US3155605A - Reforming with a steamed platinumalumina catalyst in the presence of sulfur - Google Patents

Description

Nov. 3, 1964 w. H. LANG ETAL 3,155,605

REFORMING WITH A STEAMED PLATINUM-ALUMINA CATALYST IN THE PRESENCE OF SULFUR Filed Aug. 24. 1961 Reformer H2S'\ Scrubber 2l5 25 Full 3 Range 2 Nuphthu 2 Scrubber 2 l 1 vem l6 |8 22 J Pre- Neuter 20 I l9 1. X

a Reformer Recycle Gus INVENTO/PS. William H.Lcng

Donald M.Nace PoulB.Weisz ATTORNEY.

United States Patent 3,155,605 REFtiRMlNG WETH A STEAMED PLATINUM- ALUMFINA CATALYST EN THE PRESENCE 0F SULFUR William H. Lang, Wenonah, and Donald M. Nace, West Eeptford Township, Gloucester County, N.J., and Paul B. Weiss, Media, Pm, assignors to Socony Mobil Qil oinpany, inc a corporation of New York Filed Aug, 24, W61, er. No, 133,625 Glaims. (Cl. 208-49) The invention relates to improvements in catalytic reforming. More particularly, the present invention relates to improvements in catalytic reforming of naphthas in a combination process by separately reforming specified low boiling fractions under specific conditions in the presence of critical amounts of sulfur, separately reforming remaining high boiling fractions and combining the resulting products of the said two reforming operations to obtain improved yields of gasolines having high octane numbers.

In catalytic reforming of petroleum naphthas the following main hydrocarbon reactions occur: dehydrogenation of cyclohexanes to aromatics; dehydroisomerization of alkylcyclopentanes to aromatics; 'dehydrocyclization of paraffins and olefins to aromatics; isomerization of nparafiins to isoparafins; hydroisomerization of olefins to isoparatiins; isomerization of substituted aromatics; hydrodealkylation of aromatics; and hydrocracking of paraffins and cycloparaliins. Of the above reactions dehydrogenation of naphthenes to aromatics is the chief octane upgrading reaction. The dehydrogenation of cyclohexanes to aromatics over a supported platinum catalyst readily occurs without any substantial hydrocracking under normal reforming conditions; however, dehydroisomerization of alkylcyclopentanes to cyclohexanes to aromatics over a supported platinum catalyst requires increased temperature conditions over the cyclohexane to aromatics reaction which enhances the undesirable hydrocracking reaction. In the art, reforming processes are described wherein supported platinum catalysts are utilized in combination with many reaction variables to dehydrogenate simultaneously cyclohexanes and alkyl cyclopentanes to aromatics with a minimum amount of simultaneous hydrocracking of cycloparafiins to obtain high octane gasolines in economically attractive yields. Of particular interest, reference is made to US. 2,861,944 which describes a process wherein a methylcyclopentane fraction boiling chiefly in the range of about 140 F. to 180 F. is separately reformed over a standard supported platinum catalyst in the presence of sulfur, separately reforming the heavier naphtha fraction boiling in the range of about 180 F. to 400 F. under conventional' reforming conditions and combining the resulting products to obtain commercially attractive yields of high octane gasoline. ing process and other known reforming methods are adequate for the production of high octane gasolines, it is the ultimate aim to utilize a more efficient reforming process and provide improved yields of high octane gasoline over the known reforming methods.

It is the object of this invention to provide an efiicient naphtha reforming process which provides improved gasoline yields of high octane ratings. it is a further object of this invention to provide an improved process wherein a petroleum naphtha is readily upgraded to high octane gasolines utilizing economically attractive reforming conditions. These and other objects will become apparent to those skilled in the art by the further consideration of the following disclosures and appended claims.

A combination reforming process has been discovered which provides improved yields of high octane gasoline by initially fractionating a hydrocarbon naphtha having an initial boiling point of about 140 F. and an end Although the above described reformr Patented Nov. 3, 1964 "ice boiling point of about 400 F. into two fractions, i.e., a low boiling fraction boiling in the range from about F. to about 300 F. and containing at least about 20 mole percent alkylcyclopentanes and a high boiling fraction boiling the range from about 300 F. to about 400 F. The low boiling fraction is then separately reformed over a supported steamed platinum metal catalyst in the presence of critical amounts of sulfur under otherwise standard reforming conditions. The higher boiling fraction is pro-treated to lower and substantially remove the known catalyst poisons such as nitrogen, arsenic, sulfur, and the like, using conventional known pretreating methods such as passing said fraction over a commercial cobalt-oxide molybdena-alumina catalyst.

fter the pro-treatment step, the higher boiling fraction is then reformed utilizing conventional reforming condi tions. After the separate reforming of both the low and high boiling fractions, the resulting reformed products are combined to provide improved yields of high octane gasolines.

The hydrocarbon naphthas used in the process of this invention are those having an initial boiling point of about 140 F. and an end boiling point of about 400 F. containing substantial amounts of alkylcyclopentanes. To obtain the improvements in yields of high octane gasolines, it is essential that the low boiling hydrocarbon naphthas boiling in the range of about 140 F. to about 300 F. contain at least about 20 mole percent alkylcyclopentanes. Known typical naphthas containing the necessary amount of alkylcyclopentanes in the low boiling naphthas include Wilmington naphtha, Mid-Com tinent naphtha, among others.

To achieve the improvements by the process of this in vention, a reducible sulfur compound can be added to the low boiling hydrocarbon naphtha prior to reforming. The reducible sulfur compound will be hydrogenated to hydrogen sulfide in the reformer. Hydrogen sulfide itself can be added to the hydrogen stream or recycle stream of the reformer in amounts sufiicient to provide the desired sulfur content. Based on a weight percentage of the low boiling naphthas, charged sulfur concentrations of about .001 percent to about 0.7 percent, preferably .005 percent to 0.5 percent, will provide the improvements in yields of high octane gasoline of this process.

The use of controlled amounts of sulfur in the reforming process of the low boiling fraction is exceptional in its behavior since the presence of sulfur will only temporarily poison those sites of the platinum catalysts which produce the undesirable reactions obtained in reforming of naphthas. There are no permanent detrimental effects to the platinum catalysts in using sulfur. For instance, if higher platinum activity is required, the amounts of sulfur can be reduced and the activity of the platinum catalyst increases instantaneously. Correspondingly, if less platinum activity is desired, the amounts of sulfur present can be increased to obtain the instantaneous decrease of catalytic activity.

Typical reducible sulfur compounds which can be used in the process include, for example, the organic mercaptans, sulfides, disulfides, and heterocyclic sulfur compounds, having boiling points within and below the naphtha boiling range such as, tertiary-butyl mercaptan, tertiary-hexyl mercaptan, di-tertiary-butyl sulfide, di-normalbutyl sulfide; di-tertiary-butyl disulfide; di-tertiary-octyl disulfide; thiophene; and the like; and as described previously, hydrogen sulfide in the form of a gas. The optimum concentration of sulfur will depend on the composition of the naphtha charge stock (particularly the concentration of alkylcyclopentanes), the platinum activity of a particular catalyst used and the severity of the reforming operation.

The catalyst which can be used in the reforming process of the low boiling fraction can be any known type of supported platinum group metal catalyst used for reforming which has been specially steam-treated. The steaming treatment of the catalyst utilized in the process of this invention is a process where a conventional platinum metal catalyst such as platinum on alumina catalyst containing small amounts of halide is subjected to a stream of gas containing from about 50 to 100 mole percent steam for from about 2 to 72 hours. The steamed platinum metal catalyst can include those catalysts which are steamed for a duration of from 1 hour to as long as 3 days, preferably from about 1 hour to about hours, in a temperature range of about 700 F. to about 900 F. or include those catmysts steamed at higher temperatures from about 900 F. to about 1200 F. with steam alone or in the presence of an oxygen-containing inert gas such as air, oxygen alone and the like for a period of time ranging from about 1 hour to about 3 days, preferably for about 2 hours to about hours. Variations of the above-described steaming process can be used to produce the steamed catalyst. For example, oxygen plus steam can be passed over the catalyst for a period of time, then the catalyst can be steamed without oxygen for a period of time or modifications thereof. The purpose of the steaming of the above described catalysts is to lower the acidity of the platinum metal group catalyst by reducing the halide content therein. The steaming process reduces the acidity of the platinum metal catalyst not only by decreasing the chlorine content but also by decreasing the catalysts surface area. Reduction of acidity has the purpose of inhibiting substantially the undesirable reactions known to occur in reforming.

The term platinum metal as used throughout the specification and claims is meant to include any type of metal in the platinum series such as platinum, palladium, rhodium, osmium, iridium and ruthenium, as well as alloys or mixtures of these metals. The amount of the platinum metal on a support can range from about 0.01 percent to about 5 percent platinum metal, preferably from about 0.1 percent to about 2 percent by weight based on the total catalyst. The platinum metal portion of the catalyst can be incorporated into the catalyst support by impregnating or co-precipitating the ame with a suitable compound of platinum metal in accordance with procedures well known in the art, for example, platinum amine complex, potassium chloropiatinate, chloroplatinic acid, platinum sulfide, palladium sulfide, rhodium sulfide, platinum polysulfide and the like. The quantity of platinum compound used in the catalyst preparation will depend on the final concentration of the platinum metal desired. The catalyst support of the platinum metal catalyst can be any suitable carrier material known in the art. These carriers include those inorganic oxide gels capable of maintaining halides thereon such as, for example, alumina, silica, silica-alumina, zirconia, silica-Zirconia, magnesia, alumina-boria and the like. The preferred catalysts are those wherein the support or carrier is alumina having platinum deposited thereon and contain small quantities of halides such as chlorine, fluorine and bromine in the range of from about 0 to about 2.0 weight percent after platinum impregnation.

The higher boiling hydrocarbon naphthas, hereinbefore described, are separately reformed over untreated supported platinum group metal catalysts under standard reforming conditions in the substantial absence of sulfur in the naphtha hydrocarbon feed.

The conditions utilized in the process of this invention are the standard reforming conditions known to the art. The pressure in the reactors is maintained between about and about 1000 p.s.i.g., preferably in the range from about 100 to about 750 p.s.i.g.; the inlet temperature of the reforming reactor ranges from about 880 F. to 1000 F., preferably in the range of 900 F. to

970 F. The liquid hourly space velocity of the naphtha charge per volume of catalyst can range from about 0.1 to about 10, preferably in the range from 0.5 to 5. The molar ratio of hydrogen to hydrocarbon charge can range from about 2 to about 40, prefcrabl" in the range of about 3 to 20.

The conditions utilized in both reforming processes of this invention are the standard reforming conditions known to the art.

The process of the present invention is illustrated diagrammatically in the attached figure. A full range hydrocarbon naphtha having an initial boiling point of about F. and an end boiling point of about 400 F. enters the fractionator 12 through line 11. The fractionator 12 divides the hydrocarbon naphtha into a low boiling charge having a boiling range from about 140 F. to about 300 F. and a high boiling charge from about 300 F. to about 400 F. The high boiling charge flows through line 16 to the pre-heater 17 containing a cobalt oxide-molybdena-alumina catalyst to remove catalytic poisons such as nitrogen, arsenic, sulfur and the like. The product of the pre-treater 17 flows through line 18 to the stripping apparatus 19 to remove the volatile gases produced in the pre-treater. The pie-treated high boiling naphtha charge then flows through line 20 to the reformer 21 containing an untreated supported platinum metal catalyst. The reformer product flows through line 2?. to be combined with the product of the reforming operation of reformer 14 hereinbelow described. The low boiling naphtha flows through line 13 directly to the reformer 14 containing a steamed supported platinum metal catalyst. The sulfur component such as hydrogen sulfide used in this process can be added to line 13 or directly to reformer 14 to supply the necessary hydrogen sulfide content. A variation of the addition of hydrogen sulfide to reformer M is shown in the figure. In this variation, the hydrogen sulfide addition to reformer 14 can be supplied from the stripping apparatus 19 by flowing the gases such ammonia and hydrogen sulfide produced on the pre-treatment of the high boiling naphtha through line 23 through an ammonia scrubber to remove substantially all the ammonia. Th remaining hydrogen sulfide gas and minor reforming contaminants are then passed through line 25 to the hydrogen sulfide scrubber to remove the minor reforming contaminants and the remaining hydrogen sulfide can then be controlled by a vent or other appropriate means and used in such amounts so as to supply the required hydrogen sulfide content to reformer 14. The hydrogen sulfide, under the above-described conditions can be supplied to reformer 14 through line 27. The gasoline product leaves the reformer 14- through line 15 to be combined with the product of reformer 21. A variation of the above-described process can be used if the quantity of catalytic poisons in the low boiling naphthas is too high for a practical reforming operation. The full range naphtha can be first pre-treated and then fractionated into the low and high boiling naphthas.

The process of this invention may be carried out in any equipment suitable for reforming operations. It is highly desirable and obvious to use a sulfur resistant steel liner in the low boiling naphtha reformer but these restrictions are not necessary in the high boiling naphtha reformer. The process of this invention can be operated batohwise. It is preferable, however, and generally more feasible to operate continuously. Accordingly, the process is adapted to operations using a fixed bed of catalyst. Also the reforming processes can be operated using a moving bed of catalyst, wherein, the hydrocarbon flow may be concurrent or countercurrent to the catalyst flow. A fluid type of operation may also be employed.

An additional advantage of the process of this invention, other than the improved high octane gasoline yields, relates to the fact that where small and tolerable amounts of catalytic poisons are present in the low boiling naphthas, only the high boiling naphthas which may represent in the range of 25 to 75 weight percent of the full range nap'hthas are required to be pre-treated. This advantage represents a distinguishable, economical and commercial feature over the known reforming operations where the entire full range naphthas are required to be pre-treated. It is recognized, however, that this advantage is not available if large and detrimental quantities of catalytic poisons appear in the low boiling naphtha fraction.

The following examples will serve to illustrate the process of this invention without limiting the same:

EXAMPLE 1 A charge of 50 cc. of platinum on aluminum catalyst which contained 0.6 weight percent platinum and 0.7 weight percent chlorine was placed in a reactor. This charge was heated to 950 F. and processed four times with oxygen and/or steam by the following sequence: two cycles of /2 hour duration at 950 F. with oxygen saturated with Water at 200 C. followed by one cycle of a 4 hour duration with 100 percent steam at 950 F., and an additional cycle of a 6 hour duration with 100 percent steam at 950 F.

EXAMPLE 2 A Mid-Continent naphtha having an initial boiling point of about 150 F. and an end boiling point of about 250 F. was pre-treated at 700 F. over a cobalt of about 208 F. and an end boiling point of about 400 F. was pre-treated at 700 F. over a cobalt oxide-molybdena-alumina pre-treating catalyst, at 500 p.s.i.g. and 5 liquid hourly space velocity to remove the nitrogen derivatives. The resulting naphtha having an ARI. gravity of 53.9 contained 0.0004 percent sulfur. The composition of the naphtha was 31.0 weight percent paraffins, 52.5 weight percent monocycloparaffins (34 weight percent alkylcyclopentanes), 10.3 weight percent alkylbenzenes, and 6.2 weight percent olefin and dicyclo compounds. The octane number of this naphtha (ResearchA-B cc. TEL) was 83.8. The above pre-treated naphtha was reformed over a conventional platinum alumina reforming catalyst containing 0.6 weight percent platinum and 0.7 weight percent chlorine and a steamed platinum on alumina catalyst of Example 1. The reforming operation was carried out in a conventional fixed bed unit which used 75 cc. of catalyst under operating conditions of 500 p.s.i.g. pressure, a molar ratio of hydrogen to hydrocarbon charge of 10 and a liquid hourly space velocity of 2. The amounts of sulfur added to the naphtha charge varied as shown in the reforming results described in Table 11 below.

Table I! CONVENTIONAL PLATINUM ON ALUMINA CATALYST CONTAINING 0.6 WT. PERCENT PLATINUlW AND 0.7 WT. PERCENT CHLORINE [Sulfur content in naphtha charge-0.000l%] oxide-molybdena-alumina pre-treating catalyst at 500 p.s.i.g. and 5 liquid hourly space velocity to remove the 323; gg nitrogen and other catalytic poison derivatives. The re- Inlet Temp., F. (Research-l- Volume Gasoline, suiting naphtha contained 26 mole percent of alkylcyclo- 3 TEL) Percent Percent pentanes and negligible amounts of sulfur. The above a a 97.8 82.5 98.1 pre-treated naphtha was rerormed over a steamed plati- 100,7 7M 9Z1 num on alumina catalyst of Example 1. The reform- 103.1 67.8 86.5 ing operation was carried out in a conventional fixed 103'9 833 bed unit which used cc. of catalyst under operating conditions of 500 p.s.i.g. pressure, a molar ratio of hy- 40 [Sulfur contentmmphtha harge 031%] drogen t0 hydrocarbon charge of 10, and a liquid hourly space velocity of 2. The amounts of sulfur added to 8%; 2%? 22;? the naphtha charge varied as shown in the reforming 1034i results described in Table I below.

Table 1 0 Vol. Moles/ Moles Charged Inlet Gasoline Percent Addition of Sulfur to Temper- Octane 0 Naphtha, Wt. Percent ature, Number Gasoline Oyclo Aromat- 0 Total Total F. (R+3 cc. Yield Parafiius ios Paraftins Oyclics Ct-l- TEL) As demonstrated in the above example the addition of 0.06 weight percent of sulfur in the naphtha charge pro- STEAMED fg gflfi fi p g CATALYST vides a significant increase of almost 10 volume percent 65 [Sulfur contentmmphtha chargero'omlzl] of 0 gasoline yields over the naphtha Without any additional sulfur added. As heretofore described, the higher 9&0 824 99.3 boiling naphtha charge having an initial boiling point of p823 32. 3317) about 250 F. and an end boiling point of about 400 F. 1 5 is reformed separately using known reforming conditions. The combination of the reformed product of the low boiling fraction and the high boiling fraction provides increased yields of high octane gasoline. gg EXAMLE 3 89.1

A Wilmington naphtha having an initial boiling point The results of Table 11 indicate overall improvements in gasoline yields having octane numbers greater than 100 when utilizing a steamed platinum on alumina catalyst with amounts of 0.31 weight percent of sulfur added to the naphtha charge over the steamed catalyst with negligible amounts of sulfur present in the naphtha charge over the steamed catalyst and negligible amounts of sulfur (i.e., 0.0004%) in the naphtha charge. Significant improvements are also shown and demonstrated in the reforming of the naphthas over steamed platinum on alumina catalysts when compared to the untreated platinum on alumina catalyst, with or without added sulfur to the naphtha charge.

Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be resorted to, without departing from the spirit and scope of this invention, as those skilled in the art will readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.

What is claimed is:

l. A method for reforming a naphtha fraction containing allzyl cyclopentanes and boiling in the range of from about 140 F. to about 400 P. which comprises fractionating said naphtha fraction under conditions to concentrate substantially all said alkyl cyclopentanes in the tower boiling portion of said naphtha fraction for recovery from a higher boiling portion of the naphtr a fraction and reforming the low boiling naphtha fraction containing said alkyl cyclopentanes by contact under reforming conditions with a steamed platinum alumina catalyst in the presence of sulfur added in amounts ranging from about .001 to about 0.7 weight percent to convert said alkylcyclopentanes to aromatics.

2. A process for reforming a desulphurized naphtha hydrocarbon which comprises fractionating said naphtha hydrocarbon to obtain a low boiling naphtha fraction boiling in the range of from about 140 F. to about 300 F. and containing substantially all alkyl cyclopentanes concentrated therein from a higher boiling naphtha portion boiling up to about 400 F. reforming the higher boiling fraction in the absence of sulphur with a platinum reforming catalyst under reforming conditions, reforming the low boiling naphtha fraction in the presence of a severly steamed platinum alumina catalyst under reforming conditions in the presence of added sulphur in amounts f3 ranging from about .001 to about 0.7 weight percent based on the naphtha charge, and combining the reformed fractions of each step to obtain an improved high octane gasoline,

3. A method of reforming naphtha hydrocarbons containing alkyl cyclopentanes which comprises fractionating said naphtha hydrocarbons to obtain a low boiling naphtha fraction from a higher boiling naphtha fraction, said low boiling naphtha fraction containing at least about 20 mol percent of alkyl cyclopentanes, pretreating the higher boiling naphtha fraction to remove sulphur therefrom and thereafter reforming the higher boiling naphtha fraction with a platinum catalyst under reforming conditions, and reforming the low boiling naphtha fraction with a steamed platinum catalyst in the presence of sulphur added in amounts up to about 0.7 Weight percent based on the naphtha charge, and combining the reformed fractions to obtain an improved high octane gasoline.

4. The method of claim 3 wherein the sulphur content ranges from about .005 to about 0.5 weight percent based on the naphtha charge.

5. A method for reforming naphtha boiling range hydrocarbons containing at least about 20 mol percent nlltyl cyclopentanes which comprises fractionating said naphtha boiling hydrocarbons to obtain a loW boiling fraction containing alkyl cyclopentanes concentrated therein from a higher boiling naphtha fraction, desulfurizing the higher boiling naphtha fraction and then reforming with a platinum catalyst to produce high octane gasoline product, adding sulfur to the lower boiling naphtha fraction to provide a sulfur content in the range from about .001 to about 0.7 weight percent and thereafter reforming the low boiling naphtha fraction containing sulfur in the presence of a severely steamed platinum alumina catalyst to produce a high octane gasoline product.

References Cited in the file of this patent UNITED STATES PATENTS 2,642,383 Berger et al. June 16, 1953 2,763,623 Haensel Sept. 18, 1956 2,903,415 Bowles Sept. 8, 1959 3,005,770 Lutz Oct. 24, 1961 3,006,841 Haensel Oct. 31, 1961

Claims (1)

1. 2. A PROCESS FOR REFORMING A DESULPHURIZED NAPHTHA HYDROCARBON WHICH COMPRISES FRACTIONATING SAID NAPHTHA HYDROCARBON TO OBTAIN A LOW BOILING NAPHTHA FRACTION BOILING IN THE RANGE OF FROM ABOUT 140*F. TO ABOUT 300* F. AND CONTAIING SUBSTANTIALLY ALL ALKYL CYCLOPENTANES CONCENTRATED THEREIN FROM A HIGHER BOILING NAPHTHA PORTION BOILING UP TO ABOUT 400*F. REFORMING THE HIGHER BOILING FRACTION IN THE ABSENCE OF SUPHUR WITH A PLATINUM REFORMING CATALYST UNDER REFORMING CONDITIONS, REFORMING THE LOW BOILING NAPHTHA FRACTION IN THE PRESENCE OF A SEVERELY STEAMED PLATINUM ALUMINA CATALYST UNDER REFORMING CONDITIONS IN THE PRESENCE OF ADDED SULPHUR IN AMOUNTS RANGING FROM ABOUT 0.001 TO ABOUT 0.7 WEIGHT PERCENT

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