US2717861A - Selective hydrogenation process - Google Patents

Description

United States Patent 2,717,861 SELECTIVEHYDROGENATION PROCESS Peter K. Baumgarten, Newark, DeL, and Edward J Hoffmann and Edward F. Wadley,'-Baytown, Tex., asslgnors, by mesne assignments, to-Esso Research .andEngmeering Company, Elizabeth,5 N. J., a corporation of Delaware Application August-.11, 1954, Serial No. 449,128 7 Claims. (CL 19636) The present invention is directed-to aselective'hydrogenation process. More particularly, the invention is directed to the hydrogenation of naphthas containing olefins and di-olefins, such as cracked naphthas,-=u-nder conditions such that the di-olefins are selectively hydrogenated.

This application is a continuation-impart of Serial No. 182,648, filed September 1, 1950, for 'Peter K; Baumgarten, 'Edward J. Hoffman, and Edward -Wadley, entitled Selective *Hydrogenation Process, now U. S. Patent No. 2,694,671.

Thepresent inventionwill be: described. as a hydrogenation process in which a naphtha, such as-a:cracked naphtha, containing monoand di-olefins is-hydrogenated to improve the quality thereof for use as a. motor fuel. The steps in the hydrogenation process of-thespresent invention involve contacting the naphtha witha sulfur insensitive catalystata temperature in the rangewbetween 350 and 650 F. andat a pressure in therange'between 15 and 500 pounds per square inchwgaugeandat a liquid space velocity in the range between 1 and..20iv./v./hour in the presence of a sufiicientamount1of1avhydrogencontaining gas containingat least 10% hydrogentozmaintain a molal ratio ofgas to naphtha of 1:1 for afixedset of conditions within the ranges of temperatures,.pressures, and space velocities. given to obtain maximum. conversion of conjugated di-olefins and to forma product suitable for use as a. motor. fuel. 'Finally, the product is recovered from contact with the catalystandzmay be treated subsequently prior to use as a motorlfuel.

The sulfur insensitive. catalyst employed in the practice of the present inventionimay be a sulfideof a heavy metal, such as nickel, molybdenumand tungsten. Mixtures of these catalystsmay be employed, such as'rnixtures of nickel sulfide and tungsten sulfide. Other molybdenum-containing catalysts suchas molybdenunr oxide, molybdenum sulfide,.and the like, may. be used. The catalyst may be used as such-or may. be'depositedon a suitable carrier material, such as a porousadsorbentzinert material, such as clay, kieselguhnalumina and theslike.

The hydrogen-containing gas involved in the practice of the present invention should contain atleast 10% of hydrogen and may contain up to 100% of hydrogen. --As a preferred range the hydrogen-containing.gas willzcontain from 50 to 100% of hydrogen. The other-material present in the gas should be inert from the standpoint of reacting with the cracked naphtha being hydrogenated or deleteriously affecting the catalyst. activity. :.=Such.;inert material may be C1 to C paraffinic hydrocarbons,.flue gas and the like.

While the space velocityemployed in the =practice of the present invention may range from 1 to 20 v.-/v./hour, a preferred range is from 3 to 8 v./v./hour.

As stated, temperatures may range from 350tt0 650 :the foregoing conditions is removed'from the catalyst and may be subsequentlytreated.prionto .result from the hydrogenation reaction.

2,717,861 Patented Sept. 13, 1955 F. with temperatures preferably in the range from 500 to 600 F. Pressures ordinarily may range from 15 to 500 pounds per square inch gauge with a preferred range from 50m pounds per square inch gauge.

The hydrogenated naphtha. or. product produced. under contact with use as a motor fuel. Such treatments may include-distillation; to recovera desired; fraction, and/or-washing; the hydrogenated productwithaa solution of aeausfiqalkali .such as an aqueous or alcoholicsolutionof sodium hydroxide having a gravity in the rangebetweenS and'.30 B. to remove hydrogen sulfide and other caustic soluble sulfur compoundswhich may be present in the gfeeda or h hyd ogenated product may be treated with the alkaline solution prior or subsequent to the distillation step to recover motor fuel. constituents.

The present invention is basedon the discovery -that for any given set of conditions of temperatures, pressures and space velocities in the ranges set out above when employing a hydrogen-containinggas containing, at least 10% hydrogenthat itis possible toobtain maximum conversion of conjugated .di-olefins .with a.low.-conversion of mono-olefins if a ratio of gas to naphtha being hydrogenated of 1:1 isma-intained. This ratio of 1:1 is independent of the concentration of hydrogen in-the gas employed in the hydrogen medium and it is the only ratio that will permit maximum conversion of conjugated diolefins when operatingunder any fixed set of conditions Withinthe ranges given; for example, for a given set of conditions of temperature, pressure and space velocity by maintaining aratio of hydrogen-containing gas to naphtha of 1:1 only is it possible t o ob t.ain,maximum conversion of conjugated di-olefins. ---Increasing the gas to oil ratio increases monowlefin conersion wi a decrease in conjugated di-olefin content.

The reason that it is important to remove the maximum amount of conjugated di-olefins under a given set of conditionswhile minimizing the removal.-.of-.monoolefins is that the di-olefins are contributors to the formation of gums and engine deposits on use of .cracked-naphthas, in motor fuels. eWhile-removal of theconjugated 'di-olefins may be achieved-by subjecting cracked naphtha also result .in removal of mono-olefins by conversion ofparaflins. h-Whenstraight chain mono-olefins are converted to normal parafiins, the octane numbers of the cracked naphthaare seriously impaired. The present invention eliminates thetobjectionable features of the prior'art processesin .that. thedifollowing series, of runs in.whieh. a. naphtha from a thermal cracking operation was contacted with a nickel sulfide-tungsten sulfide catalyst at atemperatureofv500 F. and at a pressure of 100 pounds per square inch gauge employing. gas from a commer ial hydroforming ,unit containing approximately 72% hydrogen. gThemaphtha was charged to contact WithLthe catalyst at, a;space.v e1ocity of 6 v./v./hour. The results of these runs are shown in the following table:

From the foregoing results in Table I, it will be seen that at a ratio of 1 mole of gas per mole of naphtha that 88% of the conjugated diene-olefin content is converted while at the same ratio only 17% of the total olefin content is removed indicating that the di-olefins were selectively hydrogenated. It will be noted that it is only at a ratio of 1:1 that a maximum conversion of di-olefins takes place while minimizing conversion of mono-olefins.

Similar values may be obtained when contacting a cracked naphtha from a thermal cracking unit under conditions such as those represented in the foregoing example. Exemplary of the results obtainable at lower and higher space velocities are the data presented in Table II in which comparisons are made between space velocities of 3 and 12 v./ v./ hour under similar conditions to those of the preceding example:

1 Conjugated.

The data presented in Table II show the same unexpected results as the data presented in Table I, namely, that at a ratio of 1:1 mole of hydogcn-containing gas per mole of naphtha, maximum conversion of di-olefins takes place with a low conversion of mono-olefins showing that the mono-olefins are substantially unaffected at this ratio.

The data presented in Tables I and II are also presented graphically in the single figure which is a plot of conversion against the mole of gas per mole of naphtha. From an examination of this figure it will be seen that at a ratio of 1:1 maximum conversion of di-olefins is obtained irrespective of the space velocity of the feed in contact with the catalyst While at the ratio of 1:1 the conversion of mono-olefins has not reached a maximum. It will be further noted from an examination of the curves that when a ratio in excess of 1:1 is employed the conversion of di-olefins drops otf while the conversion of mono-olefins increases. It may be concluded, therefore, from these results that only at a ratio of 1:1 are the beneficial results of the present invention obtained.

It will be noted that it is the ratio of hydrogen-contain ing gas to naphtha which is important and not the content of hydrogen contained in the hydrogen-containing gas provided the amount of hydrogen contained therein. is above Referring again to the data in Tables I and II it will be clear that at a ratio of 1:1 the amount of hydrogen in cubic feet per barrel of naphtha is less than that employed at higher ratios of gas to naphtha. Thus it is important in the practice of the present invention that the ratio of hydrogen-containing gas to naphtha be: maintained at 1:1 for a given set of operating conditions.

To illustrate the effect of hydrogen purity additional runs were made in which a naphtha from a thermal cracking operation was contacted with a nickel sulfide-tungsten sulfide catalyst at a temperature of 500 F. and at a pressure of pounds per square inch gauge, employing a gas containing 99.7% hydrogen and about 0.3% nitrogen. This gas was carefully purified to exclude oxygen. The aforesaid naphtha was contacted with the catalyst at a space velocity of 6 v./v./hour. The results of these runs are shown in Table III:

It will be seen from the results of the runs presented in Table III that a ratio of 1.02 mols of gas per mol of naphtha 93% of the conjugated diene olefin were converted with 24% conversion of the total olefins. At a ratio of 2.4 mols of gas per mol of naphtha the total olefin conversion was increased while the conjugated dienc olefin conversion decreased slightly. It will be noted that the amount of hydrogen in the second run was over double the amount of that employed in the first run.

While the present invention has been described and illustrated by reference to a naphtha from a thermal cracking operation, it will be apparent to the skilled. workman that the invention is not restricted to ther-- mally cracked naphthas. The invention will apply equal-- ly to naphthas from catalytic cracking operations and reformed naphthas. As a general statement, the invention may be preferably applied to stocks boiling in the gasoline and naphtha boiling range but may be applied to fractions having a boiling point up to 700 F.

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

l. A method for hydrogenating a naphtha containing monoand di-olefins to improve the quality thereof for use as a motor fuel which comprises contacting said naphtha with a molybdenum-containing catalyst at a tem perature in the range between 350 and 656 F. at a pressure in the range between 15 and 500 pounds per square inch gauge and at a liquid space velocity in the range between 1 and 20 v./v./hour in tie presence of a sufficient amount of a hydrogen-containing gas containing at least 10 mol percent hydrogen to maintain a mol ratio of gas to naphtha of 1:1 for a fixed set of conditions within the ranges of temperatures, pressures and space velocities given to obtain maximum selective conversion of conjugated di-olefins at low mono-olefin conversion and to form a product suitable for use as a motor fuel and recovering said product.

2. A method in accordance with claim 1 in which the molybdenum-containing catalyst is molybdenum sulfide.

3. A method in accordance with claim 1 in which the molybdenum-containing catalyst is molybdenum oxide.

4. A method for hydrogenating a cracked naphtha containing monoand di-olcfins to improve the quality thereof for use as a motor fuel which comprises contacting said cracked naphtha with a molybdenum-containing catalyst at a temperature in the range between 356 and 650 F. at a pressure in the range between 15 and 500 pounds per square inch gauge and at a liquid space velocity in the range between 1 and 20 v./v./hour in the presence of a suflicient amount of a hydrogen-containing gas containing at least 10 mol percent hydrogen to maintain a mol ratio of gas to cracked naphtha of 1:1 for a fixed set of conditions within the ranges of temperatures, pressures and space velocities given to obtain maximum selective conversion of conjugated di-olefins at low monoolefin conversion and to form a product suitable for use as a motor fuel and recovering said product.

5. A method for hydrogenating a cracked naphtha containing monoand di-olefins to improve the quality thereof for use as a motor fuel which comprises contacting said cracked naphtha with a molybdenum-containing catalyst at a temperature in the range between 500 and 600 F. at a pressure in the range between 60 and 300 pounds per square inch gauge and at a liquid space velocity in the range between 3 and 8 v./v./hour in the pres ence of a sufiicient amount of a hydrogen-containing gas containing at least 10 mol percent hydrogen to maintain 21 mol ratio of gas to cracked naphtha of 1:1 for a fixed set of conditions within the ranges of temperatures, pressures and space velocities given to obtain maximum selective conversion of conjugated di-olefins at low monoolefin conversion and to form a product suitable for use as a motor fuel and recovering said product.

6. A method in accordance with claim 5 in which the molybdenum-containing catalyst is molybdenum sulfide.

7. A method in accordance with claim 5 in which the molybdenum-containing catalyst is molybdenum oxide.

No reference cited.

Claims (1)

1. A METHOD FOR HYDROGENATING A NAPHTHA CONTAINING MONO- AND DI-OLEFINS TO IMPROVE THE QUALITY THEREOF FOR USE AS A MOTOR FUEL WHICH COMPRISES CONTACTING SAID NAPHTHA WITH A MOLYBDENUM-CONTAINING CATALYST AT A TEMPERATURE IN THE RANGE BETWEEN 350* AND 650* F. AT A PRESSURE IN THE RANGE BETWEEN 15 AND 500 POUNDS PER SQUARE INCH GAUGE AND AT A LIQIUD SPACE VELOCITY IN THE RANGE BETWEEN 1 AND 20V./V./HOUR IN THE PRESENCE OF A SUFFICIENT AMOUNT OF A HYDROGEN-CONTAINING GAS CONTAINING AT LEAST 10 MOLE PERCENT HYDROGEN TO MAINTAIN A MOL RATIO OF GAS TO NAPHTHA OF 1:1 FOR A FIXED SET OF CONDITIONS WITHIN THE RANGES OF TEMPERATURES, PRESSURES AND SPACE VELOCITIES GIVEN TO OBTAIN MAXIMUM SELECTIVE CONVERSION OF CONJUGATED DI-OLEFINS AT LOW MONO-OLEFIN CONVERSION AND TO FORM A PRODUCT SUITABLE FOR USE AS A MOTOR FUEL AND RECOVERING SAID PRODUCT.

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