US3761398A

US3761398A - Method of treating sulfur containing mineral oils to reduce their sulfur content

Info

Publication number: US3761398A
Application number: US00109892A
Authority: US
Inventors: E Munekata
Original assignee: Individual
Current assignee: EIJI MUNEKATA JA; EISUKE MUNEKATA JA
Priority date: 1970-02-16
Filing date: 1971-01-26
Publication date: 1973-09-25
Anticipated expiration: 1990-09-25
Also published as: DE2105710A1; SE392727B; NL7101755A; FR2080532B1; NL141926B; GB1292426A; SU488420A3; FR2080532A1; CA954465A

Abstract

A METHOD OF TREATING SULFUR-CONTAINING MINERAL OILS TO REDUCE THEIR SULFUR IS DISCLOSED IN WHICH THE OIL IS CONTACTED WITH SUPERHEATED WATER, FOR EXAMPLE, BY COUNTER-CURRENT EXTRACTION TECHNIQUE.

Description

Sept. 25, 1973 EL MUNEKATA ET AL 3,761,398

METHOD ,OF TREATING SULFUR-CONTAINING MINERAL OILS TO REDUCE THEIR SULFUR CONTENT Filed Jan. 26, 1971 I2 3 LT. 41 1 fr up United States Patent G 3,761,398 METHOD OF TREATING SULFUR-CONTAINING MINERAL OILS TO REDUCE THEIR SULFUR CONTENT Eiji Munekata, Tokyo, and Eisuke Munekata, Toyonaka, Japan; said Eisuke Munekata assignor to said Eiji Munekata Filed Jan. 26, 1971, Ser. No. 109,892 Claims priority, application Japan, Feb. 16, 1970, 45/ 12,664; May 28, 1970, 45/45,179 Int. Cl. Cg 17/08, 29/08 US. Cl. 208-408 ABSTRACT OF THE DISCLOSURE A method of treating sulfur-containing mineral oils to reduce their sulfur content is disclosed in which the oil is contacted with superheated water, for example, by counter-current extraction technique.

BACKGROUND TO THE INVENTION Consumption of petroleum products as fuel has been increasing steadily each year, accompanied by such public nuisance as air pollution as a consequence. To fight against this public nuisance the stress has been placed more and more on the removal of sulfur contained in such fuel oils, including petrol, kerosene and light oils as well as in crude oil and heavy oils.

There are a large number of different kinds of sulfur compounds present in mineral oils, ranging from simple compounds such as hydrogen sulfide to complex mercaptanes, sulfides, di-sulfides, thiophenes, etc. Prior processes for reducing the sulfur content of mineral oils have tended to include different processing steps for removing the different kinds of sulfur compounds. Such prior processes have, therefore, been complicated and expensive and a need exists for a simple and more effective process.

It is therefore the primary object of the present invention to provide a novel method for reducing the sulfur content of mineral oil which is less complex and expensive than traditional processes.

An additional object of the present invention is to provide an extraction apparatus suitable for carrying out the novel method.

Further objects and advantages of the invention will become apparent from the following description.

SUMMARY OF THE INVENTION It has been discovered by the inventors that a large number of different kinds of sulfur compounds present in mineral oils can be removed by extraction with superheated water, i.e. water maintained at superatmospheric pressure and having a temperature higher than 100 C.

Although the sulfur compounds contained in mineral oils can be dissolved in superheated water, the amount of the dissolved sulfur compounds is governed by the law of distribution between mineral oils and superheated water. By the law of distribution a higher concentration of sulfur compounds will dissolve into the oil phase than in the water phase. The absolute amount of sulfur compounds dissolved into water, however, increases if the amount of water is increased in proportion to the amount of oil. The total amount of dissolved sulfur compounds is further increased if the oil and water are brought in contact counter-currently.

Extraction towers may be used in an industrial scale. However, it may be more effective to use extraction vessels which are connected in series, and operate the method by a counter-current extraction of the oil with. superheated water. Incidentally, superheated water and hot mineral oil do not easily mix with each other. It is there- 5 Claims 3,761,398 Patented Sept. 25, 1973 fore essential to adjust the fluidity of both liquids, so that the superheated water and hot mineral oil intimately contact each other. When the extraction is carried out with superheated water in an extraction tower, it is essential that there is a difference in specific gravity (density) between the two liquids, so that there is adequate countercurrent flow. For this purpose the inventors recommend two methods, i.e. either to adjust the specific gravity of the superheated water by addition of water soluble substances and/or by application of colloidal solution or to adjust the specific gravity of the sulfur containing mineral oil by application of distillates and/or by addition of heavier or lighter oil, as required. At any rate, the adequate difference in the specific gravity is vitally important for the extraction process to be performed satisfactorily in the extraction tower. In this extraction there is a close relationship between the specific gravity and the fluidity. When the difference in fluidity between the superheated water and the sulfur containing oil is small, the difference in specific gravity can be small. And when said difference in large, it is necessary to increase the difference in specific gravity. Should the difference in the specific gravity be too large, both superheated water and sulfur containing oils merely run against each other without coming into intimate contact with each other, with consequent insufficient extraction. If, on the other hand, the difference in the specific gravity is too small, then there will be no counter-current contact of sulfur-containing mineral oils with superheated water and therefore effective superheated water extraction becomes impossible.

It is difficult for superheated water to come into intimate contact with sulfur-containing mineral oil, therefore migration of sulfur compounds from the mineral oil into the superheated water does not take place unless the superheated water and sulfur-containing mineral oil have a substantially similar fluidity. It is a common sense in liquid-liquid extraction to resort to agitation and other means similar thereto in Order to obtain a good mutual dispersion. To control the fluidity, it might also be neces sary to adjust the relative proportions of distillates in the sulfur-containing oils. For instance, sulfur-containing heavy oil and desulfurized light oil can be mixed in order to prepare a sulfur-containing mineral oil having an ade quate fluidity for the superheated water extraction. The oil mixture after treatment can be separated into heavy oil and light oil by distillation in order to achieve the object of heavy oil desulfurization.

To explain the extraction condition, the inventors have decided to adjust the relative specific gravities of the mineral oil and superheated water for achieving satisfactory counter-current flow, and the inventors find no contradiction as to the explanation on counter-current extraction from the viewpoint of relative fluidity, because what the specific gravity and the fluidity mean here are compatible. The inventors are of an opinion that the adjustrnent of the difference of the specific gravity is a basically important condition for the execution of superheated water extraction based on the counter-current contact technique. It is also a fact that liquid with a small specific gravity has a high fluidity, while a liquid with a large specific gravity has a low fluidity as far as petroleum mineral oils are concerned, within the range of this invention. Therefore, the inventors lay greater weight on the specific gravity of the mineral oils and the superheated water in determining the working conditions of the method and less weight on fiuidities of the liquids.

In order to adjust the difference between the relative specific gravities of sulfur-containing oils and of the superheated water or aqueous solution (neutral, acidic or basic solution), it is convenient to adjust firstly the concentration of additives to the superheated water. For this purpose it is recommended to apply inorganic or organic solutions, and/or suspensions or emulsions, namely colloidal solution. For instance, the use of such solutions as salt solution, or a solution of iron sulphate in which iron hydroxide is suspended can be recommended. Howver, it is better to employ water itself, if possible, because a Water solution generally has a lower dissolving power than water itself. If the required difference of the specific gravity is found to be difficult to obtain, when superheated water is used, it is recommended to facilitate the adjustment of the difference of the specific gravity by appropriate adjustment of the specific gravity of the sulfur containing oil. The inventors recommend use of superheated water itself for treatment of sulfur-containing lighter oils and use of superheated water solutions for the treatment of sulfur-containing heavier oils. The changes in the specific gravities of mineral oils and water with temperature are not always parallel. For example, the specific gravity of superheated water falls more rapidly with rising temperature than that of mineral oils; above a certain temperature, water has a specific gravity which is smaller than that of mineral oils. Thus, at the higher temperatures it becomes necessary to use water solutions.

The temperature used in the superheated water extraction method according to this invention is more than 100 C. As the preferable range of this temperature is 100 to 350 C., both sulfur-containing mineral oil and superheated water must be kept at this temperature. The extraction tower must be maintained at a pressure much higher than the total pressure of both partial pressure of vapor of water and partial pressure of the vapor of mineral oil. By so doing, the boiling of either water or oil inside the extraction tower can be supressed, which otherwise would disturb the regular counter-current flow of the liquids. The quantitative relations between the sulfur-containing mineral oils and superheated water or superheated water solution, the relations between differences of specific gravities as well as the temperature conditions for the extraction, must be determined for each experiment independently.

As it is apparent from the above stated description, the desulfurization of sulfur-containing mineral oils utilizing the dissolving power of superheated water in respect of sulfur compounds is proved by the description of autoclave experiment in Ex. 1. However, an extraction equipment is required to carry out the desulfurization of sulfur-containing oils with superheated water on an industrial scale. This equipment must have such function as to enable sufficient mutual dispersion of mineral oil and of superheated water. The equipment must be made of corrosion proof material in order not to be affected by sulfur-containing mineral oil and superheated water, particularly superheated water solution which contains neutral, acidic or basic substances. In order to have a thorough mutual dispersion, filling materials must be charged into the extraction tower, or agitators must be installed in the extraction tower or in a multiple of extraction vessels, connected in series. The regular and constant counter-current flow of the superheated water and sulfur-containing oil in the extraction equipment will be considerably prevented if boiling of either mineral oil or superheated water takes place. It must also be so arranged that a pressure much higher than the total pressure of superheated water vapor and mineral oil vapor, must be introduced into the extraction equipment. The inventor also recommends recovery of the pressure of the superheated water and mineral oil being discharged from the extraction equipment to save the power necessary for the introduction of mineral oil and superheated water under such an excessive pressure.

DETAILED DESCRIPTION OF THE DRAWING A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawing. The drawing illustrates a case whereby the extraction is made not by a multiple of extraction vessels but by an extraction tower. Reference numeral 1 indicates a superheated vertical extraction tower, resistant to a high pressure, having an inlet 2 for the superheated water at its upper part, and an inlet 3 for hot mineral oil at its lower part. Tower 1 also includes an outlet 4 of the desulfurized mineral oil at its top, and an outlet 5 for the sulfur-containing superheated Water at its bottom. The superheated water extraction tower 1 is either filled with inert filler materials or has an agitating mechanism inside in order to sufficiently bring both superheated water and the mineral oil, which is dispersed in the superheated water, in counter-current contact. Reference numeral 10 indicates a water tank and reference numeral 11 a mineral oil tank containing the mineral oil which is to be treated. Tanks 10 and 11 are connected via pressure pumps 8 and 9 to the tower 1. These pumps are connected further to the interior of the superheated water extraction tower 1 via a heat exchanger 7 and heater 6. An outlet 4 for the desulfurized oil and an outlet 5 of the sulfur-containcontaining superheated water are connected by pipes via heat exchanger 7 to the pressure recovery mechanism attached to

pumps

9 and 8. These two outlets 4 and 5 are so arranged that they are connected to desulfurized oil receiving tank 13 and sulfur-containing water receiving tank 12. The temperature of the sulfur-containing water drops in the heat exchanger. Said sulfur-containing water is then led into the receiving tank 12. As the sulfur compounds cannot exist in dissolved state in water or water solution according to the temperature depression, the sulfur compounds are separated from aqueous phase, and exist as another liquid phase, even if said sulfur compounds be in a liquid state.

It can be seen that water or water solution and sulfurcontaining mineral oil stored in the water tank 10 and the oil tank 11 respectively will be fed into the heat exchanger 7 by the

pumps

8 and 9, where they are pre heated as the result of the heat exchange with the desulfurized mineral oil and sulfur-containing superheated water or sulfur-containing water solution which were already treated in the extraction tower 1. They will then be forwarded to the heater 6 where they are heated to the appropriate temperature for the treatment and fed into superheated water extraction tower 1 through superheated water inlet 2 and hot mineral oil inlet 3 at a pressure determined by the pressure pumps 8 and 9. Superheated water or superheated water solution as well as hot mineral oil fed into the extraction tower 1 are brought into counter-current contact, extracted, treated and recovered through the outlets 4 and 5, wherefrom they are conveyed via heat exchanger 7 to the desulfurized oil receiving tank 13 and the sulfur-containing water receiving tank 12 to be stored. Thus, the desulfurized mineral oil is obtained.

It will be appreciated that the operation pressure of the

pumps

8 and 9 must be maintained at a level which is high enough to suppress boiling of either the water or the oil. The pressure required is the grand total of the partial pressure of superheated water and the partial pressure of hot mineral oil found in the extraction column, plus the pressure of the pump required for transporting the fluid in the equipment, plus the pressure for pressurizing the extraction tower as a safety measure in order to prevent bumping. As such high pressure is employed in the extraction, one of the features of this invention is to recover the energy possessed by the pressure of the fluids discharged from the tower. For this reason a recovering apparatus is attached to the pressure pumps 8 and 9 in order to recover the pressure of desulfurized mineral oil and sulfur-containing superheated water or sulfur-containing superheated water solution coming from the outlets 4 and 5 and flowing out of heat exchanger 7. The recovered heat energy pre-heats the raw materials which will become superheated water or superheated water solution and hot mineral oil to be fed into the extraction tower and thereby saves the heat. The pressure energy recovering apparatus is installed in the pressure pumps 8 and 9, and takes the form of, for example, a turbine operated by the pressure of the fluids discharged from the tower. The turbine may be geared to the motors of the

pumps

8 and 9 for the purpose of saving the energy required by the motors of the pressure pumps. In order to economize electric power for the pressure pumps, it is possible to utilize said recovered pressure for electric power generation by driving a power generator separately installed.

The following examples are given to illustrate the operation of the method of the present invention.

EXAMPLE 1 A heavy oil with sulfur content 3.4% and specific gravity 0.97 was charged into an autoclave together with water in an amount equal to twice that of said heavy oil. After agitation for about 20 minutes at a temperature of 300 C., the contents were allowed to settle, so that the water phase separated from the oil phase and the two phases were separated. At this time, the sulfur content of the substance in the oil phase was 2.0%, and the sulfur content in the heavy oil dropped down to about 40%.

Based on the confirmed finding of this autoclave experiment further extraction revealed that more than 50% of the sulfur contained in the heavy oil can be removed by continuous counter-current treatment. In this connection reference may be made to the experience of the inventors in the counter-current superheated water extraction of phenols from phenols-containing mineral oils (see Separation, Dr. Eiji Munekata, published by Maruzen, 1951, and Researches in the Chemistry and Industrialization, Dr. Eiji Munekata, published by Nikkan Kogyo Shimbunsha, 1964).

EXAMPLE 2 Vacuum distilled gas oil (650-1000 F.) having a sulfur content of 2.5% and a specific gravity 0.92 was extracted by superheated water at about 230 C. in a counter-current contact extraction column in a laboratory. The sulfur content of the light oil after the treatment was 1.5%. According to this result it is apparent that desulfurized gas oil with sulfur content less than 0.5% could be obtained in an extraction tower operated counter-currently.

EXAMPLE 3 A heavy oil having a sulfur content of 4.4% and specific gravity 0.99 was blended with light oil in equal amounts to prepare a sulfur-containing mineral oil of total sulfur content 2.5% and specific gravity 0.93. When examined, this blended oil was found to be far more suitable than the original heavy oil for counter-current continuous extraction. This sulfur containing mineral oil was treated in the apparatus described in the drawing with salt water solution at 300 C. A heavy oil was obtained by distilling the treated blended oil which exhibited a reduction in sulfur content.

What is claimed is: 1. A method of treating a sulfur-containing mineral oil to reduce its sulfur content comprising extracting sulfur-containing substances from said mineral oil by intimately contacting said mineral oil with super-heated aqueous liquor having a temperature above C., wherein the specific gravity of at least one of said mineral oil and said super-heated aqueous liquor is adjusted prior to treating said oil, by adding Water soluble substances and/ or colloidal substances so that the ditference between their specific gravities at the temperature of the treatment is sufficient to enable a counter-current flow.

2. The method of claim 1, wherein said aqueous liquor is at a temperature between 100 C. and 350 C. and said oil is contacted with said super-heated liquor in a treatment vessel.

3. The method of claim 1, wherein said super-heated aqueous liquor is super-heated water.

4. The method of claim 1, wherein the specific gravity of the oil is adjusted by selecting suitable fractional distillates.

5. The method of claim 1, wherein the specific gravity of the mineral oil is adjusted by adding distillates to said mineral oil which is to be treated.

References Cited UNITED STATES PATENTS 2,78%59 3 1957 McDonald 23-310 415,876 11/1889 Minshall 208-208 1,838,029 12/1931 Isles 208-208 2,402,799 6/ 1946 Arnold et al 208-208 3,670,896 6/1972 Hale, Jr., et al. 210-242 DELBERT E. GANTZ, Primary Examiner J. M. NELSON, Assistant Examiner U.S. Cl. X.R. 208-289