US2638438A - Hydrogenation of naphthas - Google Patents

Description

y 1953 E. J. HOFFMANN ET AL 2,638,438

HYDROGENATION OF NAPHTHAS Filed Sept. 1, 1950 Feed Nophfha Hydrogen I Hydrogenation Zone Organic Sulfur 2 Compound 19 Treafed Naphfha .26

-Sefflin Zone Lg a g 26 Used Sodi Sodium Hydroxide Hydroxide Solution INVENTOR. Edward J. Hoffmann, BY Edward F. WadIey,

Patented May 12, 1953 HYDROGENATION OF'NAPHTHAS v l'idward J. Hoffman and Edward F. Wadley,

Baytown, Tex assignors, by mes'nc assigm ments; to Standard Oil Development Company, Elizabeth, N J., a corporation of Delaware Application September 1, 1950, Serial No. 182,649

(01. ice-28) Claims.

The present invention is directed to a method for nydrogenating a naphtha fraction containing olefins. More particularly, the invention is concerned with a method for hydrogenating a cracked naphtha containing monoand diolenns under conditions such that the diolefins-are selectively hydrogenated.

The present invention involves hydrogenating a'naphtha fraction, such'as a cracked naphtha, boiling in the gasoline range containing monoand-diolefi-ns in which the cracked naphtha has added to ita small amount, in the range from 0.1% to 1.0% by weight, of a caustic soluble organic sulfur compound following which the naphtha; to which the caustic soluble organic sulfur compound is added, is contacted under hydrogenation conditions with a sulfur insensitive hydrogenation catalyst in the presence of hydrogen to cause-selective hydrogenation of said dfolefins to the substantial exclusion of the hydrogenationof the mono-olefins to form a hydrogenated product containing the residual organic sulfur compound and hydrogenated products of the suifur compounds. The hydrogenated prodnet is then subjected to treatment Wltha solutionof alkali metal hydroxide to remove the 'residual organic sulfur compound and hydrogenate dproducts of sulfurand'flnally the sci-treated fraction is recovered for further use as may be desired.

The caustic soluble organic sulfur compound may be selected from the classconsisting: of'the aliphatic mercaptanshaving from 1 to 4 carbon atoms in the moleculeand the thiophenols boiling up to 450 F., the'aliphatic mercaptans includingmethyl mercaptan, ethyl mercaptan, normal propyl and is'opropyl mercaptans, normal butyl, secondary butyl and tertiary butylmercaptansas well as the corresponding aliphatic unsaturated mercaptans, such as ethylene merc'aptan, propylene mercaptan and the butylene mercaptans. By the term thiophenols we mean to include the broad class of thiophenols which include benzenethiol and the alkyl substituted benzene thiolsboiling upto 450 F. This class oi compounds, which is alsocaustic soluble, includes benzene thicl, the methyl benzene thiols, the ethyl benzene thiols, 2,4 dimethyl-l'benzene thiol, 2,5 dimethyl-l benzenethiol and 23,6 trimethyldbenzene thiol.

, Organic sulfur compounds selected from the aforementioned class may be added to the naphtha-containing mono-olefins' and diolefins iii-an amount inv the range between 0.1. and 1% by weight based on. the naphtha.

Ordinarily the ,2 amount added may be in the range from about 6.1% to 0'.5% by weight.

The hydrogenation conditions employedin'the practice of the present invention include the employment of a sulfur insensitive catalyst, suchas a catalyst illustrated by the sulfides of molybdenum, tungsten and nickel. Mixtures of 'the'sulholes of these metals may suitably be employed; For example, a mixture of nickel and tungsten sulfide performs admirably in the process'ofthe present invention.

Temperatures employed in the present invention may range from 400t0 600 F. with a preferred temperature being in the neighborhood of about 500 F. The pressure may be in the range from 50 =to50'0 p. s. i. g. or a somewhat lower pressure may be used; for example, apressure ores p. s. i. gsmay'be employed.

Hydrogen to oil ratio may range from to 2000 cu. ft. of hydrogen per barrel of ieedwith good results being obtained in the range from about 100' to 1000 cu. ft. per barrel. The cracked naphtha to which the organic sulfur compound has been added may be charged in contact with the catalyst at a liquid space velocity in the range from 1.5 to 12 v./v./hour with satisfactory results being obtained in the range fromabout 2 to 8 v./v./hour.

The invention will be further illustratedby reference to the drawing in which the single figure is aflow diagram of a preferred'modcoi conducting the invention.

- Referring now to the drawing, numeral l'l designates a charge tank in which a cracked naphthe fraction, such. as a thermally cracked'orcatalytically cracked naphtha, is stored. Such a naphtha fraction may contain monoand diolcfins and may have a bromine number any-- where from about '10 to 50 or more, depending on the content of the oleflnic and p'araffinie hydrocarbons therein. The feed naphtha is withdrawn from tank H by line i2 containing pump I3 and is discharged-thereby into a hydrogenationzone l4. Prior to entrance into hydrogenation zone Hi, the cracked naphtha has admixed with it an; organic sulfur compound which is introduced into line I2 by line 15 from asource not shown. The caustic soluble organic sulfur compound is selected from the class of compounds illustrated but, vfor purposes of this description, will be assumed to'be a relatively low boiling mercaptan, such as methyl, ethyl oributyl mercaptans. The organicsulfur compound is admixed with the cracked naphtha in: an amotmt'initherangezfrom 0.1 to 1% by weight and the admixture of naphtha and mercaptans discharged into hydrogenation zone I4 where the naphtha is contacted with hydrogen introduced by line I6. For purposes of this description hydrogenation zone I4 is shown as a rectangle in the drawing but it will be clearly understood that zone I4 will include catalytic reactors containing a sulfur insensitive hydrogenation catalyst as described, and means for admixing hydrogen with the naptha and separating unreacted hydrogen and light gases which may be formed in the reaction from the hydrogenated product. Hydrogenation zone l4 may be said to include all auxiliary hydrogenation facilities well known to the art for hydrogenating naphtha fractions containing olefins.

The conditions in hydrogenation zone I4 embrace those mentioned before. The hydrogenated product is discharged from hydrogenation zone I4 by line I! and the product will be substantially free of diolefins while the mono-olefins and the organic sulfur compound added to the said. naphtha may be substantially untouched. The hydrogenation product will also include hydrogenated sulfur compounds resulting from the hydrogenation of certain sulfur compounds which may originally be present in the said naphtha. It is well known that hydrogenation will lower the sulfur content of petroleum fractions by converting certain sulfur compounds to hydrogen sulfide which may be readily removed from the hydrogenated naphtha. The hydrogenated product is admixed in line I! with a caustic alkali solution, such as sodium hydroxide, introduced thereto by line 26. The solution of sodium hydroxide may be an aqueous or alcoholic solution of, sodium hydroxide, such as a solution in methyl alcohol. Preferably the sodium hydroxide solution is an aqueous solution of sodium, hydroxide having a Baum gravity in the range of 5 to 30. A sodium hydroxide solution having a Baum gravity in the range of 5 to 30 gives very satisfactory results. The admixture of hydrogenated product and sodium hydroxide solution is discharged by line I'I into a settling zone I8 wherein a sufficient residence time is provided to allow separation of the sodium hydroxide treated naphtha from the sodium hydroxide solution, the treated naphtha being withdrawn by line i9 for distillation or for further treatment, as desired, and/or for use as a fuel. The used sodium hydroxide solution is discharged from settling zone 58 by line 20, controlled by valve 2I and may be discharged from the system thereby. Preferably, however, a substantial portion of the used sodium hydroxide solution is recycled to line H by branch line 22 controlled by valve 23 and containing pump 24 by discharging a certain amount of the used sodium hydroxide solution by manipulation of valve 2| and by introducing a suiiicient amount of fresh sodium hydroxide solution by line 20 controlled by valve 25 to maintain the strength of the sodium hydroxide solution at the desired level to remove the organic sulfur compound added to line I2 by lines I5 and also to remove hydrogenated products of sulfur which may be found in the product issuing from hydrogenation zone 14.

From the foregoing description taken with the drawing it will be seen that a simple, readily adaptable process is provided for selectively hydrogenating diolefins in olefin-containing fractions.

The invention will be further illustrated by the following runs in which a thermally cracked naphtha having an original sulfur content of 0.04 had added to it a sufficient amount of tertiary butyl mercaptan (a caustic soluble compound) and a caustic insoluble sulfur compound to provide a feed mixture having a lamp sulfur content of 0.25% by weight. The said naphtha had a bromine number of 41.6. A portion of the naphtha to which the tertiary butyl mercaptan was added was then hydrogenated by passing it in contact with a nickel sulfide-tungsten sulfide catalyst at a space velocity of 2.9 v./v./hour, a temperature of 505 F., a pressure of 45 p. s. i. g. and a hydrogen rate of 900 cu. ft. per barrel of feed. The hydrogenated product had a sulfur content of 0.043 of which the remaining tertiary butyl mercaptan content may be easily removed by contact with an aqueous solution of sodium hydroxide. The bromine number of the hydrogenated product was 33.9 while the bromine number conversion was only 18.5%. On the other hand, the conversion of dlolefins as indicated by an ultraviolet absorption coefiicient at a light wave length of 235 millimicrons 88%. These results clearly show that the diolefins were substantially hydrogenated to the substantial exclusion of the mono-olefins. The sulfur conversion was 83%.

A second run was made under substantially the same conditions as the first run with the exception that the liquid space velocity was 6 v./v./hour and the hydrogen rate per barrel of feed was cu. ft. In this instance the sulfur content of the feed was reduced to 0.061, the bromine number to 37.4. The bromine number conversion was 10.1% while the sulfur conversion was 76%. Again the ultraviolet absorption coefficient at a light wave length of 235 millimicrons showed that nearly 70% of the diolefins had been converted while the bromine number showed that only a slight amount of conversion of the mono-olefins had been effected. It will be seen from the second run that at the higher space velocities with less hydrogen substantial conversion of diolefins to the substantial exclusion of hydrogenation of mono-olefms was ef fected.

A cracked naptha fraction treated in accordance with the present invention wherein the diolefins are selectively hydrogenated and the mono-olefins are substantially unaffected is an important tool in petroleum refining operations since the mono-olefins are very beneficial in gasoline due to their high octane numbers. On the other hand, the diolefins are very deleterious due to their inherent characteristics of reacting with oxygen and forming gum compounds. Therefore, the present invention, which selectively removes the diolefins, removes the deleterious compounds without afiecting the beneficial compounds by incorporating in the feed stock to a hydrogenation process an amount of an organic sulfur compound which is caustic soluble and which may be removed from the hydrogenation products. It is only the caustic soluble organic sulfur compounds which may be effectively employed in the practice of the present invention and removed therefrom in accordance with the aforementioned description.

The nature and objects of the present invention having been completely described and illustrated, what we wish to claim as new and useful and to secure by Letters Patent is:

l. A method for hydrogenating a naphtha fraction boiling in the gasoline range containing monoand diolefins wherein the diolefins are hydrogenated selectively which comprises adding to said naphtha fraction a caustic soluble organic sulfur compound selected from the class consisting of the aliphatic mercaptans having from 1 to 4 carbon atoms in the molecule and the thiophenols boiling up to 450 F. in an amount in the range from 0.1% to 1.0% by weight based on said naphtha, contacting the naphtha to which the organic sulfur compound has been added with a sulfur insensitive hydrogenation catalyst at a temperature in the range between 400 and 600 F. and at a pressure between45 and 500 p. s. i. g. in the presence of hydrogen under conditions to cause selective hydrogenation of said diolefins to the substantial exclusion of hydrogenation of said mono-olefins to form a hydrogenated product containing said organic sulfur compound and hydrogenated products of sulfur, treating said hydrogenated product with a solution of alkali metal hydroxide to remove therefrom said organic sulfur compound and hydrogenated products of sulfur and recovering said treated product.

2. A method for hydrogenating a cracked naphtha fraction boiling in the gasoline boiling range containing monoand di-olefins wherein the diolefins are selectively hydrogenated which comprises adding to said naphtha fraction a caustic soluble organic sulfur compound selected from the class consisting of the aliphatic mercaptans having from 1 to 4 carbon atoms in the molecule and the thiophenols boiling up to 450 F. in an amount in the range from 0.1% to 1.0% by weight based on said naphtha, contacting the naphtha to which the organic sulfur compound has been added with a sulfur insensitive hydrogenation catalyst at a temperature in the range between 400 and 600 F. and at a pressure in the range between 45 and 500 p. s. i. g. in the presence of 100 to 2000 cubic feet of hydrogen per barrel of said naphtha fraction at a liquid space velocity in the range of 1.5 to 12 v./v./hour to cause selective hydrogenation of said diolefins to the substantial exclusion of hydrogenation of the mono-olefins to form a hydrogenated product containing said organic sulfur compound and hydrogenation products of sulfur, treating said hydrogenated product with an aqueous solution of an alkali metal hydroxide to remove therefrom said organic sulfur compound and hydrogenated products of sulfur and recovering said treated product.

3. A method in accordance with claim 2 in which the solution of alkali metal hydroxide is an aqueous solution of sodium hydroxide.

4. A method for hydrogenating a cracked naphtha fraction boiling in the gasoline boiling range containing monoand diolefins wherein the diolefins are hydrogenated selectively which comprises adding to said naphtha fraction a caustic soluble organic sulfur compound selected from the class consisting of methyl mercaptan, ethyl mercaptan, the propyl mercaptans, the butyl mercaptans, benzene thiol, the methyl benzene thiols, the ethyl benzene thiols, 2,4 dimethyl- 1 benzene thiol, 2,5 dimethyl-l benzene thiol and 2,4,6 trimethyl-l benzene thiol, in an amount in the range from 0.1% to 1.0% by weight based on said naphtha, contacting the naphtha to which the organic sulfur compound has been added with a sulfur insensitive hydrogenation catalyst at a temperature in the range between 400 and 600 F. and at a pressure between 45 and 500 p. s. i. g. in the presence of hydrogen under conditions to cause selective hydrogenation of said diolefins to the substantial exclusion of hydrogenation of said mono-olefins to form a hydrogenated product containing said organic sulfur compound and hydrogenated products of sulfur, contacting said hydrogenated product with a solution of sodium hydroxide to remove therefrom said organic sulfur compound and hydrogenated products of sulfur and recovering said treated product.

5. A method for hydrogenating a cracked naphtha fraction boiling in the gasoline boiling range containing monoand diolefins which 7 comprises adding to said naphtha fraction a caustic soluble organic sulfur compound selected from the class consisting of methyl mercaptan, ethyl mercaptan, the propyl mercaptans, the butyl mercaptans, benzene thiol, the methyl benzene thiols, the ethyl benzene thiols, 2,4 dimethyl- 1 benzene thiol, 2,5 dimethyl-l benzene thiol and 2,4,6 trimethyl-l benzene thiol, in an amount in the range from 0.1% to 1.0% by weight based on said naphtha, contacting the naphtha to which the organic sulfur compound has been added with a nickel-tungsten sulfide hydrogenation catalyst at a temperature in the range between 450 and 550 F. and at a pressure between and 500 p. s. i. g. in the presence of hydrogen under conditions to cause selective hydrogenation of said diolefins to the substantial exclusion of hydrogenation of said mono-olefins to form a hydrogenated product containing said organic sulfur compound and hydrogenated products of sulfur, contacting said hydrogenated product with an aqueous solution of sodium hydroxide to remove therefrom said organic sulfur compound I and hydrogenated products of sulfur and recov- Name Date 2,143,078 Lyman et a1. Jan. 10, 1939 2,367,348 Harrington Jan. 16, 1945 2,392,579 Cole Jan. 8, 1946 2,413,312 Cole Dec. 31, 1946 2,511,453 Barry June 13, 1950

Claims (1)

1. A METHOD FOR HYDROGENATING A NAPHTHA FRACTION BOILING IN THE GASOLINE RANGE CONTAINING MONO- AND DIOLEFINS WHEREIN THE DIOLEFINS ARE HYDROGENATED SELECTIVELY WHICH COMPRISES ADDING TO SAID NAPHTHA FRACTION A CAUSTIC SOLUBLE ORGANIC SULFUR COMPOUND SELECTED FROM THE CLASS CONSISTING OF THE ALIPHATIC MERCAPTANS HAVING FROM 1 TO 4 CARBON ATOMS IN THE MOLECULE AND THE THIOPHENOLS BOILING UP TO 450* F. IN AN AMOUNT IN THE RANGE FROM 0.1% TO 1.0% BY WEIGHT BASED ON SAID NAPHTHA, CONTACTING THE NAPHTHA TO WHICH THE ORGANIC SULFUR COMPOUND HAS BEEN ADDED WITH A SULFUR INSENSITIVE HYDROGENATION CATALYST AT A TEMPERATURE IN THE RANGE BETWEEN 400* AND 600* F. AND AT A PRESSURE BETWEEN 45 AND 500 P. S. I. G. IN THE PRESENCE OF HYDROGEN UNDER CONDITIONS TO CAUSE SELECTIVE HYDROGENATION OF SAID DIOLEFINS TO THE SUBSTANTIAL EXCLUSION OF HYDROGENATION OF SAID MONO-OLEFINS TO FORM A

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