US2394797A - Process for the production of a blending fuel - Google Patents

Description

Feb. 12, 1946. 5. H. M ALLlSTER ETAL 2,394,797

PROCESS FOR THE PRODUCTION OF A BLENDING FUEL Filed Oct. 20; 1943 2 Sheets-Sheet 1 Blending Fuel Al Y ksomzriza'lion Fig. 1

lnvzznrorszsumnzr H. McAlfis'ter Norman E. Pz'crg Feb. '12, 1946. s. H. MQALLISTER E1. AL 2,394,797

PROCESS FOR THE PRODUCTION OF A BLENDING FUEL Filed Oct. 20, 1943 2 Sheets-Sheet 2 ESL v lnvehl'ors'. Sumner H. McAllisTer Norman E. Peer- 3 Bg +he'ar-At'rornzg QIZZ Patente d Feb. 12, 1946 PROCESS FOR THE PRODUCTION OF A BLENDING FUEL Sumner H. McAllister, Lafayette, and Norman E. Peery, San Francisco, Calif., assignors to Shell Development Company, San Francisco, Calif a corporation of Delaware A'pplication October 20, .1943, Serial No. 507,220

\ .6 Claims.

. This invention relates to a new and improved blending fuel of exceptionally desirable volatility and ignition characteristics and to a Pr ce f r its production.

As is wel1 known, there is a great .demand for gasoline-type fuels of high performance rating,.

especially for use under rich mixture supercharged conditions. These fuels are presently prepared by blending certain selected stocks and then adding tetraethyl lead. For example, a base stock may be blended with iso-octane or alkylate and then about 3 cc. of tetraethyl lead addedper gallon. This method of producing these fuels is limited by several factors, one of the most important of which is the matter of volatility. It is necessary to maintain a certain balance ,of hydrocarbon constituents in such fuels in order to have a suitable volatility. Therefore, the amount of higher boiling constituents which may be used is strictly limited, and it is generally, necessary to use considerable amounts of lower boiling material. There is, however, no available supply of good material for this purpose. The materials generally employed at present are selected straight run gasoline fractions and substantially saturated fractionsof catalytically cracked gasoline. These and other available lower boiling hydrocarbon fractions have, however, relatively poor performance ratings and poor blending values, especially under rich mixture supercharged con- This is'due to the fact that'the isomerization to neohexane requires conditions which ar much more severe than those practical for the isomerization of normal hexane to isohexane, and, in order to apply these conditions, a very strong suppressor of degradation must be applied. Also, it

is found to be very diillcult to produce practical yields of neohexane directly from normal hexane in one step.

Th blending fuel of the present invention is a high performance fraction, consisting predominantly of neohexane and. cyclopentane. This blending fuel, although consisting largely of two hyrocarbons, behaves as a single hydrocarbon.

Thus, it may be distilled and .handled as if it consisted of neohexane alone. It is furthermore quite superior to neohexane alone as a blending fuel, especially for fuels designed for use under rich mixture supercharged conditions.

dltions, and their use in considerable concentrations materially lowers the performance rating of .the blend.

One material which is ideally suited for this purpose is neohexane (2,2-dimethyl butane). It has the desired volatility, exceptionally high performance rating, high blending value, and high lead susceptibility. This material was produced for a short while in limited quantities by a thermal alkylation process. This method proved to be uneconomical and is no longer used. Considerable work has been done in attempts to produce neohexane by catalytic isomerization of normal hexane, but up to the present time no such process has been developed to large scale commercial use.

Although the isomerization. of normal paraffin hydrocarbons including normal hexane is de-- scribed in a number of patents and it is generally .stated that the processes are suitable for the isomerization of normal paraflin hydrocarbons to their branched isomers and the isomerization of branched isomers to more highly branched isomers, these processes do not, under the conditions shown, produce practical yields of neohexane.

According to the process of the invention, this superior blending fuel is produced directly from available materials by the practical combination of process steps hereinafter described. To aid in the description, reference is had to the attached drawing wherein there is shown by conventional figures aflow diagram of a suitable modification of the process of the invention.

The blending stocks of the invention may be produced, according to the process ofthe invention, from straight run gasolines of naphthenic character. Suitable naphthenic straight run gasolines are obtained from most western and Mid- Continent petroleums. These straight run gasolines contain appreciable quantities of cycloparaflin hydrocarbons along with normal parafiln hydrocarbons. While it is preferred for practical reasons to produce the blending fuels of the invention from such straight run naphthenic gasoline, it is, of course, possible to start with materials of similar composition regardless of their origin.

The straight run gasoline fraction normally containing normal pentane, normal hexane, normal heptane, cyclopentane, methyl cyclopentane.

dimethyl cyclopentane, cyclohexane, and minoramounts of the other usual components of approximately equal boiling points is first fractionally distilled to separate a cyclopentane fraction and a normal hexane fraction. In view of the complexity of these straight run gasolines, it is practically impossible to separate these hydrocarbon components in a pure state by fractional distillation. As will be pointed out, however, separation of the pure hydrocarbons is neither necessary nor desirable. It will be understood, therefore, that throughout the present description, when referring to a cyclopentane fraction or a normal hexane fraction, commercial relatively narrow boiling fractions containing most of and consisting largely of the designated component are meant. Referring to the drawin s (Figure I), the straight run gasoline entering via I is subjected to a fractional distillation in a fractionator 2 to remove lower boiling components, chiefly pentane. This lower boiling fraction, boiling for instance up to between about 40 C. and 49 C., is removed overhead via line 3. The heavier fraction is then subjected to a second fractional distillation in fractionator 4 to separate and remove a cyclopentane fraction. This fraction is cut to' and'a higher boiling fraction which may be re- 1 turned to the refinery via line '6. This normal hexane fraction contains appreciable concentrations of methyl cyclopentane as well as minor amounts of cyclohexane and 1,1-dimethyl cyclopentane, and possibly some dimethyl pentanes, if these latter hydrocarbons happen to be present in appreciable concentrations in the feed. The fraction, however, is preferably substantially free of heptanes, particularly normal heptane.

It may boil up to about 69 C. to 81 C. A very suitable fraction boils, for instance, between about 65 C. and 75 C. I

The normal hexane fraction taken overhead via line I is catalyt cally isomerized in an isomerization unit 8 under conditions conducive to the 'more or less selective conversion of normal hex ane to methyl pentanes, while taking advantage of the inhibitingv action of the naturally occurring cycloparamn upon degradation reactions. The product from the isomerization is subjected to a fractional distillation to separate a lower boiling fraction boiling up to 63 C. to 68 C. and a higher boiling fraction boiling above 63 C. to 68 C. The higher boiling fraction contains substantially all of the isomerized and unisomerized cycloparaflin hydrocarbons present and the unisomerized normal hexane. This may be effected in a fractionator 9 as illustrated in Figure I or it may be effected by recycling the isomerizate back to the fractionator 4 as illustrated in Figure II. If the product from the isomerizat on treatment is fractionated in, a separate fractionator 9, as illustrated in Figure I, the higher boiling fraction may be recycled to the isomerization unit 8 via l ne In or may be withdrawn via line I I. Also, it may. if desired, be refractionated in fractionator l2 to separate the unisomerized normal hexane from the bulk of the cycloparaflins. which fract ons may, if desired,-be recycled in any proportion to the isomerization unit 8 in order to control the concentration of cycloparaflin inhibitor therein.

The lower boiling fract on from the product of the isomerization treatment contains the iso-paraiiin produced in the isomerization treatment. This fraction consists largely of 2-methyl pentane and v3-methyl pentane, and issubstantially free of methyl cyclopentane, cyclohexane and normal hexane. In some cases, small amounts of 2,2- dimethyl butane and/or 2,3-dimethyl butane m y be formed in the isomerization. These compounds, if formed, are also included in this lower boiling fraction.

The lower boiling fraction from the product of the isomerization treatment is subjected to a separate isomerization treatment in isomerization unit l3 in admixture with the cyclopentane fraction from fractionator 4 to more or less selectively isomerize the methyl pentanesto n'eohexane. Thus, if the product from the isomerization treatment is fractionated in a separate fractionator 9 as illustrated in Figure I, the lower boiling fraction is blended with the lower boiling fraction from fractionator 4. If, on the other hand, the fractionation of the product from the isomerization treatment is effected in fractionator 4, as illustrated in Figure II, the total overhead fraction from this, fractionator is sent to the second isomerization unit 13.

The product from isomerization unit [3 is fractionated in a fractionator M to separate a lower boiling. fraction boiling up to 50 C. to 59 C. and a higher boiling fraction boiling above 50 C. to 59 C. The lower boiling fraction consists es-. sentially of neohexane and the cyclopentane which passes through the isomerization zone unchanged. The concentration of cyclopentane in the fraction depends upon the amount of cyclopentane introduced into the isomerization zone and upon the conversion of methyl pentanes to neohexane obtained' In general, it is at least 5% and below 75%, the remainder being substantially neohexane.

Thehigher boiling fraction from fractionator l4 consists essentially of unisomerized methyl pentanes .and small amounts of normal hexane formed by reversedvisomerization. This fraction may be withdrawn via line IE but is preferably recycled in whole or in part to one of the isomerization zones. This may be done directly or the fraction may be further fractionated in a fractionator l6 into a normal hexane fraction and a methyl pentane fraction, which fractions may be separately recycled in whole or in part to the first and second isomerization zones, respectively.

The lower boiling fraction from fractionator I4 is a blending fuel of exceptionally valuable and desirable properties. It distills like a single hydrocarbon boiling at about 50 C. and has therefore an excellent-and highly desired volatility.

' Furthermore, it has an exceptionally high blending value and high lead susceptibility. The A. S. T. M. octanegiumbers of the major components, neohexane and cyclopentane, are 94 and 89, respectively. It would be expected therefore that the blending fuel would be inferior to neohexane per se. The performance number'of the blending fuel is, however, between about and 227, and generally about to 178. Pure .neohexane, on the other hand, has a performance number of about 145. [Performance number is the per centpower output of the blending fuel compared to iso-octane when tested in a leaded (4 cc. TEL) blend in a 30 engine, as specified by the U. S. Army Air Corps] It is thus seen that in terms of performance the present blending fuels are considerably superior tov neohexane.

The process of the invention described above not only produces superior base stocks but prodiices a greater yield of base stock of given quality per volume of feed stock. This is due largely to the fact that the isomerization of normal hexane to neohexane is eflected in two more or In the first isomerization step, certain cycloparaflln hydrocarbons, which are easily separable from the isoparafiins formed, are used to depress degradation reactions and to thereby allow the isomerization to be carried out more or less selectively under conditions affording high production rates. In such cases where the concentration of naturally occurring eycloparafiins in the feed are insuiiicient to give the optimum results, the concentration in the isomerization zone is built up by the recycling .of a suitable amount of these cycloparaflins separated from the product from the first isomerization treatment. In the second isomerization step, the isomerization is effected under drastic conditions in the substantial absence of normal hexane while depressing degradation reactions with the cyclopentane separated prior to the first isomerization step. This cycloparafiin is very resistant to the action of the isomerization catalyst and is an especially advantageous degradation inhibitor for use under the drastic conditions required in the second isomerization step.

The isomerization steps involved in theabovedescribed process will now be more particularly described.

The isomerizations are preferably carried out in the liquid phase. Any of the known liquid phase isomerization systems may be employed.

The preferred catalysts for effecting the isomerization are anhydrous aluminum chloride. and

aluminum bromide; however, other isomerization catalysts of the Friedel-Crafts type may be employed, particularly in the first isomerization step. Suitable aluminum chloride isomerization catalysts are, for example, aluminum chloride lumps, aluminum chloride deposited upon inert carrier materials, aluminum chloride complexes of the Gustavson and Ansolvo acid types, aluminum chloride suspensions in aluminumchloridehydrocarbon complexes, and composites of aluminum chloride with certain other metal halides.

. of cycloparaflins of about or above.

130 C. 'I'hecontact times are generally between about 2 and 25 minutes. The concentrations of hydrogen halide promoter are generally between about 1% and 10% of the hydrocarbon feed. Under suitable conditions chosen within these limits degradation is repressed by concentrations high concentrations of cycloparafilns, for instance above about 50%, are not only unnecessary but are also undesirable in the first isomerization step since they materially reduce the production capacity of the isomerization reactor.

Degradation may be also repressed by the use of suitable pressures of hydrogen. Degradation is, however, most effectively inhibited by the combined action of the cycloparafiin hydrocarbons and hydrogen. Thus, in the, preferred embodiment of the invention the isomerization steps are carried out under appreciable partial pressures of hydrogen, for instance, partial pressures between about 2 and 40 atmospheres. While it appears most economical at present to carry out the first isomerization step with a minimum of degradation and in the preferred embodiment of the invention degradation to lower and higher boiling products is maintained below about 5% (based on the feed), it may be practical under certain circumstances to allow the degradation to exceed this amount. Typical isomerization conditions for the first isomerization and typical results of this treatment are shown in the following ex- Suitable catalysts are described in U. S. Patents 2,208,362; 2.250,118; 2,291,376; 2,306,261;

2,169,494; 2,216,221; 2,223,180; and 2,225,776; and.

in U. S. applications Serial Nos. 425,779; 428,116;

now U. s, Patents 2,342,073 and 2,327,670, re-

spectively; and in U. S. applications Serial Nos. 428,852; and 428,862. Especially suitable and preferred catalysts are those described and claimed in copending application Serial No. 363,676, filed October 31, 1940, now U. S. Patent No. 2,370,195, issued February 27, 1945, consisting of a molten mixture comprising aluminum' halide and a metal halide which does not react with the aluminum halide, said metal halide being in molecular excess with respect to the aluminum halide. A preferred catalyst of this type is a hydrogen chloride-treated mixture of from about 80 to about 99 parts of antimony trichloride and from about 20 to about 1 part of aluminum chloride.

In order to obtain optimum results the severity of the reaction conditions should be carefully controlled. The severity of the conditions depends upon the following factors: the temperature, the degree and time of contact, the activity of the catalyst, the kind and concentration of degradation inhibitors present, and the concentration of promoter. These factors, which are to a large extent interdependent, are adjusted according to,

amples:

Example I From a naphthenic straight run gasoline there was separated by fractional distillationa fraction boiling between about 64 C. and 73 C. This fraction, after acid washing to remove traces of aromatic hydrocarbons, contained:

Per cent Isohexanes About 5 Normal hexane About 59.5 Methyl cyclopentane About 35.5

This fraction was treated in a continuous manner in a mixing autoclave with a molten catalyst consisting of aluminum chloride, antimony chloride and hydrogen chloride. The aluminum chloride and hydrogen chloride were added with the feed. The reaction conditions were as follows:

Temperature 80 C. Phase ratio of catalyst to hydrocarbon in the reactor 1:5 Feed rate of AlCla 2.4 g./hr. Feed rate of hydrocarbon 2.57 kg./hr.

Promoter HCl, 4.2% based on the hydrocarbon feed Contact time About 13 minutes Pressure 375 p. s. i.

Partial pressure of hydrogen About 225 p. s. i.

The product contained:

The production of methyl pentanes was about 228 grams per gram of aluminum chloride.

Example If The same hydrocarbon fraction as used in Very 4 aaomov. 4

to produce a blend having the iollowing composi- Example I was treated in the same manner under the following conditions:'

Temperatur Phase ratio of catalyst tohydrocarbon in the reactor 2:1 Feed rate of A101: 6 g./hr. Feed rate of hydrocarbon 2.6 kg./hr. Promoter HCl, 5.6% based on the hydrocarbon feed Contact time About 5.3 minutes Pressure 210 p. s. 1.

Partial pressure of hydrogen About 40 p. s. i.

The product contained:

, Per cent Nenhmmnn 6 2,3-dimethyl butane and methyl pentanes--- 33 Normal hexane 26 Methyl cyclopentane 10.1 Cyclohexane 23.5

Higher boiling products 1.4

The production of methyl pentanes was about 113 grams per gram of aluminum chloride.

Th second isomerization i carried out under conditions within the above-specified limits correlated to give relatively more severe conditions.

Although the conditions may be made more severe by increasing the temperature, it is more advantageously done by increasing the contact and/or by increasing the concentration of hydrogen haiide promoter and/or by increasing the activity of th catalyst. Thus, instead of employing a molten catalyst containing about 0.5%2% aluminum chloridein antimony trichloride', a similar catalyst containing about 2%-7% aluminum chloride may advantageously be employed. One set of particularly suitable conditions for the second isomerization is, for example:

Catalyst A molten mixture comprising antimony trichloride 97'%-98%, aluminum chloride 2%- 3% (+hydrogen chlo- These conditions may be altered considerably, due consideration being given to the interdependency of the variables.

Example 111 d A product produced in a. first isomerization step as described above was fractionated to separate a methyl pentane fraction having the following composition:

Per cent Cyclopentane Neohexane 0.6 Methyl pentanes 91.0 Normal hexane 7.4 Methyl cyclopentane 0.9

This fraction was blended fith about 14% of a cyclopentane fraction obtained as described above tion:

Per cent Cyclopentane 12.4 Neohexane 2.3 Methyl pentanes 77.3 Normalhexa 6.3 Methyl cyclopentane 0.8

This blend was isomerized under the followin conditions:

Catalyst A molten mixture comprising antimony trichloride 98%, aluminum chloride 2% (+hydrogen chloride) Temperature 80 C. Contact time 15 minutes Phase ratio of catalyst to hydrocarv bon in the reactor 1:4.5

Promoter HCl, 4.2% based on the feed Partial pressure of hydrogen 100 p. s. i. Average total operating pressure 320 p. at

The product was found to contain:

- Per cent Butane 1.9 Pentan 5.0 Cyclopentane -s 9.7 Neohexane 22.4 Methyl pentanes "42.5 1 Normal hexane and heavier. 18.5

pentane fraction, a product having the following composition is obtained:

Per cent Butane 2.8' Pentane -s 5.3 Cyclopentane 0 Neohexane 3.1 Methyl pentanes 63.5 Normal hexane and heavier 25.3

We claim as our invention:

1. A process for the production of a blending fuel from substantially saturated naphthenic gasoline which comprises separating from the naphthenic gasoline a lower boiling fraction boiling up to about 50 C.-65 C. containing naturally occurring cyclopentane and being substantially,

free of normal paraffin hydrocarbons, also a normal hexane fraction boiling up to about 69 C.-- 81 0. containing naturally occurring normal hexane and cycloparafiin hydrocarbons and being substantially free of normal heptane, subjecting.

said hexane fraction to a liquid phase catalytic isomerization treatment with a Friedel-Crafts type isomerization catalyst under conditions chosen to afford isomerization of normal hexane to methyl pentane as the predominant reaction,

separating from the product of said isomerization treatment a methyl pentane fraction substantially free of normal hexane, subjecting said methyl and cyclopentane.

2= A process for the production of a blending fuel from substantially saturated naphthenic gasolines which comprises separating from the naphthenic gasoline a lower boiling fraction boiling up.

to about 50 C.-65 0.. containing naturally occurring cyclopentane and being substantially free of normal parafiin hydrocarbona also a normal hexane fraction boiling up to about 69 C.-81 C. containing naturally occurring normal hexane and cycloparaffin hydrocarbons and being substantially free or normal heptane, subjecting said hexane fraction to a liquid phase catalytic isomerization treatment with a Friedel-Crafts type isomerization catalyst under conditions chosen to afford isomerization of normal hexane to methyl pentanes as the predominant reaction,

separating from the product of said isomerization treatment a methyl pentane fraction substantially free of normal hexane, subjecting said methyl pentane fraction in admixture with said first lower boiling fraction to a liquid phase catalytic isomerization treatment with a Friedel-Crafts type isomerization catalyst under conditions chosen to afiord isomerization oi. methyl pentanes to neohexane as the predominant reaction, and separating from the product of said second isomerizaticn a fraction boiling up to about 50 C. 59" C. consisting essentially of neohexane and cyclopentane. r

3. A process for the production of a blending fuel from substantially saturated naphthenic gasolines which comprises separating from the naphthenic gasoline a lower boiling fraction boiling up to about 50 C.65 C. containing naturally occurring cyclopentane and being substantially free of normal paraffin hydrocarbons, also a normal hexane fraction boiling up to about 69 C.- 81 C. containing naturally occurring normal hexane and cycloparaflin hydrocarbons and being substantially free of normal heptane, subjecting said hexane fraction to a liquid phase catalytic isomerization treatment with a Friedel-Crai'ts type isomerization catalyst under conditions chosen to afford isomerization of normal hexane to methyl pentane as the predominant reaction, separating from the product of said isomerization treatment a methyl pentane fraction substantially free ofnormal hexane, subjecting said methyl pentane fraction in admixture with said first lower boiling fraction to a liquid phase catalytic isomerization treatment with an aluminum chloride isomerization catalyst under conditions chosen to afford isomerization of methyl pentanes to neohexane as the predominant reaction, and separating from the product of said second isomerization a traction boiling up to about 50 C.- 59 C. consisting essentially of neohexane and cyclopentane.

4. A process for the production of a blending fuel from substantially saturated naphthenic gasolines which comprises separating from the naphthenic gasoline a lower boiling fraction boiling up to about 50 C.-65 C. containing naturally occurring cyclopentane and being substantially tree of normal paraflln hydrocarbons, also a normal hexane fraction boiling up to about 69 C.-81 0. containing naturally occurring normal hexane and cycloparafiln hydrocarbons and being substantially free of normal heptane, subjecting said hexane fraction to a liquid phase catalytic isomerization treatment with an aluminum chlo-' ride isomerization catalyst under conditions chosen to afford isomerization of normal hexane to methyl pentane as the predominant reaction, separating from the-product of said isomerization treatment a methyl pentane traction substantially, free of normal hexane, subjecting said methyl pentane fraction in admixture with said first lower boiling fraction to a liquid phase catalytic isomerization treatment with an aluminum chloride isomerization catalyst under conditions chosen to afford isomerization of methyl pentanes to neohexane as the predominant reaction, and separating from the product of said second isomerization a fraction boiling up to about 50 C.-59 C. consisting essentially of neohexane and cyclopentane.

5. A process for the production of a blendin drocarbons having six carbon atoms substantially free of normal heptane in said primary fractionating zone, subjecting said hexane fraction to a liquid phase catalytic isomerization treatment with a Friedel-Crafts isomerization catalyst under conditions chosen to afiord isomerization of normal hexane to methyl pentanes as the predominant reaction, passing the resulting isomerization product from said isomerization treatment to said'primary fractionating zone, subjecting said lower boiling fraction to a separate liquid phase catalytic isomerization treatment with a Friedel-Crafts type isomerization catalyst under conditions chosen to afiord isomerization of methyl pentanes to neohexane as the predominant reaction, and separating from the product substantially free of normal hexane, subjecting of said second isomerization a'fraction boiling up to about 50 C.-59 C., consisting essentially of neohexane and cyclopentane.

6. A process for the production of a blending fuel from substantially saturated naphthenic gasoline which comprises separating from said naphthenic gasoline a lower boiling'ifraction boiling up to about 50 C.-65 C. containing naturally occurring cyclopentane substantially free of normal paramn hydrocarbons and a normal hexane fraction boiling up to about 69 C.-8l C. containing naturally occurring normal hexane and ,cycloparaflin hydrocarbons substantially free of normal heptane, subjecting said hexane fraction to a liquid phase catalytic isomerization-treatment with a Friedel-Crafts type isomerization catalyst in a first isomerization zone under conditions chosen to aflord isomerization of normal hexane to methyl pentanes as the predominant reaction, separating from the efliuent of said first isomerization zone a methyl pentane traction 6 a I asomav said methyl pentane traction-in-admixture with in: up to about n i ting essensaid first lower boiling fraction to a liquid phase tially oi neohexane and'cyclopentane and a higher catalytic isonierization treatment with a Friedel- .boiling fraction boiling above about 50 c.-65 0., Crafts type catalyst in a second isomerization and recycling at least a part of said 1ast-menzone under conditions chosen to afford isomerlzao tioned higher boiling fraction to said first isomtlon or metlwl pentanes to neohexane as the preerization zone. dominant reaction, separating from the emuent UMNER H. McALLISTER. 0! said second isomerizatlon zone a fraction boil- NOR-MAN E- PEERY.

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