Removal of hydrogen sulfide and / or mercaptans from petroleum or petroleum derivatives and treatment compositions for achieving the removal

Abstract

An aqueous treatment composition of crude oil and / or petroleum distillate for removing sulfur compounds from crude oil and / or petroleum distillate, and a treatment method using such a composition are disclosed. The composition has less than 0.5% by mass of a di- or tri-benzhydroxy compound, a strong base, less than 1% by mass of a divalent metal gluconate, the balance being water, and a pH of 9 or more. The treatment method includes the steps of adding the treatment composition to crude oil or petroleum distillate to form a mixture having 0.001% to 0.02% by mass of a di- or tri-benzhydroxy compound in the oil and 0.001% to 0.03% by mass of a divalent metal gluconate in the oil, and mixing them together.

Description

Technical Field

[0001] Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 369,088, filed Jul. 22, 2022, which is hereby incorporated by reference in its entirety.

[0002] This application relates to the removal of hydrogen sulfide and / or mercaptans from petroleum, and more particularly to the removal from crude oil and / or petroleum distillates by an oxidation reaction caused by treatment with a caustic solution of a divalent metal gluconate and a di- or tri-benzhydroxy compound.

Background Art

[0003] The removal of hydrogen sulfide from petroleum has been a long-standing problem as revealed by U.S. Patent No. 2,468,701, filed Jan. 25, 1945, and remains an unsolved need as revealed by U.S. Patents Nos. 4,206,194; 5,180,572; and 6,746,611. Along with hydrogen sulfide, it is also desirable to remove mercaptans. These are both often volatile toxic gases present in crude oil. Crude oil with a high sulfur content can cause corrosion, catalyst poisoning, and environmental pollution. If sulfur-containing substances remain, this can be present in gasoline, diesel fuel, and jet fuel, which is undesirable.

[0004] Many sulfur compounds can be present in crude oil. The following table lists sulfur compounds in order of increasing difficulty of removal from crude oil (the top is easier than the bottom).

[0005]

Table 1

[0006] A common method for treating crude oil is caustic washing. Caustic washing removes sulfides from crude oil and petroleum distillates. This method is relatively simple and cost-effective, but it does not remove all sulfur forms, especially organic sulfides, and generates a large amount of caustic soda (NaOH / KOH) wastewater that is harmful to the environment. The wastewater is typically collected in large ponds for post-treatment. Such post-treatment is costly and time-consuming.

[0007] Furthermore, sodium and residual alkalinity are added to the oil, which can make the oil corrosive and cause scaling problems in pipelines and other infrastructure. Additionally, at high pH, the presence of sulfide ions can cause reactions with metals. Caustic washing can also cause water-in-oil emulsions and foam due to the saponification of fatty acids in the oil.

[0008] Other engineers have tried dry gas desulfurization, hydrodesulfurization, and biodesulfurization, but these are much more costly methods. Triazine and other amines are commonly used liquid scavengers for removing hydrogen sulfide from oil, but residual triazine in the oil can cause fouling and corrosion of pipes, towers, and other equipment.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0010] These methods have been shown to reduce hydrogen sulfide in petroleum, but there is always a need to find more rapid, effective, cost - efficient and environmentally friendly methods for removing sulfur compounds including not only hydrogen sulfide but also mercaptans from crude oil and petroleum distillates.

Means for Solving the Problems

[0011] In a first aspect, a method for treating crude oil or petroleum distillate is disclosed. This method includes a step of preparing a crude oil or petroleum distillate that requires reduction in the content of sulfur - containing compounds, and a step of adding a treatment composition thereto. The treatment composition has a pH of 9 or higher and (a) less than 1 mass% (% wt / wt) of di - or tri - benzhydroxy compounds; (b) a strong base; (c) less than 0.5 mass% of divalent metal gluconate; and (d) the balance water and contains. 1. This method also includes a step of mixing the treatment composition and the crude oil or petroleum distillate to form a mixture containing (a) from 0.001% to 0.02 mass% in the petroleum and (c) from 0.001% to 0.03 mass% in the petroleum. Upon mixing, (a) oxidizes the sulfur compounds in the crude oil or petroleum distillate in the presence of (c), thereby reducing the amount of sulfur compounds in the crude oil or petroleum distillate. During addition and mixing, oxygen gas may be introduced. The oxygen gas source may be the outside air. This method may optionally include a step of adding an aqueous hydrogen peroxide solution of 30 mass% or less at 1000 ppm or less after mixing the treatment composition with the crude oil or petroleum distillate, and a step of washing the mixture with toluene, ozone - treated water, or a hydrogen peroxide solution after the amount of sulfur compounds present has been reduced. Alternatively, this method may include a step of adding polyethylene glycol at 1000 ppm or less after mixing the treatment composition with the crude oil or petroleum distillate.

[0012] Typically, the sulfur compound is hydrogen sulfide and / or mercaptan. In one embodiment, (a) is present in less than 0.2% by mass of the treatment composition, and (a) is hydroquinone and / or pyrogallol, more preferably hydroquinone and pyrogallol. The mass concentration of pyrogallol is higher than that of hydroquinone.

[0013] In one embodiment, the pH is at least 13. In one embodiment, (c) comprises zinc gluconate and / or magnesium gluconate, more preferably a mixture of zinc gluconate and magnesium gluconate. The mixing may be carried out for at least 1 hour, more preferably at least 2 hours.

[0014] In another aspect, a treatment composition for crude oil and / or petroleum distillates is disclosed. The treatment composition comprises (a) less than 0.5% by mass, more preferably less than 0.2% by mass of a di- or tri-benzhydroxy compound; (b) a strong base; (c) less than 1% by mass of a divalent metal gluconate; and (d) the balance water and the treatment composition has a pH of 9 or more, more preferably 13 or more. In one embodiment, (a) is hydroquinone and / or pyrogallol, more preferably a mixture of hydroquinone and pyrogallol. With respect to the mixture of hydroquinone and pyrogallol, the mass concentration of hydroquinone may be higher than that of pyrogallol. (c) is zinc gluconate and / or magnesium gluconate, more preferably a mixture of zinc gluconate and magnesium gluconate.

[0015] In another aspect, (a) less than 1% by mass of a di- or tri-benzhydroxy compound; (b) a strong base; (c) less than 1% by mass of metallic zinc powder; and (d) the balance water and having a pH of 9 or more, a treatment composition for crude oil and / or petroleum distillates is disclosed.

Brief Description of the Drawings

[0016]

Figure 1

Modes for Carrying Out the Invention

[0017] The following detailed description will illustrate the general principles of the present invention, and its examples will be further shown in the accompanying drawings.

[0018] As used herein, percent or the percent symbol is understood to mean mass percent of the entire composition unless explicitly stated otherwise. It should also be noted that in any designation of a range of concentration or amount, any particular upper concentration or amount may be accompanied by any particular lower concentration or amount.

[0019] Unless otherwise indicated by way of example or explicitly stated otherwise, all numbers in this description indicating amounts of materials, parts, percentages, ratios, and proportions, physical properties of materials, and conditions of reactions are to be understood as modified by the term "about". As used herein, "about" means that a value is preferably within + / - 5% or more preferably within + / - 2% of that value.

[0020] As used herein, "room temperature" means 25°C + / - 5°C, more preferably + / - 2°C.

[0021] In a first aspect, there is described a treatment composition for crude oil or petroleum distillates that oxidizes certain sulfur compounds. After oxidation, the oxidized sulfur compounds can be removed, if desired, by extraction or washing. Petroleum distillates, also known as horticulture oil, are separated from crude oil for many industrial uses. Mineral oil, naphtha, heavy fuel oil, wax, and benzene are examples of distillates. The treatment composition reduces the abundance of sulfur compounds by an oxidation mechanism with the treatment composition. More specifically, sulfur compounds such as hydrogen sulfide and mercaptans are converted by the oxidation mechanism to thiosulfate and disulfide, and optionally polysulfide. The treatment composition has a pH of 9 or more, and as a mass percentage of the composition, (a) less than 0.5% by mass of a di- or tri-benzhydroxy compound; (b) a strong base in an amount that gives a pH of 9 or more; (c) less than 1% by mass of a divalent metal gluconate; (d) the balance water; and comprises. The pH is more preferably 11 or more, 12 or more, 13 or more. By having a pH of 11.5 or more, the pH is above the second pKa of hydrogen sulfide. The pH is controlled by a strong base. The strong base may be NaOH and / or KOH. In one embodiment, the strong base is a mixture of NaOH (50% solution) and KOH (40% solution) in an approximately 1:1 ratio by mass%. For example, NaOH is commercially available in a high-concentration form as 50% by mass in water, KOH is commercially available in a high-concentration form as either 40% or 45% by mass in water, and their blend in a 1:1 ratio results in a mixture such as 100 ml of concentrated NaOH to 100 ml of concentrated KOH, or 1 L to 1 L. In another embodiment, the ratio is 1.1:1, or more preferably 1.09:1. In yet another embodiment, the ratio is 1.5:1, 2:1, or 3:1. The ratio is typically selected to balance the overall properties of the treatment solution, including, but not limited to, viscosity, density, and cation concentration for improving the solubility of the final product.

[0022] The di- or tri-benzhydroxy compound is more preferably present in less than 0.4% by mass, or less than 0.3% by mass, even more preferably less than 0.2% by mass of the treatment composition. The di- or tri-benzhydroxy compound is selected from the group consisting of hydroquinone (1,4-dihydroxybenzene), pyrogallol (1,2,3-trihydroxybenzene), gallic acid (3,4,5-trihydroxybenzoic acid), and 1,2,4-benzenetriol, and combinations thereof. In one embodiment, the di- or tri-benzhydroxy compound is a mixture of hydroquinone and pyrogallol, and the mass concentration of pyrogallol is higher than the mass concentration of hydroquinone. The mass percentage of pyrogallol may be 500 times that of hydroquinone, for example, 0.1% by mass of pyrogallol versus 0.0002% by mass of hydroquinone. Pyrogallol is an oxygen scavenger. Therefore, pyrogallol can send oxygen gas from the headspace in the reaction vessel to the crude oil or petroleum distillate and participate in the oxidation mechanism of the reaction. The profiles of petroleum by gas chromatography and mass spectrometry do not show changes in the composition of hydrocarbons in the petroleum. Introducing a small amount of oxygen from the air into the petroleum can be effective in the "sweetening" of petroleum (i.e., by the oxidation of mercaptans and hydrogen sulfide), but it is not as strong as oxidizing the petroleum. However, in some cases, there was a decrease in the asphaltene content.

[0023] The divalent metal gluconate is more preferably present in less than 0.8% by mass, or less than 7% by mass, even more preferably less than 6% by mass of the treatment composition. The divalent metal gluconate is selected from the group consisting of zinc gluconate, magnesium gluconate, calcium gluconate, iron(II) gluconate, copper(II) gluconate, and combinations thereof. In one embodiment, the divalent metal gluconate is a mixture of zinc gluconate and magnesium gluconate. In one embodiment, the mass concentration of zinc gluconate is higher than the mass concentration of magnesium gluconate. The mass percentage of zinc gluconate may be 10 times that of magnesium gluconate, for example, 0.5% by mass of zinc gluconate versus 0.05% by mass of magnesium gluconate.

[0024] In one embodiment, the treatment composition has a pH greater than 11 and, as a mass percent of the composition, (a) about 0.1 mass % of a di- or tri-benzhydroxy compound; (b) an amount of strong base that gives a pH greater than 11; (c) about 0.55 mass % of a divalent metal gluconate; and (d) the balance water is included.

[0025] The pH is more preferably about 13. In any embodiment, the strong base may be a mixture of NaOH and KOH. In one embodiment, NaOH is about 22 mass % of the aqueous treatment composition and KOH is about 20 mass %.

[0026] In any embodiment, the di- or tri-benzhydroxy compound may be a mixture of pyrogallol and hydroquinone. In one embodiment, pyrogallol is 0.1 mass % of the aqueous treatment composition and hydroquinone is 0.0002 mass %. In any embodiment, the divalent metal gluconate may be a mixture of zinc gluconate and magnesium gluconate. In one embodiment, zinc gluconate is 0.5 mass % of the aqueous treatment composition and magnesium gluconate is 0.05 mass % of the aqueous treatment composition.

[0027] Interestingly, the combination of the di- or tri-benzhydroxy compound and the divalent metal gluconate is very effective in the oxidation of sulfides and mercaptans in crude oil or petroleum distillates. The inventors conducted trials in which the level of mercaptans decreased by at least 50% in 3 hours to a maximum of 99.9% in 1 hour depending on the dosage of the aqueous treatment composition introduced into the crude oil or petroleum distillate. Hydrogen sulfide decreased by 88% in the first half hour. Zinc is known to reduce quinone to hydroquinone. Zinc can also catalyze the oxidation of sulfides by semiquinone radicals. The oxidation of sulfides by hydroquinone is not thermodynamically favorable without a catalyst.

[0028] The inventors' experiments began with a caustic solution combined with hydroquinone and zinc powder, and then with a caustic solution combined with flavin and zinc powder in a model solution to which pentanethiol of a known concentration was added, to detect whether the mercaptan concentration decreased. This was not effective in oxidizing a sufficient amount of sulfur compounds. Furthermore, it was difficult to store zinc powder in the solution. Zinc gluconate was tested as an alternative because it is said to generate peroxyl radicals and hydroxyl radicals in the presence of sulfide. As shown in Table 1 (Table 2) below, zinc gluconate functioned better than zinc powder.

[0029] Some examples of chelation were attempted alone and in combination with hydroquinone and zinc powder, and their variants. The model chelating agent EDTA is known to stabilize hydrogen sulfide in solution, which inhibits the oxidation process. However, the hydroxy form of ferric chelate (e.g., Fe-EDTA) is used to remove hydrogen sulfide from natural gas by oxidative absorption in which hydrogen sulfide is oxidized to elemental sulfur. The inventors found that the chelating agent binds to zinc powder and reduces performance.

[0030] In another aspect, a method for treating crude oil or petroleum distillate with the above aqueous treatment composition is described below. Prepare crude oil or petroleum distillate that requires reduction in the content of sulfur-containing compounds. An aqueous treatment composition. Add the aqueous treatment composition at a preset concentration to the crude oil or petroleum distillate. The dosage may be 1% by mass or less than 1% by mass based on the petroleum. This dosage range resulted in a reduction in the mercaptan concentration of at least 50% in as short a time as 1 to 3 hours. An aqueous treatment composition at a dosage of 1% by mass resulted in a 64% reduction in total mercaptan in as short a time as 1 to 3 hours. Smaller amounts of the aqueous treatment composition, such as 0.1% by volume, were tested against various types of petroleum, and typically a 50% reduction in total mercaptan occurred over 12 hours. Therefore, a higher dosage of the aqueous treatment composition reacts more quickly and the conversion rate from mercaptan to disulfide is higher.

[0031] Since the aqueous treatment composition is aqueous, the treatment method would be to add water to the oil. The solubility of water in the oil depends on the viscosity and other characteristics of the oil. If the water solubility of the oil is exceeded, the water will separate. Typically, the addition of 0.1% of the aqueous treatment composition does not cause separation of the aqueous phase, but the addition of 1% will result in a thin film of the aqueous phase at the bottom of the oil.

[0032] The addition may be carried out with or without stirring, but better results were obtained with stirring. For example, when a 1 mass% dosage of the aqueous treatment composition was allowed to stand for several hours without stirring, it formed a layer in the oil, and it was found that the sample taken from the top had a much lower concentration of total mercaptan than the sample taken from the bottom of the oil sample. Furthermore, when this "layered" sample was stirred again and then measured, the mercaptan concentration was lower than that of the control crude oil sample. Therefore, both oxidation and precipitation were occurring in the sample.

[0033] In one embodiment, the treated petroleum mixture contains 0.001% to 0.02% by mass of di- or tri-benzhydroxy compounds in the petroleum and 0.001% to 0.03% by mass of divalent metal gluconates in the petroleum. The presence of di- or tri-benzhydroxy compounds and divalent metal gluconate compounds in crude oil or petroleum distillates reduces the amount of sulfur compounds present therein. The sulfur compounds can be hydrogen sulfide and / or one or more mercaptans. The crude oil or petroleum distillate is stirred for a preset time such as at least 1 hour. In one embodiment, the use of oxygen gas such as outside air is controlled by placing the crude oil or petroleum distillate in a sealed container having a selected amount of headspace including the outside air. Oxygen in the headspace derived from air (autoxidation) and / or oxygen in water can be utilized to react with sulfide to produce sulfate. Transition metal ions catalyze the oxidation of H2S and mercaptans. Sulfide was obtained from the water passed through the petroleum containing sulfide, but according to the infrared (IR) results and colorimetry (spectrophotometry) for the identification of sulfide, sulfite, and sulfate after treatment with the above aqueous treatment composition, the sulfide not only became sulfate and / or thiosulfate but also sulfite ions.

[0034] In all embodiments, the di- or tri-benzhydroxy compound is hydroquinone and / or pyrogallol, more preferably a mixture of hydroquinone and pyrogallol. The mass concentration of pyrogallol is higher than the mass concentration of hydroquinone. In all embodiments, the divalent metal gluconate is zinc gluconate and / or magnesium gluconate, more preferably a mixture of zinc gluconate and magnesium gluconate. The mass concentration of zinc gluconate is higher than the mass concentration of magnesium gluconate.

[0035] This treatment method may also include the addition of an aqueous hydrogen peroxide solution at a predetermined concentration in parts per million (ppm). The hydrogen peroxide solution may be a solution of 30% by mass or less, for example, a 10% by mass solution, a 2% by mass solution, or a 1% by mass solution. Hydrogen peroxide is generally added at least 10 minutes after mixing the aqueous treatment composition with crude oil or petroleum distillate. In one embodiment, hydrogen peroxide was added after half an hour of the treatment composition. In another embodiment, hydrogen peroxide was added after one hour of the treatment composition.

[0036] This method may include washing after treatment of the petroleum mixture. The washing medium may be toluene, ozonated water, or a hydrogen peroxide solution (2% - 30% solution). Toluene reacts with the hydroxide in the aqueous treatment composition to form benzyl alcohol / aldehyde, so that the excess caustic substances due to overfeeding the product into the petroleum can be consumed by the addition of toluene to the petroleum. When the liquid-liquid extraction method is required, the ozonated water or the hydrogen peroxide solution may be introduced after the initial chemical reaction has slowed down (typically after 3 hours). Both reduce the total sulfur content in the petroleum. The inventors conducted trials in which hydrogen peroxide assisted the oxidation mechanism of mercaptans. However, the inventors also conducted trials in which the peroxide reacted with divalent metal gluconate(s) to form dimers that precipitate from the petroleum mixture. This may be beneficial in that the petroleum can be more easily removed and decanted from the precipitate. The inventors found that after stopping the stirring, the gluconate (sugar) settled as a thin film at the bottom of the petroleum. When hydrogen peroxide was added without stirring, this settled to the bottom and reacted with the gluconate to form a precipitate. Gluconate is stable at high pH but decomposes when reacting with hydrogen sulfide (i.e., when hydrogen sulfide is oxidized). The inventors previously identified the free radical mechanism by electron spin resonance spectroscopy.

[0037] This method may include removal of water from the treated oil, and the water is derived from the aqueous treatment composition. This can be achieved by the addition of an emulsifier. An example is polyethylene glycol (PEG). PEG may be added at about 1000 ppm or less. In one embodiment, PEG is added at 100 ppm. In another embodiment, PEG is added at 50 ppm.

[0038] To test for residual alkalinity, a jar test of a small test sample is performed by passing about 10% by volume of water through the oil and measuring the pH. If the pH exceeds 10, a small amount of toluene is added and left for several hours or overnight, and the jar test of the oil is performed again. The resulting pH should be in the range of 9 - 10. If the wash water of the jar test has a pH exceeding 10, this indicates unused hydroxyl ions that can be corrosive, e.g., in pipelines. When H2S and mercaptans are present in the oil, it has been found that the water for water washing of the oil has a negative redox potential (e.g., -250 mV). The water passed through the treated oil should optimally have a pH of about 9 and a redox potential in the range of about -100 mV to +25 mV.

Examples

[0039] The basic procedure used to form the aqueous treatment compositions used in the following examples is as follows: The water was adjusted to a preset pH by adding concentrated potassium hydroxide and concentrated sodium hydroxide. The NaOH / KOH mixture may be a 1:1 mixture or about a 1.1:1 mixture. Then substances tested as treatment agents, such as hydroquinone, pyrogallol, zinc gluconate, magnesium gluconate, etc., were added in an amount sufficient to give the concentrations shown in the tables of the following examples. Each solution was stirred for 1 hour with a controlled amount of headspace in a covered container.

[0040] After preparing the test solution by the above procedure, a petroleum sample was typically prepared as a 100 mL sample. The petroleum samples used in the examples herein contained mercaptans such as ethanethiol, butanethiol, and pentanethiol. The tests showed that pentanethiol was the most easily detected and measured. Mass spectrometry showed evidence of disulfide products of pentanethiol and other potential products after treatment with the aqueous treatment composition (various peaks appeared on the chromatogram as the peak of pentanethiol decreased).

[0041] Each aqueous treatment composition was added to its respective petroleum sample at a predetermined dosage. In most examples, the aqueous treatment composition was introduced in an amount of 1 volume % (1 mL was pipetted into 100 mL of petroleum). The petroleum containing the aqueous treatment composition was stirred for at least 1 hour and then tested for mercaptans using the potentiometric titration method of Standard ASTM UOP 163. The lower limit of quantification in UOP 163 is 0.2 mass ppm of mercaptan (as sulfur) and 1.0 mass ppm of hydrogen sulfide (as sulfur). The dosage may vary, and if the dosage is other than 1%, it is specified in the examples below. The stirring time can also be lengthened, and if it exceeds 1 hour, it is also shown in the examples below.

[0042] (Example 1) Samples of crude oil were obtained and tested with 100 ml samples according to various treatment possibilities. 100 ppm of pentanethiol was added to each sample of crude oil to establish a known baseline for measuring the reduction in the amount of mercaptan. The ppm of pentanethiol in this example was measured using the titration method described above. After a 1-hour incubation time, the pentanethiol in the unadded control sample was 48 ppm (time was allotted for the chemical reactions that proceed before analysis of the sample). After 1 hour at room temperature and room pressure, the pentanethiol in the added control sample was 233 ppm. The samples were reacted at room temperature and room pressure in a sealed container (such as with a screw-on cap tightened on the reaction vessel) using a magnetic stir plate at a pre-set time at a moderate speed (e.g., 500 - 1000 rpm). The container had a limited headspace and in some examples had approximately 20 percent headspace. Thus, although outside air can initially contact the oil when pouring the oil or during the addition of the aqueous treatment composition, since the container is sealed, the introduction of air (source of oxygen gas) into the oil is limited and the evaporation (volatilization) of mercaptan from the sample is minimized.

[0043] In all examples, the pH listed in the table is the pH of the aqueous treatment composition itself, not the pH of the mixture of the petroleum aqueous treatment composition.

[0044]

Table 2

[0045] Trial 5 was repeated two more times for a detection time of 12 hours. In one of the trials, the ppm of pentanethiol was again below the detection limit and in the other it was 9 ppm. Each pH level reduced the ppm of pentanethiol well, and the amount of reduction increased as the pH increased. As seen in Trial 4, pyrogallol (trihydroxybenzene) alone did not oxidize the mercaptan.

[0046] Referring to FIG. 1, the aqueous treatment composition had a concentration of NaOH / KOH sufficient to define the pH of the solution (11, 12, 13, and 14 respectively), a zinc gluconate concentration of 0.1% by mass in the solution, and a 1,4-benzenediol concentration of 0.05% by mass. The percentage of mercaptan removal at each pH is shown in FIG. 1. As the pH increased, the percentage of mercaptan removed also increased.

[0047] (Example 2) Pyrogallol was further investigated. 100 ppm of pentanethiol was added to the control petroleum and then tested using standard titration methods.

[0048]

Table 3

[0049] As can be seen in Trial 4 of Table 1 (Table 2) above, pyrogallol itself is not effective in high pH aqueous solutions. As can be seen in Trial 12, pyrogallol combined with zinc gluconate reduced the concentration of pentanethiol present in the petroleum sample. A 25% reduction in pentanethiol was seen. This is much less effective compared to the trials of hydroquinone in Table 1 (Table 2). However, pyrogallol remains in solution better than hydroquinone at the concentrations tested above. The inventors have found that it is necessary to filter the solution containing hydroquinone to prevent precipitation.

[0050] In the test of adding hydrogen peroxide after treatment, the 2% solution was not strong enough. The inventors used a 30% solution of hydrogen peroxide in Trial 11 above. Since hydrogen peroxide can potentially undergo an undesirable exothermic reaction, it is not mixed into the treatment composition. Instead, as explained above, hydrogen peroxide is added after the aqueous treatment composition has been mixed with the petroleum for the incubation time.

[0051] (Example 3) The next trial was conducted to test zinc gluconate. To a sample of crude oil as tested in Example 1 having a background amount of 48 ppm of pentanethiol, 100 ppm of pentanethiol was added. This is the control shown in Table 2 (Table 3) below.

[0052]

Table 4

[0053] Each of Trials 14 - 16 reduced the pentanethiol present well. Zinc gluconate alone reduced the ppm concentration of mercaptan by 68% in 1 hour and 74% in 2 hours. By adding hydroquinone to zinc gluconate, the mercaptan was further oxidized, being oxidized by 86% in 2 hours and 89% in 12 hours.

[0054] (Example 4) Magnesium gluconate is tested. Magnesium gluconate was considered as an alternative to zinc gluconate. However, the solubility of magnesium gluconate is low. The control in the table below was the crude oil sample without addition.

[0055]

Table 5

[0056] The trace amount of hydroquinone in the above trial was 2 ppm. It was effective in reducing the mercaptan concentration by 33% with the aqueous treatment composition alone. When 150 ppm of 30% hydrogen peroxide solution was added following this same treatment composition, no detectable mercaptan was present.

[0057] Trial 17 was repeated with a sample to which 10 ppm of pentanethiol was added followed by 150 ppm of hydrogen peroxide. There was no significant improvement in the reduction of the mercaptan concentration. Magnesium gluconate was added to the treatment composition.

[0058]

Table 6

[0059] Even when hydrogen peroxide was not added, the aqueous treatment composition having both zinc gluconate and magnesium gluconate functioned better in reducing the mercaptans present in the crude oil sample. A variety of trials conducted have revealed that magnesium gluconate is suitable in the aqueous treatment composition. Also surprisingly, adding magnesium gluconate together with zinc gluconate improved the effectiveness of the reduction of mercaptans in the sample.

[0060] Calcium lactate, zinc-2-deoxyglucose, zinc acetate, and an organic copper compound (copper citrate) were each tested as possible alternatives to zinc gluconate and magnesium gluconate, but none were successful. The dosage in the oil for each alternative to zinc gluconate was 0.0015%, pyrogallol was 0.0007%, hydroquinone was 0.00001%, the pH of each solution was adjusted to 13, and the reaction time was 1 hour.

[0061] (Example 5) Next, the inventors increased the amount of pentanethiol added and retested the formulation of Trial 20.

[0062] [Table 7]

[0063] The aqueous treatment composition was effective. This reduced the added pentanethiol concentration by about 86%.

[0064] (Example 6) An aqueous treatment composition is prepared. Pyrogallol is added to a blend of 22% by mass of sodium hydroxide and 20% by mass of potassium hydroxide to a final concentration of 0.1% by mass. The blend is stirred until homogeneous. Then zinc gluconate is added to a concentration of 0.5% by mass, followed by magnesium gluconate to 0.05% (magnesium gluconate is less water-soluble than zinc gluconate and is thus added in a smaller amount), and then a trace amount of hydroquinone (2 ppm) is added.

[0065] Crude oil is treated. Petroleum containing 32.6 ppm of total mercaptans is obtained. The petroleum is analyzed by titration, according to UOP 163. One liter aliquots (Sample 1) of the petroleum are treated with 1000 ppm of the aqueous treatment composition while stirring. A second one liter aliquot (Sample 2) of the petroleum is treated with a dose of 500 ppm of the aqueous treatment composition while stirring. Both samples of the petroleum are sealed with screw caps before and after the addition of the aqueous treatment composition. The samples are stirred on a stirring plate at 500 rpm for 2 hours. Then the samples are removed from the stirring plate and allowed to stand overnight (12 hours). The containers had approximately 20 percent headspace. This implies that while air can initially contact the petroleum when it is poured in or during the addition of the aqueous treatment composition, since the containers are sealed, there is no continuous introduction of air into the petroleum and the evaporation (volatilization) of mercaptans from the samples is minimal.

[0066] After 12 hours, both samples are tested by titration according to the UOP 163 method. The control sample of the crude oil has 32.6 ppm of mercaptans (natural, i.e., no additional mercaptans have been added).

[0067]

Table 8

[0068] Both samples significantly reduced the amount of natural mercaptans present in the crude oil.

[0069] (Example 7: Gas Chromatography and Mass Spectrometry) The inventors monitored mercaptans in petroleum using headspace gas chromatography / mass spectrometry (GC / MS) selected ion monitoring (SIM). Extraction was performed using a solid-phase microextraction fiber (DVB / CAR / PDMS (divinylbenzene / carboxen / polydimethylsiloxane) of the SUPELCO® brand). For quantification, a standard curve was generated using a pentanethiol standard substance over a range of concentrations using the SPME method, and each standard substance or sample contained a constant concentration of an internal standard. The response of pentanethiol is normalized to the response of the internal standard, which is a quality assurance means.

[0070] In this trial, pentanethiol was added to petroleum having <5 ppm of natural pentanethiol. The total pentanethiol measured was quantified as 50 ppm. The inventors found that petroleum to which mercaptan was added was more prone to oxidation than natural mercaptan in petroleum, probably because the mercaptan is bound to or strongly associated with hydrocarbons in petroleum by hydrophobic interactions, van der Waals forces, etc.

[0071] [Table 9]

[0072] LOQ represents the "limit of quantification". In the test method used, the LOQ was 1 ppm.

[0073] (Example 8) Test the addition of PEG after treatment. A petroleum sample containing mercaptan was treated as above with 1 volume % (1 mL per 100 mL of petroleum) of the aqueous treatment composition according to Trial 18. Then, 0.1 volume % of 50 ppm polyethylene glycol was added half an hour after adding the above chemical blend. Titration using the UOP 163 titration method revealed a 71% reduction in mercaptan in the petroleum obtained from this treatment method. A thin layer of the aqueous phase was seen at the bottom of the separated petroleum. 50 ppm of polyethylene glycol acts as a demulsifier that helps separate the aqueous phase from the petroleum. The petroleum was then washed with water (water:petroleum is approximately 50 mass %). The oil phase and the water phase were then each tested for total sulfur by X-ray diffraction. There was a further loss of 20% of the sulfur from the petroleum into the water wash.

[0074] ​

Claims

1. A method for treating crude oil or petroleum distillates, comprising: preparing a crude oil or petroleum distillate that requires reduction in the content of sulfur-containing compounds; adding a treatment composition to the crude oil or petroleum distillate, the treatment composition having a pH of 9 or higher, (a) less than 1% by mass of a di- or tri-benzhydroxy compound; (b) a strong base; (c) less than 0.5% by mass of a divalent metal gluconate; and (d) the balance being water ; mixing the treatment composition and the crude oil or petroleum distillate to form a mixture containing (a) from 0.001% to 0.02% by mass in the petroleum and (c) from 0.001% to 0.03% by mass in the petroleum; and wherein (a) oxidizes sulfur compounds in the crude oil or petroleum distillate in the presence of (c), thereby reducing the amount of sulfur compounds in the crude oil or petroleum distillate.

2. The method according to claim 1, wherein (a) is present in less than 0.2% by mass of the treatment composition.

3. The method according to claim 2, wherein (a) contains hydroquinone and / or pyrogallol.

4. The method according to claim 3, wherein (a) contains a mixture of hydroquinone and pyrogallol.

5. The method according to claim 4, wherein the mass concentration of pyrogallol is higher than the mass concentration of hydroquinone.

6. The method according to claim 1, wherein the pH is at least 13.

7. The method according to claim 1, wherein (c) contains zinc gluconate and / or magnesium gluconate.

8. The method according to claim 1, wherein the addition and mixing are carried out in the presence of oxygen gas.

9. The method according to claim 8, wherein the oxygen gas source is outside air.

10. The method according to claim 1, further comprising adding an aqueous hydrogen peroxide solution of 30% by mass or less at 10,000 ppm or less after mixing the treatment composition with the crude oil or petroleum distillate.

11. The method according to claim 10, further comprising washing the mixture with toluene, ozone-treated water, or a hydrogen peroxide solution after the amount of sulfur compounds present has been reduced.

12. The method according to claim 1, further comprising adding polyethylene glycol at 10,000 ppm or less after mixing the treatment composition with the crude oil or petroleum distillate.

13. The method according to claim 1, wherein the mixing step is at least 1 hour.

14. (a) less than 1% by mass of a di- or tri-benzhydroxy compound; (b) a strong base; (c) less than 1% by mass of a divalent metal gluconate or zinc metal powder; and (d) the balance being water; A treatment composition for crude oil and / or petroleum distillates, containing and having a pH of 9 or higher.

15. The treatment composition according to claim 14, wherein (a) is a di- or tri-benzhydroxy compound with a content of less than 0.5% by mass and (c) is a divalent metal gluconate.

16. The treatment composition according to claim 15, wherein (a) is present in an amount of less than 0.2% by mass.

17. The treatment composition according to claim 16, wherein (a) contains hydroquinone and / or pyrogallol.

18. The treatment composition according to claim 17, wherein the mass concentration of hydroquinone is higher than the mass concentration of pyrogallol.

19. The treatment composition according to claim 14, wherein the pH is at least 13.

20. The treatment composition according to claim 14, wherein (c) contains zinc gluconate and / or magnesium gluconate.

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