Removal of hydrogen sulfide and / or mercaptans from oil or oil derivatives and treatment composition for implementing same

Abstract

Disclosed are aqueous treatment compositions for crude oil and / or petroleum fractions to remove sulfur compounds therefrom and treatment processes using such compositions. The composition has less than 0.5% wt / wt of a di-or tri-benzo-hydroxy compound, a strong base, less than 1% wt / wt of a divalent metal gluconate, the balance water and a pH of 9 or greater. The treatment process comprises adding the treatment composition to a crude oil or petroleum fraction to form a mixture having from 0.001% to 0.02% wt of a di-or tribenzohydroxy compound / wt oil and from 0.001% to 0.03% wt of a divalent metal gluconate / wt oil, and mixing them together.

Description

Related Applications

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

[0002] The present application relates to the removal of hydrogen sulfide and / or mercaptans from oils, more particularly from crude oils and / or petroleum fractions, by oxidation reactions caused by treatment with alkaline solutions of divalent metal gluconates and di- or tribenzohydroxy compounds. Background Art

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

[0004] A large number of sulfur compounds can be present in crude oil. The table below has the sulfur compounds listed in order of increasing difficulty to remove from crude oil (easier at the top than at the bottom).

[0005] A common treatment process for crude oil is alkali washing. Alkali washing removes sulfides from crude oil and petroleum fractions. Although this method is relatively simple and inexpensive, it cannot remove all forms of sulfur, particularly organic sulfides, and it creates a large amount of caustic soda (NaOH / KOH) wastewater that is harmful to the environment. Wastewater is usually collected in large ponds for post-treatment. Such post-treatment is expensive and time-consuming.

[0006] In addition, the oil is endowed with sodium and residual alkalinity, which can make the oil corrosive and can cause scaling problems in pipelines and other infrastructure. Moreover, at high pH, ​​the presence of sulfide ions can cause reactions with metals. Alkali washing can also cause water-in-oil emulsions and foams from the saponification of fatty acids in the oil.

[0007] Others have tried dry gas desulfurization, hydrodesulfurization, and biodesulfurization, which is a much more expensive process. Triazines and other amines are commonly used liquid scavengers to strip hydrogen sulfide from oil, but residual triazines in the oil can cause scaling and corrosion of pipes, towers, and other equipment.

[0008] While these methods have been shown to reduce hydrogen sulfide in oil, there is a continuing need to find more cost-effective, more environmentally friendly processes that also more quickly and efficiently remove sulfur compounds, including mercaptans, from crude oil and petroleum fractions, in addition to hydrogen sulfide. Summary of the invention

[0009] In a first aspect, a method for treating crude oil or a petroleum fraction is disclosed. The method comprises providing a crude oil or a petroleum fraction in which the sulfur compound content needs to be reduced, and adding a treatment composition thereto. The treatment composition has a pH of 9 or greater and comprises: (a) less than 1% wt / wt of di- or tri-benzohydroxy compounds; (b) strong bases; (c) less than 0.5% wt / wt divalent metal gluconate; and (d) The balance is water. 1. The method further comprises mixing the treatment composition with crude oil or petroleum fractions to form a mixture comprising 0.001% to 0.02% wt (a) / wt oil and 0.001% to 0.03% wt (c) / wt oil. After mixing, (a) oxidizes sulfur compounds in the crude oil or petroleum fraction in the presence of (c), thereby reducing their amount in the crude oil or petroleum fraction. Oxygen may be introduced during the addition and mixing. The source of oxygen may be ambient air. The method may optionally comprise adding 1000 ppm or less of a 30% wt / wt aqueous hydrogen peroxide solution after mixing the treatment composition with the crude oil or petroleum fraction, and washing the mixture with toluene, ozone water or hydrogen peroxide solution after reducing the amount of sulfur compounds present. Alternatively, the method may comprise adding 1000 ppm or less of polyethylene glycol after mixing the treatment composition with the crude oil or petroleum fraction.

[0010] Typically, the sulfur compound is hydrogen sulfide and / or mercaptans. In one embodiment, (a) is present at less than 0.2% wt / wt of the treatment composition, and (a) is hydroquinone and / or pyrogallol, more preferably hydroquinone and pyrogallol. The wt / wt concentration of pyrogallol is greater than the wt / wt concentration of hydroquinone.

[0011] 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 performed for at least one hour, more preferably at least two hours.

[0012] In another aspect, a treatment composition for crude oil and / or petroleum fractions is disclosed. The treatment composition comprises: (a) less than 0.5% wt / wt of di- or tri-benzohydroxy compounds, more preferably less than 0.2% wt / wt; (b) strong bases; (c) less than 1% wt / wt divalent metal gluconate; and (d) Residual water; wherein 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 a mixture of hydroquinone and pyrogallol, the wt / wt concentration of hydroquinone may be greater than the wt / wt concentration of pyrogallol. (c) is zinc gluconate and / or magnesium gluconate, more preferably a mixture of zinc gluconate and magnesium gluconate.

[0013] In a further aspect, disclosed is a treatment composition for crude oil and / or petroleum fractions having: (a) less than 1% wt / wt of di- or tri-benzohydroxy compounds; (b) strong bases; (c) less than 1% wt / wt metallic zinc powder; and (d) Residual water; wherein the treatment composition has a pH of 9 or greater. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The graph is a plot of the removal of pentanethiol (starting at 100 ppm) from oil by oxidation as a function of pH when treated with an aqueous treatment composition. DETAILED DESCRIPTION

[0015] The following detailed description will illustrate the general principles of the invention, examples of which are additionally provided in the accompanying drawings.

[0016] As used herein, unless expressly specified otherwise, percentages or percentage symbols should be understood to mean weight percent of the total composition. It should also be noted that when any range of concentrations or amounts is specified, any particular upper concentration or amount can be associated with any particular lower concentration or amount.

[0017] Except in the working examples or where otherwise explicitly stated, all numbers in this specification indicating amounts, parts, percentages, ratios and proportions of materials, physical properties of materials and reaction conditions are to be understood as modified by the word "about". As used herein, "about" means that a value is preferably + / - 5% or more preferably + / - 2%.

[0018] As used herein, "room temperature" means 25°C + / - 5°C, more preferably + / - 2°C.

[0019] In a first aspect, a treatment composition for crude oil or petroleum fractions is described, wherein the treatment composition oxidizes certain sulfur compounds therein. After oxidation, the oxidized sulfur compounds can be removed by extraction or washing, if desired. Petroleum fractions (also known as horticultural oils) are separated from crude oil for many industrial uses. Mineral oil, naphtha, heavy fuel oil, wax, and benzene are example fractions. The treatment composition reduces the presence of sulfur compounds through its oxidation mechanism. More specifically, sulfur compounds (such as hydrogen sulfide and mercaptans) are converted to thiosulfates and disulfides, and possibly polysulfides, via the oxidation mechanism. The treatment composition has a pH of 9 or greater and includes, by weight percentage of the composition: (a) less than 0.5% wt / wt of di- or tri-benzohydroxy compounds; (b) a strong base in an amount to provide a pH of 9 or greater; (c) less than 1% wt / wt divalent metal gluconate; and (d) Residue of water. The pH is more preferably 11 or greater, 12 or greater, 13 or greater. By having a pH of 11.5 or greater than 11.5, the pH is or greater than 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 % wt / wt. For example, NaOH is commercially available in its concentrated form (50% wt / wt in water) and KOH is commercially available in its concentrated form (either 40% or 45% wt / wt in water), and a blend of 1:1 of the ratio thereof is a mixture of 100 ml of concentrated NaOH and 100 ml of concentrated KOH, or 1 L and 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 generally selected to balance the overall properties of the processing solution, including but not limited to the balance of viscosity, density, and cation concentration, for enhanced solubility of the final product.

[0020] The di- or tri-benzohydroxy compound is more preferably present at less than 0.4% wt / wt of the treatment composition, or less than 0.3% wt / wt of the treatment composition, and even more preferably less than 0.2% wt / wt of the treatment composition. The di- or tri-benzohydroxy compound is selected from the group consisting of hydroquinone (1,4-dihydroquinone), pyrogallol (1,2,3-trihydroxybenzene), gallic acid (3,4,5-trihydroxybenzoic acid) and 1,2,4-pyrogallol and combinations thereof. In one embodiment, the di- or tri-benzohydroxy compound is a mixture of hydroquinone and pyrogallol, and the wt / wt concentration of pyrogallol is greater than the wt / wt concentration of hydroquinone. The wt / wt percentage of pyrogallol can be 500 times greater than that of hydroquinone, for example, pyrogallol is 0.1% wt / wt and hydroquinone is 0.0002% wt / wt. Pyrogallol is an oxygen scavenger. Thus, pyrogallol can bring oxygen from the headspace of the reaction vessel into the crude oil or petroleum fraction to participate in the oxidation mechanism of the reaction. The characteristics of the oil analyzed by gas chromatography and mass spectrometry show that the composition of hydrocarbons in the oil is unchanged. The introduction of small amounts of oxygen from the air into the oil can effectively "sweeten" the oil (i.e., via oxidation of mercaptans and hydrogen sulfide), but its intensity is not enough to oxidize the oil. However, in some cases, the asphaltene content is reduced.

[0021] The divalent metal gluconate is more preferably present at less than 0.8% wt / wt, or less than 7% wt / wt and even more preferably less than 6% wt / wt 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 wt / wt concentration of zinc gluconate is greater than the wt / wt concentration of magnesium gluconate. The wt / wt percentage of zinc gluconate can be 10 times greater than that of magnesium gluconate, for example, 0.5% wt / wt of zinc gluconate to 0.05% wt / wt of magnesium gluconate.

[0022] In one embodiment, the treatment composition has a pH greater than 11 and comprises, by weight percent of the composition: (a) about 0.1% wt / wt of a di- or tri-benzohydroxy compound; (b) a strong base in an amount to provide a pH greater than 11; (c) about 0.55% wt / wt divalent metal gluconate; and (d) Residue of water.

[0023] The pH is more preferably about 13. In all embodiments, the strong base may be a mixture of NaOH and KOH. In one embodiment, NaOH is about 22% wt / wt of the aqueous treatment composition and KOH is about 20% wt / wt of the aqueous treatment composition.

[0024] In all embodiments, the di- or tribenzohydroxy compound may be a mixture of pyrogallol and hydroquinone. In one embodiment, pyrogallol is 0.1% wt / wt of the aqueous treatment composition and hydroquinone is 0.0002% wt / wt of the aqueous treatment composition. In all embodiments, the divalent metal gluconate may be a mixture of zinc gluconate and magnesium gluconate. In one embodiment, zinc gluconate is 0.5% wt / wt of the aqueous treatment composition and magnesium gluconate is 0.05% wt / wt of the aqueous treatment composition.

[0025] Interestingly, the combination of di- or tri-benzohydroxy compounds and divalent metal gluconates are highly effective in oxidizing sulfides and mercaptans in crude oil or petroleum fractions. We have tested where mercaptan levels were reduced by at least 50% within 3 hours and up to 99.9% within 1 hour, depending on the dosage of the aqueous treatment composition introduced into the crude oil or petroleum fraction. Hydrogen sulfide was reduced by 88% within the first half hour. Zinc is known to reduce quinones to hydroquinone. Zinc can also catalyze the oxidation of sulfides via the semiquinone free radical. The oxidation of sulfides by hydroquinone is not thermodynamically favorable in the absence of a catalyst.

[0026] Our experiments started with a combination of alkaline solution with hydroquinone and zinc powder, and then with flavin and zinc powder in a model solution spiked with known concentrations of pentamethylenethiol to test whether the thiol concentration was reduced. This is not effective in oxidizing sufficient amounts of sulfur compounds. Also, keeping the zinc powder in solution is difficult. Zinc gluconate was tested as an alternative because it is said to produce peroxy and hydroxyl radicals in the presence of sulfides. Zinc gluconate performed better than zinc powder, as shown in Table 1 below.

[0027] Several chelation examples were tried, alone and in combination with hydroquinone and zinc powder and variants thereof. The model chelator EDTA is known to stabilize hydrogen sulfide in solutions that inhibit oxidation processes. However, iron chelates in hydroxyl form (such as Fe-EDTA) are used to remove hydrogen sulfide from natural gas by oxidative absorption, whereby hydrogen sulfide is oxidized to elemental sulfur. We found that the chelator binds the zinc powder and degrades performance.

[0028] In another aspect, the method for treating crude oil or petroleum fractions using the aqueous treatment composition described above is described below. A crude oil or petroleum fraction that needs to reduce the content of sulfur-containing compounds is provided. Aqueous treatment composition. Aqueous treatment composition with a preselected concentration is added to the crude oil or petroleum fraction. The dosage can be 1%wt / wt or less than 1%wt / wt relative to the oil. Dosages within this range produce a reduction of at least 50% of the mercaptan concentration within just 1 hour to 3 hours. A 1%wt / wt dosage of aqueous treatment composition produces a reduction of 64% of total mercaptans within just 1 hour to 3 hours. A smaller number of aqueous treatment compositions, such as 0.1% by volume, have been tested on different types of oils, and a 50% reduction in total mercaptans generally occurs within a period of 12 hours. Therefore, higher dosages of aqueous treatment compositions react faster, and mercaptans are converted to a higher percentage of disulfides.

[0029] Since the aqueous treatment composition is water-based, the treatment process will add water to the oil. The solubility of water in the oil depends on the viscosity and other properties of the oil. Once the water solubility of the oil is exceeded, the water will separate out. Typically, adding 0.1% of the aqueous treatment composition will not cause the water phase to separate, but a 1% addition will form a thin film of water phase at the bottom of the oil.

[0030] Dosing can be done with or without stirring, but better results occur with stirring. For example, it was found that a 1% wt / wt dose of the aqueous treatment composition, when left for several hours without stirring, formed a layer within the oil, wherein a sample from the top had a much lower total mercaptan concentration than a sample taken from the bottom of the oil sample. Moreover, when this "layered" sample was stirred again and then measured, the concentration of mercaptans was lower than that of the control crude oil sample. Thus, both oxidation and sedimentation occurred in the sample.

[0031] In one embodiment, the treated oil mixture comprises 0.001% to 0.02%wt of di- or tri-phenyl hydroxyl compounds / wt oil and 0.001% to 0.03%wt of divalent metal gluconate / wt oil. In crude oil or petroleum fractions, the presence of di- or tri-phenyl hydroxyl compounds and divalent metal gluconate compounds reduces the amount of sulfur compounds present therein. The sulfur compound can be hydrogen sulfide and / or one or more mercaptans. The crude oil or petroleum fractions are stirred for a preselected time period, such as at least one hour. In one embodiment, by placing crude oil or petroleum fractions in a sealed container with a headspace containing a selected amount of ambient air, control access to oxygen gas (such as in ambient air). Oxygen in the headspace from air (auto-oxidation) and / or water can be used to react with sulfide to produce sulfate. Transition metal ions catalyze the oxidation of H2S and mercaptans. Passing water over oil containing sulfide produces sulfide, but after treatment with the aqueous treatment composition described above, the sulfide is converted into sulfate and / or thiosulfate and sulfite ions based on infrared (IR) results and colorimetry (spectrophotometry) for identifying sulfide, sulfite and sulfate.

[0032] In all aspects, the di- or tri-phenylhydroxy compound is hydroquinone and / or pyrogallol, more preferably a mixture of hydroquinone and pyrogallol. The wt / wt concentration of pyrogallol is greater than the wt / wt concentration of hydroquinone. In all aspects, the divalent metal gluconate is zinc gluconate and / or magnesium gluconate, more preferably a mixture of zinc gluconate and magnesium gluconate. The wt / wt concentration of zinc gluconate is greater than the wt / wt concentration of magnesium gluconate.

[0033] The treatment method may also include adding an aqueous solution of hydrogen peroxide at a predetermined parts per million (ppm) concentration. The hydrogen peroxide solution may be a 30% wt / wt solution or less, such as a 10% wt / wt solution, a 2% wt / wt solution, or a 1% wt / wt solution. The hydrogen peroxide is added after the aqueous treatment composition is mixed with the crude oil or petroleum fraction, typically at least 10 minutes after the treatment composition. In one embodiment, the hydrogen peroxide is added half an hour after the treatment composition. In another embodiment, the hydrogen peroxide is added one hour after the treatment composition.

[0034] The method may include post-treatment washing of the oil mixture. The washing medium may be toluene, ozone water or hydrogen peroxide solution (2% to 30% solution). Toluene reacts with the hydroxide in the aqueous treatment composition to form benzyl alcohol / aldehyde, so excess alkali added to the oil from the product in excess can be consumed by adding toluene to the oil. If a liquid-liquid extraction process is required, ozone water or hydrogen peroxide solution may be introduced after the initial chemical reaction slows down (usually after 3 hours). Both reduce the total sulfur content in the oil. We have tested where hydrogen peroxide contributes to the oxidation mechanism of mercaptans. However, we have also tested where peroxide reacts with divalent metal gluconates to form dimers that precipitate from the oil mixture. This can be beneficial because the oil can be more easily removed and decanted from the precipitate. We found that after stirring stopped, gluconates (sugars) were deposited to the bottom of the oil as a film. When hydrogen peroxide was added without stirring, it was deposited to the bottom and reacted with gluconates to form a precipitate. Gluconate is stable at high pH but decomposes upon reaction with hydrogen sulfide (ie, when the hydrogen sulfide is oxidized). We have tentatively identified a free radical mechanism using electron spin resonance spectroscopy.

[0035] The method may include removing water from the treated oil, the water coming from the aqueous treatment composition. This may be achieved by adding 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.

[0036] To test for residual alkalinity, jar-testing of a small test sample is performed by adding about 10% by volume of water to the oil and determining the pH. If the pH is greater than 10, a small amount of toluene is added and left for a few hours or overnight, and the oil is jar-tested again. The resulting pH should be in the range of 9 to 10. If the wash water in the jar test has a pH above 10, it indicates that there are unexhausted hydroxyl ions, which can be corrosive in pipelines, etc. When H2S and mercaptans are present in the oil, the water from the water wash of the oil is found to have a negative redox potential (such as -250mV). After treatment, the water that has passed through the oil should optimally have a pH of about 9 and a redox potential of about -100mV to +25mV. Working Example

[0037] The basic procedure for forming the aqueous treatment compositions used in the following examples is as follows: water is adjusted to a preselected pH by adding concentrated potassium hydroxide and concentrated sodium hydroxide, the NaOH / KOH mixture can be a 1:1 mixture or about a 1.1:1 mixture, and then the substances tested as treatment agents (such as hydroquinone, pyrogallol, zinc gluconate, magnesium gluconate, etc.) are added thereto in amounts sufficient to provide the concentrations set forth in the tables in the examples below. Each solution is stirred for 1 hour in a covered vessel with a controlled amount of headspace.

[0038] After the test solution preparation of each above procedure, prepare oil sample, usually 100mL sample. The oil sample used in this paper embodiment comprises mercaptan, such as ethyl mercaptan, butyl mercaptan and pentyl mercaptan. Test reveals that pentyl mercaptan is the easiest to detect and measure. Mass spectrometry proves that after being processed with aqueous treatment composition, the disulfide product of pentyl mercaptan and other possible products (various peaks appear on the chromatogram along with the reduction of pentyl mercaptan peak).

[0039] Each kind of aqueous treatment composition is added in the corresponding oil sample with a certain dosage. In most embodiments, the aqueous treatment composition is added with the amount of 1 volume % (1mL is pipetted into 100mL of oil). The oil with the aqueous treatment composition is stirred for at least one hour, and then the mercaptan is sampled using the standard ASTM UOP 163 potentiometric titration method. The quantitative lower limit of UOP 163 is 0.2 mass-ppm mercaptan (in terms of sulfur) and 1.0 mass-ppm hydrogen sulfide (in terms of sulfur). The dosage can vary, and if the dosage is not 1%, it is specified in the following embodiments. The stirring time can be extended equally, and if greater than one hour, it is also noted in the following embodiments. Example 1

[0040] Obtain crude oil sample, and test in 100ml sample according to different processing possibilities.Each crude oil sample is mixed with the amyl mercaptan of 100ppm, to set up known baseline, for its measurement of the reduction of mercaptan amount.The ppm amyl mercaptan in this embodiment uses the titration method described above to measure.After one hour of incubation (time for chemical reaction is assigned before analyzing sample), the control sample that does not add has the amyl mercaptan of 48ppm.After one hour at room temperature and normal pressure, the control sample that adds has the amyl mercaptan of 233ppm.Allow sample at room temperature and normal pressure in sealed container (such as, fixing with screw cap on reaction vessel), use magnetic stirring plate to stir and react preselected time period with medium speed (such as, 500-1000rpm).Container has limited head space, is about 20% head space in some embodiments. In this way, ambient air may initially contact the oil as it is poured or during addition of the aqueous treatment composition, but because the container is sealed, introduction of air into the oil (a source of oxygen) is limited and evaporation (volatilization) of thiols from the sample is minimized.

[0041] The pH listed in the tables in all examples is the pH of the aqueous treatment composition itself, not the pH of the oil-aqueous treatment composition mixture. Table 1

[0042] Test 5 was repeated two more times for a 12 hour test period. In one of the tests, the ppm of pentanethiol was again below the detection limit, and in the other test it was 9 ppm. Each pH level successfully reduced the ppm of pentanethiol, and the reduction increased as pH increased. As shown in Test 4, pyrogallol (trihydroxybenzene) alone does not oxidize mercaptans.

[0043] Referring to Figure 1, the aqueous treatment composition had NaOH / KOH in concentrations sufficient to define the solution pH (11, 12, 13, and 14, respectively), zinc gluconate concentration of 0.1% wt / wt solution, and 1,4-benzenediol concentration of 0.05% wt / wt. The % removal of mercaptans at each pH is presented in Figure 1. As the pH increases, the percentage removal of mercaptans also increases. Example 2

[0044] Pyrogallol was further explored. A control oil was spiked with 100 ppm pentanethiol and then tested using a standard titration method. Table 2

[0045] As shown in Experiment 4 in Table 1 above, pyrogallol by itself was ineffective in high pH aqueous solutions. As shown in Experiment 12, pyrogallol with zinc gluconate did reduce the concentration of pentanethiol present in the oil sample. The pentanethiol was reduced by 25%. This is much less effective than the hydroquinone experiment in Table 1. However, at the concentrations tested above, pyrogallol stayed in solution better than hydroquinone. We have found that filtering solutions containing hydroquinone is necessary to prevent precipitation.

[0046] In testing post-treatment additions of hydrogen peroxide, a 2% solution was not strong enough. We used a 30% hydrogen peroxide solution in Experiment 11 above. The hydrogen peroxide was not mixed into the treatment composition because it can undergo an undesirable exothermic reaction. Instead, the hydrogen peroxide was added after the aqueous treatment composition had been mixed into the oil for an incubation period as described above. Example 3

[0047] Next a test was performed to test zinc gluconate. A crude oil sample with a background level of 48 ppm of pentanethiol as tested in Example 1 was spiked with 100 ppm of pentanethiol. This is the control set forth in Table 2 below. Table 3

[0048] Each of Trials 14-16 successfully reduced the presence of pentanethiol. Zinc gluconate alone reduced the mercaptan ppm concentration by 68% in one hour and by 74% in two hours. Where hydroquinone was added to the zinc gluconate, the mercaptan was further oxidized, reducing by 86% in two hours and by 89% in 12 hours. Example 4

[0049] Testing Magnesium Gluconate. Magnesium gluconate is considered as a substitute for zinc gluconate; however, the solubility of magnesium gluconate is low. The controls in the table below are virgin crude oil samples that were not spiked. Table 4

[0050] In the above test, the trace amount of hydroquinone was 2 ppm. The aqueous treatment composition alone effectively reduced the mercaptan concentration by 33%. This same treatment composition was then supplemented with 150 ppm of a 30% hydrogen peroxide solution, with no detectable mercaptans.

[0051] Experiment 17 was repeated with a sample spiked with 10 ppm of pentanethiol and subsequently 150 ppm of hydrogen peroxide was added. There was no significant improvement in the reduction of mercaptan concentration. Magnesium gluconate was added to the treatment composition. Table 5

[0052] Even without the addition of hydrogen peroxide, an aqueous treatment composition having both zinc gluconate and magnesium gluconate performed better in reducing mercaptans present in crude oil samples. Numerous tests conducted revealed that magnesium gluconate is suitable in an aqueous treatment composition. And surprisingly, including magnesium gluconate with zinc gluconate increased the reduction of mercaptans in the sample. Calcium lactate, zinc-2-deoxyglucose, zinc acetate, and an organic copper compound (copper citrate) were each tested as possible substitutes for zinc gluconate and magnesium gluconate, but none were successful. The dosage in oil for each substitute for zinc gluconate was 0.0015%; pyrogallol was 0.0007%, and hydroquinone was 0.00001%, the pH of each solution was adjusted to 13, and the reaction time was 1 hour. Example 5

[0053] Next, we increased the amount of pentanethiol added and tested the formulation of Run 20 again. Table 6

[0054] The aqueous treatment composition was effective. It reduced the concentration of spiked pentanethiol by about 86%. Example 6

[0055] Prepare an aqueous treatment composition. Add pyrogallol to a blend of 22% (wt / wt) sodium hydroxide and 20% (wt / wt) potassium hydroxide to a final concentration of 0.1% (wt / wt). Stir the blend until homogeneous. Then, add zinc gluconate to a concentration of 0.5% (wt / wt), followed by magnesium gluconate to a concentration of 0.05% (magnesium gluconate is less water soluble than zinc gluconate, so it is added in lower amounts), followed by a trace amount of hydroquinone (2 ppm).

[0056] Crude oil was treated. An oil containing 32.6 ppm total mercaptans was obtained. The oil was analyzed by titration UOP 163. One liter aliquot (sample 1) of the oil was stirred with 1000 ppm of the aqueous treatment composition. A second one liter aliquot (sample 2) of the oil was stirred with a 500 ppm dose of the aqueous treatment composition. Two samples of the oil were sealed with screw caps before and after the addition of the aqueous treatment composition. The sample was stirred on a stirring plate at 500 rpm for two hours. The sample was removed from the stirring plate thereafter and allowed to stand overnight (12 hours). The container had a headspace of approximately twenty percent; this means that ambient air may initially contact the oil when the oil is poured in or during the addition of the aqueous treatment composition, but since the container is then sealed, no air is continuously introduced into the oil, and evaporation (volatilization) of mercaptans in the sample is minimal.

[0057] After a 12 hour period, both samples were tested by titration according to the UOP 163 method. The crude oil control sample had 32.6 ppm mercaptans (naturally present, ie, not spiked with additional mercaptans). Both samples significantly reduced the amount of mercaptans naturally present in crude oil. Example 7 : Gas chromatography and mass spectrometry

[0058] We used headspace gas chromatography / mass spectrometry (GC / MS) with selected ion monitoring (SIM) to monitor thiols in oil. The extraction was performed using brand DVB / CAR / PDMS (divinylbenzene / Carboxen / polydimethylsiloxane). For quantification, a standard curve was generated using the SPME method over a range of concentrations using pentamethylenethiol standards, where each standard or sample contained a constant concentration of an internal standard. The response of pentamethylenethiol was normalized to that of the internal standard, which is a quality assurance measure.

[0059] In this test, pentanethiol was spiked into oil with <5 ppm naturally occurring pentanethiol. The total measured pentanethiol was quantified as 50 ppm. We have found that oil spiked with mercaptans is more easily oxidized than mercaptans naturally occurring in the oil, probably because mercaptans bind or strongly associate with hydrocarbons in the oil through hydrophobic interactions, van der Waals forces, etc. Table 7

[0060] LOQ stands for "Limit of Quantitation". For the test method used, the LOQ was 1 ppm. Example 8

[0061] Test the post-treatment of adding PEG. According to Test 18, an oil sample containing mercaptan was treated as above with an aqueous treatment composition of 1 volume % (1 mL / 100 mL oil). Then half an hour after adding the above chemical blend, 0.1 volume % of 50 ppm polyethylene glycol was added. Titration using the UOP 163 titration method proved that this treatment process reduced the mercaptan in the oil by 71%. A film of separated water phase was found at the bottom of the oil. 50 ppm of polyethylene glycol acts as a demulsifier that helps to separate the water phase and the oil. The oil was then washed with water (approximately 50% wt / wt water: oil). The total sulfur of the oil phase and the water phase was then detected separately by X-ray diffraction. An additional 20% of the sulfur in the oil was lost into the water wash.

[0062] It should be noted that the embodiments are not limited to the details of the constructions and steps described herein in their application or use. Features of the illustrative embodiments, constructions, and variants may be implemented or incorporated in other embodiments, constructions, variants, and modifications, and may be practiced or performed in various ways. In addition, unless otherwise noted, the terms and expressions used herein are selected for the convenience of the reader to describe the illustrative embodiments of the present invention, and are not intended to limit the purpose of the present invention. In short, it is the applicant's intention that the scope of the patent issued thereby is limited only by the scope of the appended claims.

[0063] The claims are as attached.

Claims

1. A method for treating crude oil or petroleum fractions, the method comprising: Providing crude oil or petroleum fractions in which the content of sulfur compounds needs to be reduced; adding a treatment composition to the crude oil or petroleum fraction, wherein the treatment composition has a pH of 9 or greater and comprises: (a) less than 1% wt / wt of di- or tri-benzohydroxy compounds; (b) strong bases; (c) less than 0.5% wt / wt divalent metal gluconate; and (d) the balance is water; and mixing the treatment composition with crude oil or a petroleum fraction to form a mixture comprising 0.001% to 0.02% wt (a) / wt oil and 0.001% to 0.03% wt (c) / wt oil; wherein (a) oxidizes sulfur compounds in crude oil or petroleum fractions in the presence of (c), thereby reducing the amount of sulfur compounds in the crude oil or petroleum fractions.

2. The method of claim 1, wherein (a) is present at less than 0.2% wt / wt of the treatment composition.

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

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

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

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

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

8. The method of claim 1, wherein the adding and mixing are performed in the presence of oxygen.

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

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

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

12. The method of claim 1, further comprising adding 1000 ppm or less of polyethylene glycol after mixing the treatment composition with the crude oil or petroleum fraction.

13. The method of claim 1 wherein mixing occurs for at least one hour.

14. A composition for treating crude oil and / or petroleum fractions, comprising: (a) less than 1% wt / wt of di- or tri-benzohydroxy compounds; (b) strong bases; (c) less than 1% wt / wt of divalent metal gluconate or metallic zinc powder; and (d) Residual water; wherein the treatment composition has a pH of 9 or greater.

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

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

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

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

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

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

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