Abstract:
A catalytic cracking catalyst comprising zeolite, kaolin, alumina and/or silica, antimony and 100-5,000 wt. ppm Ni is disclosed. The Ni-antimony interact in the environment of a fluidized catalytic cracking reactor to increase the magnetic susceptibility of the catalyst, permitting removal of nickel contaminated catalyst by magnetic separation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Division of prior, application Ser. No. 08/804,856, filed Feb. 24, 1997 now U.S. Pat. No. 5,972,201, Hydrocarbon Conversion Catalyst Additives and Processes, issued Oct. 26, 1999, which is a continuation of prior, application Ser. No., 08/372,747, filed Jan. 13, 1995, now abandoned. 
    
    
     BACKGROUND OF INVENTION 
     I. Field of the Invention 
     The present invention relates to compositions for fluid catalytic cracking processes. 
     II. Description of the Prior Art 
     In an FCC process, metals accumulate onto the catalyst, the catalyst becomes deactivated with time and in order to maintain FCC unit activity, a fraction of the unit inventory is withdrawn and fresh catalyst is added. The spent catalyst (withdrawn catalyst) contains a dynamic mixture of catalyst particles from very old/high metals, low activity to newer/low metals high activity. 
     Antimony has frequently been added to cracking catalyst to “passivate” the catalyst and reduce the production of hydrogen and other undesirable light gaseous products, e.g., in U.S. Pat. Nos. 4,459,366, 4,457,693, 3,711,422, and 4,334,979. 
     Magnetic separation has been taught by a number of U.S. patents such as U.S. Pat. Nos. 4,406,773, 5,147,527, 5,106,486, 5,171,424, and 5,230,869 to Hettinger et al., which teaches the removal of inactive catalyst and sorbents from mixtures of active and inactive particulates so that the active particulates can be recovered for reuse. 
     However, it has not been previously taught that the passivating advantage of antimony on conversion on catalyst and sorbents can be coupled with the enhanced magnetic susceptible of metals to obtain the advantages of passivation and selective recovery of more active particulate. 
     SUMMARY OF THE INVENTION 
     I. General Statement of the Invention 
     Accordingly, the present invention provides a catalytic cracking catalyst comprising zeolite, kaolin, alumina and/or silica and 0.1-10 wt. % antimony [and 0.005-15wt. % antimony] and 100-5,000 wt. Ppm Ni, on an elemental metal basis. 
     Particularly preferred is a process as described above wherein at least a portion of the particulates in the mixture comprises iron, the combination of antimony plus iron having been found to have synergistic magnetic properties according to the discovery of the invention. 
     Also particularly preferred is a process in which at least a portion of the antimony is added by mixing in the feed so as to cause said antimony to deposit gradually over time onto the catalyst. (Sorbent may also be used according to the techniques of U.S. Pat. No. 4,237,312 in place of catalyst or intermixed with catalyst.) 
     The antimony can be included in the particulate catalyst or sorbent during the manufacture of the particulate; e.g. by compounding it, or by ion exchanging onto the surface of the catalyst, or dipping the catalyst into a solution or suspension of antimony compounds during manufacture of the catalyst or sorbent. 
     The invention is preferred for situations where the particulates are a high valued specialty catalyst or additive which it is desired to recover for recycle. 
     The invention embodies a system for the conversion of a metal containing hydrocarbon feed into lower molecular weight products comprising in combination: a) a source of antimony-containing moiety decomposable under FCC conditions; b) a contacting zone wherein said feed can be contacted with catalyst for hydrocarbon conversion purposes; c) a hydrocarbon feed which gradually exhausts the activity of said catalyst, over repeated contacts with said hydrocarbon feed; and d) a magnetic separator operably connected to separate at least a portion of said particulates after contact with said feed; said separators separating said particulates into at least a portion having a magnetic susceptibility greater than the average aforesaid mixture and at least a second portion having a magnetic susceptibility lower than the average aforesaid mixture. 
     Particularly preferred are compositions of matter comprising with one or more of zeolite, kaolin, alumina and/or silica and 0.1-10 wt. % antimony suitable for cracking hydrocarbon feedstocks containing nickel and/or iron. 
     Sb Compounds 
     Sb can be added to feed in the form of antimony acetate (a commercial 97% composition, is available); Nalco colloidal antimony compositions available from Nalco Chemical Co.; antimony pentoxide and the other antimony compounds described in the various patents of Phillips Petroleum Company; and any other compound of antimony which does not deleteriously affect the cracking process or the magnetic separation. 
     Sb Addition 
     As described above, the antimony can be impregnated into the catalyst during its manufacture, can be ion exchanged onto the surface of the catalyst before use, can be dipped or otherwise coated onto the surface before use, or can otherwise be present in virgin catalyst as it is introduced into the FCC or RCC cracking system. Amounts of antimony on catalyst are shown in Table III. The invention is useful with a wide variety of conventional catalyst and sorbents used for hydrocarbon conversion. 
     Antimony can be incorporated into a catalyst during manufacture in order to “tag” that particular catalyst. This is especially important when attempting to separate out and recover a particularly valuable catalyst, e.g. a ZSM-5 or other specialty catalyst or catalyst additive, as in U.S. Pat. No. 5,538,624. For example, if the ZSM-5 contains substantial amounts of catalyst, and if nickel accumulates along with iron on the surface of the catalyst during repeated cracking cycles, that ZSM-5-containing catalyst can readily be recovered by magnetic separation because of the high magnetic susceptibility imparted by the presence of all three metals in combination. 
     Alternatively, the Sb can be injected into the feed continuously or periodically or can be injected into the hot catalyst return line, or the recycle line from the magnetic separator back to the FCC unit. 
     Magnetic Separation 
     The magnetic separator can be of the HGMS type (high gradient magnetic separator), the RERMS type (rare earth roller magnetic separator), or other permanent magnet type, or electromagnetic magnets installed in roller-type magnetic separators, or can be of the electrostatic variety, as described in the text by Svoboda entitled  Magnetic Methods for the Treatment of Minerals.    
     II. Utility of the Invention 
     The present invention is useful for a wide variety of hydrocarbon conversion processes including, without limitation, fluid catalytic cracking, the RCC heavy oil conversion process, hydrotreating, catalytic reforming, and various sorbent processes such as the MRS™ process of Ashland Oil, Inc. The invention permits the separation of a high activity sorbent or catalyst or other particulate portion from a mixture comprising spent particles and active particles. The active portion can be recycled back to a contactor for contact with additional quantities of hydrocarbon feeds to be converted. Also, the invention permits the preferential removal of particularly high value or particularly specialized particles which have been added to a particle mixture for optimum conversion of the hydrocarbon feed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates the magnetic susceptibility (X g ×10 −6  emu/g) and demonstrates the discovery of the invention that magnetic susceptibility is most increased by iron plus nickel, together with antimony. 
     FIG. 2 is comparative and indicates that nickel, vanadium and iron each greatly increase the magnetic susceptibility as they accumulate on the catalyst particles. 
     FIG. 3 is a bar graph again versus magnetic susceptibility where iron is 4200 ppm on each of the two samples, and the left hand run has 0% antimony, whereas the right hand run has 0.34% antimony. Note particularly how a relatively small addition of antimony sharply increases magnetic susceptibility. 
     FIG. 4 shows the effect of antimony on nickel. As the amount of nickel content on the catalyst increases, magnetic susceptibility increases with the addition of antimony, yet the magnetic susceptibility increases slightly in the absence of antimony as the nickel content increases. 
     FIG. 5 shows how an extremely small amount of antimony sharply increases the magnetic susceptibility of the catalyst in which it is either contained, or on which it has become deposited. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     EXAMPLE 1 
     (The Invention Adding Sb to Hydrocarbon FCC Feed so that it Deposits on to the Catalyst Over Time) 
     A commercial catalyst, FOC90, available from Akzo Chemicals, Inc., a division of Akzo Nobel, is employed in a conventional fluid catalytic cracking unit (FCC) of a design by UOP, M. W. Kellogg, or other designer. The catalyst circulates successively through a riser into a recovery section and then into a regenerator where carbon is burned off by treatment with air and/or CO 2 . The decoked catalyst is then recycled back to the riser for contact with additional quantities of a heavy oil feedstock which contains approximately 10 ppm nickel plus 5 ppm iron. From this stream of catalyst, there is continuously or intermittently withdrawn a portion which is sent to a magnetic separator of the type described in U.S. Pat. No. 5,147,527. The magnetic separator operates conventionally and removes a high metal-contaminated portion of the catalyst before recycling the remaining lower metal catalyst back to the cracking cycle. 
     When a 1:1 ppm (weight) ratio of feed iron to antimony (as antimony acetate, 97% wt.) is added to the feed to the FCC, the antimony gradually deposits on the circulating catalyst so that the catalyst which was earliest added becomes the most magnetic, and newly added make-up catalyst is the least magnetic. Operating the same magnetic separator conventionally, causes a sharper recovery of new catalyst because the magnetic susceptibility of the nickel-iron-contaminated catalyst is sharply increased by the antimony depositing on the catalyst. The magnetic susceptibility of the newly added catalyst is virtually zero, whereas the magnetic susceptibility of the catalyst which has been in the unit for several months is approximately 1 to 200×10 −6  emu\g, giving a sharp difference on which the magnetic separator can operate to provide a separation between older and newer catalyst. 
     EXAMPLE 2 
     (The Invention Incorporating Sb into a High Value Specialty Catalyst Additive Particle During Manufacture) 
     ZSM-5 and similar catalysts are covered by a number of patents, e.g. U.S. Pat. Nos. 3,702,886; 4,229,424; 4,080,397; EP 94693B1; and 4,562,055, and is highly favored by the petroleum refining industry because it cracks hydrocarbon feedstocks in such a way as to produce higher octane gasoline. However, ZSM-5 costs approximately 2-4 times the cost of normal cracking catalyst conventionally used for FCC units. 
     Therefore, it is common practice to add some ZSM-5 particles along with a conventional product, e.g. FOC-90 or other conventional commercial catalyst. When withdrawing metal-contaminated catalyst, some of the ZSM-5 is removed and is conventionally landfilled or otherwise disposed of to waste. 
     By incorporating 0.01 to 15, more preferably 0.02 to 5, and most preferably 0.03 to 2% by wt. of antimony into the catalyst as it is made, a ZSM-5 catalyst can be “tagged” so that it separates preferentially from the conventional catalyst which does not contain substantial quantities of antimony. As the ZSM-5/antimony tagged catalyst circulates, it is successively contacted with hydrocarbon fuel, separated from the hydrocarbon products, sent through a conventional regenerator to remove carbon, and is separated out (a portion at a time) to a magnetic separator. The magnetic separator preferentially separates the high magnetic susceptibility ZSM-5 catalyst which has had its magnetic susceptibility enhanced by the presence of antimony together with contaminating nickel and iron from the metal-containing hydrocarbon feed. 
     Alternatively, or supplementally, the highest magnetic fraction from the separator can be further processed through the same or an additional magnetic separator to still further concentrate (beneficiate) the ZSM-5-containing catalyst. 
     Note that the common practice of adding antimony to FCC feedstocks can be conventionally combined with the invention, though it somewhat decreases the difference in magnetic susceptibility between the catalyst which was tagged with antimony during manufacture and that which was not because both will have some Sb deposited on their surface from the feedstock being cracked. 
     EXAMPLE 3 
     (Comparative; the Effect on Magnetic Susceptibility of the Presence of Iron Versus the Presence of Nickel) 
     Table 1 sets forth the magnetic susceptibility together with the parts per million of iron, nickel, and antimony for a series of different catalysts, all based on a commercially available petroleum cracking catalyst, FOC-90 manufactured by the Filtrol Division of Akzo Chemicals, Inc., a division of Akzo Nobel. 
     FIG. 1 plots these same results. 
     As can be readily seen, the Fe+FOC-90 (4) has a sharply increased magnetic susceptibility over Sb+FOC-90 (2). This increase is enhanced as the nickel increases (3 and 4). When even a lower amount of nickel is added with 600 ppm of antimony (7), the magnetic susceptibility is dramatically increased by a factor of over four. This is only slightly affected by tripling the amount of nickel on the catalyst (6). 
     Thus, a major discovery of the invention is that antimony together with nickel plus iron is enormously higher in magnetic susceptibility than iron or nickel alone. Thus, adding antimony, e.g. to a feed so that it deposits on a cracking catalyst gradually over time, can effectively sharpen the separation achieved by a magnetic separator operating on the catalyst. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Effect of Sb and Other Metals on Magnetic Susceptibility 
               
             
          
           
               
                   
                 Xg*10 −6 , 
                   
                 PPM 
                   
               
               
                 Sample 
                 emu/g 
                 Fe 
                 Ni 
                 Sb 
               
               
                   
               
               
                 Blank 1 FOC-90-Sb 
                 0.9 
                 4826 
                 0 
                 700 
               
               
                 Blank 2 Fe—FOC-90+ Sb 
                 1.9 
                 11200 
                 0 
                 490 
               
               
                 I. Feed FOC-90 
                 1.25 
                 4826 
                 0 
                 0 
               
               
                 II. Fe—FOC-90 
                 2.2 
                 11200 
                 0 
                 0 
               
               
                 III. Fe + Ni (1000) 
                 4.2 
                 11200 
                 1200 
                 0 
               
               
                 IV. Fe + Ni (3000) 
                 4.4 
                 11200 
                 3600 
                 0 
               
               
                 V. Fe + Ni (1000) + Sb 
                 17.96 
                 11200 
                 1200 
                 600 
               
               
                 VI. Fe + Ni (3000) + Sb 
                 15.72 
                 11200 
                 3600 
                 1900 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE II 
               
             
             
               
                   
               
               
                 Effect of Antimony Upon Magnetic Susceptibility 
               
             
          
           
               
                 Octex 
                   
                   
                   
                 Magnetic Susceptibility 
               
               
                 Catalyst 
                 Nickel 
                 Iron 
                 Antimony 
                 X g  × 10 −6  emu/g 
               
               
                   
               
               
                 1 
                 — 
                 0.0042 
                 — 
                 2.89 
               
               
                 2 
                 — 
                 0.0042 
                 0.0054 
                 4.88 
               
               
                   
               
             
          
         
       
     
     Further evidence of such interaction between iron and antimony is evident in Table II. As can be seen, without antimony the magnetic susceptibility is at 2.89×10 −6  emu/g. Whereas with the addition of antimony, the magnetic susceptibility was increased by approximately 69%, thus demonstrating the applicability of this invention. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE III 
               
             
             
               
                   
               
               
                 Compositions (on catalyst particles) 
               
             
          
           
               
                   
                   
                   
                 More 
                 Most 
               
               
                 Parameter 
                 Units 
                 Preferred 
                 Preferred 
                 Preferred 
               
               
                   
               
               
                 Antimony 
                 % by wt. 
                 0.005-15 
                 0.02-5 
                 0.03-2 
               
               
                 Fe 
                 ppm wt 
                 10-25,000 
                 100-15,000 
                 1000-10,000 
               
               
                 Ni 
                 ppm wt 
                 10-15,000 
                 100-5000 
                 500-3000 
               
               
                 V 
                 ppm wt 
                 10-25,000 
                 100-10,000 
                 10000-5000 
               
               
                   
               
             
          
         
       
     
     All magnetic susceptibilities supported in this application were measured by Mathew-Johnson magnetic susceptibility balance according to techniques recited in U.S. Pat. No. 5,190,635 to Hettinger, col. 6, lines 8-16. 
     Modifications 
     Specific compositions, methods, or embodiments discussed are intended to be only illustrative of the invention disclosed by this specification. Variation on these compositions, methods, or embodiments are readily apparent to a person of skill in the art based upon the teachings of this specification and are therefore intended to be included as part of the inventions disclosed herein. While FOC-90 is used in the Examples, many other commercial catalysts can be used, e.g. Davison/Grace and/or Engelhard. 
     Reference to documents made in the specification is intended to result in such patents or literature being expressly incorporated herein by reference.