US2141185A - Reforming of naphtha - Google Patents

Description

Dec. 27, 1938.

E. J. HOUDRY REFORMING OF NAPHTHA Filed April 27, 1955 Patented Dee. 27, 1938 UNITED STATES PATENT OFFICE Houdry Process C poration of Delaware orporation, Dover,

i., a cor- Applioation April 27, 1935, Serial N0. 18,600

6 Claims '(Cl. 196-52) This invention relates to the treatment of hydrocarbon distillates of mineral oil and the like at the upper end of the -gasoline boiling range and has as its primary purpose the improvement of the antlknock characteristics of the material treated. Another and related object is to eect a general or a partial lowering of the boiling range. Still another object is to reduce the sulphur content of the material treated. Still another object 1o is to produce the above results with a minimum of loss.

To meet the requirements of automotive 'engines and the specifications for motor fuels suitable therefor reiiners have resorted to various expedients to improve the antiknock ratings of their products. One expedient is to mix with the iinished product a chemical substance which modifies the rate of combustion of the fuel so as to suppress to some extent detonating edect of the fuel,

80 one such substance being tetraethyl lead, known under such names as ethyl spirit or Q fluid. Such substances, being highb poisonous, are dangerous to handle and expensive to manufacture. Moreover the number of octane points rise which can 2s be effected by the addition of such substances varies widely with the composition of the motor fuel and in some instances is quite negligible.

Another expedient is the thermal reforming of knocking hydrocarbons by the use of heat and so pressure. Since the low boiling fraction of straight run gasoline contains the non-knocking components, refiners have found it necessary, in many instances, to reform the higher boiling or knocking part of natural gasoline `to 'secure an 35 adequate quantity of standard grade gasoline. The operation is, in most instances, conducted at a cracking temperature, namely, above 950 F., and at prsures in excess of 400 pounds in a once through operation. Temperature and pressure- 40 conditions are set to produce a predetermined gas make, inasmuch as the gas make in this operation is directly related to the octane rating of the product. The gas make is high and normally varies from 15% up to 30 or even 35%, depend- 45 ing upon the nature of the stock and the octane rating desired. Hence the thermal operation of reforming is costly by reason of the heavy losses.

Many attempts have been made in 'recent years t-o effect reforming by catalysis and there are disso closures in patents of I. G. Farbenindustrie Aktiengesellschaft and others specifying a. wide 'rangeof catalysts and of operating conditions including temperature ranges from 572 to 1500 F., pressures from subatmospheric to in excess of 55 200 atmosphereafeed rates of 1:2 (one volume of oil per hour to two volumes of catalyst) to 3:1 per hour. The U. S. patent to M. W. Boyer, No. 1,934,031, issued November 7, 1933, specifies temperatures above 900, 950 or 1000 F., pressures above atmospheres and preferably above 200 5 Vatmospheres, a feed rate of 2:1, and operation continuously with added hydrogen. So far as I am aware. none of the proposed catalytic reforming processes has gone into commercial use or has been found to be capable of successful competi- 1o tion with thermal reforming or with octane increase by the `addition of chemicals.

During the development of various processes for the conversion or treatment of petroleum with the aid of contact masses I have made many at- 15 tempts to effect catalytic reforming of heavy naphtha with indifferent success. After an exhaustive and detailed study extending over a long period, with thousands of experiments, I have finally discovered that heavy naphtha can be re- 20 formed by a new method of procedure with remarkably favorable results, especially when the operation is effected catalytically.

|l'he drawing shows a flow sheet of the process of this application.`

The first step in the new procedure is to divide the naphtha by fractionation or otherwise into two parts, the first part covering the boiling range f of about 250 to 375 F. and the second part from about 375 F. to the end point of the naphtha. 30

v'I'hese two parts are then reformed separately as follows: Each part undergoes the chosen reforming `operation and from the product is separated the reformed material of the desired antiknock value. su'ch as 75 octane, leaving a low octane 35 residue. I'his residue is then reformed and the 7 5 octane material again removed, the procedure continuing until all the material of each part is brought to the desired octane rating. While thermal reforming may be used with a certain meas- 40 ure of success, I prefer to use a catalytic reforming operation, since it gives a larger percentage of easily separated material of the desired octane rating, but the operating conditions are critical and divergence from any of them beyond a relatively narrow range is sufficient to upset yield, or product, or both.

The results of the initial fractionation of the charge combined with separate catalytic reforming of the fractions are most surprising and unexpected. In the first place, liquid yield as high as v100% is attainable. In the second place, the octane rating off' the converted product is above 70 and usually about 75 (C.F. R. Motor Method) regardless of the charging material. In the third place, the gas make has little or no eifect upon the antiknock improvement of the charge.

Factors in the most successful operation of my process comprise, catalyst, temperature, pressure, feed rate or time of contract of reactants, length of period on-stream (which takes into account the changed characteristics-of the catalyst due to deposit of contaminants as the reaction period progresses), and added gaseous material, in addition to the particular nature of the hydrocarbon charge. Preferred conditions of temperature.

and/or pressure vary, for example, as the feed rate or activity ofthe catalyst varies. By way of illustration as the time of contact of reactants with the catalyst is increased, the temperature and/or pressure may be reduced somewhat, and vice versa. Illustrative relative conditions of operation appear hereinafter.

Salient features' of the present invention, involve: (1) maintaining the fraction of reactants charged to a reforming zone within a relatively or fairly narrow boiling range, e. g; dividing the raw naphtha charge into fractions, one boiling below substantially 375 F. and another boiling above substantially 375 F. or dividing the naphtha charge into fractions each having a boiling range of approximately 100 F. and (2) controlling the rate of feeding the naphtha fraction to the catalyst as herein defined and illustrated.

Reforming in a series of separate passes, is, inter alia,` also an important feature of this invention.

The charge most particularly contemplated is a naphtha predominately in the boiling range of 250 to 450 F. which is divided into two or more fractions, e. g., 250 to 375 F. and 375 F. to end point respectively. These parts must be reformed separately. Several passes are usually required for best results.

The catalyst is essentially a blend of silica and alumina with as little extraneous material as possible. The weight ratio of silica and alumina should be not less than three to one, preferably four to one, or somewhat higher. The catalyst may be formed in various ways, as for example, precipitating silica on alumina, or alumina on silica, o r by combining a silica gel with alumina. Another way is to take a natural compound, such as a clay in the form of fullers earth, kieselguhr, bentonite, china clay, or the like, and then leach it with acids or treat it with other substances such as phosgene and various alkalies. The resulting product is used as a base or carrier on which to build back the desired silica to alumina ratio. In some instances, improved results are'secured by incorporating in the catalyst a small quantity of the oxide of one or more of the following metals-iron, lead, copper, manganese, vanadium, molybdenum, chromium, tungsten. The catalyst is formed in bits,

broken fragments, or molded pieces of substantially uniform size so as to be capable of regeneration in place.

The temperature must be between 850 and 925 F. and preferably between 875 and 925 F.

The pressure may vary between 15 and 300 pounds per square inch gauge. An excellent op eration is secured at 75 pounds. One advantage obtained by raising the pressure up to 300 pounds is an improvement in the rate of feed.

The feed rate may vary from 3:5 (three volumes of oil per hour to five volumes of catalyst) to.7 :5. A good rate for seventy-'five pounds pressure is 1:1. y

The period of operation varies from one-half to two hours, and comprises the time necessary to feed to the catalyst a quantity of oil varying from one-fourth the volume to a volume equal to twice that of the catalyst. The run generally averages from forty-five minutes to one and onehalf hours, the catalyst being thereafter regenerated to remove coke and tarry deposits in preparation for another run.

Extraneous gaseous material, in the form of steam or refractory gases such as vmethane. ethane, propane, butane, hydrogen or mixtures of the same, is added to the extent of from 2 to 5% by weight of the charge for the purpose of inhibiting secondary reactions and to reduce the deposit of contaminants upon the catalyst.

The operation is conducted so as to produce only a small amount of gas. as of the order of 4 to 7% per pass. This is enough to insure a good reaction and nothing is gained by making more gas. `The products of the reaction are topped by fractionation to separate out the lower boiling converted material of increased octane rating, as above 70. Normally about 50% of the charge is converted into high octane material. The remainder, which usually shows some slight improvement in octane over the charge, may be subjected, with or without fresh charge, to a second converting operation, and the procedure continued until all `the material is converted.

Since the charge is changed into lower gravity material, and since the gas make and the carbon deposit are low, the yield in liquid is very close to 100%.

First example The 65% or light cut was fed to a catalytic mass of the above described type maintained' at a temperature of 875 F., at a charging rate of 1:1, under 75 pounds pressure, with 2% of steam, for one hour.- The gas make was 4.3% by weight and the coke deposit on the catalyst 1.5%, the resulting products being topped to secure a 39% overhead having an octane rating of 72.7. The recycle material was sent in a second pass into the conversion zone under the same operating conditions., except that the reaction temperature was raised to 900 F. The gas make was 5% by weight and the coke deposit on the catalyst 1.8%, and a high octane overhead cut comprising 42% of the products was separated out having an octane rating of 70.7. The bottoms or recycle material from the second pass was sent for a third pass under the same operating conditions as for the second pass, except that the charging rate was reduced to 4:5. The gas make was 5.5% by weight and the coke deposit on the catalyst 3.3%, and the products were topped to obtain a %'yield of 73.7 octane gasoline. The overall yield for the three passes was 73% of gasoline with an octane rating of 72 (C. F. R.. Motor Method). There was approximately 20% of recyclematerial remaining having an A. P. I. gravity of 40, a boiling range of 315 to 470, and

an octane rating of 50.

The 35% bottoms of the East Texas naphtha were catalytically converted separately as fcl-` lows: The first pass was made at a charging rate of 3:5 with 5% steam to catalyst of the above described type. under 65 pounds pressure at a temperature of 882 F. for 45 minutes. The gas make'was'7% and the coke deposit 1%, and 48% `oi' 80 (C. F. R. Motor'Method) The ilnal yieldv for the three passes from the 35%,.bottom cut l of East. Texas naphtha was 83% of 80 octane gasoline and 13% oi' recycle material of 50 octane v rating.`

The total average yield from the reforming operation on both cuts of the original heavy naphtha was 76.3% of gasoline of 76 octane rating (C. F. R. Motor Method). The bottoms left, suitable'for recycling, comprised 17.5% of the original charge with a 50 octane rating.

Second example A California naplitha of 40.5 A. P. I. gravity, with a boiling range of 300 to 495 and an octane rating of 32, was divided into a light cut of approximately 35%, having a gravity of 46.8, and

-a boiling range of 300 to 375, with an octane minutes, producing 4.5% of gas and 1% coke and yielding 40% of 76 octane gasoline. The

bottoms from-the ilrst pass were subjected to a second pass under the same conditions, except that the feed rate was 4:5 and produced 4.4% gas and 1% coke, with a yield of 39.6% gasoline of 76 octane. 'Ihe bottoms from the second pass were subjected to a third pass under the same operating conditions as the first pass, except that the temperature was raised to 900 F. I'he gas make was 5% and the coke deposit 1.2%, the yield being 38.2% of 76 octane rating. The total yield for the light cut was 76% of 76 octane gasoline (C. F. R.. Motor Method) and about 20% of recycle material having an octane rating of 50.

For lthe heavy cut of California naphtha,- the first pass was made on the catalyst at 875 F. at a charging rate of 4:5 under 55 pounds pressure with 5% of steam for 45 minutes. 6% of gas was produced and there was a coke deposit of 2% on the catalyst. The products were subjected to fractionation, obtaining an overhead cut of'40% gasoline of 80- octane rating. The bottoms vsfrom. the rst pass were subjected to a second-pass under the same conditions producing 6.2% gas, a coke deposit of 1.8% and yielding 41% of 80 octane gasoline. The third pass was made at' 900' F., the other conditions being the same and the gas make was 6.1%, the coke deposit 2.1% and the yield of 80 octane gasoline was 38.7%. 'I'he total yield for the heavy cut was 75% of 80 octane gasoline (C. F. R. Motor Method) and 18% of recycle material of 50 octane.

When the products from both cuts were blended, the total yield for-the Caifornia naph` tha reformed was 75.35% of 78 octane gasoline and 18.7% of heavy material suitable for further recycling of 50 octane rating.

` Third example original material, was subjected to four passes.

The rst pass was sent to a catalyst of the above described type maintained at 875 F. at a charging rate of 7:10 with 2% of steam under 75 pounds pressurefor 60 minutes. The gas make was 7%, the` coke deposit on the catalyst 1.5%, and the products, when topped, yielded 25% of gasoline of 72 octane rating (C. F. R. Motor Method). 'Ihe second pass was at the rate of 4:5, with the catalyst at 900 F., the other conditions being the same, producing 6.8% of gas, a coke deposit of 1.4%, and yielding-23.2% of 72 octane gasoline. The third pass was nade at 4 the rate of 7:10 under conditions otherwise the same as in the second pass, producing 7.2% of gas, a coke deposit of 1.6%, and yielding 24.5% of 72 octane gasoline. The fourth pass was made under the same conditions as the third, with a gas make of 6.8%, a coke deposit of 1.6%, and yielding 23.5% of 72 octane gasoline. The nal yields for the four passes of the light cut were 61% of 72 octane gasoline (C. F. R. Motor Method) and 24% of bottoms or recycle material of 0 octane rating.

'I'he heavy Michigan cut, comprising 35% of the original material, was subjected to three passes. The first pass was made on catalyst of the above described type at 875 F. at a charging rate of 4:5 with 5% steam at 55 pounds pressure for 4,5,.minutes. I'he gas make was 7.5, the coke deposit 2%, and the yield was 32% of 72 octane 4gasoline (C. F. R. Motor Method). The secondV pass was made on the catalyst at 900 F., at a charging rate of 7:10, with 5% steam and under` 65 poundsV pressure, producing a gas make of 7.8%, a coke deposit of 2.8% and yielding 28.5% of 74 octane gasoline. The third pass was made under the same conditions as the second pass with a gas make of 7.7%, a coke deposit of 2.9%, andthe yield was 28% of 74 octane gasoline. The total yield of the three passes of the heavy cut was 61.5% of 73 octane gasoline (C. F. R. Motor Method) and the bottoms or recycle material of -0 octane which remained was 29.5%.

The products of both the heavy and the light cuts, after reforming, when blended, gave 61.2% of 72 octane gasoline and 25.9% of bottoms suitable for further recycling of -0 octane rating.

The gas produced from all operations in accordance with the present invention is of high quality. Itfhas a high specic gravity (1.3 to 1.5) and a high olenic content. By removing from the gas all of theconstituents which are in the gasoline boiling range. such as butane and heavier, a considerable quantity of gasoline of a very high octane rating, over 90 (C. F. R. MctmA Method) can be recovered which is suitable for blending with the reformed naphtha or with other gasoline. Also, the oleflns contained in the gas can be polymerized to produce a further yield of gasoline of high octane number. By these means, the total yield of high octane gasoline can be raised, in some cases, as much as 8 to 10%, and the octane number by two points.

In order to determine where to cut the product to separate out the transformed material of the desired octane rating, it is customary to make an experimental run on laboratory apparatus with the charging stock under suitable predetermined conditions. It is then found, for example, that a overhead fraction gives an 80 octane, that a deeper cut such as 46% gives 77 octane,

and that a still deeper cut such as 56% will give a 73 octane. 'I'hus it is possible to'cut for a definite octane value of the reformedy material, or to obtain a denite yield, as taking the octane improvement which such a yield offers.

I claim as my invention:

` 1. In the reforming of a naphtha charge to improve its antiknock characteristics, the process which comprises dividing the charge into a plurality of fractions of dierent boiling range characteristics, each having a boiling range of not more than 125 F., subjecting each of said fractions to a separate reforming operation, each of said operations involving treating the respective naphtha fraction in a'plurality of separate reaction steps, the low boiling portions of the products from each reaction step which have an octane rating above approximately 70 C. F.- R. M. M. being separated from the remaining higher boiling or bottoms fraction before the latter is subjected to the next succeeding reaction step, each of said steps being effected in a reaction zone containing a catalyst comprising'a blend of silica and alumina and being maintained under a superatmospheric pressure not greater than approximately 300 lbs/sq. in. gauge, and at a temperature within the range of 850 to 925 F., and blending the products of each of the reforming steps having an `octane rating above approxi'- mately 70 C. F. R. M. M. to provide a high yield of high quality product from said naphtha charge and a low concomitant `production of coke and fixed gas.

2. In the reforming of a naphtha charge to improve its antiknock characteristics, the process which comprises dividing the charge into a plurality of fractions of different boiling range characteristics, a predominant proportion of each boiling within a range of not more than 100 F., subjecting each fraction separately, in at least one confined reaction zone, to the action of an adsorptive contact mass contained therein, said mass comprising a blend of silica and alumina with the permissible addition of other active material and being maintained at a superatmospheric pressure not greater than approximately 300 lbs./sq. in gauge and at a temperature approximately within the range of 850 to 925 F., and blending together at least a portion of the products from the said reaction zones having an octane rating above a predetermined satisfactory minimum so as to effect the desired improvement in anti-knock characteristics of low boiling components as well as of high boiling components of the aforesaid charge while keeping the concomitant production of coke and fixed gases at a low amount in proportion to the amount of said charge. i

3. In the reforming of a naphtha charge boiling substantiallycompletely below approximately 450 F. to improve its antiknock characteristics,

the process which comprises dividing the naph charge into at least two fractions of different boiling range characteristics, a first fraction boiling predominantly above 375' 1 and a second fraction boiling predominantly below 375 1'. and subjecting each fraction to a separate plurality of reforming steps in separate reaction zones held at progressively increasing temperatures, the lower boiling fractionjof the products from each. of

` said reaction zones having an octane rating above a predetermined minimum being separated from the remaining or bottoms fraction lbefore the latter is subjected to the next succeeding reaction step, each step being effected in a reaction zone containing an adsorptive contact masscomprising a blend of silica. and'alumina and being main- 4tained under a superatmospheric pressure not greater than approximately 300 lha/sq. in. gauge and at a temperature substantially within the range of 850v to 925 F.

` 4. In the reforming of a naphtha charge boiling substantially completely below approximately 450 F. to improve its antiknock characteristics,

the range of 850 to 925 F. and under superatmospheric pressure, and blending together portions of the products of the higher and lower boiling fractions of said charge which have an octane rating above a predetermined satisfactory minimum so as to arrive at a high yield of high quality product while keeping the concomitant production of coke and fixed gases at a low amount in proportion to the amount of the aforesaid charge.

5. In the reforming of a naphtha fraction to improve its anti-knock characteristics, the process which comprises subjecting the naphtha in straight passes to a first reforming step at a temperature of about 875 F., fractlonating the products of the f'lrst reforming step so as to obtain an overhead fraction of at least 70 octane rating C. F. R. M. M. and a first bottoms fraction, subjecting said first bottoms fraction to a second separate reforming step at a temperature of about 900 F., fractionating the products of said second reforming step so asY to obtain an overhead fraction of at least 70 octane rating C. F. R. M. M.

land a second bottoms fraction, passing said second bottoms fraction to a third reforming step wherein it is subjected to a temperature of about 925 F.l and separating the products of said third reforming step into an overhead fraction of at least 70 octane rating C. F. R. M. M. and a lower octane bottoms fraction, each of said reforming steps being conducted under a suitable superatmospheric pressure of the order of approximately 75 lbs./sq. in. gauge and in the presence'of catalytic masses, eachl comprising essentially blends of silica and alumina having a weight ratio of silica to alumina of at least approximately 4 to l.

6. In the reforming of a naphtha charge boiling substantially completely below approximately 450 F. to improvepits antiknock characteristics, the process whichcomprises dividing the naphtha charge into at least two fractions of Vdifferent boiling range characteristics, a first fraction boiling predominantly above 375 F. and a second fraction boiling predominantly below 375 F., subjecting said first fraction in successive passes to a rst reforming step at ay temperature of about 875 F., fractionating the products of the first reforming step so as to obtain an overhead fraction of at least 70 octane rating C. F.'R. M. M. and a first bottoms fraction,y subjecting said rst bottoms fraction to a second separate reforming operation at a temperature of about 900 F., fractionating the products of the second reforming step or operation so as to obtain an overhead fraction of at least 70 octane rating C. F. R. M. M. and a second bottoms fraction, passing said second bottoms fraction to a third reforming step wherein it is subjected to a temperature of about i925 F.

and separating the products of said third reforming step into an overhead fraction of at least 70 octane rating C. F. R. M. M. and Ya lowe octane bottoms fraction, and subjecting the aforesaid second fraction to at least one separate reforming step, each of said reforming steps being conducted under the suitable superatmospheric pressure of the order of approximately '75 lbs ./sq. in. gauge and in the presence of catalytic masses, each comprising essentially blends of silicay and alumina having weight ratio of silica to alumina of at least approximately 4 to 1.

EUGENE J. HODRY.

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