absorber was metered on wet test gas voiume meters 40 and 40.

Exactly 300 cu. ft. of gas were passed through each absorber, in a period of 55 hours. At the end of the test, absorber A had an increase in weight of 132.5 grams. Absorber B had increased in weight by 192.5 grams.

-At the end of the run, the liquid absorbent and absorbate were removed from each absorber. The liquid from absorber A was distille-d to separate and recover the absorbed light oil, which oil contained predominantly aromatic hydrocarbons. The crude light oil from absorber A weighed 136.5 grams, equivalent to 1.71% by weight of the original absorbent. About 50 ml. of a black, gu'mrny, tarry waste material settled out of the wash oil during and after the steam distillation.

The absorbent-absorbate from scrubber B was also distilled to separate the light oil therefrom. The crude light oil in this instance amounted to 128.1 grams, or 1.60%y by weight of the original absorbent. There was no observation of any gummy, tarry material settling out from the absorbent of absorber B, either during or after distillation.

The light oils from the two absorbers were refined separately by the following steps:

(1) Forerun removal and collec-tion of a crude benzenetoluene-Xylene (BTX) by distillation.

(2) Acid washing of the BTX fraction.

(3) Fractional distillation of the acid washed BTX to obtain purified benzene and toluene.

In the first refining step, 125.0 lgrams of light oil from absorber A were distilled to remove the forerunnings. Likewise, 121.9 grams of light oil from absorber B were distilled. The results of these distillations are shown in Table 1V.`

'.the combined distilled benzene TABLE IV From Scrubber A From Serubber B Grains Wt. Gramsl Wt.

percent percent Light Oil Charge 125.0 121.9 Forerun (up to 77 C.,

B.P. at 760 mm. press.) 4. 3. 20 2 5 2.05 BTX (77 C. to 145 C.,

13.1). at 760 mm. press.) 78.8 63. 0 90.3 81.5 Residue (primary oil) 33. 8 10. 4

The residues from step 1 will contain from about 25% to 30% by weight of absorbent.

The recovered BTX fractions from each absorber were acid washedV separately with 66 B. sulfuric acid and neutralized with 18% sodium hydroxide. The washing procedure was performed by agitating 75.7 g. of BTX, in the case of absorber A material, and 75.0 g. in the case of absorber B material, in a 100 ml. separatory funnel with 1.5 ml. of the acid for 20 minutes. The agitated liquid was allowed to settle for 20 minutes, after which it was again agitated for 20 minutes, this time with a fresh 1.5 ml. portion of acid. After another 20- minute settling period, the samples were each agitated for 20 minutes with a 2.5 ml. portion of the caustic solution. This was followed by a 20 minute settling period, a second 20 minute neutralization with a fresh 2.5 ml. portion of caustic, and nally another 20 minute settling period. At the end of this proced-ure there remained 72.7 g. of washed BTX from absorber A and 70.2 g. of washed BTX from absorber B. Losses, represented -by difference in weight between the washed BTX and the original BTX charged to the funnel before washing, inclu-de olens and thiophenes. l

In the third and final refining step, the washed BTX from each absorber was separately subjected to a fractional distillation. Results of the distillations are shown in the following table.

TABLE V.-VBTX FRACTIONS 8 separately analyzed by gas chromatography. The result' ant data, tabulated in TableI VI, showing a reduction in aliphatic and -alircyclic contaminants in the case of absorber B, clearly demonstrate the advantage of the polyoxyalkylene glycol monoether-water absorbent over the conventional hydrocarbon straw oil.

TABLE VI Contaminants Contaminants Contaminants Aliphatie in Benzene from in Benzene from and Alicyclic Absorber A, Absorber B,

Percent Percent n-Hexano 0. 044 0. 026 2,4-dimethyl pentane 0. 104 0. 061 Methyl eyclopentane 0.211 0.075 2,3-diinethyl pentane 0. 385 0. 087 Cyclohexane 0. 426 0. 122 n-Hept-uie 0. 458, 0.091 Methyl cyclohexane. 0. 035 0.015

Our invention provides a method by which coke oven plant operators are enabled to upgrade their benzene product with existing equipment.

This invention can also be practiced in conjunction with hydrogenation processes for refining benzene, by eliminating the acid or oleum wash treatment and feeding the forerun-free BTX to a hydrogenation reactor. For example, the glycol scrubbing step may precede a hydrogenation process, such as that described in U.S. Patent No. 3,081,259 to Donovan et al. By this m-ode of operation, the BTX product introduced into the hydrogenation reactor will be quite low in aliphatic compounds, thus reducing the hydrogen and thermal cracking requirements over those required for hydrogenating the BTX product resulting from prior scrubbing practices.

We claim:

1. A method of treating coke oven gas to recover a benzene product having a high freeze point which comprises scrubbing coke oven gas with lan aqueous solution of a glycol of the type designated as polyoxyalleylene glycol terminal monoether having a gram molecular Absorber A Absorber B Total Cut Weight,

Percent Benzene, Toluene, impurities, Weight, Benzene, Toluene, impurities,

Percent Percent Percent Percent Percent Percent Percent Percent Total Benzene- Total Benzene 55.8 Total Tolnene Total Toluene 26. 1 Total Xylenes. Total Xylenes 18. 1

As can be ascertained from the table, only the benzene :and toluene were volatilized in the distillations, the temperature being purposely held below the point at which Xylene would distill over. This was done because of the extra operational lprecautions required to obtain Xylene along with the benzene and toluene fractions, and the lack of significance of fractionally distilled values for Xylene had they been obtained. The percent-age of the yXylene fraction in each case was determined by measuring the volume of residue in the distilling flask.

The combined benzene from absorber A had a freeze point (dry) of 5.0 while the combined benzene from absorber B had a freeze pointfdry) of 5.3" C. land contained 0.023% Kolens.

The combined distilled benzene from absorber A and from absorber B were C. and contained 0.025% olens, Y

weight of from about 250 to 1000 at a temperature of from 20 F. to 120 F. and at a pressure of n-ot more than 25 p.s.i.g. land thereby removing `a liquid lproduct of benzene, toluene and xylene from the gas with said solution, and separating benzene from the other constituents of the liquid.

2. A method of treating coke oven gas to recover a benzene product having a high freeze point which comprises scrubbing coke oven gas with an aqueous sol-ution of a glycol of the type designated las polyoxyethylenepoly-oxypropylene glycol terminal monoether having a gram molecular weight of from 250 to 1000 at a temperature of from 20 F. t-o 120 F. and at a pressure of not more than 25 p.s.i.g. and thereby removing a liquid product containing benzene, toluene and Xylene from the gas with said solution, separating benzene from the other constituents of the liquid and washing the separated benzene with acid.

3. A method according to claim 2 wherein the separated benzene is Washed with sulfuric acid.

4. A method of treating coke oven gas to recover a benzene product having a freeze point of 52 C. which comprises scr-ubbing coke oven gas with an aqueous solution of a glycol `of the type designated -as polyoxyalkylene glycol terminal monoether having a gram molecular Weightt of from about 250 to 1000, said solution comprising water in an amount of from 1% to 10% by weight of said monoether at Ia temperature of from 20 F. to 120 F. and |at a pressure of not more than 25 p.s.i.g. and thereby removing a -liquid product containing benzene, toluene and Xylene from the gas with said solution, separating benzene from the other constituents of the liquid and Washing the separated benzene with oleum.

5. The improvement in 1a method of treating coke oven gas to recover a benzene product having la high freeze point which comprises scrubbing coke oven gas with a liquid glycol of the type designated as polyoxyethylenepolyoxypropylene glycol terminal monoether having a gram molecular Weight of from about 250 to 1000 and water in an amount of from 1% ot 10% by weight of said monoether at a temperature of from 20 F. to 120 F. and at a pressure of not more than 25 p.s.i.g.

6. The improvement in a method of treating coke oven gas to recover a benzene product having a freeze point above C. which comprises scrubbing coke oven gas with an aqueous solution of a glycol of the type designated as polyoXyethylene-polyoxypropylene glycol terminal monoether having a gram molecular weight of from about 250 to 1000, said solution comprising Water in an amount of from 1% to 10% by Weight of said monoether, at a temperature of from 20 F. to 120 F. and at a pressure of not more than 25 p.s.i.g.

7. The method of claim 3 in which from 1% to 10% Water by Weight is mixed with the glycol.

8. The improvement in a method of treating coke oven gas to recover `a benzene product having a freeze point above 5 C. which comprises scrubbing coke oven gas with an aqueous solution of a polyoxyalkylene glycol terminal monoether having a gram molecular Weight of HO [CHZ-CHZO) x-(CHz-CHCHaO y] CnHzlnl-l- 1 Where x and y components occur in about equal molar concentration and n is an integer of from 1 to 5, said solution comprising Water in an `amount of from 1% to 10% by weight of said monoether at a temperature of from 20 F. to 120 F. and at a pressure of not more than 25 .p.s.i.g.

9. The improvemnet in a method of treating coke loven gas to recover a benzene product having -a freeze point above 5 C. which comprises scrubbing coke oven gas with -an aqueous solution of a polyoxyethylene-polyoxypropylene glycol terminal monoether having a gram molecular weight of from about 250 to 1000 .and la Saybolt Universal viscosity of between and 300 at 100 F., said solution comprising water in an amount `of from 1% to 10% by weight lof said monoether at ya temperature of from 20 F. to 120 F. and at a pressure of not more than 25 p.s.i.g.

10. The improvement in la method of treating coke oven gas to recover a benzene product having -a freeze point above 5 C. which comprises scrubbing coke oven gas with an aqueous solution of the butoxy form of a polyoxyethylene-polyoxypropylene glycol monoether having a gram molecular weight of from about 250 to 1000, said solution comprising water in an 'amount of from 1% to 10% by weight of said monoether, at a temperature of from 20 F. to 120 F. and at a pressure of not more than 25 p.s.i.g.

References Cited bythe Examiner UNITED STATES PATENTS 2,730,558 1/1956 Gerhold 260-674 2,834,820 5/ 1958 Bloch 260-674 FOREIGN PATENTS 460,633 10/ 1949 Canada.

11,758 11/ 1913 Great Britain.

DELBERT E. GANTZ, Primary Examiner. C. E. SPRESSER, IR., Assistant Examiner.

Claims (1)

1. A METHOD OF TREATING COKE OVEN GAS TO RECOVER A BENZENE PRODUCT HAVING A HIGH FREEZE POINT WHICH COMPRISES SCRUBBING COKE OVEN GAS WITH AN AQUEOUS SOLUTION OF A GLYCOL OF THE TYPE DISGNATED AS POLYOXYALKYLENE GLYCOL TERMINAL MONOETHER HAVING A GRAM MOLECULAR WEIGHT OF FROM ABOUT 250 TO 1000 AT A TEMPERATURE OF FROM 20*F. TO 120*F. AND AT A PRESSURE OF NOT MORE THAN 25 P.S.I.G. AND THEREBY REMOVING A LIQUID PRODUCT OF BENZENE, TOLUENE AND XYLENE FROM THE GAS WITH SAID SOLUTION, AND SEPARATING BENZENE FROM THE OTHER CONSTITUENTS OF THE LIQUID.

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