Composite material

Abstract

A composite material comprises a macroporous silicate-based material at least partially substituted with at least one microporous zeolite, wherein the microporous zeolite is functionalised with either copper, iron or both copper and iron, and wherein the composite material is in the form of particles. The composite material can be obtained using a method comprising the steps of: (i) providing a mixture comprising a silicate-containing scaffold having a macroporous structure, an aluminium source and an organic template; (ii) hydrothermally treating the mixture to form a microporous zeolite-containing structure substantially retaining the macroporous structure of the silicate-containing scaffold; (iii) incorporating copper, iron or both copper and iron into the zeolite. The silicate-containing scaffold can be a diatomaceous earth.

Claims

1. A method for the manufacture of a zeolite-containing structure, the method comprising: (i) providing a mixture comprising a silicate-containing scaffold having a macroporous structure, an aluminium source and an organic template; ii) hydrothermally treating the mixture to form a microporous zeolite-containing structure substantially retaining the macroporous structure of the silicate-containing scaffold; iii) incorporating copper, iron or both copper and iron into the zeolite.

2. The method of claim 1, wherein the zeolite has a ratio of silica to alumina of 10:1 to 50:1, and the silicate-containing scaffold is essentially the sole source of silicon atoms for the zeolite structure.

3. The method of claim 1, wherein the microporous zeolite comprises chabazite.

4. The method of claim 1, wherein the silicate-containing scaffold comprises one or more of porous glass, silica gel, and a diatomaceous earth, preferably wherein the silicate-containing scaffold comprises a diatomaceous earth.

5. The method of claim 1, wherein the silicate-containing scaffold comprises a cylindrical structure.

6. The method of claim 1, wherein the aluminium source comprises sodium aluminate.

7. The method of claim 1, wherein the organic template comprises a cage structure and/or a ring structure, preferably a tricyclo ring structure.

8. The method of claim 1, wherein the organic template comprises adamantyl trimethylammonium hydroxide and the microporous zeolite is chabazite.

9. The method of claim 1, wherein in step (i) the mixture has a pH greater than 7.

10. The method of claim 1, wherein step (ii) comprises heating the mixture in an autoclave at a temperature of from 140 to 180° C. for a period of from 1 to 7 days.

11. The method of claim 1, wherein the zeolite-containing structure is a composite material comprising a macroporous silicate-based material at least partially substituted with at least one microporous zeolite, wherein the microporous zeolite is functionalised with either copper, iron or both copper and iron, and wherein the composite material is in the form of particles.

Description

(1) The present disclosure will now be described in relation to the following non-limiting figures, in which:

(2) FIG. 1 shows a flowchart of a method according to the present invention;

(3) FIG. 2 shows XRD patterns of diatom (comparative), diatom-chabazite composite according to the invention and standard chabazite (comparative; from IZA data base);

(4) FIG. 3 shows SEM images of: (a) kieselguhr per se, and (b) and (c) composite materials according to the present invention;

(5) FIG. 4 a) and b) show EDX results of diatom (comparative); and diatom-chabazite composites according to the invention; and

(6) FIG. 5 shows a graph of N.sub.2-sorption isotherms of diatom and diatom-chabazite composites according to the invention.

(7) Referring to FIG. 1 there is shown a method for the manufacture of a zeolite-containing structure, the method comprising: (i) providing a mixture comprising a silicate-containing scaffold having a macroporous structure, an aluminium source and an organic template; (ii) hydrothermally treating the mixture to form a microporous zeolite-containing structure substantially retaining the macroporous structure of the silicate-containing scaffold; (iii) incorporating copper, iron or both copper and iron into the zeolite.

(8) The present disclosure will now be described in relation to the following non-limiting examples.

EXAMPLE 1

(9) Hydrothermal synthesis of a macroporous zeolite (chabazite)-containing composite material was carried out. To a solution of 0.20 g of NaOH in 26.2 g of H.sub.2O was added in succession, under agitation, 6.7 g of TMAda-OH (Adamantyltrimethylammonium hydroxide, 25% solution) and 0.51 g of sodium aluminate (20% Al.sub.2O.sub.3, 19.30% Na.sub.2O). This mixture was admixed with 2.60 g of kieselguhr (diatomaceous earth, EP Mineral “Celatom™”). The synthesis mixture had the molar composition: SiO.sub.2:0.05 Al.sub.2O.sub.3:0.20 TMAda-OH:0.10 Na.sub.2O:44 H.sub.2O

(10) The synthesis mixture was introduced into a stainless steel autoclaves with a Teflon® container (45 ml). The autoclave was then sealed and maintained for 4 days in a preheated oven at 160° C. The synthesis product was filtered off from the mother liquor, washed with distilled water and then dried at 75° C.

(11) Powder X-ray diffraction indicated that the zeolite chabazite had been formed (see FIG. 2). Scanning electron micrographs indicated that the shape of the kieselguhr had been maintained (see FIG. 3 (b)).

EXAMPLE 2

(12) Hydrothermal synthesis of a macroporous zeolite (chabazite)-containing composite material was carried out in a similar manner to Example 1. However, the autoclave was maintained for 4 days in a preheated oven at 160° C.

(13) To determine whether a pseudomorphic transformation had occurred, a sedimentation experiment was carried out. The material was dispersed in water and allowed to slowly settle. After 15 minutes, top, middle and bottom portions of the suspension were separated, filtered and analysed by powder X-ray diffraction. The results indicated that all three portions were the same, suggesting inherent bonding between the zeolite and the support. This was consistent with a pseudomorphic transformation. EDX experiments (see FIG. 4) also indicated a pseudomorphic transformation and a chabazite content of ˜28 wt. %.

(14) Scanning electron micrographs of the kieselguhr starting material (FIG. 3(a)) and the chabazite-containing composite material (FIGS. 3(b) and 3(c)) indicated that the shape of the kieselguhr had been maintained.

(15) .sup.27Al-MAS-NMR spectroscopy was carried out on the material (both as-synthesised and after calcining), and was compared with spectra for kieselguhr. The results indicated that no extra-framework aluminium species (penta- or hexa-coordinated) existed, confirming that in the bulk geometry the macroporosity of the kieselguhr starting material is maintained.

(16) The porosity characteristics of the material were investigated using N.sub.2-sorption, and the results are set out below:

(17) TABLE-US-00001 TABLE 1 Porosity characteristics. BET Total pore Micropore Macroporosity; surface volume volume surface area Sample area (m.sup.2/g).sup.a (cc/g).sup.a (cc/g).sup.a (m.sup.2/g).sup.b Kieselguhr 3 0.06 — 6.7 Example 1 441 0.27 0.19 3.2 Example 2 311 0.24 0.13 4.5 .sup.aN.sub.2-sorption measurement; .sup.bHg-Porosimetry measurement

(18) These values indicate approximately 58-61% of zeolite chabazite (CHA) is present in Example 2, which is consistent with the value of 55% determined by X-ray diffraction.

EXAMPLE 3

(19) Materials were prepared in a similar manner to Example 1 with differing levels of chabazite zeolite content ranging from 20 to 40%. Materials were NH.sub.4.sup.+ ion exchanged in a solution of NH.sub.4NO.sub.3, then filtered. The resulting materials were added to an aqueous solution of Cu(NO.sub.3).sub.2 with stirring. The slurry was filtered, then washed and dried. The procedure can be repeated to achieve the desired metal loading of 3 wt % (based on the zeolite content). The final product was calcined.

(20) The SCR catalytic activity of the materials was analysed. The following reaction conditions were used: NO: 500 ppm, NH.sub.3: 550 ppm, O.sub.2: 8.0% and H.sub.2O: 10.0%, V: 1000 L/g.Math.h (based on composite)

(21) Good levels of NO.sub.x and NH.sub.3 conversion were exhibited by the samples tested (see Table 2 below), and increased with increasing chabazite content. The catalytic effect of the samples was found to be particularly high at a temperature of around 400° C.

(22) TABLE-US-00002 TABLE 2 NOx Conversion 200° C. 300° C. 400° C. 500° C. 20% Chabazite/Kieselguhr 11 49 86 87 40% Chabazite/Kieselguhr 26 89 94 95

(23) A list of the tests carried out on Examples 1-3 are set out below, including tests not mentioned above, together with a summary of their conclusions:

(24) TABLE-US-00003 TABLE 3 Test method Conclusion X-ray diffraction (XRD) 28-67% of zeolite (CHA) content is achieved Sedimentation tests Pseudomorphic transformation SEM Shape is preserved with a zeolite content of 28-45% Cross-sectional SEM/EDX Si/Al = 10-43 (Pseudomorphic trans- formation) ICP analysis SiO.sub.2/Al.sub.2O.sub.3 = 17-20 (Bulk); SiO.sub.2/Al.sub.2O.sub.3 = 9-11 (Zeolite) N.sub.2-sorption (see FIG. 5) BET surface area: 433 m.sup.2g.sup.−1 Hg-Porosimetry Wide pore-size distribution NH.sub.3-SCR Cu-Chabazite/diatom is catalytically active Scaling-up Synthesis was scaled up to 1 L autoclave (ca. 100 g product per each run), successful under static condition

Table 3—Test Summary

(25) The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.

(26) For the avoidance of doubt, all documents acknowledged herein are incorporated herein by reference.