US2426903A - Conversion of hydrocarbon oils - Google Patents

Description

Sept. 2, 1947. w. J. SWEENEY 2,426,903

CONVERSION OF HYDROCARBON OILS Filed Nov. 5.1944 2 Sheets-Sheet i r u (1.5 ourfiuhu o e b n m M m w 5 a u H e n m M J a & m N." n V. Au In 7 an 8 il ms l m Q A III! I W (mm \rd( 2. & Mmw. Wu 8. QJH u N hm 02:65. W W 0% mu 8 W 8 PKEL FE NOEMOFQQ Y. Pr av u Q dorgmzuom mp.

A om Sept. 2, 1947. I w. J. SWEENEY 2,426,903

CONVERSION OF HYDRO'CARBON OILS Filed Nov. 5, 1944 I v 2 Sheets-Sheet 2 William: J gw'eeneq ES-w enflcm b QbbQencq Patented Sept. 2, 1947 UNITED STAT William J. Sweeney, s

ration of Delaware 2,426,903 I CONVERSION OF HYDROCARBON ummit, N. 1., assignor to Standard Oil Developm ent Company. a corpo- Application November 3, 1944, Serial No. 561,673

3 Claims.

This, invention relates to the conversion of hydrocarbon oils and pertains more particularly to the production of aviation gasoline from higher boiling oil.

It is now commonly known that gasolines produced by conventional catalytic cracking processes contain relatively high concentrations. of' olefinic and other unsaturated constituents which are undesirable in aviation gasoline. It is likewise known that the olefinic constituents are more highly concentrated in the lower boiling fraction of the gasoline produced from the catalytic cracking operation. I

Various methods have heretofore been proposed for removing the olefinic constituents from the gasoline obtained from catalytic cracking operations. These methods may include, for example, acid treatment, solvent extraction, polymerization, alkylation, recracking and hydrogenation.

It has likewise been found that while the higher boiling fraction of catalytic gasoline contains a relatively high concentration of aromatics and a relatively low concentration of oleflnic constituents, as compared with the lower boiling fraction, the higher boiling fraction also contains constituents which tend to impair and degrade the quality of aviation gasoline.

In view of this, it has been proposed to subject the heavier fraction of the catalytic naphtha to further catalytic treatment in the presence of the same general type of catalyst employed during the catalytic cracking and under the same general operating conditions. This retreating of the gasoline efiects a material improvement in the quality of the gasoline product.

According to one type of procedure heretofore proposed, the naphtha formed from a catalytic cracking operation is segregated into a light naphtha fraction, such as a fraction boiling below 200 and a heavier naphtha fraction boiling between 200 F. and the end point of the gasoline. The light naphtha fraction so separated is then hydrogenated to saturate the oleflnic constituents and the heavier naphtha is subjected to further cracking treatment, preferably at lower temperaturesthan are employed in the primary cracking operation. The retreated heavy naphtha and the hydrogenated light naphtha may then be blended into the final gasoline prod not. together with the addition of an alkylate or other addition agent, for producing the final market aviation gasoline.

One of the principal objects of the present invention is to provide a process of the general'type above outlined which will produce an improved yield of higher quality aviation gasoline.

Other more spec invention will be apparent hereinafter.

In accordance with the broader phases of the present invention, a higher boiling oil, such as a gas oil or reduced crude, is initially subjected to a catalytic cracking operation. The cracked vapors are thereaf light naphtha fraction and a heavier nahptha fraction. The heavier naphtha fraction so separated is then subjected to a recrackingtreatment in the presence of a catalyst and the recracked or retreated product is separately fractionated to separate a light. naptha and a heavy naphtha. The heavy naphtha o separated is withdrawn as a finalproduct of the proces formed during the retreating operation is then intermixed or combined with the light naphtha formed during the primary cracking process.

This combined stream is thereafter subjected to further treatment for removal of the oleiinic constituents therefromand then blended with the retreated heavy naphtha.

According to a further mo vention, the light naphtha formed during the initial catalytic cracking process and during the aftertreating of the heavy naphtha fraction obtained therefrom is furtherseparated into a fraction consisting principally of C5 hydrocarbons and a fraction consisting principally of Ce hydrocarbons. The C5 hydrocarbon fraction is thereafter separately treated, as hereinafter described, and the Co fraction is subjected to hydrogenation, as previously described.

In accordance with another more sp of the present invention, the cracked vapors from the initial and aftertreating operations are fractionated to segregate a light naphtha fraction boiling up to about F. and a second naphtha fraction boiling between about 150 F. and the final end point of the naphtha.

It has been found, for example, that a substantial improvement in the character and yield of the products may be realized by careful selection of the cut point between the light and heavy naphthas formed during the cracking treatment. .By cutting the fractions at about 150 F.

molecule will appear mainly in the heavy naphtha and therefore be subj ected to the 'aftertreating operations previously described, whereas the light I iiic and detailed objects of the ter. fractionated to segregate a s. The light naphtha dification of the inthe hydrocarbons having 7 carbon atoms or more perthe hydrocarbon fraction consisting principally of hydrocarbons containing 7 carbon atoms per molecule is more advantageously treated by the recracking or retreating operation than by the hydrogenation treatment given to the lower boiling fraction. A

With the above general nature and objects in view, the invention will be best understood by the more detailed description hereinafter in which reference will be made to the accompanying drawings forming a part of the disclosure and illustrating in a diagrammatic manner an apparatus suitable for carrying the invention into effect. In'the drawings Fig. 1 is a diagrammatic illustration of the cat-- alytic' cracking and retreating steps in the process, together with the initial fractionation of the products, and

Fig. 1A is an extension of Fig. 1 illustrating the hydrogenation and allgvlation steps. together with a more complete separating and fractionating equipment.

Referring to the drawing, reference character I. designates a charge line into which a higher boiling oil tobe processed is introduced into the equipment. This oil may comprise any higher boiling natural or synthetic petroleum stock which is to be converted into lower boiling motor fuel. For example, the oil may be a clean condensate stock of gas oil boiling range, or it may comprise a crude or reduced crude. The oil passing through line I. is intermixed with a cracking catalyst which is continuously discharged therein throuah a vertical conduit II. This catalyst may be any of the commonly known cracking catalysts, such as silica-alumina, silicamagnesia, alumina-boria, silica-zirconia, or mixtures thereof.

For illustrative purposes, the cracking operation is shown in the form of a fluid catalyst cracking equipment in which the catalyst in line- 1y divided form while in fluid state is caused to circulate continuously through a cracking chamber and a regenerating chamber. In this operation the loss in pressure on the catalyst resulting from the circulation through the chambers is restored by .means of a standpipe in which the necessary pressure is generated to effect the circulation.

Furthermore, in this type of operation the oil vapors and regenerating gas are passed upwardl through the cracking and regenerating zones, respectively, at a velocity controlled to maintain a dense, turbulent layer of catalytic material in the bottom portion of the chamber superimposed byadilutemixtureofgasesandcatalystinthe upper portion.

Theoilpassingthroughlinellmaybepreheated, or the necessary amoimt of heat for the cracking operation may be obtained from the hot regenerated catalyst being introduced therein through conduit II. The mixture of hot regenerated catalyst and oil vapors formed in the line ll continues through line ll into the bottom section of a cracking chamber 12 throimh a distributing cone It. The oil vapors pass throughthecrackingchamberll ataveloclty controlled to maintain a dense, turbulent layer of catalytic material, as indicated on the drawing 'andaspreviouslydescrlbed..'1'he vapomusreactionproductsareremovedfromtheupperportionofthecrackingchamberflthroughacycloneseparator llwhichmayhemountcdmthe upperpartotthereactionchamber. 'ihecracked vaporswithdrawnfromthetopoftbeaacking'tltumedtothe 4 chamber pass through line It to a primary fractionating tower I! in which constituents boiling above the desired motor fuel fraction are condensed. The fractionating tower may be provided with one or more trap-out trays for segregating the diifere'nt fractions of said higher boiling constituents.

The initial condensate formed in the bottom section of the primary fractionating tower I8 is withdrawn through line II. This fraction may contain a small amount of entrained catalyst carried overhead from the reaction chamber I! through'line l5. This fraction may be treated in equipment (not shown) for removing the catalyst therefrom, or the fraction may be recirculated from line l'l through pump l8 and line I! which merges with the charge line II. An intermediate gas oil out may be collected in a trapout tray 2| of the fractionating tower I6 and may be withdrawn therefrom through line 22.

Vapors remaining uncondensed in the fractionating tower I6 and consisting of normally gaseous constituents together with the desired motor fuel fraction are removed overhead through line 23 to a condenser 24 in which the desired distillate is condensed. The products from the condenser may then pass to a product receiver 25 in which the liquid distillate formed in the condenser 24 may in separated from the normally gaseous constituents. This normally gaseous fraction is removed from the. product receiver 25 through line 25. This fraction may consist principally of C: and lower boiling hydrocarbons.

The liquid distillate comprising the motor fuel constituents includin the C4 hydrocarbons is withdrawn from the bottom of the product receiverlithroughlinefl andmaybepmto an atter-fractionator 28. The top temperature of the atter-fractionator 28 may be regulated to take overhead through line 29 a vaporous fraction consisting principally of hydrocarbons boiling below about 150 F. and comprising the C4. C5 and C hydrocarbons.

Unvaporlzed distillate is continumlsly withdrawn from the after-fractionator 2! through line. Thisdistillatefractiomwhichmayboil between 150? P. and 450 E, is subjected to further cracking treatment. To this end, the product withdrawn from the receiver 28 through line 3| ispassedbymeans ofpmnp fltolineflinto I which additional catalyst is discharged through conduit 34. The resulting mixture of heavy naphtha and catalyst is thereafter throughlineflintothebottomsectlonofaretreatingchamberlithrougha cone 3. The temperature within theretreatlng chamberiimayrangefromfioo'ktolm'l'. Theheatnecesarytomaintainthedesiredtemperaturemaybesupplicd byhot regenerated catalystthroughlinefl,orthedistillatefractlonmaybesubiectedtosuitablepreheaflng before or after intermixing with the catalyst. The retreated vapors aftmposing through the conversim chamber 35 are remwedoverheadfllroughaflclmesepantorl'l andlineiltoasepamtefi'actionaiingtowerfl in which the! are subjected to I; Inc'- timation to remove higher boiling polymers fonned during the retreating The W m 01 m v-l I I!l.;-I\ formedduringthecracfingopenflonareremovedfmmtheflactlmatlngtowerflthrough linellandmaybewiththecycleoll inlntheprimarytowerliandmemunching a 5. The vapors remaining uncondensed in the iraction'ating tower 39 are removed overhead through 1ine 42 to a separate condenser 43 in which the normally liquid products are con-' 68 to a stabilizing tower 41 in which the products are subjected to combined distillation and fractionation to separate the same into a lower boll ing and a higher boiling fraction. The top temperature of the stabilizing tower 41 may be maintained at the same temperature as the afterfractionating tower 28 so as to take overhead through line 38 a lowerboiling fraction boiling below about 150 F. v The retreated heavy naphtha fraction is withdrawn from the stabilizin tower M through line t9 as a final product of the process. The-light naphtha fraction recovered from the after-fractionating tower 28 and the light naphtha fraction recovered from the stabilizing tower M are thereafter combined and may be passed to a butane tower 5i illustrated in Fig. 1A. Tower 51 is maintained under conditions controlled to remove'overhead through line 52 the C4 hydrocarbons. These products may be passed to an alkylation zone indicated symbolically by the rectangle 53 in which they are subjected to alkylation with or without extraneous isoparaillns and oleflns. The debutanized product is withdrawn from the bottom of the butane tower 5| through line 55.

According to one modification of the invention, this product, consisting largely of the C5 and C6 hydrocarbons, is passed through line 55 to a hydrogenation unit 56 in which it is subjected to low temperature catalytic hydrogenation for saturating the olefinic constituents contained therein. This hydrogenation may be carried out at temperatures of from 500 F. to 1000 F. and in the presence of various hydrogenating catalysts, The hydrogenated product may then be combined with the retreated heavy naphtha withdrawn from the bottom of the stabilizing tower 41. If desired, the hydrogenated products may be subjectedto redistillation and fractionation before being blended with the retreated heavy naphtha.

According to another phase of the present invention, the product withdrawn from the'bottom of the butane tower 5| is'passed through line 51 to a pentane tower 58 which is controlled to take overhead a fraction consisting principally of C5 hydrocarbons. The remaining unvaporized fraction is withdrawn from the pentane tower 58 through line 59 and is passed to the hydrogenation unit 56 previously described.

The C5 fraction removed overhead from the pentanetower 58 through line Si is then subjected to separate distillation and fractionation in tower 62 to separate a fraction rich in iso constituents and a fraction rich in normal constituents. The fraction consisting principally of normal constituents is removed from the tower 62 The products from the alkylation unit may then pass to a suitable distillation and fractionation tower 65 for separation of the desiredaviation alkylate.

UnreactedCr and C5 hydrocarbons are removed from the tower 65 through line 66 and may be passed to a butane tower 61 in which the butane is separated from the isopentane. The isopentane is withdrawn from the bottom of the butane tower 61 through line 68 and may be blended with the hydrogenated Cs hydrocarbons and aftertreated heavy naphtha. The aviation alkylate formed in the process may likewise be combined with the retreated and hydrogenated product. The vapors from the butane tower 81 may be passed into a second fractionating tower 69 for separation of the unreacted isobutane from the normal butane. The normal butane may be withdrawn from the tower 69 through line H and rejected from the process, and the isobutane may be condensed and rgcirculated to the alkylation unit 53.

No attempts will be made to describe in detail the conditions for effecting the alkylation of the C4 and C5 hydrocarbons, since these conditions are well known in the art and subsequent equipment necessary for effecting the separation and segregation of the resulting products is likewise stream may vary over an extended range, such as from 1 to 50 or more parts of catalyst per part of oil, both in the cracking and in the retreating operations.

A stream of catalyst is continuously withdrawn from the cracking chamber i2 through a vertical conduit i5 which discharges into a stream of air passing through line 16 and is passed into the bottom portion of a regenerator'l'l in which carbonaceous deposits formed during the cracking operation are removed. Likewise, a stream of catalyst is continuously withdrawn from the retreating chamber through a vertical conduit 18 which discharges into the air line 16. Regenerated catalyst is continuously withdrawn from the common regenerator Tl through conduits H and 34 for return to the primary and secondary stages, respectively.

The air velocity passing upwardly through th regenerator I1 is preferably controlled, as previously described, to maintain a relatively dense, fluidized, turbulent layer of catalytic material undergoing regeneration within the regenerator 11. Spent regenerating gas is removed from the top of the regenerating chamber 11 through a cyclone separator 19 and line 80. This stream may be passed to further equipment for the removal of the final traces of catalyst. This equip- 7 menthsbem-omlttedinthelntemtotslmplldl! abatflrcan'yhlgontthemtruflng. Theaackmammequiunmtmustntedinthe dnwhlllshltmfledtoshowammtinflflllld m nimum lmdn theflnehdivldndqhbstls mummhhdhltheflnllshtethrughtheaacklngmtreating and regenerating mm. In order to nahtalnflleda'indmfldflmaamllmtaf matlngurgasmbeat Wm h mmlsll,

,Iiandllwhetelncnhbsttflnktosetfle m mmal! 1 Having the insulin, It will he that it anlamesmchothundaflmuandas mewlthmtheqirltandmflmmt.

whathdslmdtohe l'qtwtadhylettualate entts:

LAmtorthedgamunem alieIu-awhflnmelwhichmm mmmmhmmt 8 naphtha traction: with said rem-acted heavy naphthatncflm.

llnthepmoeasdeflnedbydaimLthel'urther whlchcunprlseswtflnsthenaphthu obtained from both the hacking and recracking operations so that the lower balling .namthafiactlonhasmendpointbelowabout $.Amfurthemduaflouotgasolinemltahleforavlaflmfuelwhichoompflseswbjectlng a hlgher boiling all to cracking in the pmenoe' annulled toform ancleflmcgasolinefiacflnn, 1mm the uachpd products a lower bnflnmnaphthatrantionboflingbelowaboutm Eandahigherbofllngnaphthafractlomsubjeotlngsaldhtgherboilingnaphthaflactlontofurthat making treatment in the mm at an adivecncklngcatalyshfiomthezeili"i mfermoesamofrworflinthe The following fileofthlspatent:

UNITED STATES PATENTS Number Name Date 2,2! lloGxewr Mar. 10, 1942 2,289,116 Hamhner I July 14, 1942 2,310,321 Swans Feb. 9, 1943 2,348,599 mwn llay 9, 1944 2,360,253 Mnschner II Oct. 10, 1944 Roetheli Oct. 1'1, 1944 Ihfi July 31, 1945

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