Patent Publication Number: US-4842719-A

Title: Catalytic two-stage coal hydrogenation and hydroconversion process

Description:
The U.S. Government has rights to this invention pursuant to Contract No. DE-AC22-83PC0017 awarded by the U.S. Department of Energy. 
    
    
     This application is a continuation of application Ser. No. 725,458, filed Apr. 22, 1986 now abandoned. 
    
    
     BACKGOUND OF INVENTION 
     This invention pertains to an improved catalytic two-stage coal hyrogenation and hydroconversion process to produce increased yields of low-boiling hydrocarbon distillate liquid products. It pertains particularly to such a process in which the coal feed is rapidly heated and catalytically hydrogenated in a first reaction zone containing an ebullated catalyst bed, and then further hyrogenated and hydrocracked in a second close-coupled catalytic reaction zone at slightly higher temperature conditions to produce increased yields of desirable low boiling hydrocarbon liquid products while minimizing hydrocarbon catalyst gas yields and deactivation. 
     In the H-Coal® single stage coal liquefaction process, a particulate coal feed is usually slurried in a coal-derived recycle oil and the coal-oil slurry is preheated to a temperature near the reaction temperature then fed with hydrogen into a catalytic ebullated bed reactor, which operates at relatively high temperatures. In the reactor, a major portion of the coal is liquefied to produce hydrocarbon gas and distillate liquid fractions, but an undesirably large fraction of the coal liquefaction product is residual oil containing preasphaltenes and as asphaltene compounds. The preasphaltenes are highly unstable species at elevated temperatures, and can decompose thermally in the present of hydrogen to form asphaltenes while releasing gaseous hydrocarbons and water, but they can also rearrange, aromatize, and even condense to form char. In the reactor, the asphaltenes break down further heavy and light distillates, naptha and gaseous hydrocarbons. 
     In order to achieve satisfactory hydrocarbon liquid products in single-stage catalytic reaction processes, the reactor must be operated at a relatively high temperature which usually produces some retrograde materials and places a limit on the distillate liquid yields which can be achieved. Conventional single-stage catalytic processes for coal liquefaction and hydrogenation are generally disclosed in U.S. Pat. Nos. 3,519,555 and 3,791,959. In attempts to overcome the deficiencies of single-stage catalytic processes for coal liquefaction and hydrogenation, various two-stage catalytic processes have been proposed, including processes having thermal first stage reactor as well as catalytic-catalytic processes utilizing low first stage temperatures of only 600°-700° F. Examples of such coal hydrogenation processes using two stages of catalytic reaction are disclosed by U.S. Pat. Nos. 3,679,573; 3,700,584; 4,111,788; 4,350,582; 4,354,920; and 4,358,359. Although these processes using two stages of coal hydrogenation have generally provided some improvements over a single stage coal liquefaction process, such processes usually produce low quality liquid solvent materials in the reactor and do not provide for the disired hydrogenation and high conversion of the coal feed to produce high yields of desirable low-boiling hydrocarbon liquid products with minimal yields of hydrocarbon gas and heavy residuum fractions. Such improved results have now been achieved by the present two-stage catalytic coal hydrogenation and hydroconversion process. 
     SUMMARY OF INVENTION 
     The invention provides an improved process for direct two-stage catalytic hydrogenation, liquefaction and hydroconversion of coal to produce significantly increased yields of desirable low-boiling hydrocarbon distillate liquid products with minimal yields of hydrocarbon gas and high-boiling resid fractions. In the process, a particulate coal such as bituminous, sub-bituminous or lignite and a process-derived recycled hydrocarbon liquid solvent material are mixed together, and the resulting flowable coal-oil slurry is hydrogenated and liquefied using two stage direct-coupled ebullated bed catalytic reactors connected in series. 
     The coal-oil slurry is fed into the first stage back-mixed catalytic reaction zone which is maintained at selected moderate temperature and pressure conditions and in the presence of a particulate hydrogenation catalyst which promotes controlled rate liquefaction of the coal, while simultaneously hydrogenating the recycle solvent oils, at conditions which favor hydrogenation reactions at temperatures less than about 800° F. The first stage reaction zone contains an ebullated bed of a particulate hydrogenation catalyst to hydrogenate the aromatic rings in the particulate coal, recycle solvent and dissolved coal molecules and produce the disired low-boiling hydrocarbon liquid and gaseous material. 
     The catalyst used in each stage reactor should be selected from the group consisting of oxides or other compounds of cobalt, iron, molybdenum, nickle, tin, tungsten and mixtures thereof and hydrocarbon hyrogenation catalyst metal oxides known in the art, deposited on a base or support material selected from the group consisting of alumina, magnesia, silica, titania, and similar materials. Useful catalyst particle sizes can range about 0.030 to 0.125 inch effective diameter. 
     The first stage reactor is maintained at conditions of 650°-800° F. temperature, 1000-4000 psig hydrogen partial pressure, and at 10-60 lb/coal hr/ft 3  reactor feed rate or space velocity to produce a high quality hydrocarbon solvent material, while achieving at least about 50 W % conversion of the coal tetrahydrofuran to (THF) soluble materials. At such mild reaction conditions, hydrocracking, condensation and polymerization reactions along with formation of hydrocarbon gases are all advantageously minimized. Preferred first-stage reaction conditions are 700°-790° F. temperature, 1500-3500 psig hydrogen partial pressure and a coal space velocity of 15-50 lbs coal/hr/ft 3  reactor, with the preferred conditions being specific to the type of coal being processed. 
     From the first stage reaction zone, the total effluent material containing hydrogen and heteratom gases, hydrocarbon gases, hydrocarbon liquid fractions and unconverted coal materials is passed with additional hydrogen directly to the second stage back mixed catalytic/reaction zone the material is further hydrogenated and hydrocracked at a temperature at least about 25° F. higher than for the first stage reaction zone. Both stage reaction zones are upflow, well mixed ebullated bed catalytic reactors. For the second stage reactor, operating conditions are maintained at higher severity conditions which promote more complete thermal conversion of the coal to liquids, hydroconversion of primary liquids to distillate products, and product quality improvement via heteroatoms removal at temperature greater than 800° F., and with similar hydrogen pressure and a hydroconversion catalyst such as cobalt-moly on alumina support material. The desired second stage reaction conditions are coal space velocity of 750°-875° F. temperature, 1000-4000 psig hydrogen partial pressure and 10-60 lb coal/hr/ft 3  reactor volume to achieve at least about 90 W % conversion of the remaining reactive coal along with the asphaltene and preasphaltene compounds, and the heteroatoms are further reduced to provide THF soluble products materials. Preferred second stage reaction conditions are 800°-860° F. temperature, 1500-3500 psig hydrogen partial pressure, and coal space velocity of 15-50 lb/hr ft 3  reactor volume. 
     This two-stage catalytic coal liquefaction process provides high selectivity to low-boiling hydrocarbon liquid products and desired low yields of C 1  -C 3  hydrocarbon gases and residuum materials, together with minimal deactivation of the catalyst as measured by residuum conversion, where provides for extended activity and useful life of the catalyst. Overall, the present two-stage catalytic process produce higher yields of distillate and lower molecular weight products which are considerably more paraffinic and &#34;petroleum-like&#34; in terms of their chemical structure, than are produced by other single or two-stage direct coal liquefaction processes. It has been determined that the Watson characterization factor for the hydrocarbon liquid products in relation to their mean average boiling point from the present catalytic two-stage process are intermediate those products produced by the H-Coal® single-stage catalytic process and by petroleum catalytic hydroconversion processes. 
     The present two-stage direct coal liquefaction process advantageously provides a significant improvement over the single-stage H-Coal® coal liquefaction process, by providing an integrated recycle solvent hydrogenation step upstream of the conventional catalytic ebullated bed reactor. The reaction conditions are selected to provide controlled hydrogenation and conversion of the coal to liquid products (as defined by solubility in quinoline, tetrahydrofuran, or other similar solvent), while simultaneously hydrogenating the recycle and coal-derived product oils. Because the coal feed is dissolved in a high quality hydrocarbon solvent in the low temperature stage-stage reactor, the potential for retrogressive (coke forming) reactions is significantly reduced and solvent quality, hydrogen utilization and heteroatom removal are appreciably improved, which increases potential conversion of the coal while extending the catalyst life. The high quality effluent slurry material from the first stage reactor is fed to the close-coupled second stage catalytic reactor operated at somewhat higher temperatures to achieve increased coal conversion to mainly distillate liquid products. 
     The process thermal efficiency is advantageously improved over other two-stage coal liquefaction processes. Also, because of the high percentage conversion of coal to low-boiling hydrocarbon distillate liquids is achieved, higher boiling residuum fractions can be recycled to the first stage reactor. Thus, the present process advantageously achieves higher yields of distillate and lower molecular weight hydrocarbon products and less heteratoms with lower energy input than for single stage catalytic processes, and also for other thermal and thermal/catalytic two-stage coal liquefaction processes. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a schematic flow diagram of a two-stage catalytic coal hydrogenation and liquefaction process in accordance with the invention. 
     FIG. 2 is a graph showing the effect of first stage reactor temperatures on the yield of C 4  -975° F. hydrocarbon product liquid. 
    
    
     DESCRIPTION OF INVENTION 
     In the present invention, improved hydrogenation and liquefaction of coal is achieved by a two-stage catalytic process using two well-mixed ebullated bed catalytic reactors direct-connected in series. As is shown in FIG. 1, a coal such as bituminous, subbituminous or lignite is provided at 10 and passed through a coal preparation unit 12, where the coal is ground to a desired particle size range such as 50-375 mesh (U.S. Sieve Series) and dried to a desired moisture content such as 3-10 W % moisture. The particulate coal is then slurried at tank 14 with sufficient process-derived recycle solvent liquid 15 having a normal boiling temperature above about 550° F. to provide a flowable slurry. The weight ratio of solvent oil/coal is usually 1.4-5.0, with 1.5-3.0 being preferred. The coal/oil slurry is pressurized at pump 16, mixed with recycled hydrogen at 17, preheated at heater 18 to 600°-650° F. temperature and is then fed into the lower end of first stage back-mixed catalytic ebullated bed reactor 20. Fresh make-up high-purity hydrogen is provided as needed at 17a. 
     The coal-oil slurry and hydrogen streams enter reactor 20 containing an ebullated catalyst bed 22, passing uniformly upwardly through flow distributor 21 at flow rate and at temperature and pressure conditions to accomplish the desired hydrogenation reactions. The operation of the ebullated bed catalytic reactor including internal recycle of reactor liquid upwardly through the expanded catalyst bed is generally well known and is described by U.S. Pat. No. 4,437,973, which is incorporated herein by reference. The first stage reactor 20 preferably contains a particulate hydrogenation catalyst such as cobalt molybdate, nickle molybdate, or nickel tungsten on an alumina or silica support material. In addition, fresh particulate hydrogenation catalyst may be added to reactor 20 at connection 23 in the ratio of about 0.1 to 2.0 pounds of catalyst per ton of coal processed. Spend catalyst may be removed from reactor 20 at connection 24 to maintain the desired catalytic activity within the reactor. 
     Operating conditions in the first stage reactor are maintained at moderate temperature range of 650°-800° F., 1000-4000 psig hydrogen partial pressure, and coal feed rate or space velocity of 10-60 lb coal/hr/ft 3  reactor volume. The preferred reaction conditions will of 700°-790° F. temperature, 1500-3500 psig hydrogen partial pressure and 15-50 lb coal/hr/ft 3  reactor volume will be specific to the particular coal being processed, because different coals convert to liquids under thermal conditions at different rates. The optimal first stage reaction conditions will allow maxium utilization of hydrogen shuttling solvent compounds, such as pyrene/hydropyrenes, known to be present in coal-derived recycled oils, since catalytic rehydrogenation of donor species occurs simultaneously with solvent-to-coal hydrogen transfer. Coal-derived oils are also exposed to an efficient catalytic hydrogenation atmosphere immediately upon their formation, reducing the tendency for regressive repolymerization reactions which lead to poor quality hydrocarbon liquid products. First stage reactor thermal severity has been found to be quite important, as too high a severity leads to a coal conversion rate which is too rapid for the catalytic hydrogenation reactions to keep pace, as well as poorer hydrogenation equilibrium for the solvent compounds. Too low a thermal severity in the first stage, while still providing an efficient atmosphere for solvent hydrogenation, does not provide sufficient coal conversion to provide a substantial process improvement. 
     In the first stage reactor, the objective is to hydrogenate the aromatic rings in molecules of the feed coal, recycle solvent and dissolved coal so as to produce a high quality hydrogen donor solvent liquid in the presence of hydrogen and the hydrogenation catalyst. At the moderate catalytic reactor conditions used, heteroatoms are removed, retrogressive or coke forming reactions are essentially eliminated, and hydrocarbon gas formations are effectively minimized. Because of the reaction conditions used, i.e., relatively low temperature first stage, the catalyst promotes coal hydrogenation and minimizes polymerization and cracking reactions. Also because of these improved conditions in the first stage reactor, less coke is deposited on the catalyst at the milder reaction conditions used, and the deposited coke also has a desirably higher hydrogen/carbon ratio than for prior processes, which minimizes catalyst deactivation and appreciably prolongs the effective life of the catalyst. 
     From the first stage reactor 20, the total effluent material at 26 containing less than about 6 W % C 1  -C 3  hydrocarbon gases, 15-25 W % 650° F.- light hydrocarbon liquid and 60-70 W % 650° F.+ heavy hydrocarbon materials, expressed on an MAF coal basis is mixed additional preheated hydrogen at 28 and flows directly to the lower end of close-coupled second stage catalytic reactor 30. The effluent material at 26 preferably contains 3-6 W % C 1  -C 3  hydrocarbon gases, 18-22 W % C 4  -650 ° F. light hydrocarbon liquid fraction, 12-16 W % 650°-850° F. hydrocarbon liquid, and the remainder 850° F.+ heavy hydrocarbon materials, all expressed on a MAF coal basis. This reactor 30 which operates similarly to reactor 20 contains flow distributor grid 31 and catalyst bed 32, and is operated at a temperature at least about 25° F. higher than for the first stage reactor, and usually in the temperature range of 750°-875° F., but at temperatures lower than conventionally used for single-stage catalytic coal liquefaction processes. The higher temperature used in reactor 30 may be accomplished by utilization of the preheated hydrogen stream 28 as well as the second stage reactor heat of reaction. The second stage reactor pressure is slightly lower than for the first stage reactor to permit forward flow of the coal slurry material without any need for pumping, and additional makeup hydrogen is added at 28 to the second stage reactor as needed. A particulate catalyst similar to that used in the first stage reactor is utilized in bed 32 for the second stage reactor. 
     In the second stage reactor 30, the reaction conditions are selected to provide a more complete catalytic conversion of the unconverted coal to liquids, utilizing the high quality solvent liquid produced in the first stage reactor. The remaining reactive coal as well as preasphaltenes and asphaltenes are converted to distillate liquid products along with additional heteroatoms removal. Substantial secondary conversion of coal derived liquids to distillate products, and product upgrading by heteroatoms removal, is also accomplished in the second stage reactor. The reaction conditions are selected to minimizes gas formation or dehydrogenation of the first stage liquid effluent materials. Useful reactor conditions are 750°-875° F. temperature, 1000-4000 psig hydrogen partial pressure, and coal space velocity of 10-60 lb coal/hr/ft 3  reactor volume. Preferred reaction conditions will depend on the particular type coal being processed, and are usually 800°-860° F. temperature, 1500-3500 pisg hydrogen partial pressure and 15-50 lb/hr/ft 3  reactor space velocity. 
     It is an important characteristic of this process that very little change in the hydrocarbon compounds composition occurs between the first and second stage reactions. It has been found that the 850° F.- distillate liquids contain much lower levels of condensed aromatics and are significantly more aliphatic than are products produced from a conventional single stage catalytic coal hydrogenation process. Recycle of residual oil greatly enhances hydrogenation and hydroconversion of the coal in the first stage reactor. 
     From the second stage reactor 30, the effluent material at 38 is passed to a phase separator 40 operating at near reactor conditions, wherein a vapor fraction 41 is separated from a solids-containing liquid slurry fraction at 44. The vapor fraction 41 is treated at hydrogen purification section 42, from which hydrogen stream 43 is withdrawn for recycle by compressor 43a to the reactors 20 and 30. Fresh make-up hydrogen is added as needed at 17a. A vent gas containing undesired nitrogen and sulfur compounds is removed as stream 45. 
     The slurry liquid fraction 44 is pressure-reduced at 47 to near atmospheric pressure, such as about 200 psig, and passed to distillation system generally shown at 50. The resulting liquid fractions are recovered by a vapor/liquid flash in the distillation system 50, including atmospheric and vacuum distillation steps to produce light distillate product steam 51 and a heavier higher-boiling distillate liquid product stream 52. A bottoms stream 55 is passed to a liquid-solids separation step 56, from which unconverted coal and ash solids are removed at 57. The liquid stream 58 having reduced concentration of solids is recycled by pump 59 as slurring oil 15. If desired, a reduced solids concentration product liquid stream can be withdrawn at 60. 
     The recycle slurrying oil stream 58 is prepared by blending a portion of the atmospheric separator bottoms liquid slurry (containing 500° F.+ distillate, residuum, unreacted coal and ash), the atmospheric fractionation bottoms material (600° F. + distillate), and vacuum gas oil. This slurring liquid at 58 is then recycled back as stream 15 to the mixing step at 14, where it is mixed with the coal feed to form the flowable coal-oil slurry feedstream to the first stage reactor 20. 
     The recycle oil preparation in liquid-solids separation step 56 can be improved by reducing its solids concentration (ash and unconverted coal) by using known solids removal means in separation step 56, which such as by use of hydroclones, centrifuges, filters or solvent deashing techniques, with use of liquid hydroclones usually being preferred. 
     This invention will be further described and better understood by reference to the following Examples of comparative operations, which Examples whould not be construed as limiting the scope of the invention. 
     EXAMPLE 1 
     Several runs were made using the present two-stage catalytic process on Illinois No. 6 coal at the reaction conditions shown in Table 1, i.e., 750° F. first stage temperature and 825° F. second stage reactor temperature. From the results provided in Table 1, it is seen that substantially improved results including increased hydrogen effeiciencey and improved distillate liquid yields were achieved, as compared to results for a single stage catalytic coal liquefaction process operating at substantially the second stage reaction conditions. It should be noted that the yields of C 4  -975° F. and 390°-975° F. materials are both significantly greater for the present two-stage process than for single stage processes. 
     From the improved results achieved by the present process, it was also unexpectedly found that the 850° F. minus distillate fraction contained much lower levels of condensed aromatics and are significantly more aliphatic than the similar boiling fractions from a single stage catalytic coal liquefaction process, as is shown in Table 2, showing the proton distribution of the 850° F. minus distillate liquid. 
     
                       TABLE 2                                                     
______________________________________                                    
PROTON DISTRIBUTION OF 850° F.-DISTILLATES                         
                     Two-Stage                                            
                     Catalytic Process                                    
          Single Stage First    Second                                    
          H-Coal ® Process                                            
                       Stage    Stage                                     
______________________________________                                    
Aromatics                                                                 
Condensed   24.8            7.4      8.1                                  
Uncondensed  7.0            7.2      7.6                                  
Totals      31.8           14.6     15.7                                  
Alpha Aliphatics                                                          
Alkyl       11.8           10.8     10.1                                  
Cyclic      18.2           15.5     14.3                                  
Beta Aliphatics                                                           
Alkyl       16.6           24.4     25.0                                  
Cyclic      13.5           21.1     20.1                                  
Gamma Aliphatics                                                          
             8.0           13.6     14.8                                  
Totals      68.1           85.4     84.3                                  
______________________________________                                    
 
    
     
                       TABLE 1                                                     
______________________________________                                    
CATALYTIC TWO-STAGE PROCESS PERFORMANCE                                   
______________________________________                                    
Feed:  Illinois No. 6 Coal - 70 U.S. Mesh size                            
Catalyst:                                                                 
       First Stage - Amocat 1C                                            
       Second Stage - Amocat 1A                                           
Average Catalyst Age,                                                     
                216.3    664.3      Single                                
Lb Dry Coal/Lb Catalyst             Stage                                 
                                    Cata-                                 
                                    lytic(2)                              
OPERATING                                                                 
CONDITIONS                                                                
Temperature, °F.                                                   
First Stage     750      750                                              
Second Stage    825      825        850                                   
Pressure, psig  2506     2515       2500                                  
Dry Coal Space Velocity                                                   
                68       68         68                                    
(ea. stage),                                                              
Lb Dry Coal/Hr/Ft.sup.3                                                   
Catalyst(3)                                                               
Total Material  97.6     97.31                                            
Recovery, (Gross) W %                                                     
NORMALIZED YIELD,                                                         
W % Dry Coal                                                              
C.sub.1 -C.sub.3 Gas                                                      
                5.6      5.9        12.1                                  
C.sub.4 -390° F. Liquid                                            
                17.9     16.2       21.2                                  
390-500° F. Liquid                                                 
                13.9     12.2                                             
500-650° F. Liquid                                                 
                16.8     16.8                                             
650-850° F. Liquid                                                 
                11.7     10.9                                             
850-975° F. Liquid                                                 
                4.0      3.7                                              
390-975° F. Liquid                                                 
                46.4     49.4       32.0                                  
C.sub.4 -975° F. Liquid                                            
                64.3     65.6       53.2                                  
975° F. + Material                                                 
                4.9      4.6                                              
Unconverted Coal                                                          
Ash             11       11.1                                             
H.sub.2 O       9.2      9.0                                              
CO + CO.sub.2   0.46     0.3                                              
NH.sub.3        1.25     1.1                                              
H.sub.2 S       2.6      2.7                                              
Total (100 + H.sub.2 Reacted)                                             
                106.1    105.56                                           
PROCESS                                                                   
PERFORMANCE                                                               
Coal Conversion 94.3     94.8       94.6                                  
W % M.A.F.                                                                
975° F. + Conversion,                                              
                86.9     82.2       72.0                                  
W % M.A.F.                                                                
Hydrogen Efficiency                                                       
                10.5     10.7       9.6                                   
C.sub.4 -975° F., W % M.A.F.                                       
                72.3     67.2                                             
Organic Sulfur  98.0     96.6                                             
Removal, W %                                                              
Nitrogen Removal, W %                                                     
                79.2     66.5                                             
C.sub.4 -975° F. DISTILLATE                                        
QUALITY                                                                   
Gravity, °API                                                      
                25.5     23.7                                             
Sulfur, W %     0.035    0.037                                            
Nitrogen, W %   0.19     0.33                                             
______________________________________                                    
 
    
     (3) Space velocity expressed in terms of catalyst bed settled volume, which is equivalent to about twice the space velocity expressed in terms of reactor total volume; 
     This indicates that relatively little change occurs in chemical structure of the compounds in the second stage reactor compared to those in the first stage, and that significantly more aliphatic type compounds are produced in the two-stage catalytic process. 
     EXAMPLE 2 
     Additional runs were made for this two-stage catalytic process on sub-bituminous Wyodak coal. Comparative results with the Illinois No. 6 bituminous coal runs of example 1 are shown in Table 3. 
     
                                           TABLE 3                                 
__________________________________________________________________________
COMPARATIVE PROCESS PERFORMANCE                                           
                                 WYODAK(2)                                
                ILLINOIS NO. 6                                            
                         WYODAK(1)                                        
                                 H-COAL ®                             
                TWO STAGE                                                 
                         TWO STAGE                                        
                                 SINGLE STAGE                             
__________________________________________________________________________
C.sub.1 -C.sub.3 Gas W % M.A.F. Coal                                      
                5-7       7-10    5-13                                    
C.sub.4 -975° F., W % M.A.F. Coal                                  
                63-68    54-68   47-51                                    
Coal Conversion, W % M.A.F.                                               
                94-95    79-92   82-91                                    
Coal                                                                      
Hydrogen Consumption                                                      
                6-7      6-8     5-7                                      
Hydrogen Efficiency                                                       
                10-11    8-9      7-10                                    
975° F.+ 81-87ersion                                               
                         74-90   69-78                                    
__________________________________________________________________________
 (1)Preliminary Data                                                      
 (2)Run 2274 and 17787, HCoal ® Single Stage Catalytic Process        
 
    
     It is noted that percent coal conversion and yield of C 4  -975° F. material is somewhat less for Wyodak coal than for the Illinois No. 6 coal. 
     Results for the present two-stage catalytic process compared with the H-coal® single stage catalytic process on Wyodak coal are also shown in Table 3. It is noted that although the percent conversion of the Wyodak subbituminous coal is comparable to that for the single stage process, the C 4  -975° F. yield and the conversion of the 975° F.+ material are significantly higher than for the single stage process. 
     EXAMPLE 3 
     During two-stage catalytic operations on Wyodak coal, the effect of first stage reactor temperature on hydrogen content of reactor liquids and the solvent quality and on C 4  -975° F. yields were investigated. The first stage reactor temperature was varied between 650° F. and 775° F. with the second stage reactor temperature maintained at 810° F. and at 45 lb/hr-ft 3  catalyst space velocity in each reactor. The results for hydrogen content of the reactor liquid as indicated by hydrogen/carbon ratios are shown in Table 4. 
     
                       TABLE 4                                                     
______________________________________                                    
HYDROGEN CONTENT OF REACTOR LIQUIDS -                                     
RUN 227-22                                                                
FIRST                                                                     
STAGE    HYDROGEN TO CARBON RATIO                                         
REACTOR  650-850° F. LIQUIDS                                       
                         850° F.+ LIQUIDS                          
TEMP.    FIRST     SECOND    FIRST   SECOND                               
°F.                                                                
         STAGE     STAGE     STAGE   STAGE                                
______________________________________                                    
650      1.35      1.32      1.09    0.99                                 
700      1.36      1.35      1.11    1.07                                 
750      1.34      1.30      1.04    0.98                                 
775      1.29      1.29      0.97    0.94                                 
______________________________________                                    
 
    
     From these data, it is seen that the hydrogen to carbon ratios are greater for the first than for the second stage reactors at temperature up to about 750° and decline at 775° F. first stage temperature. Also, it is pointed out that these hydrogen/carbon ratios are among the highest reported in the literature for processing Wyodak coal. 
     The effect of first stage reactor temperature on solvent quality as determined by coal conversion achieved under standard autoclave test conditions is shown in Table 5. 
     
                       TABLE 5                                                     
______________________________________                                    
SOLVENT QUALITY OF REACTOR PRODUCTS -                                     
RUN 227-22                                                                
FIRST                                                                     
STAGE    COAL CONVERSION, W % M.A.F. COAL(2)                              
TEMP.°F.                                                           
         FIRST STAGE    SECOND STAGE                                      
______________________________________                                    
650      64.5           60.0                                              
700      70.4           60.8                                              
750      64.1           47.9                                              
750      64.6           49.7                                              
  750(1) 51.6           54.2                                              
775      42.6           46.7                                              
______________________________________                                    
(1) Wet coal feed producing lower hydrogen partial pressure               
(2) HRI Solvent Quality Test Conditions:                                  
Coal       Upper Wyodak                                                   
Temperature                                                               
           750° F.                                                 
Residence  30 Minutes                                                     
Time                                                                      
Type Test  Thermal                                                        
Solvent    Stage 1 - Filtered Liquid Product                              
           Stage 2 - Filtered Atmospheric Still Bottoms                   
Conversion As measured by solubility of microautoclave                    
           product in THF                                                 
 
    
     It is noted that the solvent quality is higher in the first stage reactor up to a first stage reactor temperature of about 750° F. 
     The effect of first stage reactor temperature on C 4  -975° F. liquid yields is shown in FIG. 2. It is seen that improved C 4  -975° F. yields are obtained for increasing first stage reaction temperature from 650° F. up to about 750° F., and that liquid yields are further increased as the second stage reactor temperature is increased from 810° F. to 825° F. Thus, the improved solvent liquid quality achieved in the first and second stage reactors is indicated by the high hydrogen content of the 650°-850° F. and 850° F.+ reactor liquid fractions as shown in Table 14 and the coal conversions obtained based on the standard test for solvent quality as shown in Table 5. 
     EXAMPLE 4 
     The present two-stage catalytic coal liquefaction process is compared with other two-stage thermal-catalytic coal liquefaction processes, as shown in Table 6. 
     
                                           TABLE 6                                 
__________________________________________________________________________
COMPARISON WITH THERMAL - CATALYTIC PROCESSES                             
                 TWO-STAGE                                                
                         HRI THERMAL-                                     
                                  KERR-MCGEE                              
                 CATALYTIC                                                
                         CATALYTIC                                        
                                  THERMAL CATALYTIC                       
Coal             ←Wyodak Clovis Point→                        
__________________________________________________________________________
C.sub.1 -C.sub.3 gas, W %                                                 
                 8.1     9.9      12.8                                    
C.sub.4 -850° F. Liquid, W %                                       
                 65.5    52.9     52.6                                    
Coal Conversion, W % MAF Coal                                             
                 89.3    90.2     92.1                                    
Hydrogen Consumption                                                      
                 8.1     6.6      5.2                                     
Hydrogen Efficiency                                                       
                 8.1     8.5      10.1                                    
975° F.+ Conversion                                                
                 87.4    76.9     78.6                                    
__________________________________________________________________________
 
    
     From this comparison, it is seen that the present catalytic two-stage process provides improved results of reduced C 1  -C 3  gas yields, increased C 4  -850° F. liquid yields, and increased conversion of 975° F. + fraction material compared to the other processes. 
     Although this invention has been described broadly and in terms of certain preferred embodiments thereof, it will be understood that modifications and variation of the process can be made within the spirit and scope of the invention, which is defined by the following claims.