FI67720B - AVLAEGSNANDE AV SMAO SYRAMAENGDER - Google Patents

Description

\ * jSr? \ ΓΒ1 m1, advertisement publication A779n [B] (11) UTLÄGG Nl NGSSKRIFT O / / ΔΌ C (45> - '^ ^ (51) Kv.ik.4 / lnt.ci. * C 10 G 19 / 02 FINLAND —FINLAND (21) Patenttlhakemu * - Patentansäkning 781377 (22) Application date - Ansökn Ingsdag 0 ^ .05 * 78 (H) (23) Starting date - Giltighetsdag 04.05 · 78 (41) Published public - Blivit offendig 06.1 1 .78

National Board of Patents and Registration of Finland Date of publication on the day of publication—

Patent- och registerstyrelsen '' Ansökan utlagd och utl.skrlften publicerad 31 .01 .05 (32) (33) (31) Privilege claimed - Begärd priority 05.05 · 77 USA (US) 79 ^ 153 (71) UOP Inc., Ten U0P Plaza - Algonquin & Mt. Prospect Roads, Des Plaines,

Illinois, USA (72) Thomas Ace Verachtert, Wheeling, Illinois, USA (7 ^) Berggren Oy Ab (5 ^) Removal of small amounts of acid - Avlägsnande av sma syramängder

Many hydrocarbons contain sulfur in the form of mercaptans (thiols). Mercaptans are almost invariably present in liquefied petroleum gases, cracked gasolines, straight-run gasolines, natural gasoline and heavier hydrocarbon distillates, e.g. in fire oil and fuel oil.

These mercaptan components are undesirable mainly due to their strong odor, but in some cases also due to their adverse chemical reaction with other hydrocarbons or fuel system components.

Many attempts have been made to provide processes that remove or modify mercaptans. Some of the previous processes involved treatment of the hydrocarbon fraction with base, clay, and hydrotreating. A significant improvement in the handling of hydrocarbon fractions was achieved when the UOP Merox process was announced to the industry in 1959. Oil and Gas Journal Issue 1959-10-26 includes the Merox process as well as a description of some previous processes.

F ____ 2,67720 This process used a catalyst dissolved in a base or alternatively supported on a support to oxidize mercaptans to disulfides in the presence of oxygen and a base.

U.S. Patent 3,108,081 discloses a catalyst comprising an adsorbent support and a phthalocyanine catalyst for oxidizing mercaptans. According to this patent, the most suitable phthalocyanine was a sulfonated derivative, with monosulfonate being particularly preferred.

In industrial work, several catalyst toxins or other harmful substances are present in the hydrocarbons fed to the treatment units for the removal or modification of mercaptan.

Small amounts of acidic components such as naphthenic acids and hydrogen sulfide are also common.

Hydrogen sulphide often occurs naturally, but is also present as a by-product from some of the earlier stages of the process, in which sulfur compounds decompose in the presence of hydrogen and at high temperature to form hydrogen sulphide. When the hydrocarbon feed stream to be treated is either naphtha or fuel oil, most of the hydrogen sulfide is removed during distillation, but such removal is not always complete and further treatment of the hydrocarbon stream is required.

Naphthenic acids and other carboxylic acids are commonly found in crude oil. During distillation, naphthenic acids are distilled together with hydrocarbons with a similar boiling range, condensing into different distillate streams. Naphthenic acids are characterized by solubility in both hydrocarbon and aqueous media and are often referred to as surfactants due to their activity at surfaces, such as liquid-hydrocarbon interfaces. When neutralized with alkali salts, naphthenic acids form alkaline naphthenates that are chemically similar to soaps. As such, they tend to emulsify the hydrocarbon and aqueous phases, effectively preventing the oil and aqueous phases from separating.

Because of these properties, they must be removed from finished products where the presence of aqueous emulsions cannot be allowed, or from substances fed to chemical treatment processes where they interfere with the efficient performance of the process.

3,67720

Thus, several methods have been developed in processing technology to solve these problems. One method is to simply introduce a large vessel, called a prewash device, partially filled with a dilute aqueous alkaline solution, disperse the hydrocarbon containing small amounts of acid components in the solution, and carry a stream of hydrocarbon upward through the vessel. Typically, the hydrocarbon stream is passed to the prewash vessel through a nozzle array to ensure close contact of the hydrocarbon with the dilute base solution. Sometimes the connection is made by circulating the base solution by means of a pump to mix the base solution with the incoming hydrocarbon in the piping. The strength and amount of base solution used are generally adjusted so that the base solution absorbs very little of the weakly acidic mercaptans contained in the feed material. The primary solution pretreatment only removes more acidic naphthenic acids, hydrogen sulfide and other residues of acidic compounds. When a very low acid content in the product is desired, a sand filtration separator can be connected to the rear of the pre-wash vessel to remove any corresponding salt water droplets from the hydrocarbon stream to be treated. However, a sand filter often requires maintenance to maintain its separation efficiency, and the sand is exposed to the corrosive effect of alkaline aqueous solutions.

Unfortunately, such a method does not always satisfactorily solve the deacidification problem. The use of a large prewash vessel increases the capital cost of the plant, and it may be possible that the alkaline solution will not be used effectively. When removing naphthenic acid, a very dilute alkaline solution must be used for the most efficient deacidification. The use of a batch pre-wash system also means that the naphthenic acid removal efficiency is intermittent. Efficacy is greatest when the alkaline solution is fresh and lowest when the weakly alkaline solution is discarded. Due to the periodic nature of the process and the surface activity of the naphthenate soaps, a certain amount of unneutralized base is always wasted with the base solution used.

However, even with the use of a conventional separator behind a prewash vessel, such as a sand filter or mesh mat separator, the entrainment of acid salts is sometimes too great. This is because the efficiency of the separators depends on many different factors. Acceptable efficiency can only be achieved in a relatively narrow flow rate range, and the deterioration in efficiency associated with use is 4,67720 common, with particle agglomeration, wear due to sand abrasion, channel formation, and other factors reducing the performance of the separators. The inability of conventional disconnectors to maintain high efficiencies without frequent maintenance has led to the use of electrical disconnectors. These devices are similar to known desalination devices used to remove water containing dissolved salts absorbed into crude oil. By using an electrical separator, it is possible to remove sufficient absorbed alkali solution containing naphthenic acid salts from the prewashed hydrocarbon to meet the requirements of the subsequent process units, and to use an electrical separator if applicable for special purposes such as separating water from jet fuel. Admittedly, electrical isolators are exclusively manufactured and greatly increase the cost of pretreatment equipment. They also require careful monitoring, which tends to increase their operating costs as well as the costs of supervisors.

Another problem with previous prewash processes is the placement of large amounts of reagent used. As mentioned above, the efficient operation of the intermittent type pre-wash vessel does not allow complete removal of the alkali solution. There is always a considerable amount of unneutralized base that remains in the relatively large liquid reservoir of the alkali solution in the prewash vessel. Thus, when the acidification efficiency of the alkaline solution is no longer sufficient, a large relative amount of unneutralized alkali will necessarily be discarded. This problem is due not only to the inefficient use of reagents, but also to the fact that free alkali poses a particular placement problem.

One disadvantage of intermittent prewash is that it is difficult to recover the naphthenic acids in the base phase used. If an attempt is made to recover these acids, it is first necessary to re-acidify the spent base solution and then to separate the acids from the oil mixed with them. Due to the dilution of the streams used in the pretreatment of the mercaptan conversion process, the recovery of naphthenic acids is not generally considered profitable. In this case, the source of potentially valuable raw material is left unused. Naphthenic acids can be used as paint driers, wood preservatives and, to some extent, lubricants operating under very high pressures. Naphthenic acids have also been used as solvents for vulcanized rubber, various resins and aniline dyes, mineral oil clarifiers, insecticides, and wood oil additives to effect air-free drying.

Thus, oil refineries are constantly looking for a process that provides efficient deacidification, is economical to use, and provides an almost stoichiometric utilization of the time solution. There is also a need for a process that is continuous to avoid the often necessary draining and handling of large volumes of alkali solution.

Accordingly, the present invention provides a process for removing acids from liquid hydrocarbons comprising (a) mixing an aqueous alkaline solution with a hydrocarbon, (b) feeding the mixture from step (a) to a hydrophilic separation layer, (c) separating the hydrocarbon phase and a separate aqueous phase in this layer, and (d) ) recovering from said layer the hydrocarbon phase with reduced acid content and the aqueous phase almost saturated with acids as a product of the process.

In a more limited embodiment, the invention provides a continuous process for removing naphthenic acids from a fuel oil stream, the process comprising (a) burning oil and an amount of 1-3% by weight aqueous sodium hydroxide in ) draining the mixture obtained in step (a) downwards through a stationary layer of hydrophilic separation medium with an LHSV, i.e. a flow rate between 0.5 and 20 volumes per hour, and separating the spent basic aqueous phase from the fuel oil in said layer (c) by 0.10% removing the fuel oil containing the initial naphthenic acid content from the bottom of the bed as a process product, and (d) removing the aqueous phase from the bottom of the bed.

In another embodiment, the invention provides a process for recovering naphthenic acids from liquid hydrocarbons, the process comprising (a) conveying a sufficient amount of a basic aqueous solution to neutralize the liquid hydrocarbons and naphthenic acids to a 6 67720 mixer, (b) conveying (c) absorbing at least a portion of the neutralized naphthenic acids contained in the liquid hydrocarbon in said medium; and (d) removing the aqueous phase comprising the spent base solution and the hydrocarbon phase comprising the naphthenic acid-reduced hydrocarbons from said layer.

The hydrocarbon streams that can be treated by the process of this invention are low in an acid. For example, naphthenic acids are generally detected in streams with ASTM D 86 distillation endpoints above 150 ° C. Hydrogen sulphide can be found in most refinery intermediate streams. Carboxylic acids are often present in catalytically cracked species. The method of this invention can be successfully applied to all of these species.

Many fuel oil batches that need to be treated to convert mercaptan often contain a lot of naphthenic acid. The naphthenic acid content is usually expressed as an acid number, the typical number being the milligram amount of potassium hydroxide required to neutralize one gram of sample. The requirement for most jet fuel fuels is that the acid number should not exceed 0.010 mg KOH / g. Today, batches with acid numbers greater than 0.100 mg KOH / g are found. Existing intermittent prewash units with their subsequent separators cannot effectively remove naphthenic acids in the range of approximately 0.025 mg KOH / g. The presence of such large amounts of naphthenic acid in the materials fed to the mercaptan conversion unit, if not removed, causes operational difficulties in the treatment unit as well as product loss. The acid number of a fuel oil or other hydrocarbon can be determined by a variety of test methods, such as ASTM-D-3242, ASTM-D-3339, ASTM-D-974, ASTM-D-664, and the like.

The base proposed for use may be any water (or alcohol) soluble inorganic base. Both NaOH and KOH are suitable, with sodium hydroxide being most preferred due to its easy availability and low cost. A relatively dilute aqueous alkaline solution is necessary to cause the naphthenic acid to dissolve in the aqueous phase.

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The solubility of alkali naphthenates in the aqueous phase decreases with increasing alkali content of the aqueous phase. The solubilities of other acid salts also tend to limit the base concentration in the solution, which can in fact be used at normal temperatures.

Regardless of the type or concentration of base used, the invention makes it possible to work with only a small excess of base in the event of variations in the acid content of the feed.

The feed stream and the basic aqueous phase are contacted with each other in a simple mixer before they enter the separation bed.

The material of the separating layer is selected from the group of alkali-resistant substrates, such as e.g. various activated wood and other residual coals, coal, lignite, shale, slag and calcined coke, and preferably having hydrophilic properties. Examples of suitable residual carbons are e.g. those derived from wood chips, lignite coal, anthracite coal, bituminous coal, peat, petroleum knife, and the like. Crushed and sorted anthracite coal is particularly preferred.

The contacting of the hydrocarbon with the injected alkali and the separation layer can take place in any suitable manner. The separation medium can be maintained as either a fixed or a movable layer. Periodic connection can also be used. The hydrocarbon stream may pass through the separation medium in an upward, downward or radial direction.

The amount of separation medium must be adapted to the properties of the material to be fed and the desired properties of the product. It may be desirable to install parallel separating layers so that one layer can be used to regenerate another. Serial flow coupling can also be used to achieve maximum deacidification.

It is also possible to use several layers connected in series together with a series connected in parallel.

The amount of separation medium required can be determined as a function of the liquid flow rate. In general, the separation medium must be adequately charged so that the liquid flow rate will be between 0.5 and 20,67720 bed volumes per hour. Likewise, the dimensioning of the preferred solid catalyst bed is such that the flow rate of the liquid through the bed is selected to provide the highest efficiency and lowest cost.

For best results, the particle size distribution of the media should be between 0.1-6.0 mm, with particle sizes between 0.6-2.0 mm showing excellent properties.

The temperature and pressure conditions in which the base solution comes into contact with the feedstock and in which the mixture comes into contact with the separation media are not critical. In general, ambient temperatures above the freezing point of the aqueous phase or the freezing point of the oil phase can be used. Typical evening temperatures for refinery hydrocarbon product streams are in the range of 10-60 ° C, and the present invention works well in these temperature ranges. The lower temperature limit is usually set to a value at which the viscosity of the liquid becomes so high that secure contact between the aqueous phase and the substance to be fed no longer takes place and subsequent separation of the aqueous phase from the organic phase is prevented. The upper temperature limit is usually set according to the degree of dewatering that can be tolerated in the system and the allowable water content of the treated hydrocarbon stream. Working between 25-60 ° C gives satisfactory results with several feed streams. Normal materials are highly fluid at these temperatures, and contact and separation of the aqueous and hydrocarbon phases are facilitated. Working at much higher temperatures is possible and may be desirable when handling very heavy or viscous oils. Higher temperatures tend to promote contact events and reaction rates, but, for example, adequate deacidification can generally be achieved without the cost of heating the stream to a high temperature. The pressure under which the deacidification process according to the invention operates must be sufficient to maintain the liquid phase, since both the contacting and the separation of the organic phase and the aqueous phase take place throughout the liquid state. Pressure is obviously not a significant factor. Thus, the pressure should generally only be of such a magnitude as to cause the liquids to pass through the process units.

9,67720

The function of the injected alkaline solution is twofold. The base solution not only neutralizes the acid in the feed medium, but also wets the surface of the separating medium layer. Thus, the process of the present invention works efficiently because the acids and the base react not only in the mixing equipment but also in the separation layer following them. Due to this extensive and close contact between base and acid, the present invention works effectively.

Furthermore, there is an aqueous phase dispersed in the hydrocarbon stream after completion of the reaction between the acid and the alkali, which aqueous phase must be removed. This is another function of the separation layer. The layer gradually collects the dispersed aqueous phase into small droplets, eventually forming large droplets that separate and settle to the bottom of the separation vessel for removal. Preferably, the liquid level controller automatically causes the water phase to flow out of the separation vessel as it collects. The advantage of automatic liquid level control is that it makes the process really continuous, so that very little or no employee monitoring is required.

The support for the carbon layer is preferably a flat screen which holds the carbon up but passes the spent alkaline solution through to remove it from the layer. Particularly suitable are the known Johnson screens available from the Johnson Division of UOP Inc. These screens are assembled from wedge-shaped rods welded to a support frame. They are very strong and generally unobstructed, with a relatively large open area for fluid flow. The hydrocarbon stream can be introduced into and removed from the carbon layer through round screen plates of similar structure.

The drawing shows a simplified flow diagram of an embodiment of the invention in which a dilute alkaline solution is continuously injected into an acidic feedstock and the mixture is passed through a separation bed.

In the first step of the process according to the invention, the acidic feed stream coming via line 10 is contacted with a dilute base solution sucked from storage tanks 1 (not shown in the drawing) via line 21 by pressing 10 67720 solution via line 22 to mixer 2. Hydrocarbon and alkali solution 11 along the separation vessel 3. The separation vessel 3 comprises a separation layer 4, an inlet distributor 8, a collecting pipe 5 and a drain screen 6.

The treated hydrocarbon, which is substantially acid-free, is removed from the carbon bed through a collection tube 5 and transferred along line 12 to other processing units or a storage tank (not shown in the drawing).

The aqueous phase separated by the carbon layer seeps down through the layer, exiting through the drain screen 6 to the drain tank 7. The inspection glass and the liquid level regulator ensure that the used aqueous phase is continuously discharged via the line 23.

Example I

A small test facility was used to test the invention. The fuel to be fed was a fuel oil with a very high acid number, namely 0.084 mg KOH / g. The separating layer consisted of 50 cm 2 charcoal, manufactured by Norit Co. The mesh value of charcoal was reported to be 10/30, and 90% of the particles were between 0.6 and 2.0 mm in diameter. The charcoal was placed as a solid layer in a small pressure vessel. The inner diameter of the vessel was 25 mm and the height of the layer was 100 mm. The charcoal was supported by a glass wool plug at the bottom of the vessel. The alkali solution added to neutralize the naphthenic acids was a dilute aqueous solution of sodium hydroxide. The base content was 1.5% by weight. The solution was added slowly with a syringe. Such a base solution addition method was necessary because the plant was small and because the present invention provides a very efficient use of the base. An ultrasonic stirrer was used to mix the fuel oil with sodium hydroxide solution before the separation layer.

The acid number of the feed was measured. The hydrocarbon product, after passing through an activated charcoal layer, was analyzed for both sodium content and acid number. The feed was measured after mixing with the base solution but before separation to confirm the correct addition of NaOH. Acid titration of the mixture as well as atomic absorption spectroscopy (AAS) analyzes were used to determine the alkali content.

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The experiments were performed with LHSV values of 2.0 and 4.0, i.e. at a feed rate of 3 3 of 100 cm / h and 200 cm / h, respectively.

The test results are shown in Table 1 below.

table 1

Hours IHSV Product: Moles NaOH / mole acid in feed

Acid number Na (ppn) Added Titration result AAS result 0-8 2 0.001 0.25 8-17 2 0.010 1.11 0.46 17-38 2 0.011 38-73 4 0.029 1.5 1.77 1.29 0, 27 73-80 4 0.009 0.34 1.26 0.60 0.10 80-100 4 0.004 0.45 1.28 1.29 0.10 100-124 4 0.023 2.2 1.14 0.60 0 , 34 124-152 4 0.005 3.6 1.14 0.58 0.77 152-179 4 0.018 8.1 1.14 0.40 0.74 179-197 4 0.036 19 1.14 0.48 1, 03 197-221 4 0.006 3.6 1.14 0.34 0.53 221-248 4 0.004 7.1 - - 0.80 248-273V2 4 0.003 6.1 - - 0.74

Example II

Another experiment on the invention was performed on an industrial-sized unit. Fuel oils from Louisiana and Illinois were used as feed materials. The existing refinery vessel was used as the separation layer of the unit. No attempt was made to construct the vessel in advance, rather, an attempt was made to use refinery equipment to test the invention on a somewhat larger scale.

No agitator was used to provide close contact between the fuel oil feed stream and the alkaline medium. Instead, a partially closed valve placed in front of the separator was used.

An alkaline medium available from the refinery at a concentration of 4-fP on the Baume scale was used as the alkaline medium. This concentration was higher than desired, but was the only concentration available for the experiment. Calculations showed that about 11.4 _ ____. . Γ: .. ______ 12,677,720 gallons of alkaline solution per hour were needed to neutralize the fuel oil from Louisiana crude oil, while 5/7 gallons of alkaline solution per hour was needed to neutralize the acids contained in the fuel oil from the Illinois basin. Charcoal Calgon SGL, 8 x 30 mesh, was used as the separation medium. When Louisiana oil was used, the injection of the base solution was started at a flow rate of 37.8 liters per hour, which is considerably higher than that required to neutralize acids, primarily naphthenic acids, stoichiometrically. This injection rate of the base solution reduced the initial acid number of the fuel oil from 0.10 mg KOH / g to 0.0096 mg KOH / g. The effluent showed that only about 50% of the base solution had been consumed. The base solution spray rate was then reduced to about 28.8 liters per hour, but this resulted in insufficient acid removal. According to the analysis, the fuel oil product contained an excessive amount of naphthenic acid, namely 0.032 mg KOH / 100 ml. This analytical result may be questionable due to the difficulty of obtaining a representative sample. However, 60% of the run-off base solution had been consumed. The amount of base remaining in the fuel oil product ranged from 0.042 to 0.067 ppm NaOH. This lower amount of residual base was expected because experience has shown that it is easier to separate the base from hydrocarbons in an industrial-sized unit than in a pilot plant.

Example III

The experiments were further performed in the experimental facility described in Example I. These experiments were performed using charcoal from Darco Company with a nominal mesh size of 10-30 (90% of the particles had a diameter between 0.6 and 2.0 mm). The feed was the same as in Example I. In Example III, the target amount of base solution injected was 1.2 times the amount theoretically required to neutralize naphthenic acids. The base solution used was somewhat more concentrated than that used in the first experiment, namely 5 ° Baum§ NaOH (corresponding to 3.2% by weight NaOH). The reaction temperature was 25 ° C and the pressure was 550 kPa.

The test results are shown in Table 2.

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Table 2

Hours LHSV Product: ppm NaOH added

Acid number Na (ppm) Addition Titration result 0-12 4 0,005 - 73 18 12-23 4 0,017 73 16 23-37 4 0,010 1,2 73 22 37-45 4 0,007 1,4 (temporary turbidity in the product) 45-53 4 0,005 73 32 53-64 4 0.016 (from jelly separation) 64-73 4 0.009 75 20 73-80 4 0.006 75 19 80-89 4 0.005 89-99 4 0.005 75 45 99-108 4 0.003 75 64 108-118 4 0.005 75 11 118-126 4 0.008 126-137 4 0.023 73 15 137-150 4 0.010 2.8 73 13 150-159 4 0.007 73 19 159-166 4 0.005 71 68 166-189 4 0.006 71 11 189-196 10 0.012 2 , 5 69 78 196-204 10 0.011 12.9 68 39

xStoichiometric amount 62 ppm NaOH

The gel-like substance appeared in the separator after 64 hours of operation and formed continuously until the end of the experiment. A temporary plug developed at 99 hours. Occasionally there was some turbidity in the product, but this usually disappeared after a few hours. However, at the end of the experiment, the cloudy product required up to 7 days of standstill to clear up. It is probable that the higher concentration of sodium hydroxide caused the formation of a gel-like substance, indicating that the concentration of the base must be precisely controlled.

Example IV

The same test apparatus and feed material as in Examples I and III were used. In this example, ground anthracite carbon was used as the separating material. The nominal particle size of the carbon was between 14 ----- il_______ ______ 67720 0.84-2.0 mm, with a reported mesh value of 10 x 20.

A somewhat more dilute base solution, 3 °, was used in this experiment

Baume NaOH (corresponding to 1.8% by weight of sodium hydroxide). The experiment was performed with an LHSV of 4.0 and was continued until the amount of feedstock was consumed. The results of the experiment are shown in Table 3.

Table 3

Hours LHSV Product: ppm NaOH

Acid number Na (ppm) Addition Titration result 0-11 4 0.046 - 68 11-23 4 0.014 3.9 68 12 23-35 4 0.008 - - 8 35-48 4 0.007 1.9 67 31 48-70 4 0.005 0.63 67 60 70-89 4 0.006 0.50 67 23 89-97 4 0.005 - 67 28 97-120 4 0.004 0.92 67 31 120-144 4 0.006 0.66 67 40 144-168 4 0.006 1.05 67 36 168-175 4 0.006 - 67 35 This experiment was significantly better at reducing the naphthenic acid content of the product than the previous experiments, as shown by the acid numerical values. The result of this experiment was also very satisfactory in that the sodium content of the product was significantly lower than in the previous experiments, although the sodium content of the product in Examples I and III is satisfactory.

Most of the advantage achieved in Example IV is due to the lower NaOH concentrations, but there may be a synergistic effect due to the use of anthracite as the separation medium.

The separation layer of the present invention, when used for the removal of naphthenic acids, may optionally be impregnated with naphthenic acid salts. Several different regeneration methods can be used to reactivate the bed as well as recover naphthenic acid salts for use as a valuable by-product.

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It is likely that acceptable regeneration can be accomplished simply by removing the bed from the feed stream and introducing hot water vapor into the bed. In order to achieve a more complete regeneration of the bed and to recover the naphthenic acid salts in the form of an acid rather than a salt, it is also possible to convert the salts immediately back into acids. This can be accomplished by isolating the separation layer from the hydrocarbon and base solution streams, circulating the aqueous acid solution through the layer, and desorbing the naphthenic acids from the carbon.

If a sufficient amount of acid solution is used, much of the naphthenic acid will be displaced in the acidification step. The desorption of naphthenic acids can be promoted by introducing hot steam into the reactor. Naphthenic acids evaporate with steam, and this treatment should provide almost complete regeneration of the separation layer. If the carbon layer cannot be easily regenerated by this mild method, it may be necessary to go to steam treatment at an elevated temperature or to treatment with various known hydrocarbon solvents such as benzene, acetone and methanol to enhance the removal of naphthenic acids and acid salts from the separation layer.

An interesting feature of the present invention is that while performing excellent work to remove acids from the fuel oil product or feed to the mercaptan conversion unit, the invention also provides up to a 1000-fold increase in naphthenic acids, allowing recovery of naphthenic acids without the desired by-product, any commercial use. Most of the naphthenic acids are recovered from the aqueous phase as long as a balanced amount has accumulated in the separation layer.

The present invention can also be used to remove hydrogen sulfide from carbon-hydrogen streams. A hydrocarbon stream containing, for example, 0.01% by weight of hydrogen sulfide can be contacted with a stream of aqueous solution containing 6% by weight of sodium hydroxide and passed together through a separation layer. The separating layer preferably consists of charcoal with a nominal grain size of 0.6-2.0 mm and available under the trade name Calgon. If a 30% excess of base is used, the hydrocarbon product leaving the separator would contain less than 0.0005% by weight of hydrogen sulfide.

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The efficiency of the removal of certain acids is limited by the consideration of equilibrium factors under the desired operating conditions. The removal of very weak acids, for example mercaptans and phenols, may also depend on the consideration of equilibrium factors, the adjustment of the concentration of the alkaline solution and the type of acid component to be removed.

It is recommended to use a more concentrated alkaline solution to remove hydrogen sulfide than naphthenic acids. This is because the salts of hydrogen sulfide are more soluble than the salts of naphthenic acids. NaOH concentrations of between 2 and 10% by weight give good results.

The results obtained show that the process according to the invention, applied to the removal of naphthenic acids, is very effective in reducing the acid number of a naphthenic acid-rich fuel oil. In general, it should be possible to reduce the naphthenic acid content to an acceptable level for the further processing or sale of the oil.

It can be seen that the process of the invention provides an almost stoichiometric base utilization. Acid neutralization is also more efficient due to the larger effective surface area of the basic medium, not only in the mixer and piping but also in the separation layer. The greater flexibility and efficiency of the method make it possible to work at hydrocarbon flow rates that are much lower than normal. There is very little aqueous solution due to the hydrocarbon due to the ability of the separation layer to collect water droplets into a separate phase that separates from the hydrocarbon by gravity. The method is also capable of reducing pretreatment device costs.

Il

Claims (13)

67720 17 A process for pretreating a crude petroleum distillate, wherein H 2 S and other acidic components are removed by mixing an aqueous base solution with a distillate before oxidizing the mercaptan compounds contained in the distillate, characterized by (a) passing the mixture to bring the aqueous phase of the mixture to fuse together, (b) recovering the crude distillate from the bottom of the solid fusion layer without the oxidation products from step (a) present and the distillate being substantially free of acidic impurities, and (c) removing the fused aqueous phase from the bottom of the fusion layer. Process according to Claim 1, characterized in that the distillate to be treated is petroleum containing naphthenic acids. Process according to Claim 1, characterized in that the distillate to be treated is naphtha or fuel oil and the acid is hydrogen sulphide. Process according to Claim 1, characterized in that the aqueous alkaline solution is continuously added in an amount sufficient to neutralize 100 to 200% of the acids contained in the system. Process according to Claim 1, characterized in that the fusion medium used is activated carbon derived from anthracite coal, wood chips, lignite coal, anthracite coal, bituminous coal, peat or petroleum. Process according to Claim 1, characterized in that the fusion medium is anthracite carbon. Method according to Claim 1, characterized in that the particle size of the fusion medium is between 0.1 and 6.0 mm. __ ______ ___________ i ... _____ 18 67720 Method according to Claim 7, characterized in that the particle size is between 0.6 and 2.0 mm. Process according to Claim 1, characterized in that in step (a) the mixture is passed through the fusion layer at a liquid volume rate per hour which is 0.5 to 20 volumes per volume of fusion medium relative to the distillate. Process according to Claim 1, characterized in that the basic solution is an aqueous solution of sodium hydroxide or potassium hydroxide. Process according to Claim 10, characterized in that the base solution contains 0.01 to 50% by weight of alkali. Process according to Claim 1, characterized in that the acid is naphthenic acid and the base solution is a NaOH solution with a concentration of 1 to 3% by weight. Process according to Claim 1, characterized in that the acid is hydrogen sulphide and the base solution is a NaOH solution with a concentration of 2 to 10% by weight.