US1887941A - Process of treating hydrocarbons - Google Patents

Description

NOV. 15, 1932. MOORE 1,887,941

PROCESS OF TREATING HYDROCARBONS Fil ed Jan. 15, 1930 mare-o mam DEF/ LE 06/14 7/0 I? FRACUO/VAUM CHE M. 8516167775 FIXED GASES WIPE/i FliACT/O/V POLYMER; CONTACTED WPOI? 6116b OIL R RE/"L UX ME/K5272! COIVDf/KMT/U/V 4ND COOL l/VG F/Ml. HWDMIT 3g)? Patented Nov. 15, 1932 UNITED. STATES PATENT oFFcE a NORMAN H. MOORE, OF WESTFIELD, NEW JERSEY, ASSIGNOR TO THE TEXAS COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE PROCESS OF TREATING HYDROCARBONS Application filed January 15, 1930. Serial No. 421,027.

This invention relates to a process of treating hydrocarbon oils and more particularly to the treatment of relatively light hydrocarbon distillates, such as cracked naphthas and the like, for the production of commercial gasoline of low vapor tension and which is free from undesirable unsaturated constituents.

The invention broadly contemplates a process of treating vapors evolved from the cracking of hydrocarbon oils for the production of gasoline comprisin dephlegmation of the evolved vapors to form an overhead vapor fraction substantially composed of gaseous constituents, rectifying the resulting vapor fraction to produce a stabilized condensate free from fixed gases which is to undergo further treatment with subsequent production of a vapor fraction of desired final and point and ultimately contacting the vapor fraction of final end point with comminuted solid adsorbent catalytic material to effect polymerization of its undesirable unsaturated constituents.

In a preferred embodiment of the invention cracked vapors evolved either from cracking chambers or from flash or evaporative drums to which the cracked material or synthetic charge oil may be conducted from cracking chambers or heating coils, are subjected to dephlemgation or fractionation, preferabl under superatmospheric pressure derived from the cracking system, to produce a naph tha vapor fraction having an end point higher than that desired for the final gasoline-product and a liquid fraction or reflux condensate substantially free from the gasoline constituents which is preferably returned to the cracking coils or reaction drum to undergo further conversion.

The formation of a high end point naphtha vapor fraction during the foregoing fractionation for the subsequent production of an ultimate gasoline having a desired end point which is lower than that of the naphtha fraction is preferable to the direct formation of a vapor fraction having the desired final end point, especially when-the foregoing fractionation or dephlegmation is carried out under substantially the same pressure which from the following discussion which has refcrating in this manner.

The naphtha vapor fraction which has associated with it an appreciable proportion of volatile products resulting from the crackin reaction and which are of thenature of fixed or permanent gases is rectified preferably without prior condensation or cooling and while still under either superatmospheric or reduced superatmospheric pressure derived from the cracking system in order to remove these undesirable fixed gases which, if not re moved from the naphtha, would escape when the vapor is subsequently condensed to form a distillate at reduced or atmospheric pressure carrying with them valuable naphtha or gasoline constituents.

The rectified or stabilized naphtha. may be treated with acids, alkali or other suitable chemical reagents for the partial removal of impurities such as sulfur compounds or certain unsaturated constituents, 4 following which it is re-vaporized and fractionated to form a vapor fraction of desired final end point. 80

The re-fractionated vapor fraction is then subjected to catalytic treatment by contacting with a solid comminuted adsorbent or catalytic material such as for example, fullers earth, charcoal, bone black or the like to bring about polymerization and subsequent removal of its unstable and unsaturated constituents.

The invention may be clearly understood erence to the accompanying drawing illustrating a flow diagram of the preferred method of practicing the invention.

In carrying out the invention the vapors evolved from the conversion or decomposition of hydrocarbon oils by liquid or vapor phase or combined liquid and vapor phase cracking which may be under superatmospheric pressures, as for example 400 pounds or even greatly in excess of this, or, on the 10( other hand,' at pressures considerably reduced from this such as 50 pounds or even more nearly approaching atmospheric, are passed to a dephlegmator or fractionator and subjected to fractionation therein, preferably under pressure derived from the cracking stills or coils, to produce a low boiling or cracked naphtha vapor fraction and a. high boiling liquid fraction substantiallyfree from naphtha or gasoline constituents, which liquid may be either withdrawn from the system or preferably returned to the cracking apparatus for further heating and cracking.

The cracked vapors evolved from the cracking of hydrocarbon oils in conventional cracking coils or reaction chambers or from flash chambers operating in conjunction therewith may comprise in addition to the desirable gasoline fractions, a relatively small proportion of fixed or permanent gases and a relatively large and preponderant proportion of partially cracked material having a boiling point considerably higher than that corresponding to naphtha or gasoline and may, for example, have a distillation end point ranging from 700 F. to 800 F. Thus the evolved vapors may be dephlegmated or fractionated to produce a vapor fraction which has an end point of around 450 F. from which a gasoline product having an end point of 400 F., for example, may later be formed, and a liquid condensate or gas oil fraction substantially free from constituents boiling below the end point of the vapor fraction formed during dephlegmation.

The vapor fraction formed in the above mentioned fractionating step contains the fixed or permanent gases which, when the vapor is condensed to form a gasoline or naphtha distillate, are held in solution in the liquid under the pressures usually employed during fractionation and condensation, imparting a high vapor tension to the liquid, and when the pressure is subsequently reduced these gasesare largely released from the liquid carrying with them valuable gasoline fractions. Even though the fractiona tion and subsequent condensation may be carried out at pressures approaching atmospheric and the resulting distillate contains a minimum of these fixed gasesthere will still be an appreciable loss due to the very high vapor pressure of these gases and their carrying effect as they escape from the distillate and therefore it is desirable to rectify the naphtha vapor, preferably prior to condensation or further treatment, to effectively remove these gases in order to prevent loss of valuabl gasoline constituents during subsequent treatment as well as during later transportation and storage.

While the vapor fraction may be condensed and cooled immediately following its removal from the deph'legmator to form a naphtha distillate which may be charged to the rectifying apparatus or'may be given a preliminary chemical treatment for the removal of impurities prior to rectification, such as scrubbing with an alkali to remove hydrogen sulfide, it is preferable to introduce the vapor fraction to the rectifier or stabilizer without previous condensation or cooling in order to take advantage of the sensible heat contained in the vapor which may be liberated within the rectifier to effect the necessary re-vaporization during rectification to remove the fixed gases and thereby minimize, and perhaps entirely eliminate, the quantity of heat to be added from external sources.

Accordingly the vapor fraction formed during the primary fractionation or dephlegmation is subjected to further fractionation or rectification to produce a rectified or stabilized condensate of desired vapor tension. the fixed or permanent gases which were previously dissolved therein being removed in a substantially dry state or containing such a small proportion of normally liquid constituents that it would not be practicable to further treat the gases for the extraction of gasoline constituents prior to their disposalas fuel or in any other suitable manner.

The rectification step is preferably carried out under superatmospheric pressure originally derived from the cracking system which may be substantially the same pressure prevailing in the cracking system or in the dephlegmator, although it is contemplated that pressures reduced below that prevailing in the cracking vessel or in the dephlegmator may also be employed.

Since the cracking reaction is usually carried out under autogenous pressures in excess of atmospheric the subsequent treating steps including fractionation, condensation and rectification are preferably carried out under pressure originally derived from the cracking system, employing any desirable gradation of pressures throughout these consecutive treating steps and thereby avoiding the necessity of providing means for positive displacement therethrough of the material undergoing treatment.

While subsequent treating steps immediatelv following those just mentioned may be sion may be chemically treated with acid,

caustic, or other suitable chemical reagent in order to remove a portion of the impurities contained thereinsuch as sulfur compounds or some of the undesirable unsaturated con- Ill stituents prior to the later treatment with catalytic adsorbent material.

The chemical treatment may beof the nature of a washing with caustic, soda ash or other suitable reagent to remove certain undesirable sulfur compounds such as mercaptans and hydrogen sulfide. On the other hand the condensate may be subjected to acid treatment with either weak or strong acid, as may be desired, to effect partial removal of certain unsaturated constituents or other unstable impurities the remainder of which are removed in the later treatment with catalytic material which will be fully discussed shortly. While the catalytic material may remove all of these undesired constituents without a prior acid treatment it is preferable to subject the condensate to such prior acid treatment in order to insure an ultimate product-of superior quality and chemical stability as well as to increase the life and efli ciency of a given batch of catalytic material.

Upon removal of the acid sludge formed during the treatment with acid the condensate may then be sweetened with alkali, doctor solution or other suitable reagent.

The chemically'treated stabilized oil which is in liquid form is now re-vaporized either prior to or in conjunction with the final fractionation to which it is subjected in order to produce therefrom a chemically treated rectified vapor fraction having a desired final end point which, as previously explained, is lower than that of the original vapor fraction formed during the primary dephlegmating or fractionating step and a liquid or gas oil fraction free from the desired gasoline constituents which may be withdrawn to storage or returned to the cracking system for further treatment. a

The stabilized or rectified gasoline fraction while in vapor form is then passed through a bed or body of comminuted solid absorbent catalytic material such as fullers earth or the like where, due to the close physical contact effected between the vapor and the surface of the solid particles during passage therethrough, a catalytic reaction occurs whereby polymerization of the undesirable unsaturated and unstable constituents of the vapor which were not removed during the chemical treatment is brought about. .In this catalytic reaction the unsaturated constituents are polymerized to form liquid compounds or polymers which have a higher boiling point than the valuable gasoline components with which they we cassociated prior to polymerization. Thus the polymers are separated from the-treated vapors either durin or immediately following the contacting 0 the vapors with the catalyst by liquefaction or fractional condensation and the contacted vapor, free from polymerous mate rial, may thenbe passed to a final condenser following which it may be subjected to a final sweetening treatment with chemicals such as alkali or doctor solution to produce a final sweetened gasoline.

lVhile the production of a high end point naphtha vapor fraction during the primary dephlegmation of the cracked vapors evolved from the cracking system has been discussed it may be desirable in certain cases to fractionate these cracked vapors to produce directly a vapor fraction having the same end point as that desired for the final product as, for example, when cracking certain stocks which may produce gasoline fractions of superior quality and which do not require acid treatment or rigorous catalytic treatment.

Under these conditions the fractionation step immediately prior to catalytic treatment may be omitted, it being only necessary to revaporize the rectified condensate preparatory to its passage through the catalytic mass. However, when a final end point fraction such as the above is treated with acid, especially strong acid, the end point'may be raised sufficiently, due to the presence of high boiling polymer compounds formed as a result of the polymerization of unsaturated constituents by the acid, to necessitate final fractionation prior to contacting with the catalyst in order to remove these undesirable high boiling compounds.

Thus by means of this invention the cracked vapors evolved in conventional cracking apparatus may be treated to produce a final gasoline of desired distillation range free from fixed gases or. so-called wild constituents and which is also free from undesirable, un-

stable and unsaturated constituents which if not removed produce color-forming compounds and tend to form gummy deposits.

While the removal of the fixed or permanent gases during rectification of the cracked p vapor has been discussed, the invention further contemplates the possibility of removing in addition low boiling fractions relatively heavier than the fixed gases in order to produce a rectified condensate having a high initial boiling point, the quantity of such light constituents removed depending upon the desired distillation range of the final product.

Furthermore while substantially atmospheric pressure is usually employed during re-vaporization, final fractionation and subsequent contacting with catalytic material, it is contemplated that either sub-atmospheric or super-atmospheric pressures may be employed during these steps.

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

- I claim: 1. In the method of'treating hydrocarbon vapors evolved during cracking under superatmospheric pressure, the steps which comprise subjecting the evolved vapors to dephlegmation under superatmospheric pressure to form a reflux condensate and an overhead vapor fraction'huving an end point higher than that desired for the final product, condensing the vapor fraction to form a dis tillate, subjecting the distillate to preliminary chemical treatment for partial removal of impurities, subjecting the treated distillate to rectification under reduced superatmospheric pressure to form a condensate of desired vapor tension, chemically treating the rectified condensate for further removal of impurities, re-vaporizing the chemically treated condensate, fractionating the revaporized condensate to form a vapor of desired final end point and a liquid free from constituentsdesiredfor the final product, contacting said vapor with solid adsorbent catalytic material to polymerize its undesirable unsaturated Constituents and separating and condensing the remaining vapors to form a treated final product.

2. In the method of treating hydrocarbon vapors evolved during cracking, the steps which comprise subjecting the evolved vapors to dephlegmation under superatmospheric pressure to form a reflux condensate and an overhead vapor fraction having an end point higher than that desired for the final product, condensing the vapor fraction to form a distillate, subjecting the'distillate to preliminary chemical treatment for partial removal of impurities subjecting the partially treated distillate to rectification to remove fixed gases and form a condensate of desired vapor tension, chemically treating the rectified condensate for the partial removal of impurities, revaporizing the partially refined condensate, fractionating the re-vaporized condensate to form a vapor of desired final end point and a liquid free from constituents desired for the final product, contacting said vapor with solid adsorbent catalytic material to polymerize its undesirable unsaturated constituents and separating and condensing the remaining vapors to form a treated final product.

3. In the method of treating hydrocarbon vapors evolved during cracking, the steps which comprise subjecting the evolved vapors to dephlegmation to form a reflux condensate and an overhead vapor fraction having an end point higher than that desired for the final product, condensing the vapor fraction to form a distillate, subjecting the distillate to rectification to remove fired gases and form a condensate of desired vapor tension, acid treating the rectified condensate for the partial removal of impurities, re-vaporizing the partially refined condensate, fractionatingthe re-vaporized condensate to form a vapor of desired final end point and a liquid free from constituents desired for the final prod- 5 net, contacting said vapor with solid adsorbent catalytic material to polymerize its undesirable unsaturated constituents and separating and condensing the remaining vapors to form a treated final product.

4. In the method of treating hydrocarbon vapors evolved during cracking under superatmospheric pressure, the steps which comprise subjecting the evolved vapors to fractionation under superatmospheric pressure to form a reflux condensate and an overhead vapor fraction of desired final end point, condensing the vapor fraction to form a distillate, subjecting the distillate to preliminary chemical treatment for partial removal of impurities, rectifying the distillate under reduced superatmospheric pressure to form a condensate of desired vapor tension, chemically treating the rectified condensate for further removal of impurities, re-vaporizing the partially refined condensate, contacting the resultant vapor with solid adsorbent catalytic material to polymerize its undesirable unsaturated constituents and separating and condensing the remaining vapors to form a treated final product.

5. In the method of treating hydrocarbon vapors evolved durin cracking, the steps which comprise subjecting the evolved vapors to fractionation to form a reflux condensate and an overhead vapor fraction of desired final end point, condensing the vapor fraction to form a distillate, subjecting the distillate t6 preliminary chemical treatment for partial removal of impurities, rectifying the partially treated distillate to remove fixed gases and form a condensate of desired vapor tension, chemically treating the rectified condensate for the partial removal of impurities, re-vaporizing the partially refined condensate, contacting the resultant vapor with solid adsorbent catalytic material to polymerize its undesirable unsaturated constituents and separating and condensing the remaining vapors to form a treated final product.

6. In the method of treating hydrocarbon vapors evolved during cracking, the steps which comprise subjecting the evolved vapors to fractionation to form a reflux condensate and an overhead vapor fraction of desired final end point, condensing the vapor fraction to form a distillate, rectifying .thedistillate to remove fixed gases and form a condensate of desired vapor tension, acid treating the rectified condensate for the partial removal of impurities, re-vaporizing the partially refined condensate contacting the resultant vapor with solid adsorbent catalytic material to polymerize its undesirable unsaturated .constituents and separating and condensing the remaining vapors to form :1 treated final product.

In witness whereof I have hereunto set my hand this 6th day of January, 1930.

.NORMAN H. MOORE.

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