WO2011012288A1

WO2011012288A1 - Method for producing a silico-alumino-phosphate

Info

Publication number: WO2011012288A1
Application number: PCT/EP2010/004594
Authority: WO
Inventors: Arno Tissler; Roderik Althoff; Silke Sauerbeck
Original assignee: Süd-Chemie AG
Priority date: 2009-07-27
Filing date: 2010-07-27
Publication date: 2011-02-03
Also published as: DE102009034850A1; CH703927B1

Abstract

The present invention relates to a method for producing a silico-alumino-phosphate, comprising the step of reacting a phosphorous source with a synthesis mixture having a template containing, aqueous-alkaline suspension of a SiO₂-powder and an aluminum hydroxide powder at increased temperature, a silico-alumino-phosphate that can be obtained according to the method and that is doped with one or more transition metal(s) if applicable, and an associated catalytic compound and an associated catalyst molded body.

Description

The present invention relates to a process for producing a silico-aluminophosphate, a silico-aluminophosphate obtainable by the process, a catalytic composition, and a shaped catalyst body containing the silico-alumino - Phosphate, optionally in transition metal-doped form, and the use of the silico-alumino-phosphate in transition metal-doped form as the active component in an exhaust gas purification catalyst.

Alumo-silicates (zeolites), alumo-phosphates (ALPOs) and silico-aluminophosphates (SAPOs) have been known in the art for some time as active components for refinery, petrochemical and chemical catalysts as well as for exhaust gas purification in both stationary and in-house known mobile applications. These groups are often only listed under the collective name Zeolithe.

Silico-aluminophosphates in the context of the present invention are crystalline substances with a spatial network structure, which consist of SiCVAIOVPO ^ tetrahedra, which are linked by common oxygen atoms to a regular three-dimensional network.

These structures contain cavities that are characteristic of each type of structure. The silico-aluminophosphates are classified into different structures according to their topology. The crystal framework contains open cavities in the form of channels and cages that are normally filled with water molecules and additional framework cations that can be exchanged. Each atom contains one phosphorus atom, so that the charges balance each other.

When silicon atoms substitute the phosphorus atoms, the silicon atoms form an excess negative charge which is compensated by cations. The interior of the pore system represents the catalytically active surface. The more silicon a silico-aluminophosphate contains, the denser the negative charge in its lattice and the more polar its internal surface. The pore size and structure, in addition to the parameters of manufacture, i. Use or type of template, pH, pressure, temperature, presence of seed crystals, determined by the P / Al / Si ratio, which accounts for most of the catalytic character of a silico-alumino-phosphate. The negative charge caused by the Si atoms is due to the incorporation of cations in the pores of the

Compensated zeolite material.

In a pure, non-ion-exchanged zeolite, these are usually H ⁺ ions, the Brönsted Induce acid properties, but also against other cations, such as metal cations in the lattice can be replaced. Accordingly, pure alumino-phosphates have no Brönsted acidity and no possibility to exchange H ⁺ ions for other ions.

The silico-aluminophosphates are mainly distinguished by the geometry of the cavities formed by the rigid network of SiCVAIOVPCv tetrahedra. The entrances to the cavities are formed by 8, 10 or 12 rings; the expert speaks here of narrow, medium and wide-pore structures. Certain aluminophosphates show a uniform structure structure, e.g. Example, a VFI or AET topology with linear channels, which connect with other topologies behind the pore openings larger cavities.

For technical applications, these materials are often modified with other components. In off-gas catalysis, it is usually modified with transition metals such as noble metals (for oxidation catalysis) or iron, copper, cobalt, etc. (for reduction catalysis). These then present as a powder materials are then either formed into extrudates (usually for stationary applications), with the aid of oxidic and organic binders

Extrudates / honeycomb catalysts or applied via the intermediate stage of a washcoat on ceramic or metallic honeycombs (for mobile applications).

In the prior art, production processes for silico-aluminophosphates are known, which are carried out with reactive components such as, for example, Al salts, SiO ₂ sols and phosphoric acid. Furthermore, processes are known in which silico-aluminophosphates which are loaded with transition metals, such as, for example, Fe and / or Cu as active components, are used in exhaust gas purification systems, in particular in so-called DeNOx systems. A disadvantage of the known production processes, inter alia, that this reactive and also very pure starting materials must be used. The purity of the silico-aluminophosphate prepared, ie the absence of other metal species, which can cause lattice defects and thus lower high-temperature stability, as well as undesirable catalytic effects (side reactions), is a prerequisite for a successful application of silico-alumino-phosphates in catalysis.

Furthermore, very reactive starting materials often do not lead to the desired structure, but to foreign phases, e.g. AFI or AIPO quartz which lower the catalytic activity of silico-aluminophosphates (see, for example, P. Concepciόn, JML Nieto, A. Mifsud, J. Perez-Pariente, Y. Xu, J. Maddox, JW Couves, J Chem. Soc. Faraday Trans. 86 (1990) 425; U. Lohse, R. Bertram, K.

Jancke, I. Kurzawaski, B. Parlitz, E. Löffler, E. Schreier, J. Chem. Soc. Faraday Trans. 91 (1995) 1163; MG Uytterhoeven, RA Schoonheydt, Micropor. Mater. 3 (1994) 265).

Also, lattice defects in the structure of the silico-aluminophosphates are often observed with reactive starting materials in the prior art. These lead to a low catalytic effect, and that only a few ions can be exchanged, as long as e.g. metal-exchanged silico-aluminophosphates are to be produced.

The object underlying the present invention was therefore to avoid the disadvantages of the prior art, i. to provide a high temperature stable, phase-pure silico-aluminophosphate cost-effectively without traces of foreign elements.

The object is achieved by a method for producing a silico-alumino-phosphate, comprising the steps of

a) providing a mixture comprising a template containing an aqueous-alkaline suspension of an aluminum hydroxide powder and a phosphorus source

b) adding SiO ₂

c) reacting the reaction mixture obtained in step b) at more than 100 0C.

The SiO ₂ can preferably be added in portions either as a slurry in water or as a solid (powder), so that a slow, homogeneous reaction takes place with the mixture presented. Although according to the invention also aluminum hydroxide (as a suspension or solid) to a

Mixture of SiO ₂ , the phosphorus source and the template containing aqueous suspension are given, but often arise with this less preferred procedure often mixed phases with contaminated products or other silico-alumino-phosphate structures, so that it requires further purification steps.

Surprisingly, it has been found that by using two inert starting materials for SiO ₂ and Al ₂ O ₃ instead of, for example, Si or Al sols as used in the prior art, namely an SiO ₂ powder and an aluminum hydroxide. Powder, a very pure high-temperature-stable silico-alumino-phosphate can be prepared directly, ie without recrystallization over other alumino-phosphate

Structures, arises and has a high exchange potential for metal cations. On- Due to the high (phase) purity of the silico-alumino-phosphate obtained by the process according to the invention, side reactions are largely suppressed when it is used in catalysis.

In the process according to the invention, the source of phosphorus can be any phosphorus source known to those skilled in the art for the preparation of silico-aluminophosphates, e.g. Phosphoric acid, organic phosphates, e.g. Triethyl phosphate, or phosphorus salts, e.g. Sodium metaphosphate, or aluminum phosphates. In this case, the phosphorus source has a good solubility in water, as well as in alkaline solutions or organic solvents.

According to a preferred embodiment of the process according to the invention, phosphoric acid is used as the phosphorus source, since it is particularly suitable as a medium-strength acid having a pKs1 value of 2.16 owing to its miscibility in water. In the process according to the invention, any template which is known to the person skilled in the art for the preparation of silico-alumino-phosphates can be used as the template. Preferably, a nitrogen-containing organic or inorganic salt. In this case, the template can be selected, containing e.g. Tetramethylammonium, tetraethylammonium,

Tetrapropylammonium or tetrabutylammonium ions, in particular -hydroxides, di-n-propylamine, tripropylamine, triethylamine, triethanolamine, piperidine, cyclohexylamine, 2-

Methylpyridine, N, N-dimethylbenzylamine, N, N-diethylethanolamine, dicyclohexyl-amine, N ₁ N-dimethylethanolamine, choline, N, N ^{'-Dimethylpiperazin,} 1, 4-diazabicyclo [2,2,2] octane, N-methyldiethanolamine, N-methylethanolamine , N-methylpiperidine, 3-methylpiperidine, N-methylcyclohexylamine, 3-methylpyridine, 4-methylpyridine, quinuclidine, N, N-dimethyl-1,4-diazabicyclo [2,2,2] octanion, di-n-butylamine, neopentylamine , Di-n-pentylamine, isopropylamine, t-butylamine, ethylenediamine, pyrrolidine and 2-imidazolidone.

However, according to a preferred embodiment of the process according to the invention, the template used is tetraethylammonium hydroxide (TEAOH), since this reacts in water to form strongly basic solutions. Since the formation of the silico-aluminophosphate takes place only under alkaline conditions, therefore, a pH greater than 7 is absolutely necessary. Due to the strong alkaline effect of

Tetraethylammonium hydroxide, can therefore be dispensed with a further addition of hydroxides, for example in the form of alkaline inorganic salts, etc. This makes the process for producing silico-aluminophosphates even cheaper and more efficient, since no further purification step is required to remove unwanted impurities such as Na ⁺ - or K ⁺ ions (by the addition of NaOH or KOH, etc.).

Due to the strong alkaline effect of tetraethylammonium hydroxide, only the use of phosphoric acid as a source of phosphorus is possible. If a template is used which shows only weakly alkaline action, then the pH of the aqueous suspension decreases and conversion to the silico-aluminophosphates according to the invention is no longer possible, since this takes place in an alkaline medium.

In the method according to the invention, a SiO ₂ powder is used as SiO ₂ source. In this case, it is possible to use any SiO ₂ powder which has a purity of> 97% to 99.9%, preferably at least 99%. In this case, a high-purity SiO ₂ is preferably used, which is obtained as a waste product in chip production (Si wafer). By being very fine, the Si powder is already oxidized on contact with atmospheric oxygen and thus accumulates in a purity of 99.9%. Since extreme demands are placed on the purity, with regard to the number of foreign atoms in the Si lattice and the quality, with regard to the number of lattice defects for the production of Si wafers, no further treatment of the SiO ₂ powder is necessary before use, which allows a direct insertion into the reaction mixture. As a result, the production costs for the silico-aluminophosphate according to the invention can be further reduced.

In a preferred embodiment of the method according to the invention, the SiO ₂ powder has an average particle size distribution d ₁₀ O of <0.6 μm, more preferably of <0.5 μm, in particular of <0.4 μm. It should be noted that the particle size distribution due to the solution behavior in aqueous solution has a direct influence on the formation of undesirable structures. The use of SiO ₂ powder with a particle size distribution of> 0.6 microns leads due to a different solution behavior to form undesirable structures in the synthesis, which must be separated again in further steps.

To determine the average particle size distribution of the SiO ₂ powder, a Malvern Mastersizer (obtained from Malvern Instruments GmbH, Germany) was used. For the measurement, the SiO ₂ powder was suspended in analytically pure n-hexane. The particle size of the SiO ₂ powder was determined by conventional analysis methods such as XRD.

According to an advantageous development of the method according to the invention, the SiO ₂ powder has a purity of> 99.99%. By using a very high purity SiO ₂ powder, a silico-aluminophosphate is compared to the one used a high purity (about 97% to 99%) SiO ₂ again enhanced high temperature stability and a substantial absence of undesirable catalytic

Side effects are obtained because the presence of other metal species that can cause lattice defects is diminished. An example of a preferred SiO ₂ powder meeting this purity criterion is Elkem Submicron Silica 995, available from Elkem Materials, Norway. In this preferred embodiment, however, any other SiO ₂ powder can be used, which are known in the art, as long as they meet the above-mentioned purity criterion.

In a preferred embodiment of the method according to the invention, the SiO ₂ powder has a BET surface area in a range from 35 m ² / g to 70 m ² / g. More preferably, the SiO ₂ powder has a BET surface area in a range of 40 m ² / g to 65 m ² / g, more preferably in a range of 45 m ² / g to 55 m ² / g. The BET surface area is of importance for the purity of the resulting silico-aluminophosphates, since only a large BET surface area of more than 35 m ² / g ensures sufficient reactivity of the SiO ₂ powder. It is of particular importance that the formation of foreign phases and lattice defects by the use of SiO ₂ can be prevented with certain reactivity, whereby a high catalytic selectivity and effectiveness is ensured. However, it should be noted that the BET surface area can not be increased arbitrarily, since at a BET surface area greater than 70 m ² / g, the reactivity of the SiO ₂ powder is so great that it leads to the formation of unwanted by-products.

The BET surface area of the SiO ₂ powder is determined by adsorption of nitrogen in accordance with DIN 66131 and DIN 66132 (DIN ISO 9277: 2003-05, determination of the specific surface area of solids by gas adsorption by the BET method). A publication of the BET method can be found, for example, in J. Am. Chem. Soc. 60, 309 (1938).

According to a further advantageous embodiment of the method according to the invention, the aluminum hydroxide powder has an average particle size of 5 .mu.m to 200 .mu.m, more preferably from 5 .mu.m to 150 .mu.m and in particular from 5 .mu.m to 100 .mu.m. For smaller particle sizes than 5 .mu.m, the aluminum hydroxide dissolves too quickly and there is the possibility of foreign phase formation (which are preferably kinetically formed), too large particles of more than 200 .mu.m may not dissolve or deteriorate at all and also lead to foreign phase formation. Especially in combination with the preferably used SiO ₂ powder having the above-defined BET surface area, the reactivity of the reaction mixture is increased to such an extent that the formation of by-products is largely prevented, and silico-aluminophosphates predominantly obtained in the desired structure become. According to a preferred embodiment of the method according to the invention, the aluminum hydroxide powder is hydrargillite powder. In this case, for example, hydrargillite powder can be used as aluminum hydroxide SH10, which is available from Aluminum Oxid Stade GmbH, Germany. In a particularly preferred embodiment, the hydrazillite powder has an average particle size of from 5 .mu.m to 100 .mu.m, whereby the course of the reaction can be controlled even better, since the reactivity does not lead to the formation of many by-products.

In further preferred embodiments of the inventive method, the step of reacting at a temperature in the range of 100 ⁰ C to 250 ⁰ C is performed, more preferably at a temperature of 150 ⁰ C to 200 ⁰ C and in particular at a temperature of 170 ⁰ C bis 190 ⁰ C. the choice of temperature for the inventive step of reacting the reaction mixture is for a successful course of the synthesis of great importance since a too strong heating should be avoided as tetraethylammonium hydroxide, which is preferably used as a template in case of strong heating Over 250 ⁰ C is decomposed to triethylamine and methanol, whereby its structure-directing function and effect is lost and thus no more silico-alumino-phosphates in the desired structure can arise. Next moderate temperatures up to 250 ⁰ C are also important for the course of the reaction, since the formation of the silico-alumino- phosphate is to run slow and controlled so that both side reactions to other structures can be largely prevented, and lattice defects in the crystallization of the products avoided be, whereby the high temperature stability of the silico-alumino-phosphate is even higher. Preferably, the preparation of the silico-alumino-phosphate is carried out under pressure. In this case, the reaction is usually carried out in an autoclave. It uses pressures up to 300 bar, depending on the desired structure.

According to a further embodiment of the method according to the invention, the step of reacting is carried out for a period in the range of 50 hours to 100 hours, more preferably in the range of 60 hours to 90 hours, in particular in the range of 65 hours to 80 hours. Since only a slow reaction over a period of over 50 hours ensures the desired purity of the products, the reaction time is high. Furthermore, the method according to the invention comprises the steps of filtering, washing and drying the resulting silico-alumino-phosphate in order to remove any starting materials still present.

The steps of filtering, washing and drying according to this preferred embodiment of the process according to the invention can be carried out in a manner known per se and are carried out under mild conditions (250 ^° C. max.).

In further preferred embodiments of the process according to the invention, after the silico-aluminophosphate has been dried, the process further comprises a ion exchange of the silico-aluminophosphate with one or more transition metals. Since cations are incorporated into silico-alumino-phosphates due to the excess negative charges for charge compensation, so the catalytic effect can be modified by targeted ion exchange with metals. The silico-aluminophosphate according to the invention can accordingly be metal-exchanged with one or more transition metals by means of an aqueous ion exchange, an aqueous impregnation, an incipient wetness process or a solid-state ion exchange. These methods of ion exchange with metals are known in the art. It is preferred to carry out the ion exchange of the transition metal by means of one or more transition metal compound (s) by aqueous ion exchange.

According to a particularly advantageous embodiment of the method according to the invention, the at least one transition metal is a noble metal or iron or copper or a combination of iron and copper, wherein iron and / or copper for the use of the metal-exchanged silico-aluminophosphate as catalyst in an SCR Reaction are preferred and copper is preferably used in oxidation reactions. The transition metal-containing silico-alumino-phosphate according to the invention is suitable on account of its high phase purity and the low proportion of lattice defects, its temperature stability, its possible high proportion of exchanged transition metal and its high ammonia storage capacity

as an SCR catalyst, especially in mobile diesel applications. When used as a diesel SCR catalyst can be further exploited the advantage that the zeolitic

At the same time serves as a cold start trap for unburned hydrocarbons, which at low Riger temperatures where the oxidation effect of the catalyst is not high enough, are adsorbed, and then desorbed at higher operating temperatures, ie with optimum oxidation efficiency of the catalyst.

Cold start hydrocarbon emissions are currently responsible for approximately 80% of hydrocarbons emitted by internal combustion engines. Numerous methods have already been proposed to reduce these emissions. The methods include the use of materials to adsorb the hydrocarbons when the catalysts loaded on the vehicles are cold and inactive, and then release those hydrocarbons again at higher temperatures when the catalyst has reached a sufficient operating temperature. so that he can convert the hydrocarbons into non-polluting products. This can now be circumvented by using a silico-aluminophosphate according to the invention, since these are efficient catalysts even at low temperatures.

According to a very particularly preferred embodiment of the silico-aluminophosphate according to the invention, the silico-aluminophosphate has an Si / (Al + P) molar ratio of from 0.01 to 0.5: 1, more preferably from 0.02 to 0, 1: 1 up. Silico-aluminophosphates of the stated molar ratio have a higher metal exchange capacity, which can increase their catalytic performance. If the silico-aluminophosphate is in transition metal-modified form, it preferably has a transition metal content, calculated as oxide, of from 1% to 10%, preferably from 2% to 6% by weight. %, if the proportion of transition metal is too low, the advantages of the silico-aluminophosphate according to the invention, such as the good high-temperature stability, in addition to the low working temperature suffer.

According to the invention, a silico-aluminophosphate optionally doped with one or more transition metals is also provided, which is obtainable by means of the process according to the invention. This is highly phase-pure with a phase purity greater than 99%, preferably greater than 99.5%, most preferably greater than 99.9%, as compared to silico-alumino-phosphate of the prior art, due to the preferred reaction regime. the presence of other phases or structures can not be detected in the silico-aluminophosphate obtainable according to the invention by means of customary analysis methods such as XRD.

Furthermore, according to the invention, a catalytic composition is provided which contains the transition metal-containing silico-alumino-phosphate according to the invention. In a preferred

Embodiment, the catalytic composition according to the invention contains the transition metal preferably, in the range of 5 to 95% by weight, more preferably in the range of 20 to 80% by weight, of silico-aluminophosphate. The catalytic composition may further contain other metal oxides, binders, promoters, stabilizers and / or fillers known to those skilled in the art. The transition metal-containing silico-alumino-phosphate according to the invention or the catalytic composition containing the transition-metal-containing silico-aluminophosphate according to the invention can be processed into a washcoat which is suitable for coating catalyst supports or shaped catalyst bodies. Preferably, the washcoat comprises 5 wt% to 70 wt%, more preferably 10 wt% to 50 wt%, most preferably 15 wt% to 50 wt% of the silico-aluminophosphate of the present invention , The application over a washcoat is advantageous, since so a uniform coating of the catalyst carrier takes place.

The transition metal-containing silico-alumino-phosphate according to the invention or the catalytic composition containing the transition-metal-containing silico-aluminophosphate according to the invention can also be extruded into a catalyst in any extruded form, preferably in honeycomb form, such as commonly used in US Pat automotive applications is used, processed.

The invention thus also relates to a shaped catalyst body comprising the transition metal-containing silico-aluminophosphate according to the invention or the catalytic composition according to the invention.

The invention will be explained in more detail below by way of non-limiting examples.

Example 1 (according to the invention)

The following example illustrates the preparation of SAPO-34, a silico-aluminophosphate, by the process of the present invention.

32.50 parts by weight of deionized water and 13.93 parts by weight of silica (Elkem Submicron Silica 995, 99.997% pure amorphous silica, average particle size dioo <4 μm, BET surface area = 50 m ² / g, from Elkem Materials, Norway, available) were mixed. Further, a mixture of 89.17 parts by weight of deionized water and 90.70 parts by weight of hydrargillite (aluminum hydroxide SH10, available from Aluminum Oxide Stade GmbH, Germany) was prepared containing 132.29 parts by weight phosphoric acid (85%) and 241. 41 parts by weight TEAOH (Tetraethylammonium hydroxide) (35% in water). The silica / water mixture prepared in the manner described above was added to the resultant hydrargillite mixture to obtain a synthesis gel mixture having the following molar composition: Al ₂ O ₃ : P ₂ O ₅ : 0.4 SiO ₂ : 1 TEAOH : 35 H ₂ O

The synthesis gel mixture having the above composition was placed in a

Stainless steel autoclave transferred. The autoclave was stirred and heated to 180 ⁰ C, this temperature was maintained for 72 hours. After cooling, the product obtained was filtered off, washed with deionized water and dried in an oven at 100 ⁰ C. An X-ray diffraction pattern of the resulting product showed that the product was pure SAPO-34. The elemental analysis showed a composition of 3.9% Si, 22.0% Al and 20.1% P, which corresponds to a stoichiometry of Si _o, o ₇₇ Al _o , ₅ i ₄ Po, ₄₀₉ . According to an SEM (Scanning Electron Microscope) analysis of the product, its crystal size was in the range of 0.5 to 1 μm.

Example 2 (comparative example)

The following comparative example illustrates the preparation of SAPO-34 by a conventional method using Al ₂ O ₃ in the form of pseudoboehmite and silica sol as starting materials.

79.97 parts by weight of deionized water and 65.25 parts by weight of pseudoboehmite (Pural SB, 74% Al ₂ O ₃ , BET surface area = 257 m ² / g, available from Sasol Limited, South Africa) were mixed. 124.92 parts by weight of phosphoric acid (85%) and 201, 13 parts by weight of TEAOH (35% in water) and then 28.72 parts by weight of silica sol (Köstrosol 1030, 30%) were added to the resulting mixture.

Silica, available from CWK Chemiewerk Bad Köstritz, Germany) to give a synthesis gel mixture having the following molar composition:

Al ₂ O ₃ : P ₂ O ₅ : 0.4 SiO ₂ : 1 TEAOH: 35 H ₂ O

The synthesis gel mixture having the above composition was placed in a

Stainless steel autoclave transferred. The autoclave was stirred and heated to 180 ⁰ C, this temperature was held for 320 hours. After cooling, the product obtained was filtered off, washed with deionized water and dried in an oven at 100 ⁰ C. An X-ray diffractogram of the resulting product showed that the product was pure SAPO-34. The

Elemental analysis showed a composition of 3.8% Si, 20.4% Al and 18.1% P, giving a Stoichiometry of Si _o , o ₉ oAl _{o, 482} Po _{, 428} corresponds. According to an SEM (Scanning Electron Microscope) analysis of the product, its crystal size was in the range of 1 to 3 μm.

Example 3 (Comparative Example) The following comparative example corresponds to the preparation of SAPO-34 according to Example 2 above, but instead of pseudo-boehmite, hydrargillite (aluminum hydroxide SH 10) was used.

A synthesis gel mixture having the following molar composition was obtained:

Al ₂ O ₃ : P ₂ O ₅ : 0.4 SiO ₂ : 1 TEAOH: 35 H ₂ O

The synthesis gel mixture having the above composition was placed in a

Stainless steel autoclave transferred. The autoclave was stirred and heated to 180 ⁰ C, this temperature was maintained for 32 hours. After cooling, the product obtained was filtered off, washed with deionized water and dried in an oven at 100 ⁰ C. An X-ray diffractogram of the resulting product showed that the product was pure SAPO-34. The elemental analysis showed a composition of 3.6% Si, 21, 0% AI and 17.6% P, which corresponds to a stoichiometry of Si _o, o ₈₅ Alo _{, 498} Po _{, 4} i ₇ . According to an SEM (Scanning Electron Microscope) analysis of the product, its crystal size was in the range of 0.5 to 1 μm.

Claims

claims

A process for producing a silico-aluminophosphate, comprising the steps of a) providing a mixture comprising a template-containing aqueous-alkaline suspension of an aluminum hydroxide powder and a phosphorus source

b) adding SiO ₂

c) reacting the reaction mixture obtained in step b) at more than 100 0C.

2. The method of claim 1, wherein the phosphorus source is phosphoric acid.

3. The method according to claim 1 or 2, wherein as a template

Tetraethylammonium hydroxide (TEAOH) is used.

4. The method of claim 1 or 2, wherein the SiO ₂ powder has an average particle size distribution dioo of <0.6 microns.

5. The method according to any one of claims 1 to 3, wherein the SiO ₂ powder has a purity of> 99.99%.

6. The method according to any one of claims 1 to 4, wherein the SiO ₂ powder has a BET surface area in a range of 35 m ² / g to 70 m ² / g.

7. The method according to any one of claims 1 to 5, wherein the aluminum hydroxide powder has an average particle size of 5 microns to 200 microns.

8. The method according to any one of claims 1 to 6, wherein the aluminum hydroxide powder is a hydrargillite powder.

9. The method according to any one of claims 1 to 7, characterized in that the step of reacting at a temperature in the range of 100 ⁰ C to 250 ⁰ C is performed.

10. The method according to any one of claims 1 to 8, characterized in that the

Step of implementation is carried out for a period in the range of 50 hours to 100 hours.

11. The method according to any one of claims 1 to 9, characterized in that it further comprises steps of filtering, washing and drying of the obtained silico

Aluminophosphate.

12. The method according to claim 10, characterized in that the method further comprises a step of ion exchange of the silico-alumino-phosphate with one or more transition metal (s) after drying the obtained silico-alumino-phosphate.

13. The method according to claim 11, characterized in that the transition metal is a noble metal or iron or copper or a combination of iron and copper.

14. silico-aluminophosphate, obtainable by the process according to one of claims 1 to 10.

15. silico-aluminophosphate, obtainable by the process according to claim 11 or 12.

16. A catalytic composition containing a silico-alumino-phosphate according to claim 14.

17. Use of a silico-alumino-phosphate according to claim 14 as active component in an exhaust gas purification catalyst.