Method for removing mercury in hydrocarbon oil

Abstract

The present invention provides a method which can efficiently adsorb and remove ionic mercury and/or organic mercury contained in a hydrocarbon oil for a long period of time. The method involves bringing the hydrocarbon oil into contact with an adsorbent containing a layered silicate mineral having an interlayer charge of 0 or an interlayer charge of greater than 0 to 0.6 or less.

Claims

1. A method for adsorbing and removing ionic mercury and/or organic mercury in a hydrocarbon oil, comprising bringing the hydrocarbon oil into contact with an adsorbent comprising a layered silicate mineral having an interlayer charge of 0 or an interlayer charge of greater than 0 to 0.6 or less and an optional binder, wherein the adsorbent contains substantially no copper, and wherein the adsorbing is performed by the adsorption action of only the layered silicate mineral.

2. The method according to claim 1, wherein said layered silicate mineral having an interlayer charge of 0 is lizardite, amesite, chrysotile, kaolinite, dickite, halloysite, talc or pyrophyllite.

3. The method according to claim 1, wherein said layered silicate mineral having an interlayer charge of greater than 0 to 0.6 or less is smectite, saponite, hectorite, montmorillonite or beidellite.

4. The method according to claim 1, wherein the method is performed in the absence of hydrogen.

5. A method for adsorbing and removing ionic mercury and/or organic mercury in hydrocarbon oil, comprising bringing the hydrocarbon oil into contact with an adsorbent comprising a layered silicate mineral having an interlayer charge of 0 or an interlayer charge of greater than 0 to 0.6 or less and an optional binder, and an adsorbent containing an activated carbon and/or a metal sulfide, wherein the adsorbent comprising the layered silicate mineral contains substantially no copper, and wherein the adsorbing is performed by the adsorption action of only the layered silicate mineral.

6. The method according to claim 5, wherein said layered silicate mineral having an interlayer charge of 0 is lizardite, amesite, chrysotile, kaolinite, dickite, halloysite, talc or pyrophyllite.

7. The method according to claim 5, wherein said layered silicate mineral having an interlayer charge of greater than 0 to 0.6 or less is smectite, saponite, hectorite, montmorillonite or beidellite.

8. The method according to claim 5, wherein the method is performed in the absence of hydrogen.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a view showing the structure of a layered silicate mineral

(2) FIG. 2 is a view showing the balance of charges in a layered silicate mineral (2:1 layer structure)

DESCRIPTION OF EMBODIMENTS

(3) Hereinafter, the present invention will be described in more detail.

(4) No particular limitation is imposed on the hydrocarbon oil to be treated by the present invention if it is an ionic mercury and/or organic mercury-containing hydrocarbon oil which is liquid in normal conditions. Examples of the hydrocarbon oil include liquid hydrocarbons derived from natural gas or petroleum associated gas and hydrocarbon oils such as hydrocarbons with 5 carbon atoms and fractions with a boiling point of 180° C. or lower resulting from fractional distillation of natural gas or petroleum associated gas or crude oil in an atmospheric distillation unit. The removal method of the present invention can be applied to even natural gas and hydrocarbons such as ethylene and propylene, which are gaseous at ambient temperatures and pressures, in a liquefied state if they can be liquefied by applying thereto pressure.

(5) The mercury in such hydrocarbon oils is contained as elemental mercury, ionic mercury compounds, organic mercury compounds and may be contained in an amount of usually a few ppb by weight to 500 ppb by weight depending on the type of hydrocarbon oil. The method of the present invention can efficiently adsorb and remove ionic mercury and/or organic mercury for a long period of time.

(6) In the present invention, elemental mercury refers to mercury element and is the only metallic element that does not coagulate at ordinary temperatures and pressures. In the present invention, the ionic mercury

(7) refers to mercury that dissociates in the form of mercury ion (Hg.sub.2.sup.2+, Hg.sup.2+) in water, and mercurous chloride (Hg.sub.2Cl.sub.2) and mercuric chloride (HgCl.sub.2) are well-known.

(8) In the present invention, the organic mercury refers to a mercury compound wherein an alkyl group and mercury bonds, and dimethyl mercury, diethyl mercury and the like exist. On the basis of Water Quality Pollution Control Act or environmental criterion, monoalkylmercury halides such as methylmercury chloride, methylmercury bromide and the like are dissolved in water and dissociated as monovalent ions but are treated as organic mercury in the present invention.

(9) In the present invention, the layered silicate mineral refers to a silicate mineral which comprises a tetrahedral structure wherein silicon, aluminum or magnesium is centrally located and oxygens surround therearound to form a tetrahedron and an octahedral structure wherein aluminum, magnesium or iron is centrally located and oxygens surround therearound to form an octahedron as a basic structure and may be of a 1:1 layer structure formed by one tetrahedron and one octahedron or a 2:1 layer structure formed by two tetrahedrons and one octahedron. The both structures are laminates of tetrahedron sheets and octahedron sheets each forming a two dimensional layer (see FIG. 1).

(10) With regard to the interlayer charge in a layered silicate mineral, each silicate layer is repeated as indicated by (basal oxygen).sup.−-(Si).sup.+-(apex oxygen).sup.−-(octahedral cations).sup.+-(apex oxygen).sup.−-(Si).sup.+-(basal oxygen).sup.−, and for the 2:1 structure, when the atom located centrally in the tetrahedral structure is Si.sup.4+ and the atom located centrally in the octahedral structure is Al.sup.3+, the sum of charge in the 2:1 structure is 0. In this case, the charge in the structure is deemed balanced and thus no charge is generated between the layers. However, in the tetrahedral structure, Si.sup.4+ undergoes isomorphous replacement with Al.sup.3+ while in the octahedral structure, Al.sup.3+ undergoes isomorphous replacement with Mg.sup.2+ or Fe.sup.2+, and thus the charge balance is destroyed. As the result, since the charge of cation is decreased, the whole 2:1 structure becomes negatively charged, and this negative charge generates as the interlayer charge. In the actual minerals, the charge is balanced by capturing cations in an amount matching the layer charge between the layers (see FIG. 2).

(11) The interlayer charge indicating 0 means that the charge in a unit structure is balanced as described above. For the 1:1 structure, the charge is balanced in all the layers and thus the interlayer charge is 0. Typical examples of such silicate minerals include lizardite, amesite and chrysotile belonging to the serpentine group and kaolinite, dickite and halloysite belonging to the kaolin group. Talc and pyrophyllite exist as silicate minerals with a 2:1 structure.

(12) The interlayer charge of greater than 0 and 0.6 or less means that 0.6 or fewer Si.sup.4+ in the tetrahedron and 0.6 or fewer Al.sup.+3 in the octahedron in the structure are replaced with Al.sup.3+ and Mg.sup.2+ or Fe.sup.2+, respectively. Typical examples of such minerals include those belonging to the smectite group such as smectite, saponite, hectorite, montmorillonite and beidellite.

(13) The interlayer charge of greater than 0.6 means that more than 0.6 Si.sup.4+ in the tetrahedron and more than 0.6 Al.sup.+3 in the octahedron in the structure are replaced with Al.sup.3+ and Mg.sup.2+ or Fe.sup.2+, respectively. Typical examples of such minerals include those having an interlayer charge of 0.6 to 1.0 belonging to the isinglass (also referred to as “mica”) group such as phlogopite, biotite, muscovite, paragonite and illite and those having an interlayer charge of 1.8 to 2.0 belonging to the brittle mica group such as clintonite and margarite.

(14) In the present invention, the use of an adsorbent containing a layered silicate mineral having an interlayer charge of 0 or an interlayer charge of greater than 0 and 0.6 or less can stably and efficiently remove from a hydrocarbon oil containing ionic mercury and/or organic mercury the ionic mercury and organic mercury for a long period of time.

(15) The necessary amount of the adsorbent can be arbitrarily determined depending on the intended outlet mercury concentration and the type of adsorbent to be used, but when the mercury concentration in a hydrocarbon oil is 100 μg/kg, 1 kg of the adsorbent can remove 0.1 to 10 g of organic mercury and ionic mercury.

(16) In the present invention, the above-described layered silicate mineral may be used in the original powdery form but may be used after being shaped into a pelletized, crushed or particulate form. More specifically, the layered silicate mineral or powder containing the layered silicate mineral as they are or as mixture with a binder such as alumina or silica may be used after being shaped by tablet compression, tumbling granulation or extrusion molding.

(17) Furthermore, in the present invention, any product containing the above-described layered silicate mineral can be used. More specifically, naturally-produced white clay and some activated earth produced by acid-treating white clay may also be used.

(18) Although various method may be applied to bring a hydrocarbon oil into contact with the adsorbent, a fixed bed mode is suitably used because an adsorbing treating apparatus is simple in structure and is easily operable. The fixed bed mode is a mode where an adsorbing treatment is carried out by supplying continuously a hydrocarbon oil into a packed bed configured by filling and fixing the adsorbent in a cylindrical structure.

(19) In the present invention, the above-described adsorbent containing a layered silicate mineral having an interlayer charge of 0 or an interlayer charge of greater than 0 and 0.6 or less in combination with an adsorbent capable of removing elemental mercury can remove not only ionic mercury and/or organic mercury but also elemental mercury from a hydrocarbon oil.

(20) The adsorbent capable of removing elemental mercury may be a conventional adsorbent, such as activated carbon (activated carbon having been subjected to a treatment suitable for adsorbing mercury), metal sulfides (those supporting a sulfurized metal on alumina).

(21) This adsorbent capable of removing elemental mercury may be disposed the prior stage and/or subsequent stage where the adsorbent containing the layered silicate mineral of the present invention or may be used as a mixture therewith.

(22) The method of the present invention can remove mercury down to a trace concentration or extremely low concentration for a hydrocarbon oil containing mercury in a large amount or a minute amount.

(23) The above description illustrates merely an example of the embodiments of the present invention and thus can be modified in accordance with the description of claims.

EXAMPLES

(24) Hereinafter, the present invention will be described in more detail by way of the following examples, which should not be construed as limiting the scope of the invention.

(25) In the examples and comparative examples, the mercury content was measured using a general purpose full automatic mercury analyzer “Mercury/SP-3D” manufactured by Nippon Instruments Corporation, the mercury compounds were analyzed by type in accordance with the method described in ITAS ((International Trace Analysis Symposium '90 (Jul. 23-27, 1990) conference minutes 3P-40 (Akio FURUTA, et al.)).

(26) The hydrocarbon oils containing mercury used in the examples and comparative examples were prepared in the following manners.

(27) (Preparation of Hydrocarbon Oil Containing Elemental Mercury)

(28) Into a 100 ml screw cap bottle with a stirrer therein was put one grain of elemental mercury, followed by addition of normal hexane having been subjected to bubbling with 100 ml argon gas. The gaseous phase portion was then substituted with argon gas, and the mouth of the bottle was covered with a polytetrafluoroethylene sheet and capped. Thereafter, stirring was carried out with a magnetic stirrer for five days. The mercury concentration in the hexane at that time was from 500 to 1500 μg/L. This hexane solution was diluted with hexane in the amount of 5 times more of the solution and used as an elemental mercury-containing hydrocarbon oil in the examples and comparative example. The mercury concentration in the hexane solution after being diluted was 140 μg/L.

(29) (Preparation of Hydrocarbon Oil Containing Organic Mercury and Ionic Mercury)

(30) Pagerungan condensate (mercury content: 66 μg/L) imported from East Timor was filtered with a 10 μm membrane filter, referring to the method described in ITAS (International Trace Analysis Symposium '90 (Jul. 23-27, 1990) conference minutes 3P-40 (Akio FURUTA, et al.)) and then stripped with helium gas to remove elemental mercury thereby preparing a hydrocarbon oil containing organic mercury and ionic mercury. Specifically, 1000 ml of Pagerungan condensate were filtered with a 10 μm membrane filter and then bubbled, injecting helium gas at 100 ml/min in a two-necked flask equipped with a coiled condenser at a temperature of 40° C. for 1.5 hour. After this treatment, the mercury concentration in the hydrocarbon oil was 45 μg/L (organic mercury: 33 μg/L, ionic mercury: 12 μg/L).

Example 1

(31) The hydrocarbon oil containing organic mercury and ionic mercury thus prepared in an amount of 50 ml was put into a 50 ml screw cap bottle containing therein a stirrer, and 0.005 g pulverized kaolinite that is a layered silicate mineral was added thereto. The mixture was allowed to stand, stirring for 140 hours. After 140 hours, the hydrocarbon oil was taken out to measure the content of organic mercury and ionic mercury contained therein.

(32) The same procedures were carried out for the hydrocarbon oil containing elemental mercury thus prepared.

Example 2

(33) The same procedures as Example 1 were followed except for changing the layered silicate mineral to talc.

Example 3

(34) The same procedures as Example 1 were followed except for changing the layered silicate mineral to smectite.

Example 4

(35) The same procedures as Example 1 were followed except for changing the layered silicate mineral to montmorillonite.

Comparative Example 1

(36) The same procedures as Example 1 were followed except for changing the layered silicate mineral to isinglass.

Comparative Example 2

(37) The same procedures as Example 1 were followed except for changing the layered silicate mineral to illite.

Comparative Example 3

(38) The same procedures as Example 1 were followed except for using 0.05 g of a commercially available coconut husk active carbon instead of 0.005 g of the layered silicate mineral.

Comparative Example 4

(39) The same procedures as Example 1 were followed except for using 0.05 g of a copper sulfide+alumina-based adsorbent instead of 0.005 g of the layered silicate mineral.

Evaluation

(40) Table 1 sets forth the adsorption capacity in respect of organic mercury and ionic mercury in Examples 1 to 4 and Comparative Examples 1 to 4. The adsorption capacity for organic mercury and ionic mercury exceeds 350 μg/g when using the layered silicate minerals having no interlayer charge or an interlayer charge of greater than 0 and 0.6 or less of Examples 1 to 4 while the adsorption capacity was 20 μg/g or less, which is extremely small when using the layered silicate mineral having an interlayer charge of greater than 0.6 of Comparative Examples 1 and 2. Similarly to Comparative Examples 1 and 2, the adsorption capacity for organic mercury and ionic mercury was also small in Comparative Examples 3 and 4 using conventional commercially available coconut husk active carbon and metal sulfide (copper sulfide+alumina) having been used for removal of mercury.

(41) TABLE-US-00001 TABLE 1 Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 1 Example 2 Example 3 Example 4 Adsorbing material kaolinite talc smectite montmorillonite mica illite coconut husk copper active carbon sulfide + (commercially alumina available) Layer structure 1:1 layer 2:1 layer 2:1 layer 2:1 layer 2:1 layer 2:1 layer structure structure structure structure structure structure Interlayer charge none none 0.2 to 0.6 0.2 to 0.6 0.6 to 1.0 0.6 to 1.0 (charge = 0) (charge = 0) Elemental mercury 140 140 140 140 140 140 140 140 concentration in hydrocarbon oil (μg/L) (before adsorption) Elemental mercury — 109 — 101 — — 0.4 0.5 concentration in hydrocarbon oil (μg/L) (after adsorption) Adsorbed elemental mercury — 31 — 39 — — 140 140 amount (μg/L) Ionic mercury + organic 45 45 45 45 45 45 45 45 mercury concentration (μg/L) in hydrocarbon oil (before adsorption) Ionic mercury + organic 2 3.3 5.3 8.2 43 44.6 10 8 mercury concentration (μg/L) in hydrocarbon oil (after adsorption) Adsorption capacity for ionic 430 417 397 368 20 4 35 37 mercury and organic mercury (mercury-μg/adsorbent-g)

INDUSTRIAL APPLICABILITY

(42) The method of the present invention is extremely useful for industrial purposes because it adsorbs and removes ionic mercury and/or organic mercury contained in a hydrocarbon oil efficiently for a long period of time.