Hydrofining process for hydrocarbon containing feed streams
This invention relates to a hydrofining process for hydrocarbon-containing feed streams. In one aspect, this invention relates to a process for removing metals from a hydrocarbon-containing feed stream. In another aspect, this invention relates to a process for removing sulfur or nitrogen from a hydrocarbon-containing feed stream. In still another aspect, this invention relates to a process for removing potentially cokeable components from a hydrocarbon-containing feed stream. In still another aspect, this invention relates to a process for reducing the amount of heavies in a hydrocarbon-containing feed stream. 
     It is well known that crude oil as well as products from extraction and/or liquefaction of coal and lignite, products from tar sands, products from shale oil and similar products may contain components which make processing difficult. As an example, when these hydrocarbon-containing feed streams contain metals such as vanadium, nickel and iron, such metals tend to concentrate in the heavier fractions such as the topped crude and residuum when these hydrocarbon-containing feed streams are fractionated. The presence of the metals make further processing of these heavier fractions difficult since the metals generally act as poisons for catalysts employed in processes such as catalytic cracking, hydrogenation or hydrodesulfurization. 
     The presence of other components such as sulfur and nitrogen is also considered detrimental to the processability of a hydrocarbon-containing feed stream. Also, hydrocarbon-containing feed streams may contain components (referred to as Ramsbottom carbon residue) which are easily converted to coke in processes such as catalytic cracking, hydrogenation or hydrodesulfurization. It is thus desirable to remove components such as sulfur and nitrogen and components which have a tendency to produce coke. 
     It is also desirable to reduce the amount of heavies in the heavier fractions such as the topped crude and residuum. As used herein the term heavies refers to the fraction having a boiling range higher than about 1000° F. This reduction results in the production of lighter components which are of higher value and which are more easily processed. 
     It is thus an object of this invention to provide a process to remove components such as metals, sulfur, nitrogen and Ramsbottom carbon residue from a hydrocarbon-containing feed stream and to reduce the amount of heavies in the hydrocarbon-containing feed stream (one or all of the described removals and reduction may be accomplished in such process, which is generally referred to as a hydrofining process, depending on the components contained in the hydrocarbon-containing feed stream). Such removal or reduction provides substantial benefits in the subsequent processing of the hydrocarbon-containing feed streams. 
     In accordance with the present invention, a hydrocarbon-containing feed stream, which also contains metals, sulfur, nitrogen and/or Ramsbottom carbon residue, is contacted with a solid catalyst composition comprising alumina, silica or silica-alumina. The catalyst composition also contains at least one metal selected from Group VIB, Group VIIB, and Group VIII of the Periodic Table, in the oxide or sulfide form. The reaction product of a mercaptoalcohol and a molybdenum compound selected from the group consisting of molybdic acids, alkali metal salts of molybdic acids and ammonium salts of molybdic acids (sometimes referred to hereinafter as &#34;Reaction Product&#34;) is mixed with the hydrocarbon-containing feed stream prior to contacting the hydrocarbon-containing feed stream with the catalyst composition. The hydrocarbon-containing feed stream, which also contains molybdenum, is contacted with the catalyst composition in the presence of hydrogen under suitable hydrofining conditions. After being contacted with the catalyst composition, the hydrocarbon-containing feed stream will contain a significantly reduced concentration of metals, sulfur, nitrogen and Ramsbottom carbon residue as well as a reduced amount of heavy hydrocarbon components. Removal of these components from the hydrocarbon-containing feed stream in this manner provides an improved processability of the hydrocarbon-containing feed stream in processes such as catalytic cracking, hydrogenation or further hydrodesulfurization. Use of the Reaction Product results in improved removal of metals. 
     The Reaction Product may be added when the catalyst composition is fresh or at any suitable time thereafter. As used herein, the term &#34;fresh catalyst&#34; refers to a catalyst which is new or which has been reactivated by known techniques. The activity of fresh catalyst will generally decline as a function of time if all conditions are maintained constant. It is believed that the introduction of the Reaction Product will slow the rate of decline from the time of introduction and in some cases will dramatically improve the activity of an at least partially spent or deactivated catalyst from the time of introduction. 
     For economic reasons it is sometimes desirable to practice the hydrofining process without the addition of the Reaction Product until the catalyst activity declines below an acceptable level. In some cases, the activity of the catalyst is maintained constant by increasing the process temperature. The reaction product is added after the activity of the catalyst has dropped to an unacceptable level and the temperature cannot be raised further without adverse consequences. It is believed that the addition of the Reaction Product at this point will result in a dramatic increase in catalyst activity. 
     Other objects and advantages of the invention will be apparent from the foregoing brief description of the invention and the appended claims as well as the detailed description of the invention which follows. 
     The catalyst composition used in the hydrofining process to remove metals, sulfur, nitrogen and Ramsbottom carbon residue and to reduce the concentration of heavies comprises a support and a promoter. The support comprises a refractory material selected from the group consisting of alumina, silica or silica-alumina. Suitable supports are believed to be Al 2  O 3 , SiO 2 , Al 2  O 3  --SiO 2 , Al 2  O 3  --TiO 2 , Al 2  O 3  --P 2  O 5 , Al 2  O 3  --BPO 4 , Al 2  O 3  --AlPO 4 , Al 2  O 3  --Zr 3  (PO 4 ) 4 , Al 2  O 3  --SnO 2  and Al 2  O 3  --ZnO. Of these supports, Al 2  O 3  is particularly preferred. 
     The promoter comprises at least one metal selected from the group consisting of the metals of Group VIB, Group VIIB, and Group VIII of the Periodic Table. The promoter will generally be present in the catalyst composition in the form of an oxide or sulfide. Particularly suitable promoters are iron, cobalt, nickel, tungsten, molybdenum, chromium, manganese, vanadium and platinum. Of these promoters, cobalt, nickel, molybdenum and tungsten are the most preferred. A particularly preferred catalyst composition is Al 2  O 3  promoted by CoO and MoO 3  or promoted by CoO, NiO and MoO 3 . 
     Generally, such catalysts are commercially available. The concentration of cobalt oxide in such catalysts is typically in the range of about 0.5 weight percent to about 10 weight percent based on the weight of the total catalyst composition. The concentration of molybdenum oxide is generally in the range of about 2 weight percent to about 25 weight percent based on the weight of the total catalyst composition. The concentration of nickel oxide in such catalysts is typically in the range of about 0.3 weight percent to about 10 weight percent based on the weight of the total catalyst composition. Pertinent properties of four commercial catalysts which are believed to be suitable are set forth in Table I. 
     
                       TABLE I                                                     
______________________________________                                    
                                         Sur-                             
                                  Bulk   face                             
         CoO      MoO      NiO    Density*                                
                                         Area                             
Catalyst (Wt. %)  (Wt. %)  (Wt. %)                                        
                                  (g/cc) (M.sup.2 /g)                     
______________________________________                                    
Shell 344                                                                 
         2.99      14.42   --     0.79   186                              
Katalco 477                                                               
         3.3      14.0     --      .64   236                              
KF - 165 4.6      13.9     --      .76   274                              
Commercial                                                                
         0.92      7.3     0.53   --     178                              
Catalyst D                                                                
Harshaw                                                                   
Chemical                                                                  
Company                                                                   
______________________________________                                    
 *Measured on 20/40 mesh particles, compacted.                            
 
    
     The catalyst composition can have any suitable surface area and pore volume. In general, the surface area will be in the range of about 2 to about 400 m 2  /g, preferably about 100 to about 300 m 2  /g, while the pore volume will be in the range of about 0.1 to about 4.0 cc/g, preferably about 0.3 to about 1.5 cc/g. 
     Presulfiding of the catalyst is preferred before the catalyst is initially used. Many presulfiding procedures are known and any conventional presulfiding procedure can be used. A preferred presulfiding procedure is the following two step procedure. 
     The catalyst is first treated with a mixture of hydrogen sulfide in hydrogen at a temperature in the range of about 175° C. to about 225° C., preferably about 205° C. The temperature in the catalyst composition will rise during this first presulfiding step and the first presulfiding step is continued until the temperature rise in the catalyst has substantially stopped or until hydrogen sulfide is detected in the effluent flowing from the reactor. The mixture of hydrogen sulfide and hydrogen preferably contains in the range of about 5 to about 20 percent hydrogen sulfide, preferably about 10 percent hydrogen sulfide. 
     The second step in the preferred presulfiding process consists of repeating the first step at a temperature in the range of about 350° C. to about 400° C., preferably about 370° C., for about 2-3 hours. It is noted that other mixtures containing hydrogen sulfide may be utilized to presulfide the catalyst. Also the use of hydrogen sulfide is not required. In a commercial operation, it is common to utilize a light naphtha containing sulfur to presulfide the catalyst. 
     As has been previously stated, the present invention may be practiced when the catalyst is fresh or the addition of the Reaction Product may be commenced when the catalyst has been partially deactivated. The addition of the Reaction Product may be delayed until the catalyst is considered spent. 
     In general, a &#34;spent catalyst&#34; refers to a catalyst which does not have sufficient activity to produce a product which will meet specifications, such as maximum permissible metals content, under available refinery conditions. For metals removal, a catalyst which removes less than about 50% of the metals contained in the feed is generally considered spent. 
     A spent catalyst is also sometimes defined in terms of metals loading (nickel+vanadium). The metals loading which can be tolerated by different catalyst varies but a catalyst whose weight has increased about 12% due to metals (nickel+vanadium) is generally considered a spent catalyst. 
     Any suitable hydrocarbon-containing feed stream may be hydrofined using the above described catalyst composition in accordance with the present invention. Suitable hydrocarbon-containing feed streams include petroleum products, coal, pyrolyzates, products from extraction and/or liquefaction of coal and lignite, products from tar sands, products from shale oil and similar products. Suitable hydrocarbon feed streams include gas oil having a boiling range from about 205° C. to about 538° C., topped crude having a boiling range in excess of about 343° C. and residuum. However, the present invention is particularly directed to heavy feed streams such as heavy topped crudes and residuum and other materials which are generally regarded as too heavy to be distilled. These materials will generally contain the highest concentrations of metals, sulfur, nitrogen and Ramsbottom carbon residues. 
     It is believed that the concentration of any metal in the hydrocarbon-containing feed stream can be reduced using the above described catalyst composition in accordance with the present invention. However, the present invention is particularly applicable to the removal of vanadium, nickel and iron. 
     The sulfur which can be removed using the above described catalyst composition in accordance with the present invention will generally be contained in organic sulfur compounds. Examples of such organic sulfur compounds include sulfides, disulfides, mercaptans, thiophenes, benzylthiophenes, dibenzylthiophenes, and the like. 
     The nitrogen which can be removed using the above described catalyst composition in accordance with the present invention will also generally be contained in organic nitrogen compounds. Examples of such organic nitrogen compounds include amines, diamines, pyridines, quinolines, porphyrins, benzoquinolines and the like. 
     While the above described catalyst composition is effective for removing some metals, sulfur, nitrogen and Ramsbottom carbon residue, the removal of metals can be significantly improved in accordance with the present invention by introducing the Reaction Product into the hydrocarbon-containing feed stream prior to contacting the hydrocarbon containing feed stream with the catalyst composition. As has been previously stated, the introduction of the Reaction Product may be commenced when the catalyst is new, partially deactivated or spent with a beneficial result occurring in each case. 
     Any suitable molybdenum compound selected from the group consisting of molybdic acids, alkali metal salts of molybdic acids and ammonium salts of molybdic acids may be used to form the Reaction Product. A preferred molybdic acid is H 2  MoO 4 . Examples of suitable alkali metal salts and suitable ammonium salts are Na 2  MoO 4 , (NH 4 ) 2  MoO 4 , (NH 4 ) 5  HMo 6  O 21 .xH 2  O, (NH 4 ) 4  H 2  MO 6  O 21 .5H 2  O; Na 5  HMo 6  O 21 .18H 2  O; Na 4  H 2  Mo 6  O 21 .13H 2  O; Na 3  H 3  Mo 6  O 21 .71/2H 2  O; (NH 4 ) 6  Mo 7  O 24 .4H 2  O; (NH 4 ) 4  Mo8O 26 .xH 2  O and (NH 4 ) 3  H 7  Mo 12  O 41 .xH 2  O. Ammonium salts are preferred over alkali metal salts because they react with mercaptoalcohols at higher rates. A preferred molybdenum compound for use in forming the Reaction Product is (NH 4 ) 6  Mo 7  O 24 .4H 2  O. 
     Any suitable mercaptoalcohol may be utilized to form the Reaction Product. An example of a suitable mercaptoalcohol is a mercaptoalcohol having the following generic formula: ##STR1## wherein R 1 , R 2 , R 3  and R 4  are independently selected from hydrogen or hydrocarbyl groups (alkyl, cycloalkyl, aryl, alkaryl, cycloalkaryl) having 1-20 (preferably 1-6) carbon atoms, n=1-10 (preferably 1-2), and m=1-10 (preferably 1-2). 
     Examples of suitable mercaptoalcohols are 2-mercaptoethanol, 1-mercapto-2-propanol, 1-mercapto-2-butanol, 3-mercapto-1-propanol, 1-mercapto-2-hexanol, 2-mercaptocyclohexanol, 2-mercaptocyclopentanol, 3-mercaptobicyclo[2.2.1]-heptane-2-ol, 1-mercapto-2-pentanol, 1-mercapto-2-phenyl-2-ethanol, 3-mercapto-3-phenyl-propane-1-ol, 2-mercapto-3-phenyl-propane-1-ol, thioglycerol 9-mercapto-10-hydroxyoctadecanoic acid, and 10-mercapto-9-hydroxyoctadecanoic acid. Preferred mercaptoalcohols are HS--CH 2  --CH 2  --OH(2-mercaptoethanol) and HS--CH 2  --C(C 6  H 5 )H--OH(1-mercapto-2-phenyl-2-ethanol). 
     The molybdenum compound and the mercaptoalcohol may be combined in any suitable manner and under any suitable reaction conditions. Preferably, the molybdenum compound is first suspended in the mercaptoalcohol or in a mixture of the mercaptoalcohol and any suitable solvent. An example of a suitable solvent is toluene. 
     The reaction may be carried out at any suitable temperature. The temperature will generally be in the range of about 20° C. to about 250° C. and will more preferably be in the range of about 80° C. to about 120° C. 
     The reaction may be carried out at any suitable pressure. The pressure will generally be in the range of about 0.1 atmosphere to about 100 atmospheres. A preferred pressure is about 1 atmosphere. 
     The molybdenum compound and mercaptoalcohol may be reacted for any suitable time. The reaction time will generally be in the range of about 0.1 hour to about 48 hours and will more preferably be in the range of about 0.5 hour to about 3 hours. The completion of the reaction can be observed by a dark red-brown color of the reaction mixture and the disappearance of the suspended molybdenum compound. 
     Water will form during the reaction. This water may be removed if desired or left in the reaction mixture. 
     If desired, an excess of the mercaptoalcohol can be used as a diluent in the reaction. 
     The Reaction Product will be liquid in form. If a solvent is not used, the reaction product may be used directly as an additive. However, if a solvent is used, it is desirable to evaporate the solvent prior to use of the Reaction Product. 
     The Reaction Product may be filtered to remove any residual solids or it may be used without filtration. 
     It is believed that the Reaction Product is a molybdenum (VI) hydroxymercaptide. However, as will be more fully pointed out in the examples, the exact structure of the Reaction Product is not known. 
     Any suitable concentration of the Reaction Product may be added to the hydrocarbon-containing feed stream. In general, a sufficient quantity of the Reaction Product will be added to the hydrocarbon-containing feed stream to result in a concentration of molybdenum metal in the range of about 1 to about 60 ppm and more preferably in the range of about 2 to about 20 ppm. 
     High concentrations such as about 100 ppm and above should be avoided to prevent plugging of the reactor. It is noted that one of the particular advantages of the present invention is the very small concentrations of molybdenum which result in a significant improvement. This substantially improves the economic viability of the process. 
     After the Reaction Product has been added to the hydrocarbon-containing feed stream for a period of time, it is believed that only periodic introduction of the Reaction Product is required to maintain the efficiency of the process. 
     The Reaction Compound may be combined with the hydrocarbon-containing feed stream in any suitable manner. The Reaction Product may be mixed with the hydrocarbon-containing feed stream as a liquid directly or may be mixed in a suitable solvent (preferably an oil) prior to introduction into the hydrocarbon-containing feed stream. Any suitable mixing time may be used. However, it is believed that simply injecting the Reaction Product into the hydrocarbon-containing feed stream is sufficient. No special mixing equipment or mixing period are required. 
     The pressure and temperature at which the Reaction Mixture is introduced into the hydrocarbon-containing feed stream is not thought to be critical. However, a temperature below 450° C. is recommended. 
     The hydrofining process can be carried out by means of any apparatus whereby there is achieved a contact of the catalyst composition with the hydrocarbon containing feed stream and hydrogen under suitable hydrofining conditions. The hydrofining process is in no way limited to the use of a particular apparatus. The hydrofining process can be carried out using a fixed catalyst bed, fluidized catalyst bed or a moving catalyst bed. Presently preferred is a fixed catalyst bed. 
     Any suitable reaction time between the catalyst composition and the hydrocarbon-containing feed stream may be utilized. In general, the reaction time will range from about 0.1 hours to about 10 hours. Preferably, the reaction time will range from about 0.3 to about 5 hours. Thus, the flow rate of the hydrocarbon containing feed stream should be such that the time required for the passage of the mixture through the reactor (residence time) will preferably be in the range of about 0.3 to about 5 hours. This generally requires a liquid hourly space velocity (LHSV) in the range of about 0.10 to about 10 cc of oil per cc of catalyst per hour, preferably from about 0.2 to about 3.0 cc/cc/hr. 
     The hydrofining process can be carried out at any suitable temperature. The temperature will generally be in the range of about 250° C. to about 550° C. and will preferably be in the range of about 350° to about 450° C. Higher temperatures do improve the removal of metals but temperatures should not be utilized which will have adverse effects on the hydrocarbon-containing feed stream, such as coking, and also economic considerations must be taken into account. Lower temperatures can generally be used for lighter feeds. 
     Any suitable hydrogen pressure may be utilized in the hydrofining process. The reaction pressure will generally be in the range of about atmospheric to about 10,000 psig. Preferably, the pressure will be in the range of about 500 to about 3,000 psig. Higher pressures tend to reduce coke formation but operation at high pressure may have adverse economic consequences. 
     Any suitable quantity of hydrogen can be added to the hydrofining process. The quantity of hydrogen used to contact the hydrocarbon-containing feed stock will generally be in the range of about 100 to about 20,000 standard cubic feet per barrel of the hydrocarbon-containing feed stream and will more preferably be in the range of about 1,000 to about 6,000 standard cubic feet per barrel of the hydrocarbon-containing feed stream. 
     In general, the catalyst composition is utilized until a satisfactory level of metals removal fails to be achieved which is believed to result from the coating of the catalyst composition with the metals being removed. It is possible to remove the metals from the catalyst composition by certain leaching procedures but these procedures are expensive and it is generally contemplated that once the removal of metals falls below a desired level, the used catalyst will simply be replaced by a fresh catalyst. 
     The time in which the catalyst composition will maintain its activity for removal of metals will depend upon the metals concentration in the hydrocarbon-containing feed streams being treated. It is believed that the catalyst composition may be used for a period of time long enough to accumulate 10-200 weight percent of metals, mostly Ni, V, and Fe, based on the weight of the catalyst composition, from oils. 
     The following examples are presented in further illustration of the invention. 
    
    
     EXAMPLE I 
     In this example, the preparation of a first Reaction Product which is referred to as Mo-Mercaptide A is described. 
     1-mercapto-2-phenyl-2-ethanol was prepared from 1000 grams of styrene oxide, 567 grams of H 2  S and 10 mL of a 20 weight % NaOH solution in methanol. These reactants were pumped into a 1 gallon autoclave reactor and heated from 28° C. to 59° C. during a 1-hour period while the pressure rose from about 350 psig to about 500 psig. At the end of the 1-hour period an additional 20 mL of the NaOH in methanol solution was charged to the autoclave and the reaction mixture was reheated to about 60° C. (at 490 psig) during a 2 hour period. Thereafter, 50 mL of the NaOH/methanol solution was charged to the autoclave and the entire reaction mixture was heated to about 100° C. (at 490 psig) during a period of 50 minutes. Then 50 mL of methanol was added to the autoclave and heating at about 100° C. (400 psig) continued for about 1 hour. 1353 grams of the product, 1-mercapto-2-phenyl-2-ethanol, were recovered. 
     92.4 grams (0.6 mole) of 1-mercapto-2-phenyl-2-ethanol, 17 grams (0.1 mole Mo) of an ammonium molybdate (approximate chemical formula (NH 4 ) 6  Mo 7  O 24 .4H 2  O, containing about 85 weight % MoO 3  ; marketed as &#34;molybdic acid&#34; by Mallinckrodt, Inc., St. Louis, MO), and 50 mL of toluene were charged to a 300 mL 3-neck flask equipped with magnetic stirrer, Dean-Start trap and reflux condenser. The stirred reaction mixture was heated to 90° C. and kept at this temperature for about 30 minutes. The mixture was then brought to reflux and water was removed as the azeotrope. The formed dark-brown solution was cooled to about 60° C., vacuum-filtered with added filter aid and analyzed. The solution contained about 1.5 weight % Mo (determined by plasma analysis). The main reaction product (Mo-Mercaptide A) is believed to be molybdenum (VI) hydroxymercaptide, Mo(S--CH 2  --CHPh--OH) 6 , as judged from the IR spectrum of a related product, prepared from β -mercaptoethanol and ammonium molybdate (see Example II), which showed an OH absorption band but no SH absorption band. 
     EXAMPLE II 
     This example illustrates the preparation of a second Reaction Product prepared by reaction of 169 grams (1.0 mole Mo) of ammonium molybdate (same as Example I) and about 468 grams (6 moles) of β-mercaptoethanol (prepared in the Philtex Plant of Phillips Petroleum Company, Phillips, TX) in a 1-liter reactor. N 2  was sparged through the reaction mixture, while it was heated to about 115° C., so as to remove formed H 2  O (48 mL distillate was collected). The non-volatilized liquid product was cooled and analyzed by IR spectrometry. It showed a strong OH absorption band but no SH absorption band (2500 cm -1 ). The Mo content was about 17 weight %. It is believed that the formula of the formed product is Mo(S--CH 2  --CH 2  --OH) 6 . This Reaction Product is referred to as Mo-Mercaptide B. 
     EXAMPLE III 
     In this example, the automated experimental setup for investigating the hydrofining of heavy oils in accordance with the present invention is described. Oil, with or without a dissolved decomposable molybdenum compound, was pumped downward through an induction tube into a trickle bed reactor, 28.5 inches long and 0.75 inches in diameter. The oil pump used was a Whitey Model LP 10 (a reciprocating pump with a diaphragm-sealed head; marketed by Whitey Corp., Highland Heights, Ohio). The oil induction tube extended into a catalyst bed (located about 3.5 inches below the reactor top) comprising a top layer of 40 cc of low surface area α-alumina (14 grit Alundum; surface area less than 1 m 2  /gram; marketed by Norton Chemical Process Products, Akron, Ohio), a middle layer of 33.3 cc of a hydrofining catalyst mixed with 85 cc of 36 grit Alundum and a bottom layer of 50 cc of α-alumina. 
     The hydrofining catalyst used was a commercial, promoted desulfurization catalyst (referred to as catalyst D in table I) marketed by Harshaw Chemical Company, Beachwood, Ohio. The catalyst had an Al 2  O 3  support having a surface area of 178 m 2  /g (determined by BET method using N 2  gas), a medium pore diameter of 140 Å and at total pore volume of 0.682 cc/g (both determined by mercury porosimetry in accordance with the procedure described by American Instrument Company, Silver Springs, Md., catalog number 5-7125-13. The catalyst contained 0.92 weight-% Co (as cobalt oxide), 0.53 weight-% Ni (as nickel oxide); 7.3 weight-% Mo (as molybdenum oxide). 
     The catalyst was presulfided as follows. A heated tube reactor was filled with a 4 inch high bottom layer of Alundum, a 17-18 inch high middle layer of catalyst D, and a 5-6 inch top layer of Alundum. The reactor was purged with nitrogen and then the catalyst was heated for one hour in a hydrogen stream to about 400° F. While the reactor temperature was maintained at about 400° F., the catalyst was exposed to a mixture of hydrogen (0.46 scfm) and hydrogen sulfide (0.049 scfm) for about fourteen hours. The catalyst was then heated for about one hour in the mixture of hydrogen and hydrogen sulfide to a temperature of about 700° F. The reactor temperature was then maintained at 700° F. for fourteen hours while the catalyst continued to be exposed to the mixture of hydrogen and hydrogen sulfide. The catalyst was then allowed to cool to ambient temperature conditions in the mixture of hydrogen and hydrogen sulfide and was finally purged with nitrogen. 
     Hydrogen gas was introduced into the reactor through a tube that concentrically surrounded the oil induction tube but extended only as far as the reactor top. The reactor was heated with a Thermcraft (Winston-Salem, N.C.) Model 211 3-zone furnace. The reactor temperature was measured in the catalyst bed at three different locations by three separate thermocouples embedded in an axial thermocouple well (0.25 inch outer diameter). The liquid product oil was generally collected every day for analysis. The hydrogen gas was vented. Vanadium and nickel contents were determined by plasma emission analysis; sulfur content was measured by X-ray fluorescence spectrometry; Ramsbottom carbon residue was determined in accordance with ASTM D524; pentane insolubles were measured in accordance with ASTM D893; and N content was measured in accordance with ASTM D3228. 
     The additives used were mixed in the feed by adding a desired amount to the oil and then shaking and stirring the mixture. The resulting mixture was supplied through the oil induction tube to the reactor when desired. 
     EXAMPLE IV 
     A desalted, topped (400° F.+) Hondo Californian heavy crude (density at 38.5° C.: 0.963 g/cc) was hydrotreated in accordance with the procedure described in Example III. The liquid hourly space velocity (LHSV) of the oil was about 1.5 cc/cc catalyst/hr; the hydrogen feed rate was about 4,800 standard cubic feet (SCF) of hydrogen per barrel of oil; the temperature was about 750° F.; and the pressure was about 2250 psig. The Reaction Product added to the feed in run 3 was Mo-Mercaptide B. The Reaction Product added to the feed in run 4 was Mo-mercaptide A. The molybdenum compound added to the feed in control run 2 was Mo(CO) 6  (marketed by Aldrich Chemical Company, Milwaukee, Wis.). Pertinent process conditions and demetallization results of two control runs and one invention run are summarized in Table II. 
     
                                           TABLE II                                
__________________________________________________________________________
                    PPM in Feed                                           
       Days on  Temp                                                      
                    Added          PPM in Product                         
                                            % Removal                     
Run    Stream                                                             
            LHSV                                                          
                (°F.)                                              
                    Mo  Ni V  Ni + V                                      
                                   Ni                                     
                                     V Ni + V                             
                                            of (Ni + V)                   
__________________________________________________________________________
 1     1    1.58                                                          
                750 0   103                                               
                           248                                            
                              351  30                                     
                                     54                                   
                                       84   76                            
(Control)                                                                 
       2    1.51                                                          
                750 0   103                                               
                           248                                            
                              351  34                                     
                                     59                                   
                                       93   74                            
No Additive                                                               
       3    1.51                                                          
                750 0   103                                               
                           248                                            
                              351  35                                     
                                     62                                   
                                       97   72                            
       4    1.51                                                          
                750 0   103                                               
                           248                                            
                              351  36                                     
                                     63                                   
                                       99   72                            
       5    1.49                                                          
                750 0   103                                               
                           248                                            
                              351  35                                     
                                     64                                   
                                       99   72                            
       6    1.55                                                          
                750 0   103                                               
                           248                                            
                              351  28                                     
                                     60                                   
                                       88   75                            
       7    1.53                                                          
                750 0   103                                               
                           248                                            
                              351  38                                     
                                     71                                   
                                       109  69                            
       9    1.68                                                          
                750 0   103                                               
                           248                                            
                              351  40                                     
                                     64                                   
                                       104  70                            
       10   1.53                                                          
                750 0   103                                               
                           248                                            
                              351  20                                     
                                     26                                   
                                       46   .sup. 87.sup.1                
       17   1.61                                                          
                750 0   103                                               
                           248                                            
                              351  49                                     
                                     98                                   
                                       147  .sup. 58.sup.1                
       18   1.53                                                          
                750 0   103                                               
                           248                                            
                              351  40                                     
                                     75                                   
                                       115  67                            
       19   1.53                                                          
                750 0   103                                               
                           248                                            
                              351  40                                     
                                     73                                   
                                       113  68                            
       20   1.57                                                          
                750 0   103                                               
                           248                                            
                              351  44                                     
                                     75                                   
                                       119  66                            
       21   1.45                                                          
                750 0   103                                               
                           248                                            
                              351  41                                     
                                     68                                   
                                       109  69                            
       22   1.49                                                          
                750 0   103                                               
                           248                                            
                              351  41                                     
                                     60                                   
                                       101  71                            
       24   1.47                                                          
                750 0   103                                               
                           248                                            
                              351  42                                     
                                     69                                   
                                       111  68                            
 2     1    1.56                                                          
                750 20  103                                               
                           248                                            
                              351  22                                     
                                     38                                   
                                       60   83                            
(Control)                                                                 
       1.5  1.56                                                          
                750 20  103                                               
                           248                                            
                              351  25                                     
                                     42                                   
                                       67   81                            
Mo(CO).sub.6                                                              
       2.5  1.46                                                          
                750 20  103                                               
                           248                                            
                              351  28                                     
                                     42                                   
                                       70   80                            
Added  3.5  1.47                                                          
                750 20  103                                               
                           248                                            
                              351  19                                     
                                     35                                   
                                       54   85                            
       6    1.56                                                          
                750 20  103                                               
                           248                                            
                              351  29                                     
                                     38                                   
                                       67   81                            
       7    1.55                                                          
                750 20  103                                               
                           248                                            
                              351  25                                     
                                     25                                   
                                       50   86                            
       8    1.50                                                          
                750 20  103                                               
                           248                                            
                              351  27                                     
                                     35                                   
                                       62   82                            
       9    1.53                                                          
                750 20  103                                               
                           248                                            
                              351  27                                     
                                     35                                   
                                       62   82                            
       10   1.47                                                          
                750 20  103                                               
                           248                                            
                              351  32                                     
                                     35                                   
                                       67   81                            
       11   1.47                                                          
                751 20  103                                               
                           248                                            
                              351  25                                     
                                     35                                   
                                       60   83                            
       12   1.42                                                          
                750 20  103                                               
                           248                                            
                              351  27                                     
                                     34                                   
                                       61   83                            
       13   1.47                                                          
                750 20  103                                               
                           248                                            
                              351  31                                     
                                     35                                   
                                       66   81                            
       14   1.56                                                          
                750 20  103                                               
                           248                                            
                              351  36                                     
                                     52                                   
                                       88   75                            
       15   1.56                                                          
                750 20  103                                               
                           248                                            
                              351  47                                     
                                     68                                   
                                       115  .sup. 67.sup.1                
 3     1    1.63                                                          
                750 3.4 111                                               
                           258                                            
                              369  29                                     
                                     42                                   
                                       71   81                            
(Invention)                                                               
       3    1.53                                                          
                750 3.4 111                                               
                           258                                            
                              369  27                                     
                                     43                                   
                                       70   81                            
Mo--   4    1.53                                                          
                750 3.4 111                                               
                           258                                            
                              369  31                                     
                                     51                                   
                                       82   78                            
Mercaptide                                                                
       6    1.58                                                          
                750 3.4 111                                               
                           258                                            
                              369  31                                     
                                     52                                   
                                       83   71                            
B      8    1.50                                                          
                750 3.4 111                                               
                           258                                            
                              369  36                                     
                                     58                                   
                                       94   75                            
       10   1.50                                                          
                748 3.4 111                                               
                           258                                            
                              369  33                                     
                                     54                                   
                                       87   76                            
       13   1.44                                                          
                748 3.8 109                                               
                           243                                            
                              352  31                                     
                                     49                                   
                                       80   77                            
       15   1.57                                                          
                750 3.8 109                                               
                           243                                            
                              352  36                                     
                                     61                                   
                                       97   72                            
       16   1.57                                                          
                750 3.8 109                                               
                           243                                            
                              352  35                                     
                                     60                                   
                                       95   73                            
       18   1.53                                                          
                750 3.8 109                                               
                           243                                            
                              352  36                                     
                                     61                                   
                                       97   72                            
       20   1.48                                                          
                750 3.8 109                                               
                           243                                            
                              352  37                                     
                                     63                                   
                                       100  72                            
 4     1    1.73                                                          
                750 3.8  95                                               
                           241                                            
                              336  25                                     
                                     56                                   
                                       81   76                            
(Invention)                                                               
       3    1.43                                                          
                750 3.8  95                                               
                           241                                            
                              336  23                                     
                                     47                                   
                                       70   79                            
Mo--   4    --  750 3.8  95                                               
                           241                                            
                              336  23                                     
                                     50                                   
                                       73   78                            
Mercaptide                                                                
       5    1.41                                                          
                750 3.8  95                                               
                           241                                            
                              336  28                                     
                                     56                                   
                                       84   75                            
A      7    1.47                                                          
                750 3.8  95                                               
                           241                                            
                              336  30                                     
                                     60                                   
                                       90   73                            
       8    --  750 3.8  95                                               
                           241                                            
                              336  29                                     
                                     60                                   
                                       89   74                            
       9    --  750 3.8  95                                               
                           241                                            
                              336  30                                     
                                     61                                   
                                       91   73                            
       10   1.56                                                          
                750 3.8  95                                               
                           241                                            
                              336  29                                     
                                     57                                   
                                       86   74                            
__________________________________________________________________________
 .sup.1 Results believed to be erroneus                                   
 
    
     Data in Table II show that the dissolved molybdenum hydroxy mercaptides were effective demetallizing agents (compare runs 3 and 4 with run 1), but not as effective as Mo(CO) 6  (run 2). 
     The removal of other undesirable impurities in the heavy oil in the first three runs is summarized in Table III. 
     
                       TABLE III                                                   
______________________________________                                    
         Run 1  Run 2    Run 3     Run 4                                  
         (Control)                                                        
                (Control)                                                 
                         (Invention)                                      
                                   (Invention)                            
______________________________________                                    
Wt % in Feed:                                                             
Sulfur     5.6      5.6      5.6     5.3                                  
Carbon Residue                                                            
           9.9      9.9      9.9     10.0                                 
Pentane Insol-                                                            
           13.4     13.4     13.4    13.1                                 
ubles                                                                     
Nitrogen    0.70     0.70     0.70    0.71                                
Wt % in Product:                                                          
Sulfur     1.5-3.0  1.3-2.0  1.4-2.0 1.2-1.5                              
Carbon Residue                                                            
           6.6-7.6  5.0-5.9  5.7-6.2 5.1                                  
Pentane Insol-                                                            
           4.9-6.3  4.3-6.7  3.8-6.1 3.4                                  
ubles                                                                     
Nitrogen   0.60-0.68                                                      
                    0.55-0.63                                             
                             0.54-0.62                                    
                                      0.54                                
% Removal of:                                                             
Sulfur     46-73    64-77    64-75   72-77                                
Carbon Residue                                                            
           23-33    40-49    37-42   49                                   
Pentane Insol-                                                            
           53-63    50-68    54-72   74                                   
ubles                                                                     
Nitrogen    3-14    10-21    11-23   26                                   
______________________________________                                    
 
    
     Data in Table III show that the removal of S, Ramsbottom carbon residue, pentane insolubles and nitrogen was consistently higher in runs 3 and 4 (with Mo-Mercaptides A and B) than in run 1 (with no added Mo). Mo-mercaptides and Mo(CO) 6  had approximately the same effectiveness in removing these impurities. 
     EXAMPLE V 
     An Arabian heavy crude (containing about 30 ppm nickel, 102 ppm vanadium, 4.17 wt % sulfur, 12.04 wt %, carbon residue, and 10.2 wt % pentane insolubles) was hydrotreated in accordance with the procedure described in Example I. The LHSV of the oil was 1.0, the pressure was 2250 psig, the hydrogen feed rate was 4,800 standard cubic feet hydrogen per barrel of oil, and the temperature was 765° F. (407° C.). The hydrofining catalyst was presulfided catalyst D. 
     In run 4, no molybdenum was added to the hydrocarbon feed. In run 5, molybdenum (IV) octoate was added for 19 days. Then molybdenum (IV) octoate, which had been heated at 635° F. for 4 hours in Monagas pipe line oil at a constant hydrogen pressure of 980 psig in a stirred autoclave, was added for 8 days. The results of run 4 are presented in Table IV and the results of run 5 in Table V. 
     
                       TABLE IV                                                    
______________________________________                                    
(Run 4)                                                                   
Days on                                                                   
       PPM Mo     PPM in Product Oil                                      
                                 % Removal                                
Stream in Feed    Ni    V     Ni + V of Ni + V                            
______________________________________                                    
 1     0          13    25    38     71                                   
 2     0          14    30    44     67                                   
 3     0          14    30    44     67                                   
 6     0          15    30    45     66                                   
 7     0          15    30    45     66                                   
 9     0          14    28    42     68                                   
10     0          14    27    41     69                                   
11     0          14    27    41     69                                   
13     0          14    28    42     68                                   
14     0          13    26    39     70                                   
15     0          14    28    42     68                                   
16     0          15    28    43     67                                   
19     0          13    28    41     69                                   
20     0          17    33    50     62                                   
21     0          14    28    42     68                                   
22     0          14    29    43     67                                   
23     0          14    28    42     68                                   
25     0          13    26    39     70                                   
26     0           9    19    28     79                                   
27     0          14    27    41     69                                   
29     0          13    26    39     70                                   
30     0          15    28    43     67                                   
31     0          15    28    43     67                                   
32     0          15    27    42     68                                   
______________________________________                                    
 
    
     
                       TABLE V                                                     
______________________________________                                    
(Run 5)                                                                   
Days on                                                                   
       PPM Mo     PPM in Product Oil                                      
                                 % Removal                                
Stream in Feed    Ni    V     Ni + V of Ni + V                            
______________________________________                                    
Mo (IV) octoate as Mo Source                                              
 3     23         16    29    45     66                                   
 4     23         16    28    44     67                                   
 7     23         13    25    38     71                                   
 8     23         14    27    41     69                                   
10     23         15    29    44     67                                   
12     23         15    26    41     69                                   
14     23         15    27    42     68                                   
16     23         15    29    44     67                                   
17     23         16    28    44     67                                   
20     Changed to hydro-treated Mo (IV) octoate                           
22     23         16    28    44     67                                   
24     23         17    30    47     64                                   
26     23         16    26    42     68                                   
28     23         16    28    44     67                                   
______________________________________                                    
 
    
     Referring now to Tables IV and V, it can be seen that the percent removal of nickel plus vanadium remained fairly constant. No improvements in metals, sulfur, carbon residue, and pentane insolubles removal was seen when untreated or hydro-treated molybdenum octoate was introduced in run 5. This demonstrates that not all decomposable molybdenum compounds provide a beneficial effect. 
     EXAMPLE VI 
     This example illustrates the rejuvenation of a substantially deactivated sulfided, promoted desulfurization catalyst (referred to as catalyst D in Table I) by the addition of a decomposable Mo compound to the feed, essentially in accordance with Example III except that the amount of Catalyst D was 10 cc. The feed was a supercritical Monagas oil extract containing about 29-35 ppm Ni, about 103-113 ppm V, about 3.0-3.2 weight-% S and about 5.0 weight-% Ramsbottom C. LHSV of the feed was about 5.0 cc/cc catalyst/hr; the pressure was about 2250 psig; the hydrogen feed rate was about 1000 SCF H 2  per barrel of oil; and the reactor temperature was about 775° F. (413° C.). During the first 600 hours on stream, no Mo was added to the feed; thereafter Mo(CO) 6  was added. Results are summarized in Table VI. 
     
                                           TABLE VI                                
__________________________________________________________________________
Feed                    Product                                           
Hours on                                                                  
     Added Ni  V   (Ni + V)                                               
                        Ni  V   (Ni + V)                                  
                                     % Removal                            
Stream                                                                    
     Mo (ppm)                                                             
           (ppm)                                                          
               (ppm)                                                      
                   (ppm)                                                  
                        (ppm)                                             
                            (ppm)                                         
                                (ppm)                                     
                                     of (Ni + V)                          
__________________________________________________________________________
 46  0     35  110 145   7  22  29   80                                   
 94  0     35  110 145   8  27  35   76                                   
118  0     35  110 145  10  32  42   71                                   
166  0     35  110 145  12  39  51   65                                   
190  0     32  113 145  14  46  60   59                                   
238  0     32  113 145  17  60  77   47                                   
299  0     32  113 145  22  79  101  30                                   
377  0     32  113 145  20  72  92   37                                   
430  0     32  113 145  21  74  95   34                                   
556  0     29  108 137  23  82  105  23                                   
586  0     29  108 137  24  84  108  21                                   
646  15    29  103 132  22  72  94   29                                   
676  15    29  103 132  20  70  90   32                                   
682  29    28  101 129  18  62  80   38                                   
706  29    28  101 129  16  56  72   44                                   
712  29    28  101 129  16  50  66   49                                   
736  29    28  101 129   9  27  36   72                                   
742  29    28  101 129   7  22  29   78                                   
766  29    28  101 129   5  12  17   87                                   
__________________________________________________________________________
 
    
     Data in Table VI show that the demetallization activity of a substantially deactivated catalyst (removal of Ni+V after 586 hours: 21%) was dramatically increased (to about 87% removal of Ni+V) by the addition of Mo(CO) 6  for about 120 hours. At the time when the Mo addition commenced, the deactivated catalyst had a metal (Ni+V) loading of about 34 weight-% (i.e., the weight of the fresh catalyst had increased by 34% due to the accumulation of metals). At the conclusion of the test run, the metal (Ni+V) loading was about 44 weight-%. Sulfur removal was not significantly affected by the addition of Mo. Based on these results, it is believed that the addition of the Reaction Products (such as those prepared in accordance with the procedures of Examples I and II) to the feed would also be beneficial in enhancing the demetallization activity of substantially deactivated catalysts. 
     Reasonable variations and modifications are possible within the scope of the disclosure and the appended claims to the invention.