Composition Process And Apparatus To Remove Sulfur From Refined Crude Oil Fraction

Abstract

A ionic liquid composition to remove sulfur from refined crude oil fraction, comprising or consisting of two or more compounds having: —an imidazolium cation substituted by one or more straight or branched C.sub.1-C.sub.6 alkyl group and —an anion selected from the group consisting of R.sub.5COO, CI., Br, [BF.sub.4], [PF.sub.6]—, [SbF.sub.6]—, [R.sub.6SO.sub.4], [OTs], [OMs], wherein R5 is C.sub.1-C.sub.8 alkyl, Cs—Cs cycloalkyl, benzyl, C.sub.2-C.sub.6 alkenyl, and R6 is C.sub.1-C.sub.6 alkyl.

Claims

1. An ionic liquid composition to remove sulfur from refined crude oil fraction, comprising two or more compounds having: an imidazolium cation substituted by one or more straight or branched C.sub.1-C.sub.6 alkyl group, and an anion selected from the group consisting of R.sub.5COO.sup.−, Cl.sup.−, Br.sup.−, [BF.sub.4].sup.−, [PF.sub.6].sup.−, [SbF.sub.6].sup.−, [R.sub.6SO.sub.4].sup.−, [OTs].sup.−, [OMs].sup.−, wherein R5 is C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.8 cycloalkyl, benzyl, C.sub.2-C.sub.6 alkenyl, and R6 is C.sub.1-C.sub.6 alkyl.

2. The composition of claim 1, wherein the imidazolium cation is substituted in position 1 and 3 by a straight or branched C.sub.1-C.sub.6 alkyl group, optionally is substituted in position 1 by butyl and in position 3 by methyl.

3. The composition of claim 1, wherein the anion is selected from [BF.sub.4].sup.− and [PF.sub.6].sup.−.

4. The composition of claim 1, wherein the two or more compounds comprise: 1-butyl-3-methyl imidazolium hexafluoro phosphate, and 1-butyl-3-methyl imidazolium tetrafluoroborate.

5. The composition of claim 1, wherein the anion is selected from Cl.sup.−, [BF.sub.4].sup.− and [PF.sub.6].sup.−.

6. The composition of claim 1, comprising: 1-butyl-3-methyl imidazolium hexafluoro phosphate, 1-butyl-3-methyl imidazolium tetrafluoroborate, and 1-butyl-3-methyl imidazolium chloride.

7. The composition of claim 6, comprising: from 30 to 50% by volume of 1-butyl-3-methyl imidazolium hexafluoro phosphate, from 20 to 30% by volume of 1-butyl-3-methyl imidazolium tetrafluoroborate, from 25 to 35% by volume of 1-butyl-3-methyl imidazolium chloride, with respect to the total volume of the composition.

8. The composition of claim 7, comprising: from 35 to 44% by volume of 1-butyl-3-methyl imidazolium hexafluoro phosphate, from 22 to 27% by volume of 1-butyl-3-methyl imidazolium tetrafluoroborate, from 26 to 29% by volume of 1-butyl-3-methyl imidazolium chloride, with respect to the total volume of the composition.

9. The composition of claim 6, wherein the volume ratio between 1-butyl-3-methyl imidazolium hexafluoro phosphate, 1-butyl-3-methyl imidazolium tetrafluoroborate and 1-butyl-3-methyl imidazolium chloride is comprised between 1:0.63:0.74 and 1:0.61:0.66.

10. The composition of claim 1, wherein the composition (i) does not comprise an oxidizing agent; and/or (ii) does not comprise a metal salt.

11. The composition of claim 1, additionally comprising water and/or an organic solvent.

12. A process for desulfurization of a refined crude oil fraction, comprising: mixing a ionic liquid composition according to claim 1 with a batch of refined crude oil fraction in a mixing tank to manufacture an emulsion comprising at least the refined crude oil fraction and the ionic liquid composition; feeding the emulsion through a catalytic reactor to bind at least S-compounds, and optionally other metals, of the refined crude oil fraction to the ionic liquid composition; feeding the emulsion into a settling tank and storing the emulsion in said settling tank for a settling time (t) in order to leave the S-compounds bond to the ionic liquid composition to separate by gravity from a desulfurized refined crude oil fraction and to settle down in the settling tank; wherein, optionally, the desulfurized refined crude oil fraction is then transferred to a storage or service tank; wherein, optionally, the settled ionic liquid composition containing S-compounds is then transferred to a flashing unit.

13. The process of claim 12, wherein, before mixing the ionic liquid composition with the batch of refined crude oil fraction, the ionic liquid composition is mixed with demineralized water and then the mixture of ionic liquid composition and demineralized water is fed to the mixing tank (6) containing or configured to contain the batch of refined crude oil fraction.

14. The process of claim 12, wherein, in the flashing unit, S-compounds are separated from the ionic liquid composition and form a residual sludge in the flashing unit; wherein the ionic liquid composition free of S-compounds is fed to a separate re-use tank to be reused in the process; wherein the residual sludge is transferred to a holding tank and, optionally, dried and packed for further handling.

15. An apparatus for desulfurization of a refined crude oil fraction configured to perform the process of claim 12, wherein the apparatus comprises: a mixing tank having a first inlet in fluid communication with a tank of refined crude oil fraction; a fresh ionic liquid composition tank and/or a re-use ionic liquid composition tank in fluid communication with a second inlet of the mixing tank; at least one settling tank having an inlet in fluid communication with an outlet of the mixing tank; wherein said at least one settling tank has a first upper outlet for delivering desulfurized refined crude oil fraction and a second lower outlet for delivering settled ionic liquid composition containing S-compounds; a catalytic reactor located between the outlet of the mixing tank and the inlet of said at least one settling tank.

Description

DESCRIPTION OF DRAWINGS

[0101] FIG. 1 schematically shows an apparatus for desulfurization of a refined crude oil fraction according to the present invention; and

[0102] FIG. 2 is a flowchart of a process for desulfurization of a refined crude oil fraction according to the present invention.

DETAILED DESCRIPTION

[0103] FIG. 1 schematically shows an apparatus 1 for desulfurization of a refined crude oil fraction according to the present invention.

[0104] Suitable refined crude oil fractions may be selected from gasoline, kerosene, diesel oil, heavy oil, and lubricating oil. In an embodiment, the refined crude oil fraction is heavy fuel oil for maritime transportation.

[0105] The apparatus 1 comprises a mixing tank 2 having a first inlet 2a in fluid communication with a tank 3 of refined crude oil fraction and a second inlet 2b in fluid communication with a fresh ionic liquid composition tank 4 and/or a re-use ionic liquid composition tank 4′. The mixing tank 2 comprises mixing elements, not shown in drawings, configured to blend the liquid content of the mixing tank 2. The mixing tank 2, including flanges and connections, may be assembled of welded mild steel plates, rockwool insulation and galvanized cover plates. The mixing elements of the mixing tank 2 of the disclosed embodiment comprise two macerating pumps, one duty and one stand-by, to ensure satisfactory emulsification. The macerating pumps operates in on/off mode for each batch. Continuously level control, including temperature monitoring, may be displayed locally as well as on a remote control system. The mixing tank 2 is equipped with heating devices 5, such as internal steam heating coils and/or electrical heating elements with temperature control.

[0106] According to the process of the invention, batches of refined crude oil fraction from the tank 3 are processed. For each batch, a predetermine quantity of refined crude oil fraction is transferred to the mixing tank 2. An amount of a mixture comprising a ionic liquid composition (which will be detailed in the present description) and demineralized water calculated as a function of the actual sulfur content within the batch of refined crude oil fraction is transferred from the fresh ionic liquid composition tank 4 and/or from the re-use ionic liquid composition tank 15 into the mixing tank 2. In the mixing tank, the refined crude oil fraction with the mixture comprising the ionic liquid composition and the demineralized water is emulsified to obtain an emulsion comprising: the mixture comprising the ionic liquid composition and demineralized water, and the refined crude oil fraction. The refined crude oil fraction inlet supply should be maintained at approx. 60° C.-80° C. (a pre-heater may be installed if necessary). The refined crude oil fraction with the mixture comprising the ionic liquid composition and the demineralized water is heated to and maintained at a mixing temperature T.sub.mix of 80° C. through the heating devices 5 for a better emulsification.

[0107] The apparatus 1 comprises two settling tanks 6, each having an inlet 6a in fluid communication with an outlet 2c of the mixing tank 2. Each of the settling tanks 6 has a first upper outlet 6b connected to a storage or service tank 7 for refined crude desulfurized oil fraction resulting from the process of the invention and a second lower outlet 6c. The settling tanks 6, including flanges and connections, may be assembled of welded mild steel plates, rockwool insulation and galvanized cover plates. Each settling tank 6 is equipped with internal cone baffle plates 8 to reduce the overall settling time. Each settling tank 6 is provided with level and temperature controls which may be displayed locally as well as on the remote control system. The emulsion is stored in said settling tanks 6 for a settling time t in order to leave the sulfur compounds (S-compounds) bond to the ionic liquid composition to separate by gravity from a desulfurized refined crude oil fraction and to settle down in each settling tank 6. The emulsion in the settling tanks 6 is maintained at a settling temperature T.sub.settl of 50° C. for the cited settling time “t” which may be of 120 minutes.

[0108] A catalytic reactor 9 is located between the outlet 2c of the mixing tank and the inlets 6a of the settling tanks 6. The catalytic reactor 9 comprises duct or ducts, mechanical elements, e.g. blades, movable or fixed, or other mixing devices configured to further mix the emulsion flowing through the catalytic reactor 9 and to increase the rate of chemical reactions in said emulsion. The catalytic reactor 9 allows to improve binding of at least S-compounds, and optionally other metals, of the refined crude oil fraction to the ionic liquid composition. The catalytic process is arranged inline between the mixing tank 2 and settling tanks 6.

[0109] After the settling time “t”, the liquid in each settling tank 6 is divided in two parts: un upper part 10 of desulfurized refined crude oil fraction and a lower part 11 of the sulfur compounds (S-compounds) bond to the ionic liquid composition. A continuously double acting level control system allows monitoring the oil/liquid composition level interface.

[0110] The desulfurized refined crude oil fraction 10 is then transferred to the storage or service tank 7 through the first upper outlets 6b for use when needed. The settled ionic liquid composition containing S-compounds 11 is then transferred to a flashing unit 12 part of the apparatus 1. The flashing unit 12 is configured to separate the S-compounds from the ionic liquid composition. The flashing unit 12 leaves the heavy metals and sulfur as a sludge residue in the bottom part. The flashing unit 12 has an inlet 12a connected to the second lower outlet 6c of each settling tank 6 for receiving the settled ionic liquid composition containing S-compounds 11. The flashing unit 12 has a first upper outlet 12b in fluid communication with an inlet 4′a of the re-use tank 4′, for delivering the ionic liquid composition free of S-compounds to said re-use tank 4′, and a second lower outlet 12c for delivering residual sludge S-compounds to a holding tank 13. The residual sludge S-compounds may be transferred to a separate drying and bagging unit, not shown, for further handling. The ionic liquid composition free of S-compounds fed to the separate re-use tank 4′ may be reused in the process.

[0111] The fresh ionic liquid composition tank 4 has an outlet 4a connected to the second inlet 2b of the mixing tank 2 through a duct. The re-use ionic liquid composition tank 4′ has an outlet 4′b connected to said duct between said outlet 4a and said second inlet 2b. The fresh ionic liquid composition tank 4 has a first inlet 4b connected to a source of demineralized water 14 and a second inlet 4c connected to an outlet 15a of a concentrate ionic liquid composition tank 15. The fresh ionic liquid composition tank 4 is also acting as a mixing tank between concentrated ionic liquids supplied from the concentrate ionic liquid composition tank 15 and demineralized water supplied optionally through a reverse osmosis desalination system.

[0112] According to the process of the invention, before mixing the ionic liquid composition with the batch of refined crude oil fraction, the concentrate ionic liquid composition from the concentrate ionic liquid composition tank 15 is mixed with demineralized water in the fresh ionic liquid composition tank 4 and then the mixture of ionic liquid composition and demineralized water is fed to the mixing tank 2 containing or configured to contain the batch of refined crude oil fraction.

[0113] The apparatus 1 is designed for continuous safe monitored batch operations. Operating pressures within mixing tank 2 and settling tanks 6 are kept at atmospheric pressure and fuel oil temperature is maintained below its flash point High temperatures are only present within the tank steam heating coils 5, as well as, within the flashing tank 12. Partial vacuum may also be applied within the flashing tank 12.

[0114] The ionic liquid composition consists of two or more compounds having: [0115] an imidazolium cation substituted by one or more straight or branched C.sub.1-C.sub.6 alkyl group and [0116] an anion selected from the group consisting of R.sub.5COO.sup.−, Cl.sup.−, Br.sup.−, [BF.sub.4].sup.−, [PF.sub.6].sup.−, [SbF.sub.6].sup.−, [R.sub.6SO.sub.4].sup.−, [OTs].sup.−, [OMs].sup.−, wherein R5 is C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.8 cycloalkyl, benzyl, C.sub.2-C.sub.6 alkenyl, and R6 is C.sub.1-C.sub.6 alkyl.

[0117] In an embodiment, the composition comprises or consists of [0118] 1-butyl-3-methyl imidazolium hexafluoro phosphate, [0119] 1-butyl-3-methyl imidazolium tetrafluoroborate, and [0120] 1-butyl-3-methyl imidazolium chloride.

[0121] In an embodiment, the composition comprises or consists of [0122] from 35 to 44% by volume of 1-butyl-3-methyl imidazolium hexafluoro phosphate, [0123] from 22 to 27% by volume of 1-butyl-3-methyl imidazolium tetrafluoroborate, [0124] from 26 to 29% by volume of 1-butyl-3-methyl imidazolium chloride

[0125] with respect to the total volume of the composition.

[0126] In an embodiment, a volume ratio between 1-butyl-3-methyl imidazolium hexafluoro phosphate, 1-butyl-3-methyl imidazolium tetrafluoroborate and 1-butyl-3-methyl imidazolium chloride is comprised between 1:0.63:0.74 and 1:0.61:0.66.

[0127] In an embodiment, the emulsion comprises: [0128] from 5% to 20% by mass of a mixture comprising the ionic liquid composition according to the first object of the invention and demineralized water, and [0129] from 80% to 95% by mass of a refined crude oil fraction

[0130] with respect to the total mass of the emulsion.

[0131] In an embodiment, the emulsion comprises: [0132] from 5% to 15% by mass of a mixture comprising the ionic liquid composition according to the first object of the invention and demineralized water, and [0133] from 85% to 95% by mass of a refined crude oil fraction

[0134] with respect to the total mass of the emulsion,

[0135] In an embodiment, the above mixture comprises from 1% to 3% by mass of the ionic liquid composition and from 97% to 99% by mass of demineralized water, with respect to the total mass of the mixture.

[0136] In an embodiment, a mass ratio between the oil fraction and the ionic liquid composition is 550:1, more preferably is 450:1.

[0137] The Applicant has found that the S-removal % obtained through the invention may be higher than 70%, optionally higher than 75%, 80% or 85%, optionally higher than 90%.

EXAMPLES

Example 1: Preparation of the Ionic Liquid (IL1) Composition

[0138] A ionic liquid composition according to the present invention was prepared with the following ingredients (all percentage by volume):

[0139] 44% by volume of 1-butyl-3-methyl imidazolium hexafluoro phosphate,

[0140] 27% by volume of 1-butyl-3-methyl imidazolium tetrafluoroborate,

[0141] 29% by volume of 1-butyl-3-methyl imidazolium chloride.

[0142] To prepare 10 liters of a ionic liquid composition according to the present invention 4.4 liters of 1-butyl-3-methyl imidazolium hexafluoro phosphate, 2.7 liters of 1-butyl-3-methyl imidazolium tetrafluoroborate and 2.9 liters of 1-butyl-3-methyl imidazolium chloride were mixed for 2 hours at 25° C.

Example 2: Preparation of the Emulsion of Heavy Oil and IL

[0143] The ionic liquid composition prepared in example 1 was first mixed with demineralized water, then the resultant mixture was added to the heavy oil in a mixing tank.

[0144] Specifically:

[0145] 9.8 liters of demineralized water and define amount of the ionic liquid composition prepared in example 1 (2% by mass with respect to the total mass of the mixture) were mixed;

[0146] 90 liters of marine fuel oil (IFO) and define amount of the mixture prepared above (10% by mass with respect to the total mass of the emulsion) were mixed in the mixing tank to give the title emulsion.

Example 3: Determination of Sulfur Content

[0147] The S-content was determined by X-Ray Fluorescence Spectrometer (XRF) by SGS Italia SPA, Genova, Italia according to the International Standard ISO 8754, second edition 2003.

[0148] Initial sulfur content of the oil (Inlet oil) used to prepare the emulsion of example 2 and sulfur content of the oil recovered after subjecting the emulsion of example 2 to the process according to the invention (Outlet oil) were determined.

[0149] Sulfur content and the S-removal % of each sample are reported in Table 1.

TABLE-US-00001 TABLE 1 S-content S-content S-removal Sample (% m/m) (ppm) (%) Inlet oil 2.23 22300 — Outlel oil 0.030 300 98.66

[0150] As can be seen from the results reported above, the IL1 composition prepared in example 1 when emulsified with a marine fuel oil is able to effectively remove sulfur from such oil.

[0151] As reported by Javadli, R et al. cited above, few of the known technologies are viable and/or efficient for the desulfurization of heavy oil, mainly due to the properties of heavy oil itself, and there are no reports on the extractive desulfurization of heavy oil by ionic liquids.

[0152] Surprisingly, the Applicant has found that IL1 is able to deeply remove sulfur (by more than 98%) from oils having high sulfur content, such as the marine fuel oil used in example 2, whose initial sulfur content is higher than 2% m/m (higher than 20000 ppm), moreover this accomplishment is reached without the addition of any oxidizing agent.

[0153] Furthermore, it is worth noting that IL1 is able to reduce the sulfur content to a very low level, i.e. 0.030% m/m, which complies with the sulfur limit announced by the International Maritime Organization, to be implemented in ship fuel by 2020, i.e. 0.5% m/m.

[0154] Another advantage carried out by IL1 consists in the fact that it can be used in very low quantity with respect to the oil (the oil/IL1 mass ratio in the emulsion of example 2 is 450:1) and is capable of being reused multiple times, until a maximum of 5 times; moreover, the process of extractive desulfurization by IL1 does not require high energy. Thus overall, the costs related to desulfurization of oils having high sulfur content, such as marine fuel oil, are greatly reduced.

[0155] Summarizing, the IL composition according to the present invention, and the process and the apparatus thereof, represent an improvement in the field of desulfurization of refined crude oil fractions, in particular for desulfurization of heavy fuel oil and marine fuel oil as they reduce the amount of pollutants in air, employ the minimum energy during the desulfurisation process, and have a minimal effect on the price of the fuel.