US2908636A - Hydroforming process - Google Patents

Description

Qct. 13, 1959 w. STEFFGEN ETAL 2,908,636 HYDROFORMING PROCESS Filed Dec. 27, 1955 AlFh Frederick Williams Steffgen Charles Newton Kimberlm, Jr. Fred J. Buchrnann Alexis Voorhies, Jr.

By Attorney Inventors United States Patent 2,908,636 HYDROFORMlNG PROCESS Frederick Williams Stelfgen, Charles Newton Kimberlin, Jr., Fred J. Buchmann, and Alexis Voorhies, Jr., Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware Application December 27, 1955, Serial No. 555,353

4 Claims. (Cl. 208-140) drogen and ordinarily there is a net production of hydrogen in the process. A variety of reactions occur during hydroforming including dehydrogenation of naphthenes to the corresponding aromatics, hydrocracking of paraffins, isomerization of straight chain paraifins to form branch chain parafiins, dehydrocyclization of parafiins and isomerization of compounds such as ethylcyclopentane to form methylcyclohexane which is readily converted to toluene. In addition to these reactions some hydrogenation ofolefins and polyolefins occurs and sulfur or sulfur compounds are eliminated by conversion to hydrogen sulfide or to catalytic metal sulfides making the hydroformate burn cleaner in an internal combustion engine. 1

Hydroforming is usually applied to a rather wide boiling range, naphtha, i.e. having a boiling range of from about 125 F. to about 400-430 F. It has been know that the lower boiling naphthas are not substantially improved by hydroforming processes as ordinarily conducted. The extensive article on Hydrofonning in Petroleum Processing for August 1955 states at page 1174, Optimum reformer utilization is obtained by not using feed stock constituents boiling much below 200 F which do not contribute greatly to increased octane during reforming as these merely take up reformer capacity better used for high boiling materials more susceptible to octane upgrading. In view of the continuing demand for more and higher octane number gasolines however, it is becoming increasingly important to upgrade these lower boiling fractions.

It is the object of this invention to provide the art with an improved method for reforming or upgrading light naphthas.

It is also the object of this invention to provide a simple and elfective method for hydroforming light petroleum naphthas boiling in the range of from about 110250 F., preferably from about ISO-225 F., in contact with platinlun-containing catalysts.

These and other objects will appear more clearly from the detailed specificationand claims which follow.

It has now been found that light naphthas boiling in.

2,908,636 Patented Oct. 13, 195? ice 2 the range of from about 1l0250 F. may be upgrading simply and effectively by hydroforming them in contact with platinum-containing catalysts at pressures below 125 p.s.i.g.' and preferably at pressures of from 50 to 100 pounds per sq. inch. The low pressure platinum hydroforming process is particularly suited to the improvement of the octane number of virgin naphthas boiling in the range of about 150 to 200 F. The C fraction, boiling below about 150 F. is not upgraded by the process to as great an extent as the C and C hydrocarbons; therefore the C fraction is not a particularly desirable component of the feed. On the other hand, the.

presence of C hydrocarbons in the feed is not particularly harmful so that it may be preferred to include this fraction in the feed if doing so will avoid an additional distillation step in the feed preparation. The fraction boiling above 200 F. up to about 225 F. or 250 F. responds fairly well to the conventional hydrofroming processes employing either molybdena or platinum catalysts at about 200 p.s.i.g. or higher and may be included in the feed to such processes if desired. On the other hand, this fraction also responds well to the present low pressure platinum process so that the method of handling this particular fraction of the virgin naphtha feed will depend upon circumstances such as the availablity of equipment and the volumes of the difierent boiling range fractions which it is desired to process. It has been found that in the pressure range of from 50-100 pounds per sq. inch it is possible with platinum containing catalysts to upgrade a light virgin naphtha having a mean average boiling point of 169 F. and a Research clear O.N. of 66 into a hydroformate having a Research clear O.N. of around 90 and higher in yields of about volume percent and into a hydroformate having a Research clear O.N. of around 95 or higher in yields of about 68 volume percent. In contrast thereto hydroforming of this naphtha at 200 p.s.i.tg. with a molybedenum oxide catalyst produces a hydroformate of only about 81 O.N. in yields of about 75 vol. percent or about 85 ON. in yields of about 68 vol. percent. In further contrast thereto, hydroforming of this naphtha at 200 p.s.i.g. with platinum containing catalysts produces a hydroformate of only 85 octane number at 75 volume percent yield. Moreover, it was found impossible to increase the octane number much above about 87 by hydrofroming with the platinum catalyst at 200 p.s.i.g. In other words, the hydroforming process with platinum catalyst at 200 p.s.i.g.

.has an octane number ceiling only slightly above 87 octane number when applied to light virgin naphthas whereas the octane number ceiling for the lower pressure platinum process was found to be well above octane number when applied to the same light virgin naphtha feed. Under these reaction conditions there is a tendency for carbon to form on the catalyst quite rapidly and therefore it becomes necessary to regenerate the catalyst quite frequently. Accordingly, the process is most advantageously carried out in a fluidized solids system so that the catalyst may be conveniently circulated from the reaction zone to the regeneration zone where carbonaceous deposits may be burned off. It is also desirable to provide means for subjecting a portion of the regenerated catalyst, also preferably continuously to reactivation with a halogen or halogen compound such as chlorine or hydrogen chloride. A freehalogen such as chlorine is the preferred treating agent for reactivation. Aside from the accumulation of poisons, the deactivation of platinum hydroforming catalysts proceeds by two mechanisms, viz., (1) the loss of chlorine or other halogen that is normally present as a part of the catalyst composition and that contributes substantially to the catalytic activity, and (2) the agglomeration of the platinum metal into relatively large or massive crystals having crystal diameters in excess of about 50 :angstrom units. Treatment of the catalyst with a halogen compound such as hydrogen chloride or the like is effective in restoring the halogen content of the catalyst to the desired value and to this extent is effective in restoring the activity of deactivated or partly deactivated catalysts. But treatmen with a halogen compound such as hydrogen chloride or the like is not effective for the reduction of the size of platinum crystals; therefore such treatment is only partially and not entirely effective in restoring the catalytic activity of deactivated catalysts. On the other hand, treatment of the catalyst with an elementary halogen such as chlorine or the like not only restores the catalyst halogen content to the desired level but also ac- -complishes the redispersion of the platinum metal by breaking up the large platinum crystallites. This treatment, therefore, is entirely effective in restoring the activity to deactivated catalysts whose activity loss was not due to the accumulation of poisons such as arsenic or the like.

In the accompanying drawing, there is illustrated diagrammatically, an apparatus layout in which a preferred modification of the .present invention may be carried into effect.

Sinular reference characters refer to similar parts or materials.

Referring in detail to the drawing, 10 represents a reactor vessel containing a fluidized bed 12 of catalyst comprising 0.01 to 1.0 wt. percent platinum and/or 0.1 to 2.0 Wt. percent palladium. A suitable catalyst comprises about 0.1 to 0.6 wt. percent platinum widely dispersed on a high surface area alumina support, having a surface area of about 150 to 220 square meters per gram. A preferred catalyst is one comprising a mixture of one part of a platinum catalyst concentrate consisting of 0.3 to 2.0 wt. percent platinum on alumina microspheres formed by spray drying an alcoholate alumina hydrosol mixed with sufficient unplatinized alumina to form a catalyst composition containing about 0.01 to 0.2 wt. percent platinum. The pressure in vessel 10 may be in the range of to 125 p.s.i.g., and is preferably about 50 p.s.i.g. The temperature of catalyst bed 12 may be in the range of about 800 to 975 F.; however, under the conditions of low pressure and low recycle hydrogen rates of the present invention, the dehydrogenation activity of platinum metal catalysts is extremely high, so that the reaction temperature may be somewhat lower than that of the prior art hydroforming processes. A preferred temperature is in the range of 875 to 950 F.

Light virgin naphtha feed, having a boiling range of from 110250 F., preferably 150 to 225 F. is preheated in heater 14 and passed by line 16 into the lower section of reactor 10. The naphtha feed is preheated in heater 14- to a temperature in the range of 900 to 1050 F., preferably about 975 F. to 1000 F. Recycled hydrogen, which has been preheated to 900 to 1300 F., preferably about 1200 F., in heater 18 and which bears freshly regenerated and reactivated catalyst from lines 52 and 57, is also introduced into the lower section of reactor by line 20. Alternately, in place of separately preheating the naphtha feed and recycle hydrogen streams, the naphtha feed from line 17 may be mixed with the recycle gas in line 32, and the combined stream preheated in heater 18; in this case the preferred preheat temperature is in the range of 900 to 1000 F. The recycle gas, or recycle hydrogen, normally contains about 65 to 90 mol percent hydrogen with the remainder being light hydrocarbon gases; the exact composition of the recycle gas depends upon the hydroforming conditions maintained in reactor 10 and upon the pressure and temperature at which the gas is separated from the liquid products. The amount of recycle gas employed may be in the range of about 500 to 5000, preferably about 1000 to 3000 standard cubic feet per barrel of naphtha feed (s.c.f./b.). In addition to preheating the feed and recycle gas the additional heat load required by the endothermic hydroforming reaction may be supplied to eatalyst bed 12 by heating coil 15 immersed therein. Hot flue gases, mercury, Dowtherm or the like may be passed through coil 15. Other means of supplying heat to eatalyst bed 12, for example, by circulating a stream of catalyst through coils in a furnace, are within the scope of the invention. The naphtha vapor and recycled gas pass upwardly through catalyst bed 12 whereupon the naphtha is hydroformed. After leaving catalyst bed 12 the hydroformed vapor and gas is passed through conventional catalyst recovery equipment, such as a cyclone separator or filter, or the like, and through line 22 and condenser or cooler 24 into gas-liquid separator 26. The hydroformed naphtha product is removed from the system by line 28. The excess gaseous product is removed from the system by line 30 and the remainder of the gas is recycled by line 32. When feeding a high sulfur content naphtha, above about 0.02 wt. percent sulfur, it is preferred to remove the hydrogen sulfide from the recycle gas in line 32 by means of a caustic scrubber or other conventional scrubbing means not shown. Catalyst from bed 12 passes into standpipe 34 where it is stripped of adsorbed hydrocarbons by hydrogen from line 36. Stripped catalyst from standpipe 34 passes into line 38 where it is picked up by a stream of air and transported to regenerator 40. Regenerator 40, which is a relatively small vessel because of the low rate of coke formation on platinum and palladium catalysts, is maintained at a temperature of 900 to ]200 F., preferably, 1000 to 1100 F. The pressure in regenerator 40 is approximately the same as that in reactor 10. In vessel 40 coke deposits are burned from the catalyst by air introduced by line 38. In the burning of the coke a certain amount of water is formed by combustion of the hydrogen in the coke; this is stripped from the catalyst and passes overhead with the flue gases through conventional catalyst recovery means, such as a cyclone separator or filter, or

the like, and is removed from the system by line 42. Since for the subsequent chlorine reactivation, presently to be described, a completely regenerated or coke-free catalyst is desired, it is preferred to employ an excess of air in regenerator 40; the oxygen content of the flue gas in line 42 should be above 2%, and is preferably above 5%. Regenerated catalyst passes by line 44 into the upper section of chlorine reactivator vessel 46. Since it is desired to maintain substantially anhydrous conditions in reactivator vessel 46, water vapor is further stripped from the catalyst passing through line 44 by means of air introduced by line 48. Reactivator vessel 46, which may be comparatively small in cross-sectional area compared to its height, is preferably maintained at the same pressure and temperature as regenerator 40. Chlorine gas or a mixture of chlorine gas in air is introduced into vessel 46 near the midsection thereof by line 50 and air is introduced into vessel 46 near the bottom thereof by line 54. The air and chlorine pass upwardly through vessel 46 and are removed from the system. by line 45, .while catalyst from line 44 passes downwardly through vessel 46. Thus, the upper section of reactivator vessel comprises a chlorine treating zone wherein regenerated (i.e., coke-free) catalyst is contacted with a mixture of chlorine gas and air, and the lower section of reactivator vessel 46 comprises a stripping zone wherein adhering chlorine is stripped from the treated catalyst by means of air. In the upper, chlorine treating zone of vessel 46 the chlorine partial pressure may be in the range of about 0.001 to 2 atmospheres, preferably, about 0.01 to 1 atmosphere. The quantity of chlorine admitted to vessel 46 by line 50 may be in the range of 0.1 to 2.0

wt. percent, preferably, about 0.5 wt. percent, of the catalyst introduced into vessel 46 by line 44. As mentioned above the temperature and total (air plus chlorine) pressure in the chlorine treating zone is preferably about the same as the temperature and pressure in regenerator vessel 40. The residence time of the catalyst in the chlorine treating zone may be in the range of seconds to 1 hour, preferably, about 1 to 15 minutes. The action of the chlorine treatment on the catalyst is to destroy large platinum crystals and re-disperse the metal over the catalyst surface of the base or support, thus completely restoring the activity of the catalyst to that of fresh catalyst. As the chlorine treated catalyst descends from the upper chlorine treating zone of vessel 46 into the lower stripping zone of vessel 46, adhering clhorine is stripped from the catalyst by air fro-m line 54. However, it is usually preferred not to completely strip the chlorine from the catalyst and the operation of the stripping zone, in conjunction with that of the chlorine treating zone, provides an important means for controlling the hydrocracking activity of the catalyst, and hence, of controlling the volatility of the hydroformed naphtha product at the desired level. Apart from the temperature and pressure in vessel 46, which are generally fixed by those in vessel 40, the quantity of chlorine remaining on the stripped catalyst may be controlled by the amount of air introduced into the stripping zone by line 54 and the partial pressure of the chlorine employed in the chlorine treating zone. The lower the amount of stripping air employed and the higher the partial pressure of chlorine in the treating zone, the greater the amount of chlorine remaining on the stripped catalyst and the higher the hydrocracking activity of the catalyst, and hence, the higher the volatility of the hydroformed naphtha product. The amount of chlorine which it is desirable to have remaining on the stripped catalyst is related to the platinum content of the catalyst. With high platinum content catalysts, a relatively high chlorine content is desirable; a correspondingly lower chlorine content is desirable for lower platinum contents. In general, the total amount of chlorine (i.e., both chemically combined and adsorbed chlorine) remaining on the stripped catalyst when employing a catalyst of 0.6% platinum content may be in the range of about 0.2 to 1.25 wt. percent, and is preferably about 0.5 to 1.0 wt. percent. The amount of chlorine remaining on the stripped catalyst may be proportionally lower when employing a lower platinum content catalyst. The reactivated and stripped catalyst passes from vessel 46 by line 52 into line where it is picked up by recycle gas or by a mixture of recycle gas and naphtha feed and transported to reactor vessel 10 as hereinbefore set forth.

'If desired, all of the catalyst leaving regenerator vessel EXAMPLE A naphtha having the following inspection was hydroformed according to the present invention:

Feed inspection Gravity 679 API. Boiling range (5% to 95%) l62-19l F. Naphthenes, volume percent 40.7.

Parafiins, volume percent 57.1

Aromatics, volume percent 2.2. Sulfur 0.03 wt. percent.

CFRR octane number 66.1.

- Conditions in hydroforming zone Catalyst composition 0.6% platinum onalcoi t holate alumina. Temperature... 900 F.

Pressure 50 p.s.i.g.

W/hr./w 1.1.

Conditions in the regenerator Temperature F 1050 Pressure p.s.i.g 50 Residence time minutes..- 30 Weight percent carbon on regenerated catalyst 0.0

Conditions in chlorine treater Temperature 1050 F. Pressure -L. 50 p.s.i.g. Residence time 5 minutes. Composition of treating gas 11% chlorine in air. Chlorine partial pressure About 0.5 atmosphere. Duration of air treat following chlorine treat 10 minutes. Wt. percent chlorine on stripped catalyst About 0.85.

Product impection Gravity API.... 49.2 Boiling range (5% to F... l44-265 CFRR octane number 96.9 Product yield, vol. percent 66.5

In another operation with the same light naphtha feed stock and with the same 0.6% platinum catalyst which was conducted at a pressure of pounds per square inch and which was otherwise identical to the above described operation, there was obtained 70.2 volume percent yield of product having a Research clear octane number of 91.6.

In another operation the same light naphtha feed was subjected to the conventional high pressure platinum hydroforming operation conducted at 200 p.s.i.g. The prodnot, obtained in 69.6 volume percent yield, had a Research clear octane number of only 87.2.

In still another operation the same light naphtha feed was subjected to the conventional molybdena hydroforming operation conducted at 200 p.s.i.g. The product, obtained in 62.4 volume percent yield, had a Research clear octane number of 87.5.

A clear comparison of the various hydroforming processes by which this light naphtha feed was treated is given in the following summary table. The table shows the highest octane number achieved in each process and the feed rate (W./hr./w.) at which this octane number was obtained. The table also shows the yield by hydroformed product given by each process at several octane number values.

, generation.

It will be understood, of course, that the foregoing examples are merely illustrative of the invention and that the same is not limited to the precise details set forth above. In other words, the temperature in the hydroforming zone may vary from 800 to 975 F., the pressure may vary from atmospheric to about 125 p.s.i.g., the length of each productive phase of the complete process cycle, including regeneration and chlorine treatment may vary from 1 to hours. The catalyst composition may vary from one containing .01% of platinum to one containing 1% by weight of platinum, the remainder being a suitable support. Furthermore, palladium may be used in place of platinum as the active hydrogenationdehydrogenation component of the catalyst, but pallidium must be used in about three times. the amount of platinum for similar results. As to the treatment of regenerated catalyst. with chlorine, it is pointed out that the amount of chlorine in the treating gas may vary from a chlorine partial pressure of about 0.001 atmosphere to a chlorine partial pressure of about 2 atmospheres, and that it will not be necessary to treat the catalyst during every cycle. An examination of the regenerated catalyst periodically to determine average platinum crystallite size, will determine whether or not it is necessary to increase the proportion of the catalyst being treated with the chlorine-containing gas. If the average crystallite size is above about or 75 A. units as determined by X-ray examination, then the proportion of the catalyst flowing through the chlorine treatment zone described above should be increased and the proportion of catalyst bypassing this zone should be decreased. It is important to note in connection with the chlorine treatment that the catalyst should be substantially free of water. In otherwords, the catalyst should be substantially free of water when subjected to chlorine treatment for best results.

To recapitulate briefly, the present invention relates to improvements in hydroforming light naphthas in the presence of a platinum group metal.

As has been pointed out, the present invention provides a process for the octane number improvement of light naphthas boiling in the range of about 110 to 250 F. and it is particularly adapted to the octane number improvement of naphtha fractions boiling in the range of about 150 to 200 F. Heavier naphthas boiling above about 250 F. up to about 430 F. may also be processed according to the present invention, although there is no particular advantage in doing so. The heavier naphthas are generally more advantageously hydroformed by the conventional high pressure hydroforming processes using either platinum or molybdena catalysts and operating at pressures of about 20 pounds per square inch or higher. The heavier naphthas respond well to the conventional hydroforming processes and at the higher pressures employed less coke is deposited on the catalyst and the rate of catalyst deactivation is less with these heavy feeds. However, under certain circumstances when it is desired to upgrade a wide cut naphtha containing material boiling both in the light naphtha and in the heavy naphtha boiling ranges, it may be preferred to process this wide cut naphtha according to the low pressure platinum hydroforming process of the present invention. By so doing, feed prefractionation and the provision of separate high pressure hydroforming facilities may be avoided.

The present improvements comprise employing the fluidized catalyst technique, and it is further characterized in that the process is operated at relatively low pressures, low hydrogen recycle rates and short time on-stream pefiods. It has been discovered that the catalyst which is fouled during the on-stream phase cannot successfully be regenerated with air alone, nor can it be satisfactorily reactivated by subjecting the catalyst to a prolonged soaking in air at elevated temperatures and pressures, following the removal of deactivated deposits by oxidative re- It has been discovered, however, that the spent catalyst may be restored to a high level of activity by subjecting it first to oxidative regeneration and then subjecting it to the influence of a chlorine-containing gas for a short period of time. The chlorine treatment of the regenerated catalyst need not be performed during each cycle. It is apparently required when the platinum group metal particles are formed into large crystals as a result of use in the process. Furthermore, since addition of chlorine to the catalyst increases its hydrocracking activity, the volatility of the hydroformate may be adjusted to the desired level by control of the amount of chlorine remaining on the catalyst after treatment with chlorine and stripping with air. During the processing, however, chlorine may be driven off possibly by the action of water either in the feed or formed during the process or during the regeneration of the catalyst. In any event, the results of tests clearly dictate that the air regenerable platinum catalyst must be at least intermittently treated with the chlorine-containing gas following regeneration in order to maintain the activity and selectivity of the said catalyst at a high level.

This application is a continuation-in-part of Serial No. 453,456, filed September 1, 1954.

Numerous modifications of the present invention may be made by those who are familiar with this art without departing from the spirit thereof.

What is claimed is:

1. A method for hydroforming virgin petroleum naphtha fractions boiling in the range of from about 150 to 225 P. which comprises contacting said fractions in admixture with a hydrogen-rich gas with a fluidized bed of finely divided platinum on alumina catalyst particles in a reaction zone at a temperature of 800 to 975 F. and at a pressure of from 50 to pounds per square inch and maintaining said hydrocarbons in contact with catalyst for a period sufficient to produce a (1 hydroformate having a research clear octane number of at least 85, continuously withdrawing catalyst particles from the reaction zone, transferring the withdrawn catalyst particles to a regeneration zone, burning deactivating carbonaceous deposits from the catalyst particles in the regeneration zone by treating the deactivated catalyst with a regeneration gas containing an excess of oxygen, withdrawing the regenerated catalyst from the regeneration zone, transferring at most a part of the regenerated catalyst to a reactivator vessel, halogen treating the withdrawn regenerated catalyst in the reactivator vessel with a gas se lected from the group consisting of halogen and halogen compounds, and recycling the remainder of the regenerated catalyst and the halogen-treated regenerated catalyst to the reaction zone.

2. The process defined in claim 1 in which the regeneration gas contains at least 5% excess oxygen, the regeneration temperature is in the range of 9001200 F., and the regenerated catalyst is treated with chlorine.

3. The process as defined in claim 2 in which the catalyst consists of platinum on alcoholate alumina.

4. The process defined in claim 2 in which the catalyst comprises 0.3 to 2.0 wt. percent platinum on alumina diluted to 0.01 to 0.2 wt. percent platinum with unplatinized alumina.

References Cited in the file of this patent UNITED STATES PATENTS 2,373,254 Mattox May 9, 1942 2,479,110 Haensel Aug. 16, 1949 2,587,425 Adams et a1 Feb. 26, 1952 2,636,865 Kimberlin Apr. 28, 1953 2,642,384 Cox June 16, 1953 2,689,208 Murray et al. Sept. 14, 1954 2,746,909 I-Iemminger May 22, 1956 2,758,063 MacLaren Aug. 7, 1956 2,816,857 Hernminger Dec. 17, 1957

Claims (1)

1. A METHOD FOR HYDROFORMING VIRGIN PETROLEUM NAPHTHA FRACTIONS BOILING IN THE RANGE OF FROM ABOUT 150 TO 225*F. WHICH COMPRISES CONTACTING SAID FRACTIONS IN ADMIXTURE WITH A HYDROGEN-RICH GAS WITH A FLUIDIZED BED OF FINELY DIVIDED PLATINUM ON ALUMINA CATALYST PARTICLES IN A REACTION ZONE AT A TEMPERATURE OF 800 TO 975*F. AND AT A PRESSURE OF FROM 50 TO 100 POUNDS PER SQUARE INCH AND MAINTAINING SAID HYDROCARBNS IN CONTACT WITH CATALYST FOR A PERIOD SUFFICIENT TO PRODUCE A C5- HYDROFORMATE HAVING A RESEARCH CLEAR OCTANE NUMBER OF AT LEAST 85, CONTINUOUSLY WITHDRAWING CATALYST PARTICLES FROM THE REACTION ZONE, TRANSFERRING THE WITHDRAWN CATALYST PARTICLES TO A REGENERATION ZONE, BURNING DEACTIVATING CARBONACEOUS DEPOSITS FROM THE CATRALYST PARTICLES IN THE REGENERATION ZONE BY TREATING THE DEACTIVATED CATALYST WITH A REGENERA-

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