US2971902A

US2971902A - Aromatization of hydrocarbons

Info

Publication number: US2971902A
Application number: US803862A
Authority: US
Inventors: Robert A Blome; Jack M Andrews; Willard S Reaves
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1959-04-03
Filing date: 1959-04-03
Publication date: 1961-02-14
Anticipated expiration: 1978-02-14

Description

Feb. 14, 1961 R. A. BLoME ErAL AROMATIZATION oF HYDRocARBoNs 4 Sheets-Sheet 1 Filed April 3, 1959 ATToRN Y.

Feb. 14, 1961 R. A. BLOME ErAL AROMATIZATION OF HYDROCARBONS 4 Sheets-Sheet 2 Filed April 5, 1959 4 Sheets-Sheet 5 R. A. BLOME EVAL AROMATIZATION 0F HYDROCARBONS Feb. 14, 1961 Filed April s, 1959 INVENTORS. ROBERT A. BLOME, JACK M. ANDREWS, WILLARD S. REAVES, BY

ATT

z,71,9oz

4 Sheets-Sheet 4 R. A. BLOME I'AL AROMATIZATION OF' HYDROCARBONS JNVENToRs. ROBERT A. BLOME, JACK M. ANDREWS, wlLLARD s. REAvEs,

ATToR E Feb, 14, 1961 Filed April :5, 1959 United States Patent Oiice 2,971,902 Patented Feb. 14, 1961 ARoMATIzATroN or HYDnocARBoNs Robert A. Blume, Jack M. Andrews, and Willard S.

Reaves, Baytown, Tex., assignors, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, NJ., a corporation of Delaware Filed Apr. 3, v1959, Ser. No. 803,862

9 Claims. (Cl. 208-65) The present invention is directed to a method for increasingy yields of high octane number components. More particularly, the invention is directed to obtaining increased yields of high octane number components by hydroforming a naphthenic hydrocarbon feed. In its more specific aspects, the invention is concerned with increasing yields of high octane number components by reforming a mixture of naphthenic hydrocarbons, paranic hydrocarbons, and oleiinic hydrocarbons.

The present invention may be briey described as a method for increasing yields of high octane number components by hydroforming a naphthenic hydrocarbon feed having a molecular weight in the range from about 80 to about 150. The naphthenic hydrocarbon feed is sub- 'ected to hydroforming conditions in a plurality of serially interconnected reaction zones, each containing a platinum catalyst. The product from each reaction zone excepting the last reaction zone is Vreheated before charging to the rest of the reaction Zones. In the practice of the present invention, the improvement comprises maintaining the temperature drop in each of said reaction zones substantially equal in the range between 70? and 85 F. while operating each of said reaction Zones at a greater temperature within the Yrange from about 750 to about 1000 F. than the next preceding reaction zone.

A feature of the present invention is adding to the naphthenic hydrocarbon feed a sulicient amount of a parathnic hydrocarbon having 1 to 5 carbon atoms in the molecule which also enhances the yield of high octane number components.

In the practice of the present invention, temperatures in the range from about 750 to about 1 000 F. will be employed in the several reaction zones which ordinarily will be four in number; but a lesser or a greater number may be used. In the present invention, reactor inlet temperaturesvary from about 40 to 50 F. For'example, in an operation conducted in the practice of the present invention, the first reaction zone may be operated at a reactor inlet temperature in the range from about 775 to about 825 F., the second reaction zone having an inlet temperature within the range from about 825 to about 875 F. and the ,third reaction zone may be operated at inlet temperature within the range from about' 875 to 925 F. While the fourth Yor last reaction may operate with an inlet temperature in the range from about 925 to about 1000" F. By operating with inlet temperatures varying from each other by about 40 to about 50 F., approximately equal temperature drops are obtained in each of the reaction zones in the range between about 70 and about 85 F. and substantially improved yields are obtained.

Pressures employed in the practice of the present invention may range from about 50 to 500 pounds per square inch gauge. A suitable and preferred pressure is about 300 pounds per square inch gauge.

The space velocity employed is preferably about three volumes of feed hydrocarbons per volume of catalyst per hour entering the `first of the reaction Zones, but space velocities in the several reaction zones may vary from about 0.5 to about 5.0 v./v./hr.

Hydrogen is employed in hydroforming operations and the hydrogen-containing gas may be purified hydrogen but preferably is a recycled gas containing from about to about mole percent of hydrogen while the amount of hydrogen employed may range from about 2 to about 4 mols of hydrogen per mol of feed.l

As stated, the presence of light parains having l1 to 5 carbon atoms in the molecule is benecial in enhancing yield and suitably the light parains may be extraneously added parains or may be recovered from the product from the last reaction zone. Amounts of light paraiiins added to the naphthenic hydrocarbon freed may range from about .1 mol to about 2.0 mols per mol of feed hydrocarbon.

The feed hydrocarbon employed in Vthe practice ofthe present invention may be a naphthenic hydrocarbon feed obtained from crude petroleum which may contain paratiins and aromatics or may be a naphthenic hydrocarbon feed including naphthenic hydrocarbons, paraiiins, aromatics, and olens obtained from converted hydrocarbons. Regardless of the source of the naphthenic hydrocarbon feed, it should suitably boil in the range from about F. to about 400 F. or should have a molecular weight from about 80 to about 150. In the practice of the present invention, the successive or serially interconnected reaction zones are operated at increasingly high temperatures. When the feed reaches the first zone at the lowest temperature, the naphthenes are quickly converted to aromatics while the paraflins remain practically unchanged; and substantially little, if any, cracking occurs. In the second reaction zone the bulk of the naphthenes have already been converted to aromatics and therefore are not available for cracking; but with increased temperature in the second reaction zone, the paratlins begin to react at a faster rate. At the same time, the olen cracking and cyclization reactions are proceeding at an increased rate while the naphthenes have been almost completely depleted by conversion to aromatics. Thus, the olefins will preferentially dehydro- 'cyclize and the very high reaction rate and equilibrium constant for naphthenes dehydrogenation insures that their level will be kept veryllow throughout the reaction zones. In the third and fourth lreaction zones, which are operated at increasingly high temperatures, more cracking occurs together with vadditional conversion of parafiins to aromatics through the olen intermediary. In addition, the corresponding increase in the naphthene-aromatic equilibrium constant prevents Ythe aromatics from reverting to naphthenes and subsequently being subjected to cracking. Thus Vin thepractice of the present invention, contrary to conventional hydroforming operations, improved yields are obtained while maintaining or increasing the octane level of the product. Heretofore, it was always considered that increased or high octane numbers were to be obtained only at the sacrifice of yield. Actually, in the present invention, increased yields of high octane number paraliins are obtained and therefore the present invention is quite advantageous and useful as will be brought out more fully hereinafter.

The present invention will be further illustrated by reference to the drawing wherein:

' Fig. l is a flow diagram of a preferred mode;

Fig. 2 is a showing of conventional operations illustrating conditions and composition of the products in the several reaction zones;

Fig. 3 is a similar operation as that described in Fig. 2; and

Figs. 4, 5, and 6 are examples of the practice of the present invention.

Referring now to the drawing, numeral 11 designates a feed line by way of whichga preheated naphtha which may boil in the range from about 150 to 400 F. is 1ntroduced into a heating zone 12 which is supplied with heat by gas burner 13. The naphtha passes through the coil 14 and is brought up toa suitable inlet temperature for charging by line 15 to the lead reaction zone 16, which is provided with a bed of platinum catalyst 17 which suitably may be a supported platinum catalyst.

At this point it may be st ated that the catalyst employed in the present invention is preferably a supported platinum on alumina catalyst. The amount of platinum on'the catalyst'is preferably about .3% by weight but amounts of platinum in the catalyst of about .1 to 2.0% may be employed. In some cases as much as 4% by Weight of platinum may be used, although a preferred range is from about .2 to about .6% by weight. This support is preferably highly puried aluminum oxide which suitably may be a gamma alumina or an eta alumina derived from conventional sources of alumina hydrates such as those obtained from alumina alcoholates, phenolates, and the like. For example, the gamma alumina may be prepared from boehmite.

In the reaction zone 16, a temperature drop in the range from between about 70 to about 85 F. occurs and the converted product issues therefrom by line 18 and is charged into a first reheating zone 19 into which heat is supplied by gas burners 20. On passage of the product from zone 16 through the coil 21, the temperature of the product from zone 16 is raised to a temperature in the range indicated herein supra and the heated product from zone 16 is then charged by way of line 22 into a` second reaction zone 23 containing a bed of catalyst 24 which is similar to the bed 17 of zone 16. In zone 23, a temperature drop substantially equal to the temperature drop in zone 16 obtains and in the range between about 70 and 85 F. The product from zone 23 discharges controlled by valve 45 while excess hydrogen may be discharged from the system by opening valve 46 in line 41.

The hydrocarbon product is discharged from zone by line 47 into a fractional distillation zone 48 which is shown as a single distillation tower and which is equipped with all auxiliary equipment usually associated with the modern distillation tower including, by way of example only, suitable internal vapor-liquid contacting means such as bell cap trays and the like, condensing and cooling means, and means for inducing reux. Zone 48 is provided with heat for adjustment of temperatures and pressure by heating means illustrated by steam coil 49, which may suitably be an internal or external reboiler.

Light products may be Withdrawn by way of line 50 and may include the parans having 1 to 5 carbon atoms in the molecule while other fractions may be discharged by lines 5 1, 52, and 53. These fractions will contain substantial amounts of aromatics.

In the preferred operation in accordance with the present invention, light parains having 1 to 5 carbon atoms in the molecule are introduced into line 11 with the feed by line 54 controlled by valve 55. As stated, the source of the light parains may be from the product introduced into zone 48 by line 47.

By virtue of operating in accordance with the preferred mode, enhanced yields of high octane number hydrocarbons are obtained, as will be shown more fully by reference to the several examples.

A number of operations are conducted in accordance with the present invention in which each of the operations` is adjusted to produce a constant 98 octane number product.

The results of iive examples in which Examples I and II represent the prior art and Examples III, IV, and V represent the present invention are shown in Table I.

TABLE I Light Reformate Increased Increased Octane He Recycle, Parafn ie Yield above Yield above Example Pressure, Number, Moles/Mole Recycle, Moles/100 Example 1I, Example I,

p.s.1.g. Research of Feed Moles/Moley Moles of Moles/100 Moles/100 Clear of Feed Feed Moles cf Moles of Feed Feed 300 98 4. 0 O. 0 70. 7 300 9S 4. 0 0. 0 72. 0 300 98 4. 0 0. 0 75. 3. 5 4. 8 300 98 3. 5 0. 5 81. 4 9. 4 10. 7 300 9S 3. 0 1. O 90. 3 18. 3 19. 6

by way of line 25 into a second heating zone 26 supplied 50 with heat by gas burners 27. On passage of the product from zone 23 through the coil 28, the temperature of the product from zone 23 is raised to a temperature as indicated hereinbefore and the heated product is then introduced by line 29 into a third reaction zone 30 likewise provided with a bed 31 of supported platinum catalyst similar to that in

zones

16 and 23. On passage of the product through zone 30, a substantially equal tempera- `ture drop to that obtaining in

zones

16 and 23 is effected and the product from zone 30 discharges by line 32 into a third reheating zone 33 to which heat is supplied by gas burners 34. The product in zone 30 passes through coil 35 which connects to line 36 for introduction of the third product into the fourth reaction zone 37, also provided with a bed 38 of supported platinum catalyst. In zone 37 a temperature drop substantially equal to the It Will be noted from Table I that Examples III, IV, and V result in substantial increases in yields over Examples I and II, which represent the conventional operation.

The data shown in Table I were obtained in operations I 55 wherein a feed stock having the following composition is employed.

TABLE II Naphtha composition (mol percent) Parains 35.2 Naphthenes 37.3 Oleiins 1.0 Aromatics 26.5

M.w. los

Sp. gr 0.75

temperature drop in

zones

16, 23, and 30, and in theA .5 composition of the intermediate products are illustrated. From an examination of Fig. 2, it will be clear that a substantially constant inlet temperature is maintained in the several reaction zones. The temperature drop in the several reaction zones varied from 168 F. in the rst reaction zone to 20 F. in the last reaction zone.

Referring to Fig. 3, which illustrates Example II, a similar effect will be noted. vIn both Examples I and H, shown in Figs. 2 and 3, there is no addition of light hydrocarbons.

In Example III, which is illustrated in Fig. 4, it will be clear that the inlet temperature to the several reaction zones progressively increases while the temperature drop in each of the several zones is substantially equal.

In Fig. 5, which illustrates Example IV, light parafns are employed, Iand it will be clear that substantially increased yields over and beyond that obtainable in Example III are obtained.

Again, in Example V, shown in Fig. 6, the inlet temperature progressively increases to each succeeding reaction zone while the temperature drop is substantially the same. From the results shown in the several examples and illustrated by the several figures of the drawing, it will be clear that substantially improved results are obtained .in the practice of the present invention.

The present invention is quite advantageous and useful in that for the first time a mode of operation is provided wherein substantially ideal conditions are provided which allow obtaining of enhanced yield of high octane number material. Of course, it is realized that higher octant number material than that shown may be obtained if it is desired to sacrifice part of the enhanced yields obtainable in the practice of the present invention.

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

l. In a method for increasing yields of high octane number components in which a naphthenic hydrocarbon feed having a molecular Weight in the range from about 80 to about 150 is subjected to hydroforming conditions in a plurality of serially interconnected reaction zones each containing a platinum catalyst and in which the product from each reation zone excepting the last reaction zone is reheated before charging to the next of said reaction zones, the improvement which comprises maintaining the temperature drop in each of said reaction zones substantially equal in the range between about 70 and about 85 F. while operating said reaction zones each at a greater temperature Within the range from about 750 F. to about 1000 F. than the next preceding reaction zone.

2. In a method for increasing yields of high octane number components in which a naphthenic hydrocarbon feed having a molecular weight in the range from about 80 to about 150 is subjected to hydroforming conditions in a plurality of serially interconnected reaction zones each containing a platinum catalyst and in which the product from each reaction zone excepting the last reaction zone is reheated before charging to the next of said reaction zones, the improvement which comprises adding to said hydrocarbon feed an amount within the range from about 0.1 to about 2.0 moles of a parainic hydrocarbon having 1 to 5 carbon atoms in the molecule per mole of hydrocarbon feed, maintaining the temperature drop in each of said reaction zones substantially equal in the range between about 70 and about 85 F. while operating said reaction zones each at a greater temperature within the range from about 750 F. to about 1000 F. than the next preceding reaction zone.

3. In a method for increasing yields of high octane number components in which a naphthenic hydrocarbon feed having a molecular weight in the range from about 80 to about 150 is subjected to hydroforming conditions in the presence of about 2 to about 4 moles of hydrogen per mole of feed and at a space velocity in the range from about 0.5 to about 5.0 v./v./hour and at a pressure in the range from about 50 to about 500 pounds per square inch gauge in a plurality of serially interconnected reaction zones each containing a platinum catalyst and in which the product from each reaction zone excepting the last reaction zone is reheated before charging to the next of said reaction zones, the improvement which comprises maintaining -the temperature drop in each of said reaction zones substantially equal in the range between about 70 and about 85 F. while operating said reaction zones each at a greater temperature within the range from about 750 F. to about 1000 F. than the next preceding reaction zone.

4. A method in accordance with claim 3 in which four reaction zones are employed and in which the inlet temperature to the first reaction zone is Within the range from about 775 to about 825 F., the inlet temperature to the second reaction zone is Within the range from about 825 to about 875 F., the inlet temperature to the third reaction zone is within the range from about 875 to about 925 F., and the inlet temperature to the fourth reaction zone is within the range from about 925 to about 1000 F.

5. In a method for increasing yields of high octane number components in which a naphthenic hydrocarbon feed having a molecular weight in the range from about to about 150 containing parains and aromatics and substantially free of olefins is subjected to hydroforming conditions in four serially interconnected reaction zones each containing a platinum catalyst and in which the product from each reaction zone excepting the last reaction zone is reheated before charging to the next of said reaction zones, the improvement which comprises mainn taining the temperature drop in each of said reaction zones substantially equal in the range between about 70 and about F. While operating said reaction zones each at a greater temperature within the range from about 750 F. to about 1000" F. than the next preceding reaction zone, the naphthenes in said hydrocarbon feed being substantially completely hydroformed to aromatics in the lirst two of said reaction zones and the parains in said hydrocarbon feed being substantially completely reacted in the last two of said reaction zones.

6. ln a method for increasing yields of high octane number components in which a naphthenic hydrocarbon feed having a molecular weight in the range from about 80 to about 150 is subjected to hydroforming conditions in a plurality of serially interconnected reaction zones each containing a platinum catalyst and in which the product from `each reaction zone excepting the last reaction zone is reheated before charging to the next of said reaction zones, the improvement which comprises maintaining the temperature drop in each of said reaction zones substantially equal to the range between about 70 and about 85 F. while operating said reaction zones each at a greater temperature Within the range from about 750 F. to about l000 F. than the next preceding reaction zone, the temperature of the inlet to each of said reaction zones varying in the range from about 40 to about 50 F.

7. A method in accordance With claim 6 in which an amount of a parain hydrocarbon having l to 5 carbon atoms in the molecule in the range from about .l to about 2.0 moles per mole of hydrocarbon feed is added to said naphthenic hydrocarbon feed.

8. A method in accordance with claim 7 in Which the added paratiin hydrocarbon is separated from the product from the last of said zones.

9. In a method for increasing yields of high octane number components in which a naphthenic hydrocarbon feed having a molecular weight in the range from about 8O to about 150 containing parains and aromatics and substantially'free of oleinsA is subjected to hydroformng Y t catalyst and in which the produce from each reaction zone excepting the last reaction zone is reheated before charging to the next of saidrreaction zones, the improvement which comprises adding to said hydrocarbon feed an amount within the range from about 0.1 to about 2.0 moles ofa parainic hydrocarbon having 1 to 5 carbon atoms in the molecule per mole of hydrocarbon feed, maintaining the temperature drop in each of said reaction zones substantially equal in the range between about 70 and about 85 F. while operating said reaction zones each at a greater temperature within the range from about 750 F. to about 1000 F. than the next 8 Y preceding reaction zone, the inlet temperature to the first reaction zone being within the range from about 775 to about 825 F., the inlet temperature to the second reaction being within the range from about 825 to about 875 F., the inlet temperature to the third reaction zone being Within the range form about 875 to about 925 F., and the inlet temperature to the fourth reaction zone being Within the range from about 925 to about 1000 F.

References Cited in the le of this patent UNITED STATES PATENTS Haensel Ian. 27, 1959

Claims

1. IN A METHOD FOR INCREASING YIELDS OF HIGH OCTANE NUMBER COMPONENTS IN WHICH A NAPHTHENIC HYDROCARBON FEED HAVING A MOLECULAR WEIGHT IN THE RANGE FROM ABOUT 80 TO ABOUT 150 IS SUBJECTED TO HYDROFORMING CONDITIONS IN A PLURALITY OF SERIALY INTERCONNECTED REACTION ZONES EACH CONTAINING A PLATINUM CATALYST AND IN WHICH THE PRODUCT FROM EACH REACTION ZONE EXCEPTING THE LAST REACTION ZONE IS REHEATED BEFORE CHARGING TO THE NEXT OF SAID REACTION ZONES, THE IMPROVEMENT WHICH COMPRISES MAINTAINING THE TEMPERATURE DROP IN EACH OF SAID REACTION ZONES SUBSTANTIALLY EQUAL IN THE RANGE BETWEEN AB OUT 70* AND ABOUT 85*F. WHILE OPERATING SAID REACTION ZONES EACH AT A GREATER TEMPERATURE WITHIN THE RANGE FROM ABOUT 750* F. TO ABOUT 1000*F. THAN THE NEXT PRECEDING REACTION ZONE.