AU7532894A

AU7532894A - Process for the manufacture of a zeolite

Info

Publication number: AU7532894A
Application number: AU75328/94A
Authority: AU
Inventors: Philip Luc Buskens; Luc Roger Martens; Georges Marie Karel Mathys
Original assignee: Exxon Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 1993-07-23
Filing date: 1994-07-23
Publication date: 1995-02-20
Anticipated expiration: 2014-07-23
Also published as: AU678597B2; JPH09500860A; BR9407200A; CA2167279A1; PL312687A1; WO1995003249A1; EP0710216A1; CZ18596A3

Description

"Process for the Manufacture of a Zeolite" This invention relates to a process for the manufacture of a zeolite, especially to one suitable for use as a catalyst, to the zeolite produced by the process, and to organic reactions, especially oxidations of hydrocarbons, catalysed thereby.

Titanium-containing TS-1 and TS-2 are catalysts for the oxidation of hydrocarbons by hydrogen peroxide. A disadvantage of these catalysts is that because they have MFI and MEL structures, respectively, the rings of which are 10-membered, of diameter of the order of 0.5 nm, the entry of bulky feed molecules is restricted. For example, in the oxidation of paraffins, n-hexane reacts more readily than cyclohexane, and in general reactivity decreases with increasing branching and molecular weight. Further, the activity of the catalysts is high only for hydrogen peroxide; for organic hydroperoxides they are much less efficient.

More recently, a titanium-containing zeolite capable of efficiently catalysing the oxidation of higher paraffins using hydrogen peroxide has been synthesized. This catalyst, Ti-Beta zeolite, has a pore diameter of about 0.75 nm, and may be prepared as described in J. Chem. Soc. Chem. Comm. , 8, 1992, 589, using a procedure in which low concentrations of aluminium are present in the synthesis mixture. In our co-pending Application No^ 9307910, a process is described for the manufacture of Ti-Beta zeolite which comprises the preparation of a _^synthesis mixture containing a source of titanium (e.g. , tetraethyl orthotitanate, hereinafter TEOT) , a source of aluminium (e.g., aluminiu ^powder) , a source of silicon (e.g. colloidal silica) and an organic nitrogen-containing base (especially tetraethylammonium hydroxide, hereinafter TEAOH) , ageing the mixture, advantageously in the presence of H₂0₂, ^and hydrothermal treatment of the aged mixture.

The crystals formed during hydrothermal treatment are isolated, washed, dried, and calcined to remove organic material from the structure. Typical synthesis mixtures yielding Ti-Beta zeolite after hydrothermal treatment have an initial molar composition within the following ranges: sio₂(i); τio₂ (o.oooi to 0.2); AI₂O₃ (0.005 to 0.100)

H₂0 (10 to 100); and TEAOH (0.1 to 1)

Advantageously the Ti plus Si:Al molar ratio is within the range of from 10 to 200:1. Hydrogen peroxide is advantageously present in the synthesis mixture, although it may decompose before or during hydrothermal treatment, preferably in a proportion of 10 to 200 moles H₂0₂ per mole of TEOT when that is used as the source of titanium.

The catalyst formed in accordance with this procedure is active for oxidations using organic peroxides, especially hydroperoxides, thereby enabling the oxidation reaction to take place in a single organic phase, avoiding the aqueous phase also present when H₂0₂ is employed.

Although the procedure described above produces an active catalyst, yields in the absence of alkali metal cations are very low. Indeed, in an article by Camblor et al. Zeolites, 1991, 202 to 210, it is suggested that alkali metal cations are essential" for the formation of zeolite Beta itself, and there would have appeared to be no reason to distinguish Ti-Beta in this respect.

The present invention is based on the observation that if ethene is present in contact with a Ti-, V-, or Zr-Beta-forming synthesis mixture during the hydrothermal treatment the corresponding Ti-, V-, or Zr- Beta zeolite is obtained in good yields.

The present invention accordingly provides in a first aspect a process for the manufacture of a Ti-, V-, or Zr-Beta zeolite in which at least a part of a hydrothermal treatment of a Ti-, V-, or Zr-Beta forming synthesis mixture is carried out under an ethene- containing atmosphere at a pressure of at least 20 bar and advantageously under an ethene partial pressure of at least 5 bar.

In a second aspect, the invention provides a process for the manufacture of a Ti-, V-, or Zr-Beta zeolite in which at least a part of a hydrothermal treatment of a Ti-, V-, or Zr-Beta forming synthesis mixture is carried out in the presence of at least 0.1 mole of ethene per mole of tetraethylammonium cations. Advantageously, the mole ratio of ethene:tetraethylammonium is in the range 0.1 to 1:1.

For clarity, the remainder of the description will primarily relate to the aspect of the invention in which the product is Ti-Beta zeolite; it will be understood that mutatis mutandis the same procedure is used for the other products. It will be understood also that it is within the scope of the invention to make products containing mixtures of two or more of Ti, V, and Zr, as well as zeolites containing one or more of Ti, V, or Zr, and small proportions of other cations.

As a Ti-Beta forming synthesis mixture, there is typically used a mixture comprising a source of silicon, a source of titanium, a source of aluminium, water, and a source of tetraethylammonium cations.

The synthesis mixture is advantageously substantially free from alkali metal cations; by substantially free is meant the absence of more alkali metal than is inevitably present in commercial supplies of the essential components. If alkali metal ions, e.g., sodium or potassium ions, are present, they are advantageously present in a molar proportion of Si0₂:M⁺ of 1: at most 0.5. Advantageously, the synthesis mixture has a molar composition within the following ranges: Siθ₂(l); TiO₂(0.0001 to 0.2); Al₂O₃(0.0005 to 0.1); H₂O(10 to 100) and TEAOH (0.01 to 1) .

Advantageously, the Ti plus Si:Al molar ratio is within the range of from 50 to 200:1.

Preferred sources of the components are: for silicon, colloidal silica, advantageously a colloidal silica substantially free from alkali metal cations, or a tetraalkylammonium orthosilicate; for aluminium, aluminium powder; and for titanium, a hydrolysable titanium compound, e.g., TiOCl₄ , TiOCl₂ or a tetraalkyl orthotitanate, especially TEOT. For vanadium, a preferred source is vanadyl sulphate and, for zirconium, zirconyl sulphate. The tetraethyl ammonium cations are advantageously provided by TEAOH.

Advantageously, at least for titanium, hydrogen peroxide is present in the synthesis mixture. Advantageously, it is present in a proportion of from 10 to 200 moles per mole of TEOT, when that is the titanium source.

Advantageously, especially if it contains hydrogen peroxide, the synthesis mixture is aged between its formation and the hydrothermal treatment. Ageing may be carried out at room temperature or at elevated temperatures, for example at from 60 to 90°C, advantageously about 70°C, the ageing time being from 2 to 24 hours, depending inversely on the temperature. A preferred ageing treatment comprises initial room temperature ageing for from 12 to 18 hours, followed by elevated temperature ageing, e.g. , at 70°C, for from 2 to 4 hours.

Elevated temperature ageing also causes evaporation of water from the synthesis mixture, thereby producing a synthesis gel of a concentration advantageous for hydrothermal treatment. If desired, or required, the aged gel may be diluted before treatment, e.g. , with ethanol. If ethanol is added, it is advantageously present in the synthesis mixture subjected to hydro¬ thermal treatment in a proportion of at most 2 moles per mole of Sip₂.

The synthesis mixture, preferably aged, is advantageously subjected to hydrothermal treatment at a temperature within the range of from 120°C to 200°C, preferably from 130°C to 150°C, under the pressure regime as indicated above, advantageously for a time in the range of from 1 hour to 30 days, preferably from 6 days to 15 days, until crystals are formed. Hydrothermal treatment is advantageously effected in an autoclave.

While not wishing to be bound by any theory, it is believed that under the conditions prevailing under the hydrothermal treatment tetraethylammonium ions decompose and are unavailable to form a template effective in zeolite formation. By carrying out the treatment in the presence of ethene, a decomposition product, the equilibrium of the decomposition reaction is displaced and more tetraethylammonium ions remain available to act as templates.

In any event, by carrying out at least part of the hydrothermal treatment in the presence of ethene, a higher zeolite yield may be obtained or a lower proportion of tetraethylammonium ions may be included in the synthesis mixture. Advantageously, ethene is present in the reaction vessel from the commencement of the hydrothermal treatment.

Advantageously, the ethene partial pressure is at least 5 bar, preferably at least 20 bar, and most preferably at least 30 bar, for at least a part of the period of hydrothermal treatment. Also, advantageously, the total pressure is at least 30 bar, and preferably at least 40 bar. Advantageously, the ethene partial pressure is at least 80%, preferably at least 90%, of the total pressure.

After crystallization has taken place, the synthesis mixture is cooled, and the crystals are separated from the mother liquor, washed and dried.

To eliminate the organic base from the crystals, they are advantageously then heated to from 200 to 600°C, preferably about 550°C, in air, for from 1 to 72 hours, preferably about 12 hours.

The resulting calcined product may either be used as such or subjected to further treatment e.g., by acid, for example, HCl, or by bases e.g., ammonium or sodium ions. The product may be post-treated, as by steaming.

The Ti-Beta zeolite produced by the process of the invention may be highly crystalline and is characterized by an IR absorption at ± 960 cm^-1 and by an absorption band in Diffuse Reflectance Spectroscopy at the wave number 47,500 cm^-1. Diffuse Reflectance Spectroscopy is described in chapter 4 of "Characterisation of Heterogeneous Catalysts" by Chemical Industries, Volume 15, published by Manel Dekker Inc. of New York in 1984. The system used was as shown in Figure 3 of that chapter using a Cary 5 spectrometer.

The zeolite produced by the process of the invention is an active oxidation catalyst, especially for reactions employing a peroxide as oxidant, including organic peroxides, including hydroperoxides, as well as hydrogen peroxide. Compared to TS-1 and TS-2 catalysts, Ti-Beta zeolite is more effective in the oxidation of larger molecules, e.g., cycloparaffins and cycloolefins. The use of organic hydroperoxides avoids the two phase system necessarily associated with aqueous hydrogen peroxide.

The present invention accordingly also provides the use of the product of the process of the invention as a catalyst in the oxidation of an organic compound, especially in single phase oxidation by an organic peroxide. The catalyst of the invention is effective in oxidizing saturated hydrocarbons, e.g., paraffins and cycloparaffins, and the alkyl substituents in alkyl- aromatic hydrocarbons. In cycloparaffins, ring-opening and acid formation may take place, for example, in the oxidation of cyclohexane by tertiary butyl peroxide or H₂0₂ adipic acid is produced, and in the oxidation of cyclopentane glutaric acid is produced. The catalyst is also effective in the epoxidation of unsaturated hydrocarbons, e.g,. olefins and dienes, and the produc¬ tion of ether glycols, diols, the oxidation of alcohols, ketones or aldehydes to acids, and the hydroxylation of aromatic hydrocarbons.

In the oxidation process of the invention the oxidizing agent may be, for example, ozone, nitrous oxide, or preferably hydrogen peroxide or an organic peroxide including a hydroperoxide. Examples of suitable organic hydroperoxides include di-isopropyl benzene monohydroperoxide, cumene hydroperoxide, tert.butyl hydroperoxide, cyclohexyl hydroperoxide, ethylbenzene hydroperoxide, tert.amyl hydroperoxide, and tetralin hydroperoxide. Advantageously the compound to be oxidized is liquid or in the dense phase under the conditions used for the reaction. Advantageously, the reaction is carried out in the presence of a suitable solvent. The use of a tertiary butyl hydroperoxide is particularly beneficial since the tertiary butyl alcohol produced can readily be converted to the valuable isobutylene molecule.

The oxidation reaction may be carried out under batch conditions or in a fixed bed, and the use of the heterogeneous catalyst facilitates a continuous reaction in a monophase or biphase system. The catalyst is stable under the reaction conditions, and may be totally recovered and reused.

The following Examples illustrate the invention.

Example 1

Mixture A was prepared by adding dropwise 3.4 ml TEOT to 63.39 ml distilled H₂0. The mixture is cooled to 5°C, and 39 ml H₂0₂ (35% in H₂0) added. The resulting mixture was stirred for 2 hours at 5°C, resulting in a clear yellow-orange liquid.

Mixture B was prepared by adding 0.0312 g Al powder to 28.71 g of TEAOH (40% in H₂0) and dissolving it by heating to 90°C. After cooling 31 ml of distilled H₂0 were added. This mixture was cooled to 5°C and added to mixture A. The resulting mixture was stirred for another hour, then 12.23 g colloidal silica (Ludox HS40, 40% in water, stabilized by Na⁺) added. The synthesis mixture was stirred overnight at room temperature, followed by heating for 4 hours at 70°C. The resulting concentrated gel was diluted with 10 ml of ethanol, transferred to a stainless steel autoclave and made up to 100 ml with water. After 6 days at 125°C, the contents of the autoclave were a milk white suspension. This was centrifuged at 4000 rpm for 20 minutes to separate the solids. After drying at 60°C, the solids were calcined at 550°C in air for 12 hours to yield a Ti-Beta zeolite. More details of synthesis conditions for this and the remaining Examples are given in Table 1, while characteristics of the zeolites produced are given in Table 2.

In a Comparison Example 1, the procedure was as given above except that following addition of colloidal silica the synthesis mixture was immediately placed in the autoclave and heated for 7 days at 150°C. An amorphous product resulted.

Example 2

Mixture A was obtained by adding dropwise 0.5 ml TEOT to 63 ml distilled H₂0. This mixture was cooled to 5°C. Subsequently, 39 ml H₂0 (35% in H₂0) were added. The resulting mixture was stirred for 3 hours at 5°C, resulting in a clear yellow-orange liquid.

Mixture B was produced by adding 0.0312 g Al powder to 29.43 g of TEAOH (40% in H₂0) and dissolving it by heating at 90°C. Then, 31 ml of distilled H₂0 were added. This mixture was cooled to 5°C.

Solutions A and B were mixed and the resulting solution stirred for 1 hour at 5°C. Subsequently, 12.54 g of colloidal silica (Ludox AS40, 40% in H₂0, stabilized by NH₄ ⁺) were added. This mixture was stirred at room temperature for 18 hours and afterwards for another 2 hours at 70°C. The resulting gel was diluted with 10 ml ethanol and transferred to a stainless steel autoclave.

The autoclave was put in an oven and crystallization proceeded without agitation at 125°C for 6 days. After this time the autoclave was quickly cooled to room temperature and the solids separated from the liquid by centrifugation at 13,000 rpm. The organic template was then removed from the zeolite pores by calcination at 550°C in air for 12 hours.

Example 3

63 ml of H₂0 were mixed with 1.5 ml TEOT. The resulting mixture was cooled to 5°C. During this time a white suspension was formed. Subsequently, 39 ml of precooled H₂0₂ (35 wt% in H₂0) were added to this suspension. Upon addition the suspension took on a yellow colour. The resulting solution (mixture A) was stirred at 5°C for 3 hours.

0.0315 g of Al powder and 29.42 g of TEAOH (40% in H₂0) were put in a beaker, covered to prevent evaporation and heated at 80°C for 3 hours. After all the Al had dissolved, 32.31 g of distilled H₂0 were added. The resulting solution (Mixture B) was cooled to 5°C.

Mixtures A and B were combined, resulting in a pale yellow solution, which was kept stirred at 5°C for another hour. Afterwards, 12.53 g of colloidal silica (Ludox AS40, 40% in H₂0) were added. After 18 hours at room temperature, the colour of the slightly opaque solution had turned from pale yellow to white. Subsequently, the solution was kept at 70°C for 2 hours, after which it was allowed to cool to room temperature. The resulting gel was diluted with 10 ml of ethanol and transferred to an autoclave.

The autoclave was kept in an oven at 135°C in static conditions. After 6 days the crystals were separated 13,000 rpm. Finally, the solids obtained were dried overnight at 60°C. The organic template was removed from the zeolite pores by calcination at 550°C in air for 12 hours.

Example 4

Mixture A was obtained by adding dropwise 1.5 ml TEOT to 63 ml distilled H₂0. This mixture was cooled to 5°C. Subsequently, 39 ml H₂0₂ (35% in H₂0) were added. The resulting mixture was stirred for 3 hours at 5°C, resulting in a clear yellow-orange liquid.

Mixture B was produced by adding 0.910 g Al powder to 29.43 g of TEAOH (40% in H₂0) and dissolving it by heating at 90°C. Then, 31.08 g of distilled H₂0 were added. This mixture was cooled to 5°C.

Solutions A and B were mixed and the resulting solution stirred for 1 hour at 5°C. Subsequently, 12.57 g of colloidal silica (Ludox AS40, 40% in H₂0) were added. This mixture was stirred at room temperature for 16 hours and afterwards for another 2^• hours at 70°C. The resulting gel was diluted with 10 ml ethanol and transferred to a stainless steel autoclave.

The autoclave was put in an oven and the crystallization proceeded without agitation at 135°C for 10 days. After this time the autoclave was quickly cooled to room temperature and the solid material separated from the liquid by centrifugation at 13,000 rpm. After drying at 60°C, the organic template was removed from the zeolite pores by calcination at 550°C in air for 12 hours.

Example 5

12 ml of TEOT were mixed with 256 g of distilled H₂0. The resulting mixture was cooled to 5°C. During this time a white suspension formed. Subsequently, 103 ml of H₂0₂ (35 wt% in H₂0) were added to this suspension. Upon addition the suspension became yellow. The resulting solution was stirred for 3 hours at 5°C.

The aluminium source, 0.3859 g Al powder and 366 g of TEAOH (40% in H₂0) were combined in a beaker, covered to prevent evaporation, and heated at 80°C for 2 hours. After dissolution of aluminium, 183 ml of distilled water were added. The resulting solution was cooled to 5°C.

The two solutions were mixed, resulting in a pale yellow solution, which was stirred at 5°C for another hour. Afterwards, 61 g of colloidal silica (Aerosil, 200 m²/g) are added. After 18 hours at room temperature, the colour of the slightly opaque solution turned from pale yellow to white. Subsequently, the solution was kept at 70°C for l hours, during which it became yellow again. The solution was allowed to cool to room temperature. Before transferring the solution to a 1000 ml, ptfe-lined, stainless steel autoclave, 61 ml of ethanol were added. In previous Examples, the synthesis mixture had occupied at most two-thirds of the autoclave volume. In this Example, the synthesis mixture occupied about 95% of the volume. Gas phase analysis showed a high ethene content in the head-space.

The autoclave was kept at 140°C without agitation. After 11 days, pressure had risen to 50 bar. The crystals were separated from the mother liquor and washed by centrifugation at 13,000 rpm. After drying at 60°C, the organic template was removed from the zeolite pores by calcination at 550°C in air for 12 hours.

Example 6

The same procedure as described for Example 5 was used to compose the synthesis gel, but all reagent quantities were halved. The gel was transferred to a 1000 ml, ptfe-lined, stainless steel autoclave, and occupied about 50% of the volume. After closing the autoclave, ethene was introduced to give an ethene pressure of 7 bar. Subsequently, the autoclave was heated to 140°C. After 18 hours the pressure had risen to 14 bar. It was increased to 34 bar by introducing further ethene into the autoclave. Finally, after 3 days, the pressure which had risen to 36 bar was increased to 44 bar by adding further ethene. At this stage, the molar ratio of ethene:TEAOH was about 0.4:1. After a total of 13 days (when pressure was 50 bar) the autoclave was quickly cooled down. The crystals were separated from the mother liquor and washed by centrifugation at 13,000 rpm. After drying at 60°C, the organic template was removed from the zeolite pores by calcination at 550°C in air for 12 hours.

Comparison Example 2

The synthesis was as reported by M.A. Camblor et al, J. Chem. Soc. Chem. Comm. 8 (1992) 589.

33.95 g of TEAOH (40% in H₂0) were diluted with 40.00 g of distilled H₂0, to which 0.9 ml of TEOT were added. A white precipitate was formed. Subsequently, 9.99 g of colloidal silica (Aerosil 200 m²/g) were added. Finally, a solution of 0.32 g of Al (N0₃) ₃.9H 0 in 6.01 g distilled H₂0 was added.

The resulting gel was transferred to a ptfe-lined stainless steel autoclave and kept at 135°C for 10 days, while rotating at 50 rpm. The autoclave was quickly cooled down. The crystals were separated from the mother liquor and washed by centrifugation at 13,000 rpm. After drying at 60°C, the organic template was removed from the zeolite pores by calcination at 550°C in air for 12 hours. Comparison Example -3 Example 2 was repeated at a Si0₂/Al₂0₃ mole ratio of 101:1 and 1.49 moles TEAOH per mole of Si0₂. No solids were obtained.

Table 1 Synthesis Conditions

gel composition (molar ratios) crystallization conditions

Example Siθ₂/Tiθ₂ Si0₂/Al₂0₃ OH^~/Si0₂ EtOH/Siθ₂ H₂0/Si0₂ ^a evap. time head-space temp time No. at 70°C (h) (%) (°C) (days)

Comp. 1 5 143 0.94 2 95 0 40 150 7

.1 5 147 0.95 2 98 4 33 125 6

2 35 145 0.96 2 98 2 50 125 6

3 12 143 0.96 2 99(42) 2 50 135 10

4 12 50 0.96 2 100(25) 2 50 135 10

5 18 142 0.98 1 40(25) 2.5 5 140 11

6 18 142 0.98 1 40(25) 2.5 50 140 13

Comp. 2 38 385 0.55 0 22 0 50 135 10^b

^a H₂0/Si0₂: Values between brackets indicate the H₂0/Si0₂ ratio after evaporation. k Agitation at 50 rpm.

Table 2 Product Characterization

IR, cπT¹ DRS, αm^-**-

Example Remarks (%) Yield XRD

960 575 525 . 30,000 34,000 47,500

Comp. 1 Ludox HS40/H₂0₂/ 0 amorphous no no no yes(s) yes(s) no no ageing

1 Ludox HS40/H₂O₂/ 4 TiB yes(w) yes(s) yes(s) yes(v ) yes(w) yes(s) ageing

2 Ludox AS40/H₂0₂/ 20. TiB yes(s) yes(s) yes(s) no no yes(s) ageing

3 more Ti/increased 35 TiB yes(s) yes(s) yes(s) no no yes s) time and temp.

4 more Al 75 TiB yes(s) yes(s) yes(s) no yes(s) yes(s)

5 small head space 55 TiB yes(s) yes(s) yes(s) no no yes(s)

6 large head-space/ high ethylene 55 TiB yes(s) yes(s) yes(s) no no yes(s)

Comp. 2 Camblor method 10 Camblor-β yes(vw) yes(s) yes(s) yes(w) yes(s) no

vw = very weak; w = weak and s = strong

The results of Tables 1 and 2 show, with reference to Comparison Example 1 and Example 1, the importance of ageing the synthesis mixture before the hydrothermal treatment. The IR of Comparison Example 1 showed neither the typical zeolite-β framework vibrations at 575 and 525 cm^-1 nor the Ti=0 vibration at 960 cm^-1, x-ray diffraction (XRD) indicating the absence of crystallinity. Under DRS examination, the bands at 30,800 cm^-1, assigned to agglomerated Ti0₂ , and 34,000 cm^-1, assigned to finely dispersed Ti0₂, were both strong. In contrast in Example 1, carried out with ageing, all the above-mentioned IR bands were present, although the 960 cm^-1 was weak, and while the above- mentioned DRS bands were present, they were weak, and were accompanied by a strong band at 47,500 cm^-1, assigned to titanium in the framework of the zeolite. The yield, at 4% was, however, very low, yield being calculated as follows:

Yield % = 100 (weight of calcined zeolite obtained) weight of Si0₂ and A1₂0₃ in gel

In Example 2, an NH₄ ⁺ stabilized silica source is used; a much higher yield, 20%, is obtained, and the DRS bands attributable to the Ti0 phase are absent.

In Example 3, with a higher titanium content and higher temperature and longer time of crystallization, an improved yield (35%) is obtained. In Example 4, a higher yield (75%) results from a higher aluminium content, but a strong band at 34,000 cm^-1 indicates Ti0₂ present, possibly indicating co-formation of Al-β, Al-Rich Ti-β and Ti0₂.

In Examples 5 and 6, a high ethene pressure is maintained, in Example 5, by a small head-space and in Example 6 by ethene addition during crystallization. High yields are obtained with no indication of Ti0₂ contamination.

In Comparative Example 2, the absence of the band at 47,500 cm^""1 and the presence of the other two DRS bands indicate that a substantially different structure of Ti-β zeolite is being achieved by the process of the present invention from that of the reported procedure.

Overall, the results show that the optimum synthesis has the following characteristics: a high ethene pressure; synthesis gel ageing; peroxide presence; absence of alkali metal cations; and low aluminium content.

Claims

Claims :

1. A process for the manufacture of a Ti-, V- or Zr-Beta zeolite in which at least a part of a hydrothermal treatment of a Ti-, V- or Zr-Beta forming synthesis mixture is carried out under an ethene- containing atmosphere at a pressure of at least 20 bar.

2. A process as claimed in claim 1, wherein at least part of the hydrothermal treatment is carried out under an ethene partial pressure of at least 5 bar.

3. A process as claimed in claim 2, wherein the ethene partial pressure is at least 20 bar.

4. A process as claimed in claim 2, wherein the ethene partial pressure is at least 30 bar.

5. A process as claimed in any one of claims 1 to 3, carried out at a total pressure of at least 30 bar.

6. A process for the manufacture of a Ti-, V-, or Zr-Beta zeolite in which at least a part of a hydrothermal treatment of a Ti-, V-, or Zr-Beta forming synthesis mixture is carried out in the presence of at least 0.1 mole of ethene per mole of tetraethylammonium cations.

7. A process as claimed in claim 6, wherein the mole ratio of ethene:tetraethylammonium is in the range 0.1 to 1:1.

8. A process as claimed in any one of claims 1 to 7, wherein the synthesis mixture comprises water, a source of silicon, a source of titanium, a source of aluminium, and a source of tetraethylammonium ions.

9. A process as claimed in claim 8, wherein the molar composition of the synthesis mixture is within the following ranges:

Si0₂ (1); Ti0₂ (0.0001 to 0.2) ; A1₂0₃ (0.0005 to 0.1); H₂0 (10 to 100) ; TEAOH (0.01 to 1 )

10. A process as claimed in any one of claims 1 to 9, wherein the synthesis mixture contains colloidal silica.

11. A process as claimed in claim 10, wherein the colloidal silica is substantially alkali metal free.

12. A process as claimed in any one of claims 1 to 9, wherein the synthesis mixture contains a tetraalkylorthosilicate.

13. A process as claimed in any one of claims 1 to

12, wherein the synthesis mixture, at least initially, contains hydrogen peroxide.

14. A process as claimed in any one of claims 1 to

13, wherein the synthesis mixture is aged between its formation and the hydrothermal treatment.

15. A process as claimed in claim 14, wherein at least part of the ageing is carried out at room temperature.

16. A process as claimed in claim 14 or claim 15, wherein at least part of the ageing is carried out at an elevated temperature.

17. A process as claimed in any one of claims 1 to 16, wherein the synthesis mixture subjected to hydrothermal treatment contains ethanol, advantageously in a proportion of at most 2 moles per mole of Si0 .

18. A process as claimed in any one of claims 1 to

17, wherein hydrothermal treatment is carried out at a temperature within the range of from 120°C to 200°C.

19. A process as claimed in any one of claims 1 to

18, wherein hydrothermal treatment is carried out for from 1 hour to 30 days.

20. A process as claimed in any one of claims 1 to

19, wherein after hydrothermal treatment the resulting crystals are recovered and heated in air at from 200 to 600°C, for from 1 to 72 hours.

21. A process as claimed in claim 20, wherein the calcined product is treated with an acid or a base, or is steamed.

22. Ti-, V-, or Zr-Beta zeolite obtainable by the process of any one of claims 1 to 21.

23. The use of an ethene-containing atmosphere during hydrothermal treatment of a synthesis mixture to improve the yield of Ti-, V-, or Zr-Beta zeolite.

24. The use of the product of any one of claims 1 to 21, or of the product as claimed in claim 22, as a catalyst in the oxidation of an organic compound.

25. The use as claimed in claim 24, wherein the oxidation is carried out using an organic peroxide.

26. The use as claimed in claim.24 or claim 25, wherein the organic compound is a saturated hydrocarbon.

27. Any new feature described herein or any new combination of hereindescribed features.