High surface area layered double hydroxides

Abstract

Layered double hydroxides having a high surface area (at least 125 m.sup.2/g) and the formula (I)
[M.sup.z+.sub.1?xM.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.sub.+bH.sub.2O.c(AMO-solvent)(I)
wherein M and M are different and each is a charged metal cation (and must be present), z=1 or 2; y=3 or 4, 0<x<0.9, b is 0 to 10, c=0 to 10, X is an anion, n is the charge on the anion, and a=z(1?x)+xy?2; AMO-solvent is aqueous miscible organic solvent, may be prepared by a method which comprises a) precipitating a layered double hydroxide having the formula
[M.sup.z+.sub.1?xM.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.sub.+bH.sub.2O wherein M, M, z, y, x, a, b and X are as defined above from a solution containing the cations of the metals M and M and the anion X.sup.n?; b) ageing the layered double hydroxide precipitate obtained in step a) in the original solution; c) collecting, then washing the layered double hydroxide precipitate; d) dispersing the wet layered double hydroxide in an AMO solvent so as to produce a slurry of the layered double hydroxide in the solvent; e) maintaining the dispersion obtained in step d); and f) recovering and drying the layered double hydroxide. The high surface area products have low particle size and are particularly suitable for use as catalysts, catalyst supports, sorbents and coatings.

Claims

1. A method of preparing a layered double hydroxide having a specific surface area of at least 125 m.sup.2/g and having the formula:
[M.sup.z+.sub.1+xM.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.sub.+bH.sub.2O.c(AMO-solvent)(I) wherein M and M are different and each is a charged metal cation (and must be present), z=1 or 2; y=3 or 4, 0<x<0.9, b is 0 to 10, 0<c?10, X is an anion selected from at least one of halide, inorganic oxyanion, anionic surfactants, anionic chromophores, and anionic UV absorbers, wherein the inorganic oxyanion is selected from carbonate, bicarbonate, hydrogenphosphate, dihydrogenphosphate, nitrite, nitrate, sulphate or phosphate or a mixture of two or more thereof, n is the charge on the anion, a=z(1?x)+xy?2; and AMO-solvent is an aqueous miscible organic solvent having a solvent polarity (P) in the range 3.8 to 9, which method comprises a) precipitating a layered double hydroxide having the formula
[M.sup.z+.sub.1?xM.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.sub.+bH.sub.2O wherein M, M, z, y, x, a, b and X are as defined above from a solution containing the cations of the metals M and M and the anion X.sup.n?; b) ageing the layered double hydroxide precipitate obtained in step a) in the original solution; c) collecting the layered double hydroxide precipitate by filtration, then washing the layered double hydroxide precipitate until the washing solution has a pH which is substantially neutral; d) dispersing the wet layered double hydroxide precipitate in an AMO-solvent so as to produce a slurry of the layered double hydroxide in the solvent, wherein the AMO-solvent is an aqueous miscible organic solvent having a solvent polarity (P) in the range 3.8 to 9; e) maintaining the dispersion obtained in step d); and f) recovering and drying the layered double hydroxide.

2. A method according to claim 1, wherein, in formula (I), when z is 2, M is Mg, Zn, Fe, Ca, Sn Ni, Cu, Co, Mn or Cd or a mixture of two or more of these, or when z is 1, M is Li.

3. A method according to claim 1, wherein in step a) the layered double hydroxide precipitate is formed by introducing metal (M.sup.z++M.sup.y+) solution to the anion (X.sup.n?) solution with a drop rate in the range of 0.1 to 3.5{mol(M.sup.z++M.sup.y+)}/{mol(anion)*min}.

4. A method according to claim 1, wherein in step a) the layered double hydroxide is precipitated from the cation and anion containing solution which either additionally contains NaOH or to which NaOH solution is added separately to adjust pH of solution to a predetermined value.

5. A method according to claim 1, wherein in step b) the layered double hydroxide precipitate is aged in the original solution for less than 24 hours.

6. A method according to claim 1, wherein in step c) the washed layered double hydroxide precipitate is then rinsed with AMO-solvent.

7. A method according to claim 1, wherein in step d) the wet layered double hydroxide obtained in step c) is dispersed and maintained in AMO-solvent under stirring.

8. A method according to claim 1, wherein in step e) the dispersion obtained in step d) is maintained for up to 96 hours.

9. A method according to claim 1, wherein after step e) the layered double hydroxide is collected as wet form and is dispersed in a fresh volume of the AMO solvent and the dispersion is maintained for at least two hours.

10. A method according to claim 1, wherein in step f), the layered double hydroxide is recovered by filtration and the recovered layered double hydroxide is dried in an oven or by a spray dryer.

11. A method according to claim 1, wherein, in formula (I), when y is 3, M is Al, Ga, Y, In, Fe, Co, Ni, Mn, Cr, Ti, V, or La, or when y is 4, M is Sn, Ti or Zr or a mixture thereof.

12. A method according to claim 11, wherein M is Al.

13. A method according to claim 12, wherein the layered double hydroxide is selected from Zn/Al, Mg/Al, Ca/Al, Ni/Al, and Cu/Al.

14. A method according to claim 13, wherein the layered double hydroxide is an Mg/Al layered double hydroxide.

15. A layered double hydroxide having a specific surface area of at least 125 m.sup.2/g, a BET pore volume (N.sub.2) of at least 0.5 cc/g and having the formula:
[M.sup.z+.sub.1?xM.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n+).sub.a/n.sub.+bH.sub.2O.c(AMO-solvent)(I) wherein M and M are different and each is a charged metal cation (and must be present), z=1 or 2; y=3 or 4, 0<x<0.9, b is 0 to 10, 0<c?10, X is an anion selected from at least one of halide, inorganic oxyanion, anionic surfactants, anionic chromophores, and anionic UV absorbers, wherein the inorganic oxyanion is selected from carbonate, bicarbonate, hydrogenphosphate, dihydrogenphosphate, nitrite, nitrate, sulphate or phosphate or a mixture of two or more thereof, n is the charge on the anion, a=z(1?x)+xy?2; and AMO-solvent is an aqueous miscible organic solvent having a solvent polarity (P) in the range 3.8 to 9.

16. A layered double hydroxide according to claim 15, wherein the layered double hydroxide has a specific surface area of at least 240 m.sup.2/g.

17. A layered double hydroxide according to claim 15, wherein the layered double hydroxide has a BET pore volume (N.sub.2) of at least 1.0 cc/g.

18. A layered double hydroxide according to claim 15, wherein the layered double hydroxide is dried by spray drying and has an agglomerated particle size less than 30 ?m.

19. A layered double hydroxide according to claim 15, wherein the layered double hydroxide has a particle size less than 150 ?m.

20. A layered double hydroxide according to claim 19, wherein the layered double hydroxide has a particle size less than 30 ?m.

Description

(1) Further advantages and features of the subject-matter of the present invention can be taken from the following detailed description taking in conjunction with the drawing, in which:

(2) FIG. 1: TEM images of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 1 before drying

(3) FIG. 2: SEM images of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 1 after spray drying

(4) FIG. 3: XRD pattern of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 1 before drying a) only washed with water, b) dispersed in acetone for 48 hr.

(5) FIG. 4: SEM images of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 2 after drying by oven

(6) FIG. 5: SEM images of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 2 after spray drying

(7) FIG. 6: N.sub.2-sorption isotherm of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 2 after drying by oven

(8) FIG. 7: N.sub.2-sorption isotherm of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 2 after spray drying

(9) FIG. 8: SEM images of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 3 after drying by oven

(10) FIG. 9: SEM images of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 3 after spray drying

(11) FIG. 10: N.sub.2-sorption isotherm of Mg.sub.3AlSO.sub.4 LDHs obtained from Example 9 after drying in vacuum oven

(12) FIG. 11: TEM images of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 10 before drying (A) water washed (B) 1000 mL of rinsed acetone

(13) FIG. 12: N.sub.2-sorption isotherm of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 10 rinsed with acetone of 100 mL, 300 mL and 1000 mL.

(14) FIG. 13: BET surface area and LDH layers of of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 10 rinsed with different amount of acetone.

(15) FIG. 14: BET surface area and LDH layers of of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 10 dispersed in acetone for different dispersion time.

(16) FIG. 15: BET surface area and LDH layers of of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 10 dispersed in acetone for different dispersion cycles.

(17) FIG. 16: N.sub.2-sorption isotherm of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 11 dispersed in acetone for 1 h, 2 h and 4 h.

(18) FIG. 17: BET surface area and LDH layers of of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 11 dispersed in acetone for different dispersion time.

(19) FIG. 18: BET surface area and LDH layers of of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 11 dispersed in acetone for different dispersion cycles.

EXAMPLES

Example 1

(20) A metal precursor solution was prepared by dissolving 9.6 g of Mg(NO.sub.3).sub.2.6H.sub.2O and 4.68 g of Al(NO.sub.3).sub.3.9H.sub.2O in 50 mL deionized water. A base solution was prepared by dissolving 4 g of NaOH and 2.65 g of Na.sub.2CO.sub.3 in 200 mL of deionized water. The metal precursor solution was added quickly into base solution under visciously stirring. After 30 min, the resulting slurry was collected by filtration and washed thoroughly with water and acetone successively. The washed filter cake was re-dispersed into acetone (200 mL) with stirring at 60? C. After 48 h, the acetone in the suspension was removed and fresh acetone (200 mL) was introduced. The obtained new suspension was stirred at room temperature for 2 h. The suspension was filtered to collect the LDH solid which was then washed thoroughly with acetone. The final product [Mg.sub.0.75Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.4H.sub.2O.0.1 (acetone)=(Mg.sub.3AlCO.sub.3 LDH) was dried in an oven at 60? C. overnight.

(21) The BET surface area and pore volume of the resulting Mg.sub.3?AlCO.sub.3 LDH are shown in Table 1. The morphology of the Mg.sub.3AlCO.sub.3 before drying is presented in FIG. 1. The morphology of the Mg.sub.3AlCO.sub.3 LDH after drying by spray dryer are presented in SEM images in FIG. 2. The purity of the obtained Mg.sub.3AlCO.sub.3 LDH was examined by X-Ray Diffraction as shown in FIG. 3.

(22) TABLE-US-00001 TABLE 1 BET surface area and pore volume of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 1. Range of feed rate BET Total pore Drying to spray dryer surface volume Methods (mL/min) area (m.sup.2/g) (cc/g) Oven, 65? C. 141 0.71 (overnight) Filter + vacuum 180 0.92 Spray dryer* 20-25 248 1.99 *all the samples dried using spray dryer (the same as below) were conducted in the same conditions, which is using the same outlet temperature of 55? C.

Example 2

(23) [Mg.sub.0.75Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.0.1H.sub.2O.0.1(acetone)=Mg.sub.3AlCO.sub.3 LDH was synthesized by adding 200 mL Mg(NO.sub.3).sub.2.6H.sub.2O (0.15 mol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.05 mol) solution drop-wise into a 200 ml Na.sub.2CO.sub.3 (0.10 mol) solution with a drop rate in the range of 0.1-3.5 {mol(M.sup.z++M.sup.y+)}/{mol(anion)*min}. The pH of the precipitation solution was controlled at 10 using a NaOH solution (4M), the resulting slurry was left for 16 hrs at room temperature. The obtained LDH slurry was filtered and washed with deionized water until a pH=7 was obtained and then the filtered solid was washed with acetone 500 ml through suction filter funnel. The wet cake was re-dispersed in 1000 ml acetone for 1 hr.

(24) Half of the LDH produced, suspended in acetone, was dried by oven at 65? C. and the other half was dried by spray drying in a N.sub.2 atmosphere. The BET surface area and pore volume of the resulting [Mg.sub.0.75Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.1H.sub.2O.0.1(acetone)=(Mg.sub.3AlCO.sub.3 LDH) Mg.sub.3AlCO.sub.3 LDH are shown in Table 2. The morphology of Mg.sub.3AlCO.sub.3 LDH after drying by oven and spray dryer are comparatively presented in SEM images in FIGS. 4 and 5, respectively. N.sub.2-sorption isotherm of Mg.sub.3AlCO.sub.3 LDHs obtained after drying by oven and spray dryer were shown in FIGS. 6 and 7, respectively.

(25) TABLE-US-00002 TABLE 2 BET surface area and pore volume of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 2. Range of feed rate Total pore Drying to spray dryer BET surface volume Methods (mL/min) area (m.sup.2/g) (cc/g) Oven, 65? C. 154 0.88 (overnight) Spray dryer 10-15 316 1.37 Spray dryer 15-20 330 1.36 Spray dryer 20-25 333 1.45 Spray dryer 25-30 314 1.19

Example 3

(26) [Mg.sub.0.75Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.1H.sub.2O.0.1 (acetone)=Mg.sub.3AlCO.sub.3 LDH was synthesized by adding 200 mL Mg(NO.sub.3).sub.2.6H.sub.2O (0.15 mol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.05 mol) solution drop-wise into a 200 mL Na.sub.2CO.sub.3 (0.10 mol) solution with the drop rate in the range of 0.1-3.5 {mol(M.sup.z++M.sup.y+)}/{mol(anion)*min}. The pH of the precipitation solution was controlled at lousing a NaOH solution (4 M). After 30 min. of ageing in original solution, the resulting slurry was filtered and washed with deionized water until a pH=7 was obtained. The filtered slurry was washed with acetone 500 mL through suction filter funnel followed by dispersion in 500 mL of acetone. After 16 hrs of stirring, the suspension was filtered and introduced fresh acetone (1000 mL) for another 1 hr of stirring. The half of LDH suspended in acetone was dried by oven at 65? C. and the other half was dried by spray drying in a N.sub.2 atmosphere. The BET surface area and pore volume results of the resulting Mg.sub.3AlCO.sub.3 LDH are shown below in Table 3. The morphology of Mg.sub.3AlCO.sub.3 LDH after drying by oven and spray dryer are comparatively presented in SEM images in FIGS. 8 and 9, respectively.

(27) TABLE-US-00003 TABLE 3 BET surface area and pore volume of Mg.sub.3AlCO.sub.3 LDHs obtained from Example 3. Range of feed rate Total pore Drying to spray dryer BET surface volume Methods (mL/min) area (m.sup.2/g) (cc/g) Oven, 65? C. 278 1.10 (overnight) Spray dryer 25-30 326 1.25

Example 4

(28) [Ni.sub.0.075Mg.sub.0.675Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.42H.sub.2O.0.13(acetone)=Ni.sub.0.3Mg.sub.2.7AlCO.sub.3 LDH was synthesized by adding 700 mL Ni(NO.sub.3).sub.2.6H.sub.2O (0.0525 mol) and Mg(NO.sub.3).sub.2.6H.sub.2O (0.4725 mol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.175 mol) solution drop-wise into a 700 ml Na.sub.2CO.sub.3 (0.35 mol) solution with a drop rate in the range of 0.1-3.5 {mol(M.sup.z++M.sup.y+)}/{mol(anion)*min}. The pH of the precipitation solution was controlled at 10 using a NaOH solution (4M), the resulting slurry was left for 16 hrs at room temperature. The obtained LDH slurry was filtered and washed with deionized water until a pH=7 was obtained and then the filtered solid was washed with acetone 3000 ml through suction filter funnel. The wet cake was re-dispersed in 1750 ml acetone for 1 hr.

(29) Half of the LDH produced, suspended in acetone, was dried by oven at 65? C. and the other half was dried by spray drying in a N.sub.2 atmosphere. The BET surface area and pore volume of the resulting [Ni.sub.0.075Mg.sub.0.675Al.sub.0.25 (OH).sub.2](CO.sub.3).sub.0.125.0.42H.sub.2O.0.13(acetone)=(Ni.sub.0.3Mg.sub.2.7AlCO.sub.3 LDH) Ni.sub.0.3Mg.sub.2.7AlCO.sub.3 LDH are shown in Table 4.

(30) TABLE-US-00004 TABLE 4 BET surface area and pore volume of Ni.sub.0.3Mg.sub.2.7AlCO.sub.3 LDHs obtained from Example 4. Range of feed rate Total pore Drying to spray dryer BET surface volume Methods (mL/min) area (m.sup.2/g) (cc/g) Oven, 65? C. 177 0.65 (overnight) Spray dryer 20-25 317 0.84

Example 5

(31) [Cu.sub.0.075Mg.sub.0.675Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.4H.sub.2O.0.1(acetone)=Cu.sub.0.3Mg.sub.2.7AlCO.sub.3 LDH was synthesized by adding 700 mL Cu(NO.sub.3).sub.2.6H.sub.2O (0.0525 mol) and Mg(NO.sub.3).sub.2.6H.sub.2O (0.4725 mol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.175 mol) solution drop-wise into a 700 ml Na.sub.2CO.sub.3 (0.35 mol) solution with a drop rate in the range of 0.1-3.5 {mol(M.sup.z++M.sup.y+)}/{mol(anion)*min}. The pH of the precipitation solution was controlled at 10 using a NaOH solution (4M), the resulting slurry was left for 16 hrs at room temperature. The obtained LDH slurry was filtered and washed with deionized water until a pH=7 was obtained and then the filtered solid was washed with acetone 3000 ml through suction filter funnel. The wet cake was re-dispersed in 1750 ml acetone for 1 hr.

(32) The LDH produced, suspended in acetone, was dried by spray drying in a N.sub.2 atmosphere. The BET surface area and pore volume of the resulting [Cu.sub.0.075Mg.sub.0.675Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.4H.sub.2O.0.1(acetone)=(Cu.sub.0.3Mg.sub.2.7AlCO.sub.3 LDH) Cu.sub.0.3Mg.sub.2.7AlCO.sub.3 LDH are shown in Table 5.

(33) TABLE-US-00005 TABLE 5 BET surface area and pore volume of Cu.sub.0.3Mg.sub.2.7AlCO.sub.3 LDHs obtained from Example 5. Range of feed rate Total pore Drying to spray dryer BET surface volume Methods (mL/min) area (m.sup.2/g) (cc/g) Spray dryer 20-25 252 1.00

Example 6

(34) [Co.sub.0.075Mg.sub.0.675Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.4H.sub.2O.0.1(acetone)=Co.sub.0.3Mg.sub.2.7AlCO.sub.3 LDH was synthesized by adding 700 mL Co(NO.sub.3).sub.2.6H.sub.2O (0.0525 mol) and Mg(NO.sub.3).sub.2.6H.sub.2O (0.4725 mol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.175 mol) solution drop-wise into a 700 ml Na.sub.2CO.sub.3 (0.35 mol) solution with a drop rate in the range of 0.1-3.5 {mol(M.sup.z++M.sup.y+)}/{mol(anion)*min}. The pH of the precipitation solution was controlled at 10 using a NaOH solution (4M), the resulting slurry was left for 16 hrs at room temperature. The obtained LDH slurry was filtered and washed with deionized water until a pH=7 was obtained and then the filtered solid was washed with acetone 3000 ml through suction filter funnel. The wet cake was re-dispersed in 1750 ml acetone for 1 hr.

(35) The LDH produced, suspended in acetone, was dried by spray drying in a N.sub.2 atmosphere. The BET surface area and pore volume of the resulting [Co.sub.0.075Mg.sub.0.675Al.sub.0.25 (OH).sub.2](CO.sub.3).sub.0.125.0.4H.sub.2O.0.1(acetone)=(Co.sub.0.3Mg.sub.2.7AlCO.sub.3 LDH) Co.sub.0.3Mg.sub.2.7AlCO.sub.3 LDH are shown in Table 6.

(36) TABLE-US-00006 TABLE 6 BET surface area and pore volume of Co.sub.0.3Mg.sub.2.7AlCO.sub.3 LDHs obtained from Example 6. Range of feed rate Total pore Drying to spray dryer BET surface volume Methods (mL/min) area (m.sup.2/g) (cc/g) Spray dryer 20-25 256 1.06

Example 7

(37) [Cu.sub.0.0075Ni.sub.0.0675Mg.sub.0.675Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.4H.sub.2O.0.1(acetone)=Cu.sub.0.03Ni.sub.0.27Mg.sub.2.7AlCO.sub.3 LDH was synthesized by adding 700 mL Cu(NO.sub.3).sub.2.6H.sub.2O (0.00525 mol) and Ni(NO.sub.3).sub.2.6H.sub.2O (0.04725 mol) and Mg(NO.sub.3).sub.2.6H.sub.2O (0.4725 mol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.175 mol) solution drop-wise into a 700 ml Na.sub.2CO.sub.3 (0.35 mol) solution with a drop rate in the range of 0.1-3.5 {mol(M.sup.z++M.sup.y+)}/{mol(anion)*min}. The pH of the precipitation solution was controlled at 10 using a NaOH solution (4M), the resulting slurry was left for 16 hrs at room temperature. The obtained LDH slurry was filtered and washed with deionized water until a pH=7 was obtained and then the filtered solid was washed with acetone 3000 ml through suction filter funnel. The wet cake was re-dispersed in 1750 ml acetone for 1 hr.

(38) The LDH produced, suspended in acetone, was dried by spray drying in a N.sub.2 atmosphere. The BET surface area and pore volume of the resulting [Cu.sub.0.0075Ni.sub.0.0675Mg.sub.0.675Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.4H.sub.2O.0.1(acetone)=(Cu.sub.0.03Ni.sub.0.27Mg.sub.2.7AlCO.sub.3 LDH) Cu.sub.0.03Ni.sub.0.27Mg.sub.2.7AlCO.sub.3 LDH are shown in Table 7.

(39) TABLE-US-00007 TABLE 7 BET surface area and pore volume of Cu.sub.0.03Ni.sub.0.27Mg.sub.2.7AlCO.sub.3 LDHs obtained from Example 7. Range of feed rate Total pore Drying to spray dryer BET surface volume Methods (mL/min) area (m.sup.2/g) (cc/g) Spray dryer 20-25 197 0.74

Example 8

(40) [Mg.sub.0.75Al.sub.0.25(OH).sub.2](NO.sub.3).sub.0.25.0.32H.sub.2O.0.12(acetone)=Mg.sub.3AlNO.sub.3 LDH was synthesized by adding 700 mL Mg(NO.sub.3).sub.2.6H.sub.2O (0.525 mol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.175 mol) solution drop-wise into a 700 ml NaNO.sub.3 (0.35 mol) solution with a drop rate in the range of 0.1-3.5 {mol(M.sup.z++M.sup.y+)}/{mol(anion)*min}. The pH of the precipitation solution was controlled at 10 using a NaOH solution (4M), the resulting slurry was left for 16 hrs at room temperature. The obtained LDH slurry was filtered and washed with deionized water until a pH=7 was obtained and then the filtered solid was washed with acetone 3000 ml through suction filter funnel. The wet cake was re-dispersed in 1750 ml acetone for 1 hr.

(41) The LDH produced, suspended in acetone, was dried by spray drying in a N.sub.2 atmosphere. The BET surface area and pore volume of the resulting [Mg.sub.0.75Al.sub.0.25(OH).sub.2](NO.sub.3).sub.0.25.0.32H.sub.2O.0.12(acetone)=(Mg.sub.3AlNO.sub.3 LDH) Mg.sub.3AlNO.sub.3 LDH are shown in Table 8.

(42) TABLE-US-00008 TABLE 8 BET surface area and pore volume of Mg.sub.3AlNO.sub.3 LDHs obtained from Example 8. Range of feed rate Total pore Drying to spray dryer BET surface volume Methods (mL/min) area (m.sup.2/g) (cc/g) Spray dryer 20-25 212 0.85

Example 9

(43) [Mg.sub.0.75Al.sub.0.25(OH).sub.2](SO.sub.4).sub.0.25.0.55H.sub.2O.0.13(acetone)=Mg.sub.3AlSO.sub.4 LDH was synthesized by adding 20 mL Mg(SO.sub.4).sub.2 (0.0375 mol) and Al(SO.sub.4).sub.3.16H.sub.2O (0.0125 mol) solution quickly into a 50 ml solution containing 0.025 mol of Na.sub.2SO.sub.4 and 0.075 mol of NaOH. The resulting slurry was left for 30 min at room temperature. The obtained LDH slurry was filtered and washed with deionized water until a pH=7 was obtained and then the filtered solid was washed with acetone 500 mL through suction filter funnel. The wet cake was re-dispersed in 300 mL acetone for 2 hrs. The slurry was filtered and redispersed in 300 mL acetone for 2 hrs.

(44) The LDH produced was filtrated and dried in vacuum oven for 16 hrs. The BET surface area and pore volume of the resulting [Mg.sub.0.75Al.sub.0.25(OH).sub.2](SO.sub.4).sub.0.25.0.55H.sub.2O.0.13(acetone)=(Mg.sub.3AlSO.sub.4 LDH) Mg.sub.3AlSO.sub.4 LDH are shown in Table 9. N.sub.2-sorption isotherm of Mg.sub.3AlSO.sub.4 LDHs after drying in vacuum oven can be shown in FIG. 10.

(45) TABLE-US-00009 TABLE 9 BET surface area and pore volume of Mg.sub.3AlSO.sub.4 LDHs obtained from Example 9. Range of feed rate Total pore Drying to spray dryer BET surface volume Methods (mL/min) area (m.sup.2/g) (cc/g) Vacuum oven 180 0.93 (Room temperature)

Example 10

(46) [Mg.sub.0.75Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.25.0.1H.sub.2O.0.1 (acetone)=Mg.sub.3AlCO.sub.3 LDH was synthesized by adding the metal precursor solution (20 mL) of 1.875 M Mg(NO.sub.3).sub.2.6H.sub.2O and 0.625 M Al(NO.sub.3).sub.3.9H.sub.2O into the 50 mL of 0.5 M Na.sub.2CO.sub.3 solution with a drop rate in the range of 0.1-3.5 mol {mol(M.sup.z++M.sup.y+)}/{mol(anion)*min}. The pH value was kept at ca. 10.0 by dropwise addition of a 4.0 M NaOH solution. After 30 min with stirring at room temperature, the slurry was washed with DI water until the pH was close to 7 following by being rinsed with certain amount of acetone (step 1: rinsed acetone). The obtained LDH wet cake was dispersed in acetone (300 mL) and stirred at room temperature for certain time (step 2: dispersion time). Then the LDH was filtered and re-dispersed into flesh acetone (300 mL) for dispersion cycle study (step 3: dispersion cycle) or dried in vacuum oven for 16 hrs. The BET surface area and pore volume of the resulting Mg.sub.3AlCO.sub.3 LDH in each step are shown in Tables 10-12. The morphology of wet Mg.sub.3AlCO.sub.3 LDH after water washing and 1000 mL of rinsed acetone are comparatively presented in TEM images in FIG. 11. N.sub.2-sorption isotherm of Mg.sub.3AlCO.sub.3 LDHs obtained after rinsing with different volumes of acetone were shown in FIG. 12. The surface area and LDH layers of Mg.sub.3AlCO.sub.3 LDHs after each step were shown in FIG. 13-15.

(47) TABLE-US-00010 TABLE 10 BET surface area and pore volume of Mg.sub.3AlCO.sub.3 LDHs obtained from Step 1 (Rinsed acetone) in Example 10. Drying Rinsed acetone BET surface Total pore Methods (mL) area (m.sup.2/g) volume (cc/g) Vacuum oven 0 0.07 0.002 (Room 300 163 0.79 temperature) 500 229 0.79 1000 339 1.34

(48) TABLE-US-00011 TABLE 11 BET surface area and pore volume of Mg.sub.3AlCO.sub.3 LDHs obtained from Step 2 (Dispersion time) in Example 10 (Rinsed acetone: 500 mL). Drying Dispersion BET surface Total pore Methods time (h) area (m.sup.2/g) volume (cc/g) Vacuum oven 0 0.07 0.002 (Room 1 363 1.18 temperature) 2 352 1.25 3 364 1.17

(49) TABLE-US-00012 TABLE 12 BET surface area and pore volume of Mg.sub.3AlCO.sub.3 LDHs obtained from Step 3 (Dispersion cycle) in Example 10 (Rinsed acetone: 500 mL, dispersion time: 1 h, 300 mL). Drying Dispersion BET surface Total pore Methods cycle area (m.sup.2/g) volume (cc/g) Vacuum oven 0 0.07 0.002 (Room 1 363 1.18 temperature) 2 204 0.93 3 269 1.13

Example 11

(50) [Mg.sub.0.75Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.25.0.4H.sub.2O.0.1(acetone) Mg.sub.3AlCO.sub.3 LDH was synthesized by adding the metal precursor solution (20 mL) of 1.875 M Mg(NO.sub.3).sub.2.6H.sub.2O and 0.625 M Al(NO.sub.3).sub.3.9H.sub.2O quickly into the 50 mL of 0.5 M Na.sub.2CO.sub.3 solution. The pH value was kept at ca. 10.0 by dropwise addition of a 4.0 M NaOH solution. After 30 min with stirring at room temperature, the slurry was washed with DI water until the pH was close to 7 following by being rinsed with certain amount of acetone (step 1: rinsed acetone). The obtained LDH wet cake was dispersed in acetone (300 mL) and stirred at room temperature for certain time (step 2: dispersion time). Then the LDH was filtered and re-dispersed into flesh acetone (300 mL) for dispersion cycle study (step 3: dispersion cycle) or dried in vacuum oven for 16 hrs.

(51) The BET surface area and pore volume of the resulting Mg.sub.3AlCO.sub.3 LDH in each step are shown in Table 13-14. N.sub.2-sorption isotherm of Mg.sub.3AlCO.sub.3 LDHs obtained after rinsing with different dispersion time of acetone were shown in FIG. 16. The surface area and LDH layers of Mg.sub.3AlCO.sub.3 LDHs after Step 2 and Step 3 were shown in FIG. 17-18.

(52) TABLE-US-00013 TABLE 13 BET surface area and pore volume of Mg.sub.3AlCO.sub.3 LDHs obtained from Step 2 (Dispersion time) in Example 11 (Rinsed acetone: 500 mL). Drying Dispersion BET surface Total pore volume Methods time (h) area (m.sup.2/g) (cc/g) Vacuum oven 0 0.08 0.00 (Room 1 90 0.55 temperature) 2 140 0.75 4 220 1.07 12 232 0.86

(53) TABLE-US-00014 TABLE 14 BET surface area and pore volume of Mg.sub.3AlCO.sub.3 LDHs obtained from Step 3 (Dispersion cycle) in Example 11 (Rinsed acetone: 500 mL, dispersion time: 1 h, 300 mL). Drying Dispersion BET surface Total pore volume Methods cycle area (m.sup.2/g) (cc/g) Vacuum oven 0 0.08 0.00 (Room 1 220 1.07 temperature) 2 269 0.93 3 238 1.13