Abstract:
A process for treating liquid hydrocarbon, includes the steps of providing a liquid hydrocarbon containing complex sulfur-containing compounds, providing a bioactive material selected from or derived from members of genus Alcaligenes; and exposing the liquid hydrocarbon to the bioactive material under effective conditions such that the bioactive material interacts with the complex sulfur compounds and transforms the organic sulfur-containing compounds into inorganic sulfur compounds.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to biodesulfurization of hydrocarbons and, more particularly, to a bioactive material and method using same for breaking down complex organic sulfur-containing compounds within a hydrocarbon so as to facilitate removal of same. 
     Sulfur content in hydrocarbons is an important concern for numerous reasons, particularly when the hydrocarbon is to be used as a fuel. Numerous methods, systems and compositions are known and used for removal of sulfur from the hydrocarbon. Although these are somewhat effective, problems remain. 
     Sulfur is particularly difficult to effectively remove when it is present in organic sulfur-containing compounds, such as dibenzothiophene. The normal degradative pathway for dibenzothiophene (DBT) results in a different, but still complex organic sulfur-containing compound, such as 3-hydroxy-2-formilbenzothiophene, and removal of this compound undesirably removes carbon from the hydrocarbon. 
     In light of the foregoing, it is clear that the need remains for addressing the removal of sulfur when present in complex organic compounds. 
     It is therefore the primary object of the present invention to provide a method and bioactive material which are well suited to this removal. 
     It is a further object of the present invention to provide a method and bioactive material which are useful for reducing the C15+ fraction of a hydrocarbon, and thereby further improving the characteristics of same. 
     Other objects and advantages of the present invention will appear hereinbelow. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a process is provided for treating liquid hydrocarbon, which process comprises the steps of providing a liquid hydrocarbon containing organic sulfur-containing compounds; providing a bioactive material selected from or derived from members of genus Alcaligenes; and exposing said liquid hydrocarbon to said bioactive material under effective conditions such that said bioactive material interacts with said organic sulfur-containing compounds and transforms said organic sulfur-containing compounds into inorganic sulfur compounds. These inorganic sulfur compounds can then be more easily separated from the hydrocarbon. 
     A bioactive material is also provided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A detailed description of preferred embodiments of the present invention follows, with reference to the attached drawings, wherein: 
     FIG. 1 schematically illustrates a selective pathway of DBT breakdown when treated in accordance with the invention, as well as a conventional degradative pathway; 
     FIG. 2 illustrates activity and percent reduction in DBT as a function of pH in accordance with the present invention; 
     FIG. 3 illustrates activity over a range of temperatures in accordance with the present invention; 
     FIG. 4 illustrates activity as a function of concentration of a substrate in accordance with the present invention; 
     FIG. 5 illustrates activity as a function of concentration of the bioactive material; 
     FIG. 6 illustrates data for a hydrocarbon before and after treatment to show the presence in the product of biphenyl; 
     FIG. 7 shows bioactivity of the bioactive material of the present invention in connection with other organic sulfur compounds; 
     FIG. 8 shows excellent results obtained in treating a hydrocarbon in terms of reduction in organic sulfur compounds, as well as reduction in the C16+ fraction; and 
     FIG. 9 shows sulfur removal results in connection with emulsions having different ratios of hydrocarbon to water. 
    
    
     DETAILED DESCRIPTION 
     The invention relates to a bioactive material and a method or process for using same in treating hydrocarbons to transform complex organic sulfur compounds into more easily removable inorganic sulfur compounds, thereby making sulfur removal easier. 
     In accordance with the present invention, it has been found that members of the genus Alcaligenes, under certain conditions, have excellent activity toward attacking carbon-sulfur-carbon bonds in complex organic sulfur-containing compounds, thereby leading to inorganic sulfur compounds as desired. The species  Alcaligenes xylosoxidans  has been found to be particularly effective at this selective transformation. Cells of this material have been deposited under the Budapest Treaty on Sep. 16, 2002. ATCC whose address is 1081 University Boulevard, Manassas, Va. 20110-2209 and has received Patent Deposit Designation PTA-4669. A copy of the Deposit Receipt from ATCC has been forwarded to the U.S. Patent and Trademark Office. 
     The bioactive material of the present invention preferably includes cells from  Alcaligenes xylosoxidans  strains and more specifically an enzymatic extract from the active cells which extract is biocatalytically active on organic sulfur compounds as described above. This extract contains an oxidase enzyme believed to be particularly active. 
     In accordance with the present invention, the bioactive material as described above is advantageously used to transform organic sulfur-containing compounds contained in hydrocarbons into inorganic sulfur compounds, which are more readily removed from the hydrocarbon. Further, these inorganic compounds have an affinity toward water and, when the treatment process is carried out with an emulsion, the inorganic sulfur compounds are formed in or travel to the water phase further facilitating separation. Still further, this separation of sulfur is accomplished without removal of desirable constituents from the hydrocarbon. 
     Typical hydrocarbons which can advantageously be treated in accordance with the present invention include any liquid hydrocarbon or hydrocarbon slurry which contains organic sulfur compounds. Preferred hydrocarbons for such treatment include, among others, bitumen, heavy crude, medium crude, Diesel fuel, gasoline, coal slurry and mixtures thereof. Bitumen is particularly advantageously treated in accordance with the present invention since this hydrocarbon contains significant amounts of organic sulfur-containing compounds. 
     In accordance with the present invention, it has further been found that some strains of the bioactive material in accordance with the present invention are hydrophilic and lipophobic. As the mechanism is carried out by contacting the materials, this makes contacting of the bioactive material with hydrocarbon difficult. In accordance with the present invention, this problem is solved, when present, by forming a hydrocarbon in water emulsion of the hydrocarbon, and adding the bioactive material to the water, either before or after emulsion formation, such that the bioactive material is nevertheless in intimate contact with a major portion of the hydrocarbon. 
     As set forth above, the bioactive material in accordance with the present invention is particularly effective in attacking carbon-sulfur-carbon bonds of complex organic sulfur-containing compounds. For example, and as shown in FIG. 1, dibenzothiophene (DBT), when exposed to the bioactive material in accordance with the present invention, reacts along a selective pathway wherein the end result is a final product including biphenyl and inorganic sulfur compounds such as sulphates, hydrogen sulfide and the like. These inorganic sulfur-containing compounds are more readily separated from the hydrocarbon using conventional methods and equipment. Thus, in accordance with the present invention, the bioactive material provides activity along selective pathways which advantageously render sulfur in the hydrocarbon more easily removable. 
     FIG. 1 also illustrates, in the right hand portion of the figure, the degradative pathway experienced without a selective catalyst such as the bioactive material of the present invention. As shown, DBT may break down but this does not result in sulfur being moved to inorganic, less complex, and more easily removable compounds. 
     The bioactive material in accordance with the present invention is also active in breaking down other organic sulfur-containing compounds, such as alkylthiophenes, naphthobenzothiophene, dimethylthiopene, thionaphthene and the like. The mechanism of the bioactive material in accordance with the present invention advantageously allows for selective breaking down of such compounds, and any other compounds involving carbon-sulfur-carbon bonds, so as to transform the sulfur into inorganic sulfur compound form as desired. 
     The bioactive material and hydrocarbon in accordance with the present invention are advantageously exposed to each other, preferably at a concentration of at least about 1 mg/ml of total protein in the extract per ml of hydrocarbon of total emulsion, more preferably between about 1 mg/ml and about 5 mg/ml of total protein in the extract or ml of hydrocarbon of total emulsion, and at effective conditions, preferably a temperature between about 30° C. and about 50° C. and a pH of between about 7.0 and about 8.0, such that the complex sulfur-containing organic compounds are transformed as desired. 
     Conversion rates of dibenzothiophene, in accordance with the present invention, are advantageously at least about 70% wt., which results in a substantially facilitated sulfur removal from the hydrocarbon as desired. This advantageously transforms a substantial amount of DBT and other difficult-to-remove sulfur into more easily removed form, and further into a form which does not include carbon that is preferably left in the hydrocarbon. 
     The bioactive material was isolated from a soil and hydrocarbon sample which is typical of a local environment in Venezuela. A sample of this soil was then mixed with a mineral medium and dibenzothiophene so as to obtain a biomass from which the bacteria can be isolated. Utilizing known isolation techniques, this leads to identification of the genus and species. From this, a pure culture can be obtained and subjected to biochemical tests that confirm Alcaligenes, and further can be subjected to DNA testing which confirm xylosoxidans as the species. 
     From a pure culture of the material, biomass is further produced and subjected to centrifuge so as to separate cells which can be processed, for example using mechanical or other extraction methods, to obtain an enzymatic extract containing oxidase and possessing the activity discovered in accordance with the present invention. Using known methods, an inoculum is obtained from which a biomass is produced, and the desired extract is obtained from the biomass as more fully described below. 
     A process for extracting the particularly desirable enzymatic extract in accordance with the present invention can be conducted by first sterilizing a culture medium in a suitable vessel, for example at a pressure of 15 psi for 15 minutes at a temperature of 121° C. 
     The vessel is then preferably held at a fermentation temperature, preferably of about 30° C., and ventilated or exposed to a flow of air for about 1 hour, with air flow rate at the rate of about 1 liters per minute. 
     The vessel is preferably inoculated with the strain, for example in an amount of about 0.2% weight of the culture medium. The bacteria is then preferably allowed to incubate, for example at a temperature of 30° C., with agitation at 150 rpm, for a period of about 72 hours, and in a mineral medium containing organic sulfur, for example DBT, as the sole source of sulfur, and further with a glucose as a growth factor, for example in an amount of about 0.2% wt. 
     The material is then subjected to an incubation period for approximately 18-24 hours, without agitation, and with a flow of air preferably of about 2 liters per minute, and a temperature of about 30° C. 
     The incubated material is then advantageously subjected to centrifugation, for example at 10,000 x g, for about 20 minutes, so as to recover the biomass material and separate material from which the extract is to be obtained. 
     This separated material is then re-suspended in a buffer solution of potassium phosphate (100 mM), having a pH of 7, and this suspension is subjected to a Braun homogenizer so as to rupture the cells. 
     The solution is then again subjected to centrifuge at 10,000×g, for an additional period of about 20 minutes, and supernatant material containing the desired enzymatic extract can the be withdrawn from the solution. 
     The following examples further demonstrate the bioactive material and use same in accordance with the present invention. 
     EXAMPLE 1 
     In this example, an enzymatic extract of  Alcaligenes xylosoxidans  identified as INTS-1 was prepared in mixture with a hydrocarbon, with the pH varied between 7, 8 and 9, and the activity of the bioactive material was measured. 
     FIG. 2 shows activity for INTS-1 at various pH, along with percent reduction in DBT. 
     As shown, best results are obtained at pH greater than 6 and up to 9. 
     The bioactive material was then further evaluated, at pH of 7, and at temperatures between 30° C. and 50° C. FIG. 3 shows the results of this testing, and it can be seen that the material was effective between temperatures of 30° C. and 50° C. 
     Activity of the strain as identified above was then measured for a fixed concentration of the enzymatic extract relative to increasing amounts of DBT substrate. FIG. 4 shows the results obtained, and the continuous increase in activity shows that saturation by the DBT substrate occurs at a value greater than 100 ppm. 
     Activity of the bioactive material as described above was then evaluated at different concentrations of an enzymatic extract per volume of hydrocarbon. FIG. 5 shows the results of this evaluation, and shows that activity of the material increases gradually above a concentration of 2 mg/ml. An optimum concentration of this strain is about 2 mg/ml depending upon whether the additional activity obtained at higher concentration is cost justified. 
     EXAMPLE 2 
     In this example, a hydrocarbon sample was obtained which contained dibenzothiophene (DBT), and was exposed to bioactive material in accordance with the present invention. 
     FIG. 6 sets forth gas chromatography—mass spectrometry data for the starting product and finishing materials for two runs, namely “Experimental 1” and “Experimental 2”, and a “Control” which contained no bioactive material. As set forth above, the catalytic activity of the bioactive material in accordance with the present invention breaks down DBT to form biphenyl (BF) as well as the desired inorganic sulfur compounds which are more readily removed. The second and third patterns shown in FIG. 6 clearly show a new spike appearing which corresponds to the identification of biphenyl (BF), thereby confirming that transformation of dibenzothiopene to biphenyl is occurring, as desired, and this confirms transformation of sulfur from the organic compound to inorganic compounds, and also as desired. 
     Table 1 sets forth these results in table form as well. 
     
       
         
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 Area Relative (%) 
                   
               
             
          
           
               
                   
                 DBT 
                 BF 
               
               
                   
                   
               
             
          
           
               
                   
                 Control 
                 99.05 
                 0.95 
               
               
                   
                 Experimental 1 
                 92.69 
                 7.31 
               
               
                   
                 Experimental 2 
                 92.62 
                 7.38 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 3 
     In this example, the same bioactive material as evaluated in Examples 1 and 2 was further evaluated in connection with activity on other organic sulfur compounds, namely dimethylthiopene and thionaphthene. FIG. 7 shows the relationship between incubation time in days and activity in connection with these two other organic sulfur compounds. As shown, the bioactive material in accordance with the present invention has activity toward breaking down these organic sulfur compounds as well. 
     EXAMPLE 4 
     In this example, a bitumen in water emulsion was prepared having a ratio of hydrocarbon to water of 70:30, and the hydrocarbon contained DBT, alkyl thiopenes and naphthabenzothiophene, as well as a substantial fraction of C16+ hydrocarbons. 
     This hydrocarbon was treated using the bioactive material of the present invention, and an analysis of the starting hydrocarbon and final product are shown in FIG.  8 . As shown, the organic sulfur compounds are substantially reduced, as is the C16+ fraction, all as desired in accordance with the present invention. 
     EXAMPLE 5 
     As set forth above, the hydrocarbon to water ratio of emulsions formed in accordance with the present invention can also effect the amount of sulfur removal. 
     Sulfur removal was evaluated for five different emulsions having ratios of hydrocarbon to water of between 70:30 and 30:70, and the results of this evaluation are set forth in FIG.  9 . 
     As shown, the percentage removal of sulfur increases as the water content of the emulsion increases. 
     In accordance with the foregoing, it is clear that a bioactive material, and method for using same, have been provided which advantageously convert dibenzothiophene and other organic sulfur-containing compounds into inorganic sulfur compounds such as SO 4  compounds and H 2 S, along with biphenyl hydrocarbons. This is advantageous in that the sulfur is then more easily removable when in inorganic form, as desired in accordance with the present invention. 
     This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.