PatentDe  


Dokumentenidentifikation EP0584281 27.04.1995
EP-Veröffentlichungsnummer 0584281
Titel SYSTEM UND KONTINUIERLICHES VERFAHREN ZUR BIOKATALYTISCHEN ENTSCHWEFELUNG VON SCHWEFELHALTIGEN HETEROZYKLISCHEN MOLEKÜLEN.
Anmelder Energy Biosystems Corp., The Woodlands, Tex., US
Erfinder MONTICELLO, Daniel, J., The Woodlands, TX 77381, US
Vertreter derzeit kein Vertreter bestellt
DE-Aktenzeichen 69201792
Vertragsstaaten AT, BE, CH, DE, DK, ES, FR, GB, GR, IT, LI, LU, MC, NL, SE
Sprache des Dokument En
EP-Anmeldetag 08.04.1992
EP-Aktenzeichen 929144152
WO-Anmeldetag 08.04.1992
PCT-Aktenzeichen US9202856
WO-Veröffentlichungsnummer 9219700
WO-Veröffentlichungsdatum 12.11.1992
EP-Offenlegungsdatum 02.03.1994
EP date of grant 22.03.1995
Veröffentlichungstag im Patentblatt 27.04.1995
IPC-Hauptklasse C12S 1/00

Beschreibung[en]
BACKGROUND

Sulfur is an objectionable element which is nearly ubiquitous in fossil fuels, where it occurs both as inorganic (e.g., pyritic) sulfur and as organic sulfur (e.g., a sulfur atom or moiety present in a wide variety of hydrocarbon molecules, including for example, mercaptans, disulfides, sulfones, thiols, thioethers, thiophenes, and other more complex forms). Organic sulfur can account for close to 100% of the total sulfur content of petroleum liquids, such as crude oil and many petroleum distillate fractions. Crude oils can typically range from close to about 5 wt% down to about 0.1 wt% organic sulfur. Those obtained from the Persian Gulf area and from Venezuela (Cerro Negro) can be particularly high in organic sulfur content. Monticello, D.J. and J.J. Kilbane, "Practical Considerations in Biodesulfurization of Petroleum", IGT's 3rd Intl. Symp. on Gas, Oil, Coal, and Env. Biotech., (Dec. 3-5, 1990) New Orleans, LA, and Monticello, D.J. and W.R. Finnerty, (1985) Ann. Rev. Microbiol. 39:371-389.

The presence of sulfur has been correlated with the corrosion of pipeline, pumping, and refining equipment, and with premature breakdown of combustion engines. Sulfur also contaminates or poisons many catalysts which are used in the refining and combustion of fossil fuels. Moreover, the atmospheric emission of sulfur combustion products such as sulfur dioxide leads to the form of acid deposition known as acid rain. Acid rain has lasting deleterious effects on aquatic and forest ecosystems, as well as on agricultural areas located downwind of combustion facilities. Monticello, D.J. and W.R. Finnerty, (1985) Ann. Rev. Microbiol. 39:371-389. To combat these problems, several methods for desulfurizing fossil fuels, either prior to or immediately after combustion, have been developed.

One technique which is employed for pre-combustion sulfur removal is hydrodesulfurization (HDS). This approach involves reacting the sulfur-containing fossil fuel with hydrogen gas in the presence of a catalyst, commonly a cobalt- or molybdenum-aluminum oxide or a combination thereof, under conditions of elevated temperature and pressure. HDS is more particularly described in Shih, S.S. et al., "Deep Desulfurization of Distillate Components", Abstract No. 264B AIChE Chicago Annual Meeting, presented November 12, 1990, (complete text available upon request from the American Institute of Chemical Engineers; hereinafter Shih et al.), Gary, J.H. and G.E. Handwerk, (1975) Petroleum Refining: Technology and Economics, Marcel Dekker, Inc., New York, pp. 114-120, and Speight, J.G., (1981) The Desulfurization of Heavy Oils and Residue, Marcel Dekker, Inc., New York, pp. 119-127. HDS is based on the reductive conversion of organic sulfur into hydrogen sulfide (H&sub2;S), a corrosive gaseous product which is removed from the fossil fuel by stripping. Elevated or persistent levels of hydrogen sulfide are known to inactivate or poison the chemical HDS catalyst, complicating the desulfurization of high-sulfur fossil fuels.

Moreover, the efficacy of HDS treatment for particular types of fossil fuels varies due to the wide chemical diversity of hydrocarbon molecules which can contain sulfur atoms or moieties. Some classes of organic sulfur molecules are labile and can be readily desulfurized by HDS; other classes are refractory and resist desulfurization by HDS treatment. The classes of organic molecules which are often labile to HDS treatment include mercaptans, thioethers, and disulfides. Conversely, the aromatic sulfur-bearing heterocycles (i.e., aromatic molecules bearing one or more sulfur atoms in the aromatic ring itself) are the major class of HDS-refractory organic sulfur-containing molecules. Typically, the HDS-mediated desulfurization of these refractory molecules proceeds only at temperatures and pressures so extreme that valuable hydrocarbons in the fossil fuel can be destroyed in the process. Shih et al.

Recognizing these and other shortcomings of HDS, many investigators have pursued the development of commercially viable techniques of microbial desulfurization (MDS). MDS is generally described as the harnessing of metabolic processes of suitable bacteria to the desulfurization of fossil fuels. Thus, MDS typically involves mild (e.g., physiological) conditions, and does not involve the extremes of temperature and pressure required for HDS. Additionally, the ability of a biological desulfurizing agent to renew or replenish itself is viewed as a potentially significant advantage over physicochemical catalysis.

The discovery that certain species of chemolithotrophic bacteria, most notably Thiobacillus ferrooxidans, obtain the energy required for their metabolic processes from the oxidation of pyritic (inorganic) sulfur into water-soluble sulfate has stimulated the search for an MDS technique for the desulfurization of coal, in which pyritic sulfur can account for more than half of the total sulfur present. Recently, Madgavkar, A.M. (1989) U.S. Patent No. 4,861,723, has proposed a continuous T. ferrooxidans -based MDS method for desulfurizing coal. However, a commercially viable MDS process for the desulfurization of coal has not yet emerged.

Because of the inherent specificity of biological systems, T. ferooxidans MDS is limited to the desulfurization of fossil fuels in which inorganic sulfur, rather than organic sulfur, predominates. Progress in the development of an MDS technique appropriate for the desulfurization of fossil fuels in which organic sulfur predominates has not been as encouraging. Several species of bacteria have been reported to be capable of catabolizing the breakdown of sulfur-containing hydrocarbon molecules into water-soluble sulfur products. One early report describes a cyclic desulfurization process employing Thiobacillus thiooxidans, Thiophyso volutans, or Thiobacillus thioparus as the microbial agent. Kirshenbaum, I., (1961) U.S. Patent No. 2,975,103. More recently, Monticello, D.J. and W.R. Finnerty, (1985) Ann. Rev. Microbiol. 39:371-389, and Hartdegan, F.J. et al., (May 1984) Chem. Eng. Progress 63-67, have reported that such catabolic desulfurization of organic molecules is, for the most part, merely incident to the utilization of the hydrocarbon portion of these molecules as a carbon source, rather than a sulfur-selective or -specific phenomenon. Moreover, catabolic MDS proceeds most readily on the classes of organic sulfur molecules described above as labile to HDS.

Although Monticello and Finnerty report that several species of bacteria have been described as capable of desulfurizing the HDS-refractory aromatic sulfur-bearing heterocycles, in particular Pseudomonas putida and P. alcaligenes, this catabolic pathway is also merely incident to the utilization of the molecules as a carbon source. Consequently, valuable combustible hydrocarbons are lost, and frequently the water-soluble sulfur products generated from the catabolism of sulfur-bearing heterocycles are small organic molecules rather than inorganic sulfur ions. As a result, the authors conclude that the commercial viability of these MDS processes is limited. Monticello, D.J. and W.R. Finnerty, (1985) Ann. Rev. Microbiol. 39:371-389.

None of the above-described desulfurization technologies provides a viable means for liberating sulfur from refractory organic molecules, such as the sulfur-bearing heterocycles. The interests of those actively engaged in the refining and manufacturing of petroleum fuel products have accordingly become focused on the need to identify such a desulfurization method, in view of the prevalence of these refractory molecules in crude oils derived from such diverse locations as the Middle East (about 40% of the total organic sulfur content present in aromatic sulfur-bearing heterocycles) and West Texas (up to about 70% of the total).

SUMMARY OF THE INVENTION

This invention relates to a continuous process for desulfurizing a petroleum liquid which contains organic sulfur molecules, a significant portion of which are comprised of sulfur-bearing heterocycles, comprising the steps of: (a) contacting the petroleum liquid with a source of oxygen under conditions sufficient to increase the oxygen tension in the petroleum liquid to a level at which the biocatalytic oxidative cleavage of carbon-sulfur bonds in sulfur-bearing heterocycles proceeds; (b) introducing the oxygenated petroleum liquid to a reaction vessel while simultaneously introducing an aqueous, sulfur-depleted biocatalytic agent to the reaction vessel, the agent being capable of inducing the selective oxidative cleavage of carbon-sulfur bonds in sulfur-bearing heterocycles; (c) incubating the oxygenated petroleum liquid with the biocatalytic agent in the reaction vessel under conditions sufficient for biocatalytic oxidative cleavage of said carbon-sulfur bonds, for a period of time sufficient for a significant number of cleavage reactions to occur, whereby the organic sulfur content of the treated petroleum liquid is significantly reduced and a significant amount of water-soluble inorganic sulfate is generated; (d) removing the desulfurized petroleum liquid from the reaction vessel; (e) retrieving the spent aqueous biocatalytic agent from the reaction vessel, the spent agent being significantly enriched in inorganic sulfate; (f) treating the sulfate-enriched spent aqueous biocatalytic agent in a manner sufficient for the removal of a substantial amount of inorganic sulfate from the agent, whereby the biocatalytic activity of the agent is regenerated; and (g) reintroducing the regenerated aqueous biocatalytic agent to the reaction vessel while simultaneously introducing a petroleum liquid in need of biocatalytic desulfurization.

In a preferred embodiment of the invention, the biocatalytic agent comprises a culture of mutant Rhodococcus sp. ATCC No. 53968. This microbial biocatalyst is particularly advantageous in that it is capable of catalyzing the selective liberation of sulfur from HDS-refractory sulfur-bearing aromatic heterocycles, under mild conditions of temperature and pressure. Therefore, even crude oils or petroleum distillate fractions containing a high relative abundance of refractory organic sulfur-bearing molecules can be desulfurized without exposure to conditions harsh enough to degrade valuable hydrocarbons. Additionally, the biocatalyst is regenerated and reused in the continuous method described herein; it can be used for many cycles of biocatalytic desulfurization. Moreover, the method and process of the instant invention can be readily integrated into existing petroleum refining or processing facilities.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic illustration of the structural formula of dibenzothiophene, a model HDS-refractory sulfur-bearing heterocycle.

Figure 2 is a schematic illustration of the cleavage of dibenzothiophene by oxidative and reductive pathways, and the end products thereof.

Figure 3 is a schematic illustration of the stepwise oxidation of dibenzothiophene along the proposed "4S" pathway of microbial catabolism.

Figure 4 is a schematic flow diagram of a preferred embodiment of the instant continuous process for biocatalytic desulfurization (BDS)of this invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention employs a biocatalytic agent which is capable of selectively liberating sulfur from the classes of organic sulfur molecules which are most refractory to current techniques of desulfurization, such as HDS. The instant biocatalytic agent is used in a continuous process for desulfurizing a petroleum liquid containing organic sulfur molecules, a significant proportion of which are comprised of sulfur-bearing heterocycles. These HDS-refractory molecules occur in simple one-ring forms (e.g., thiophene), or more complex multiple condensed-ring forms. The difficulty of desulfurization through conventional techniques increases with the complexity of the molecule.

The tripartite condensed-ring sulfur-bearing heterocycle dibenzothiophene (DBT), shown in Figure 1, is particularly refractory to HDS treatment, and therefore can constitute a major fraction of the residual post-HDS sulfur in fuel products. Alkyl-substituted DBT derivatives are even more refractory to HDS treatment, and cannot be removed even by repeated HDS processing under increasingly severe conditions. Shih et al. Moreover, as noted above, DBTs can account for a significant percentage of the total organic sulfur in certain crude oils. Therefore, DBT is viewed as a model refractory sulfur-bearing molecule in the development of new desulfurization methods. Monticello, D.J. and W.R. Finnerty, (1985) Ann. Rev. Microbiol. 39:371-389. No naturally occurring bacteria or other microbial organisms have yet been identified which are capable of effectively degrading or desulfurizing DBT. Thus, when released into the environment, DBT and related complex heterocycles tend to persist for long periods of time and are not significantly biodegraded. Gundlach, E.R. et al., (1983) Science 221:122-129.

However, several investigators have reported the genetic modification of naturally-occurring bacteria into mutant strains capable of catabolizing DBT. Kilbane, J.J., (1990) Resour. Cons. Recycl. 3:69-79, Isbister, J.D., and R.C. Doyle, (1985) U.S. Patent No. 4,562,156, and Hartdegan, F.J. et al., (May 1984) Chem. Eng. Progress 63-67. For the most part, these mutants desulfurize DBT nonspecifically, and release sulfur in the form of small organic sulfur breakdown products. Thus, a portion of the fuel value of DBT is lost through this microbial action. Isbister and Doyle reported the derivation of a mutant strain of Pseudomonas which appeared to be capable of selectively liberating sulfur from DBT, but did not elucidate the mechanism responsible for this reactivity. As shown in Figure 2, there are at least two possible pathways which result in the specific release of sulfur from DBT: oxidative and reductive.

Kilbane recently reported the mutagenesis of a mixed bacterial culture, producing one which appeared capable of selectively liberating sulfur from DBT by the oxidative pathway. This culture was composed of bacteria obtained from natural sources such as sewage sludge, petroleum refinery wastewater, garden soil, coal tar-contaminated soil, etc., and maintained in culture under conditions of continuous sulfur deprivation in the presence of DBT. The culture was then exposed to the chemical mutagen 1-methyl-3-nitro-1-nitrosoguanidine. The major catabolic product of DBT metabolism by this mutant culture was hydroxybiphenyl; sulfur was released as inorganic water-soluble sulfate, and the hydrocarbon portion of the molecule remained essentially intact. Based upon these results, Kilbane proposed that the "4S" catabolic pathway summarized in Figure 3 was the mechanism by which these products were generated. The designation "4S" refers to the reactive sulfur intermediates of the proposed pathway: DBT-sulfoxide, DBT-sulfone, DBT-sulfonate, and the liberated product, inorganic sulfate. The hydrocarbon portion of the DBT molecule remains essentially intact; in Figure 3, the theoretical hydrocarbon product, dihydroxybiphenyl is shown. In practice, monohydroxybiphenyl is also observed. Kilbane, J.J., (1990) Resour. Cons. Recycl. 3:69-79, the teachings of which are incorporated herein by reference.

Subsequently, Kilbane has isolated a mutant strain of Rhodococcus rhodochrous from this mixed bacterial culture. This mutant, ATCC No. 53968, is a particularly preferred biocatalytic agent for use with the instant method of continuous biocatalytic desulfurization. The isolation and characteristics of this mutant are described in detail in J.J. Kilbane, U.S. Patent Specification Nr. 5,104,801. In the instant method for biocatalytic desulfurization (BDS), the ATCC No. 53968 biocatalytic agent is employed in a continuous desulfurization process for the treatment of a petroleum liquid in which HDS-refractory organic sulfur molecules, such as the aromatic sulfur-bearing heterocycles, constitute a significant portion of the total organic sulfur content.

Figure 4 is a schematic flow diagram of the continuous process for biocatalytic desulfurization (BDS) of this invention. Petroleum liquid 1, in need of BDS treatment, enters through line 3. As discussed above and shown in Figure 3, oxygen is consumed during biocatalytic desulfurization; accordingly, a source of oxygen (5) is introduced through line 7, and is contacted with petroleum liquid 1 in mixing chamber 9 whereby oxygen tension in petroleum liquid 1 is sufficiently increased to permit biocatalytic desulfurization to proceed. In this manner, the instant process allows the practitioner to capitalize on the greater capacity of petroleum (over aqueous liquids) to carry dissolved oxygen. For example, oxygen is ten times more soluble in octane than in water. Pollack, G.L., (1991) Science 251:1323-1330. Thus oxygen is more effectively delivered to the biocatalyst than it would be by, for example, sparging air into the reaction mixture during biocatalysis. In fact, direct sparging is to be avoided due to the tendency of such processes to produce explosive mixtures. Source of oxygen 5 can be oxygen-enriched air, pure oxygen, an oxygen-saturated perfluorocarbon liquid, etc. Oxygenated petroleum liquid thereafter passes through line 11 to injection ports 13, through which it enters reaction vessel 15.

An aqueous culture of the microbial biocatalytic agent of the present invention is prepared by fermentation in bioreactor 17, using culture conditions sufficient for the growth and biocatalytic activity of the particular micro-organism used. In order to generate maximal biocatalytic activity, it is important that the biocatalyst culture be maintained in a state of sulfur deprivation. This can be effectively accomplished by using a nutrient medium which lacks a source of inorganic sulfate, but is supplemented with DBT or a liquid petroleum sample with a high relative abundance of sulfur heterocycles. A particularly preferred microbial biocatalyst comprises a culture of mutant Rhodococcus sp. ATCC No. 53968. This biocatalytic agent can advantageously be prepared by conventional fermentation techniques comprising aerobic conditions and a suitable nutrient medium which contains a carbon source, such as glycerol, benzoate, or glucose. When the culture has attained a sufficient volume and/or density, it is delivered from bioreactor 17 through line 19 to mixing chamber 25, where it is optionally supplemented with fresh, sulfur-free nutrient medium as necessary. This medium is prepared in chamber 21 and delivered to the mixing chamber 25 through line 23. The aqueous biocatalytic agent next passes through mixing chamber 29, and then through line 31, to injection ports 33. It is delivered through these ports into reaction vessel 15, optimally at the same time as the oxygenated petroleum liquid 1 is delivered through ports 13. The ratio of biocatalyst to petroleum liquid (substrate) can be varied widely, depending on the desired rate of reaction, and the levels and types of sulfur-bearing organic molecules present. Suitable ratios of biocatalyst to substrate can be ascertained by those skilled in the art through no more than routine experimentation. Preferably, the volume of biocatalyst will not exceed about one-tenth the total volume in the reaction vessel (i.e., the substrate accounts for at least about 9/10 of the combined volume).

Injection ports 13 and 33 are located at positions on the vessel walls conducive to the creation of a countercurrent flow within reaction vessel 15. In other words, mixing takes place within vessel 15 at central zone 35, as the lighter organic petroleum liquid substrate rises from injection ports 13 and encounters the heavier aqueous biocatalyst falling from injection ports 33. Turbulence and, optimally, an emulsion, are generated in zone 35, maximizing the surface area of the boundary between the aqueous and organic phases. In this manner, the biocatalytic agent is brought into intimate contact with the substrate fossil fuel; desulfurization proceeds relatively rapidly due to the high concentration of dissolved oxygen in the local environment of the aromatic sulfur-bearing heterocyclic molecules on which the ATCC No. 53968 biocatalyst acts. Thus, the only rate-limiting factor will be the availability of the sulfur-bearing heterocycles themselves.

The BDS process is most effective for the desulfurization of crude oils and petroleum distillate fractions which are capable of forming a transient or reversible emulsion with the aqueous biocatalyst in zone 35, as this ensures the production of a very high surface area between the two phases as they flow past each other. However, biocatalysis will proceed satisfactorily even in the absence of an emulsion, as long as an adequate degree of turbulence (mixing) is induced or generated. Optionally, means to produce mechanical or hydrodynamic agitation at zone 35 can be incorporated into the walls of the reaction vessel. Such means can also be used to extend the residence time of the substrate petroleum liquid in zone 35, the region in which it encounters the highest levels of BDS reactivity.

In addition, it is important that the reaction vessel be maintained at temperatures and pressures which are sufficient to maintain a reasonable rate of biocatalytic desulfurization. For example, the temperature of the vessel should be between about 10°C and about 60°C; ambient temperature (about 20°C to about 30°C) is preferred. However, any temperature between the pour point of the petroleum liquid and the temperature at which the biocatalyst is inactivated can be used. The pressure within the vessel should be at least sufficient to maintain an appropriate level of dissolved oxygen in the substrate petroleum liquid. However, the pressure and turbulence within the vessel should not be so high as to cause shearing damage to the biocatalyst.

As a result of biocatalysis taking place in zone 35, the organic sulfur content of the petroleum liquid is reduced and the inorganic sulfate content of the aqueous biocatalyst is correspondingly increased. The substrate petroleum liquid, having risen from ports 13 through BDS-reactive zone 35, collects at upper zone 37, the region of the reaction vessel located above the points at which aqueous biocatalyst is injected into the vessel (at ports 33). Conversely, the aqueous biocatalyst, being heavier than the petroleum liquid, does not enter zone 37 to any significant extent. As the desulfurized petroleum liquid collects in this region, it is drawn off or decanted from the reaction vessel at decanting port 38 from which it enters line 39. The desulfurized petroleum liquid (41) delivered from line 39 is then subjected to any additional refining or finishing steps which may be required to produce the desired low-sulfur fuel product.

Optionally, any volatile exhaust gasses (45) which form in the headspace of the reaction vessel can be recovered through line 43. These gasses can be condensed, then burned in a manner sufficient to provide any heat which may be necessary to maintain the desired level of BDS-reactivity within the reaction vessel.

Similarly, after passing through injection ports 33 and falling through BDS-reactive zone 35, the aqueous biocatalyst collects in lower zone 47, below injection ports 13. The petroleum liquid substrate entering from these injection ports does not tend to settle into zone 47 to any significant extent; being lighter than the aqueous phase, it rises into zone 35. As noted above, the biocatalyst collecting in zone 47 has acquired a significant level of inorganic sulfate as a result of its reactivity with the substrate petroleum liquid. Biocatalytic activity is depressed by the presence of inorganic sulfate, as this is a more easily assimilable form of sulfur for metabolic use than organic sulfur. Thus, the biocatalyst is said to be "spent". However, its activity can be regenerated by removing the inorganic sulfate from the biocatalytic agent, thereby restoring the ATCC No. 53968 biocatalyst to its initial sulfur-deprived state.

This is accomplished by retrieving the spent biocatalyst from the reaction vessel through line 49, and treating it in a manner sufficient to remove inorganic sulfate. The spent agent is first introduced into chamber 51, in which solids, sludges, excess hydrocarbons, or excess bacteria (live or dead), are removed from the aqueous biocatalyst and recovered or discarded (53). The aqueous biocatalyst next passes through chamber 55, and optional chamber 57, where it is contacted with an appropriate ion exchange resin or resins, such as an anion exchange resin and a cation exchange resin. Suitable ion exchange resins are commercially available; several of these are highly durable resins, including those linked to a rigid polystyrene support. These durable ion exchange resins are preferred. Two examples of polystyrene-supported resins are Amberlite® IRA-400-OH (Rohm and Haas), and Dowex 1X8-50 (Dow Chemical Co.) Dowex MSA-1 (Dow Chemical Co.) is an example of a suitable non-polystyrene supported resin. The optimal ion exchange resin for use herein can be determined through no more than routine experimentation. Inorganic sulfate ions bind to the resin(s) and are removed from the aqueous biocatalytic agent. As a result, biocatalytic activity is regenerated.

Alternative means to remove aqueous sulfate and thereby regenerate biocatalytic activity can also be employed. Suitable alternatives to treatment with an ion exchange resin include, for example, treatment with an agent capable of removing sulfate ion by precipitation. Suitable agents include the salts of divalent cations such as barium chloride or calcium hydroxide. Calcium hydroxide is preferred due to the chemical nature of the sulfate-containing reaction product formed: calcium sulfate (gypsum), which can be readily separated from the aqueous biocatalyst. Other examples of suitable regeneration means include treatment with semipermeable ion exchange membranes and electrodialysis.

Any of the above means for regenerating biocatalytic activity can be performed by treating the aqueous culture of the biocatalyst, or by initially separating (e.g., by sieving) the microbial biocatalyst from the aqueous liquid and treating the liquid alone, then recombining the biocatalyst with the sulfate-depleted aqueous liquid.

The regenerated aqueous biocatalyst proceeds to mixing chamber 29, where it is mixed with any fresh, sulfur-free nutrient medium (prepared in chamber 21) and/or any fresh ATCC No. 53968 culture (prepared in bioreactor 17), which may be required to reconstitute or replenish the desired level of biocatalytic activity.

The regenerated biocatalytic agent is delivered through line 31 to injection ports 33, where it reenters the reaction vessel (15) and is contacted with additional petroleum liquid in need of BDS treatment, entering the reaction vessel through injection ports 13 in the manner described previously. It is desirable to monitor and control the rates of reactants entering and products being removed from the reaction vessel, as maintaining substantially equivalent rates of entry and removal will maintain conditions (e.g., of pressure) sufficient for biocatalysis within the vessel. In this manner, a continuous stream of desulfurized petroleum liquid is generated, without the need to periodically pump the contents of the reaction vessel into a settling chamber where phase separation takes place, as described in Madkavkar, A.M. (1989) U.S. Patent No. 4,861,723, and Kirshenbaum, I. (1961) U.S. Patent No. 2,975,103.

The progress of BDS treatment of the petroleum liquid within the vessel can be monitored using conventional techniques, which are readily available to those skilled in the art. Baseline samples can be collected from the substrate before it is exposed to the biocatalyst, for example from sampling ports located at mixing chamber 9. Post-BDS samples can be collected from the desulfurized petroleum liquid which collects within the reaction vessel at zone 37, through sampling ports located in the vessel wall, or a sampling valve located at decanting port 38. The disappearance of sulfur from substrate hydrocarbons such as DBT can be monitored using a gas chromatograph coupled with mass spectrophotometric (GC/MS), nuclear magnetic resonance (GC/NMR), infrared spectrometric (GC/IR), or atomic emission spectrometric (GC/AES, or flame spectrometry) detection systems. Flame spectrometry is the preferred detection system, as it allows the operator to directly visualize the disappearance of sulfur atoms from combustible hydrocarbons by monitoring quantitative or relative decreases in flame spectral emissions at 392 nm, the wavelength characteristic of atomic sulfur. It is also possible to measure the decrease in total organic sulfur in the substrate fossil fuel, by subjecting the unchromatographed samples to flame spectrometry. If the extent of desulfurization is insufficient, the desulfurized petroleum liquid collected from line 39 can optionally be reintroduced through line 3 and subjected to an additional cycle of BDS treatment. Alternatively, it can be subjected to an alternative desulfurization process, such as HDS.

In other preferred embodiments of the present method, an enzyme or array of enzymes sufficient to direct the selective cleavage of carbon-sulfur bonds can be employed as the biocatalyst. Preferably, the enzyme(s) responsible for the "4S" pathway can be used. Most preferably, the enzyme(s) can be obtained from ATCC No. 53968 or a derivative thereof. This enzyme biocatalyst can optionally be used in carrier-bound form. Suitable carriers include killed "4S" bacteria, active fractions of "4S" bacteria (e.g., membranes), insoluble resins, or ceramic, glass, or latex particles.


Anspruch[de]
  1. Kontinuierliches Verfahren zur Entschwefelung einer Erdölflüssigkeit, die organischen Schwefel enthält, wovon ein erheblicher Anteil in schwefelhaltigen heterocyclischen Molekülen anwesend ist, wobei das Verfahren die folgenden Schritte aufweist:
    • (a) In-Kontakt-Bringen der Erdölflüssigkeit mit einer Sauerstoffquelle unter Bedingungen, die ausreichen, um das Sauerstoff-Potential in der Flüssigkeit zu erhöhen;
    • (b) Einleiten der mit Sauerstoff angereicherten Erdölflüssigkeit in einen in Vertikalrichtung langgestreckten Reaktionsbehälter, der eine Einrichtung hat, um Erdölflüssigkeit aus einem oberen Bereich zu dekantieren, und eine Einrichtung hat, um wäßrige Flüssigkeit aus einem unteren Bereich zu entfernen; während gleichzeitig
    • (c) ein wäßriger Biokatalysator in den Reaktionsbehälter an einer Stelle, die räumlich von der Einleitungsstelle der Erdölflüssigkeit in den Reaktionsbehälter verschieden ist, auf solche Weise eingeleitet wird, daß in dem Behälter ein Gegenstrom erzeugt wird, wobei die Ausbildung des Gegenstroms zu einer ausreichenden Vermischung zwischen der Erdölflüssigkeit und dem wäßrigen Biokatalysator führt, so daß die Biokatalyse mit der gewünschten Rate ablaufen kann, wobei der wäßrige Biokatalysator folgendes aufweist:
      • i) einen oder mehrere mikrobielle Organismen, die ein Enzym exprimieren, das durch eine für Schwefel spezifische oxidative Spaltungsreaktion das Entfernen von Schwefel aus organischen Molekülen einschließlich schwefeltragenden heterocyclischen Molekülen katalysiert, so daß entschwefelte organische Moleküle und anorganische Schwefelionen produziert werden,
      • ii) von solchen mikrobiellen Organismen abgeleitete Enzyme oder
      • iii) Gemische aus solchen mikrobiellen Organismen und Enzymen;
    • (d) Inkubieren der mit Sauerstoff angereicherten Erdölflüssigkeit mit dem Biokatalysator in dem Reaktionsbehälter unter für die Biokatalyse ausreichenden Bedingungen, wodurch eine entschwefelte Erdölflüssigkeit erzeugt wird, deren organischer Schwefelanteil signifikant geringer als der der in den Reaktionsbehälter eingeleiteten Erdölflüssigkeit ist, wobei ferner anorganische Schwefelionen erzeugt werden;
    • (e) Dekantieren der entschwefelten Erdölflüssigkeit aus dem oberen Bereich des Reaktionsbehälters;
    • (f) Abziehen von erschöpftem wäßrigem Biokatalysator aus dem unteren Bereich des Reaktionsbehälters, wobei der erschöpfte Biokatalysator signifikant mit anorganischen Schwefelionen angereichert ist;
    • (g) Aufbereiten des erschöpften wäßrigen Biokatalysators auf eine Weise, die zum Entfernen einer erheblichen Menge von anorganischem Schwefel daraus ausreichend ist, wodurch die Wirksamkeit des Biokatalysators regeneriert wird; und
    • (h) Einleiten von regeneriertem wäßrigem Biokatalysator in den Reaktionsbehälter, während gleichzeitig in diesen eine Erdölflüssigkeit, die der biokatalytischen Entschwefelung bedarf, auf solche Weise eingeleitet wird, daß der Gegenstrom aufrechterhalten wird.
  2. Verfahren nach Anspruch 1, wobei die Zugaberaten von Reaktionspartnern in den und die Entnahme von Produkten aus dem Reaktionsbehälter so überwacht und gesteuert werden, daß ihre Raten im wesentlichen äquivalent sind, wobei die Reaktionspartner biokatalytisch zu behandelnde Erdölflüssigkeit und regenerierten wäßrigen Biokatalysator umfassen und die Produkte entschwefelte Erdölflüssigkeit und erschöpften wäßrigen Biokatalysator umfassen.
  3. Verfahren nach Anspruch 1, wobei die Erdölflüssigkeit fähig ist, eine vorübergehende oder reversible Emulsion mit dem wäßrigen Biokatalysator zu bilden, wodurch in dem Reaktionsbehälter eine Emulsionszone erzeugt wird, die oben von einer Zone, die reich an entschwefelter Erdölflüssigkeit ist, und unten von einer Zone, die reich an erschöpftem Biokatalysator ist, begrenzt ist.
  4. Verfahren nach Anspruch 3, wobei die Bildung oder Aufrechterhaltung der Emulsionszone mit Unterstützung durch mechanische oder hydrodynamische Bewegung erreicht wird.
  5. Verfahren nach Anspruch 3,wobei regenerierter Biokatalysator in den Reaktionsbehälter an oder nahe der Grenze zwischen der Zone der entschwefelten Erdölflüssigkeit und der Emulsionszone eingeleitet wird und von dem Biokatalysator zu behandelnde Erdölflüssigkeit in den Reaktionsbehälter an oder nahe der Grenze zwischen der Emulsionszone und der Zone des erschöpften wäßrigen Biokatalysators eingeleitet wird.
  6. Verfahren nach Anspruch 1, wobei der wäßrige Biokatalysator entweder eine Kultur von Rhodococcus sp. ATCC Nr. 53968 oder ein Derivat davon ist oder ein von Rhodococcus sp. ATCC Nr. 53968 oder einem Derivat davon erhaltenes Enzym ist und wobei das Enzym an einen Träger gebunden sein kann.
  7. Verfahren nach Anspruch 1, wobei der wäßrige Biokatalysator in Schritt (g) regeneriert wird durch
    • i) Entfernen einer signifikanten Zahl von anorganischen Schwefelionen aus dem erschöpften Biokatalysator; und
    • ii) Ergänzen von Nährstoffen und/oder mikrobiellen Organismen, Enzymen oder Gemischen davon, wie es erforderlich ist, um den gewünschten Grad der biokatalytischen Wirksamkeit aufrechtzuerhalten,
    wobei Schritt i) beispielsweise durchgeführt wird durch In-Kontakt-Bringen des erschöpften wäßrigen Biokatalysators mit einem Harz, das fähig ist, die genannten Ionen zu binden, und zwar unter Bedingungen, die für die Bindung dieser Ionen an das Harz ausreichend sind.
  8. Verfahren nach Anspruch 1, das die folgenden zusätzlichen Schritte aufweist:
    • (i) Einfangen und Kondensieren von etwaigen leichtflüchtigen, entflammbaren Abgasen, die aus dem Reaktionsbehälter während des Entfernens der entschwefelten Erdölflüssigkeit entweichen; und
    • (j) Verbrennen dieser Gase auf eine Weise, die ausreicht, um jegliche zur Förderung der Biokatalyse erforderliche Wärme zu liefern.
  9. System zum kontinuierlichen Entschwefeln einer Erdölflüssigkeit (1), die organischen Schwefel enthält, von dem ein signifikanter Anteil in schwefelhaltigen heterocyclischen Molekülen anwesend ist, durch Behandlung mit einem wäßrigen Biokatalysator, der aufweist:
    • i) einen oder mehrere mikrobielle Organismen, die ein Enzym exprimieren, das durch eine für Schwefel spezifische oxidative Spaltungsreaktion das Entfernen von Schwefel aus organischen Molekülen einschließlich schwefelhaltigen heterocyclischen Molekülen katalysiert, so daß entschwefelte organische Moleküle und anorganische Schwefelionen produziert werden,
    • ii) von solchen mikrobiellen Organismen abgeleitete Enzyme oder
    • iii) Gemische aus solchen mikrobiellen Organismen und Enzymen,
    wobei das System folgendes aufweist:
    • (a) eine Mischkammer (9), um die Erdölflüssigkeit (1) mit einer Sauerstoffquelle (5) unter Bedingungen in Kontakt zu bringen, die ausreichen, um die Sauerstoff-Potential in der Flüssigkeit (1) auf einen Wert zu erhöhen, der ausreicht, um den Ablauf der Bio-katalyse mit einer gewünschten Rate zuzulassen, wobei die Mischkammer (9) durch eine Leitung (11) verbunden ist mit
    • (b) einem in Vertikalrichtung langgestreckten Reaktionsbehälter (15), der ein erstes Set von Einspritzeinlässen (13), durch die mit Sauerstoff angereicherte Erdölflüssigkeit (1) aus Leitung (11) eingeleitet wird, und ein zweites Set von Einspritzeinlässen (33) hat, durch die der wäßrige Biokatalysator aus Leitung (31) eingeleitet wird, wobei das erste (13) und das zweite (33) Set von Einspritzeinlässen an Stellen der Wand des Behälters (15) angeordnet sind, die räumlich voneinander getrennt und geeignet positioniert sind, um einen Gegenstrom innerhalb einer zentralen Zone (35) des Behälters (15) zu erzeugen, wenn die mit Sauerstoff angereicherte Erdölflüssigkeit (1) und der wäßrige Biokatalysator gleichzeitig in sie eingeleitet werden, wobei die Ausbildung eines Gegenstroms für eine ausreichende Vermischung zwischen der mit Sauerstoff angereicherten Erdölflüssigkeit (1) und dem wäßrigen Biokatalysator sorgt, so daß die Biokatalyse mit der gewünschten Rate ablaufen kann,

      wobei ferner der Behälter (15) eine Dekantieröffnung (38) hat, die an einer Stelle der Wand des Behälters (15) liegt, die einer oberen Zone (37) entspricht, wobei die obere Zone (37) über dem zweiten Set von Einspritzeinlässen (33) liegt, so daß sich in der oberen Zone (37) sammelnde entschwefelte Erdölflüssigkeit durch die Dekantieröffnung (38) zu einer Leitung (39) abgezogen werden kann,

      wobei außerdem der Behälter (15) eine Leitung (39) hat, die an einer Stelle der Wand des Behälters (15), die einer unteren Zone (47) entspricht, angeschlossen ist, wobei die untere Zone (47) unterhalb des ersten Sets von Einspritzeinlässen (13) liegt, so daß sich in der unteren Zone (47) sammelnder erschöpfter wäßriger Biokatalysator aus dem Behälter (15) durch Leitung (49) abgezogen und regeneriert werden kann, wobei der erschöpfte Biokatalysator signifikant mit anorganischen Schwefelionen angereichert ist; und
    • (c) Einrichtungen zum Regenerieren des erschöpften wäßrigen Biokatalysators, wobei diese Einrichtungen aufweisen:
      • i) eine Abscheidekammer (51), der erschöpfter wäßriger Biokatalysator durch Leitung (49) zugeführt wird und in der alle Feststoffe (53), beispielsweise überschüssige Kohlenwasserstoffe oder überschüssige lebende oder tote Bakterien, abgetrennt werden;
      • ii) wenigstens eine Schwefelionen-Abtrennkammer (55), der aus der Abscheidekammer (51) austretender wäßriger Biokatalysator zugeführt wird und in der der Biokatalysator in Kontakt gebracht wird mit wenigstens einem Agens zum Abtrennen anorganischer Schwefelionen, beispielsweise mit einem Ionenaustauschharz,an das anorganische Schwefelionen binden, oder mit dem Salz eines zweiwertigen Kations, das mit anorganischen Schwefelionen ein unlösliches Präzipitat bildet; und
      • iii) eine Mischkammer (29), in der der aus der Schwefelionen-Abtrennkammer (55) austretende regenerierte wäßrige Biokatalysator mit allen frischen Komponenten ergänzt wird, die erforderlich sind, um den gewünschten Grad der biokatalytischen Wirksamkeit aufrechtzuerhalten, beispielsweise mit zusätzlichen Mikroorganismen oder Medium-Bestandteilen,
    bevor der regenerierte Biokatalysator durch Leitung (31) den Einspritzeinlässen (33) und dem Reaktionsbehälter (15) zugeführt wird, wobei die Zuführung einhergeht mit der Zuführung von mit Sauerstoff angereicherter Erdölflüssigkeit (1) durch die Einspritzeinlässe (13) zu dem Behälter (15) erfolgt, wodurch der Gegenstrom in der zentralen Zone (35) des Behälters (15) aufrechterhalten wird.
  10. System nach Anspruch 9 zur Verwendung mit einer Erdölflüssigkeit, die fähig ist, mit dem wäßrigen Biokatalysator eine vorübergehende oder reversible Emulsion zu bilden, so daß die zentrale Zone (35) des Behälters (15) von einer Emulsion eingenommen wird, wobei diese Emulsion oben von der an entschwefelter Erdölflüssigkeit reichen oberen Zone (37) begrenzt ist und unten von der an erschöpftem wäßrigem Biokatalysator reichen unteren Zone (47) begrenzt ist, wobei in dem Reaktionsbehälter (15) des Systems das erste Set von Einspritzeinlässen (13) für die Zuführung von Erdölflüssigkeit (1) in der Wand des Behälters (15) an oder nahe der Grenze zwischen der zentralen Emulsionszone (35) und der unteren Zone (47) mit erschöpftem wäßrigem Biokatalysator angeordnet ist und das zweite Set von Einspritzeinlässen (33) zur Zuführung von regeneriertem Biokatalysator in der Wand des Behälters (15) an oder nahe der Grenze zwischen der zentralen Emulsionszone (35) und der oberen Zone (37) von entschwefelter Erdölflüssigkeit angeordnet ist.
Anspruch[en]
  1. A continuous process for desulfurizing a petroleum liquid which contains organic sulfur, a significant portion of which is present in sulfur-bearing heterocyclic molecules, comprising the steps of:
    • (a) contacting the petroleum liquid with a source of oxygen under conditions sufficient to increase the oxygen tension in said liquid;
    • (b) introducing the oxygenated petroleum liquid to a vertically elongate reaction vessel having means to decant petroleum liquid from an upper region and means to remove aqueous liquid from a lower region; while simultaneously
    • (c) introducing an aqueous biocatalyst to said reaction vessel at a site spatially distinct from the site of introduction thereto of the petroleum liquid, in such a fashion as to create a countercurrent flow within the vessel, the establishment of countercurrent flow providing sufficient mixing between the petroleum liquid and the aqueous biocatalyst for biocatalysis to proceed at the desired rate, said aqueous biocatalyst comprising:
      • i) one or more microbial organisms expressing an enzyme that catalyzes, by a sulfur-specific oxidative cleavage reaction, the removal of sulfur from organic molecules including sulfur-bearing heterocycles, such that desulfurized organic molecules and inorganic sulfur ions are produced,
      • ii) enzymes derived from such microbial organisms, or
      • iii) mixtures of such microbial organisms and enzymes;
    • (d) incubating the oxygenated petroleum liquid with the biocatalyst in the reaction vessel under conditions sufficient for biocatalysis, whereby a desulfurized petroleum liquid is produced, the organic sulfur content thereof being significantly lower than that of the petroleum liquid introduced into the reaction vessel, further whereby inorganic sulfur ions are produced;
    • (e) decanting the desulfurized petroleum liquid from the upper region of the reaction vessel;
    • (f) removing spent aqueous biocatalyst from the lower region of the reaction vessel, the spent biocatalyst being significantly enriched in inorganic sulfur ions;
    • (g) treating the spent aqueous biocatalyst in a manner sufficient for the removal of a substantial amount of inorganic sulfur therefrom, whereby the activity of said biocatalyst is regenerated; and
    • (h) introducing regenerated aqueous biocatalyst to the reaction vessel while simultaneously introducing thereto a petroleum liquid in need of biocatalytic desulfurization, in such a fashion as to maintain countercurrent flow.
  2. A method of Claim 1 wherein the rates of addition of reactants to and removal of products from the reaction vessel are monitored and controlled such that the rates thereof are substantially equivalent, the reactants comprising petroleum liquid to be biocatalytically treated and regenerated aqueous biocatalyst, and the products comprising desulfurized petroleum liquid and spent aqueous biocatalyst.
  3. A method of claim 1 wherein the petroleum liquid is capable of forming a transient or reversible emulsion with the aqueous biocatalyst, whereby an emulsion zone is produced in the reaction vessel, said emulsion zone being bounded above by a zone enriched in desulfurized petroleum liquid, and bounded below by a zone enriched in spent aqueous biocatalyst.
  4. A method of Claim 3 wherein the formation or maintenance of the emulsion zone is accomplished with the assistance of mechanical or hydrodynamic agitation.
  5. A method of Claim 3 wherein regenerated biocatalyst is introduced to the reaction vessel at or close to the boundary between the desulfurized petroleum liquid zone and the emulsion zone, and petroleum liquid to be treated by the biocatalyst is introduced to the reaction vessel at or close to the boundary between the emulsion zone and the spent aqueous biocatalyst zone.
  6. A method of Claim 1 wherein the aqueous biocatalyst is either a culture of Rhodococcus sp. ATCC No. 53968 or a derivative thereof, or is an enzyme obtained from Rhodococcus sp. ATCC No. 53968 or a derivative thereof, and the enzyme may be bound to a carrier.
  7. A method of Claim 1 wherein the aqueous biocatalyst is regenerated at step (g) by
    • i) removing a significant number of inorganic sulfur ions from the spent biocatalyst; and
    • ii) replenishing nutrients and/or microbial organisms, enzymes or mixtures thereof as required to maintain the desired level biocatalytic activity,
    step (i) for example being conducted by contacting the spent aqueous biocatalyst with a resin capable of binding said ions, under conditions sufficient for the binding of said ions to the resin.
  8. A method of Claim 1 comprising the additional steps of
    • (i) trapping and condensing any volatile, flammable exhaust gasses escaping from the reaction vessel during the removal of the desulfurized petroleum liquid; and
    • (j) burning said gasses in a manner sufficient to provide any heat necessary to promote biocatalysis.
  9. A system for continuously desulfurizing a petroleum liquid (1) which contains organic sulfur, a significant portion of which is present in sulfur-bearing heterocyclic molecules, by treatment with an aqueous biocatalyst comprising
    • i) one or more microbial organisms expressing an enzyme that catalyzes, by a sulfur-specific oxidative cleavage reaction, the removal of sulfur from organic molecules including sulfur-bearing heterocycles, such that desulfurized organic molecules and inorganic sulfur ions are produced,
    • ii) enzymes derived from such microbial organisms, or
    • iii) mixtures of such microbial organisms and enzymes,
    said system comprising:
    • (a) a mixing chamber (9) for contacting the petroleum liquid (1) with a source of oxygen (5) under conditions sufficient to increase the oxygen tension in said liquid (1) to a level sufficient to permit biocatalysis to proceed at a desired rate, said mixing chamber (9) being connected by a line (11) to
    • (b) a vertically elongate reaction vessel (15), having a first set of injection ports (13) through which oxygenated petroleum liquid (1) is introduced from line (11), and a second set of injection ports (33) through which the aqueous biocatalyst is introduced from line (31), said first (13) and second (33) sets of injection ports being located at sites of the vessel (15) wall spatially distinct from each other and positioned appropriately for creating a countercurrent flow within a central zone (35) of the vessel (15) when the oxygenated petroleum liquid (1) and the aqueous biocatalyst ore simultaneously introduced thereto, the establishment of countercurrent flow providing sufficient mixing between the oxygenated petroleum liquid (1) and the aqueous biocatalyst for biocatalysis to proceed at the desired rate,

      further wherein the vessel (15) has a decanting port (38) located at a site of the vessel (15) will corresponding to in upper zone (37), said upper zone (37) being located above the second set of injection ports (33), such that desulfurized petroleum liquid collecting in upper zone (37) con be withdrawn through decanting port (38) to line (39),

      still further wherein the vessel (15) has a line (49) connected to a site of the vessel (15) will corresponding to a lower zone (47), said lower zone (47) being located below the first set of injection ports (13), such that spent aqueous biocatalyst collecting in the lower zone (47) can be retrieved from the vessel (15) through line (49) and regenerated, the spent biocatalyst being significantly enriched in inorganic sulfur ions; and
    • (c) means for regenerating the spent aqueous biocatalyst, said means comprising
      • i) a separation chamber (51) to which spent aqueous biocatalyst is delivered via line (49), wherein any solids (53), e.g., excess hydrocarbons or excess bacteria whether live or dead, are removed;
      • ii) at least one sulfur ion removal chamber (55) to which aqueous biocatalyst exiting the separation chamber (51) is delivered, wherein the biocatalyst is contacted with at least one agent for removing inorganic sulfur ions, e.g., an ion exchange resin to which inorganic sulfur ions bind or the salt of a divalent cation which forms an insoluble precipitate with inorganic sulfur ions; and
      • iii) a mixing chamber (29) wherein the regenerated aqueous biocatalyst exiting sulfur ion removal chamber (55) is supplemented with any fresh components needed to maintain the desired level of biocatalytic activity, e.g., additional microorganisms or medium components,
    prior to delivery of the regenerated biocatalyst through line (31) to injection ports (33) and into the reaction vessel (15), said delivery being concomitant with the delivery to the vessel (15) of oxygenated petroleum liquid (1) via injection ports (13),whereby countercurrent flow within the central zone (35) of the vessel (15) is maintained.
  10. A system of Claim 9 for use with a petroleum liquid which is capable of forming a transient or reversible emulsion with the aqueous biocatalyst, such that central zone (35) of vessel (15) is occupied by an emulsion, said emulsion being bounded above by upper zone (37) enriched in desulfurized petroleum liquid, and bounded below by lower zone (47) enriched in spent aqueous biocatalyst, the reaction vessel (15) of said system having the first set of injection ports (13) for the delivery of petroleum liquid (1) located in the vessel (15) wall at or close to the boundary between the central emulsion zone (35) and the lower spent aqueous biocatalyst zone (47), and the second set of injection ports (33) for delivery of regenerated biocatalyst located in the vessel (15) wall at or close to the boundary between the central emulsion zone (35) and the upper desulfurized petroleum liquid zone (37).
Anspruch[fr]
  1. Procédé de désulfuration en continu d'un liquide pétrolier contenant du soufre organique, une partie importante de ce soufre étant présente dans des molécules hétérocycliques porteuses de soufre, procédé qui comprend les étapes suivantes:
    • (a) mise en contact du liquide pétrolier avec une source d'oxygène, dans des conditions suffisantes pour augmenter la pression d'oxygène dans ledit liquide,
    • (b) introduction du liquide pétrolier oxygéné dans un réacteur vertical, pourvu de moyens pour faire décanter le liquide pétrolier à partir d'une région supérieure, et de moyens pour évacuer le liquide aqueux à partir d'une région inférieure, et
    • (c) introduction simultanée d'un biocatalyseur aqueux dans ledit réacteur en un point spatialement distinct du lieu d'introduction dans ce réacteur du liquide pétrolier, de manière à créer un écoulement contre-courant au sein du réacteur, l'établissement d'un écoulement à contre-courant permettant d'effectuer un mélange suffisant entre le liquide pétrolier et le biocatalyseur aqueux pour que la biocatalyse se produise à la vitesse souhaitée, ledit biocatalyseur aqueux comprenant:
      • i) un ou plusieurs organismes microbiens exprimant une enzyme qui catalyse, par une réaction de coupure oxydante spécifique pour le soufre, l'élimination du soufre à partir de molécules organiques englobant des hétérocycles porteurs de soufre, de manière à former des molécules organiques désulfurées et des ions soufre minéral,
      • ii) des enzymes provenant de tels organismes microbiens, ou
      • iii) des mélanges de tels organismes microbiens et enzymes,
    • (d) incubation avec le biocatalyseur, dans le réacteur, du liquide pétrolier oxygéné, dans des conditions adéquates pour la biocatalyse, ce qui fournit un liquide pétrolier désulfuré, dont la teneur en soufre est nettement inférieure à celle du liquide pétrolier introduit dans le réacteur, et ce qui produit en outre des ions soufre minéral,
    • (e) décantation du liquide pétrolier désulfuré, à partir de la région supérieure du réacteur,
    • (f) évacuation du biocatalyseur aqueux usé, à partir de la région inférieure du réacteur, le biocatalyseur usé étant nettement enrichi en ions soufre minéral,
    • (g) traitement du biocatalyseur aqueux usé de manière suffisante pour en éliminer une proportion importante du soufre minéral, l'activité dudit biocatalyseur étant ainsi régénérée, et
    • (h) introduction du biocatalyseur aqueux régénéré dans ledit réacteur simultanément avec l'introduction dans ce réacteur d'un liquide pétrolier nécessitant une désulfuration biocatalytique, d'une façon propre à maintenir un écoulement à contre-courant.
  2. Procédé selon la revendication 1, dans lequel les vitesses d'addition des réactifs dans le réacteur et d'évacuation des produits à partir du réacteur sont contrôlées et réglées de manière à être pratiquement équivalentes, les réactifs comprenant le liquide pétrolier à traiter par biocatalyse et le biocatalyseur aqueux régénéré, et les produits comprenant le liquide pétrolier désulfuré et le biocatalyseur aqueux usé.
  3. Procédé selon la revendication 1, dans lequel le liquide pétrolier est capable de former une émulsion transitoire ou réversible avec le biocatalyseur aqueux, grâce à quoi une zone d'émulsion apparait dans le réacteur, zone délimitée en dessus par une zone enrichie en liquide pétrolier désulfuré et en dessous par une zone enrichie en biocatalyseur aqueux usé.
  4. Procédé selon la revendication 3, dans lequel la formation ou le maintien de la zone d'émulsion est réalisée avec l'assistance d'une agitation mécanique ou hydrodynamique.
  5. Procédé selon la revendication 3, dans lequel le biocatalyseur régénéré est introduit dans le réacteur au niveau de, ou près de, l'interface entre la zone de liquide pétrolier désulfuré et la zone d'émulsion, et le liquide pétrolier à traiter par le biocatalyseur est introduit dans le réacteur au niveau de, ou près de, l'interface entre la zone d'émulsion et la zone de biocatalyseur aqueux usé.
  6. Procédé selon la revendication 1, dans lequel le biocatalyseur aqueux est soit une culture de l'espèce Rhodococcus ATCC N° 53968, soit un de ses dérivés, ou bien une enzyme obtenue à partir de Rhodococcus ATCC N° 53968 ou d'un de ses dérivés, et l'enzyme peut être fixée à un substrat.
  7. Procédé selon la revendication 1, dans lequel le biocatalyseur est régénéré à l'étape (g) par
    • i) élimination d'un nombre important d'ions soufre minéral du biocatalyseur usé, et
    • ii) recharge de nutriments et/ou d'organismes microbiens, d'enzymes ou de leurs mélanges en fonction des besoins, afin de maintenir le niveau souhaité d'activité biocatalytique, l'étape (i) étant p.ex. réalisée par mise en contact du biocatalyseur aqueux usé avec une résine capable de fixer lesdits ions, dans des conditions permettant de fixer ces ions à la résine.
  8. Procédé selon la revendication 1, comprenant en outre les étapes consistant à:
    • (i) piéger et condenser tout gaz de combustion volatil et inflammable, s'échappant du réacteur lors de l'évacuation du liquide pétrolier désulfuré, et
    • (j) faire brûler lesdits gaz suffisamment pour fournir la chaleur nécessaire à favoriser la biocatalyse.
  9. Système pour la désulfuration en continu d'un liquide pétrolier (1) contenant du soufre organique, une partie importante de ce soufre étant présente dans des molécules hétérocycliques porteuses de soufre, par traitement avec un biocatalyseur aqueux comprenant:
    • i) un ou plusieurs organismes microbiens exprimant une enzyme qui catalyse, par une réaction de coupure oxydante spécifique pour le soufre, l'élimination du soufre à partir de molécules organiques englobant des hétérocycles porteurs de soufre, de telle sorte que des molécules organiques désulfurées et des ions soufre minéral se forment,
    • ii) des enzymes provenant de ces organismes microbiens, ou
    • iii) des mélanges de ces organismes microbiens et d'enzymes,
    ledit système comportant:
    • a) une chambre de mélange (9) pour la mise en contact du liquide pétrolier (1) avec une source d'oxygène (5) dans des conditions suffisantes pour augmenter la pression d'oxygène dans ledit liquide (1) jusqu'à un niveau permettant de réaliser la biocatalyse à une vitesse souhaitée, ladite chambre de mélange (9) étant reliée par une conduite (11) à
    • b) un réacteur vertical (15) présentant une première série d'orifices d'injection (13) à travers lesquels est introduit du liquide pétrolier oxygéné (1) à partir de la conduite (11), et une seconde série d'orifices d'injection (33) à travers lesquels est introduit le biocatalyseur aqueux à partir de la conduite (31), lesdites première (13) et deuxième (33) séries d'orifices d'injection se trouvant en des points de la paroi du réacteur (15) spatialement distincts l'un de l'autre et placés de manière appropriée pour créer un écoulement à contre-courant au sein d'une zone centrale (35) du réacteur (15) quand le liquide pétrolier oxygéné et le biocatalyseur aqueux sont simultanément introduits dans ledit réacteur, l'établissement de l'écoulement à contre-courant permettant d'effectuer un mélange suffisant entre le liquide pétrolier oxygéné (1) et le biocatalyseur aqueux pour que la biocatalyse se produise à la vitesse souhaitée,

      le réacteur (15) possédant en outre un orifice de décantation (38) situé en un point de la paroi du réacteur (15) correspondant à une zone supérieure (37), ladite zone supérieure (37) étant située au-dessus de la seconde série d'orifices d'injection (33), de telle sorte que le liquide pétrolier désulfuré recueilli dans la zone supérieure (37) puisse être soutiré par l'orifice de décantation (38) dans la conduite (39),

      le réacteur (15) comportant également une conduite (49) reliée à un point de la paroi du réacteur (15) correspondant à une zone inférieure (47), ladite zone inférieure (47) étant située au-dessus de la première série d'orifices d'injection (13), de telle sorte que le biocatalyseur aqueux usé se rassemblant dans la zone inférieure (47) puisse être soutiré du réacteur (15) par la conduite (49) et régénéré, le biocatalyseur usé étant nettement enrichi en ions soufre minéral, et
    • c) des moyens pour régénérer le biocatalyseur aqueux usé, lesdits moyens comprenant:
      • i) une chambre de séparation (51) alimentée en biocatalyseur aqueux usé par la conduite (49), dans laquelle tous les solides (53), p.ex. hydrocarbures en excès ou bactéries en excès, vivantes ou mortes, sont séparés,
      • ii) au moins une chambre d'élimination des ions soufre (55) alimentée en biocatalyseur aqueux sortant de la chambre de séparation (51), dans laquelle le biocatalyseur est mis en contact avec au moins un agent d'élimination des ions soufre minéral, p.ex. une résine échangeuse d'ions, auquel les ions soufre minéral se fixent, ou bien le sel d'un cation divalent qui forme un précipité insoluble avec les ions soufre minéral, et
      • iii) une chambre de mélange (29) dans laquelle le biocatalyseur aqueux régénéré sortant de la chambre d'élimination des ions soufre (55) est additionné de n'importe quel constituant frais nécessaire au maintien du taux souhaité d'activité biocatalytique, p.ex. des micro-organismes ou constituants du milieu supplémentaires, avant que ledit biocatalyseur régénéré ne soit, par la conduite (31), amené aux orifices d'injection (33) et, de la, dans le réacteur (15), cet apport étant concomitant avec l'apport au réacteur (15) du liquide pétrolier oxygéné (1) par l'intermédiaire des orifices d'injection (13), un écoulement à contre-courant étant ainsi maintenu au sein de la zone centrale (35) du réacteur (15).
  10. Système de la revendication 9, utilisable avec un liquide pétrolier capable de former une émulsion transitoire ou réversible avec le biocatalyseur aqueux, de telle sorte que la zone centrale (35) du réacteur (15) soit occupée par une émulsion, ladite émulsion étant délimitée en dessus par la zone supérieure (37), enrichie en liquide pétrolier désulfuré, et en dessous par la zone inférieure (47), enrichie en biocatalyseur aqueux usé, le réacteur (15) dudit système présentant une première série d'orifices d'injection (13), pour l'introduction du liquide pétrolier oxygéné (1), situés dans la paroi du réacteur (15) au niveau de, ou près de, l'interface entre la zone d'émulsion centrale (35) et la zone inférieure (47) du biocatalyseur aqueux usé, et une seconde série d'orifices d'injection (33), pour l'introduction du biocatalyseur régénéré, situés dans la paroi du réacteur (15), au niveau de, ou près de, l'interface entre la zone d'émulsion centrale (35) et la zone supérieure (37) du liquide pétrolier désulfuré.






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