Removal of hydrogen sulfide and / or mercaptan from petroleum or petroleum derivative and treatment composition for achieving removal

Abstract

To solve the problem that although, in a conventional method, it is shown that hydrogen sulfide in petroleum is reduced, a faster, more effective, more cost-efficient, and more environmentally friendly method is required for removing sulfur compounds including removing not only hydrogen sulfide but also mercaptans from crude oil and petroleum distillates.SOLUTION: An aqueous treatment composition for crude oil and / or petroleum distillates for removing sulfur compounds from crude oil and / or petroleum distillates, and a treatment method using the composition are disclosed. The composition comprises less than 0.5 mass% of a di- or tri-benzohydroxy compound, a strong base, less than 1 mass% of a divalent metal gluconate, and a balance of water, and has a pH of 9 or greater. The treatment method comprises adding the treatment composition to crude oil or petroleum distillates to form a mixture having 0.001-0.02 mass% of a di- or tri-benzohydroxy compound in petroleum and 0.001-0.03 mass% of a divalent metal gluconate in the petroleum, and mixing the components together.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] This application relates to the removal of hydrogen sulfide and / or mercaptans from petroleum, and more particularly, to their removal from crude oil and / or petroleum distillates by oxidation reactions induced by treatment with caustic solutions of divalent metal gluconates and di- or tri-benzohydroxy compounds. [Background technology]

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

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

[0005] [Table 1]

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

[0007] Additionally, sodium and residual alkalinity are added to the oil, which can make the oil corrosive and can cause scaling problems in pipelines and other infrastructure. Furthermore, at high pH, ​​the presence of sulfide ions can cause reactions with metals. Caustic washing can also create water-in-oil emulsions and foam due to 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. Triazines and other amines are commonly used liquid scavengers that remove hydrogen sulfide from petroleum, but residual triazines in the petroleum can cause fouling and corrosion of piping, towers, and other equipment. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 2,468,701 [Patent Document 2] U.S. Patent No. 4,206,194 [Patent Document 3] U.S. Patent No. 5,180,572 [Patent Document 4] U.S. Patent No. 6,746,611 Summary of the Invention [Problem to be solved by the invention]

[0010] While these methods have been shown to reduce hydrogen sulfide in petroleum, there is a continuing need to find more cost-effective and environmentally friendly methods that are both faster and more effective in removing sulfur compounds, including the removal of not only hydrogen sulfide but also mercaptans, from crude oil and petroleum distillates. [Means for solving the problem]

[0011] In a first aspect, a method for treating crude oil or petroleum distillate is disclosed. The method includes providing a crude oil or petroleum distillate requiring a reduction in the content of sulfur-containing compounds and adding thereto a treatment composition. The treatment composition has a pH of 9 or greater, (a) less than 1 percent by weight (% wt / wt) of di- or tri-benzohydroxy compounds; (b) Strong base; (c) less than 0.5% by weight of divalent metal gluconates; and (d) The remaining water Includes. 1. The method also includes mixing the treatment composition and crude oil or petroleum distillate to form a mixture containing 0.001% to 0.02% by weight of (a) in the petroleum and 0.001% to 0.03% by weight of (c) in the petroleum. Upon mixing, (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. Oxygen gas may be introduced during the addition and mixing. The source of oxygen gas may be ambient air. Optionally, the method may include adding 1000 ppm or less of a 30% by weight aqueous hydrogen peroxide solution after mixing the treatment composition with the crude oil or petroleum distillate, and rinsing the mixture with toluene, ozonated water, or hydrogen peroxide solution after reducing the amount of sulfur compounds present. Alternatively, the method may include adding 1000 ppm or less of polyethylene glycol 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 an amount of less than 0.2% by weight of the treatment composition, and (a) is hydroquinone and / or pyrogallol, more preferably hydroquinone and pyrogallol. The mass concentration of pyrogallol is greater than the mass concentration 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. 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 weight, more preferably less than 0.2% by weight, of di- or tri-benzohydroxy compounds; (b) Strong base; (c) less than 1% by weight of divalent metal gluconates; and (d) The remaining water and the treatment composition has a pH of 9 or greater, more preferably 13 or greater. In one embodiment, (a) is hydroquinone and / or pyrogallol, more preferably a mixture of hydroquinone and pyrogallol. For the mixture of hydroquinone and pyrogallol, the mass concentration of hydroquinone may be higher than the mass concentration of pyrogallol. (c) is zinc gluconate and / or magnesium gluconate, more preferably a mixture of zinc gluconate and magnesium gluconate.

[0015] In another embodiment, (a) less than 1% by weight of di- or tri-benzohydroxy compounds; (b) Strong base; (c) less than 1% by weight of metallic zinc powder; and (d) The remaining water and having a pH of 9 or greater. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a graph of the oxidative removal of pentanethiol in petroleum (starting at 100 ppm) as a function of pH when treated with an aqueous treatment composition. DETAILED DESCRIPTION OF THE INVENTION

[0017] The following detailed description will illustrate the general principles of the present invention, examples of which are further illustrated in the accompanying drawings.

[0018] As used herein, percent or the percent symbol is understood to mean percent by weight of the total composition unless expressly stated otherwise. It should also be noted that in specifying any range of concentrations or amounts, any particular upper concentration or amount may be accompanied by any particular lower concentration or amount.

[0019] Except in the examples or where otherwise expressly indicated, all numbers in this description expressing amounts, parts, percentages, ratios and proportions of ingredients, physical properties of ingredients, and reaction conditions will be understood as being modified by the word "about." As used herein, "about" means that a value is preferably within + / - 5% or more preferably + / - 2% of the value.

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

[0021] In a first aspect, a treatment composition for crude oil or petroleum distillates is described that oxidizes certain sulfur compounds. After oxidation, the oxidized sulfur compounds can be removed by extraction or washing, if necessary. Petroleum distillates, also known as horticulture oils, are separated from crude oil for many industrial uses. Mineral oil, naphtha, heavy fuel oil, wax, and benzene are exemplary distillates. The treatment composition reduces the presence of sulfur compounds through an oxidation mechanism with the treatment composition. More specifically, sulfur compounds such as hydrogen sulfide and mercaptans are converted to thiosulfates and disulfides, and optionally polysulfides, through an oxidation mechanism. The treatment composition has a pH of 9 or greater and contains, as a weight percent of the composition: (a) less than 0.5% by weight of di- or tri-benzohydroxy compounds; (b) a strong base in an amount sufficient to give a pH of 9 or greater; (c) less than 1% by weight of a divalent metal gluconate; (d) the balance water; Includes. The pH is more preferably 11 or greater, 12 or greater, or 13 or greater. Having a pH of 11.5 or greater places the pH above the second pKa of hydrogen sulfide. The pH is controlled by a strong base. The strong base can be NaOH and / or KOH. In one embodiment, the strong base is a mixture of NaOH (50% solution) and KOH (40% solution) in a ratio of about 1:1 by weight. For example, NaOH is commercially available in concentrated form as 50% by weight in water, and KOH is commercially available in concentrated form as either 40% or 45% by weight in water; a blend thereof in a 1:1 ratio would be a mixture of 100 ml of concentrated NaOH to 100 ml of concentrated KOH, or 1 L to 1 L, etc. 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 processing solution, including but not limited to viscosity, density, and balancing cation concentration for improved solubility in the final product.

[0022] The di- or tri-benzohydroxy compound is more preferably present in an amount of less than 0.4% by weight, or less than 0.3% by weight, and even more preferably less than 0.2% by weight of the treatment composition. The di- or tri-benzohydroxy compound is selected from the group consisting of hydroquinone (1,4-dibenzenediol), 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-benzohydroxy compound is a mixture of hydroquinone and pyrogallol, wherein the mass concentration of pyrogallol is greater than the mass concentration of hydroquinone. The mass percentage of pyrogallol may be 500 times that of hydroquinone, for example, 0.1% by weight pyrogallol to 0.0002% by weight hydroquinone. Pyrogallol is an oxygen scavenger. Therefore, pyrogallol can deliver oxygen gas from the headspace in the reaction vessel to the crude oil or petroleum distillate, participating in the oxidation mechanism of the reaction. Petroleum profiles by gas chromatography and mass spectrometry have not shown any change in the hydrocarbon composition of the petroleum. Introducing small amounts of oxygen from the air into petroleum can be effective in "sweetening" the petroleum (i.e., by oxidizing mercaptans and hydrogen sulfide), but not so strong as to oxidize the petroleum. However, in some cases, there has been a decrease in asphaltene content.

[0023] The divalent metal gluconate is more preferably present in an amount of less than 0.8% by weight, or less than 0.7% by weight, and even more preferably less than 0.6% by weight 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 weight zinc gluconate to 0.05% by weight magnesium gluconate.

[0024] In one embodiment, the treatment composition has a pH greater than 11 and comprises, as a weight percent of the composition: (a) about 0.1% by weight of a di- or tri-benzohydroxy compound; (b) a strong base in an amount that gives a pH greater than 11; (c) about 0.55% by weight of a divalent metal gluconate; and (d) The remaining water Includes.

[0025] More preferably, the pH is about 13. In all embodiments, the strong base may be a mixture of NaOH and KOH. In one embodiment, the NaOH is about 22% by weight and the KOH is about 20% by weight of the aqueous treatment composition.

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

[0027] Interestingly, the combination of di- or tri-benzohydroxy compounds and divalent metal gluconates is highly effective in oxidizing sulfides and mercaptans in crude oil or petroleum distillates. The inventors conducted trials in which, depending on the dosage of the aqueous treatment composition introduced to the crude oil or petroleum distillate, mercaptan levels were reduced by at least 50% in three hours and up to 99.9% in one hour. Hydrogen sulfide levels were reduced by 88% in the first half hour. Zinc is known to reduce quinones to hydroquinones. Zinc can also catalyze the oxidation of sulfides by semiquinone radicals. The oxidation of sulfides by hydroquinone is thermodynamically unfavorable without a catalyst.

[0028] Our experiments began with a caustic solution combined with hydroquinone and zinc powder, followed by a caustic solution combined with flavin and zinc powder in a model solution with known concentrations of pentanethiol to detect whether mercaptan concentrations were reduced. This was not effective in oxidizing sufficient amounts of sulfur compounds. Furthermore, it was difficult to preserve zinc powder in solution. Zinc gluconate was tested as an alternative because it is said to generate peroxy and hydroxyl radicals in the presence of sulfides. As shown in Table 1 below, zinc gluconate performed better than zinc powder.

[0029] Several chelation examples were tried, both alone and in combination with hydroquinone and zinc powder and their variants. EDTA, a model chelating agent, 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 bound the zinc powder, reducing performance.

[0030] In another aspect, a method for treating crude oil or petroleum distillate with the aqueous treatment composition described above is described below. A crude oil or petroleum distillate requiring a reduction in the content of sulfur-containing compounds is prepared. The aqueous treatment composition is added to the crude oil or petroleum distillate at a predetermined concentration. The dosage may be 1% by weight or less of the petroleum. Dosages in this range have resulted in at least a 50% reduction in mercaptan concentrations in as little as 1 to 3 hours. A 1% by weight dosage of the aqueous treatment composition results in a 64% reduction in total mercaptans in as little as 1 to 3 hours. Smaller dosages of the aqueous treatment composition, such as 0.1% by volume, have been tested on various types of petroleum, typically resulting in a 50% reduction in total mercaptans in 12 hours. Therefore, higher dosages of the aqueous treatment composition react more quickly and result in a higher conversion of mercaptans to disulfides.

[0031] Because the aqueous treatment composition is aqueous, the treatment method involves adding water to the petroleum. The solubility of water in petroleum depends on the viscosity and other characteristics of the petroleum. When the water solubility of the petroleum is exceeded, the water will separate. Typically, adding 0.1% of the aqueous treatment composition will not cause separation of the aqueous phase, while adding 1% will create a thin film of aqueous phase at the bottom of the petroleum.

[0032] The addition may be with or without stirring, although stirring provided better results. For example, a 1% by weight dosage of the aqueous treatment composition, when left unstirred for several hours, was found to form a layer within the oil, with samples taken from the top having a much lower concentration of total mercaptans than samples taken from the bottom of the oil sample. Furthermore, when this "layered" sample was again stirred and subsequently measured, the mercaptan concentration was lower than in a control crude oil sample. Thus, both oxidation and precipitation were occurring in the sample.

[0033] In one embodiment, the treated petroleum mixture contains 0.001% to 0.02% by weight of di- or tri-benzohydroxy compounds in the petroleum and 0.001% to 0.03% by weight of divalent metal gluconate in the petroleum. The presence of di- or tri-benzohydroxy compounds and divalent metal gluconate compounds in the crude oil or petroleum distillate 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 predetermined period of time, such as at least one hour. In one embodiment, the availability of oxygen gas, such as ambient air, is controlled by placing the crude oil or petroleum distillate in a sealed container with a selected amount of headspace containing ambient air. Oxygen in the headspace from the air (autoxidation) and / or oxygen in the water is available to react with sulfides to produce sulfates. Transition metal ions catalyze the oxidation of HS and mercaptans. Water passed through sulfide-containing petroleum gave sulfides, but after treatment with the aqueous treatment composition described above, the sulfides were converted to sulfates and / or thiosulfates as well as sulfite ions, according to infrared (IR) results and colorimetry (spectroscopy) for the identification of sulfides, sulfites, and sulfates.

[0034] In all embodiments, the di- or tri-benzohydroxy 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] The treatment method may also include the addition of an aqueous solution of hydrogen peroxide at a predetermined parts per million (ppm) concentration. The hydrogen peroxide solution may be a 30% by weight or less solution, such as a 10% by weight solution, a 2% by weight solution, or a 1% by weight solution. The hydrogen peroxide is added after the aqueous treatment composition is mixed with the crude oil or petroleum distillate, generally at least 10 minutes after the treatment composition. In one embodiment, the hydrogen peroxide is added one-half hour after the treatment composition. In another embodiment, the hydrogen peroxide is added one hour after the treatment composition.

[0036] This method may also include post-treatment washing of the petroleum mixture. The washing medium may be toluene, ozonated water, or hydrogen peroxide solution (2% to 30% solution). Toluene reacts with hydroxides in the aqueous treatment composition to form benzyl alcohol / aldehyde, so excess caustic from overdosing this product on the petroleum can be consumed by adding toluene to the petroleum. If a liquid-liquid extraction method is desired, ozonated water or hydrogen peroxide solution may be introduced after the initial chemical reaction has slowed (typically after 3 hours). Both reduce the total sulfur content of the petroleum. The inventors have attempted to use hydrogen peroxide to assist the mercaptan oxidation mechanism. However, the inventors have also attempted to use peroxide to react 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 have found that after stirring is stopped, the gluconates (sugars) settle as a thin film to the bottom of the petroleum. When hydrogen peroxide was added without stirring, it settled to the bottom and reacted with gluconate to form a precipitate. Gluconate is stable at high pH, ​​but decomposes when it reacts with hydrogen sulfide (i.e., hydrogen sulfide is oxidized). The inventors previously identified the free radical mechanism using electron spin resonance spectroscopy.

[0037] The method may include removing water from the treated petroleum, the water originating from the aqueous treatment composition. This may be accomplished by adding an emulsifier. One example is polyethylene glycol (PEG). PEG may be added at up to about 1000 ppm. 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 is performed on a small test sample by adding approximately 10% by volume of water through the oil and measuring the pH. If the pH is above 10, a small amount of toluene is added, allowed to stand for several hours or overnight, and the oil is jar tested again. The resulting pH should be in the range of 9 to 10. If the jar test wash water has a pH above 10, this indicates unused hydroxyl ions that can be corrosive in pipelines, etc. It has been found that when H2S and mercaptans are present in the oil, the water from the oil wash has a negative redox potential (e.g., -250 mV). The water passed through the treated oil should optimally have a pH of approximately 9 and a redox potential of approximately -100 mV to +25 mV. [Example]

[0039] The basic procedure used to form the aqueous treating compositions used in the following examples is as follows: 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 an approximately 1.1:1 mixture. The substance to be tested as a treating agent, such as hydroquinone, pyrogallol, zinc gluconate, magnesium gluconate, etc., was then added in an amount sufficient to give the concentration shown in the Examples table below. Each solution was stirred for 1 hour with a controlled amount of headspace in the covered container.

[0040] After preparing the test solutions according to the above procedure, petroleum samples were prepared, typically as 100 mL samples. The petroleum samples used in the examples herein contained mercaptans such as ethanethiol, butanethiol, and pentanethiol. Testing showed that pentanethiol was the easiest to detect and measure. Mass spectrometry analysis 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 pentanethiol peak diminished).

[0041] Each aqueous treatment composition was added to each petroleum sample at a predetermined dosage. In most examples, the aqueous treatment composition was added in an amount of 1% by 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 limits of quantitation in UOP 163 are 0.2 ppm by weight of mercaptans (as sulfur) and 1.0 ppm by weight of hydrogen sulfide (as sulfur). Doses may vary, and if the dosage is other than 1%, it will be specified in the examples below. Longer stirring times, greater than 1 hour, are also possible, as is also indicated in the examples below.

[0042] Example 1 Crude oil samples were obtained and tested in 100 ml samples according to various processing possibilities. 100 ppm pentanethiol was added to each crude oil sample to establish a known baseline for measuring the reduction in mercaptan levels. The titration method described above was used to measure the pentanethiol ppm in this example. After a one-hour incubation period, the unspiked control sample had 48 ppm pentanethiol (time was allowed for the chemical reaction to proceed before the sample was analyzed). After one hour at room temperature and pressure, the spiked control sample had 233 ppm pentanethiol. The samples were reacted at room temperature and pressure in a sealed vessel (such as by a screw-on lid fastened to the reaction vessel) using a magnetic stir plate at a moderate speed (e.g., 500-1000 rpm) for a preset time. The vessel had limited headspace, approximately 20 percent headspace in some examples. Therefore, although ambient air may initially contact the petroleum when pouring it or during the addition of the aqueous treatment composition, the sealed container limits the introduction of air (a source of oxygen gas) into the petroleum and minimizes evaporation (volatilization) of mercaptans from the sample.

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

[0044] [Table 2]

[0045] Run 5 was repeated two more times for a 12-hour detection time. In one run, the ppm of pentanethiol was again below the detection limit, and in the other, it was 9 ppm. Each pH level successfully reduced the ppm of pentanethiol, with the amount of reduction increasing as the pH increased. As seen in Run 4, pyrogallol (trihydroxybenzene) alone did not oxidize the mercaptans.

[0046] Referring to Figure 1, the aqueous treatment compositions had NaOH / KOH concentrations sufficient to establish solution pHs (11, 12, 13, and 14, respectively), zinc gluconate concentrations of 0.1% by weight in the solution, and 1,4-benzenediol concentrations of 0.05% by weight. The percent removal of mercaptans at each pH is shown in Figure 1. As the pH increased, the percent of mercaptans removed also increased.

[0047] Example 2 Pyrogallol was investigated further by adding 100 ppm of pentanethiol to a control oil and then testing it using the standard titration method.

[0048] [Table 3]

[0049] As can be seen in Run 4 of Table 1 above, pyrogallol by itself in a high pH aqueous solution is not effective. As can be seen in Run 12, pyrogallol in combination with zinc gluconate reduced the concentration of pentanethiol present in the petroleum sample. A 25% reduction in pentanethiol was observed, which is much less effective than the hydroquinone run in Table 1. However, pyrogallol remains in solution better than hydroquinone at the concentrations tested above. The inventors found that it was necessary to filter solutions containing hydroquinone to prevent precipitation.

[0050] In tests where hydrogen peroxide was added after treatment, a 2% solution was not strong enough. The inventors used a 30% solution of hydrogen peroxide in Trial 11 above. Hydrogen peroxide is not mixed into the treatment composition because it can cause an undesirable exothermic reaction. Instead, as explained above, hydrogen peroxide is added after the aqueous treatment composition is mixed into the oil for an incubation period.

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

[0052] [Table 4]

[0053] Trials 14-16 each successfully reduced the pentanethiol present. Zinc gluconate alone reduced the ppm concentration of mercaptans by 68% in 1 hour and by 74% in 2 hours. Adding hydroquinone to the zinc gluconate further oxidized the mercaptans, reducing them by 86% in 2 hours and 89% in 12 hours.

[0054] Example 4 Magnesium gluconate was tested. Magnesium gluconate was considered an alternative to zinc gluconate. However, magnesium gluconate has low solubility. The control in the table below was an unspiked crude oil sample.

[0055] [Table 5]

[0056] The trace amount of hydroquinone in the above trial was 2 ppm. The aqueous treatment composition alone was effective in reducing the mercaptan concentration by 33%. This same treatment composition, followed by the addition of 150 ppm of a 30% hydrogen peroxide solution, resulted in no detectable mercaptans.

[0057] Run 17 was repeated with the sample having 10 ppm pentanethiol added followed by 150 ppm hydrogen peroxide. There was no significant improvement in reducing mercaptan levels. Magnesium gluconate was added to the treatment composition.

[0058] [Table 6]

[0059] Even without the addition of hydrogen peroxide, the aqueous treatment composition having both zinc gluconate and magnesium gluconate performed better in reducing the mercaptans present in the crude oil sample. Various trials conducted revealed that magnesium gluconate is suitable for the aqueous treatment composition. Surprisingly, adding magnesium gluconate together with zinc gluconate improved the effectiveness of reducing the mercaptans in the sample.

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

[0061] Example 5 Next, the inventors retested the formulation of Run 20 with increased amounts of pentanethiol added.

[0062] [Table 7]

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

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

[0065] Crude oil was treated. The resulting petroleum contained 32.6 ppm total mercaptans. The petroleum was analyzed by titration, UOP 163. A 1-liter aliquot (Sample 1) of the petroleum was treated with 1000 ppm of the aqueous treatment composition while stirring. A second 1-liter aliquot (Sample 2) of the petroleum was treated with a 500 ppm dose of the aqueous treatment composition while stirring. Both petroleum samples were sealed with screw caps before and after the addition of the aqueous treatment composition. The samples were stirred on a stir plate at 500 rpm for 2 hours. The samples were then removed from the stir plate and allowed to sit overnight (12 hours). The container had approximately 20 percent headspace. This implies that although ambient air may initially contact the petroleum when pouring or during the addition of the aqueous treatment composition, the sealed container prevents continuous introduction of air into the petroleum, minimizing evaporation (volatilization) of mercaptans from the sample.

[0066] After 12 hours, both samples were tested by titration according to method UOP 163. The crude oil control sample had 32.6 ppm mercaptans (natural, i.e., no additional mercaptans 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 We 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 (SUPELCO® brand DVB / CAR / PDMS (divinylbenzene / carboxene / polydimethylsiloxane)). For quantification, a standard curve was generated using pentanethiol standards across a range of concentrations using SPME, with each standard or sample containing a fixed concentration of the internal standard. The pentanethiol response was normalized to the response of the internal standard, a quality assurance measure.

[0070] In this trial, pentanethiol was spiked into petroleum containing <5 ppm of natural pentanethiol. The measured total pentanethiol was determined to be 50 ppm. The inventors found that the spiked petroleum was more susceptible to oxidation than the natural mercaptans in the petroleum, likely because the mercaptans were bound or strongly associated with the hydrocarbons in the petroleum through hydrophobic interactions, van der Waals forces, etc.

[0071] [Table 9]

[0072] LOQ stands for "limit of quantitation." In the test method used, the LOQ was 1 ppm.

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

[0074] It should be noted that the embodiments are not limited in their application or use to the details of the configurations and processes described herein. Features of the exemplary embodiments, configurations, and variations may be implemented or incorporated in other embodiments, configurations, variations, and modifications, and may be practiced or carried out in various ways. Furthermore, unless otherwise specified, the terms and phrases employed herein have been chosen for the convenience of the reader for the purpose of describing exemplary embodiments of the invention, and not for the purpose of limiting the invention. In short, it is the applicant's intent that the scope of any patent issued hereby be limited only by the appended claims.

Claims

1. 1. A method for treating crude oil or petroleum distillates, comprising: providing a crude oil or petroleum distillate requiring a reduction in the content of sulfur-containing compounds; adding a treatment composition to the crude oil or petroleum distillate, wherein the treatment composition has a pH of 9 or greater; (a) less than 1% by weight of di- or tri-benzohydroxy compounds; (b) Strong base; (c) less than 0.5% by weight of divalent metal gluconates; and (d) The remaining water and mixing the treatment composition and crude oil or petroleum distillate to form a mixture comprising 0.001% to 0.02% by weight of (a) in the petroleum and 0.001% to 0.03% by weight of (c) in the petroleum; Including, A process 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. 10. The method of claim 1, wherein (a) is present at less than 0.2% by weight of the treatment composition.

3. 3. The method of claim 2, wherein (a) comprises hydroquinone and / or pyrogallol.

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

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

6. 10. The method of claim 1, wherein the pH is at least 13.

7. 2. The method of claim 1, wherein (c) comprises zinc gluconate and / or magnesium gluconate.

8. 10. The method of claim 1, wherein the adding and mixing is carried out in the presence of oxygen gas.

9. 9. The method of claim 8, wherein the oxygen gas source is ambient air.

10. 10. The method of claim 1, further comprising the step of adding up to 1000 ppm of a 30 wt. % aqueous hydrogen peroxide solution after mixing the treatment composition with the crude oil or petroleum distillate.

11. 11. The method of claim 10, further comprising the step of washing the mixture with toluene, ozonated water, or hydrogen peroxide solution after reducing the amount of sulfur compounds present.

12. 10. The method of claim 1, further comprising the step of adding up to 1000 ppm of polyethylene glycol after mixing the treatment composition with the crude oil or petroleum distillate.

13. 10. The method of claim 1, wherein the mixing step is for at least 1 hour.

14. (a) less than 1% by weight of di- or tri-benzohydroxy compounds; (b) Strong base; (c) less than 1% by weight of divalent metal gluconates or metallic zinc powder; and (d) balance water; 1. A treatment composition for crude oil and / or petroleum distillates comprising:

15. 15. The treatment composition of claim 14, wherein (a) is less than 0.5% by weight of a di- or tri-benzohydroxy compound and (c) is a divalent metal gluconate.

16. 16. The treatment composition of claim 15, wherein (a) is present at less than 0.2 wt.%.

17. 17. The treatment composition of claim 16, wherein (a) comprises hydroquinone and / or pyrogallol.

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

19. 15. The treatment composition of claim 14, wherein the pH is at least 13.

20. 15. The treatment composition of claim 14, wherein (c) comprises zinc gluconate and / or magnesium gluconate.

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