Patent Publication Number: US-5290428-A

Title: Superacid catalyzed hydrocracking of heavy oils and bitumens

Description:
FIELD OF THE INVENTION 
     This invention relates to a process for the catalyzed hydrocracking of heavy hydrocarbons into a refinery treatable product. 
     BACKGROUND OF THE INVENTION 
     Hydrogenation processes for the upgrading of heavy cretaceons crude oil and bitumens are well known. Upgrading processes are normally carried out to remove or reduce the contaminants in the oil and to convert the heavier components of the oil into lower boiling point hydrocarbon products. The contaminants include the heteroatoms oxygen, sulphur and nitrogen and the metals vanadium, nickel and iron. 
     Current commercial upgrading processes typically involve the use of a heterogeneous catalyst, exemplary of which would be cobalt, molybdenum or nickel sulfides deposited on an alumina substrate. Deleteriously, the higher molecular weight components of the heavy oils tend to accumulate on the catalyst pellet surfaces, clogging the pore system and thus reducing the rate of hydrogenation. Ultimately, the deposition of coke and metals on the pellet surface will despoil the catalytic performance. This becomes a serious operational problem when feedstocks such as bitumen, which are high in asphaltenes are hydrocracked. 
     The types of reactor employed in hydrocracking processes typically comprise a tubular reactor containing a fixed bed of the catalysts mentioned supra, or a fluidized bed of catalyst. Recovery of spent catalyst, and indeed replacement thereof, is a major expenditure in the process. 
     Typical hydrocracking reaction conditions are undertaken at high temperatures, of the order of between 400°-840° C. and at high pressures namely about 2,000-3,000 psi or higher. 
     It would be desirable, therefore, if a process not requiring a solid catalyst and requiring less severe reaction conditions could be arrived at. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention there is provided a process for hydrocracking a heavy hydrocarbon to produce lower boiling point distillates. More specifically, the process involves reacting the feedstock with a gaseous superacid in the presence of hydrogen. 
     Preferably, addition of a hydrogen transfer agent to the reactants would be made. 
     Typical heavy hydrocarbon feedstocks would include heavy oil, bitumen or chemically related substances, for example, asphaltenes. 
     As the catalytic superacidic fluorine compound, acids which contain elements of group III, IV and/or V of the periodic table could be considered. Exemplary superacids would include, but are not limited to, HF.BF 3 , H 2  SiF 6  and HPF 6 . Preferably, the superacid utilized would comprise HF.BF 3 . 
     As stated earlier, it is a preferred condition that the hydrogenation reaction take place in the presence of a hydrogen transfer agent. Suitable hydrogen transfer agents would comprise the cycloalkanes and low molecular weight alkanes. Particularly suitable hydrogen transfer agents include methylcyclohexane (MeCH), methylcyclopentane, dimethylcyclohexane or dimethcyclopentane. The preferred hydrogen transfer agent would be methylcyclohexane. 
     Preferred conditions for the hydrogenation reaction are such that the reaction is conducted at temperatures ranging from between 25° C. and 300° C. A preferred temperature range would be between 170° C. and 250° C. It will be readily appreciated however, by one skilled in the art, that if the temperature is too low, no reaction takes place and if too high, molecular over-degradation will result. 
     The requisite reaction time would probably range between one to twenty four hours. However, there exists the possibility of instantaneous reaction, and thus the time is not to be restricted to this stated range. 
     Again, there is no criticality with respect to pressure. Typically, the HF.BF 3  pressure would be 500 psi. 
     As a result of practising the present process, the bitumen or heavy oil feedstock is rendered into lower boiling point distillates. Advantageously under the mild conditions of the process the bitumen is converted to volatiles in at least a 56% yield in one hour. Additionally, removal of the undesirable heteroatoms is effected. Furthermore, a reduction in the vanadium, nickel and iron content takes place. 
     Following the hydrogenation reaction, the superacid HF.BF 3  has to be removed prior to further processing of the reaction products and this is easily and inexpensively done because of the high volatility and solubility of the superacid in water. Thus, the catalyst is reusable without involving a complex regeneration technique. 
     The main facets of HF.BF 3  superacid catalysis may be summarized as follows: 
     the catalyst molecule diffuses to the substrate molecule; 
     the HF.BF 3  activates the hydrocarbon, unlike conventional catalysts which activate the hydrogen molecule; 
     catalysis proceeds efficiently at low temperature and hydrogen pressure; 
     catalysis involves an ionic mechanism versus the free radical mechanism of conventional catalysis and therefore it results in different, more desirable products; and 
     fluorine incorporation into the bitumen products does not occur. 
     When these characteristics are taken in conjunction with the ready separability of HF and BF 3  from the hydrocracking products and with their reusability it becomes evident that the HF.BF 3  superacid catalyzed hydrocracking of oil sand bitumens offers good potential for commercial application. 
     Broadly stated the invention comprises a process for hydrocracking a heavy oil bitumen, or chemically related feedstock, which comprises reacting said feedstock with a gaseous superacid preferably in the presence of a hydrogen transfer agent and hydrogen to thereby yield low boiling point distillates. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an infrared spectrum (IR) of the &#34;saturate&#34; fraction of Cold Lake (CL) superacid-treated asphaltene, stored under N 2 . 
     FIG. 2 is an IR spectrum of the &#34;saturate&#34; fraction of CL superacid - treated asphaltene exposed to air. 
     FIG. 3 is a gas chromatogram of the &#34;saturate&#34; fraction of CL superacid - treated asphaltene. 
     FIG. 4 is a mass chromatogram (GCMS) of the &#34;saturate&#34; fraction of CL superacid - treated asphaltene. 
     FIG. 5a, 5b and 5c are a mass spectra of scans 246, 261 and 280 (C 16  H 24 ) of FIG. 4. 
     FIGS. 6a, 6b and 6c are a mass spectra of scans 286 (C 16  H 24 ), 294 and 297 (C 17  H 26 ) of FIG. 4. 
     FIG. 7 is a mass chromatogram (GCMS) of the &#34;saturate&#34; fraction of CL superacid - treated asphaltene after ionic hydrogenation. 
     FIGS. 8a and 8b are the mass spectra of scans 237 (C 16  H 30 ) and 249 (C 17  H 32 ) of FIG. 7. 
     FIG. 9 is a chemical ionization mass chromatogram GCMS of the &#34;saturate&#34; fraction of CL superacid - treated asphaltene. 
     FIGS. 10a, 10b, 10c are the mass spectra of scans 1082(a), 1102(b) and 1156(c) of FIG. 9. 
     FIG. 11 is the gas chromatogram of the &#34;saturate&#34; fraction of superacid - treated CL bitumen. 
     FIG. 12 is the gas chromatogram of the &#34;saturate&#34; fraction of Athabasca bitumen. 
     FIG. 13 is a plot of the total recovery as a percentage of the starting material utilized versus the volume of MeCH added. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Having reference to the accompanying drawings, there is provided an alternative process to the conventional catalytic hydrocracking of oil sand bitumens, heavy oil or chemically related feedbacks. More specifically, the process involves a superacid-catalyzed hydrocracking process which proceeds via a free radical (or ionic) mechanism. The preferred superacid catalyst would be in the gaseous state. 
     The sole superacid which is in the gaseous state is HF.BF 3 , or fluoroboric acid. However, other superacids, or the salts thereof may be contemplated for use as catalysts. Exemplary superacids would include, but are not limtied to HF.BF 3 , H 2  Si F 6  and HPF 6  or the like. 
     It is desirable that the reaction take place in the presence of a hydrogen transfer agent. Suitable hydrogen transfer agents would include the cycloalkanes and low molecular weight alkanes. A particularly suitable hydrogen transfer agent is methylcyclohexane (MeCH). Contrary to expectation it was found that using MeCH as the solvent desirably resulted in the oligomerization of MeCH to produce conjugated olefinic oligomers. It had been anticipated that the MeCH would be inert under these experimental reaction conditions. Upon exposure to air, these oligomers reacted with oxygen, turning the clear liquid of the separated oligomers to a partially, soluble, translucent gum. 
     Various experiments were conducted both in the presence and absence of the MeCH solvent. In the presence of MeCH, the yields of non-volatile products were higher and were dependent upon the amounts of solvents used, as can be illustrated in tables 1-7 given hereinafter. 
     The hydrogenation reaction, typically, takes place under mild reaction conditions. The reaction temperatures range between 25° C. to 300° C. A preferred temperature between about 170° C. and 250° C. The reaction time can range from an instantaneous time to about 24 hours. Typically, a preferred reaction time is from about one hour to about twenty four hours. Preferred conditions for hydrocracking are such that the reaction is conducted at a pressure of 500 psi H 2 . 
     
                       TABLE 1                                                     
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Superacid treatment of CL asphaltene                                      
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Reaction conditions:                                                      
          210° C.                                                  
          500 psi H.sub.2                                                 
          500 psi BF.sub.3                                                
           50 mL HF                                                       
           30 mL MeCH                                                     
           2.50 g asphaltene                                              
          Reaction time 24 hrs                                            
Product yields:                                                           
maltene        5.59 g         86.8% of product                            
asphaltene     0.85 g         13.2% of product                            
Class composition of maltene:                                             
Saturates      66.3                                                       
Monoaromatics  13.2                                                       
Diaromatics    4.4                                                        
Polyaromatics  2.4                                                        
Polar          13.6                                                       
Elemental analysis:                                                       
               maltene        asphaltene                                  
C              87.92          81.66                                       
H              10.30          7.20                                        
N              0.06           0.87                                        
S              0.23           0.81                                        
O              1.19           3.77                                        
MW             329            ND                                          
(H/C).sub.atomic                                                          
               1.53           1.05                                        
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                       TABLE 2                                                     
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Superacid treatment of CL bitumen                                         
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Reaction conditions:                                                      
          285° C.                                                  
          500 psi H.sub.2                                                 
          500 psi BF.sub.3                                                
           50 mL HF                                                       
           5 mL MeCH                                                      
           3.5 g bitumen                                                  
           24 hrs reaction time                                           
Product yields:                                                           
maltene   1.87 g   85% of products                                        
                                53.4% of bitumen                          
asphaltene                                                                
          0.33 g   15% of products                                        
                                9.4% of bitumen                           
Class composition of maltene:                                             
Saturates 34.4                                                            
Monoaromatics                                                             
          14.2                                                            
Diaromatics                                                               
          11.2                                                            
Polyaromatics                                                             
          17.7                                                            
Polar     22.5                                                            
Elemental analysis:                                                       
          maltene  asphaltene                                             
C         84.25    80.18                                                  
H         11.31    7.83                                                   
N         0.22     1.05                                                   
S         3.49     7.84                                                   
O         0.79     2.27                                                   
MW        447      2,345                                                  
(H/C).sub.atomic                                                          
          1.6      1.16                                                   
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                       TABLE 3                                                     
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Superacid treatment of Suncor Coker Feed bitumen                          
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Reaction conditions:                                                      
          200° C.                                                  
          500 psi H.sub.2                                                 
          500 psi BF.sub.3                                                
           50 mL HF                                                       
           30 mL MeCH                                                     
           2.64 g bitumen                                                 
           24 hrs reaction time                                           
Product yields:                                                           
maltene   5.5 g    89.4% of products                                      
                                208% of bitumen                           
asphaltene                                                                
          0.65 g   10.6% of products                                      
                                24% of bitumen                            
Class composition of maltene:                                             
Saturates 54.4                                                            
Monoaromatics                                                             
          22.7                                                            
Diaromatics                                                               
          2.7                                                             
Polyaromatics                                                             
          0.6                                                             
Polar     19.6                                                            
Elemental analysis:                                                       
          maltene  asphaltene                                             
C         87.95    77.44                                                  
H         10.88    7.13                                                   
N         0.02     1.49                                                   
S         0.76     7.56                                                   
O         0.76     6.38                                                   
MW        324      ND                                                     
(H/C).sub.atomic                                                          
          1.47     1.10                                                   
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                       TABLE 4                                                     
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Superacid treatment of Suncor Coker Feed asphaltene                       
______________________________________                                    
Reaction conditions:                                                      
          200° C.                                                  
          500 psi H.sub.2                                                 
          500 psi BF.sub.3                                                
           50 mL HF                                                       
           30 mL MeCH                                                     
           2.5 g bitumen                                                  
           24 hrs reaction time                                           
Product yields:                                                           
maltene   5.0 g    84.9% of products                                      
                                200% of as-                               
                                phaltene                                  
ashpaltene                                                                
          0.89 g   15.1% of products                                      
                                35.6% of as-                              
                                phaltene                                  
Class composition of maltene:                                             
Saturates 39.2                                                            
Monoaromatics                                                             
          41.4                                                            
Diaromatics                                                               
          1.0                                                             
Polyaromatics                                                             
          0.0                                                             
Polar     18.3                                                            
Elemental analysis:                                                       
          maltene  asphaltene                                             
C         87.35    76.46                                                  
H         10.81    7.51                                                   
N         0.0      1.81                                                   
S         0.74     7.33                                                   
O         1.14     6.88                                                   
MW        332      ND                                                     
(H/C).sub.atomic                                                          
          1.47     1.17                                                   
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                       TABLE 5                                                     
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Superacid treatment of Suncor Coker Feed bitumen                          
and asphaltene. Effect of the quantity of MeCH added..sup.a               
Expt. No.   1      2       3    4     5    6                              
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Bitumen (g) 2.69   2.88    --   --    3.08 --                             
Asphaltene (g)                                                            
            --     --      2.50 2.50  --   2.50                           
MeCH (mL)   5      30      5    30    15   15                             
______________________________________                                    
 .sup.a Conditions: 1 h, 200° C., 500 psi H.sup.2, 500 psi BF.sub.3
 50 mL HF, reactor volume 25 mL                                           
 
    
     
                       TABLE 6                                                     
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Gravimetric results of superacid experiments on Coker                     
Feed bitumen and aphaltene                                                
                                Total                                     
Asphaltene        Maltene       recovery                                  
Volume           % of            % of   % of                              
MeCH    % re-    starting % re-  starting                                 
                                        starting                          
(mL)    covered  material covered                                         
                                 material                                 
                                        material                          
______________________________________                                    
Bitumen                                                                   
5 mL    18.5      8.1     81.5   35.7   43.8                              
15 mL   13.1      9.4     86.9   62.3   71.7                              
30 mL    5.8     11.7     94.2   191.6  203.3                             
Asphaltene                                                                
5 mL    57.1     44.6     42.9   33.5   78.1                              
15 mL   54.6     49.2     45.3   40.8   90.0                              
30 mL   19.1     38.4     80.9   161.6  200.0                             
______________________________________                                    
 .sup.a Asphaltene content of bitumen was 15.5%.                          
 
    
     
                       TABLE 7                                                     
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Class composition of the maltenes.sup.a                                   
             Superacid experiment                                         
          Starting 1 (bi-  2 (bi-                                         
                                 3 (as- 4 (as-                            
Fraction  material tumen)  tumen)                                         
                                 phaltene)                                
                                        phaltene)                         
______________________________________                                    
Saturates 24.9     27.0    58.9  20.8   42.7                              
Monoaromatics                                                             
          10.8     9.6     18.2  4.6    22.2                              
Diaromatics                                                               
          8.5      4.4     0.5   1.5    1.4                               
Polyaromatics                                                             
          20.0     8.7     1.0   6.0    1.1                               
Polars    35.8     50.2    21.4  67.0   32.6                              
______________________________________                                    
 .sup.a As wt % of maltene. Separation done on an alumina/silica gel      
 column.                                                                  
 
    
     Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever.