US2343192A - Conversion of hydrocarbon oils - Google Patents

Description

Feb. 29, 1944. W, E KUHN C ONVERSIONOF HYDROCARBON OILS Filed Feb. 25, 1942 ODM ,y y@ W WAYNE E.KUHN

uabmu `HIS A T T ORNE Y Patented Feb. 29, 1944 CONVERSION OF HYDROCARBON OILS Wayne Edward Kuhn, Scarsdale, N. Y., assignor to The Texas Company, New York, N. Y., a corporation cf Delaware Application February 25, 1942, Serial No. 432,193

2 Claims.

This invention relates to the treatment of crude petroleum or a Wide boiling fraction of petroleum for the production of gasoline of high antiknock quality and of a volatility adapted for a high grade motor fuel. The invention contemplates a combination thermal cracking and reforming, catalytic cracking and catalytic isomerization process in. which various fractions are processed in a manner adapted to produce a composite gasoline having both high antiknock quality and a distillation range adapted for a highgrade motor fuel. v

In accordance with the invention crude oil is fractionated to obtain fractions comprising gas oil, heavy naphtha and light naphtha, the gas oil is subjected to catalytic cracking, the heavy naphtha is subjected to thermal reforming, and the light naphtha, or normal parainic hydrocarbon fractions thereof, are subjected to catalytic isomerization, and gasoline constituents produced inthe catalytic cracking, thermal reforming and catalyticisomerization processes are blendedl to produce gasoline of desired volatility and antiknock quality adapted for use in high compression motors.

' In accordance with the invention the light gasoline constituents may be fractionated to separate fractions comprising normal paraffin hydrocarbons, such as pentane, hexane and heptane,

' from isomers or other hydrocarbons of relatively high -antiknock quality. The normal paraffin hydrocarbon fractions are subjected to catalytic isomerization and the isomerizate is blended with the isomers or other fractions segregated from the straight run gasoline and with gasoline products obtained in the thermal reforming of the heavy naphtha and in the catalytic cracking `of the gas oil.

The invention also contemplates the thermal cracking of higher boiling products produced in the catalytic cracking operation by passing such higher boiling products through a heating zone wherein they are subjected to cracking temperature and the combining of the heated products with crude residuum to effect cracking of the residual constitutents of the crude oil so that the entire crude may be utilized in the production of high antiknock gasoline.

' For the purpose of more fully disclosing the invention reference is now had tothe drawing which is a ow diagram illustrating a particular embodiment of the invention.

Charging stock such as crude petroleum is diwherein the oil is raised to a desired distilling temperature. The heated oil is separated into vapors and residue in a tower l2 from which residue is Withdrawn through a line I3. `The separated vapors are subjected to fractionation to obtain a gas oil fraction collected in tray Hl and a heavy naphtha fraction collected in tray l5. Uncondensed vapors comprising the lighter components of gasoline pass to a condenser I 5 thence to a distillate drum or gas separator il. The gasoline distillate collecting in receiving drum l1 is Withdrawn through a line I8 for passage to the isomerization zone hereinafter described, or is withdrawn through a branch line i9 and directed by a pump to fractionating apparatus adapted for 'effecting a further fractionation of the gasoline constituents so as to segregate components thereof that are best adapted for isomerization.

In the particular embodiment of the invention illustrated the gasoline fractionating apparatus includes fractionating towers 2 I, 22. and 23. Each of these towers is provided with suitable elements for vapor-liquid contact and with suitable heating and reboiling means and cooling or refluxing means to accomplish close fractionation. Uncondensed vapors from tower 2! pass to a condenser 2Ia thence to a distillate receiver or gas separator 2lb, uncondensed vapors from tower 2'2 pass to a condenser 22a thence to al distillate 4p 25 to the tower 2'2 wherein the constituents are subjected to conditions of fractionation so as to take overhead and collect as a distillate in receiving drum 22h a fraction comprising pentane. which fraction is withdrawn through a linel 26. Liquid is withdrawn from tower 22 through a line 21 and is directed by a pump 23 to the tower 23 wherein fractionating conditions are maintained so as to take overhead and collect as a distillate in receiver 23b a fraction comprising hexane, which fraction is withdrawn through a line 29.

The lines I8, 25 and 29 communicate with a manifold line 3U so that either the entire light gasoline fraction collected .in receiver l'l, the

rected by a pump I through a heating coilll pentane fraction collected in receiver 22h, or the hexane fraction collected in receiver 23h, or any desired mixture of the pentane and hexane fractions, may be conducted to the isomerization unit hereinafter described. The isopentane fraction is withdrawn from the receiving drum 2Ib through a line 3I and the fraction heavier than hexane is withdrawn from the fractionator 23 through a line 32. The lines 3l and 32 communicate with a manifold line 33 for the purpose of blending either or both of these fractions with other gasoline products of conversion as is hereinafter described. In case it is not desired to blend the fraction heavier than hexane, withdrawn through line 32, with the final gasoline product, this fraction maybe returned to the tower I 2 or sent to the reforming coil 15.

A pump 34' withdraws gasoline constituents from the manifold line and passes them to a heating coil 35 wherein they are heated to a desired reaction temperature for reaction in the presence: of a suitable isomerization catalyst, such as aluminum chloride, which may be conveniently introduced by means of a pump 36 through line 31 as an aluminum chloride hydrocarbon complex. The mixture of hydrocarbons and catalyst is passed through a reaction coil 38 thence to a separator 40 wherein the catalyst may be separated from the treated hydrocarbons. In separating the hydrocarbons from the catalyst distillation may be employed, the hydrocarbon vapors passing to a condenser 4I thence to a receiving drum 42 in which the isomerized product is collected. If desired, the products collected in drum 42 may be fractionated to separate out unconverted normal paraffin hydrocarbons, particularly hexane, which may be recycled to the isomerization unit.

The gas oil fraction distilled from the crude oil and collected as a reflux condensate in tray I4 of tower I2 is withdrawn through a line 43 and directed by a pump 44 through a heating coil 45 disposed in a furnace 46 wherein the gas oil is vaporized and brought to a suitable reaction temperature for catalytic cracking. The heated oil is passed to a catalyst chamber 41 containing a suitable cracking catalyst. The catalyst consists advantageously of a synthetic silica-alumina type of catalyst. Various acid-treated and metalsubstituted clays such as the Super-Filtrols and acid-treated and metal substituted natural. or articial zeolites, such as the artificial zeolite known as Doucil may be employed. Various metals such as uranium, molybdenum, manganese, lead, zinc, zirconium, nickel and the like may be substituted in the clays or zeolites. Likewise, the combination of certain acid-treated active clays of the character of Filtrol, together with added proportions of alumina or silica or both maybe employed. Alumina alone may be used under certain conditions. The synthetic alumina catalysts can be improved by the addition of other constituents such as zirconium oxide or molybdenum oxide. The catalyst may either be disposed as a stationary bed or fixed mass through which 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.

The products of the catalytic cracking pass to a separator and fractionator 43 wherein products higher boiling than gasoline may be separated out. If desired, all of the products higher boiling than gasoline may be collected in a residue separated out from the catalytically cracked products and withdrawn through a line 49. sometimes desirablahowever, to separate in the fractionator 48 a residue from vapors including gasoline as well as higher boiling constituents and to subject the separated vapors to fraction ation so as to separate constituents higher boiling than gasoline which are collected as a reux condensate in a tray 50 from which the reflux condensate may be withdrawn through a line 5I. Overhead vapors pass from the. tower 48 to a condenser 52 thence to'a receiving drum 53 in which the catalytically cracked gasoline distillate isV collected.

The lines 49 and 5I communicate with a manifold line 54 by which higher boiling products of the catalytic cracking operation are withdrawn by a pump 55 which directs these I products through a line 56 to a heating coil 51 disposed in a furnace 58 wherein the oil is subjected to a temperature adapted for thermal cracking. The heated products from the cracking coil 51 pass through a transfer line 58 to a cracking Zone,y such as a reaction chamber 6U. Products from the reaction chamber are delivered through a transf fer line 6I to a separati-ng, chamber 52 wherein vapors separater from residue. Residue, is withdrawn through a line. 6 3 and separated vapors pass tc.. a primary fractionating tower 54.

The crude. residuum withdrawn through line I3 from they crudeI oil fractionator l2 is directed` v by a pump 6.5. through aline a to the primary It is fractionator 64 to dephlegmate the cracked vapors therein. The resulting mixture of reflux condensate and unvaporized residue is withdrawn from the tower 64 by a pump 66a and. directed through a line 66 to the transfer line. 59 or to the reaction chamber G for cracking therein in contact with the. hot stream of products from the cracking coil 51.

Uncondensed vapors pass from the primary fractionator E4 to a secondary fractionator` 61 wherein the vapors are fractionated to separate gasoline constituents from higher boiling reflux condensate. The higher boiling refluxA condensate is withdrawn by a pump 68 and directed through a line 69 to the heating coil 51 so that the super-c1ean condensate from the tower 61 maybe combined with the higher boiling products of the catalytic cracking and subjected to thermal cracking in the cracking coil `51 as well as in the reaction chamber 60. Uncondensed vapors pass from the tower E1 to a condenser 1Q thence to a receiving drum or gas separator 'i2 wherein the thermally cracked gasoline distillate is collected.

In a modication of the invention a portion or all of the reflux condensate from tower B1 may be directed through a branch line 69a to the heater 45 for catalytic cracking tgoether with the straight run gas oil. Since the condensate collected in tower 61 is the product of a thermal cracking operation it may with advantage be subjected to catalytic cracking.

The naphtha fraction for reforming is withdrawn from the tray I5 of tower I2 through a line 13 and is directed by a pump 'I4 to a heating coil 15 disposed in the furnace 16 wherein the gasoline constituents are subjected to cracking temperatures adequate to effect thermal reformation into constituents of increased antiknock quality. The hot products from the reforming coil 15 pass through a transfer line 11 which is shown with a branch line 18 extending to the transfer line 59 or reaction chamber 6l! and another branch line 19 extending to the separating drum 62.

From the preceding description it will be seen that the combination process described herein serves to produce the following products, viz.:

A. Thermally cracked gasoline collected in drum 12 comprising gasoline constituents produced by the thermal cracking of the residual constituents from the crude oil and of the higher boiling products from the catalytic cracking operation as well as by the reforming of the straight run heavy naphtha;

B. Catalytically cracked gasoline collected in receiving drum 53;

` C. Isomerizate collected in drum 42 produced by the catalytic isomerization of the lighter fractions of gasoline or of selected normal parain fractions thereof.

D. segregated straight run gasoline fractions collected in line 33 comprising essentially isomers of normal paraffin hydrocarbons.

In accordance with the invention these fractions are lblended together to produce a final gasoline product of high antiknock quality and good volatility. A rectifying tower 80 is provided for rectifying or stabilizing such of these gasoline products as may require stabilization. Thecatalytically cracked distillate is withdrawn from the receiver 53 and directed by a pump 8l through a line 82 to the stabilizer 80. The mixture of thermally cracked and reformed gasoline is withdrawn from receiver 12 and directed by a pump 83 through a line 84 to the stabilizer 80 and isomerizate from drum 42 is directed by pump 35 and line 86 to the stabilizer. The stabilized gasoline product is withdrawn through a line 81. The fractions collecting in line 33 will normally' require no stabilization and these fractions may A be directed by a pump 88 through a line 89 and blended with the stabilized product from the stabilizer.

In practicing the invention the crude oil is fractionated to obtain a gas oil cut as collected in tray I4, preferably having a boiling point of 450-500" F. and an end point of about G50-'750 F., a heavy naphtha fraction as collected in tray I having an initial boiling point of about 200- 225 F. and an end point of LLOU-500 F., and a light naphtha fraction as collected in drum I1 having an end point of about 20G-225 F. This light naphtha fraction is fractionated in tower 2| so as to take overhead isopentane together with any lighter hydrocarbons that may be present.

The bottoms from tower 2l are refractionated in tower 22 so as to take overhead a pentane fraction. The bottoms from tower 22 are refractionated in tower 23 so as to take overhead a hexane fraction.

The pentane and hexane fractions are directed to the isomerizaticn unit while the isopentane fraction and the fraction heavier othan hexane which is withdrawn from the bottom of tower 23 are utilized for blending with the final gasoline product of the process. While the entire light gasoline fraction collected in drum I1 may be subjected to catalytic isomerization it is found that best results are obtained by isolating fractions containing concentrations of the normal parafns, such as pentane and hexane. and utilizing these fractions as the charging stock to the isomerization unit. The presence of aromatics in the charge to the isomerization unit may be harmful since the aromatics will react with certain of the catalysts used in the isomerization reaction and consequently it is som ctimes desirable to treat the charge to the isomerization unit with a solvent adapted for removing the aromatics. Various catalysts such as aluminum chloride. boron :ill

chloride and ferric chloride may be employed in the isomerization operation. Best results are obtained with aluminum chloride which may be introduced in the form of an aluminum chloride hydrocarbon complex. It is preferably to employ this catalyst in the presence of added hydrogen chloride and hydrogen. Temperatures of about 20C-400 F. under a hydrogen pressure of 800- 4000 lbs. may be employed. The isomerized product is of the order of 80 octane by the Cooperative fuel research motor method.

In isomerizing the entire light naphtha fraction obtained from the crude oil, fractions having, for example, initial boiling points of 90-110 F. and end points of 210-230" F. with an octane number of about C. F. R. M. may be raised to about 15 C. F. R. M. and similar straight run fractions of higher octane numbers raised to higher octane numbers. When fractionating the light naphtha to concentrate normal paran hydrocarbons for the isomerization treatment even better results are obtained. Thus a pentane-hexane fraction free from isopentane and having an octane number. of 68 C. F. R. M. may be raised to about C. F. R. M. The straight-run isopentane fraction will have an octane number of 89-91 C. F. R. M.

The gas oil may be heated in the coil 45 to temperatures of the order of 900 F.1000 F. and the vaporized and heated gas oil is brought into contact with the catalytic material in chamber 41. The gasoline product as collected in drum 53 approximates 80 octane by the Cooperative fuel motor research method.

The heavy naphtha may be subjected to temperatures of the order of 900 F.1000 F. in the heating coil 'l5 under pressures of 20D-800 lbs. and subjected to thermal reformation therein. The higher boiling product from the catalytic cracking operation, either the entire product or a gas oil product collected as a reflux condensate in tray 50, is passed to the heating coil 51 wherein it may be subjected to thermal cracking at temperatures of the order of 900 F.-1000 F. The

' mixture of crude residuum and reflux condensate Withdrawn from tower 64 is combined with the hot products from coil 51 and subjected to thermal cracking in the reaction chamber 60 at temperatures above 850 F., preferably at temperatures of about 890 F.930 F. so that a high rate of cracking conducive to a conversion into high antiknock gasoline constituents may be carried on therein. When cycling the condensate from the tower B1 to the cracking coil 51 it is generally preferable to introduce the stream from the reformer coil 15 into the separating chamber B2. In the latter chamber separation into vapors is effected and either a liquid fuel oil is withdrawn through line 63 or the residue is reduced to coke. The reflux condensate Withdrawn from tower 51 may in an alternative method of operation be directed to the heating coil 45 for catalytic cracking together with the straight run gas oil and when this operation is employed the effluent from the reforming coil 15 may be directed through the branch line 18 into reaction chamber B0. 'Ihe gasoline product resulting from the several thermal cracking operations as collected in drum 12 has an octane number of about 75 by the Cooperative fuel motor research method.

Although a preferred embodiment of the invention has been described herein, it will be understood that various changes and modifications may be made therein, while securing to a greater or less extent some or all of the benefits of the invention, without departing from thasprt and.

i scope thereof- Iclaim: 1. In the treatment of crude petroleum for` the production ofgasoline of high anti-knock f quality, the process that comprises subjecting the crude oil to fractional distillation to obtain a crude residuum, a gas oil fraction, a heavy naphtha fraction and a light naphtha fraction,` subjecting the light naphtha fraction to further fractionation to separate isopentane, pentane and hexane fractions from the other components of thelight naphtha fractions, subjecting the pentane and hexane fractions to catalytic isomerization to effect conversion into gasoline constituents of increased anti-knock quality, subjecting the heavy naphtha fraction to therma1 reforming tol effect conversion into gasoline constituents of increased volatility and anti-knock quality, subjecting the gas oilfraction to catalytic cracking to effect conversion into gasoline constituents, fractionating ther resultant products of said catalytic. cracking to separate the gasoline constituents from higher boiling products, passing the latter higher boiling products through. a heat-y ing coil wherein' these products are, heated at a cracking temperature and subjected to thermal cracking to effect conversion into gasoline constituents, combining theA resultant products of said thermal cracking with the aforesaid crude residuum and subjecting the mixture to thermal cracking in a reaction zone to eiect a further` conversion into gasoline constituents, separating the cracked products of the latter4 thermal cracking into vapors and residue frationaiiag the eeparated, vapors to, Sararaiehiaher hailing., reux `tand@anif; frein. gesellige @chtiments directies said reflux condensate tosaid, heating c thermal cracking with higherY boilingy catalytiteamone-2. gasaliaeof desired Volatility and, having' a' high aatilknack quality! 2.1i; thle treatment of` crudeV petroleum for the production of gasoline of high anti-knock quality, the process that comprises subjecting. the crude oil to fractional distillation toV obtain a crude. residuum, a gas oil fraction, a heavyv naphtha fraction and a light naphtha fraction, subjecting the light naphtha fraction to further. fractionation to separate isopentane, pentane and hexane fractions from the other components of the light naphtha fraction, subjecting the pentane and hexane fractions to catalytic isomerization to effect conversion into gasoline constituents of increased anti-knock quality, subjecting the heavy naphtha fraction to thermal reforming to effect conversion into gasoline constituents of increased vclatilit;7 and anti-knock quality, suhjecting the gas oil fraction to catalytic cracking in a catalytic cracking zone to effect conversion into gasoline' constituents, fractionating the resultant products of said catalytic cracking to separate the gasoline constituents from higher boiling products, passing the latter higher boiling products through a heating coil wherein these products are heated at a cracking temperature and subjected to thermal cracking to eifect conversion into gasoline constituents, combining the resultant products of said thermal cracking with the aforesaid crude residuum and subjecting the mixture to thermal cracking in a reaction zone to effect a further conversion into gasoline constituents, separating the cracked products of the latter thermal cracking into vapors and residue, fractionating the separated vapors to separate higher boiling reux condensate from gasoline constituents, directing said reiiux condensate to said catalytic cracking zone and combining re sultant gasoline constituents of the said thermal cracking and reforming and catalytic cracking operations With the aforesaid isopentane fraction and said other components of the light naphtha fraction to produce a gasoline of desiredvolatility and having a high anti-knock quality.

WAYNE EDWARD KUHN.

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