US3347777A - Reforming of paraffinic naphthas - Google Patents

Description

Oct 17, 1967 F. E. DAVIS, JR

REFORMING OF PARAFFINIQ NAPHTHA-S 2 Sheetshet l Filed March 30, 1966 EEQUZ 25:05@ D 92@ 555515@ E@ E S E 552055 2m;

United States Patent O Oil Corporation, a corporation of New York Filed Mar. 30, 1966, Ser. No. 538,703 Claims. (Cl. 208-65) This is a continuation-in-part application of application Ser. No. 373,668, tiled June 9, 1964, now abandoned.

The present invention relates to a method of reforming paraffin rich naphthas and more particularly relates to the method of improving C5-lreformate product yields when reforming paraflinic naphthas. In another aspect the present invention relates to correlating processing conditions in a relatively dry reforming operation with a limited amount of platinum reforming catalyst in the first reactor to improve reformate yields.

It is an object of this invention to provide an improved method of reforming hydrocarbon.

A further object of this invention is to provide an imroved method for reforming parailinic hydrocarbon.

Another object of this invention relates to dening the method of obtaining increased yields of C-freformate product over that obtainable heretofore from a paraflin rich naphtha feed of relatively low naphthene content.

Other objects and advantages of this invention will become more apparent from the following discussion.

It has now been discovered that when reforming parafflnic naphthas at pressures of about 200 p.s.i.g and higher elevated pressures that the amount of platinum-group metal reforming catalyst charged to the first reaction zone of a plurality of reaction Zones can be correlated with the moisture level of the reforming operation as measured at the reactor iniluent in an effective way to obtain substantial increases in yield of C5 and heavier reformate product having an octane rating of at least 100 (R4-3 cc.) from paraln rich naphtha feeds.

The foregoing inventive concept is clearly supported by the data and curves of FIGURES 1 and 2 hereinafter presented and discussed.

FIGURE 1 is a diagrammatic representation of data obtained in the investigation which shows the platinum reforming yield improvement with partial catalyst fill at different inuent moisture levels when charging a paraffinic naphtha.

FIGURE 2 is a diagrammatic representation of data obtained which shows by a family of curves the significant improvement in yield one can obtain when processing a paralnic feed and correlating the catalyst fill in the first From the foregoing description of the naphtha feeds, it iS clearly evident that the naphthas were paralln rich naphthas containing at least 60 percent by volume of parains. It is also significant to note that the volumes of naphthenes and aromatics in the feeds were relatively low with the upper limit of naphthenes being below about 25 Volume percent.

Examination of the data forming FIGURE 1 shows that at a moisture level as high as about 100 p.p.m. mole in the reactor influent, an increase in yield of only about 1 to 1.5 percent of C5 and heavier reformate was obtained when the first reforming reactor of a three reactor reforming process is charged with from about 2 to about 5 tons of platinum-group metal reforming catalyst. However, the yield of C5 and heavier reformate can be increased to a value above about 5 percent by the combination of maintaining the concentration of water in the influent below about 32 p.p.m. mole and preferably as low as about 4 ppm. based on the feed.

The curves presented in FIGURE 2 further establish among other things that, significant improvements can be realized when reforming a paraflinic naphtha at an elevated pressure in the presence of hydrogen and a platinumgroup metal catalyst under relatively low moisture conditions as measured at the influent to the first reactor of the reforming Zones. That is, the curves show that the yield of C5 and heavier reformate increases as the concentration of Water in the influent decreases and this yield improvement is further enhanced as the amount of catalyst charged to the first reactor is maintained less than 10 tonS and preferably less than 6 tons per 10,00() barrels of naphtha treated per day. The curves of FIGURE 2 clearly establish that operating under substantially desiccated conditions less than about 40 ppm. mole water in the first reactor influent, the amount of catalyst charged to the first reactor should preferably be no higher than about 6 tons per 10,000 barrels of naphtha treated per day to realize a significant increase in the yield of C5 and heavier reformate product.

It is to be noted that all the data presented are based on reactor influent moisture levels and these will generally be slightly higher than if the moisture level were determined in the eflluent from the reactor. However, because of the catalyst characteristics and effects of moisture thereon, it is preferred that the moisture be controlled on the influent to the first reactor.

TABLE I reactor and moisture content of influent. C i. Yield Improvement Rpm. H20 Tons Catalyst per In one embodiment of this invention, the reforming con- Reactor Innuent 10,000 b./`s.d. ditions employed were as follows: E- E Pressure: 500 p.s.i.g. 2 4 10 Catalyst: 0.6 percent by weight platinum; 0.7 percent gig by weight chlorine supported on alumina base. 50 9.0 Parailin -rich naphtha feed identified in FIGURE 1 and 75g gig below were reformed to provide the data for developing 6.0 Curves A and B of FIGURE l. The feed was a fraction 30 of Kuwait Naphtha boiling in the range of about F. 3 4 g, 9 up to about 365 F. Naphtha treated to produce curve C 60 gg Si? of FIGURE 1 was a 220 to 380 F. boiling range Kuwait 50 7. 5 naphtha fraction. The compositions of the aforesaid naph- (35: g5 thas are given below: 4 4 8.05 ii ti 65 50 4.' 4 190 to 36e F. 220 to 389 F. 5 4 5 8 Kuwait Kuwait 32 4. 4 Naphthenes, percent vol 22 24 5' 5; 4 2- 5 Paraflins, percent vol 67 64 70 Aromatics, percent V01 11 12 In? aseequal distribution of catalyst-100 ppm. mole H2O in Reactor The numerical values presented in Table I above and the curves of FIGURES 1 and 2 establish (A) that an increase in yield of C and heavier reformate can be obtained from paraflinic naphthas when the amount of platinum-group metal reforming catalyst charged to the first reaction zone is only a small fraction or portion of the total amount of catalyst in all reactors of the reforming system and the amount of catalyst employed is a function of the concentration of water in the influent to the reactor as maintained at different values below 100 ppm.; (B) the higher the moisture content of the influent, the lower the amount of catalyst one should maintain in the first reactor to obtain increased yields in the range of 2 to 6 percent of C54- reformate product; (C) to obtain increased C54- reformate yields substantially greater than about 4 percent, the final influent to the first reactor should contain substantially less than about 40 parts per million (ppm.) of water when the catalyst fill in the first reactor is less than 6 tons per 10,000 barrels of feed and (D) to obtain a maximum increase in yield of C5 and heavier reformate from a paraflin rich naphtha the moisture content of the inuent should not be above about 4 ppm. when the catalyst loading is less than 6 tons per 10,000 barrels/ day of feed. Therefore, it is preferred that the moisture content of the influent to the first reactor be less than about 40 ppm. when the charge of platinumgroup metal reforming catalyst in the first reaction zone is less than about 6 and preferably less than 5 tous per 10,000 barrels of parafiinic feed treated per day to obtain a C5 yield improvement of at least about 4 volume percent.

The preferred reforming catalyst employed in the method of this invention comprises a platinum type reforming catalyst having from about 0.35 to about 0.6 percent by Weight of platinum and from about 0.4 to about 0.7 percent by Weight of halogen, such as chlorine, supported on a high surface area base of at least about 100 square meters per gram as obtained by use of an eta alumina base. A platinum reforming catalyst of this kind weighs of the order of about 43 pounds per cubic foot and hence a LlZ-gallon barrel having a capacity of about 5.61 cubic feet contains about 241 pounds of catalyst. From this, it may be determined that the liquid hourly space velocity in the first reactor may be in the range of from about 6 to about 25 and preferably from about 8 to about 17 barrels of paraflinic feed per barrel of catalyst in the first reactor. This is approximately equivaient to from about 2 to about 8 and preferably from about 3 to about 6 tons of catalyst per 10,000 b./s.d. of naphtha feed. The remaining two reactors in a three reactor reforming unit may be charged equally or unequally with the balance of the catalyst required to cornplete the reforming operation.

In a particular embodiment, the present invention relates to reforming a 190 to 365 F. paraffin rich Kuwait naphtha after decontamination in the presence of hydrogen with a hydrogenation catalyst havin hydrodesulfuriration and hydrodenitrogenization capabilities. In this embodiment decontamination of the naphtha feed is accomplished with a mixture of oxides of cobalt and molybdenum on alumina support at a pressure of at least about 500 p.s.i.g., a temperature in the range of from about 675 to about 800 F., a liquid hourly space velocity in the range of from about 0.5 to about 5.0, employing at least about 500 cubic feet of hydrogen per barrel of naphtha.

The hydrodecontaminated naphtha treated within the above conditions had the following composition:

Paraffins, volume percent 67 Naphthenes, volume percent 22 Aromatics, volume percent 11 Sulfur, p.p.m. by weight 4 Nitrogen, ppm. by weight 1 Arsenic, parts/ 9 2 In the method of this invention, the reforming unit may comprise three or more reactors in series flow arrangement with a heater preferably up-stream of each reactor to overcome temperature drop encountered in the system. The first or lead reactor R1 is charged with less than about 6 tons but greater than about 2 tons of particleform solid platinum-type reforming catalyst per 10,000 b./s.d. of naphtha charge. As suggested above, the catalyst comprises about 0.6 percent by weight of platinum and about 0.7 percent by weight of chlorine on an etaalumina base. A second reactor R2 and a third reactor R3 may be employed with or without a fourth reactor R4 arranged in parallel or series flow with the third or final reactor R3.

In one particular arrangement the reactors are charged with about 44 tons of the reforming catalyst. That is, in a three-reactor system, the total catalyst charge may be as high as about 50 tons of catalyst when employing as high as 6 tons of catalyst in the first reactor. However, as indicated hereinbefore, it is contemplated employing no more than about 4 or 5 tons of catalyst in the first reactor per 10,000 barrels per stream day of paraftinic hydrocarbon feed.

To maintain the relatively dry or desiccated conditions required in the method of this invention, paraffinic hydrocarbon feed is dried by any suitable manner, such as for example, by fractionation, by contact with aluminosilicate molecular sieve material and by contact with other well-known drying agents. The hydrogen or hydrogencontaining gas such as hydrogen rich recycle gas is also subjected to a drying treatment by contact with for example, molecular sieve absorbent material having an average pore size of 4 or more Angstroms. By feeding a relatively dry parafiinic hydrocarbon feed and hydrogencontaining gas to the reforming operation, the moisture content of the influent to the first reactor R1 may be maintained at substantially any desired moisture level below about ppm. as desired for practicing this invention.

The paraffin rich hydrocarbon feed and at least the recycle gas dried to a desired low value are mixed to provide a reactant mixture having a hydrogen to hydrocarbon mole ratio in the range of from about 4 to about 20 and preferably from about 6 to about l0 moles of hydrogen per mole of hydrocarbon. The dried reactant mixture is heated either separatetly or as a combined stream in a combination of heating steps to provide a temperature at the vapor inlet of each reactor in the range of from about 900 F. to about 980 F. When employing virgin catalyst or freshly regenerated catalyst and an overall liquid hourly space velocity of about 1 to produce C5 and heavier reformate having an octane rating (R4-3) of 104, the temperature of the reactant mixture at the vapor inlet of the first reactor will be about 945 F.

In the method of this invention the heated reactant mixture is passed downwardly through a first reactor R1 in contact with a solid platinum-type reforming catalyst selected from an amount based on the influent moisture content to be tolerated as shown by FIGURE 2 in the range of from about 2 to about 6 tons of catalyst per 10,000 barrels per day of naphtha feed. The effluent obtained from the first reactor is thereafter suitably heated to provide a desired influent temperature at the inlet of a second recator, R2. However, the temperature of the reactant passed to the second reactor may be the same as or higher than the reactant inlet temperature to reactor R1 but usually the reactant inlet temperature to the second reactor will be at least as high as the inlet temperature to reactor R1.

`ln one particular embodiment, the catalyst is distributed substantially equally in reactors R5 and R3 of a three reactor system. Accordingly, in this particular embodiment each of reactors R2 and R5 is charged with about 22 tons of catalyst (at 241 pounds per barrel. This is equivalent to about 183 barrels of the aforesaid platinum reforming catalyst) to provide a total of about 44 tons of catalyst in the two reactors. Therefore, a three reactor reforming system processing about 10,000 barrels per day of naphtha feed would be provided with up toabout 6 tons of catalyst in the first reactor R1 to provide a total catalyst inventory of about 50 tons.

The eflluent obtained .from reactor R1 is usually caused to flow downwardly through reactor R2 in contact with a platinum-type reforming catalyst therein to the vapor outlet thereof. The effluent of reactor R2 is then passed to the vapor inlet of reactor R3 at a temperature which is usually the same as, but may be higher or lower than the reactant inlet temperature o-f reactors R1 and R2. The efiluent obtained from the second reactor is caused to flow downwardly through reactor R3 in contact with a platinum-type reforming catalyst therein to the vapor outlet thereof. The eliluent of reactor R3, designated the final effluent and comprising hydrogen, C1 and heavier hydrocarbons including reformate product is passed from reactor R3 through one or more cooling steps. The final eflluent is cooled, for example, by indirect heat exchange with parafi'inic hydrocarbon feed and recycle hydrogen rich gas in one or more separate heat exchange steps prior to being passed to a suitable pressure separator for separation of a hydrogen rich recycle gas from ref-ormate product material. The uncondensed final effluent comprising hydrogen and C1 and C3 hydrocarbons, designated reformer hydrogen rich gas, is separated from the condensed final reformate effluent comprising C4 and heavier hydrocarbons, designated raw reformate.

Since the reforming reaction generally produces more hydrogen than required for recycle thereto, a minor portion of the uncondensed hydrogen rich efiluent can be diverted to other hydrogenation processes as is well known in the art. The hydrogen rich reformer gas with or without treatment to remove low boiling hydrocarbons is recycled in an amount sufficient to maintain a hydrogen to paraf- -fnic hydrocarbon feed mole ratio in the range of from about 4 to about 20 and preferably from about 6 to about moles of hydrogen per mole of parafiinic hydrocarbon feed passed to the first reactor. Generally speaking, it takes from about 0.15 to about 0.20 ton of an aluminosilicate molecular sieve material per 1000 `standard cubic feet per minute of reformer recycle gas to provide a suitable dried reformer gas, containing not more than from about l to 2 p.p.m. (by volume) of water.

The relatively dry hydrogen rich recycle gas is passed from the drier (usually there are at least two driers, one on-stream while the other is being regenerated) to the first of the series of reforming reactor wherein it is combined with the hydrodecontaminated paraffinic hydrocarbon feed of low moisture content to form a naphtha-hydrogen charge mixture of a desired moisture content as hereinbefore discussed.

The condensed final reformate efiluent comprising C4 and heavier hydrocarbons separated from hydrogen rich recycle gas and designated raw reformate is thereafter fractionated in suitable recovery equipment to obtain a C4 and lighter fraction, a C5 to 380 F. reformate product fraction, and a 380 F. reformate bottoms fraction. The C5 and heavier reformate fractions are passed to storage or suitable gasoline blending facilities. Additives such as de-icers and anti-knock agents may be combined therewith as required.

It is to be understood that the solid particle-form platinum-type reforming catalyst should be dried to a low moisture level before contacting the catalyst with the paraflinic hydrocarbon feed.

Those skilled in the art will recognize that the foregoing description is particularly directed to methods of reforming paraflinic hydrocarbon feeds under conditions of low moisture content which are preferably less than about ppm. of water, as determined for the influent to the -first reforming reactor so that the concentration of water in the influent and the catalyst fill in tons in the first reactor are correlated to optimize the yield of C5| reformate from the paraflinic feed as shown in FGURES 1 and 2. Pressures in the range of from about 200 to about 1200 p.s.i.g. and preferably not substantially above about 600 p.s.i.g. may be employed with advantage in the first contact zone in accordance with this invention. Generally, it is preferred to use as low a pressure as possible since significant utility savings can be realized at low pressure and particularly pressures less than about 400 p.s.i.g.

A hydrogen to hydrocarbon mole ratio in the range of from about 4 to about 20 and preferably from about 6 to about 10 moles of hydrogen per mole of pa'raflinic rich naphtha feed may be used to advantage at vapor inlet temperature in the range of from about 900 F. to about 980 F. to produce C5 and heavier reformate having an octane rating (R-l-3) of at least 100. Furthermore, as shown by the figures, the concentrations of water in the influent to the first reactor should 'be maintained as low as possible to achieve the significant improvements in the reformate product yields by this invention and the lower the influent moisture content and the smaller the amount of catalyst charged to the rst reforming reactor below the 6 tons basis the greater the increase in yield of C5 and heavier reformate product one can obtain.

Having thus provided a general `description of the improved method of this invention and presented data in support thereof, it is to be understood that no undue restrictions are to be imposed by reason thereof except as defined by the following claims.

I claim:

1. A method for reformin-g a paraflin rich naphtha feed which comprises contacting a paraflin `rich naphtha feed with a platinum group reforming catalyst under reforming conditions of temperature and pressure wherein the moisture content of the influent to the first reactor and catalyst loading of the first reactor of a multiple reactor reforming process is correlated in accordance with the curves of FIGURES 1 and 2 to achieve at least a 2 volume percent yield improvement in C5-lreformate yields.

2. The method of claim 1 wherein the naphtha feed comprises at least 60 percent of parafiinic hydrocarbons.

3. The method of claim 1 wherein the temperature of the influent is maintained in the range of from about 900 to about 980 F. and the reforming pressure is maintained in the range of from about 200 to about 1200 p.s.i.g.

4. The method of claim 1 wherein the reforming pressure is maintained below about 600 p.s.i.g.

5. The method of claim 1 wherein the influent to the first reforming reactor has a moisture content maintained below about 100 ppm. moles and the catalyst loading is not greater than about 6 tons per 10,000 b./s.d. of naphtha feed.

6. The method of claim 1 wherein the influent to the first reactor has a moisture content less than about 50 p.p.m. mole and the catalyst loading therein is selected on the basis o-f the curves presented in FIGURE 2 to obtain a volume percent increase in C5| reformate of at least about 4.

7. The method of claim 1 wherein the moisture content of the influent to the first reactor and the amount of catalyst employed therein is selected from the curves of FIG- URE 2 to maximize the yield improvement in C5| reformate product.

8. The method of claim 1 wherein the amount of catalyst in the first reactor is a small fraction of the total catalyst inventory in a three reactor reforming system and is selected on the basis of the correlation established by FIGURES 1 and 2 to achieve a yield increase in C5-lreformate product greater than `about 2 volume percent.

9. The method of claim 1 wherein the reforming pressure is not substantially above about 500 p.s.i.g., the

7 8 amount of platinum reforming catalyst in the second and References Cited third reactors is substantially equivalent and the amount UNITED STATES PATENTS of catalyst employed in the first reactor 1s less than about 6 tons per 10,000 b./s.d. of naphtha charge While main- 2346737 7/1960 Poms 20S-65 taining the moisture content of the inuent to the rst 5 2952611 9/1960 Hamon et al' 20865 reactor less than about 32 p.p.m. mole. 3,234,120 2/1966 Capsu'to 208-139 10. The method of claim 1 wherein the platinum type reforming catalyst is initially `an eta alumina based catalyst DELBERT E' GANTZ Prlma'y Examine," promoted with a small amount of halogen. HERBERT LEV'INE, Examiner.

Claims (1)

1. A METHOD FOR REFORMING A PARAFFIN RICH NAPHTHA FEED WHICH COMPRISES CONTACTING A PARAFFIN RICH NAPHTHA FEED WITH A PLATINUM GROUP REFORMING CATALYST UNDER REFORMING CONDITIONS OF TEMPERATURE AND PRESSURE WHEREIN THE MOISTURE CONTENT OF THE INFLUENT TO THE FIRST REACTOR AND CATALYST LOADING OF THE FIRST REACTOR OF A MULTIPLE REACTOR REFORMING PROCESS IS CORRELATED IN ACCORDANCE WITH THE CURVES OF FIGURES 1 AND 2 TO ACHIEVE AT LEAST A 2 VOLUME PERCENT YIELD IMPROVEMENT IN C5+ REFORMATE YIELDS.

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