US 2975103 A
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March 14, 1961 l s uM 2,975,103
BACTERIOLOGICAL DESULFURIZATION OF PETROLEUM Filed April 6, 1956 CONTACTING 4 SE TTLER COLUMN FIG.'I
FRACTIONATOR SE PARATOR CONTACTING VESSEL FIG-2 lsidor Kirshenbaum Inventor By M (2M Attorney United States Patent BACTERIOLOGICAL DESULFURIZATION OF PETROLEUM Isidor Kirshenbaum, Union, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware Filed Apr. 6, 1956, Ser. No. 576,651
8 Claims. (Cl. 195-3) This invention relates to a method for desulfurizing crude petroleum oil, petroleum hydrocarbon fractions, and the like. More particularly it concerns a desulfurization method involving the use of aerobic bacteria which convert organic sulfur compounds to inorganic sulfur compounds, the latter then being removed from the crude oil by chemical means.
This application is a continuation-in-part of applica tion Serial No. 232,909, filed June 22, 1951 and now abandoned.
Crude petroleum oil is characterized, in some cases, by the presence of objectionable quantities of sulfur compounds which must be removed or substantially reduced in amount, depending on the intended uses of the final products, as for example to eliminate any corrosive effect of the final products. Certain sulfur compounds are further objectionable in such final products as fuels for internal combustion engines in that they reduce the efiiciency of anti-knock compounds such as tetraethyl lead and will, when used alone, reduce the octane number of the fuel. Many sulfur-containing crudes cannot be handled by conventional refining methods because of the corrosive effect of the sulfur compounds. In the refining of such crudes either to remove the sulfur compounds or reduce them to unobjectionable amounts, it is frequently necessary to modify the usual refining steps as well as to use additional steps. Such process modifications require extensive apparatus, involve corrosion problems, and add materially to the cost of the final products.
In accordance with the present invention microorganisms are employed in a desulfurization process which does not require extensive equipment or complicated refining steps. While it is known that certain microorganisms will attack sulfur compounds and effect their conversion to easily removable sulfur compounds such as hydrogen sulfide and water-soluble sulfur compounds, procedures along the line of using such microorganisms in crude oils to remove and reduce the sulfur compounds therein have not been utilized, apparently because there has up to now been known no attractive method for economically utilizing these organisms in a practical plant process. 7 7
It is therefore the main object of this invention to provide an economically feasible process for the utilization of microorganisms in desulfurizing crudes or fractions thereof.
It is a further object of the invention to provide a method for increasing and controlling the rate of desulfurization when using microorganisms for this purings wherein:
following specification and to the accompanying draw- H as Amberlite resins of the MB series.
Patented Mar. 14, 1961 ice Figure 1 represents one embodiment of this invention in diagrammatic form in which the desulfurization is carried out in a packed column; and V Figure 2 diagrammatically represents another embodiment of this invention in which the desulfurization is carried out by means of a slurry operation.
With specific reference to Figure 1, a sulfur-containing feed enters contacting column 2 through line 1. Column in through line 10. The mixed streamsmove up column 2 at a rate such that the required degreeo-f desulfurization is attained by the time the streams leave the column by line 3. More than one column may be used in series and/or parallel. Exit gases (air, CO etc.) leave the system through line 11 via a series of bafies and condensers, not shown. The liquid streams leaving the' column through line 3 are led to settling stage 4 wherein the mixture is separated into an oil and an aqueous culture layer. Any entrapped gases are liberated and leave the system through line 12. The oil layer is removed via line 9, washed (if necessary) free of sulfate, etc. and
sent to a fractionator (not shown).
In order to maintain the proper pH and to remove'the sulfate formed during the desulfurization, the aqueous culture layer is regenerated. To accomplish this, water containing a basic precipitant such as OaO, BaO or the hydroxide of either may be added via line 5. This aqueous solution or slurry mayalso contain added nutrient (if desired). Since the number of bacteria has increased excessively during the desulfurizat-ion process, excess bacteria are removed via line 8. The lime or barium oxide added via line'5 precipitates the sulfate ascalcium sulfate or barium sulfate, which forms a slurry the major portion of which is removed through line 7, although some of it will leave the settler through line 8 along with the excess bacteria.
An alternate procedure is to regenerate the aqueous culture by circulating a portion of the aqueous layer through an ion exchange resin such as one of the Amberlite resins produced by the Rohm & Haas Company and thus remove the sulfate and adjust the pH and salinity prior to recirculation of the bacterial culture to column 2 through line 6. Anion exchange resins such as Amberlite IRA410, IR-45 or Amberlite IRA-400 and IRA-410 may be used to adjust the sulfate content of the aqueous layer. Excess acidity can be removed by cation exchange resins such as Amberlite IR- or-IRC-SO. Sometimes it is convenient to use a monobed resin such A surface active agent may be added via line 1 or 6, if desired. r r.
In desulfurization of high sulfur crudes, economical operation is often attained by using the resin exchange media in the form of packing for column 2. This type of operation is especially efficient in that it enables the pH and anion concentration of the mixture to be maint-ained at their optimum throughout the entire process. In this type of process the resin exchange packing in column 2 may be periodically regenerated by the procedures established for the particular resins employed.
Referring now to 'Figure 2, there is shown another embodiment of the invention employing a slurry operation. The feed of sulfur-containing hydrocarbons that is to be treated enters the contacting chamber or vessel 22 through line 21. A suitable bacterial culture, impregnated on a carrier such as a neutral clay or alumina, is added to vessel 22 through line 23 as a water slurry. The resulting slurry mixture of feed and culture is agitated in the contacting chamber 22 by a stirrer or other means known in the art. Agitation is also maintained by blowing a stream of air or other oxygen-containing gas such as flue gas through the slurry via line 24. The added gas as well as gases formed during the desulfurization escape through line 25. Other agents needed to control the treatment, such as materials for adjusting the pH in the mixture, may be added through line 44. The extent and rate of desulfurization are controlled by the temperature of the slurry and the residence time of the slurry in vessel 22. After desulfurization, the slurry is conducted through line 26 from the vessel 22 into a separation unit 27, which may contain a settling zone, rotary filter, etc. The separated oil phase is led by means of line 29 into a suitable fractionator 30 from which desired fractions are removed through lines 32, 33, 34 and 35. Entrapped gases, such as air or CO are released from the separator by means of line 31.
The oil removed by line 29 is of particularly high quality, as salts and other suspended matter have been removed during the separation step. Moreover the oil is richer in C hydrocarbons (and compounds in the gasoline boiling range) than is the feed since the bacteria used do not appreciably attack hydrocarbons below decane. Because not all of the sulfur compounds are desulfurized by the bacteria with equal ease, with some crudes it may be necessary to recycle some of the product to the feed entry line 21 via line 36. Depending upon the particular hydrocarbon feed being treated, the recycle rate may range from 15 percent to as much as 50 percent of the oil phase leaving separator 27. Preferably the operation is arranged for a recycle of 20 to 30 percent of the oil phase from the separator. A particularly preferred procedure is to recycle only those streams from the fractionator 30 which are decidedly rich in sulfur. This may be done for example by conducting a portion of the stream from line 35 to line 36 through line 37.
The water phase containing carrier and bacteria leaves the separation unit 27 via line 28 and is led into the regeneration unit indicated at 38. In order to maintain proper bacterial activity some of the used material is removed through line 39 for rejection or reculturing and re-impregnation. Make up carrier, and/ or bacterial culture is added by means of line 40. Water as well as surface active reagents and/or organic nutrient may be added via line 41. The pH and salinity of the slurry are adjusted in the regenerator system 38, for example by adding a sulfate precipitant through line 41 and/or by the use of ion exchange resins as was described in connection with Figure 1. Precipitated sulfates are removed through line 42. The regenerated culture slurry is then pumped through line 43 to entry line 23 and thence into vessel 22.
The microorganisms employed in carrying out the process of this invention may be obtained from mixtures such as occur in nature, preferably where crude oil or petroleum products have been stored or spilled. They may be found in oil-soaked soils, water from the bottom of storage tanks in which crude oil or petroleum products have been stored, and the water of petroleum separation tanks and sedimentation ponds. They also occur in sea water, marine bottom deposits, garden and field soils, industrial waste and sewage disposal waters and like waste material. Such mixtures contain an undetermined number of different species of microorganisms both of the aerobic and anaerobic types. Use can be made of any of such natural mixtures, or combinations thereof, which when propagated under laboratory conditions will yield a mixture of organisms of the aerobic type capable of converting the sulfur compounds of the substance to be treated, it being understood that the invention is not limited to the use of any particular mixture, class or species of microorganisms except that it or they be capable of converting the sulfur compounds to easily removable form. Microorganisms from animal, marine, and vegetable sources can likewise be used as well as microorganisms from waste materials such as sewage.
Although the temperature may in some instances be varied over a wider range, the preferred operating range for high activity is from about 65 F. to about 105 F., maximum activity occurring in the 85 F. to 95 F. temperature range. The proportion of water to oil present during the desulfurization is relatively small, for example from 0.01 to 1 volume of water per volume of hydrocarbon, a preferred range being 0.1 to 0.2 volume of water per volume of hydrocarbon. The use of such small proportions of water is highly advantageous from an economical standpoint. The optimum pH depends upon the bacteria used and generally is in the range 6.3-8.5. The salinity of the culture should also be adjusted depending upon the species of bacteria used, and in general falls in the range of from zero to 1.5 percent by weight, although some bacteria are able to grow at a salinity of 3.5 weight percent or more. The activity of the bacteria can also be controlled to an appreciable extent by including nutrient material in the water phase.
Surface active agents, such as alkyl sulfates, e.g. lauryl sulfate, alkylatcd aromatic sulfonates, sodium petroleum sulfonates, sodium aryl alkylpolyether sulfonates, aryl alkylpolyether alcohols, fatty acid soaps of the ethanolamines, pentaerythritol monostearate, alkyl sodium sulfosuccinic acid, and the like, can be used to increase contact between the oil and the water layer. Generally the amount of surface active agent used will be in the range of from 0.05 to 0.5 weight percent, based on the water phase, and will preferably be in the range of 0.1 to 0.2 percent. It is preferable to use sulfur-containing agents such as the sodium aryl alkyl polyether sulfonates available under the trade-name of Triton, the alkyl sodium sulfosuccinic acids sold under the trade-name Aerosol OT, alkylatcd aromatic sulfonates, etc. As the bacteria eventually consume the sulfur-containing agents they destroy the detergent properties of the added agent and thus permit an easy subsequent separation of the oil and water layers. High concentrations of nutrient may also be obtained in the water phase by supplementing the dissolved (and/or emulsified) oil with a sugar such as glucose, starch, fats, fatty acids, etc. The use of fatty acids as nutrient is of special interest when the refinery has access to the fatty acid stream from a hydrocarbon syn thesis plant. Oxygenated compounds such as oxo acids from an oxo plant may also be used.
The rate of reaction of the bacteria with the sulfurcontaining molecule is also increased by addition of small amounts of protein to the water layer. As little as l p.p.m. of peptone will accelerate the rate of reaction. The rate of desulfurization is also increased by increasing the contact between the oil and the bacterial solution by the use of a packing material such as glass beads, helices, Raschig rings, bauxite granules, etc. This increase is especially marked when the aqueous layer contains less than ppm. of organic material.
Under optimum reaction conditions employing the method of this invention, over 90% of the sulfur may be removed under aerobic conditions in less than 10 minutes contact time. The desulfurization is carried out preferably using a slurry type operation or by concurrent flow through a packed column. Any other method of operation which results in intimate contact between the oil and bacterial phases may be used.
Among the bacteria that may be employed in the present invention are thiophyso volutans, thiobacillus thiaoxidans and tlziobncillus thioparus.
The following are specific examples of methods for carrying out the process of the present invention.
EXAMPLE I A culture of Thiobacillus thio-oxidans is grown in a tank of nutrient comprising water containing the following ingredients:
Also, trace amounts of Cu, Fe, Mn and Zn.
The pH of the nutrient is maintained at 4 and the temperature is maintained at about 90 F. to ensure the growth of bacteria. The nutrient medium is placed in contact with a body of hydrocarbon having a volume at least 15% of that of the nutrient solution, about 5% of the hydrocarbon comprising a mercaptan such as ethyl mercaptan. After 4 days the culture is used to impregnate an activated alumina that has been pre-calcined for 4 hours at 900 F. The impregnation of the alumina is carried out by mixing the materials in the ratio of 100 grams of alumina with 6070 cc. of the culture. If necessary, extraneous Water may be added to make a pumpable slurry. The culture-impregnated alumina is then employed for the sweetening of a light gas oil using the procedure described above in connection with Figure II. Specifically, a gas oil having the following characteristics is employed:
A.S.T.M. DISTILLATIO'N: F.
I.B.P. 436 over 521 50% over 595 90% over 652 F.B.P. 682
The gas oil has a natural sulfur content of 1.1%.
Referring to Figure 2, the gas oil enters the contacting vessel 22 through line 21 and therein encounters the slurry of bacteria culture and alumina that enters the vessel through line 23. The proportion of materials entering the vessel is approximately 4 to 5 volumes of oil to one volume of slurry. Although, as stated, the pH is preferably maintained at about 4 during the growth of the culture, it is preferred that the contacting of the culture with the sulfur-containing hydrocarbons that are being treated be conducted at a pH of about 6.5. The pH is adjusted by adding calcium carbonate to the slurry in the vessel through line 44, the adjustment being controlled by using a pH meter. Rate of flow of the materials through the contacting vessel is maintained so as to allow sufficient contact time to reduce the sulfur content of the gas oil to less than 0.3 percent. As previously described in connection with Figure 2, the mixture leaving the contacting vessel is conducted to the separator, and the separated aqueous layer is sent on to the regenerating vessel 38. Sufiicient lime is added to the aqueous material through line 41 to precipitate the sulfates as calcium sulfate. The rate of addition of the lime is determined by periodic sampling of the material in the regenerator 38. The pH of the regenerated culture is adjusted to 6.5 by adding citric acid and the culture is then returned to the contacting vessel 22 as previously described.
EXAMPLE II In a manner similar to that described in Example I an activated alumina is impregnated with a culture of Thiophyso volutans that has been grown at a pH of about 7.6 to 7.8 and a temperature of 95 F. The slurry is mixed with the sulfur-containing gas oil in vessel 22 in about the same proportions as in Example I. A slight adjustment in pH to about 7.5 is effected by adding K HPO and citric acid to the mixture in vessel 22 through line 44. Separation and regeneration are con ducted in essentially the same manner as in Example I,
but more complete desulfurization is elfected byrecycling through line 36 about 25 percent of the oil removed from the fractionator through line 35.
EXAMPLE 111 An aqueous culture of Thiobacillus thioparus grown at a temperature of -F. and a pH of 7.5 is introduced into a contacting column of the type described in connection with Figure l, the column containingcalcined bauxite as packing material. About 0.1 weight percent of sodium lauryl sulfate is added to the culture as it enters the column, to improve the efficiency of contact between the oil and Water phases. The feed rate of the entering stream of culture is adjusted to be about one-tenth of the volume of sulfur-containing gas oil entering the column through line 1. The rate of flow of the materials is adjusted to provide sufficient residence.
time to reduce the sulfur content from its original value of 1.1 to 1.2% to 0.25% or less.
As the contacting step is preferably conducted at the same pH, 7.5, as wasmaintained during culture, little or no adjustment in pH will be required although barium hydroxide or K HPO' or acetic acid or citric acid may be added if slight adjustments are found necessary. The sulfates produced by the bacteria are precipitated out in the settler 4 by adding barium hydroxide through line 5. The regenerated culture is then recycled back to the contacting column through line 6, along with additional fresh culture if necessary.
The foregoing description does not by any means cover all of the possible uses of this invention nor all of the forms which it may assume, but serves to illustrate its fundamental principles and the manner in which it can be utilized. It is obvious that changes in the details may be made without departing from the spirit and scope of this invention as defined in the appended claims.
What is claimed is:
1. In a process for desulfurizing hydrocarbons containing organic sulfur compounds, the steps including: contacting said hydrocarbons with an aqueous culture of aerobic bacteria adapted to convert organic sulfur compounds to inorganic sulfur compounds in the presence of oxygen, supplying an oxygen-containing gas to said hydrocarbons during the step of contacting with said bacteria, said contacting of the hydrocarbon with said aqueous culture of aerobic bacteria being carried out.
in the presence of a sulfur-containing surface-active agent which is consumed by said bacteria during said contacting, separating said aqueous culture from said hydrocarbons, contacting said aqueous culture with an electrolyte having an afiinity for sulfate 'ions, whereby said aqueous culture is regenerated by removal of inorganic sulfur compounds therefrom, and contacting the regenerated aqueous culture with additional hydrocarbons containing organic sulfur compounds.
2. The process defined by claim 1 in which the said electrolyte is a compound selected from the class consisting of calcium oxide, barium oxide, calcium hydroxide, and barium hydroxide.
3. The process defined by claim 1 in which the said electrolyte constitutes an anion exchange resin.
4. The process defined by claim 1 in which the said contact of hydrocarbons with the aqueous culture is bacillus thiopm'us, Thiophyso volutans and Thiobacillus thio-oxidans.
7. The process defined by claim 8 including ,the step of recycling to the contacting zone a portion of the hydrocarbons obtained from said separation zone.
8. In a process for desulfurizing hydrocarbons containing organic sulfur compounds, the steps including; contacting a stream of said hydrocarbons in a contacting zone with a stream comprising an aqueous culture of .aerobic bacteria adapted to convert organic sulfur compounds to inorganic sulfur compounds in the presence of oxygen, passing a stream of an oxygen-containing gas through said contacting zone, said contacting of the streams being carried out in the presence of a sulfur-containing surface-active agent which is consumed by said bacteria during said contacting, conducting a mixture of hydrocarbons and aqueous culture from said contacting zone into a settling zone, separating hydrocarbons from aqueous culture in said separating zone, conducting separated aqueous culture from said settling zone into a regenerating zone, contacting said aqueous culture in said regenerating zone with an electrolyte having an affinity for sulfate ions, whereby the said aqueous culture is regenerated by removal of inorganic sulfur com pounds therefrom, and recycling regenerated aqueous culture to the contacting zone.
References Cited in the file of this patent UNITED STATES PATENTS 2,367,803 Schindler Jan. 23, 1945 2,413,278 Zobell Dec. 24, 1946 2,521,761 Strawinski Sept. 12, 1950 2,574,070 Strawinski Nov. 6, 1951 OTHER REFERENCES