Composition and process for removing chlorides from a gaseous stream

Abstract

A composition capable of removing chlorides from a gaseous stream and a process of using same. The compositions have sufficient chloride capacity, offer comparable creation of green oil, and have sufficient structural integrity to be utilized as sorbents in a chloride removal process. Generally, the compositions include a first zinc carbonate, a second zinc carbonate different than the first zinc carbonate and an alumina material. The composition has been cured at a temperature between about 149 to 399 C. The first zinc carbonate may comprise hydrozincite and the second zinc carbonate may comprise smithsonite.

Claims

1. A composition comprising: a first zinc carbonate; a second zinc carbonate different than the first zinc carbonate; sodium carbonate; an alumina material, wherein the alumina material comprises less than 10 wt % of the composition, and wherein the first zinc carbonate comprises hydrozincite, wherein a molar ratio of sodium to zinc is between 0.95 to 1.10, wherein a molar ratio of sodium to alumina is at least 5, and wherein the composition has been cured at a temperature between 149 to 316 C.

2. The composition of claim 1 wherein the second zinc carbonate comprises smithsonite.

3. The composition of claim 1 wherein the alumina material comprises less than 5 wt % of the composition.

4. The composition of claim 1 wherein the composition includes at least two pairs of x-ray diffraction peaks at a two-theta value selected from a group consisting of: about 12.80 and about 17.30; about 13.00 and about 36.00; and, about 25.00 and about 32.50.

5. The composition of claim 4, wherein the composition further includes at least one x-ray diffraction peak or pair of peaks at a two-theta value selected from a group consisting of: about 34.30; about 35.00 and 38.00; and, about 30.50 and about 34.50.

6. The composition of claim 1 wherein the composition lacks an x-ray diffraction peak at a two-theta value of about 14.50.

7. The composition of claim 1 further comprising: zinc oxide.

8. The composition of claim 7 further comprising: about 16 wt % sodium.

9. The composition of claim 1 further comprising: about 42 wt % zinc.

10. The composition of claim 1, wherein the molar ratio of sodium to alumina is between 5 to 6.

11. A composition for adsorbing chloride compounds, the composition comprising: a first zinc carbonate, wherein the first zinc carbonate comprises hydrozincite or smithsonite; a second zinc carbonate different than the first zinc carbonate; sodium carbonate; an alumina material; and, zinc oxide, and wherein a molar ratio of sodium to alumina is between 5.0 to 6.0, wherein a molar ratio of sodium to zinc is between 0.95 to 1.10, wherein the composition has been cured at a temperature between 149 to 316 C., and wherein the alumina material comprises less than 10 wt % of the composition.

12. The composition of claim 11 wherein the composition includes at least two pairs of x-ray diffraction peaks at a two-theta value selected from a group consisting of: about 12.80 and about 17.30; about 13.00 and about 36.00; and, about 25.00 and about 32.50.

13. The composition of claim 11 wherein the first zinc carbonate comprises hydrozincite, and wherein the second zinc carbonate comprises smithsonite.

14. The composition of claim 13, wherein the composition has been cured at a temperature between 260 to 316 C.

15. The composition of claim 11 wherein the composition comprises about 42 wt % zinc and about 16 wt % sodium.

16. The composition of claim 11 wherein the composition is substantially free of boehmite.

17. A process for removing chloride compounds from a gaseous stream, the process comprising: passing a gaseous stream to an adsorption zone, the adsorption zone comprising an adsorbent and being operated under conditions to remove chloride compounds from the gaseous stream, wherein the adsorbent comprises a first zinc carbonate being hydrozincite or smithsonite, a second zinc carbonate different than the first zinc carbonate, sodium carbonate, an alumina material, wherein the alumina material comprises less than 10 wt % of the adsorbent and, zinc oxide, wherein a molar ratio of sodium to alumina is at least 5.0, wherein a molar ratio of sodium to zinc is between 0.95 to 1.10, and wherein the composition has been cured at a temperature between 149 to 316 C.

18. The process of claim 17 wherein the adsorbent comprises about 42 wt % zinc.

19. The process of claim 18 wherein the first zinc carbonate comprises smithsonite, and wherein the second zinc carbonate comprises hydrozincite, and wherein the adsorbent is substantially free of boehmite.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) One or more exemplary embodiments of the present invention will be described below in conjunction with the following drawing figures, in which:

(2) FIG. 1 shows a comparison of an x-ray diffraction of various samples according to the present invention, as well as two commercially available products; and,

(3) FIG. 2 shows a comparison of the cumulative intrusion compared to the pore size for various samples according to the present invention, and one commercially available product.

DETAILED DESCRIPTION OF THE INVENTION

(4) The invention is described in preferred embodiments in the following description. Reference throughout this specification to one embodiment, an embodiment, or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases in one embodiment, in an embodiment, and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

(5) The terms sorbent, adsorbent, and absorbent as used herein refer to the ability of a material to take in or soak up liquid or gas components on the surface thereof or to assimilate such components into the body thereof.

(6) As mentioned above, a composition capable of removing chlorides from a gaseous stream and a process of using same have been invented. The compositions have sufficient chloride capacity, offer comparable creation of green oil, and have sufficient structural integrity to be utilized as sorbents in a chloride removal process.

(7) With these general principles in mind, one or more embodiments of the present invention will be described with the understanding that the following description is not intended to be limiting.

(8) In a broad aspect, the compositions of the present invention comprise at least two zinc carbonates and an alumina material, such aluminum oxide (Al.sub.2O.sub.3). The two zinc carbonates are different from each other. At least one of zinc carbonates is hydrozincite (Zn.sub.5(CO.sub.3).sub.2(OH).sub.6) or smithsonite (zinc carbonate (ZnCO.sub.3)). It is preferred that one of the zinc carbonates is hydrozincite and the other zinc carbonate is smithsonite.

(9) The alumina used in the compositions of the present invention preferably comprises less than about 10% by weight (wt %) of the composition, or less than about 5 wt % of the composition. Throughout this application, the term about with respect to weight percentages means +/5, or +/2.5, or +/1. While the compositions of the present invention include alumina, the compositions are essentially free of boehmite (aluminum oxide hydroxide (AlO(OH)).

(10) In addition to the two zinc carbonates and the alumina, the compositions may include other materials, including, for example zinc oxide (ZnO), natrite (Na.sub.2CO.sub.3), nahcolite (NaHCO.sub.3), and zinc oxalate hydroxide (Zn.sub.2C.sub.2O.sub.4.3Zn(OH).sub.2). The compositions may comprise about 42 wt % zinc and about 16 wt % sodium, and between 0 to 10 wt % aluminum. These weight percentages reflect the metal salts, such as an oxide, carbonate, bicarbonate, hydroxide, hydrocarbonate, etc. In the compositions, a molar ratio of sodium to zinc may be between about 0.95 to 1.10. Additionally, in the compositions, a molar ratio of sodium to alumina may be between about 5.0 to 6.0.

(11) At least two solid and one liquid component are needed to produce the reactive composite composition of the present invention which can be formed into materials to be used as a sorbent. A first solid preferably comprises an alkali metal carbonate in a powder form. Small particles, preferably about 5 to 10 microns in diameter, are employed. One carbonate component that has been found to provide excellent results in the present invention is the natural carbonate (soda ash) ore known as Trona, however, other solids that can be used include Nahcolite, Wegscheiderite (Na.sub.2CO.sub.3.NaHCO.sub.3), Thermonatrite (Na.sub.2CO.sub.3.H.sub.2O), Shortite (Na.sub.2CO.sub.3.2CaCO.sub.3), and Eitelite (Na.sub.2CO.sub.3.MgCO.sub.3). One such carbonate that has been found especially useful is a natural sodium sesquicarbonate, marketed by Solvay Chemicals, Houston, Tex. as Solvay T-200. A sesquicarbonate has a formula of Na.sub.2CO.sub.3.NaHCO.sub.3.2H.sub.2O. It produces 1.5 mols sodium carbonate (Na.sub.2CO.sub.3) upon heating at sufficiently high temperature. Other solids that can be used include Nahcolite, Wegscheiderite (Na.sub.2CO.sub.3.NaHCO.sub.3), Thermonatrite (Na.sub.2CO.sub.3.H.sub.2O), Shortite (Na.sub.2CO.sub.3.2CaCO.sub.3), and Eitelite (Na.sub.2CO.sub.3.MgCO.sub.3).

(12) The second solid material zinc carbonate preferably comprises of following characteristics in Table 1, below.

(13) TABLE-US-00001 TABLE 1 Specification Determination Units Min Max Zinc As Zn % 56 60 Lead As Pb (dried basis) % 0 0.1 Other heavy metals (dried basis) % 0 0.3 Sulphur as S (Room Temp) % 0 0.3 Sodium Oxide as Na.sub.2O (Room Temp) % 0 1 Surface Area m.sup.2/g 50 LOD at 1050 C. % 0 2 Tapped Bulk Density Lbs./ft.sup.3 25 50 (tapped to constant volume) Chloride as Cl ppm 0 1000

(14) The third component is water, or optionally an aqueous solution of a salt, which plays an important role in facilitating a reaction between the carbonate and alumina powder. The preferred metal salt is selected from the group consisting of sodium carbonate and sodium silicate.

(15) Additional components may be added to enhance porosity or strength.

(16) After the components are mixed, for example in a nodulizer, the produced particles are cured (or calcined) at a temperature between 149 to 399 C. (about 300 to 750 F.), or between about 260 to 316 C. (500 to 600 F.) for approximately 1 hour, however, other times may be utilized. During the heating, hydrozincite is formed. Additionally, smithsonite and hydrozincite will decompose to varying extents to form zinc oxide. Furthermore, as a result of the curing, the Trona converts to sodium carbonate. The resulting cured particles will include at least one, and preferably both, of smithsonite and hydrozincite.

(17) A sample new sorbent was made by using the Nodulization technique disclosed in U.S. Pat. No. 7,758,837. A powder blend by using T-200 sesquicarbonate and basic ZnCO.sub.3 at a molar ratio of sodium to zinc of about 0.95-1.10 was placed in a small rotating pan made from the bottom of a plastic bottle. The pan had a diameter of about 12.7 cm (5 inches) and a height of about 15.2 cm (6 inches). It was rotated at about 120 rpm at an inclination of about 45 degrees. The powder blend was occasionally stirred using a spatula and hand sprayed with water to form particulates. A total of about 20 g water was added before the particulates began to stick together. At that point, the addition of water was ceased and a small amount of additional blend was added in order to restore the free flowing pattern of the particulates. The particulates had a broad particle size distribution ranging from about 40 mesh to about 3 mesh. Other than some spherical beads, most of the particles had a rather irregular form. All particulates were placed in a closed glass container and allowed to settled for about 2 hours followed by curing at 149 C. (300 F.), 260 C. (500 F.), and 399 C. (750 F.), respectively for about 1 hour in an air circulated oven. The material lost about 30% of its weight upon curing. After cooling, the size fraction 58 mesh of the particulates was screened out for further testing, XRD and Cl pickup in particular.

(18) FIG. 1 depicts an x-ray diffraction of the three samples. Additionally, two different samples of a commercially available sorbent are also depicted on FIG. 1one having essentially no zinc (#1) and one including an alumina binder (#2). The compositions of the three new samples and two commercially available products are depicted in TABLE 2, below.

(19) TABLE-US-00002 TABLE 2 Samples Zn Na Al Mol Mol Crush (ref. no. in FIG. 1) wt % wt % wt % Na/Zn Na/Al Strength Commercially 0 9.33 40.4 0.27 6.0 Lbf available #1 (10) Commercially 25.6 13.8 12.3 1.53 1.31 2.5 Lbf available #2 (12) New cured at 40-44 15-17 0-10 .95-1.10 5-6 8 Lbf 149 C. (14) New cured at 40-44 15-17 0-10 .95-1.10 5-6 6.5 Lbf 260 C. (16) New cured at 40-44 15-17 0-10 .95-1.10 5-6 3 Lbf 399 C. (18)

(20) As shown in FIG. 1, the x-ray diffraction of the new sample 14 cured at 149 C. indicated the presence of hydrozincite and smithsonite along with zincite (ZnO), natrite (Na.sub.2(CO.sub.3)), nacolite (NaHCO.sub.3), zinc oxalate hydroxide (Zn.sub.2C.sub.2O.sub.4.3Zn(OH).sub.2). Additionally, the x-ray diffraction of the new sample 16 cured at 260 C. indicated the presence of hydrozincite and smithsonite along with zincite (ZnO), natrite (Na.sub.2(CO.sub.3)), nacolite (NaHCO.sub.3), zinc oxalate hydroxide (Zn.sub.2C.sub.2O.sub.4.3Zn(OH).sub.2).

(21) In contrast, an x-ray diffraction of the new sample 18 cured at 399 C. (750 F.) indicated the presence of zincite, and natrite, but no hydrozincite or smithsonite. A similar x-ray diffraction of the commercially available sample 12 which includes an alumina binder indicated the presence of zincite, natrite and boehmite, but no hydrozincite or smithsonite. Finally, the x-ray diffraction of the commercially available sample 10 that was relatively free of zinc indicated no zinc compounds in the sample.

(22) Thus, in general an x-ray diffraction of a composition according to the present invention, would have at least one set of two-theta peaks at: 25.00 and 32.50 (indicating smithsonite); 13.00 and 36.00 (indicating hydrozincite); or, 12.80 and 17.30 (unidentified, but possibly zinc carbonate hydroxide hydrate). In some embodiments, the compositions would have two of these three sets of peaks, or all three sets. The compositions may also include additional materials, and, for example, an x-ray diffraction may include two-theta peaks at: 34.30 (indicating zincite); 35.00 and 38.00 (indicating natrite); and, 30.50 and 34.50 (indicating hydrogen sodium carbonate). Furthermore, in the composition according to the present invention, an x-ray diffraction should indicate the lack of a two-theta peak at 14.50 (for boehmite).

(23) FIG. 2 shows the cumulative intrusion compared to the pore diameter for the three samples discussed above, along with an uncured sample of the new sorbent 20, as well as commercially available sample 12 which includes an alumina binder, discussed above with respect to FIG. 1. As should be appreciated, FIG. 2 indicates that the commercially available sample 12 which includes an alumina binder has the greatest, total pore volume. While this may be generally desirable, as shown above in TABLE 2, the commercially available sample 12 which includes an alumina binder has the lowest crush strength. Furthermore, as demonstrated in FIG. 2, the relationship between the cure temperature of the new sorbents and the total pore volume of the samples, as well as the crush strength from TABLE 2, is not a linear relationship.

(24) A comparison of the theoretical chloride capacity of the new sample compared to the two commercially available samples discussed above in FIG. 1 is shown below in TABLE 3.

(25) TABLE-US-00003 TABLE 3 Pore Theoretical Chloride Bed Density BET SA Volume Capacity (g/cc) (m.sup.2/g) (cc/g) (g Cl/100 g sample) Commercially 0.827 170 0.289 14.4 available #1 (10) Commercially 0.751 73 0.170 49.0 available #2 (12) New sample 0.85-.95 30-35 0.130 69.5

(26) Accordingly, based upon the data in TABLE 3, the new sample had smaller pore volume, but greater theoretical chloride capacity. In testing, samples prepared according to the present invention showed a 48% longer cycle length for a 10 second contact time compared to the commercially available sample 12 which includes an alumina binder. For a 15 second contact time experiment, the sample prepared according to the present invention has a 33% longer cycle length compared to the commercially available sample 12 which includes an alumina binder.

(27) It is believed that the improved qualities and characteristics of the present invention may be due to the increased amount of active material, and less binder. Although not intending to be bound by any particular theory, it is believed that the zinc in the compounds of the present invention are more dispersed with a greater formation of Na.sub.2ZnCl.sub.4.

(28) Thus, the compounds according to the present invention, are believed to at least achieve the same chloride capacity as existing compounds, with a greater crush strength and with about the same propensity to produce green oil as existing compounds. Thus, the compositions could be used to remove chloride compounds from gas streams, in particular, gas streams associated with petrochemical processes, especially those in which chloride compounds are likely to form, such as the off gas stream of a catalytic reforming unit.

(29) It should be appreciated and understood by those of ordinary skill in the art that specifics of same aspects of the present invention are well within the knowledge of those of ordinary skill in the art and a description of same is not necessary for practicing or understanding the embodiments of the present invention.

(30) Indeed, the use of such an adsorbent is well within the skill of those of ordinary skill in the art. For example, the adsorbent could be loaded into a vessel. Any particular vessel could be used, and the vessel may include multiple beds. A stream including a chloride contaminant could be introduced into the vessel, and a purified stream having a lower concentration of chlorides may be recovered. More than one vessel may be provided, for example, in a lead-lag configuration. One of ordinary skill in the art will appreciate that the foregoing brief description may have excluded equipment which is typically used such as valves, pumps, filters, coolers, etc. as it is believed that the specifics of same are well within the knowledge of those of ordinary skill in the art and a description of same is not necessary for practicing or understanding the embodiments of the present invention.

SPECIFIC EMBODIMENTS

(31) While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims.

(32) A first embodiment of the invention is a composition comprising a first zinc carbonate; a second zinc carbonate different than the first zinc carbonate; an alumina material, wherein the alumina comprises less than 10 wt % of the composition, and wherein the first zinc carbonate comprises hydrozincite, and wherein the composition has been cured at a temperature between 149 to 399 C. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the second zinc carbonate comprises smithsonite. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the alumina comprises less than 5 wt % of the composition. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the composition includes at least two pairs of x-ray diffraction peaks at a two-theta value selected from the group consisting of about 12.80 and about 17.30; about 13.00 and about 36.00; and, about 25.00 and about 32.50. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the composition further includes at least one x-ray diffraction peak or pair of peaks at a two-theta value selected from the group consisting of about 34.30; about 35.00 and 38.00; and, about 30.50 and about 34.50. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the composition has been cured at a temperature between 260 to 316 C. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the composition lacks an x-ray diffraction peak at a two-theta value of about 14.50. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising zinc oxide. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising about 42 wt % zinc. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising about 16 wt % sodium.

(33) A second embodiment of the invention is a composition for adsorbing chloride compounds, the composition comprising a first zinc carbonate, wherein the first zinc carbonate comprises hydrozincite or smithsonite; a second zinc carbonate different than the first zinc carbonate; an alumina material; and, zinc oxide. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the composition includes at least two pairs of x-ray diffraction peaks at a two-theta value selected from the group consisting of about 12.80 and about 17.30; about 13.00 and about 36.00; and, about 25.00 and about 32.50. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the first zinc carbonate comprises hydrozincite, and wherein the second zinc carbonate comprises smithsonite. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the composition has been cured at a temperature between 260 to 316 C. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising sodium carbonate. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the composition comprises about 42 wt % zinc and about 16 wt % sodium. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the composition is substantially free of boehmite.

(34) A third embodiment of the invention is a process for removing chloride compounds from a gaseous stream, the process comprising passing a gaseous stream to an adsorption zone, the adsorption zone comprising an adsorbent and being operated under conditions to remove chloride compounds from the gaseous stream, wherein the adsorbent comprises a first zinc carbonate being hydrozincite or smithsonite, a second zinc carbonate different than the first zinc carbonate, and, zinc oxide. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the adsorbent comprises about 42 wt % zinc. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the first zinc carbonate comprises smithsonite, and wherein the second zinc carbonate comprises hydrozincite, and wherein the adsorbent is substantially free of boehmite.

(35) Without further elaboration, it is believed that using the preceding description that one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of this invention, without departing from the spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limiting the remainder of the disclosure in any way whatsoever, and that it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

(36) In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

(37) While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.