Abstract:
A process for slurry hydroprocessing, which involves preconditioning a slurry catalyst for activity improvement in vacuum residuum hydroprocessing units Preconditioning the slurry catalyst raises its temperature, thereby reducing shock on the catalyst slurry as it enters the hydroprocessing reactor.

Description:
FIELD OF THE INVENTION 
     A process for slurry hydroprocessing, which involves preconditioning a slurry catalyst for activity improvement in vacuum residuum hydroprocessing units. 
     BACKGROUND OF THE INVENTION 
     Slurry catalyst compositions, means for their preparation and their use in hydroprocessing of heavy feeds are known in the refining arts. Some examples are discussed below: 
     U.S. Pat. No. 4,710,486 discloses a process for the preparation of a dispersed Group VIB metal sulfide hydrocarbon oil hydroprocessing catalyst. Process steps include reacting aqueous ammonia and a Group VIB metal compound, such as molybdenum oxide or tungsten oxide, to form a water soluble oxygen-containing compound such as ammonium molybdate or tungstate. 
     U.S. Pat. No. 4,970,190 discloses a process for the preparation of a dispersed Group VIB metal sulfide catalyst for use in hydrocarbon oil hydroprocessing. This catalyst is promoted with a Group VIII Metal. Process steps include dissolving a Group VIB metal compound, such as molybdenum oxide or tungsten oxide, with ammonia to form a water soluble compound such as aqueous ammonium molybdate or ammonium tungstate. 
     Slurry hydroprocessing processes frequently operate at higher temperatures than those at which slurries comprising catalysts are synthesized and stored. For example, the slurry hydrocracking process of U.S. Publication No. 20060054533 typically operates at a temperature of at least 800° F., with a hydrogen pressure from about 1500 psi to about 3500 psi. The slurry catalysts generally enter the reactor (or initial reactor, if more than one) of the vacuum residuum hydroprocessing unit at a temperature around 450° F. and a hydrogen pressure of about 400 psi. This temperature and pressure differential shocks the highly active slurry catalyst and promotes the production of coke. Coke production decreases the efficiency of conversion by this catalyst. 
     SUMMARY OF THE INVENTION 
     This application discloses a process for slurry hydroprocessing, particularly slurry hydrocracking, in which the slurry catalyst is preconditioned prior to its entry into the reactor(s) of the vacuum residuum slurry hydroprocessing process. Preconditioning the slurry catalyst raises its temperature, thereby reducing shock on the catalyst slurry as it enters the hydroprocessing reactor. 
     The process of this invention is summarized as follows: 
     A process for the hydroprocessing of heavy oils, having at least one reaction stage, said process comprising the following steps:
         (a) contacting a hydrocarbon feed stream under slurry hydroprocessing conditions with a hydrogen stream and a stream comprising slurry hydroprocessing catalyst, in a vacuum residuum slurry hydroprocessing unit, and recovering a product stream along with a stream comprising spent slurry hydroprocessing catalyst and unconverted hydrocarbon feed:   (b) passing the stream comprising spent slurry hydroprocessing catalyst and unconverted hydrocarbon feed to a deoiling unit, where it is combined with a solvent, products and gases then being recovered, as well as a stream comprising spent slurry catalyst;   (c) passing the: stream comprising spent slurry catalyst to a metals recovery unit, where it is contacted with an ammonium leach solution in order to recover ammonium sulfate and compounds comprising Group VIII and Group VIB metals   (d) passing the compounds comprising Group VIII and Group VIB metals to a catalyst synthesis unit, where they are contacted with ammonia, hydrogen sulfide gas, hydrocarbon stream, hydrogen and a small amount of water to create an active slurry catalyst in oil, the oil comprising ammonium sulfate;   (e) passing the effluent of step (d) into a preconditioning unit in order to increase the temperature and reduce shock on the slurry catalyst, wherein the effluent is contacted with hydrogen and is decomposed into hydrogen sulfide and ammonia, streams which are removed from: the preconditioning unit;   (f) passing the effluent for step (e), which comprises the active slurry catalyst in oil to storage or to a vacuum residuum slurry hydroprocessing unit.       

    
    
     
       BRIEF DESCRIPTION OF THE FIGURE 
       The FIGURE illustrates the process disclosed in this invention for vacuum residuum slurry hydroprocessing using preconditioned slurry catalyst. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Stream  1 , which comprises hydrogen, enters the vacuum residuum slurry hydroprocessing unit (VRHU)  10 . Hydroprocessing processes which may be employed in this invention include hydrocracking, hydrotreating hydrodesulfurization, hydrodenitrification, and hydrodemetallization. Hydrocracking is the preferred process, however. Also entering VRHU  10  is a feed stream  2  (vacuum residuum is a common feed), hydrogen stream  3  and slurry catalyst stream  26  (which maybe admixed with Stream  3  comprising water). The slurry hydrocracking process typically operates at a temperature of at least 800° F., with a hydrogen pressure from about 1500 psi to about 3500 psi. The slurry catalysts following preconditioning, generally enters the reactor (or initial reactor, if more than one) of the vacuum residuum hydroprocessing unit at a temperature around 700° F. and a hydrogen pressure of about 2000 psi, 
     Products exit VRHU  10  through stream  55 . Stream  4 , the spent slurry catalyst stream comprising unconverted oil, enters a deoiling unit  20  where it is contacted by a solvent (stream  6 ) such as toluene or naphtha in order to remove products and gases (stream  5 ). Deoiling involves solid concentration and liquid removal, which may employ cross flow filtration, centrifugation, drying and quenching steps. 
     Stream  7  comprises deoiled spent slurry catalyst. Stream  7  enters the metals recovery unit (MRU  30 ). Enriched air enters the MRU  30  through stream  8 . Stream  9  is a solvent suitable for metals extraction, such as ketoxime. Through a series of solvent extractions and crystallization steps in MRU  30 , the metals from the oil stream are recovered, along with a byproduct of ammonium sulfate (stream  27 ). Vanadium is removed through stream  11  as V 2 O 5 . Spent metals extraction solvent is removed through stream  12  and wastewater is removed through stream  13 . 
     The Group VIII metal employed in the CASH process is often nickel. Nickel is recovered as a nickel sulfate stream (stream  14 ) and is passed to the catalyst synthesis unit (GSU  40 ). A portion of the nickel sulfate stream (stream  16 ) can be diverted to control the amount of nickel entering the catalyst synthesis unit (CSU  40 ). Recovered Group VI metals such as molybdenum, exit the MRU in stream  15 . If the metal is molybdenum, it is recovered as an ammonium dimolybdate stream (stream  15 ) which is passed to the catalyst synthesis unit (CSU  40 ). A light hydrocarbon or VGO (vacuum gas oil) (stream  17 ) enters into the catalyst synthesis unit (CSU  40 ) along with a small amount of water (stream  18 ). Stream  19  comprises hydrogen. 
     In the catalyst synthesis unit (CSU  40 ), conditions include a temperature in the range from 80° F. to 200° F., preferably in the range from 100° F. to 180° F., and most preferably in the range from 130° F. to 160° F. Pressure is in the range from 100 to 3000 psig, preferably in the range from 200 to 1000 psig, and most preferably from 300 to 500 psig. 
     The ingredients are mixed in the CSU  40  to form an active slurry catalyst in oil. A small amount of ammonium sulfate formed from the nickel sulfate and ammonia gas added to the CSU  40 , is also present in this stream. The small stream of water (stream  18 ) acts to keep the small amount of ammonium sulfate in solution. This prevents precipitation in the equipments. The active slurry catalyst in oil (stream  21 ) enters into a catalyst preconditioning unit (CPU  50 ). Hydrogen enters the CPU  50  through stream  24 . 
     The process conditions of the catalyst preconditioning unit (CPU  50 ) include temperature ranges from about 400° F. to about 1000° F., preferably from about 500° to about 800° F., and most preferably from about 600° F. to about 700° F. Pressure ranges from about 100 to about 3000 psi, preferably from 300 to about 2500 psi and more preferably from about 500 to about 2000 psi. The hydrogen rate is in the range from 2500 to 7500 scf/bbl, preferably from 500 to 6000 scf/bbl. Preconditioning of ammonium sulfate into hydrogen sulfide and ammonia requires about 2 hours. Residence time in the catalyst preconditioning unit (CPU) for the mixture comprising oil, slurry and ammonium sulfate is from 1.5 to three hours, preferably about 2 hours. 
     For every mole of hydrogen sulfide gas produced in the catalyst preconditioning unit (CPU  50 ) unit, 2 moles of ammonia are produced. 
     The CPU  50  is a continuously stirred tank reactor (CSTR or alternately, perfectly mixed reactor). This type of reactor is employed in order to prevent catalyst agglomeration. 
     The residuum feedstock  2  to the process of the present invention is generally a high boiling hydrocarbonaceous material having a normal boiling range mostly above 600° F. often having a normal boiling point range wherein at least 80% v/v of the feed boils between 600° F. and 1500° F., or between 800° F. and 1450° F. Residuum feedstocks usefully processed in the present invention may contain more than 500 ppm asphaltenes or 1000 ppm asphaltenes, and may contain as much as 10,000 ppm asphaltenes or more. The residuum feedstocks also usually contain more than 10 ppm metals and greater than 0.1% by weight sulfur, The metals are betieved to be present as organometallic compounds, but the concentrations of metals referred to herein are calculated as parts per million pure metal. The contaminating metals in the feed typically include nickel, vanadium and iron The sulfur is present as organic sulfur compounds and the wt % sulfur is calculated based on elemental sulfur. Typical feedstocks for the present invention include deasphalted residua or crude, crude oil atmospheric distillation column bottoms (reduced crude oil or atmospheric column residuum), or vacuum distillation column bottoms (vacuum residua). 
     EXAMPLE 
     Typical vacuum residuum feed properties are listed in the following table: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 API gravity at 60/60 
                 3.9 
               
               
                   
                 Sulfur (wt %) 
                 5.58 
               
               
                   
                 Nitrogen (ppm) 
                 5770 
               
               
                   
                 Nickel (ppm) 
                 93 
               
               
                   
                 Vanadium (ppm) 
                 243 
               
               
                   
                 Carbon (wt %) 
                 83.57 
               
               
                   
                 Hydrogen (wt %) 
                 10.04 
               
               
                   
                 MCRT (wt %) 
                 17.2 
               
               
                   
                 Viscosity @ 212° F. (cSt) 
                 3727 
               
               
                   
                 Pentane Asphaltenes (wt %) 
                 13.9 
               
               
                   
                 Fraction Boiling above 1050° F. (wt %) 
                 81 
               
               
                   
                   
               
             
          
         
       
     
     Typical process conditions used for heavy oil upgrading are listed as following: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Total pressure (psig) 
                 2500 
               
               
                   
                 Mo/Oil ratio (%) 
                 1.5 
               
               
                   
                 LHSV 
                 0.25 
               
               
                   
                 Reactor temperature (° F.) 
                 700-725° F. 
               
               
                   
                 H2 gas rate (SCF/B) 
                 7500 
               
               
                   
                   
               
             
          
         
       
     
     Two batches of slurry catalyst streams obtained as described above were sent to the vacuum residuum hydrocracking (VRHU) unit for use as catalysts The first batch was sent to the VRHU directly from the catalyst synthesis unit or from storage, without preliminary preconditioning. 
     The second batch was preconditioned in hydrogen as shown in the FIGURE prior to entering the VRHU. 
     Side by side comparison of VRHU performance results for conditioned slurry catalyst v. unconditioned slurry catalyst, are provided in the table below: 
     
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Without 
                 With 
               
               
                   
                 Preconditioning 
                 Preconditioning 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Hydrodenitrogenation: 
                 80.5% 
                 89.4% 
               
               
                   
                 Hydrodemetallization 
                 97.2 
                 98.6 
               
               
                   
                 Conversion of 1000 F. + 
                 96.5 
                 99.1 
               
               
                   
                 fraction 
               
               
                   
                 Conversion of 650 F. + 
                 69.8 
                 74.1 
               
               
                   
                 Fraction 
               
               
                   
                 Conversion of 800 F. + 
                 88.3 
                 91.8 
               
               
                   
                 Fraction 
               
               
                   
                   
               
             
          
         
       
     
     The improvement is approximately equivalent to increasing the fresh catalyst dosage to the VRHU by 30%.