[1]T T 3,083@90 ti riited St6l@tes Patent Office Patentecl May 7,1963 @,088,903 HYDROCRACIL@NG I?@ROCESS AND CATA'R-YSTS Rowl?nd C. H-ansford, Fullertor., Calif., assignor to Uuion 0111 Compauy of Californ;a, Los An-.eles, Calif., a corpo;"ation of CalifornL@ 5 No Drawin.- Filed May 11, 1961, Ser. No. 109,246 14 Cialins. (Cl. 208-10-9) This invention relates to the hydrocrarking of highboiling mine.-al oils to prodtice therefrorn lower-boilin,@ 10 hydrocarbons, boiling for exa-,nple in the gasoline range. The invention is irore particularly directed toward the PrOViSiOn Of new and novel catalysts for use in hydrocracking processes, and other acid-catalyzed - reactions. Briefly, the essential novel eleme-ilt of the new catalysts lti of this inver@tion is a hig'nly acidic cracking base composed of a metal phosphate gel chemically - compounded with silicon tetrafluoride. The finished catalyst also includes a conventional hydrogenatin@ component such as a group VIII metal, which may be separately added to 20 the crackin.- base a@@ by impregnation, or may be chemically compounded therewith as metal phosphate. It has been fornd that silicon tetraffloride added to such metal phosphate gel bases induces an unusually stable and highly acidic function in the catalyst. The catalysts of 25 this invention possess the unusual property of - catalyzing desired hydrocracking reactions at very low te.,nperatures, e.g., 400' to 700' F. It is known that the activity of various gel-type oxides, such as alumina, for promoting acid-catalyzed reactions 30 su-,h as isomerization and cracking can be improved by combining therewith a halogen function surh as fluorine or silicon tetrafluoride. Xerogel structures, such as those of activated alumina, are generally thou,-ht of as being anhydrolis, but actually they contain small amounts of 35 water in the form of hydroxyl -roups attached to the aluminum atoms; the removal of all such hydroxyl groups would destroy 'Llie .-el structure. Thus, when activated alumina gel is react,-d with silicon tetrafluoride, the following type of reaction is believed to occur: 40 >Al-OH+SiF4-->>AI-O-SiF,+HF The hydro.-en fluoride which is liberated in this reaction can then react with other hydroxyl groups as follo@.vs: >Al-OH+HF->AI-F+H20 4 L5 Thus, the fluorine which is introduced as SiF4 can terminate in form-s bonded directly to Vae aluminum, or to the sil-,con atoms. Both types of fftiorine are believed to fur-iiish desirable acidity on the @atolyst. However, wheti 50 water is present in feedstocks being treated over such materials, the following ex-,mplary @ypes of reactions cari ocelir, which may result in the fluorine tiltimately appearing as aluminum trifluoride: 1 >Al-O-SiF3+H20->AI-O-SiF20H+HF 55 >AI-O-SiF201-@T+H20->AI-O-SiF(OH)2+HF AIF(OH)2+2HF-AIF3+21-120 In addition, basic aluminum fluor@',des can disproportionate at high temperatures to yield aluminum trifluoride, 60 e.g., as follows: ZAlF20H-AIF3+A!F(OH)2 At tlis point, it is important to note that alumitium trifluoride is an extremely stable, ionic compound, and is substantially completely inactive for promoting - acid-cata- 65 lyzed reactions. Apparelitly, the presence of a hydroxyl grotip, or an oxygen bridge, on the same alumin,,jm atom with a fltiorine atom is necessary to form the acidic centers which can catalyze acid carbonium ion type - reactions. While the fore.ooing is lar.-ely hypothetical, it does offer 70 a rational explanation for the siibstantial difficulties which 2 have been experienced in the past with the use of fluorided or silico-flliorided alumina -el catalysts. Such catalysts may exhibit a very desirabl'e initial activity but the activity is soon observed to decline under process conditions, even though little or no fluorine is volatilized from the catalyst and taken off with the product. Apparently, the active forms of flilorine are converted -radually, as a result of hydroly'Lic or disproportionation reactions, to the substantially inactive daminum trifluoride. When this occurs, the activity of the catalyst may sometimes be restored, again temporarily, by adding more fluorine or SiF4 to the catalyst. BuL this cannot be continued indefinitely, because soon the entire gel structure is destroyed with most of the alumina beinconverted to aluminum trifluoride and aluminum silicate. The principal objective of this invention is to provide catalyst bases tipon which silicon tetrafluoride may be incorporated in a form which remaii)s active for substantially longer p-@riods of time. Another object is to provide halogenated hydrocraeking catalysts which will maintain their activity for lon@. periods of tirr,@e. Still another object is to incorporate silicon tetrafluoride in' o gel-type catalyst structures in such a way that the fluorine does not ultimately terrninate in a non-acidic structure. Other objects ,Rill be apparent from the rnore detailed description which follows. It is known that gelatinous phosphates such as aluminum phosphate are somewhat active as cracking catalysts (cf. U.S. Patent No. 2,301,913). It has now been discovered that by combinin.- such gelatinous phosphates with silicon tetrafluoride, the cracking activity is substantially improved, and the halogen component appears to remain active for substantial periods of time. Due to the complexity of metal phosphate gel structures, it is difficult to state witli certainty the chemical reacions which take place when they are treated with SiF4. However, in reference to aluminum phosphate gels, the following equations illustrate wbat are believed to be exemplary reactions: 0 osiF3 / Al-OP(OH)2 + SiF4 AL-OP + IIF OH HO 0 osiF3 F 0 osiF3 II/ II/ A L-OP + HF A L-OP + H20 O H O H r, 0 OSiF3 F 0 OSiF20H ALOP + H20 ALO-P + HF OH OH It would be experted that all of the ftuorine appearing in the above structures would be highly active for promoting acid-catalyzed reactions. Moreover, due to the presen--e of the phosphate moiety, it is substantially impossibl@e, under norrrial conditions for any significant portion of the aluniina to be converted to aluminum trifluoride. These reflections may well explain the observed catalytic activity and stability of the resulting compositions, but are not intended to be limitin.- in their eflect. I have recently shovin (copending application No. 50,8,57, fded August 22, 1960), that a similar acLivation (yf phosphate gels can be obtained by addina, boron trifluoride thereto. However, the use of silicon tetrafluoride is folnd to be even MOTE advantageous from the standpoint of stability in th-- presence of waler, because, Nvhereas boron'trifluoride can become hydrolyzed to boric acid which is volatile, the complete hydrolysis c@f silicon tetrafluoride gives silica, which is nonvolatile. The net result is that the silicon tetraffuoride-treated catalysts tend to retain tlleir activity in the presence of water for a longer period of time than the BF3-treated catalysts.
[2]3 Metals whose phosphates can be prepa-red in the fori-q of exte@ided gel structures include substantially any of the polyvalent metals, particularly the metals 6f groups ILA@, IIIA, IVB atid IIB. Exai-ilples of sLiitE@.ble phosphates i.,iclude tita,-i,'.Um phospha'Le, zirconium phosphat-,, boron phosphate, zincphosph,-,te, eadriiirm phgsphate, chro -miur@l phosphate, cobalt phosphate, n;ckel phosphate, iroii phosph,ate, ma.-nesium phosphee,. tanci of course ai-Liminum phosphate. The gel phosphates of the rnetals of group V.IB and group VIII already possess the desired hydrogenatlr@@ function @and hence may be ritilized as such, or com,biiied with olh--r ractal phosphates,. or other supporting materials. For purdoses of prepaxing ael,iie hydrocracking catalysts, the p@osphates o'L alumir@um, chromium, titanium and zirconium are pre4,@rred. W,hile the substantially neutral n-ietal phospha@'L.-s may be enployed (i.e., those containing a stoichiori-ietric ratio of phosphate to metal), it is conter@iplated that the cor.responding basic pho@-phates or acid phosphates iiay also be used, so long as a xerogel stracture caii be oblained by controlled dehydration. 'vvhile any proportion of phospha.te ions zadded to the hydrous oxid-.s will effect som@- improvement in respect to the stability of the siliceii tetraffuoride treated products, it is preferred to employ me,al phosphates wherein the metal/phosphortis atomic ratio falls within the range of 61x to 3/2x, x bei-iig the valence of the metal. This includes bo@h the theoretically nelitral metal phosphales, the acid phosp'pates ,vherei.1 at least half (yf the piiosphoric acid groups are th,-oreticdlly neulralized by th-, riietal, and tl--e basic phosphates wherein at least half of the ipetal hydroxide grotips are theoretically nei-itralized by phosphoric @acid. To prepare the foregoing n-letal phosphates ir@ gela'@nous form, it is preferred to precir@itate the same 'rom an aqueoi-is solution of a so!Llble salt of the polyvalert metal, The precipitation may be accomplished by varictis means ' d,-pending upon the metal, and the proportion of phosphate ions desired in the final product. The polyval--nt metal phosphates are in general quite insolilblewithin the pH range of about 4-9, but their solubilitias vary considerably at higher or lower pH ranges. To obtain precipitation therefore it is only necessary to provide iTi solution the desired ratio of phosphate ions at tlleappropriate pH range for prec@oitation. Where basic, phosphates are desired, the final p-.I-l of precipitation will a,@ways be above about 5, ard usually above 7. 'Ih-, pl-I may be adjusted upwardly by the addition of approp@riate bases which forms sollible phosphates, e.g., amrnonilim hydroxide, sodium hydroxide, etc., or down@wardly by adding appropriate acids which form soluble polyvalent metal salts, e.g., nitric acid, hydrochloric acid, etc. In the case of aluniinum phosphate gels for exarpple, -the preferred technique is to add an alkali such as ammonium hydroxide to an acidic solution of theallimiiium salt plus the desired ratio of phosphate ions. Prec@'@Pitation will be substantially complete within the 2-6 p@ll ran,@e, depending upon the ratio of aluminum salt to phosphate ions and perha-os other factors. The phosphate ions may be,added as phosphoric acid, or any con-lpatible solu,ble salts thereof, e.,-., ammonitun phosphate. Normally, it is preferable to adjust the pl-I of the ini@lial solution by using phosphoric acid, but other compati'ole acids may be used, e.-., nitric or h3,drochloric. In the case of alumir,.um phosphate and other acidsoluble polyvalent metal phosphates, an especially desirable homogeneoi-is precipitation may be obtained by the use of a delayed precipitant such as Lixea. 1-ii this toc-hnique, urea is added to the acidic polyvalent metal solution instead of ammonia, and the resulting solutioii is then heated to e.g., 50'-200' C. to effect the release of ammonia, with resultant homogeneous gelation tliroiighout the solution. The resulting gels are found to exhibit an unusually hi,-h surfac-- area @and acidity, especially when the mole-ratio of phosphate ions to aluminum silt is between aboiit 0.02 atid 0.9. This terhniqiie is riaore par3,088,908 ticula@-ly described in my copenclitig applica',ion No. 81,2.'32, filed January 9, 1961. Mixed metal phosi)hates can be readily prepared by s;mply using a mixture of soluble salts ir. the inilial pliosphoric acid solution. For exalr@ple, -,@,here it is de3ired to prepire a c,,italyst compris@"n,- a mixiure of aluminum phosphat,- and a hydrogenalirig metal pliosphate such as r@-',Ckcl pho@,phate or chrorr@i,,im phosphat@, mixtures of alum;num chloride and nickel chloride, or of aluminum 10 c-liloride and ch@-omium chloride may be coprecipitated as the hych-ous phosphates by the foregoirg techniqties. Sirriilarly, it is conten-iplated that mixtures of aluminum phosphates and zirconiuni phospbates -nay be prei)ared by coprecipiteion from,an aoueous solution of aluminum 15 chloride and zirconium chloride, either by the addition of alkali, or a htlo,-C.-i acceptor stich as ethylene oxid,-. Following pre.-ipitation of the -w@etal phosphate, it is ordinarily des'lrable to wash the hydrous gel in ord--r to remove soluble salts, or any,adhering or.-anic compounds 20 such as ethylene chlorohydrin. For removing the lat,er, it is preferred to wash with;an alcoliol stich as ethanol or isopropanol. Ammoni-am salts, such as tne chloride, may be removed byv-,porization during calr-ining. Generally, the phosphate gels prepared by precipitation with an or25 ganic apion-acceptor such as etliylene oxide or wiih a delayed gellin,@ agent such as urea, display a hi.-her surface area in their xero-gel form than do the corresponding phosl)hates prepared by coprecipitation with bases such as ammonia . 'lhe washed gels ue then preferably dried 30 at e.g., 200' to 500' F., and theii calcined at a higher temperatlire of e.g., 700' to 1,200' F. ifor I to 12 holirs. If it is desired to incorpo@-ate a hydrogen-ating component surh @as nickel or chromium by ii-npregnation, this may be efferted by conventional methods such as im35 pregnating the wet or calcined phosphate gel with appropriate aqueous solutions of soluble salts such as nickel nitrate, which are Lthen decomposed during a subsequent calcining to form ei@ther nickel oxl:de and/or nickel phosphates. Preferably, th-. calcined catalyst is then reduced 40 with hydrogen at e.g., 500'-900' F. 'to convert the lmprogriated salt tb the free metal. The last comoorent to be added to the catalyst is Grdiiiarily the silicon tetrafluoride. The phosphate gels should preferably be subjected to the calcining treatment 45 to reduce -the hydroxyl water content to about 0.01-5% by wei,-ht prior to the SiF4 treatment. Any amount of added SiF4 will effect @an improvement in the catalytic acid function of the catalyst, land hence ony suchamounts are contemplated. It is preferred however to add suffi'50 cient SiF4 to sattirate the calcined gels, and this can be controlled by simply passing SiF4 over the catalyst at stibstantially aiiy desired -teinperatures, e.g., from 0 'to 800' F., and continuin.- such treatment until no more water is evolved, and SiF4 begins to appear in the off55 gases. Preferably, elevated temperatures of e.g., about 400' to 800' F. are emoloyed during the addition of SiF@ in order to lassist in desorbing water formed during the reaction. If desired, an in-,rt -sweep gas such as nitrogen may be admixed w.,,th the SiF4 in ord-@r to assist in 60 the renloval of water vapor. Atmospheric pressures are ordiparily en-lployed di.@iing the SiF4 addition, but either subatmospheric or superatmosplieric pressures are contan-iplated. The final cotalysts, afler the SiF4 treatment, will be found to have absorbed usually between about 65 O.IcYo iand 209'o by weight of SiF4, and preferably bet-,veen about I% and IO %. The SiI-4 may be added to the catalyst prior to use, or it may be iadded during use in the hydrocracking process by simply adchng SiF4 to the feed or the hydrogen. 70 In either case, when the activity of the catalyst declines to an uri-desirable degree, i-t may be rejuvenated for substantial periods of time by inter.-nittent or continues addition of SiF4 to the feed gases. It is also contempl,)ted that limited amoun@ts of wa@ter 75 rr@cty be used alon.- with the Si'@'@'4 to -@naintain bigh activity,
[3]5 The :aniount of water may be very low (e.g., 1-20 parts por niillion of the feed) or it may be as h@igh as,about 20 theoretica,l parts based on thereaction: 3SiF4+2H20->ZH2SiF6+SiO2 Thus, a-t 100 parts per million,of SiF4 -in the feed, up to abou,t 200 parts per n-lillion of water (or the equivalent aMOUn@t Of C02, and ialcohol, etc.) may be used. ,Inste-ad of adding SiF4 in the gas phase, it may also be added by iniprognation in the form of an iaqueous solution of fluosilicic acid, H2SiF6. Here again, it is p,referred ito add ithe fluosilicic acid to the final calcined ca,talyst, after laddition of the hyclrogenating meatl, but the reverse order of addition is also contemplated. In genar,al,;aqueous impregna-tion with H2SiF6 gives catalysts of lower aotivi@tythan the catalysts prepared by treatment wi,t,h gaseous SiF4, @and the latter is hence preferred. Exempla,ry catalysts con-templated herein include the following, the proportions being by weight: (1) 80% AIPOI, 10% M'003,3% CoO, 7% SiF, (2) 50% ALPO,, 40% Zr,(PO4)4, 5% Ni, 5% SiF4 (3) 80% A12(OH),PO,, 15% Ni, 5% SiF4 (4) 80% AI(PO,)PO(OH),, 15% Ni, 5% SiF, (5) 85% Ti3(PO4)4, 10% Ni, 5% SiF, (6) 60% AIP04, 30% CrPO4, 10% SiF4 (7) 60% AIPO,, 35% Fe,(PO,),, 5% SiF, (8) 50% AIP04, 45 % C03 (POI) 1, 5 % SiF4 (9) 40% Zrl(PO4)4,40% Ti3(PO4)4,15% Ni, 5% SiF, Many other catalysst of a similar nature can also be atilized. The oatalysts of this invention may be employed for thehydrocracking of substantially any nuneral oil fraction boiling above ithe convent-ional gasoline range, i.e. abo,,,e,abou,t 300' F., @and usually above )about 400' F. : ,and havin.- an end-boiling point up to about 1,000' F., but preferably not greater than @about 850' F. The-se feedstocks may be sulfur-free, or @they may contain up ,to about 5% by Nveight of sulfur, in the from of organic sulfur compounds. If it is desired t@o maintain the oatalyst in,a comple@tely sulfided staite,- feedstocks containing between iabout 0.01% and 5% by weight of sulfur may be used, or ia small propor-tion of H2S may be recircula'Led in the @recycle gas. Specific feedstocks con,templated comprise s@traight-run gas oils and heavy naphthas, coker distillate gas oils and heavy naphthas,- deasphal.ted crude oils, cycle oils derived from catalytic or thermal cracking operations, and the like. T-bese feedstocks may be derived from petroleum crude oils, shale oils, t-,,r sand oils, coalhydrogenat-1,Dn and the like. Specifically, it is preferred to employ oils having an -Api gravity between about 20' ;and 35', and containing at least about 30% by volume of acid soluble components (aromait-ics plus olefins). Hydrocracking conditions to be employed herein fall withiii -the follow-ing ranges: Table I Operative Preferred Temperatute, I F ------------------------- 400-800 450-700 i.g --------------------------- 600-5,000 750-2,500 Pre'S reiip s.e.f./bbl ---------------------- 1,000-15,ooo 2,000-10,000 1121@ilura o's' LHSV ------------------------------------ 0.1-10 0.5-5 The lower temperature ranges from about 400' to 600' F.,are normally desirable for the treatment of highboiling feedstocks, for example those having an end-poin-t above about 700' F. Those skilled in the art will understand -that the combination of conditions selected @noiild be correlated with the pirticular feedstock and oatalyst used, to obtain the desired conversion per pass, normally between abou-t 20% iand 70% by volume of the fed. Ordinarily, about 500 to 3,000 sc.f. of hydrogen per barrel of gasoline produced is consumed dun,ng -the hydro3,088,908 6 cracking. "Conversion" is measured interms of volumes of original feed converted pe@r volumedf feed processed, times 100. The catalysts of this invention may also be employed for lother -acid-cat-alyzed reactions, e.g., hydroisomerization, @alkylation, de,alkylation, disproportioiaation, polymerization, carbonylation, etc. . The folloxving examples are cited to illtistrate the invention iand @the results obtainable, but axe not to be 10 construed as liniiting in scope: EXAMPLE I NON-PILUORliNATED CATALYSTS A. A catalyst base comprising about 50% by weight of AlPO4 and 50% of A1203 was prepated by homoge15 neous precipitation of the hydrous cogel from an aqueous solution of a-luminum nitrate and phosphoric acid by hydrolysis of added urea at 80'-100' C. The resulting gel was dried at 500' F. to decompose the ammonium 20 nitrate and excess urea, then pelleted and calcined at 600' C. for 16 hours. The calcined pellets were impregnated with aqueous nickel nitrate solution to give about 10% iiietallic nickel on a dry basis, then calcined and reduced in hydrogen. The resul-ting catalyst was tested for hydrocracking of a hydrogenated gas oil having the following 25 properties: Gravity, I API --------------------------- 39.2 Boiling range, ' F. (Engler) ---------------- 436-536 Nitrogen, wt. percent ---------------------- 0.0001 30 Acid solubility, vol percent ----------------- 18 Conditions of the test runs were as follows: P-ressure, p.s.i.g ------------- --------------- i,ooo Temperature, ' F--------------------- 650 and 700 35 LHSV ----------------- ------------------ 2.0 il2/oil, s.c.f./bbl - --------------------- ----- 10,000 The catalyst was presulfided with feed containin.,@ 10% sulfur (as thiophene) and tested with 0.1% sulfur added to the above feed. 40 Essentially zero conversion was obtained at the 6501 and 700' F. temperature levels, thus demonstrating that -the catalyst without added SiF,, is essentially inactive for hydrocracking at low temperatures. B. Another catalyst base containing 75% AIPO,4 and 45 25% A1203 was prepared in the same manner and impregnated with the same amount of nickel. Tested under the same conditions (700' F.), this catalyst was also completely inactive. EXAMPLE II 50 Sir-i-TRr,,ATED CATALYSTS A catalyst having the saine composition as that of Example I-B was pretreated with 35 cubic feet of a gas mix@ture comprising 0.06 mole-percent of SiF4 -and 99.94 . mol - percent of nitrogen. The pretreatmen@t was carried 55 e out at 625' F. over a period of about 4 hours after reduction of the catalyst with hydrogen for 6 hours at 700' F. Both reduction and pretreatment were at atmospheric pressure. The quantity of SiF4 passed over the catalyst 60 corresponded approxiinately to 1.3 weight-percent of:ffuorilie based on the dry catalyst. The pretreated catalyst was tested at 625' F. and 1,500 P.S.i.g., using as feed a 738' F. endpoint hydrogenated gas oil derived from an atomatic catalytic cycle oil. Space 65 velocity was 1.0 and the hydrogen/oil ratio was 8,000 s.e.f./bbl. Complete (100%) conversion of the feed to light gasoline boiling below 270' F. was obtained in a single pass through the SiF4-pretreated catalyst. This startling re70 @;sult clearly demonstrates the very high degree of activity Tesulting from the addition of very small amounts of SiF4 to AIP04-AI203 catalysts. A 50-60% conversion to 400' F. endpoint -gasoline would be obtained at temperatures as low as 500' F. 75 When other hydrocracking catalysts within the purview
[4]7 of this invention are substituted in the foregoing example, igenerafly shnilar results are zobtained, with respect to the effect of silicon tetrafluoride upon catalyst activity. It is therefore not intended that the invention should be Iiinited to the details described above since many variations may be made by those skilled in the art without departing from the scope or spirit of the following claims. I
