WO2016100688A1

WO2016100688A1 - Calcium carboxylate amended mercury sorbent

Info

Publication number: WO2016100688A1
Application number: PCT/US2015/066416
Authority: WO
Inventors: Thomas GALE; Michael Lucarelli
Original assignee: Novinda Corp
Current assignee: Novinda Corp
Priority date: 2014-12-18
Filing date: 2015-12-17
Publication date: 2016-06-23
Anticipated expiration: 2017-06-18

Abstract

Herein is described a calcium carboxylate treated mercury sorbent material and a means of manufacture. The material can include a metal-sulfide-phyllosilicate particulate that includes about 0.5 wt.% to about 7.5 wt.%, about 1 wt.% to about 5 wt.%, or about 1 wt.% to about 3 wt.% of a calcium carboxylate, wherein the calcium carboxylate decreases a BET surface area of the metal-sulfide phyllosilicate yet increases a mercury capture percentage of the metal-sulfide-phyllosilicate. The material can be manufactured by admixing a calcium carboxylate, a metal salt, and a sulfide salt with a phyllosilicate in the presence of water to form a metal-sulfide-phyllosilicate particulate that includes about 0.5 wt.% to about 7.5 wt.%, about 1 wt.% to about 5 wt.%, or about 1 wt.% to about 3 wt.% of the calcium carboxylate; and then drying the metal-sulfide-phyllosilicate that includes the calcium carboxylate.

Description

CALCIUM CARBOXYLATE AMENDED MERCURY SORBENT

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to US Provisional Patent Application

No. 62/093499, filed 18 December, 2014, the disclosure of which is incorporated herein in its entirety.

FIELD OF THE INVENTION

[0002] The present invention is directed to a mercury sorbent that includes a calcium carboxylate that decreases the surface area of the sorbent while increasing the mercury sorption by the sorbent.

BACKGROUND

[0003] Emissions of from coal-fired and oil-fired power plants are a major environmental concern. In addition to acid gases, the emissions can include unacceptably high levels of toxic elements, including mercury, antimony, arsenic, cadmium, and lead. In the US, emissions from coal fired power plants are tightly regulated, in part because as mercury emissions from these plants are the largest anthropogenic source of mercury in the US. Due to regulatory changes in the United States, emissions from these coal-fired power plants have decreased from about 53 tonnes in 2005 to 27 tonnes in 2010; yet meeting increasingly tighter regulatory requirements requires new, selective mercury sorbents.

[0004] The classic method for sequestering mercury from flue gas is the injection of powdered activated carbon (PAC) or modified-PAC into the flue stream. The carbon material provides a high surface area for chemisorption of mercury gases and agglomeration of particle bound mercury. One disadvantage of adding PAC into the flue gas is the retention of the material in the fly-ash-waste stream. Fly ash from coal-fired power plants if often added to concrete, where the presence of the activated carbon adversely affects the performance. Other disadvantages of PAC are a low shelf-life (as a non-selective chemisorbant PAC adsorbs deactivating materials from the air and often needs to be reactivated prior to use) and high C0₂ emissions during production.

[0005] Inorganic based methods for sequestering mercury often rely on the formation of a mercuric sulfide, an isolatable form of mercury with significantly lower environmental toxicity than other mercuric salts. The mercuric sulfides can be formed, for example, from elemental sulfur, inorganic and organic polysulfides, inorganic sulfides, or organic thioketones (e.g., thioamides, lawesson's reagent) and the reduced or oxidized form of mercury.

[0006] U.S. Pat. Nos. 6,719,828; 7,048,781 , RE44.124; 7,704,920; 8,480,791 ; and

8,8685,351 teach mercury-reactive, metal sulfides carried on inorganic supports. Despite these materials, there is still an ongoing need for advanced mercury sorbent materials applicable both in the flue gas environment and post-sorption in fly-ash-waste streams. A number of

improvements are desirable including sorption of both reduced and oxidized mercury, stability of the collected mercury form for prolonged environmental sequestration, enhanced sorption reaction rates, greater potential-mercury loading, and supply chain compatibility. Accordingly, there is an ongoing need to improve pollution control sorbents, methods of their manufacture, and methods of their use.

SUMMARY

[0007] A first embodiment is a material that includes a metal-sulfide-phyllosilicate particulate that includes about 0.5 wt.% to about 7.5 wt.%, about 1 wt.% to about 5 wt.%, or about 1 wt.% to about 3 wt.% of a calcium carboxylate, wherein the calcium carboxylate decreases a BET surface area of the metal-sulfide phyllosilicate and wherein the calcium carboxylate increases a mercury capture percentage of the metal-sulfide-phyllosilicate.

[0008] A second embodiment is a process of manufacturing the metal-sulfide- phyllosilicate that includes the calcium carboxylate. The process can include admixing a calcium carboxylate, a metal salt, and a sulfide salt with a phyllosilicate in the presence of water to form a metal-sulfide-phyllosilicate particulate that includes about 0.5 wt.% to about 7.5 wt.%, about 1 wt.% to about 5 wt.%, or about 1 wt.% to about 3 wt.% of the calcium carboxylate; and then drying the metal-sulfide-phyllosilicate that includes the calcium carboxylate; wherein the calcium carboxylate decreases a BET surface area of the metal-sulfide phyllosilicate; and wherein an inclusion of the calcium carboxylate increases a mercury capture percentage of the metal- sulfide-phyllosilicate.

DETAILED DESCRIPTION

[0009] Herein are described compositions, methods of their manufacture, and methods of their use where the compositions include a particulate amended with a material that decreases the BET surface area of the particulate yet, unexpectedly, increases the reactivity of the particulate toward gas-born agents. More specifically, the amended particulate has a decreased BET surface area yet an increased reactivity toward mercury in flue gas.

[0010] In a first embodiment, the composition includes a metal-sulfide-silicate particulate and about 0.1 wt.% to about 10 wt.%, about 0.5 wt.% to about 7.5 wt.%, about 1 wt.% to about 5 wt.%, or about 1 wt.% to about 3 wt.% of a calcium carboxylate. Herein, the calcium carboxylate decreases the BET surface area of the metal-sulfide-silicate yet the inclusion of the calcium carboxylate unexpectedly increases the mercury capture percentage of the metal-sulfide- silicate. In one example, the composition consists of the metal-sulfide-silicate which includes the calcium carboxylate. Herein, the metal-sulfide-silicate can include, carry or incorporate the calcium carboxylate; as will be made clear in the discussion on manufacturing, the calcium carboxylate is blended or sheared into the composition.

[0011] The metal-sulfide-silicate can include a copper sulfide, an iron sulfide, a zinc sulfide, a tin sulfide or a mixture thereof. In one example, the metal-sulfide-silicate can include a metal selected from the group consisting of copper, iron, zinc, tin, and a mixture thereof. In one preferable instance, the metal is selected from copper, iron, and a mixture thereof. In another instance, the metal is copper; in still another instance, the metal is iron; and in yet another instance, the metal is a mixture of copper and iron. While the metal sulfide can be written in the formula MS_X the ratio of sulfide to metal can be variable throughout the metal-sulfide-silicate and often does not represent the crystallinity of material in local environments. For example, the binary metal sulfides can exist as crystalline polymorphs, mixtures of stable and metastable sulfides, and/or amorphous materials. In one example, the binary copper sulfide can exist as a villamaninite, covellite, yarrowite, spionkopite, geerite, anilite, digenite, djurleite, chalcocite, or a mixture thereof. In another example, the metal sulfide can include monosulfides (S^2"), disulfides (S₂ ^2"), or mixtures thereof. In a particularly preferable example, the metal sulfide has a mixture of mono- and di-sulfides.

[0012] The silicate can be selected from the group consisting of phyllosilicates (e.g., bentonite, montmorillonite, hectorite, beidellite, saponite, nontronite, volkonskoite, sauconite, stevensite, and/or a synthetic smectite derivative, particularly fluorohectorite and laponite); mixed layered clay (e.g., rectonite and their synthetic derivatives); vermiculite, illite, micaceous minerals, and their synthetic derivatives; layered hydrated crystalline polysilicates (e.g., makatite, kanemite, octasilicate (illierite), magadiite and/or kenyaite); attapulgite, palygorskite, sepoilite; allophane, quartz, and mixtures thereof. The silicate can further be selected from the above admixed, alloyed, or fused with aluminates, transition metal oxides, and carbon. The silicate can still further be selected from precipitated or fumed silica. Some examples of silicates include bentonite, montmorillonite, fly ash (an aluminosilicate produced by the combustion of fossil fuels, e.g., coal), zeolites, and used solid state catalysts. Even more preferably, the silicate is a bentonite, montmorillonite, or fly ash. Still more preferably, the silicate includes a calcium phyllosilicate.

[0013] Herein, the calcium carboxylate can have the formula

Ca(0₂CC_xH_2x+i)(0₂CC_yH₂y+i) where the x variable can be integer from 4 to 28 and y variable can be an integer from 4 to 28. In a preferable example, the x and y integers are equal, that is x=y. In another example, the x and y a different integers, that is x≠y. The x and y integers can, individually, have values from 5 to 17; 7 to 17; 1 1 to 17; or 15 to 17. In one example, the x and y integers, individually, can be 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, or 17. Notably, the carboxylates can also be understood by their common names or lUPAC names. For example, laurate/dodecanoate (11); myrsitate/tetradecanoate (13); palmitate/hexadecanoate (15); and stearate/octadecanoate (17). Notably, as provided herein the integers x and y do not include the total carbon count in the carboxylate thereby the values of the integers do not directly match the carbon content for, for example, stearate. One particularly preferred example of a calcium carboxylate is calcium stearate.

[0014] In another example, the calcium carboxylate can include a carboxylate of an unsaturated fatty acid (unsaturated carboxylate). That is, one or both of the carboxylates of the calcium carboxylate can unsaturated. Examples of unsaturated fatty carboxylates include, for example, oleate (from oleic acid), linoleate (from linoleic acid), and linolenate (from linolenic acid). The unsaturated carboxylate can have a lipid number of 5-28: 1-6; as used herein, lipid numbers (C:D) are a designation of the number of carbon atoms and double bonds, where the first number C is carbon atoms and the second D is double bonds. For example the unsaturated carboxylate can have a lipid number C value of 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, or 26 and a D value of 1 , 2, 3, 4, 5, or 6. Preferable examples include, but are not limited to, 14: 1 , 16: 1 , 18:1 , 18:2, 18:3, 20: 1 , 20:2, 20:3, 20:4, and 22:1.

[0015] Unexpectedly, the inclusion of the calcium carboxylate improved the mercury capture when compared to the base metal-sulfide-phyllosilicate and/or a metal-sulfide- phyllosilicate which includes a different (alkali metal/alkaline earth/transition metal) carboxylate). In one instance, the mercury capture percentage of the metal-sulfide-phyllosilicate particulate that includes the calcium carboxylate is at least about 5, about 10, about 15, or about 20 percentage points greater than a mercury capture percentage of a metal-sulfide-phyllosilicate particulate that does not include the calcium carboxylate. In another instance, the mercury capture percentage of the metal-sulfide-phyllosilicate particulate that includes the calcium carboxylate is at least about 10, about 15, or about 20 percentage points greater than a mercury capture percentage of a metal-sulfide-phyllosilicate particulate that includes a magnesium carboxylate and/or a zinc carboxylate.

[0016] In one example, the inclusion of the calcium carboxylate (e.g., calcium stearate) decreased the BET surface area by at least about 5%, 10%, 15%, or 20% while the mercury capture percentage increased by at least about 5%, 10%, 15%, or 20% (compared to the carboxylate free metal-sulfide-phyllosilicate). In one direct comparison, the inclusion of about 2 wt.% calcium stearate decreased the BET surface area by at least 10% while increasing the mercury capture percentage by at least 5% (compared to the carboxylate free metal-sulfide- phyllosilicate). When compared to a metal-sulfide-phyllosilicate that includes a magnesium or zinc stearate, the inclusion of 2 wt.% calcium stearate did not appreciably change the BET surface area while increased the mercury capture percentage by at least 20%, 35%, 50%, 75%, 100% (doubling the mercury capture percentage), 150%, or 200%.

[0017] In another embodiment, the above described calcium carboxylate-metal-sulfide- phyllosilicate can be prepared by admixing a calcium carboxylate, a metal salt, and a sulfide salt with a phyllosilicate in the presence of water to form the metal-sulfide-phyllosilicate particulate that includes about 0.1 wt.% to about 10 wt.%, about 0.5 wt.% to about 7.5 wt.%, about 1 wt.% to about 5 wt.%, or about 1 wt.% to about 3 wt.% of the calcium carboxylate. The product of the admixing is then, preferably, dried to yield the above described metal-sulfide-phyllosilicate that includes the calcium carboxylate.

[0018] In one instance, the calcium carboxylate is admixed with the phyllosilicate before either of the metal salt or the sulfide salt. In another instance, the calcium carboxylate, the metal salt, and the sulfide salt are contemporaneously mixed with the phyllosilicate. In still another instance, the calcium carboxylate is admixed with the phyllosilicate after the metal salt and/or the sulfide salt.

[0019] In one particular example, the product can be prepared by admixing a calcium stearate, a copper salt, a sulfide salt, and a phyllosilicate (e.g., bentonite, kaolinite) in the presence of water to form a (calcium stearate)-copper-sulfide-phyllosilicate.

Claims

WHAT IS CLAIMED:

1. A material comprising:

a metal-sulfide-phyllosilicate particulate that includes about 0.5 wt.% to about 7.5 wt.%, about 1 wt.% to about 5 wt.%, or about 1 wt.% to about 3 wt.% of a calcium carboxylate;

wherein the calcium carboxylate decreases a BET surface area of the metal- sulfide phyllosilicate; and

wherein an inclusion of the calcium carboxylate increases a mercury capture percentage of the metal-sulfide-phyllosilicate.

2. The material of claim 1 , wherein the material consists of the metal-sulfide- phyllosilicate that includes the calcium carboxylate.

3. The material of claim 2, wherein the metal-sulfide-phyllosilicate includes a metal selected from the group consisting of copper, iron, zinc, tin, and a mixture thereof.

4. The material of claim 1 , wherein the metal-sulfide-phyllosilicate includes a calcium phyllosilicate.

5. The material of claim 1 , wherein the calcium carboxylate has the formula

Ca(0₂CC_xH_2x+i)(0₂CC_yH_2y+i) where x is an integer from 4 to 28, and y is an integer from 4 to 28.

6. The material of claim 5, wherein x=y.

7. The material of claim 5, wherein x≠y.

8. The material of claim 5, wherein x is an integer from 5 to 17; 7 to 17; 11 to 17; or 15 to 17.

9. The material of claim 5, wherein y is an integer from 5 to 17; 7 to 17; 11 to 17; or 15 to 17.

10. The material of claim 1 , wherein the calcium carboxylate includes an unsaturated fatty acid.

11. The material of claim 1 , wherein the mercury capture percentage of the metal- sulfide-phyllosilicate particulate that includes the calcium carboxylate is at least about 5, about 10, about 15, or about 20 percentage points greater than a mercury capture percentage of a metal-sulfide-phyllosilicate particulate that does not include the calcium carboxylate.

12. The material of claim 11 , wherein the mercury capture percentage of the metal- sulfide-phyllosilicate particulate that includes the calcium carboxylate is at least about 10, about 15, or about 20 percentage points greater than a mercury capture percentage of a metal-sulfide- phyllosilicate particulate that includes a magnesium carboxylate and/or a zinc carboxylate.

13. A process comprising:

admixing a calcium carboxylate, a metal salt, and a sulfide salt with a phyllosilicate in the presence of water to form a metal-sulfide-phyllosilicate particulate that includes about 0.5 wt.% to about 7.5 wt.%, about 1 wt.% to about 5 wt.%, or about 1 wt.% to about 3 wt.% of the calcium carboxylate; and then

drying the metal-sulfide-phyllosilicate that includes the calcium carboxylate; wherein the calcium carboxylate decreases a BET surface area of the metal- sulfide phyllosilicate; and wherein an inclusion of the calcium carboxylate increases a mercury capture percentage of the metal-sulfide-phyllosilicate.

14. The process of claim 13, wherein the calcium carboxylate is admixed with the phyllosilicate before either of the metal salt or the sulfide salt.

15. The process of claim 13, wherein the calcium carboxylate, the metal salt, and the sulfide salt are contemporaneously mixed with the phyllosilicate.

16. The process of claim 13, wherein the calcium carboxylate is admixed with the phyllosilicate after the metal salt and/or the sulfide salt.

17. The process of claim 13, wherein the calcium carboxylate has the formula Ca(0₂CC_xH_2x+i)(0₂CC_yH₂y+i) where x is an integer from 4 to 28, and y is an integer from 4 to 28.