US2428815A - Azeotropic separation of amylenes - Google Patents

Description

OC- 14, 1947- c. R. SANDBERG Er AL AZEOTROPIC SEPARATION OF AMYLENES Filed July 27, 1946 W W gm) Mrn W ,ma fm? 5pm .N kot XSQQQ Q B -SSAQ .an nn www w om C66 M /W Patented Oct. 14, 1947 AZEOTROPIC SEPARATION OF AMYLENES Carl R. Sandberg and Gloria B. Patterson, Dallas, Tex.; said Gloria B. Patterson now by marriage Gloria B. Wren; assignors, by mesne assignments, to Socony-Vacuum Oil Company, lncorporated, New York, N. Y., a corporation of New York Application July 27, 1946, Serial No. 686,737

10 Claims. 1

This invention relates to the fractionation of a C5 hydrocarbon cut of petroleum naphtha containing pentanes and pentenes. More particuiarly, this invention is concerned with the separation of relatively pure separate streams of 3-methyl butene-l, isopentane, pentene-l, 2- methyl butene-l, n-pentane, pentene-2, and 2- methyl butene-Z by means of distillative fractionation, using methylal as an azeotropic agent.

The conversion of a light paranic virgin naphtha by thermal cracking or catalytic cracking results in the production of a C5 hydrocarbon fraction consisting of a mixture o`f parafflnic and mono-olefinic components which are extremely difficult t separate in reasonably pure form by ordinary distillative fractionation means. An efficient method for the separation of the above components in pure form is highly desirable. Thus, relatively pure pentene-l and/or pentene-Z are desirable for the production of certain polymers. Relatively pure pentene-Z can be pyrolyzed to give high yields of butadiene. Z-methyl butene-l and 2-methy1 butene-Z are desirable feed stocks to alkylation processes for the production of high antiknock alkylates of low volatility. Isopentane is valuable as a blending-stock for the production of aviation gasoline, and relatively pure n-pentane is desirable as a feed to catalytic isomerization processes. In general, the amylenes, if recoverable in pure form, are valu- A able as intermediates in the production of chemicals.

It is an object of this invention to obtain in relatively pure form separate streams of the parailnic and mono-oleflnic components of the C fraction of cracked petroleum naphtha. Another object ofy this invention is to obtain separate streams of the various amylenes of the C5 fraction of cracked petroleum naphtha. Another object of the invention is to obtain separate streams of n-pentane and'isopentane whichrare substantially free of mono-olefinic hydrocarbons. Still another object is to separate isopentane from pentene-l. A further object is to separate n-pentane from pentene-2. Other objects will appear hereinafter. Y

As indicated above, the principal components of the Cs hydrocarbon fraction consist of two parafiinic components and five mono-oleiinic components. The boiling points of these components at normal atmospheric pressure within the range of from C. to 40 C. The boiling points of the individual components are indicated below in Table I.

lie

Table 1 Component Pgtllggc' -methyl butene-l 20. 2 isopeutane 27. 9 pentene-l z50. 1 2 methyl butene 31. l n-pentane 36.08 pentene-2 y 36. 5 2-methyl buteue-2 38. 5

It is obvious to one skilled in the art that the successful separation of a mixture containing the above components is impossible by simple distillative fractionation means. We have found, however, that thes'e components can be separated by combining known methods with the use of methylal azeotropic agent for the separation of isopentane from pentene-l and for the 'separation of n-pentane from pentene-2. Y

We have found that methylal forms. an azeotrope with isopentane having the approximate composition of volume per cent isopentane and 30 volume per cent methylal. Thev boiling point of this azeotrope at atmospheric pressure is 24.1 C. We have found that methylal forms an azeo- -trope with pentene-l having the approximate composition of 74 volume per cent pentene-l and 26 volume per cent methylal. The boiling point of this azeotrope is 29.8 C. Thus, the difference in boiling ypointsv of these azeotropes is about 53 C. By forming the azeotropes lof these compO- nents We increase the differential boiling point from 2.2 C. to 5.7" C., thereby making possible the separation of the components by distillative fractionation. 4

Methylal also forms azeotropes with n-pentane and pentene-2. The n-pentane-methylalv azeotrope contains about '12 volume per cent n-pentane and 28 volume per cent methylal, which azeotrope boils at about 31.5 C. at atmospheric pressure. The pentene-Z-methylal azeotrope contains about 7 ll volume per cent pentene-Z and 29 volume per cent methylal, and vthis -azeotrope boils at about 34.9 C. at atmospheric pressure. Hence, it can be seen that by utilizing the methylal azeotropes of these components, the differential boiling point is increased from about 0.4" C. to 3.4" C.,

thus making possible the separation of these two 4 components by distillative fractionation means. In order to obtain complete separation of the components of the C5 hydrocarbon stream containing the above seven components, it is only necessary to rst separate B-methyl butene-l, 2-methyl butene-l, and 2-methyl butene-2 from the mixponents.

the mixture with a concentrated solution of hydrochloric acid containing from about 30 to 37 per cent hydrogen chloride by weight. The acid The Z-methyl butene-l treatment may be carried out at a temperature of from about 0 C. to about 20 C. in the liquid phase. The mixture of olefin chlorides and unreacted Cs hydrocarbonsis then fractionated t0 separate the olefin chlorides which may be dehydrohalogenated and fractionated to obtain relatively pure streams of 2-methyl butene 1 and 2- methyl butene-2. The unreacted Cs hydrocarbon fraction is fractionated to obtain separate cuts containing (l.) relatively pure 3-methy1 butene-l, (2) a mixture consisting substantially of isopentane and pentene-l, and (3) a mixture consisting substantially of n-pentane and pentene-2. If desired, the 3-methy1 butene-l maybe separated in relatively pure form by a preliminary fractionation of the C5 hydrocarbons which is carried out before the treatment with hydrochloric acid. The separate streams containing respectively n-pentane and isopentane are treated with methylal to form the azeotropes of the parafilns and oleilns associated therewith. These streams are separately fractionated to separate -thel azeotropes. The azeotropic fractions are scrubbed with a solvent selective for the removal of methylal therefrom to separate the methylal which is recycled to the azeotrope-forming steps. Water is an excellent solvent for the removal of the methylal from the azeotropic mixtures.

Referring now to the drawing, the C5 hydrocarbon stream 'in line I0 having a boiling range of from about C. to about 40 C. is passed by means of pump II to fractionator I2 wherein relatively pure 3-methy1 butene-l is separated and withdrawn as overhead product in line I3. The mixture of higher boiling C5 hydrocarbons is withdrawn from fractionator I2 as bottom product through line I4. This bottom product is cooled by means of cooler I5 to a temperature within the range ofirom about 0 C. to about 20 C., and is then introduced by means of pump I5 in line I'I to hydrochloric acid-treating tower 20. If desired, the C5 hydrocarbon stream in line I0 may be sent directly to tower 20 through line 2I which connects with line I1. This is particularly advantageous if the content of 3methyl butene-l in the hydrocarbon stream is relatively small. The action of concentrated hydrochloric acid on this component is only slight when contact is made with the acid in the above temperature range, but the B-methyl butene-l can be obtained as a relatively pure product stream in a subsequent fractionation as described hereinbelow. 1

Preferably tower 20 is packed with an inert material in order Vto increase contact of the hydrocarbon with hydrochloric acid which is introduced at a point near the top of the tower by means of pump 22 in line 23. The hydrochloric acid is introduced as a fine spray, and as it passes downward over the surface of the packing, it

reacts with the 2-methy1 butene-l and 2-methyl butene-2 components to form the corresponding hydrocarbon chlorides. The acid ris withdrawn from tower 20 through line 24 and at least a part of the acid is recycled to line 23 through line 25. The mixture of unreacted hydrocarbons and hydrocarbon chlorides passes overhead through line 26 to scrubbing tower 30 wherein the ascending stream is scrubbed with water to remove residual acid from the mixture. The water is introduced to tower 30 by means of pump 3| in line 32. Tower 30 may likewise be packed with inert packing material. The wash water is withdrawn from tower 30 through bottom'drawci line 33. The liquid stream containing hydrocarbons and hydrocarbon chlorides passes overhead from tower 30 through line 34 and is introduced by means of pump 35 in line 36 to fractionator 40 at a pressure within the range of from about atmospheric to 5 atmospheres, preferably about 3 atmospheres.

Fractionator 40 which may be operated in one of two ways serves to separate the relatively high boiling hydrocarbon chlorides from the unreacted hydrocarbons of the C5 fraction. If the 3methyl butene-l has been separated from the hydrocarbon mixture in fractionator I2 and recovered through line I3, the remainder of the mixture of C5 hydrocarbons passes overhead through line 4I, whence it is passed by means of pump 42 in line 43 to fractionator 45. On the other hand, if the virgin C5 hydrocarbon stream is not given a preliminary fractionation before treatment with hydrochloric acid, B-methyl butene-l is taken overhead from tower 40 through lines 4I and 44, and the higher boiling hydrocarbons are withdrawn from tower 40 as a trapout stream through line 46, which connects4 with line 43 leading to fractionator 45. The mixture of hydrocarbon chlo.- rides passes from tower 40 through line 4l to dehydrochlorination zone 50 described hereinbelow.

Fractionating tower 45 serves as a 'separation zone wherein the mixture of isopentane and pentene-l is separated from the mixture of npentane and pentene-2. Tower 45 is operated at a pressure of from about atmospheric to about 5 atmospheres. The mixture of isopentane and pentene-l is taken overhead through line 48 which connects with line 49 wherein the Cs hydrocarbons are mixed with methylal azeotropic agent. The mixture of n-pentane with pentene-2 is withdrawn as bottom product through line 5I. The amount of methylal introducedto line 49 depends on the composition of the C5 hydrocarbon stream in line 48. For every 70 parts of'isopentane in the mixture there is introduced 30 parts of methylal, and for every 74 parts of pentene-l in the mixture there is introduced to line 49 about 36 parts of methylal. The mixture of methylal, isopentane, and pentene-l is passed by means ofpump 52 in line 53 to fractionator 55, which is operated at a pressure within the range of about 1 to 3 atmospheres. The methylal-isopentane azeotrope is taken overhead through line 56 and is passed by means of pump 5'I to a point near the bottom of scrubbing tower 58. Water is introduced to tower 58 by means of pump 59 in line 60 which joins line 6I. Tower 58 is packed with an inert packing material in order to obtain better distribution of the water and better contact of the same with the ascending hydrocarbon stream. Relatively pure isopentane which is free of methylal is taken overhead through line 62.

The bottom product from fractionator 55 which consists of the methylal azeotrope of pentane-1 is withdrawn via line and passes through cooler 66. From cooler 66 the azeotrope is passed by means of pump 61 in line 68 to the bottom of scrub-hing tower 89 which is also packed with inert packing material. Water fro-inline 60 is passed to line 10 and introduced into scrubbing tower 69 at a. point near the top thereof. Pentene-l substantially free of methylal is withdrawn from the top of tower B9 through line 1 Water solutions of methylal are Withdrawn from the bottoms of towers 58 and 69 through lines 12 and 13 respectively, and the solutions are passed through line 14 to methylal recovery tower 15 as described hereinbelow.

Returning to the recovery of 2-methy1butene-1 and 2-methy1 butene-2 from the corresponding chlorides in Zone 50, the chlorides may be dehydrochlorinated thermally at temperatures within the range of from about 800 C. to 900 C. However, we prefer to obtain a mixture of these C5 hydrocarbons by first hydrolyzing the chlorides with sulfuric acid of from 60 to 70 per cent strength, and then dehydrating the alcohols with 100 per cent sulfuric acid. The mixture of Cs hydrocarbons recovered in zone 50 is passed by means of pump 16 in line 11 to ractionator 80. Substantially pure 2-methylbutene-1 is recovered overhead through line 8|, and 2-methyl butene-2 is recovered as bottoms from tower 80 through line 82.

The mixture of n-pentane and pentene-Z in line 5| passes to line 83 wherein it is mixed with methylal in the ratio of about 28 or 29 parts of methylal per '11 or '12 parts of hydrocarbon to form the methylal azeotropes of these hydrocarbons. The azeotropic mixture is passed by means of pump 84 to fractionator 85 which is operated at a pressure of from about atmospheric to about 3 atmospheres gage. The n-pentane-methylal azeotrope is taken overhead from tower 85 through line 86 and is introduced at a point near the bottom of scrubbing tower 90 by means of pump 81. In tower 90, which may suitably be packed with inert material, the azeotrope is scrubbed with water introduced to tower 90 through lines 9| and 92 by means of pump 93. Relatively pure .n-pentane passes overhead through line 94. The bottom product from tower 85 which consists of the methylal azeotrope of pentene-2 is passed through line 95 and cooler 96 by means of pump '9-1 and introduced to scrubbing tower |00 at a point near the bottom of the tower. Water is introduced at a point near the top of tower |00 from line |0|. The descending stream of water removes the methylal from the azeotrope, and relatively pure pentene-Z is recovered as overhead through line |02. The Water solution of methylal from towers 90 and |00 are withdrawn through lines |03 and |04. Water solutions together With the water solution of methylal in line 14 are passed to methylal recovery tower 15 by means of pump |05 in line |06. Methylal is taken overhead from recovery tower 15 through line |01 and is recycled to line 49 through line |08, and to line 83 through line |09. Water is withdrawn from tower 15 through bottom draWoi line |0.

The following examples illustrate the effectiveness of methylal as an azeotropic agentJ for the separation of isopentane from pentene-l, and the separation of n-pentane from pentene-2.

Example 1 Equal volumes of technical grade isopentane and technical grade pentene-l were mixed. An attempt was made toV fractionate a part of the vmixture in a wire gauze-packed fractionator tower. No separation of these C5 hydrocarbons was effected; that is, it was impossible to obtain cuts which even approximated pure isopentane and pure pentene-l. In a. second experiment '10 milliliters of the above mixture and '10 milliliters of methylal were mixed and distilled in the same column under the same conditions relative to reflux ratio, throughput, and pressure. Azeotropes were formed with both isopentane and pentene-l. The methylal-isopentane azeotropic fraction which distilled at 24.1 C., -was collected, and washed with water to remove the methylal. Hydrocarbon residue of this azeotropic fraction consisted of 28 milliliters of isopentane having an index of refraction of ND21.3539 (theoretical, ND2l.353'1). The methylal-pentene-l azeotrope was collected at 29.8 C. 24 milliliters of pentene- 1 was recovered from this fraction by washing the methylal from the fraction with water. The pentene-l had a refractive index of ND201.3'112 (theoretical, ND21.3710).

Example 2 A 'Z0-milliliter sample of C5 hydrocarbons consisting of 35 milliliters of technical grade pentene- 2 and 35 milliliters of technical grade n-pentane was mixed with 70 milliliters of methylal, and the mixture was distilled in the wire gauze-packed fractionating column. 24 milliliters of n-pentane having a. refractive index of ND21.35'11 (theoretical, ND21.3575) was recovered from the n-pentane-methylal azeotropic fraction which also contained about 9% milliliters of methylal. The methylal-n-pentane azeotropic fraction was recovered at a boiling point of Aabout 31.5 C, The methylal azeotrope of pentene-Z consisting o! 23 milliliters of pentene-2 and 9.4 milliliters of methylal was recovered at a temperature of 34.9 C. The methylal was removed from the fraction by scrubbing with Water, and the pentene-2 recovered had a refractive index of ND21.3803. The index of refraction of an equilibrium mixture of pentene2(cis) and pentene-2(trans) is ND21.3800. The index of refraction of pure pentene2(cis) is ND2l.3820, and the index fraction of pure pentene2(trans) is .ND21.3795.

These The above examples indicate that it is possible and economically feasible to separate isopentanepentene-l and n-pentane-pentene-Z mixtures by fractionating these mixtures in the presence of methylal. Methylal is easily recoverable by washing the azeotropic fractions with water.

We claim: l

1. The process for obtaining relatively pure streams consisting substantially of n-pentane, lsopentane, pentene-l, and pentene-2 from a C5 hydrocarbon stream containing the same which comprises adding to said C5 hydrocarbon stream sufficient methylal to convert said n-pentane, isopentane, pentene-l, and pentene-2 to the methylal azeotropes of these C5 hydrocarbons, fractionally distilling the mixture containing -methylal, n-pentane, isopentane, pentene-l, and pentene-2 to produce separate streams consisting substantially of methylal-n-pentane azeotrope, methylal-isopentane azeotrope, methylal-pentene-l azeotrope, and methylal-pentene-2 azeotrope, treating the separate streams containing the methylal azeotropes with a solvent selective for the removal of methylal from said azeotropes, and recovering separate streams of n-pentane, isopentane, pentene-l, and pentene-2 substantially free of methylal.

2. The process for separating a mixture of Cs 7 hydrocarbons containing 'normal pentane, isopentane, pentene-l, and pentene-2 into streams containing substantially only one Cs hydrocarbon component which comprises the steps of (1) fractionating said mixture to obtain at least two fractions consisting of (a) a mixture of isopentane with pentene-l and (b) a mixture of normal pentane with pentene-2, (2) adding methylal to fractions a and b of step 1, (3) fractlonating in separate fractionating zones the mixtures of methylal with said fractions of step 2 to obtain separate azeotropic mixtures consisting of methylal with isopentane, methylal with pentene-l, methylal with normal pentane and methylal with pentene-2, (4) scrubbing the azeotropic mixtures of step 3 in separate scrubbing zones with a solvent to remove methylal from said azeotropic mixtures, and V(5) recovering separate streams consisting substantiallyof normal pentane, isopentane, pentene-l, and pentine-Z from step 4 of the process.

3. The process for obtaining relatively pure streams of pentene-l and pentene-Z from a CtV hydrocarbon fraction of cracked naphtha which comprises the steps of (1) fractionating said C5 Vhydrocarbon fraction to obtain fractions consisting substantially ofV (a) a mixture of isopentane with pentane-l and (b) a mixture of normal pentane with pentene-2, (2) adding methylal to mixtures a and b of step-1 to form methylal-C5 ering said S-methyl butene-l from step 2` and vseparately recovering Z-methyl butene-land 2- methyl butene-Z from step 4, and (8) separately p for each 74 parts by volume ofpentene-l in said mixture, (2) fractionally distilling thel resulting mixture containing methylal, isopentane, and

hydrocarbon mixtures, (3) fractionally distilling in separate fractionating zones the methylal-'C5 hydrocarbon mixtures of step 2 to produce overhead products consisting of methylal-parafnic C5 hydrocarbon azeotropi mixtures and to produce separate higher boiling fractions consisting of Amethylal-pentene-Z and methylal-pentene-1 azeotropic mixturesas bottom-drawoi products, (4)Y scrubbing the bottom drawoi products of step 3 with a solvent selective for the removal of methylal therefrom, and (5) recovering saidfrelatively pure streams of pentene-l and pentene-2 from step 4 of the process.

4. The process for separating the'Cs hydrocarbon components of a petroleum naphtha stream consisting substantially of S-methyl butene1,iso pentane, pentene-l, normal pentane, pentene-2, 2-methyl butene-l, and 2-rnethyl butene-2 which comprises the steps of (1) passing said naphtha stream in contact with a concentrated aqueous solution of hydrogen chloride to form a mixture consisting of unreacted C5 hydrocarbons and the hydrocarbon chlorides formed from the 2-methyl butene-l and 2-methyl butene-2 in saidvstream, (2) fractionating the mixture obtained in step 1 in at least one fractionating column to obtain separate streams comprising (a) a stream of substantially pure 3-methy1 butene-l, (b) a stream consisting substantially of an intimate mixture of isopentane and pentene-l, (c) a stream consisting substantially of a mixture'of normal pentane and pentene-2, and (d) a stream consisting substantiallv of said hydrocarbon chlorides, (3) converting the hydrocarbon chlorides of step 2 to a hydrocarbon mixture containing 2-methyl butene-l and 2-methylY butene-2, (4) 'fractionating the product of step 3 to obtain separate streams of 2methyl butene-l and 2-methy1 butene-2, (5)

Y fractionating streamsb and c of step 2 in separate fr'actionating towers in the presence of methylal azeotropic agent to obtain separate streams consisting of azeotropic mixtures of methylal with isopentane, pentene-l, normal pentane, and penpentene-l to obtain separate streams consisting of methylal azeotropes of isopentane and pentene-l, (3) separately treating said methylal azeotropes with water to remove methylal therefrom, and (4) recovering said isopentane. and

pentene-l from step 3 of the process.

6. The process for separating a mixture of normal pentane and pentene-2 which comprises the steps of (l) adding to said mixture about 28 parts by volume of methylal for each '72 parts by volume 'of normal pentanerin said mixture and Valso adding to said mixture'about v29 parts by volume of methylal for each 71\parts by volume of pentane-2 in said mixture, (2) fractionally distilling the resulting mixture containing methylal, normal pentane, and pentene-2 to obtain separate streams consisting of methylal azeotropes of normal pentane and pentene-2, (3) separately treating said methylal azeotropes with water to remove methylal therefrom, and.` (4) recovering said normal pentane and pentene-2 from step 3 of the process.

7. The process for. separating aymixture consisting substantially of 3'-methyl butene-l, isopentane, pentene-l, n-peritane, pentene-2, V2- methyl butene-l, and 2-methyl butene-2 which comprises the steps of (1) fractionating said t mixture to obtain (a) an overhead streamrconsisting substantially of S-methyl butene-l and (b) a fraction containing isopentane, pentene-l, n-pentane, pentene-Z',l Z-methyl butene-l, and 2- methyl`butene-2, (2) passing fraction b of step 1 in contact with an aqueous solution of hydrogen chloride to form a mixture consisting of unreacted C5 hydrocarbons and hydrocarbon chlorides formed from 2-methyl ybutene-l. and `2- methyl butene-2 in said fraction b;V (3) fractionating the mixture of unreacted hydrocarbons and hydrocarbon chlorides obtained in step 2 in at least one fractionating column to obtain separate streams comprising a stream consisting substantially of an intimate mixture of isopentane and pentene-l, a stream consisting substantially of a mixture of n-pentane and pentene-2,`and a -stream consisting of said hydrocarbon chlorides,

butene-l and 2-methyl butene-2, (5) Vfractionattene-2, (6) removing methylal azeotropic agent from the azeotropic mixtures of step 5, (7) recoving the product ,of step 4 to obtain streams of Z-methyl buten'e-l butene-2, (6)

and 2-methyl fractionating the isopentanepentene-l stream and then-pentane-pentene-2 stream of step 3y in separate fractionating towers in the presence of methylal azeotropic agent to obtain separate streams consisting of azeotropic mixtures of methylal with isopentane, pentene-l, n-pentane, and pentene-2, (7) removing methylal azeotropic agent from the azeotropic mixtures of step 6, V(8) recovering said 3-methyl butene-l from step 1 and separately recovering 2-methyl butene-l and 2-methyl butene-Z from step 5, and

separate (9) separately recovering isopentane, pentene-l, n-pentane, and pentene-Z from step 7 of the process.

8. In the process of separating the parafnic components from the mono-olenic components of a C hydrocarbon fraction containing npentane, pentene-2, isopentane, and pentene-l, the improvement comprising the steps of (1) fractionating said Cs hydrocarbon fraction to obtain separate streams consisting substantially of n-pentane and pentene2 in one stream, and isopentane and pentene-Z in a second stream, (2) adding to the streams obtained in step 1 sufficient methylal to form methylal azeotropes of the parafllnic and mono-olefinic components in said streams, (3) separately fractionating the methylal n-'pentane azeotrope \from the methylal pentane-2 azeotrope, and separately fractionating the methylal isopentane azeotrope from the methylal pentene-l azeotrope obtained in step 2, (4) scrubbing methylal from the azeotropes obtained in step 3 with a solvent to remove methylal from said azeotropes and (5) separately recovering n-pentane, pentene-2, isopentane, and pentene-l from step-i of the process.

9. The process of separating isopentane from a mixture containing parafllnic and monoolenic C5 hydrocarbons which comprises the steps of (1) adding to said mixture sumcient methylal to form a methylal-isopentane azeotrope with the isopentane in said mixture, (2) fractionating the methylal containing Cs hydrocarbon mixture of step 1 to obtain a low boiling azeotropic fraction consisting of methylal-isopentane azeotrope, and at least one fraction containing at least one C5 hydrocarbon boiling at a higher temperature than said azeotropic fraction, (3) treating the azeotropic fraction o! step 10 2 with a solvent to separate methylal therefrom, thereby forming two liquid phases consisting of liquid isopentane in one phase and a solution of methylal in said solvent in the other phase, and (4) recovering isopentanefrom step 3 o! the process.

10. The process forI separating normal pentane from a C5 hydrocarbon fraction containing norma] pentane and Cs mono-oleflns boiling at a higher temperature than normal pentane which comprises the steps of (1) adding to said fraction suillcient methylal to form a methylal-normal pentane azeotrope with the normal pentane in said fraction, (2) subjecting the methylal containing Cs hydrocarbon fraction of step 1 to distillative fractionation to obtain a low boiling azeotropic fraction consisting of a methylalnormal pentane azeotrope and to obtain at least one fraction containing at least one C5 hydrocarbon boiling at a higher temperature than said azeotropic fraction, (3) treating the azeotropic fraction of step 2 with a solvent to separate methylal therefrom and form two liquid phases consisting of liquid normal pentane in one phase and a solution of methylal in said solvent in the other phase, and (4) recovering normal pentane from step 3 of the process.

' CARL R. SANDBERG.

GLORIA B. PATTERSON,

Now by marriage Gloria B. Wren.

i ille of this patent:

UNITED STATES PATENTS Name Date Graul July '7, 1914 Number

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