US2391962A - Manufacture of motor fuels - Google Patents

Description

Jan. l, 1946.

A. R. G-OLDSBY MANUFACTRE 0F MOTOR FUELS Filed April 21, 1942 ARTHUR R.GLDsBY v l() INVENTOR H l s A TTORNEY BY w Patented Jan. 1, 1946 rss PATENT i trios ACTURE 0F MTOB. FUELS Application April 21, 1942, Seriali No. 439,821

(Cl. iSd-49) 3 Claims.

This invention relates to the treatment of cracked naphtha for the production of high grade motor fuel of high antilmock quality.

The gasoline product produced in commercial thermal cracking processes does not ordinarily have an octane value in excess ci about '7o-72 A. S. 'I'. M. and considerable quantities of cracked gasoline produced in the thermal cracking procv esses, particularly the cracked gasolines produced in viscosity breaking and coking operations, have antiknock values below 70 octane. My invention contemplates the treatment of such cracked naphthas to produce high yields 'of products having octane values oi the order of Bil-90 and to produce motor fuel aviation motor fuel.

In accordance with the invention the cracked gasoline is treated with'a selective solvent to sep'- arate parains from olens, the paramnic fraction is subjected to thermal or catalytic reform-- ing or to hydroforming or paramn isomerization and the olenic fraction is subjected to oleiin isomerization or isoiorming.

In a preferred embodiment of the invention the parafilnic fraction, obtained in the solvent treatment of the cracked naphtha, is subjected to frac-` tionation to separate lower.; boiling or intermediate fractions rich in normal hydrocarbons, such as pentane and hexane, from higher boiling hydrocarbons. 'I'he lower boiling or intermediate parobtained in the solvent treatment, are subjected to catalytic isomerization. v

In aviation motor fuel it is desirable that the fuel contain relatively minor proportions of olen hydrocarbons and the invention contemplates a special method of treating the olenic fractions to reduce the olefin content thereof and increase susceptibility to tetraethyl lead. In accordance with the invention the cracked naphtha is treated with a selective solvent to obtain a ramnate fraction comprising parailln hydrocarbons and an extract fraction comprising oletln and aromatic hydrocarbons. The entire paradinic fraction is subjected to a conversion or reforming-treatment to raise the antilmock quality thereof, or is subjected to fractionation to obtain a lower boiling or intermediate fraction and a higher boiling fraction, and the lower 'boiling orintermediate fraction is subjected to a treatment to eil'ect isom'- f erization of normal paramn hydrocarbons. while the higher boiling fraction is subjected to reformproducts adapted for ivo ing or hydroforming to raise the antiknock quality thereof. The olefin-aromatic fraction, ob-

tained in the solvent treatment, may be subjected to a two-stage treatment, in the rst of which the fraction is subjected to treatment to effect isomerization of olen's and in the second of which the products from the nrst stage are subjected to a finishing treatment to eie'ct conversion of olefins to isoparans and to increase the lead susceptibility, orthe olefin-aromatic fraction may be subjected to a single-stage treatment in which it is subjected to treatment to eiect both an lsomerization of oleiins and a conversion of olenns to isoparafns and to effect reactions causing an increase in lead susceptibility.

The invention will be understood from the following description thereof, reference being had to the accompanying drawing which is a flow di-i -agram illustrating a particular embodiment of the invention.

Referring to the drawing, cracked naphtha is directed by a pump l0 to a treating vessel I! into which is introduced a selective solvent by a pump 9. Such solvents as sulfur dioxide, mixtures vof sulfur dioxide and methyl alcohol, benzyl alcohol, or diacetonc alcohol or phenol and mixtures of phenol and cresol are recommended as solvents to be used. The solvent treatment is ordinarily carried on in the liquid phase with sulfur -dioiiide at temperatures o'f 10 F. to 60 F. The v solvent treatment produces'a rainate fraction comprising paralns and an extract fraction comprising oleiins and aromatic's. The ramnate fraction is collected in a vessel l2 from which the solvent may be distilled oi through a line I3 and the extract fraction is collected in a vessel I4 from Awhich the solvent may be distilled oi through a line I5. In-using the phenol-cresol solvent the naphtha is introduced as a. vapor into the liquid solvent and an extracti've distillation is carried on, the paramns being removed as a vapor and the olens and aromatics remaining in the liquid.

The rainate or paraiilnic fraction is withdrawn from the vessel l2 through a line l6`hav ing branch lines Il and I8. Describing the operation when passing the paramnic fraction through the line I8, this fraction is directed'by a pump I9 through a line 2B to a fractionating. tower 2l wherein fractionation `takes place to separate from higher boiling constituents, a lower boiling parailnic fraction containing the parailln hydrocarbons which are especially susceptible to 'treatment for catalytic isomerization.

This low boiling fraction will ordinarily have an end point of 16o-170 F. so as to include the pentanes and hexanes which are well adapted for the isomerization treatment. The low boiling fraction taken off as a vapor from the tower 2l is condensed in the condenser 22 and collected as a distillate in the receiver 23. The pentanehexane fraction is Withdrawn through a line 24 and directed through either of branch lines 25 and 25. When the cracked gasoline contains a material quantity of isopentane it is desirable to remove the isopentane from the stock which is to be subjected to isomerization and for this purpose the pentane-hexane fraction is directed through the line 25 to a fractionator 21 from which the isopentane, together with any lighter fractions, is taken overhead to a condenser 28,

thence to a receiving drum 29. The pentanethrough a heating coil 45 thence to a reaction chamber 41 wherein the hydrocarbons are subjected to either thermal or catalytic reforming or to hydroforming. In the thermal reforming operation the gasoline fractions are subjected to temperatures upwards of 850 F., preferably temperatures of the order of 900 F. or 1000 F., under pressures usually within a range of'about 200 lbs. to 800 lbs. In the catalytic reforming operation the parafnnic constituents are subjected to temperatures of about 850-1000o F. under pressures of about 50-300 lbs. in the presence of catalysts such as bauxite or clays. In the hydroforming operation the paramnic hydrocaris directed through a branch line 3| v"for the isof merization treatment. The lines 5I, 26 and`3 0 communicate with a manifold line 32 so that either the entire parainic fraction obtained in the solvent treatment of the cracked naphtha or the entire light fraction obtained in fractionating the solvent treated parafflnic product or the pentane-hexane fraction from which the isopentanehas been removed may be utilized as the charge to the isomerization operation.

A pump 33 withdraws the paramnic fractions through line 32, from either of the lines 3l, 26

and 20, and directs the hydrocarbons through -a heating coil 34 thence to a contact or treating vessel 35. The catalyst employed therein comprises anhydrous metallic halides', particularly the chlorides and bromides of aluminum, usually,

with small amounts of hydrogen halides such as hydrogen chloride as a promoter. Aluminum chloride is the catalyst recommended. This catalyst is preferably used in the form of an aluminum chloride hydrocarbon complex and may be directed to the treating vessel through a line 36 while4 the hydrocarbons are introduced to the lower portion of the vessel and are caused to bubble up through the liquid complex, The operation is improved by the addition of hydrogen chloride, introduced through line 31, as well as hydrogen. introduced through line 38, under superatmospheric pressuressuch as about 150- 1000 lbs. The reaction is carried on at temperatures of about 150 F.-300 F. Complex may be withdrawn from time to time from the chamber through a line 39 and fresh aluminumchloride may be added to maintain catalyst activity. The treated hydrocarbons overflow to -a'settling vessel 40 from which any catalyst present may be withdrawn through a line 4I while the isomer-4 izate is withdrawn through a line 42. Gases -may be withdrawn through a gas release line `43.

In lieu of subjecting the paraiiinic fraction or pentane-hexane fractions thereof to catalytic isomerization the entire parafilnic fraction obtained in the solvent treatment or the 4higher y i'ractionator 2l may be directed bythe pump 44 bons are subjected to reaction temperatures in the presence of hydrogen and a suitable catalyst to effect reactions involving conversion of parafflnic hydrocarbons to aromatic hydrocarbons. The catalysts which are particularly recommended for hydroforming are molybdena-alumina catalysts and chrome-alumina catalysts. Temperatures of the order of 900 F. or 1000 F. under pressures of the order of 200-300 lbs. are

quite satisfactory for effecting the desired con Aboiling constituents of such fraction maybe subiected to thermal or catalytic reforming or hy-v version into higher antiknock hydrocarbons. The products of reaction pass from the reaction chamber 41 through a cooler 48 thence to an accumulating drum 49 from which the lighter gases, more particularly, the hydrogen and methane, may be withdrawn through a line 50 to a hydrogen accumulator 5I. A pump 52 directs the hydrogen-containing-gases to a heating coil 53 wherein the hydrogen-containing gases are preheated to approximately reaction temperatures before being combined with the heated parafilnic hydrocarbons passing from theheating coil 43 and the combined products are subjected to reaction temperatures in the presence of the molybdena-alumina or chrome-alumina catalyst in the reaction chamber 41. The reformate or hydroformate is withdrawn from the accumulator 40 through a line 54.

In the hydroforming operation an excess of hydrogen is'produd over that required for recycling to the hydroforming zone and in accordance with the invention hydrogen containing gases may be withdrawn from the accumulator II and directed by a'. pump 55 to the hydrogen line Il for4 introduction to the paraffin isomerization zone. Normally, suiilcient hydrogen is produced in the hydroforming operation to provide the hydrogen necessary for the paraffin iaomerization operation, as Well as for the finishing treatment which is described hereinafter.

' Referring no w to the treatment of the extract bons, is withdrawn from the chamber I4 through' a line 56 and is directed by a pump "through a heating coil 58 thence to a reaction chamber Il whereinthe" olefinlc hydrocarbons are subjected to isomerization or isoforming to effect a conversion o f olefin hydrocarbons into isomers thereof. The catalyst adapted for this isomerization operation consists advantageously of a synthetic silica-alumina type of catalyst, clay catalysts and vthe like. The catalyst may either be disposed as a stationary bed or fixed mass throughwhich the hydrocarbon vapors pass or'it may be used as' a powder in which case 'the hydrocarbon vapors are contacted with a stream of the powdered catalyst. Temperatures of the order'of 800 F. or 900-F. to 1000 F. with high space velocity and under moderate superatmospheric pressures preferably under 100 p. s. i. are employed. The lower temperatures have the advantage of effecting. the isomerlzation of the oleflns with a minimum of cracking and polymer formation. The products of reaction pass from the catalyst chamber 59 through a cooler thence to an accumulator or gas separator 6l. The liquid product collected in the accumulator Si consists largely of isomerized oleiins together with the aromatics contained in the charge to the isomerization unit.

The reformate or hydroformate produced in the thermal or catalytic reforming or hydroforming operation will ordinarily require some fractionation toremove polymer products of higher boiling point than desired for the gasoline or motor fuel product and also to remove normally gaseous hydrocarbons. For this purpose the reformate or hydroformate withdrawn from the accumulator s through line 50 is directed by a pump 62 to a rectifying tower S3 wherein the hydrocarbons are subjected to rectication to Produce a liquid product of desired vapor pressure. This liquid product may then be directed through a line 50 to a rerun still for the removal of any constituents oi higher b oiling point than desired for the gasoline product. The liquid product is redistilied in the tower $5, the desired gasoline Vconstituents being taken off as a vapor, condensed in a condenser coil 05 and collected in a distillate accumulator 61. The distillate is passed from the agcumulator through a line 68 to a product tank The isopentane fraction collected in accumulator 25 VWill ordinarilyhav'e an A. S. T. M. octane number approximating 90 and this fraction may be passed directly through a line to the product tank to be blended with the products therein, or withdrawn through a branch line 1| for other blending purposes.

The isomerizate produced in the isomerization of the paramnie hydrocarbons, flowing through heating coi1 82`to 'a reaction chamber 03 contain ing the catalytic material. The hydrocarbons are subjected to temperatures within a range of about 600 lit-950 F. under pressures of the order of 10o-300, pounds in the presence of the catalyst. Hydrogen containing gas is drawn from the tank 5land is directed by a pump 84 through a heating coil Whereinthe gas is. heated to 'approximately the temperature of reaction and is delivered thence into the reaction chamber 83. The reaction products pass through a cooler to an accumulator or gas separator 81 from which the hydrogen containing gases may be recycled to the heating coil 85, while any excess of such gases may be returned to the hydrogen tank 5l. The liquid product isr directed by a pump 88 either through branch line 85 to the product tank 09 or through branch line 90 to the stabilizer 63.

In a modiication oi' the invention the extract fraction withdrawn from tank l, instead of being passed to the olen isomerization step .(coil 58 and reaction chamber 50), is directed through a line 9i to the heating coil 82 and reaction cham..

merization of oleiins and a conversion of oleiins' to isoparafiins to obtain a product of high octane number and of increased lead susceptibility. In

vanother modification of the invention the olenline 42, may be withdrawn through a branch line through the branch line 80 to the stabilizer 63. When the isomerizateproduct collected in the' tank Si is to be used for aviation gasoline it sometimes is desirable to treatthis product for the purpose of reducing the oleiin content and increasing Ysusceptibility to tetraethyl lead. In a preferred embodiment of the invention the isomerizat'e is subjected to a finishing treatment capable of effecting a conversion of oleiins into isoparaiiins .and of effecting an increase in lead susceptibility:

By subjecting the isomerizate at elevated temperatures to contact with a solid adsorbentcracking or hydroforming catalyst, such as the synthetic silica-alumina catalysts, adsorbentclays and the like, in the presence of hydrogen-containing gases, olefin hydrocarbons are converted into isoparamns and the reduction in olen content of the product increases the lead susceptibility Y thereof. For thepurpose 0f giving the isomerizate this iinishing treatment the product collected in tank GI may be directed`by the pump 18 and line 0l through a branch line 8| thence through a aromatic fraction withdrawn from tank I6 through line 55 is passed through a branch line 92 directly to the product tank 69 to be used in blending with the products obtained in the 'paraffin isomerization and hydroforming operations. In another modication of the invention the olefin aromatic fraction is treated with a selective solvent for aromatics such as water so as to separate this fraction into an olefin fraction and an aromatic fraction and in this case the olefin fraction is passed to either the olefin isomerizagasoline stock of 400 F. end point obtained from' the thermal cracking of gas oil and having an A. S. T. M. octane number of is treated with sulfur dioxide to produce a raiiinate fractionconstituting 60% of the gasoline stock and having an octane number of 58 and an extract fraction constituting 40% of the gasoline stock and having an octane'number of 85. The raffinate or paraflinic fraction is fractionated to produce the following fractions:

The normal pentane-hexane cut is subjected to catalytic isomerization in contact with aluminum chloride hydrocarbon complex together with added free aluminum chloride to produce a productA yield, based on' the charge to the isomerizatlon unit, of 98% of 80 octane number, or a yield of 10.3% based on the original cracked gasoline charge.` The high boiling fraction is subjected to .hydroforming in the presence of a molybdenaalumina catalyst with recycling of hydrogen to produce a product yield, based on the charge to the hydroforming unit, of 80% of 80 octane number, or a yield of 38.4% based on the cracked gasoline charge. The extract fraction obtained in the solvent treatment containing olen and aromatic hydrocarbons is subjected to olefin isomerization in contact with asynthetic silica-alumina catalyst to produce a product yield, based on the charge to the olefin isomerization unit, of 97% having an octane number of 88, or a yield of 38.8% based on the cracked gasoline charge. In blending the isopentane cut (constituting 1.5%

of the cracked gasoline charge) with the hydroformate and the isomerizates from the olefin and parailin isomerizing operations, a yield of gasoline amounting to89% ofthe original cracked gasoline charging stock is produced ,having an octane number of 84. The yield in the complete process, based on the cracked naphtha charge, may be tabulated as follows:

Per cent Isopentane 1.5 Parafnic isomerizate 10.3 Hydroformate 38.4 Olenic isomerizate 38.8

Total product s 89.0

In a second example of the invention, the process is conducted in accordance with the example just described, except that instead of subjecting the extract fraction, collected in tank Il, to isoforming or isomerization this fraction is subjected directly to a finishing treatment at a temperature of 600 F. under 300 lbs. pressure in contact with a molybdena-alumina catalyst in the presence of hydrogen, or at temperatures of 800 F.-

950 F. under about 100 lbs. pressure in contact with a synthetic silica-alumina cracking catalyst in the presence of hydrogen. In either of these operations a gasoline product of 84 octane number is produced in a quantity amounting to 95%V of the charge to the finishing operation or 38% based on thc original cracked gasoline charge, with the result that in the complete process the gasoline yields are as follows:

Per cent Isopentane 1.5 Paraninic isomerizate 10.3 Hydroformate 38.4 Gasoline from finishing operation 38.0

' Total 88.2

run gasoline or with alkylatefroxn a sulfuric acid alkylation process may readily be leaded to values even above 100 octane. The technical advantage of the process may be seen by comparing it with ordinary reforming. In thermal reforming an octane number of about '75-76 is about the limit.

obtainable ina commercial-operation and to produce a product of that octane value a yield loss of about 15% and even higher is necessary and, moreover, the product is not adapted for aviation stock on account of the relatively high oleiln content.

In a third example of the invention the process is conducted in the same manner as in the first example, except that the extract fraction instead of being given a catalytic treatment is blended directly with the final product and the high boiling. fraction of the paramnic railinate instead of Percent Isopentane n 1.5 Parafdnic isomerizate 10.3 Olefinic aromatic extract 40.0 Thermally reformed gasoline 40.8

Total 92.6

The composite gasoline, product has an octane number of 79.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, but only such limitations should be imposed as are indicated in.the appended claims. t.

I claim:

1. The method of treating cracked naphtha stocks consisting essentially of olefin and aromatic hydrocarbons to produce an improved blending stock adapted as a component of aviation gasoline that comprises contacting the olefin-aromatic naphtha with a solid catalytic material, selected from the group consisting of silica-alumina and adsorptive clays, at a temperature within a range of about 800 F.1000, F. and under a relatively low pressure of under pounds to eiect isomerization of olefin hydrocarbons and contacting resultant products of reaction with a solid catalytic material, selected from the group consisting of silica-alumina and adlsorptive clays, in the vpresence of hydrogen while at a temperature within a range of about 600 F.950 F. and under a pressure of the order of 100-300 pounds to effect conversion of olens to isoparafllns and produce a naphtha product rich in aromatic hydrocarbons and of high lead susceptibility.

2. The method of treating cracked naphtha stocks consisting'essentially of oleiln and aromatic hydrocarbons to produce an improved blending stock adaptedas a component of aviation gasoline that comprlses contacting the olefin-aromatic naplftha with a silica-alumina catalyst at a temperature within a range of about 800'F.1000 F. and under a relatively low pressure of `under 100 pounds to effect isomerizationseneca comprises treating the cracked n aphtha with a selective solvent for olenns and aromatics to separatev 'parafiin hydrocarbons from. an extract fraction rich in olefin and aromatic hydrocarbons, treating said extract fractionwith a solid catalytic material, selected from the group consisting of silica-alumina' and adsorptlve clays, at a temperature within a range of about 800 F.-

1000 F. and under a relatively low pressure of ucts oi. reaction with 'a solid catalytic material, selected from the group consisting of silica-alumina and adsorptive clays, inthe presence of Y hydrogenwhile ata temperature within a range of about 600 F.950 F. and under a pressure of the order of 100-300 pounds to eect conversion of olens to isoparamns and produce a naphtha product rich in aromatic hydrocarbons and of hig'h lead susceptibility.

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