US 3132089 A
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Description (OCR text may contain errors)
May 5, 1964 R. H. HAss ETAL 3,132,089
HYDROCRACKING PROCESS WITH PREHYDRoGENATIoN Filed Dec. 23, 1960 2 Sheets-Sheet 1 9 2 m m 2 h 3 q. J. 3 h S 2 May 5, 1964 R H HAss ETAL -HYDROCRACKING PROCESS WITH PREMYDROGENATION Filed Dec. 2s, 19Go United States Patent Ofi ice i This invention relates .to the hydrocracking of highboiling hydrocarbons to produce therefrom lower boiling hydrocarbons, boiling for example in the gasoline or jet fuel range. larly with certain optimum pre-hydrogenation techniques for conditioning the feedstock so that maximum eiliciency and catalyst life are obtainable in hydrocracking operations conducted at relatively loW pressures of below about 3,000 `p.s.i.g.,
'and relatively low temperatures, below'about 725 F. The inventionris especially adapted for the hydrocrackng of refractory, highend-pointfeedstocks', containing 4aromatic components boiling -above 600,rF., and `which may also be contaminated with organic nitrogen compounds and sulfur compounds.
-In broad aspect, the invention tionV of (lf) a substantially non-cracking pre-hydrogenaf tion step'conducted at temperatures below about`725 F and-utilizing an activef group VIII, free-metal hydro- The invention Yis concerned more particu? employed, the heavypolycyclic aromatic hydrocarbons comprisesV a combinan genation catalyst, followed by (2) a hydrocracking'step t v organicrnitrogen compounds; where the carried out at'temperatures below about feed to step',(1) must ordinarily be substantially free from feed is so contaminated, it is normally subjected first to `a hydroning and/or hydrocracking treatment, `using a transitional metal sulfide-type hydrogenation catalyst at a. temperature which is normally, though .not necessarily, higher V than the ,temperature used in the free-metal hydrogenation step.y Thus, in a more comprehensive aspect, the invention embraces two distinct` pre-hydrogenation steps, thef first serving the purposeof purifying the feed :by decomposing non-hydrocarbon impurities, and the second serving the purpose of partially hydrogenating certain 1 hydrocarbon components which are diicult to hydrogenateunder` conventional yhydrofining conditions.` Y i it 'is well known in the art'that hydrocracking catalysts become temporarily poisonedbybasic nitrogen compounds in" the feedstock. This poisoning effect is .evi-
,t dencedbydecreased -conversionof the feedstock under j a given set of conditions, a tendencywhich is reversed .l when theY nitrogen compounds areremoved fromythe.`
i feedstock. ,Furthen'it is known that thepoisoning effect offnitroge'n compounds can, `to some "extent, be overcome by operating at higher temperatures. However,v the use' of higher temperatures leads` to` increased -cokingVV become rather permanently adsorbed on the active cracking centers of the catalyst and are not effectively hydrogenated, thus blocking the active sites. Eventually, the adsorbed polycyclics may be converted to coke-like bodies through reactions of condensation and the like. VIt would appear that the distributionof active hydrogenation centers on the catalyst is such that they cannot act upon molecules which become first adsorbed on active cracking centers, at least in .a substantial number of cases.
It Ahas now been found thattbis deactivation effect can be substantially avoided if the hydrofined feedstock, con-V taining less than 25 and preferably less than L10 parts per million of basic nitrogen, is subjected to a vfurther hydrogenation, using catalysts and conditions selected so as to effect a partial hydrogenation of polycyclic hydrocarbons. Ordinarily, this second hydrogenation is conducted at a lower :temperature than the hydrofining step, but since the catalyst used in the second hydrogenation is intrinsically more`active for hydrogenating aromatics than was the hydroning catalyst, substantial beneficial effects are obtainable even at temperatures similar to those used in the hydrofining step. n Y
Witl respect to feedstocks containing organic sulfur and/or nitrogen compounds, the invention is based upon the precept that hydrogenaitingA conditions and catalysts which are optimum for decomposing Vthe organic nitro-f geni and sulfur compounds are not optimum for the partial hydrogenation of polycyclic hydrocarbons In ,n hydrofining operations, the catalyst must not be `sensitive to poisoning by nitrogen and sulfur compounds, andl this in itself precludes the use of catalyst which Vare most or nickel are most effective `for hydrogenating aromatics, asu compared to the corresponding, oxides or sulfides. Moreover,V denitrogenation is most` efcient when con- .'ducted atV relatively high temperatures,` i.e., above about 700v F., and preferably `above about 725 F. In the p temperature range of about700r to 800 F1, 'thehydroable forV hydrogenation. Hence, itwill be genation-dehydrogenation equilibrium forA paltially hydrogenated polycyclic aromatic hydrocarbonsis unfavorseen thatv the catalystsandtemperatures which are best forhydroning are not optimum for partial hydrogenation of polycyclic aromatics.l v According to the .present .in'ventionythe two operationsV are hence conducted separately4 under opti-`r mum conditionsifor each.
rates-and `decreasedcatalyst life, and is hence not a gen-v t.
erally feasible` solution tojthefproblern.V Ther solution `mostgenerally adopted involves pretreating thel feedganic 'nitrogen compounds to ammonia., andl then sending the 'nitrogenffree feedstock `to the. hydrocra'cking lreactor: f
of the catalyst as'the run proceedsrY This deactivation problemV isr particularly acute whenv using high-boiling feedstocks which contain aromatic components boiling stock,as by catalytic hydrofning,l tok decompose thefor-` It has now, been found that the foregoing plie-hydro-A` fning tefchnique'does not offer a complete-solution to the `hydro`cracking catalyst deactivation problem,rat least in` hydrocracking processes conducted' at low pressures V'of y below aboutiOOO p.s.ig., and preferably be`low.2,000` p.s".i.'gi fIt' has been found that, eVen.when all vof theVV nitrogen compounds are removed from-the feed by hydrot fining,fthere `is' still a substantial, progressive deactivationV above aboutf600 F; and up toabout 950Y It isY tion combined hydrogenation treatments v d d d i subjected to hydrpcracking at' relatively low temperatures It is perhaps possible that aising'le hydroning operai tionucouldrbe designed to effect both p vurposes,'usingl for example acobalt molybdate catalyst. "However, this would require either an enormous .capitalinvestrnent lin Vcatalyst Vand reactors to.` permit operating atlow space velocities, Y or expensive high-pressure equipment and permit loperating at pressures above about t facilities to 3,000p,s.i.g, vFrom the foregoing, Vcipal object of,- this invention is `toprovide optimum pre` forlfeedsfocks which are tofbe and pressures. A more specific objective is to Vprovidei maximum efficiency iria catalytic denitrogenation operaa'rornatics'. Still ing of feedstocks Vcontaining fractions boiling above about 650v AF.:` Still another `object is to improve theV efiiciency f 'and extend the catalystlife in hydrocracking operations 3,132,089 Y, Patented May 5, 1964 ii-,vwillheapparentthat the prind with `1a partial saturation olfpolycyclicanother object is to provide methods of t pretreatment which will permit .the` eii'icientlhydrocrack- 3 F. Other objects will be apparent from the more detailed description which follows.
The feedstocks 4which may be treated herein include in general any mineral oil fraction boiling above the conventional gasoline range, i.e., above about 300 F. and usually above about 400 F., and having an end-boilingpoint of up to about 900 F. This includes straight-run gas-oils and heavy naphthas, coker distillate gas oils and heavy naphthas, deasphalted crude oils, cycleoils derived from catalytic or thermal cracking operations and the like. These fractions may be derived from petroleum crude oils, shale oils,.tar sand oils, coal hydrogenation products and the like. ploy feedstocks boiling between about 400 and 900 F., having an API gravity of 20 to 35 ,`and containing at Specifically, it is preferred to emleast about 30% by volume of acid-soluble components p (aromatics-l-olefins).Such oils may also contain from about 0.1% to 5% of sulphur and from about 0.01% to 2% by Weight of nitrogen. Products derived therefrom include gasolines, naphthas, jet fuels, diesel fuels and the like.
Reference is now made to the attached FIGURE l, which is a owsheet illustrating this invention in one of its simpler aspects. This modification involves two stages ofy prehydrogenation, in both of which hydrocracking is minimized. The initial feedstock is brought in via line 2, .mixed with recycle and makeup hydrogen from line 4, preheated to hydroning temperatures in heater 6, and transferred via line 8 to hydroner l0, where hydrofining proceeds under substantially conventional conditions. Suitable hydroning catalysts include for example mixtures of the oxides and/or sulides of cobalt and molybdenum, or of nickel and tungsten, preferably supported on Va carrier such as alumina, or alumina containing a small amount of coprecipitated silica gel. Other suitable catalysts include in general the oxides and/ or sulides of the group VIB and/ or group VIII metals, preferably supported on adsorbent oxide carriers such as alumina, silica, titania, and the like. The hydroning operation may be conducted either adiabatically or isothermally, and under the following general conditions:
'HYDROFINING CONDITIONS Operative Preferred Temperature, 9 F 650-850 TO0-825 500-15, 000 1, OOO-l0, 000
The above conditions are suitably adjusted so as to reduce the nitrogen content of the feed to below about 25 parts per million, and preferably below about 10Y parts per i million. The resulting product is then withdrawn via line 12 and mixed therein with wash water introduced vialine 14. The mixture is then cooled and condensed in condenser 16 and transferred to high pressure separator 18. Aqueous wash liquorcontaining dissolved ammonia, hydrogen sulfide, etc. `is removed via line Ztl.
Recycle hydrogen is Withdrawn and recycled via line 4 as previously described.
Although little or no hydrocracking or hydrocarbons occurs in hydrofiner 10, the liquid product in separator 1S will still contain somehydrocarbons inthe gasoline range (e.g., 2 to 15% by volume), which constitute Y. mainly the hydrocarbon fragments from the decomposed nitrogen and sulfur compounds of the feed. This hydrolined product may be sent directly to second hydrogenation reactor 44 land hydrocracker 48, but normally it is preferable to'rst'separate" the gasoline fraction.v For this purpose, the hydroned product is advantageously.
blended with the effluent from the subsequent hydrocracking reactor to permit simultaneous recovery of the gasoline produced in both-operations. The condensate frompseparator 18 is hence passed via lines 22 and 24 to low pressure separator 26 (along with the product of I a ployed, the entire bottoms product from column 32 can be utilized, but sometimes aV small bottoms fraction is withdrawn via line 38 to prevent the buildup of nonhydrogenatable materials,` if such be present. Ordinarily this bottoms product will amount-to only about 1 to 10% by volume of the total feed to the column. In most cases however it is possible to recycle via line 36 the entire bottoms product from column 32, i.e., the entire frac tion boiling above the gasoline range.
YThe gas oil fraction in line 36 is then blended with recycle and makeup hydrogen from line 40, and the mixture is passed through preheater 42 and thence into second hydrogenation reactor 44. 'I'he preferred catalysts for use in unit 44 comprise the group VIII metals in finely-divided free form, deposited upon a substantially neutral adsorbent carrier such as alumina, activated charcoal, zirconia, titania and the like. As active hydrogenating components, the metals platinum, palladium, rhodium, iridiurn, ruthenium, nicke1,'cobalt and iron are specically contemplated. `The noble metals are ordinarily used in amounts of about 0.1 to 2% by Weight, while the iron group metals are used in amounts of about 2% to 20% by weight. Suitable hydrogenation conditions for use in reactor 44 are as follows:
HYDROGENATION CONDITIONS It may be noted that the above conditions overlap somewhat upon those speciiied for the hydrofining operation.
45. The use of kthe preferred metallic catalysts on reactor 44 makesit feasible to use the same or higher temperatures therein than the temperatures used in hydrofiner 10. However, it is preferred inmost cases to use lower temperatures. actor 44 (the reaction being exotherrnic) a portion of the cooled recycle hydrogen in line 40 may be diverted via line 46 to one or more mid-points in the reactor.
ever, any other desired temperature control means may be utilized.l
The effluent from reactor 44 is transferred directly to low-temperature hydrocracking reactor'l 48 via line 50.
If desired, additional cool hydrogen may be injected into line 50 via line52 in order to bring the mixture to the desired initial hydrocracking temperature.
Inasmuch as reactors 44 and 48 are preferably operated at the same pressure, itis entirely feasible to enclose both contacting zones'jwithin a single reactor, using appropriate temperature control means. .f
t The catalyst employed in reactor 48 may consist of f any desiredcombinationof arefractory cracking base with a suitable hydrogenating component. Suitable lcrackj ingv basesinclude yfor .example mixtures of two or more refractory oxides such as silica-alumina, silica-magnesia,
` silica-Zirconia, alumina-boria, silica-titania, silica-zirconia-titania, `acid treated clays and the like. Acidic metal phosphate gelssuchas aluminum Iphosphate may also be used The preferredv cracking bases comprise composites of silica .and alumina containing about 50%-90% silica; Acomposites of silica, titania `and'zirconiacontainingbetween 5% and l752% of each'component; decationized., .z whitareselling msleular saves ofthe Y crys- Due V Lto the second hydrogenation step to be subsequently em- To maintainthe desired temperature in re- How- , metals may also be Y foregoing.
. 48 areas follows;
i L l V1 to 10% Vcombination thereof.
tal type,having relatively uniform pore diameters of about 9 to 10 angstroms, and consisting substantially exclusively of silica and alumina in mole-ratios between about 4:1 and 6: 1. Any of thesecracking bases may be further promoted by the addition of small amounts, eg., by weight, of halides such as tuorine or boron triiluoride.
The foregoing cracking bases yare'normally compounded, as by impregnation, with from about 0.5% to (basedron free metal) of a group VIB or group VIII metal promoter, eg., an oxide or sulfide of chromium, tungsten, cobalt, nickel, or the corresponding free` metals, or any Alternatively; even smaller proportions, between about 0.05% and 1.5% of the metals platinum, palladium, rhodium or iridium may be employed. The oxides and sulfides of other transitional used, but to less advantage than the v A particularly suitable class of hydrocracking catalysts is composed of about 75-95% by weight Vofvarcoprecipitated` base containing 5`-75% SiO2, 5-75% 5-75 TiOZ, and incorporated therein from about 5-25 based on free metal, of a group VIII metal or metal sulfide, e.g., nickel or nickel sulde.
'Y Y A key feature of the process resides in utilizing economically feasiblepressures inreactor 48 (below about 3,000vp.s.i.g., and preferably below 2,000 p.s.i.g.), While at'the same time utilizing temperatures sufficiently low toV avoid the dehydrogenation of the partially hydrogenatedpolycyclic. hydrocarbons which were hydrogenated inreactor 44. At temperatures above-about`725"` F., the dehydrogenation of these materialsbecorne significant and is reected in a relatively rapid rate of deactivation of the catalyst. However, at temperatures below about 725 F., and preferably -below 700 F., it is found i that highly..efiicienthydrocracking, with-30% to 75% conversion per pass, may vvbe maintained lfor Very long ,periods of time, i.e., for periods lof atleast -about 4 months, and usually lmore thanV 8 months. Here again, suitable means may be eniployed'to control the exothermic temperatures rise, as for example by injecting` cool hydrogen at one or more points in the reactor, as illustrated via Zr02, and
line 54. Reaction conditionsV contemplated for reactor HYDROCRACKING CoNDrrroNs Operative :Preferred Temperature, F i 40u-725 50o-too Pressure,p.s.i.g- 50G-3,000 t300-2,000 i LHSV, v;/v./h A 0.5-15 .1-10. `Hz/oll ratio',s.c.r./b u 50G-15,000 "200G-12,000'
AThe products from reactor 48 are withdrawn via line 56,
condensed in condenserSS and` transferredto high-pressure separator 60. Recycle hydrogen is withdrawn via liquid` product is Vvtransferred (in ad` drofiner eflluent) Via lines 62,1122 and 24g-to` low pressure separator 26 and column 32,1.a`s previously described,
rReference fis nowfrnadeto' theattachedl'FIGURE 2, whichisa liowsheet illustrating a modification of 4the genation-hydrocracking Vstage involvesltwo possible-modes feedstock contains .about L2-50 parts per million of nitrohydrogen from line ,102, passed throughl open valve'f v104,
temperature hydrocracking reactorjlltl. ValveI-IZ is conditions at temperatures relatively higher than those lir'1e1'40,l and recycled as'previously described, whilethe mixture with the yhyline` .106, `preheater `i108, and .thence directly Linto highclosed thereby bypassing hydrofining reactor -Inrhyf i drocracker 1,10, theA feed issubjected to hydrocracking 156., repressured in 140, `120, 102, 142, 144, 146 and l148 to the various invention whereinrsthe" first 'stage' of hydogenation also involves a hydrocracking operation.v .'Thisjfrst hydrok 653 offoperation.v The Afirst'mode presumes thatfthe initial gen as organic nitrogencompounds, in lwhich caseit-may be broughtgin via line-100, mingled-thereinwitherecycle'.
V.Via-line 150 and to be employed in thefsubsequent low-temperature hydro!V cracking step. Denitrogenation and desulfurization take place concurrently with hydrocracking. Catalysts suitable for use in hydrocracker 110 maybe of the same general type as previously described for use in hydrocracker 48 of FIGURE 1. However, itis preferred to use here a catalyst wherein the hydrogenating component is in the form of a sulfide, eg., nickel sulfide. Hydrocracking conditions contemplated for reactor 110 are as In cases where the initial feedstock in line contains Y substantial quantities of organic nitrogen compounds` (e. g., more than about 50 parts perY million of nitrogen), an alternative operation is preferred, utilizing hydroner 114. This alternative may also be utilized for feeds containing less than 50 parts per million of nitrogen, if desired. In
either'case, valve 104l is closed and valve 112 opened,
whereby the feed-hydrogen mixture flows through pre-` heater 116 into hydrofiner'114, where it is subjected to hydrotining, utilizing catalysts and conditions as'previously described in connection with hydroner y10 of FIG- URE l. The'total effluent from hydrofiner 114 is then Withdrawn Via line 118 and sent via line 106 and preheater 103, to hydrocracking reactor 110, where itis subjected yto hydrocracking under the conditionspreviously described. Preferably, the hydrofning effluent in line 113 is sent directly to hydrocracking, without intervening condensation and separation of ammonia and hydrogen sullfide, but the alternative operationis also contemplated. Removing the ammonia and hydrogen sulfide improves the efficiency of hydrocracking in reactor 110, but entails the added expense of the additional facilities and utilities required. The temperaturein reactor 110 may be Vcontrolled by theinjection' of cool recycle hydrogen atone or more midpoints, as illustrated via line120.
In either of the above alternatives, the effluent from hydrocracker is withdrawn via line 122, blended in line 124 Vwith, effluent from the succeeding -loW tempera- ,ture hydrocracker, and the resulting blend is then passed Via line 126 and condenser 12S-to high pressure separator 130. VWhere the efiluent inline-122 contains ammonia and/or hydrogen sulfide, it is preferred to inject wash i Water in'to line 126Via-line 132, which is later-'Withdrawn from separator 130 via line 134. ,It will be noted that` 'this modification of the process embraces asingle hydrogen recycle system for the entire process. `All, of the recycle hydrogen is withdrawn from-separator 130 via line `blower 13S and distributed via lines processrunits. l Y Y The liquid condensate in separator 130 iswithdrawn line'142, passed through preheater`164, andinto low temperaturehydrogenaton unit 166; In rare cases where itis Y Y necessaryto withdraw a bottoms vproduct from column 1,56, thisl is done via linelf. l According-toene modiflashed into low pressure separator *15.2,* from which Cl-*C3 flashgases are withdrawn via line 154-; A Theliquid product in separator v152 is then transferredto `fractionating column 156 via line 158,` wherein it is subt jectedto fractionation inagmannersimilar to that de- Y scribedin connection kwith column 32 of FIGURE: l. -Here again,-th e `'gasolineproduct is taken overhead vialinelt), 1 andf-a-gas-oil sidecut, or the total bottoms, `traction, is with- '.drawn .via line 162, blended Withj recycle hydrogen from most cases however, it is preferred to send substantially the entire gas oil fraction boiling above gasoline from4 column 156 through low-temperature hydrogenation unit 166,.
` The catalysts and conditions of reaction to'be utilized in hydrogenation unit 166 and hydrocracking unit 172 are substantially the same as those previously described in connection' with hydrogenation unit 44 and hydrocracking reactor 48, respectively, of FIGURE l, and hence will not be again described. The efliuent from hydrocracking reactor 172 is withdrawn via line 174, blended with the product from line 122, and the blend is then treated as previously described for recovery of gasoline, and unconverted gas oil feed for units 166 and 172.
The particular advantage of the combined process of FIGURE 2 resides primarily in the obtaining of an appreciable conversion of the initial feedstock to gasoline by an operation which is substantially integral with the pre-hydroiining treatment. It has been found that where the initial feedstock is low in nitrogen, or if high in nitrogen has been treated by hydroiining toconvert the organic nitrogen to ammonia, a substantial degree of hydrocracking may be carried out economically in reactor 110 Vbefore the product is condensed to remove ammonia and hydrogen sulfide.
This hydrocracking operation is Y not as ecient in absolute terms as the hydrocracking in reactor 172, but is advantageous because the added conversion can be obtained at a total cost which does not greatly exceed the cost of hydroning alone. Thus, by
converting about 15 to 35% of the feed to gasoline in hydrofiner 114 and hydrocracker 110, `the size of units 166 and 172 may be appreciably reduced thereby reducing the overall capital expense. The key to the success of this operation resides in maintaining higher temperatures in hydrocracker 110 (e.g., 50-100 F. higher than in hydrocracker 172), thereby permitting a 10 to 25% conversion to gasoline Without encountering rapid deactivation of the catalyst as a result of the nitrogen and sulfur present.
The following examples are cited to illustrate the critical novel features of the invention, but are not to be, construed as limiting in scope.
Example I This example illustrates the difficulty encountered in' obtainingadequate pretreatment of hydrocracking feedstocks by hydroning alone, and also illustrates the critical conditions required to achieve adequate pre-hydrogenation of polycyclicl aromatic hydrocarbons.
The initial feedstock was a heavy coker distillate gasoil obtained by the delayed coking of a California crude.
oil, andv boiling between about`4l7 and y860 F. (5 to 95% boiling points, Engler). feedstock contained about 0.363 weight-percent nitrogen, and 2.1% sulfur. It had an API gravity of 21.9, an aniline point of 120.
F., and contained weight-percent'acid-soluble'corn-` foregoing feedstock was subjected l to hydroiining'at 1,800 p.s.i.g., 0.5 LHSV, avera'gepbed temperatures 755 to 760 F.,emp1oying 5,000,s.c.f. of hydrogen per barrel. The catalyst `was-a'presulided cobalt oxide-molybdenum oxide-alumina catalyst containingV the equivalentof about 3% CoOand15% M003'.` Analysis of the hydroned product showed that the usulfur content had been reduced to 19 parts per million, and the basic nitrogen contentto l 'part-'per million. However,l
' from v63.61tc') 60.5, -demonstrating a much lower rate of M activityk decline, and better cracking eliiciency.
it still contained a substantial proportionof aromatic comf ponentsfas indicated by Vanacid-solubility of125 ABy ultraviolet spectranalysis it Was-foundtocontai 3;7%
which corresponds to a conversion of about 39%.
`A`lOver a period of 12 hours, the average `conversion to ,cut-s' was substantially constant (743:9, 43.7, 44.1, 42.7,
by Weight of naphthalenic compounds, and substantial amounts of higher polycyclic hydrocarbons, as indicated in Table l, below. It willl be shown in Example II that this hydroiined product rapidly deactivates a hydrocracking catalyst when the hydrocracking is conducted at low temperatures and pressures. i
To demonstrate the feasibility of further improving this product for use as a hydrocracking feedstock, several hydrogenation runs were carried out over an activated charcoal catalyst containing about lweight-percent of platinum. All runs were carried out at 2 space velocity, and at temperatures indicated in Table l. Analyses of the respective products for aromatic types gave the following results:
TABLE 1` Hydrogenation Temperature, F. Product Analyses, wt. Y
percent Feed Biphenyls Triaromatics.-- Benzoiiuorenos Pyrenes Example II The hydroiined feedstock of Example I (having an API gravity of' 30.8, and an Engler boiling range of about 40G-790 F.) was subjected toY low-temperature hydrocracking, using ahighly active catalyst consisting -of a copelleted mixture of 50% powdered activated alumina, and 50% of a powdered commercial isomerization catalyst comprising 0.5% of palladium impregnated upon a decationized, zeolitic Y type molecular sieve having a uniform pore diameter of about 9-10 A, and composed of il% SiOz, 25x-1% A1203 and about 1.5% NaO. This palladium-impregnated molecular sieve is a commercial isomerization catalyst manufactured by LindeA Co., Tonawanda,v N.Y., under the trade name MB 5390. Upon subjectingv the feedstock to hydrocracking over the composite catalyst at 550 F., 1,500 p.s.i.g., 1.0 LHSV, with 10,000 s.c.f. of hydrogen per barrel of feed, a 68.3% average conversion to gasoline and lighter materials was obtained over'a 12-hour run; However, the API gravity of progressive product cuts taken at 2-hour intervals dropped from 58.9 to 48.4 over the run, showing that the conversion was dropping rapidly. Itis hence apparent that the catalyst was being rapidly deactivated, as was confirmed by continuing the run another 4 hours, at which point the product gravity had dropped to 44.1,'
The foregoing run was repeated except that the feed was rst passed over a bed of 0.5% platinum-on-alumina hydrogenation catalyst, and thence directly into the hydrocracking zone; The hydrogenation conditions were substantially the sameV as theA `hydrocracking conditions.
gasoline and lighter materials was above and the API gravity-ofthe 2-hour product cuts dropped only This -run Wasrthen continued for anotherv40 hours at areduced temperature of 525 F., during which time the conversion" dropped from about 60%y't'o about 35.50%.v However, most. signicantly,rduring the last 14 hours'of the run, the :API gravity of the progressivevZ-hour product A' 42.8, 42.9 and 42.8), `proving that therate of catalyst `deactivation had levelled out.. At this .point the hydrocracking temperature was again raised `to 550V F., for
j l2 hours, and theconversion rose to 49.5% and remained i This exampledemonstrates that even with optimum prehydrogenatioof thefeed, unsatisfactory results are of vcatalyst .deactivation rates.
obtained. in subsequent hydrocracking operations conducted at temperatures above 725 F., at least in terms It also demonstrates the actual deleterious Velfectsof polycyclic aromatics in lowpi'essure hydrocracking. v n d The primary feedstock was alight coker gas ol boiling between 400 and 600 F., having an APIgravity of 30.3,` and containing 2% byl weight of sulfur, 0.15%V nitrogen, and 5l volume percent acid solubles. initial pre-hydrogenation treatment was an integral vhydroining-hydrocracking combination as illustrated in FIGURE 2.` The hydroning conditions were: tempera- A,ture 725"-750"V F., pressure 1,575 p.s.i.g., space Velocity 2.0, H12/oil ratio 5,000 s.c.f./ b. The hydroning catalyst was the same as in Example I. j Hydrocracking of the hydroliner ellluent in reactor 110 was carried out at 1,500 p.s.i.g.'and about 750 F., over a hydrocracking catalyst consisting of a coprecipitated composite of the oxides of nickeL,` silica, zirconia and `titania (NiO-25%, SiO2 15%, ZrOz'-37.5%, HOT-22.5% the entire composition having been completely presulded. Notwithstanding the presence of ammonia in the hydrocracking zone, about 21% by volume of the feed was converted to gasoline in the hydroining-hydrocracking combination, and
recovered by distillation. The unconverted gas oil was essentially free of nitrogen and sulfur, but still contained a substantial proportion of monocyclic and polycyclic aromatics, as indicated in Table 2 below. This unconverted oil (blended with a smaller proportion of a hydr-ocracking cycle oil of similar characteristics) was then used as the experimental feedstock in the following comitsfaliquot of 80% parisons:
A. A portion of the experimental feedstock was Vfractionated to recover a bottoms fraction boiling above about 550 F., and the bottoms fraction. was treated with activated alumina to adsorb heavy aromatics, then rcblended with the 80% overhead fraction, giving hydrocracking feed A. f 'l The i B. Another portion ofthe 550 F.-lbottoms fraction prepared as in A above, was hydrogenated'at 550 1*. and 1,500 p.s.i.g. over a0.5% `platinum on alumina catalyst, using 10,000 s.c.f. of hydrogen per barrel of feed. VThe hydrogenated product was then reblended with overhead, giving hydrocracking feed LLB'H,
C. Vlulydrocracking feed C was a portion of the uni l treated experimental feedstock.
. Ultraviolet spectroanalysis of the above feeds showed the. following aromatics contents:
TABLE 2 l l reed A Feed B reed o Aromatics (AlzOa- (Hydro- (Untreated) genated) treated)r lttonocy'clic, wt. percent..-..-.'...` 1 y 25.4 y 7 24.0 Naphthalenes, wt. percent.. 2. 2 1. 8 2. 56' Biphcnyls, wt. percent. 1.06: 0. 9V A L29 i Tri-aromatics, wt. percent .0.'008 40.009 0.138
' It will be seen thatthe tri-aromatics were markedly reduced, both b y the hydrogenation and aluminaV treatments., But in the case of hydrogenation, thepartially hystock boiling .above the TABLE 3 Run No. 1 2 a Feed A B c (A12O3- '(Hydro- (Untreated) genated) treated) Length of run, hrs A 56 56 72 Temperature range over run, F. 725-731 734-750 748-777 Temperature increase per day,
j F. (TIR) 2.9 6.9 9. 4 Average vol. percent conversion-- 63. 8 60.2` 57. 7
It will thus be seen that, at hydrocracking temperatures above about 725 slightly better than the untreated feed, in respect to catalyst deactivation rates. However, feed A, from which the tri-aromatics and higher had been physically removed gave markedly improved results. As indicated in Example Il, however, feed B would have given satisfactory i results at lower hydrocracking temperatures.
Results analogous tothose indicated in the foregoing examples are obtained when other hydrogenation' cata- Y lysts, hydrocracking catalysts and conditions described herein are employed. It is hence'not intended to limit the invention to the details of the examples, but only broadly as defined in the following claimsz We claim:V 1. A process for hydrocracking a mineral oil` feedgasoline range, and containing polycyclic 'aromatic hydrocarbons boiling above about 600 F. and organic nitrogencompounds, to produce therefrom hydrocarbons boiling in the gasoline range, which comprises:
(A) subjecting said feedstock plus added hydrogen y'to an initial catalytic hydroning treatment at a n temperature between .about 650 and 850 F.7in the presence of -a hydrotining catalyst selected from the blass consisting of the group VIB and group VIII metal suldes supported on a substantially Vneutral adsorbent carrier; ,K (B) subjecting the eflluent from said hydrotm'ng without intervening separation of ammonia, to a first catalytic hydrocracking lat a temperature between about 600'." land 850 F., in Contact with a hydrocracking` .catalyst comprising a group VIII metal sulde hydrogenation component supported upon a refractory oxide cracking base selected from the class consisting of silica-.alumina cogels, zeolitic alumino-silicate molecular sieves, and halide-promoted cracking bases.;
` (C) treating the product from said first hydrocrack-` ving step to separate out ammonia, gasoline, and unconvented gasoil;
n temperature which is i Y of a'metallic group VH1 noble metal hydrogenation catalyst supported on a substantially neutral adsordbent carrier;
(E.) subjecting the hydrocarbonV4 eluent from. said second hydrogenation toa second' catalytic hydro- F., the hydrogenated feed B was only.
11 cracking at a :temperature which is'(a) between about 400 and 725 F. and (b) -lower than the temperature employed in said rst hydrocracking step (B), and in the presence of a hydrocrackng catalyst f comprising a group VHI noble metal supported on a refractory cracking base selected from the class consisting of silica-alumina cogels, zeolitic aluminosilicate molecular sieves, and halide-promoted cracking bases;
(F) recovering gasoline-boiling-range hydrocarbons 'from the hydrocracked product from step (E), and lwherein (G) all of said hydroning, hydrogenation and hydrocraoking steps are conducted at pressures between yabout 500l and 3,000 p.s.i.g.
, 2. A process as defined in claim 1 wherein each of said hydroning, hydrogenation and hydrocracking steps are carried out at pressures below about 2,000 p.s.i.g.
3. A process yas dened in claim 1 wherein uncon-A v'erted gas oil recovered from the effluent from said second hydrocracking step is recycled to said second hydrogenation step.
4. A process as `deiined in claim 1 wherein said substanti-ally neutral adsorbent carrier used and (D) is activated allumina.
5. A process as defined in claim 1 wherein said refractory cracking base used in steps (B) and (E) is a dein steps (A)V 12 oationized crystalline molecular sieve of the Y crystal type wherein the mole-ratio of silica/alumina is between about 4/1 and 6/ 1.
6. A process as defined in claim 1 wherein the group VIII noble metal `ort said hydrocracking catalyst used in step (E) is palladium.
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Great Britain Jan. 5, 1948