SiO2-layered double hydroxide microspheres and their use as catalyst supports in ethylene polymerisation

Abstract

A catalyst system is provided which comprises a solid support material having, on its surface, one or more catalytic transition metal complex wherein the solid support material comprises SiO.sub.2@AMO-LDH microspheres having the formula I: (i) wherein, M.sup.z+ and M.sup.y+ are two different charged metal cations; z=1 or 2; y=3 or 4; 0<x<0.9; b is 0 to 10; c is 0.01 to 10, preferably >0.01 and <10; p>0 q>0; X.sup.n? is an anion with n>0, preferably 1?5a=z(1?x)+xy?2; and the AMO-solvent is an 100% aqueous miscible organic solvent. Preferably, M in the formula I is Al. Preferably, M in the formula I is Li, Mg or Ca. The catalyst system has use in the polymerization and/or copolymerization of at least one olefin to produce a homopolymer and/or copolymer.

Claims

1. A catalyst system comprising a solid support material having, on its surface, one or more catalytic transition metal complex wherein the solid support material comprises SiO.sub.2@AMO-LDH microspheres having the formula I
(SiO.sub.2).sub.p@{[M.sup.z+.sub.(1?x)M.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n?bH.sub.2O?c (AMO-solvent)}.sub.q wherein, M.sup.z+ and M.sup.y+ are two different charged metal cations; z=1 or 2; y=3 or 4; 0<x<0.9; b is 0 to 10; c is 0.01 to 10; p>0; q>0; X.sup.n? is an anion with n>0; a=z(1?x)+xy?2; and the AMO-solvent is an 100% aqueous miscible organic solvent.

2. The catalyst system according to claim 1, wherein the solid support material has the formula I in which M is one or more trivalent metal cations.

3. The catalyst system according to claim 1, wherein the solid support material has the formula I in which M is one or more divalent cation.

4. The catalyst system according to claim 1, wherein the solid support material has the formula I in which X.sup.n? is selected from CO.sub.3.sup.2?, OH.sup.?, F.sup.?, Cl.sup.?, Br.sup.?, I.sup.?, SO.sup.2?, NO.sub.3.sup.? and PO.sub.4.sup.3?, or a mixture thereof.

5. The catalyst system according to claim 1, wherein the solid support material has the formula I in which M is Mg, M is Al and X.sup.n? is CO.sub.3.sup.?.

6. The catalyst system according to claim 1, wherein the solid support material has the formula I in which the AMO-solvent is ethanol, acetone or methanol.

7. The catalyst system according to claim 1, wherein the catalytic transition metal complex is at least one complex of a metal selected from zirconium, iron, chromium, cobalt, nickel, titanium and hafnium, the complex containing one or more aromatic or heteroaromatic ligands.

8. The catalyst system according to claim 1, wherein the catalytic transition metal complex is a metallocene containing zirconium or hafnium.

9. The catalyst system according to claim 1, wherein the catalytic transition metal complex is at least one compound selected from. ##STR00006##

10. The catalyst system according to claim 1, wherein the system is obtained by a process comprising the step of activating the solid support material with an alkylaluminoxane, triisobutylaluminium (TIBA), triethylaluminium (TEA) or diethylaluminium chloride (DEAC).

11. The catalyst system according to claim 10, wherein the alkylaluminoxane is methylaluminoxane (MAO) or modified methylaluminoxane (MMAO).

12. A method of making the catalyst system of claim 1 which comprises (a) providing a solid support material comprising SiO.sub.2@AMO-LDH microspheres having the formula (I)
(SiO.sub.2).sub.p@{[M.sup.z+.sub.(1?x)M.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.bH.sub.2O.c(AMO-Solvent)}.sub.q(I) wherein, M.sup.z+ and M.sup.y+ are two different charged metal cations; z=1 or 2; y=3 or 4; 0<x<0.9; b is 0 to 10; c is 0.01 to 10; p>0, q>0; X.sup.n? is an anion with n>0; a=z(1?x)+xy?2; and the AMO-solvent is an aqueous miscible organic solvent, (b) treating the SiO.sub.2@AMO-LDH microspheres with at least one catalytic transition metal complex having olefin polymerisation catalytic activity.

13. The method according to claim 12, wherein the solid support material has the formula I in which M is one or more trivalent metal cations.

14. The method according to claim 12, wherein the solid support material has the formula I in which M is one or more divalent metal cations.

15. The method according to claim 12, wherein the solid support material has the formula I in which X.sup.n? is selected from CO.sub.3.sup.2?, OH.sup.?, F, Cl.sup.?, Br.sup.?, I.sup.?, SO.sup.2?, NO.sub.3.sup.? and PO.sub.4.sup.3?, or a mixture thereof.

16. The method according to claim 12, wherein the solid support material has the formula I in which M.sup.z+is Mg, M.sup.y+ is Al and X.sup.n? is CO.sub.3.sup.?.

17. The method according to claim 12, wherein the solid support material has the formula I in which AMO-solvent is ethanol, acetone or methanol.

18. The method according to claim 12, wherein the catalytic transition metal complex is at least one complex of a metal selected from zirconium, iron, chromium, cobalt, nickel, titanium and hafnium, the complex containing one or more aromatic or heteroaromatic ligands.

19. The method according to claim 12, wherein the catalytic transition metal complex is a metallocene containing zirconium or hafnium.

20. The method according to claim 12, wherein the catalytic transition metal complex is at least one compound selected from. ##STR00007##

21. The method according to claim 12, further comprising a step of calcining the SiO.sub.2@AMO-LDH microspheres, before the treating step (b).

22. The method according to claim 21, further comprising a step of treating the calcined SiO.sub.2@AMO-LDH with an alkylaluminoxane before the treating step (b).

23. The method according to claim 22, wherein the alkylaluminoxane is methylaluminoxane (MAO) or modified methylaluminoxane (MMAO).

24. A process for forming a polyethylene homopolymer or a polyethylene copolymer which comprises reacting olefin monomers in the presence of a system according to claim 1.

25. A process for producing a polymer of an olefin which comprises contacting the olefin with the solid catalyst system according claim 1.

26. The process according to claim 25, wherein the olefin is ethylene.

27. The process according to claim 25, wherein the process is performed at a temperature of 50-100? C.

28. The process according to claim 24, wherein the copolymer comprises 1-10 wt % of a (4-8 C) ?-olefin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a chart showing polymerisation activities of the catalyst supported metallocene complexes at temperatures from 50 to 90? C.

(2) FIG. 2 is a chart showing polymerisation activities of the catalyst supported metallocene complexes at times from 0 to 120 minutes.

(3) FIG. 3 shows SEM images of polymer produced using the silica@AMO-LDH metallocene catalyst support complex after 15 min, 1 h, and the original silica@AMO-LDH.

(4) FIG. 4 shows XRD patterns of SiO2@LDH microspheres prepared according to example 1 conventional water washing and acetone washing.

(5) FIG. 5 shows TEM images of SiO2@LDH microspheres with solid (example 1), yolk-shell (example 1 at 40? C.), and hollow (example 1 at pH 11) morphologies.

(6) FIG. 6 shows TEM images of SiO2@AMO LDH microspheres according to examples 5 and 7 at pH=10 and room temperature.

(7) FIG. 7 shows TEM images of SiO2@AMO-LDH (Mg:Ni:Al ratio of 2.7:0.3:1) microspheres with different morphologies according to example 6 at pH 10 and room temperature, pH 10 and 40? C., and pH 11 and 40? C.

PARTICULARLY PREFERRED EMBODIMENTS

(8) The following represent particular embodiments of the silica-layered double hydroxide:

(9) 1.1 The Silica-Layered Double Hydroxide Microspheres have the General Formula I
(SiO.sub.2).sub.p@{[M.sup.z+.sub.(1?x)My+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.bH.sub.2O.c(AMO-solvent)}.sub.q(I) wherein, M.sup.z+ is selected from Li.sup.+, Ca.sup.2+, Ni.sup.2+ or Mg.sup.2+, and M.sup.y+ is Al.sup.3+ or Fe.sup.3+; 0<x<0.9; b is 0 to 10; c is 0 to 10; p>0, q>0; X.sup.n? is selected from carbonate, hydroxide, nitrate, borate, sulphate, phosphate and halide (F.sup.?, Cl.sup.?, Br.sup.?, I.sup.?) anions; with n>0 (preferably 1-5) a=z(1?x)+xy?2; and the AMO-solvent is selected from methanol, ethanol or acetone.
1.2 The Silica-Layered Double Hydroxide Microspheres have the General Formula I
(SiO.sub.2).sub.p@{[M.sup.z+.sub.(1?x)My+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.bH.sub.2O.c(AMO-solvent)}.sub.q(I) wherein, M.sup.z+ is selected from Li.sup.+, Ca.sup.2+, Ni.sup.2+ or Mg.sup.2+, and M.sup.y+ is Al.sup.3+; 0<x<0.9; b is 0 to 10; c is 0 to 10; p>0, q>0; X.sup.n? is selected from CO.sub.3.sup.2?, NO.sub.3.sup.? or Cl.sup.?; with n>0 (preferably 1-5) a=z(1?x)+xy?2; and the AMO-solvent is ethanol or acetone.
1.3 The Silica-Layered Double Hydroxide Microspheres have the General Formula Ia
(SiO.sub.2).sub.p@{[M.sup.z+.sub.(1?x)Al.sup.3+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.bH.sub.2O.c(AMO-solvent)}.sub.q(Ia) wherein, M.sup.z+ is selected from Li.sup.+, Ca.sup.2+, Ni.sup.2+ or Mg.sup.2+; 0<x<0.9; b is 0 to 10; c is 0 to 10; p>0, q>0; X.sup.n? is selected from CO.sub.3.sup.2?, NO.sub.3.sup.? or Cl.sup.?; with n>0 (preferably 1-5) a=z(1?x)+xy?2; and the AMO-solvent is ethanol or acetone.
1.4 The Silica-Layered Double Hydroxide Microspheres have the General Formula Ia
(SiO.sub.2).sub.p@{[M.sup.2+.sub.(1?x)Al.sup.3+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.bH.sub.2O.c(AMO-solvent)}.sub.q(Ia) wherein, 0<x<0.9; b is 0 to 10; c is 0 to 10; p>0, q>0; X.sup.n? is selected from CO.sub.3.sup.2?, NO.sub.3.sup.? or Cl.sup.?; with n>0 (preferably 1-5) a=z(1?x)+xy?2; and the AMO-solvent is ethanol or acetone.
1.5 The Silica-Layered Double Hydroxide Microspheres have the General Formula Ib
(SiO.sub.2).sub.p@{[Mg.sup.2+.sub.(1?x)Al.sup.3+.sub.x(OH).sub.2].sup.a+(CO.sub.3.sup.2).sub.a/nbH.sub.2O.c(ethanol/acetone)}.sub.q(Ib) wherein, 0<x<0.9; b is 0 to 10; c is 0 to 10; p>0, q>0; a=z(1-x)+xy?2.
The following represent particular embodiments of the catalyst system:
2.1 The Catalyst System Comprises a Solid Support Material Having, on its Surface, One or More Catalytic Transition Metal Complexes Selected from:

(10) ##STR00004## wherein the solid support material comprises SiO.sub.2@AMO-LDH microspheres having the formula I
(SiO.sub.2).sub.p@{[M.sup.z+.sub.(1?x)M.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.bH.sub.2O.c(AMO-solvent)}.sub.q(I) wherein, M.sup.z+ is selected from Li.sup.+, Ca.sup.2+, Ni.sup.2+ or Mg.sup.2+, and M.sup.y+ is Al.sup.3+ or Fe.sup.3+; 0<x<0.9; b is 0 to 10; c is 0 to 10; p>0, q>0; X.sup.n? is selected from carbonate, hydroxide, nitrate, borate, sulphate, phosphate and halide (F.sup.?, Cl.sup.?, Br.sup.?, I.sup.?) anions; with n>0 (preferably 1-5) a=z(1?x)+xy?2; and the AMO-solvent is selected from methanol, ethanol or acetone.
2.2 The Catalyst System Comprises a Solid Support Material Having, on its Surface, One or More Catalytic Transition Metal Complexes Selected from:

(11) ##STR00005## wherein the solid support material comprises SiO.sub.2@AMO-LDH microspheres having the formula I
(SiO.sub.2).sub.p@{[M.sup.z+.sub.(1?x)Al.sup.3+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.bH.sub.2O.c(AMO-solvent)}.sub.q(Ia) wherein, M.sup.z+ is selected from Li.sup.+, Ca.sup.2+, Ni.sup.2+ or Mg.sup.2+; 0<x<0.9; b is 0 to 10; c is 0 to 10; p>0, q>0; X.sup.n? is selected from CO.sub.3.sup.2?, NO.sub.3? or Cl.sup.?; with n>0 (preferably 1-5) a=z(1?x)+xy?2; and the AMO-solvent is ethanol or acetone.

(12) Preferred, suitable, and optional features of any one particular aspect of the present invention are also preferred, suitable, and optional features of any other aspect.

(13) Experimental Details

(14) Preparation of Silica (SiO.sub.2) Nanoparticles

(15) St?Ber Method.

(16) The monodispersed silica spheres were synthesised using the St?ber method. Tetraethyl orthosilicate (TEOS) (amounts shown below) was added to a mixed solution of ammonia (35 wt %), deionised water and ethanol. The white suspension was left to stir vigorously for 17 h. The volume of deionised water and ethanol remained constant (30 mL and 50 mL, respectively). The volume of TEOS and ammonia was varied to achieve the desired size of silica sphere (13.7 mL, 9.15 mL and 3 mL of TEOS with 15 mL, 10 mL and 5 mL of ammonia for 800 nm, 550 nm and 300 nm silica spheres, respectively). The final solid was washed with ethanol and water, until washings were pH 7, followed by drying under vacuum overnight.

(17) Seeded Growth Method.

(18) Seeded growth is a two-stage synthesis. The first stage prepares the seeds. TEOS (1 mL) diluted in ethanol (4 mL), was added to a mixed solution of ammonia (10 mL, 35 wt %) and ethanol (46 mL) and left to stir vigorously for 2 h. Keeping the reaction conditions the same for the second stage of synthesis, the calculated amount of TEOS diluted in 4? volume of ethanol was added to the seed suspension at a rate of 6 mL/h. After all the TEOS was added the reaction was left to stir for a further 2 h to make sure the particles had reached their final size. The final solid was washed with ethanol (240 mL) and dried under vacuum overnight.

(19) Preparation of Silica@LDH Nanoparticles (SiO.sub.2@AMO-LDH).

(20) The silica@LDH particles were synthesised via the coprecipitation method. Silica spheres (100 mg) were dispersed in deionised water (20 mL) using ultrasound treatment. After 30 min, the desired anion salt (0.96 mmol), Na.sub.2CO.sub.3, was added to the solution and a further 5 min of sonication was carried out to form solution A. Next an aqueous solution (19.2 mL) containing M.sup.2+(NO.sub.3).sub.2.6H.sub.2O (0.96 mmol) (M.sup.2+=Mg, Ni) and M.sup.3+(NO.sub.3).sub.3.9H.sub.2O (0.48 mmol) (M.sup.3+=Al, Fe) was added at a rate of 60 mL/h to solution under vigorous stirring. The pH of the reaction solution was controlled with the addition of 1 M NaOH by an autotitrator, or was pre-set by the Ammonia method, where ammonia (0.8 mL, 35 wt %) was added at the beginning of the reaction. The obtained solid was collected with centrifugation at 4000 rpm for 5 min and then re-dispersed in deionised water (40 mL) and stirred for 1 h. The collection and re-dispersion was repeated twice. The suspension was then dried under vacuum for materials characterisation.

(21) Aqueous Miscible Organic Solvent Treatment.

(22) For the AMOST method, the silica@AMO-LDHs are initially formed using the previous procedures. However, before final isolation, the solid was washed with acetone (40 mL) and then re-dispersed in acetone (40 mL) and left to stir overnight. The suspension was then dried under vacuum for materials characterisation.

(23) Silica@AMO-LDH (SiO.sub.2@AMO-LDH) Characterisation.

(24) Silica@AMO-LDHs synthesised at room temperature with different pHs. Si NMR: pH 10:? (ppm)?108 (s), ?99 (s), ?86 (s); pH 11:? (ppm)?135??75. Al NMR: pH 10:? (ppm) 9.6 (s), 61 (s); pH 11:9.2 (s), 56 (s). Silica@AMO-LDHs synthesised at pH 10 at different temperatures. Si NMR: room temperature: ? (ppm)?108 (s), ?99 (s), ?86 (s); 40? C.: ? (ppm)?135??75. Al NMR: room temperature: ? (ppm) 9.6 (s), 61 (s); 40? C.:9.2 (s), 56 (s). Silica@AMO-LDHs synthesised with the AMOST method at room temperature and pH 10. Si NMR: ? (ppm) ?110 (s), ?101 (s), ?87 (s). Al NMR:? (ppm) 9.4 (s), 55 (s).

(25) Silica@AMO-LDH and AMO-LDH as Catalyst Supports.

(26) The silica@AMO-LDH used as a catalyst support contained a silica core (SiO.sub.2) (550 nm) prepared via the seeded growth method and an LDH layer (Mg/Al 2:1 with CO.sub.3.sup.2? anion) grown at pH 10 at room temperature which was treated with the AMOST method. The AMO-LDH used for comparison was an LDH (Mg/Al 2:1 with CO.sub.3.sup.2? anion) synthesised under the same conditions and was treated with the AMOST method. Silica@AMO-LDH and AMO-LDH samples were thermally treated at 150? C. for 6 h under vacuum (10.sup.?2 mbar). Two equivalents of thermally treated silica@AMO-LDH (750 mg) and one equivalent of methylaluminoxane (375 mg) were heated in toluene (40 mL) at 80? C. for 2 h, with swirling to the reaction every 10 minutes. The solvent was then removed under vacuum and the colourless solid dried in vacuo for 4 h to afford silica@AMO-LDH/MAO, yield: 89%. Similar process was carried out with the AMO-LDH, yield 84%. Finally, one equivalent of silica@AMO-LDH/MAO (500 mg) and 0.01 equivalent of yellow [(EBI)ZrCl.sub.2] (12 mg) were heated in toluene (25 mL) at 80? C. for 2 h, with swirling to the reaction every 10 minutes. The reaction mixture was then left to cool and the solid was allowed to settle. The solid went from colourless to orange in colour, and the solution was left colourless. The solvent was then removed under vacuum and dried in vacuo for 4 h to afford silica@AMO-LDH/MAO-[(EBI)ZrCl.sub.2] yield: 89%. The same process was carried out with the AMO-LDH/MAO-[(EBI)ZrCl.sub.2], yield: 93%.

(27) Ethylene Polymerisation Studies.

(28) The catalysts were tested for their ability to act as a catalyst for ethylene polymerisation under slurry conditions in the presence of TIBA ([TIBA].sub.0/[Zr].sub.0=1000). The reactions were performed with ethylene (2 bar) in a 200 mL ampoule, with the catalyst precursor (10 mg) suspended in hexane (50 mL). The reactions were run for 15-120 minutes at 50-90? C. controlled by heating in an oil bath. The polyethylene product was washed with pentane (3?50 mL) and the resulting polyethylene was filtered through a sintered glass frit.

(29) The polymerisation activity of the catalyst supported metallocene complexes plotted against temperature is shown in FIG. 1.

(30) FIG. 1 Polymerisation activities of the catalyst supported metallocene complexes at temperatures from 50 to 90? C. (a) AMO-LDH/MAO-[(EBI)ZrCl.sub.2] and (b) silica@AMO-LDH/MAO-[(EBI)ZrCl.sub.2]. Polymerisation conditions: 50 mL Hexane, 2 bar Ethylene, 1 h, [TIBA].sub.0/[Zr].sub.0=1000. AMO-LDH/MAO-[(EBI)ZrCl.sub.2] (a) shows a bell-shaped activity curve, typical for the immobilised [EBI(ZrCl.sub.2)], with the optimum temperature for polymerisation to be found between 70 and 80? C. (activity of 702 kg.sub.PE/molz.sub.r/h/bar at 80? C.), FIG. 1. The curve can be explained by the increase of the propagation rate with temperature, followed by the termination rate increasing after the optimum temperature. At 80? C., when silica@AMO-LDH/MAO-[(EBI)ZrCl.sub.2] was used, the activity is 3.5 times higher, 2494 kg.sub.PE/molz.sub.r/h/bar, than the activity of the AMO-LDH/MAO-[(EBI)ZrCl.sub.2]. The activities of this catalyst are very high on the Gibson scale. Above these temperatures we see a sharp drop in the activity of the complexes, as is expected as the rate of deactivation increases. This significant result demonstrates the advantage of the hierarchical structure; growing the LDH on the surface of silica spheres has resulted in a more active catalyst support.

(31) TABLE-US-00001 TABLE 1 Polymerisation data demonstrating the molecular weights (M.sub.w) and polydispersities (M.sub.w/M.sub.n) with Temperature varying from 50 to 90? C. for 1 h using silica@AMO-LDH/MAO-[(EBI)ZrCl.sub.2] Temperature (? C.) M.sub.w (g/mol) M.sub.w/M.sub.n 50 198251 5.60 60 171780 4.87 70 152496 4.99 80 100322 4.10 90 84265 3.93

(32) TABLE-US-00002 TABLE 2 Polymerisation data demonstrating the molecular weights (M.sub.w) and polydispersities (M.sub.w/M.sub.n) with Temperature varying from 50 to 90? C. for 1 h using AMO-LDH/MAO-[(EBI)ZrCl.sub.2] Temperature (? C.) M.sub.w (g/mol) M.sub.w/M.sub.n 50 276454 5.33 60 189953 5.09 70 150138 4.70 80 105312 4.96

(33) FIG. 2 Polymerisation activities of the catalyst supported metallocene complexes at times from 0 to 120 minutes. (a) AMO-LDH/MAO-[(EBI)ZrCl.sub.2] and (b) silica@AMO-LDH/MAO-[(EBI)ZrCl.sub.2]. Polymerisation conditions: 50 mL Hexane, 2 bar Ethylene, 1 h, [TIBA].sub.0/[Zr].sub.0.

(34) The silica@AMO-LDH and AMO-LDH supported metallocene complexes have been evaluated for ethylene polymerisation over a timescale of 0-120 minutes, at 70? C., FIG. 2. AMO-LDH/MAO-[(EBI)ZrCl.sub.2] (a) shows an initial increase in activity reaching a maximum at 15 min, 899 kg.sub.PE/molz.sub.r/h/bar, FIG. 2. After this point, there is a drop in activity, it appears that AMO-LDH/MAO-[(EBI)ZrCl.sub.2] is over its peak in activity and has approximately settled to the diffusion controlled limit. This can be explained by the rapidly increasing amounts of polyethylene in the polymerising medium that can hinder the interaction of the catalyst support with the ethylene. Silica@AMO-LDH/MAO-[(EBI)ZrCl.sub.2] (b) shows a similar pattern to AMO-LDH/MAO-[(EBI)ZrCl.sub.2], FIG. 2. The optimum time for polymerisation is again 15 min with the activity reaching 2406 kg.sub.PE/molz.sub.r/h/bar, 2.5 times higher than AMO-LDH at the same time. The curves are expected to level off completely as the diffusion control limit is reached.

(35) TABLE-US-00003 TABLE 3 Polymerisation data demonstrating the molecular weights (M.sub.w) and polydispersities (M.sub.w/M.sub.n) with Time varying from 0 to 120 minutes at 70? C. using silica@AMO-LDH/MAO-[(EBI)ZrCl.sub.2] Time (minutes) M.sub.w (g/mol) M.sub.w/M.sub.n 15 143088 4.12 30 137341 4.69 60 152496 4.99 120 147827 4.57

(36) TABLE-US-00004 TABLE 4 Polymerisation data demonstrating the molecular weights (M.sub.w) and polydispersities (M.sub.w/M.sub.n) with Time varying from 0 to 120 minutes at 70? C. using AMO-LDH/MAO-[(EBI)ZrCl.sub.2] Time (minutes) M.sub.w (g/mol) M.sub.w/M.sub.n 5 175468 4.15 15 194344 4.51 30 171280 4.30 60 150138 4.70 120 144305 5.82

(37) After 15 minutes of polymerisation (a) small spherical particles within the range 0.6-1.4 ?m are present within the sample. These particles appear to be aggregated together. Strings of growing polymer can be seen. After 1 h, the polymer size and morphology is still not uniform (2.8-3.4 ?m).

(38) FIG. 3 SEM images of polymer produced using the silica@AMO-LDH metallocene catalyst support complex after (a) 15 min and (b) 1 h. (c) Silica@LDH.

(39) In FIG. 3, the silica@AMO-LDH metallocene catalyst is silica@AMO-LDH/MAO-[(EBI)ZrCl.sub.2]. Image (a) shows the polyethylene particles produced after 15 minutes. Spherical polymer particles 1.3-1.9 ?m are present in the sample along with larger 6.3-10.3 ?m particles. The polymer has mirrored the catalyst support morphology to a certain extent; the original silica@AMO-LDH is shown in image (c). After 1 h (b) the individual polymer particles have grown and aggregated together forming a very large polymer particle of 27 ?m.

(40) FIG. 4. XRD patterns of SiO.sub.2@LDH microspheres prepared according to example 1 (a) conventional water washing (b) acetone washing.

(41) FIG. 5. TEM image of SiO.sub.2@LDH microspheres with different morphology (a) solid (example 1), (b) yolk-shell (example 1 at 40? C.) and (c) hollow (example 1 at pH 11).

(42) FIG. 6 TEM image of SiO.sub.2@AMO LDH microspheres according to examples 5 and 7 at pH=10 and room temperature (a) Mg:Al=3:1 (b) Mg:Al:Fe=3:0.9:0.1.

(43) FIG. 7 TEM image of SiO.sub.2@AMO-LDH with Mg:Ni:Al=2.7:0.3:1 microspheres with different morphology according to example 6 (a) pH=10 and room temperature (b) pH=10 and 40? C. (c) pH=11 and 40? C.

(44) Further, non-limiting, examples of SiO.sub.2@AMO-LDHs suitable for use in the present invention are detailed below:

Example 1

(45) Silica spheres (100 mg, 550 nm) were dispersed in deionised water (20 mL) using ultrasound treatment. After 30 min., Na.sub.2CO.sub.3 (0.96 mmol) was added to the solution and a further 5 min of sonication was carried out to form solution A. Next an aqueous solution (19.2 mL) containing Mg(NO.sub.3).sub.2.6H.sub.2O (0.96 mmol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.48 mmol) was added at a rate of 60 mL/h to solution A under vigorous stirring at room temperature. The pH of the reaction solution was controlled to be 10 with the addition of 1 M NaOH. The obtained solid was collected with centrifugation at 4000 rpm for 5 min and then re-dispersed in deionised water (40 mL) and stirred for 1 h. The collection and re-dispersion were repeated twice. Afterward, the solid was washed with acetone (40 mL) and then re-dispersed in acetone (40 mL) and left to stir overnight. The solid was then dried under vacuum.

(46) The SiO.sub.2@LDH obtained in this Example, before the treatment with acetone, has the formula:
(SiO.sub.2).sub.0.04@{[Mg.sub.0.75Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.1.34(H.sub.2O)}.sub.0.05

(47) The SiO.sub.2@AMO-LDH, obtained after acetone treatment, has the formula:
(SiO.sub.2).sub.0.04@{[Mg.sub.0.75Al.sub.0.25(OH).sub.2](CO.sub.3).sub.0.125.0.29(H.sub.2O).0.15(acetone)}.sub.0.05

(48) Yolk shell particles were obtained by carrying out the addition of the aqueous solution containing the Mg(NO.sub.3).sub.2.6H.sub.2O and Al(NO.sub.3).sub.3.9H.sub.2O at 40? C. and pH10.

(49) Hollow shell particles were obtained by carrying out the addition of the aqueous solution containing Mg(NO.sub.3).sub.2.6H.sub.2O and Al(NO.sub.3).sub.3.9H.sub.2O at room temperature but at pH11.

(50) Surface Area Analysis

(51) The solid SiO.sub.2@LDH, the yolk shell SiO.sub.2@LDH and the hollow shell SiO.sub.2@LDH prepared as described above but without acetone treatment were subjected to Brunauer-Emmett-Teller (BET) surface area analysis.

(52) The N.sub.2 BET surface areas of the products were:

(53) TABLE-US-00005 BET surface area (m.sup.2g.sup.?1) Solid (i.e. core-shell) SiO.sub.2@LDH 107 Yolk-shell SiO.sub.2@LDH 118 Hollow-shell SiO.sub.2@LDH 177

(54) The BET surface areas reported above may be favourably compared to those of SiO.sub.2@LDHs prepared according to (A) Shao et al. Chem. Mater. 2012, 24, pages 1192-1197 and to those of SiO.sub.2@LDHs prepared according to (B) Chen et al. J. Mater. Chem. A, 1, 3877-3880.

(55) TABLE-US-00006 BET surface area (m.sup.2g.sup.?1) (A) SiO.sub.2 microspheres pre-treated with Al(OOH). Product SiO.sub.2@NiAl LDH. Solid (i.e. core-shell) SiO.sub.2 microspheres 42.3 Yolk-shell SiO.sub.2@LDH microspheres 68 Hollow-shell SiO.sub.2@LDH microspheres 124 (B) SiO.sub.2 microspheres - no pre-treatment - ammonia method. Product SiO.sub.2@LDH. Solid (i.e. core-shell) SiO.sub.2@LDH microspheres 61

(56) Core-shell SiO.sub.2@LDHs were prepared according to the procedures described in Example 1 and in the Examples 2 and 3 below having different thicknesses of LDH layer. The ratio of Mg/Al was varied to control the thickness of the LDH layer. A Mg:Al ratio of 1:1 was found to give an LDH layer of thickness 65 nm, a ratio of 2:1 was found to give an LDH layer of thickness 110 nm and a layer of thickness of 160 nm was obtained using a Mg:Al ratio of 3:1. TEM images are shown in FIG. 15. Core-shell SiO.sub.2@LDHs were also prepared according to the procedure described in Example 1 above using different sized SiO.sub.2 microspheres, 300 nm, 550 nm and 800 nm. TEM images are shown in FIG. 16. TEM images of the SiO.sub.2@LDHs produced with different morphology (a) solid (Example 1), (b) yolk shell (Example 1 at 40? C.) and (c) hollow (Example 1 at pH11), as described above, are shown in FIG. 17.

Example 2

(57) In order to obtain a 1:1 Mg:Al LDH, the procedure described above in Example 1 was repeated with the exception that an aqueous solution (19.2 mL) containing Mg(NO.sub.3).sub.2.6H.sub.2O (0.72 mmol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.72 mmol) was added at a rate of 60 mL/h to solution A under vigorous stirring.

Example 3

(58) In order to obtain a 3:1 Mg:Al LDH, the procedure described above in Example 1 was repeated with the exception that an aqueous solution (19.2 mL) containing Mg(NO.sub.3).sub.2.6H.sub.2O (1.08 mmol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.36 mmol) was added at a rate of 60 mL/h to solution A under vigorous stirring. The XRD patterns of the SiO.sub.2@LDH samples prepared with Mg:Al ratios of 1:1 (Example 2) and 3:1 (Example 3) are shown in FIG. 12.

Example 4

(59) The silica@LDH particles were synthesised via the coprecipation method. Silica spheres (100 mg, 550 nm) were dispersed in deionised water (20 mL) using ultrasound treatment. After 30 min, the anion salt (0.96 mmol), Na.sub.2CO.sub.3, was added to the solution containing ammonia (0.8 mL, 35%) and a further 5 min of sonication was carried out to form solution A. Next an aqueous solution (19.2 mL) containing Mg(NO.sub.3).sub.2.6H.sub.2O) (0.96 mmol) and Al(NO.sub.3).sub.3.9H.sub.2O (0.48 mmol) was added at a rate of 60 mL/h to solution A under vigorous stirring. The obtained solid was collected with centrifugation at 4000 rpm for 5 min and then re-dispersed in deionised water (40 mL) and stirred for 1 h. The collection and re-dispersion were repeated twice. Afterward, the solid was washed with acetone (40 mL) and then re-dispersed in acetone (40 mL) and left to stir overnight. The solid was then dried under vacuum. The suspension was then dried under vacuum for materials characterisation.

(60) The features disclosed in the foregoing description, in the claims as well as in the accompanying drawings, may both separately and in any combination thereof be material for realizing the invention in diverse forms thereof.

Example 5

(61) In order to obtain Silica@AMO-LDHs in Mg:Al=3:1. Synthesise the Silica@LDH particles by using the co-precipitation method, disperse silica spheres (100 mg) in the deionised water (20 mL) by using ultrasound treatment for 30 min, add the anion salt Na.sub.2CO.sub.3 (0.96 mmol) in the solution and further treat by ultrasound for 5 min, the finally solution named A. Then add an aqueous solution (19.2 mL) containing (1.08 mmol) Mg.sup.2+ and (0.36 mmol) Al.sup.3+ in the solution A at the rate of 60 mL/h with vigorous stirring. The pH of the reaction solution is controlled with the addition of 1 M NaOH by an autotitrator. And the morphology of Silica@LDH is controlled by pH and temperature. The obtained solid is collected with centrifugation at 5000 rpm for 5 min and then re-dispersed in deionised water (40 mL) and stir for 1 h, the washing need repeated twice. Before final isolation, the solid is washed with acetone (40 mL) and left to stir over night, and the suspension is then dried under vacuum

Example 6

(62) In order to obtain Silica@AMO-LDHs in Mg:Ni:Al=2.7:0.3:1. The Silica@LDH particles will be synthesized by using the co-precipitation method, disperse silica spheres (100 mg) in the deionised water (20 mL) by using ultrasound treatment for 30 min, add the anion salt Na.sub.2CO.sub.3 (0.96 mmol) in the solution and further treat by ultrasound for 5 min, the finally solution named A. Then add an aqueous solution (19.2 mL) containing (0.972 mmol) Mg.sup.2+, (0.108 mmol) Ni.sup.2+ and (0.36 mmol) Al.sup.3+ in the solution A at the rate of 60 mL/h with vigorous stirring. The pH of the reaction solution is controlled with the addition of 1 M NaOH by an autotitrator. As followed the morphology of Silica@LDH is controlled by pH and temperature. The obtained solid is collected with centrifugation at 5000 rpm for 5 min and then re-dispersed in deionised water (40 mL) and stir for 1 h, the washing need repeated twice. Before final isolation, the solid is washed with acetone (40 mL) and left to stir over night, and the suspension is then dried under vacuum.

Example 7

(63) In order to obtain Silica@AMO-LDHs in Mg:Al:Fe=3:0.9:0.1. The Silica@LDH particles synthesise using the co-precipitation method, disperse silica spheres (100 mg) in the deionised water (20 mL) by using ultrasound treatment for 30 min, add the anion salt Na.sub.2CO.sub.3 (0.96 mmol) in the solution and further treat by ultrasound for 5 min, the finally solution named A. Then add an aqueous solution (19.2 mL) containing (1.08 mmol) Mg.sup.2+, (0.324 mmol) Al.sup.3+ and (0.036 mmol) Fe.sup.3+ in the solution A at the rate of 60 mL/h with vigorous stirring. The pH of the reaction solution is controlled with the addition of 1 M NaOH by an autotitrator. As followed the morphology of Silica@LDH is controlled by pH and temperature. The obtained solid is collected with centrifugation at 5000 rpm for 5 min and then re-dispersed in deionised water (40 mL) and stir for 1 h, the washing need repeated twice. Before final isolation, the solid is washed with acetone (40 mL) and left to stir over night, and the suspension is then dried under vacuum

(64) The features disclosed in the foregoing description, in the claims and in the accompanying drawings may, both separately and in any combination thereof, be material for realizing the invention in diverse forms thereof.