Title of Invention

POLYTYPE Mg-Al HYDROTALCITE

Abstract

The present invention pertains to Mg-Al anionic clay having 3R2 stacking. This new polytype of anionic clay has a three-layer repeat, but it has a different interlayer arrangement than the conventional 3R1, hydrotalcite. Said new polytype can be applied in all applications described before for the conventional 3R1 polytype anionic clay such as in catalyst compositions, catalyst additive compositions, catalyst supports, absorbent compositions, stabiliser compositions and in medicaments.

Full Text

This invention pertains to a new polytype of Mg-Al anionic clay. Anionic clays have a crystal structure which consists of positively charged layers built up of specific combinations of metal hydroxides between which there are anions and water molecules. Hydrotalcite is an example of a naturally occurring anionic clay, in which carbonate is the predominant anion present. Meixnerite is an anionic clay wherein OH" is the predominant anion present. In hydrotalcite-like anionic clays the brucite-Iike main layers are built up of octahedra alternating with interlayers in which water molecules and anions, more particularly carbonate ions, are distributed. The mterlayers contain anions such as NO3", OH, CI", Br", 1", S04^ S03^Cr04^", BOa^", Mn04", HGa03^ HV04^", CIO4", BOi^% pillaring anions such as Vio02g"6 and M07024^", monocarboxylates such as acetate, dicarboxylates such as oxalate, alkyl sulphonates such as laurylsulphonate. Anionic clays have a layered structure corresponding to the general formula Wherein m and n have a value such that m/n=l to 10, preferably 1 to 6, and b has a value in the range of from 0 to 10, generally a value of 2 to 6 and often a value of about 4 X may be COs^", OH" or any other anion normally present in the interlayers of anionic clays. It is more preferred that m/n should have a value of 2 to 4, more particularly a value close to 3. It should be noted that a variety of terms is used to describe the material which is referred to in this patent as an anionic clay. Hydrotalcite-like and layered double hydroxide are interchangeably used by those skilled in the art. In this patent application we refer to the materials as anionic clays, comprising within that term hydrotalcite-like and layered double hydroxide materials. The preparation of anionic clays has been described in many prior art publications. Two major reviews of anionic clay chemistry were published in which the synthesis methods available for anionic clay syntiiesis have been summarized, F. Cavani et al "Hydrotalcite-type anionic clays; Preparation, Properties and Applications," Catalysis Today". 11 (1991) Elsevier Science Publishers B. V. Amsterdam. J P Besse and others "Anionic clavs: trends in pillaring chemistry its synthesis and microporous solids"(1992), 2, 108, editors: M.I. Occelli, H.E. Robson, Van Nostrand Reinhold, N.Y. In these reviews two structurally different forms of anionic clays are described: the 3Ri (three-layer repeat) and the 2Hi (two-layer repeat) corresponding to hydrotalcite and manassite, respectively. The Mg-Al anionic clays prepared by conventional preparation methods such as co-precipitation, optionally followed by hydrothermal treatment or aging to increase the crystallite size, have a 3Ri stacking. Also naturally occurring hydrotalcite has the 3R| stacking. In the pubhcations in Clay and Clay Minerals, Vol41, No.5, pages 551-557 and pages 558-564 of Bookin and Drits, it is stated that 3R2 polytypes have been observed in nature, however, only in sulfate Mg-Al anionic clays. For ftirther work on anionic clays, reference is given to the following articles: Helv. Chim. Acta, 25,106-137 and 555-569 (1942) J. Am. Ceram. Soc. 42, no. 3,121 (1959) Chemistry Letters (Japan"i. 843 (1973) Clays and Clay Minerals. 23, 369 (1975) Clays and Clay Minerals. 28, 50 (1980) Clavs and Clay Minerals. 34, 507 (1996) Materials ChemistrY and Phvsics. 14, 569 (1986). In addition there is an extensive amount of patent literature on the use of anionic clays and processes for their preparation. The prior art described below describes the preparation of anionic clays by the co-precipitation method: European Patent Application 0 536 879 describes a method for introducing pH ~ dependent anions mto the clay. The clay is prepared by the addition of a solution of a solution of AI(N03)3 and Mg(N03)2 to a basic solution containing borate anions. The product is then filtered, washed repeatedly with water, and dried overnight. Additionally mixtures of Zn/Mg are used. In US 3,796,792 by Miyata et al. entitled "Composite Metal Hydroxides" a range of materials is prepared into which an extensive range of cations is incorporated, including Sc, La, Th, In, etc. In the examples given solutions of the divalent and trivalent cations are prepared and mixed with base to cause co-precipitation. The resulting products are filtered, washed with water, and dried at 80°C. Example 1 refers to Mg and Sb and Example 3 to Mg and Bi. Other examples are given, and in each case soluble salts are used to make solutions prior to precipitation of the anionic day at high pH. In US 3,879,523 by Miyata entitled "Composite Metal Hydroxides" also a large number of preparation examples is outlined. The imderlying chemistry, however, is again based on the co-precipitation of soluble salts followed by washing and drying. It is important to emphasize that washing is a necessary part of such preparations, because to create a basic environment for co-precipitation of the metal ions a basic solution is needed and this is provided by NaOH/NajCOj solutions. Residual sodium, for example, can have a significant deleterious effect on the subsequent performance of the product as a catalyst or oxide support In US 3879525 (Miyata) very similar procedures are again described. In US 4,351,814 to Miyata et ai. a method for making fibrous hydrotalcltes is described. Such materials differ in stnjcture from the nomial plate-like morphology. The synthesis again involves soluble salts. For example, an aqueous solution of a mixture of MgCl; and CaCl; is prepared and suitably aged. From this a needle-iike product Mg2(OH)3C1.4HjO precipitates. A separate solution of sodium aiuminate is then reacted in an autoclave with the solid Mg2(OH)3C1.4H20 and the product is again filtered, washed with water, and dried. In US 4,458,026 to Reichle, in which heat-treated anionic clays are described as cataiysts for aldol condensation reactions, again use is made of magnesium and alurnbium-nitrate salt solutions. Such solutions being added to a second solution of NaOH and Na^COj. After precipitation the slurry is filtered and washed twice with distilled water before drying at 125 "C. In US 4,656,156 to Misra the preparation of a novel absorbent based on mixing activated alumina and hydrotalcite is described. The hydrotafcite is made by reacting activated MgO (prepared by activating a magnesium compound such as magnesium carbonate or magnesium hydroxide) vtrith aqueous solutions containing aiuminate, cariaonate and hydroxy! ions. As an example the solution is made from NaOH, Na^CO, and AIsO,. In particular, the synthesis involves the use of industrial Bayer liquor as the source of Ai. The resulting products are washed and filtered before drying at 105 "C. In US 4,904,457 to Misra a method is descritsed for producing hydrotaidtes in high yield by reacting activated magnesia v^fith an aqueous solution containing aluminate, carbonate, and hydrDxyl ions. The methodology is repeated in US 4,65B, 156. In US 5,507,980 to Kelkar et at al. a process is described for making novel catalysts, catalyst supports, and absort^ers comprising synthetic hydrotalcite-like binders. The synthesis of the typical sheet hydrotalcite involves reacting pseudD-boehmite to which acetic acid has been added to peptize the pseudo-boehmite. This is then mbced wjih magnesia. In US 6,539,861 a process is disclosed for preparing a catalysts for synthesis gas production based on hydrotalcites. The method of preparation is again based, on the co-precipitation of soluble salts by mixing with base, for example, by the addition of a solution of RhCl,, MgCNOg)^ and AI(N03)3 to a solution of Na^COaandr^aOH. ^^^^"""^ Also in US 5,399,537 to Bhattacharyya in tiie preparation of nickel-containing catalysts based on hydrotaldte use is made of the co-predpttation of soluble magnesium and aluminium salts. In US 5,591,418 to Bhattacharyya a catalyst for removing suiftjr oxides or nftrogen oxides from a gaseous mixture is made by calcining an anionic clay, said anionic clay having been prepared by co-precipitation of a solution of MgtNOa);, AI(N03)3 and CeCNO^),. The product again is filtered and repeatedly washed with de-ionized water. In US 4,946,581 and US 4.952.382 to van Broekhoven co-precipitation of soluble salts such as Mg(N03)2and AJ(N03)3 with, and without the incorporation of rare earth salts was used for the preparation of anionic clays as catalyst components and additives. A variety of anions and di- and tri-valent cations are described. In US 5,114,898AVO 9110505 Pinnavaia et a!, describe layered double hydroxide sorbents for the removal of sulflir oxide{s) from flue gases, which layered double hydroxide is prepared by reacting a solution of Al and Mg nitrates or chlorides with a solution of NAOH and NajCOg. In US 5,079,203 A/VO 9118670 layered doubte hydroxides intercalated with poiyoxo anions are described, with the parent clay being made by co-precipitation techniques. In US 5,578,286 in the name of Alcoa a process for the preparation of meixnerite is described. Said meixnerite may be contacted with a dicariaoxylate or polycarboxylate anion to fonn a hydrotalcite-!fke material. As indicated in the description of the prior art given-above, there are many applications of anionic clays. These Include but are not restricted to: catalysts, adsorbents, drilling muds, catalyst supports and carriers, extenders and applications in the medical field. In particular van Broekhoven has described their use in SO^ abatement chemis^. The present invention provides a new polytype of Mg-AI anionic clay. Said new polytype can be applied in all applications descriiDed herein before for the conventional SR, polytype anionic day. Tne present invention pertains to Mg-AI anionic clay having SRj stacking. This new polytype of anionic clay also has a three-layer repeat but it has a different interiayer an^ngement than the conventional 3R, hydrotalcite. Tne two polytypes can t>e distinguished from each other by the intensities of the 107 and 108 reflections. The 3R; type anionic day has a stronger 107 reflection close to 45 " 2 theta (as predicted by Drits and Bookin), wrtiereas the 3Ri type has a stronger reflection dcse to 47 " 2 theta (the 018 refiedion). The presence of both a peak at 45 and 47 " 2 theta of comparable intensities suggests the presence of a mixture of the two. It is understood that the precise 2 theta values for the 107 and 11>8 reflections will depend on the lattice a and c parameters for the Mg-AI anionic day. Of course there are more differences in the X-ray diffradion pattern, but this is the best range of reflection to make a distindion because hardly any other reflections exist in that range from other compounds which are likely to be present as well in anionic clay-like material. For example. boehmite has a weak reflection in that range, but its presence can t>e excluded in the absence of a strong reflection between 13 and 15 " 2 theta. Further, the new polytype Mg-AI anionic day appears to have a different morphology from the conventional 3Ri type anionic clay, as can be seen by SEM examination. The SR; type anionic day appears to have a strudure wi^ a irregular flake-iike platelets which are randomly agglomerated. Conventional 3R, anionic day has regular well-formed layers of platelets which are arranged in the usual bookstackform. The new polytype anionic clay also has interlayers in which molecules of water and anions are distributed. The main anion will be hydroxide, but in addition to that other anions may be present in the new polytype anionic day such as NO3" , OH, Cr, Br, f, C03=-, bicarbonate, SO^^ SiOj^ CrO/", BOs^", MnO/, HGaOs^", HVO/-, CIO/, BOj^-- piiiaring anions such as VIQOSB"^ and MOyO^,^, monocarboxylates such as acetate, dicarboxylates such as oxalate, alkyl sulphonates sudi as iaurylsulphonate as intercalating anions. . The Mg-AI anionic clay having SRj stacking may be prepared by hydrotheimaliy treating a siun7 containing an aluminium source and a magnesium source to forni a Mg-AI anionic clay having 3R2 stacking. Aluminium sources which are suitable for the preparation of the new potytype Mg-AI anionic clay are: crystalline aluminium trihydrate (ATH), for example gibbsites provided by Reynolds Aluminium Company RH-20cBi or JM Huber Micral ® grades, BOC (Bauxite Ore Concentrate), bauxite, bayerite and nordstrandite, thermally treated forms of aluminium trihydrate, alumina sols, flash calcined alumina, gels, pseudo-boehmite, boehmite BOC and bauxite are the cheapest alumina sources which are excellently suitable starting materia! for the new potytype anionic day. The alumina trihydrate is preferred to have a small particle size. Thennaliy treated fonms of aluminium trihydrate are readily obtained by thermally treating aluminium trihydrate (gibbsite) at a temperature ranging from 100 to 800 "C for 15 minutes to 24 hours. In any event, the calcining temperature and time for obtaining calcined aluminium trihydrate should be sufficient to cause a measurable increase of the surface area in view of the surface area of the gibbsite as produced by the Bayer process which is generally between 30 and 50 mVg. It should be noted that within the concept of this invention flash calcined alumina is also considered to be a thennaliy treated fom^ of aluminium trihydrate, although generally it is considered a totally different alumina. Flash caldned alumina is obiained by treating aluminium trihydrate at temperatures between 800-1000 "C for very short periods of time in special industrial equipment, as is described in US 4,051,072 and US 3,222,129. Combinations of various thennally treated forms of aluminium trihydrate can also be used. Also combinations of various alumina sources can be used. The aluminium source may be added as a solid, in suspension or in solution to the reactor to make the slurry. It may also be combined w/ith the magnesium source prior to the addition to the reactor to form the slurry. Magnesium sources vifhich may be used indude MgO and Mg(OH)2, dolomite and sepjolite. Also combinations of Mg sources may be used. The magnesium source may be added to the reader as a solid, a solution, or, preferably, as a slurry. The magnesium source may also be combined with the aluminium source before it is added the reader to make a slurry. As can be seen from the aluminium and magnesium sources mentioned -above, it is possible to prepare the new polytype Mg-AI anionic clay from relatively inexpensive starting materials such as BOC and Gibbsite. Also for the magnesium source inexpensive material can be used such as inexpensive MgO grades. Especially when using these inexpensive magnesium sources, ft is usually advisable to mill the magnesium source before use. Preferably, both the aluminium source and the magnesium source are milled before use to ensure readion to the SRj anionic day. When wet milling is used, the slurry containing both aluminium source and magnesium source may be wet milled, for iristance in a ball mill, and directly transferred to the reador which can operate under hydrothermal conditions. An additional advantage of using inexpensive starting materials such as oxides and hydroxides, is the fed that no additional ions are introduced in to SRj Mg-AI anionic clay. This is also the case when using carbonates as starting materials. In tiiat case, the process does not require washing of the product or filtering, there is no filtrate vraste or gaseous emissions (e.g. from acid decomposition), making the process particularly environmental-friendly and more suited to the environmental constraints which are increasingly imposed on commercial operations. The product can be spray dried directly to form microspheres or can be extruded, palletized or beaded to form shaped bodies. The new polytype Mg-Al anionic clay may also be shaped during preparation. In that case the SRj Mg-Al anionic clay is formed in shaped bodies by a process which comprises the steps of: a) shaping the slurry of magnesium source and aluminium source into shaped bodies, b) optionally thermally treating the shaped bodies, and c) hydrothermally treating the shaped bodies to form anionic clay having 3R2 stackmg in the shaped bodies. In another embodiment 3R2 anionic clay containing shaped bodies are prepared by: a) shaping a slurry of either an aluminium source and/or magnesium source into a shaped body, b) optionally treating the shaped body, and c) hydrothermally treating the shaped body in a solution containing aluminium source and/or magnesium source as to form anionic clay. Suitable shaping methods include spray-drying, pelletising, extrusion (optionally combined with kneading), beading, or any other conventional shaping method used in the catalyst and absorbent fields or combinations thereof The amount of liquid present in the slurry used for shaping should be adapted to die specific shaping step to be conducted. It might be advisable to (partially) remove the liquid used in the slurry and/or add additional or other liquid, and/or change the pH of the precursor mixture to make the slurry gellable and thus suitable for shaping. Various additives commoniy used in the various shaping methods such as extrusion additives may be added to the precursor mixture used for shaping. After shaping the shaped bodies may optionally be submitted to a thermal treatment. Such a treatment increases the physical strength of the particles. The them^al treatment can be conducted in an oxygen-containing atmosphere, in an inert atmosphere or in steam at temperatures varying from 30 to lOOCC for a time ranging from a few minutes to 24 hours. As in, for instance, spray-drying a thermal treatment is inherently involved, a further themial treatment may not be necessary. Both with and without shaping prior to the formation of the SR; anionic clay the actual reaction to form the SRj Mg-AI anionic clay is conducted under hydrothermal conditions. Within the context of this description this means in the presence of water (or steam) at a temperature above 100 "C at increased pressure. Preferably the reaction takes place in water in an autoclave at a temperature above 100 "C, i.e. under autogeneous pressure. If no shaping tal containing aluminium source and magnesium source may simply be subjected to hydrothermal treatment It is preferred to conduct the hydrothermal treatment in a "hydroxyl"rich" environment This can be done by purging the slurry vrith nitrogen or inert gas or by adding hydroxy! anions to the hydrothennal treatment medium. For instance ammonium hydroxide may be added. if the slurry is shaped first and optionally themially treated, the shaped bodies must be brought into contact with water or steam for the hydrothermal treatment. If desired a preformed anionic day may be added to the reaction mixture. Said preformed clay may be recycied anionic clay from the reaction mixture or anionic clay made separately by tfie process according to the invention. Shaped bodies containing the new polytype Mg-Al anionic clay have not been described before, therefore the present invention is also directed to these shaped bodies containing SR^ Mg-Al anionic day. Because of its simplicity, this process can be carried out in a continuous mode by mixing of a first slurry comprising aluminium source and a second slurry comprising magnesium source passing the mixed slurry, optionally after milling, through a reactor vessel which can operate under hydrothermal conditions. Said first and/or second slurry may be subjected to a treatment prior to mixing the slurries. The process may also be conducted In a continuous multi-step operation. If desired inorganic acids and bases, for example for control of the pH, may be added to the slurry before or during reaction or to the individual reactants before combining them in the slurry. The acid and bases of choice are ionmc acid, acetic acid, nitric acid and ammonium hydroxide, because these types of acids and bases do not introduce unwanted ions in the reaction mixture. If desired, the anionic clay prepared by the process according to the invention may be subjected to ion exchange. Upon ion exchange the interiayer charge-balancing anions are replaced with other anions. Upon ion exchange some of the anionic clay may be converted to a SR, stacking. Said other anions are the ones commonly present in anionic clays and include pillaring anions such as VioOas"^. MoyOa^^ Said ion exchange can be conducted before drying or after the anionic clay Is formed upon hydrothermal treatment. The process of the invention provides wide flexibiiitv in orenarinn nraduets with a wide range of Mg;Al ratios. The Mg:Al ratio can vary from 0.1 to 10, preferably from I to 6, more preferred from 2 to 4, and especially preferred to close to 3. For some applications it is desfrable to have additives, both metals and non- metals, such as rare earth metals. Si, P, B, group VI, group VIII, alkaline earth (for instance Ca and Ba) and/or transition metals (for example Mn, Fe, Ti, Zr, Cu, Ni, Zn, Mo, Sn), or mixtures thereof present in or on the 3R2 Mg-Al anionic clay. Said metals can easily be deposited on the anionic clay. They can also be added either to the magnesium source or the aluminium source or to the slurry during preparation of the 3R2 Mg-AI anionic clay. It is also possible to prepare a 3R2 type anionic clay by conversion of a 3R[ type anionic clay. To this end the 3R| type anionic clay is calcined, rehydrated, and hydrothermally treated in a hydroxyl-rich environment. This can also be done with a 3Ri anionic clay containing shaped body. It is even possible to prepare a shaped body containing both 3Riand 3R2type anionic clay. It is also possible to convert the 3R2 to a 3Ri type anionic clay. To this end the 3R2 type anionic clay is calcined, hydrated and hydrothermally treated in a carbonate-rich environment such as in the presence of CO2 or by adding carbonate anions such as ammonium carbonate to the hydrothermal treatment medium. It is also possible to prepare composites of both 3Ri and 3R2 type anionic clays. These composites may be prepared from a mixture of a Mg source which promotes 3R2 formation and a Mg source which promotes 3Ri formation and/or a Al source which promotes 3R2 formation and an Al source which promotes 3R1 formation. Al sources which promote 3R2 type anionic clay formation have been, described above AI sources which promote 3R| type anionic clay formation are aluminum salts such as aluminium nitrate, alummium chloride, aluminium chlorohydrate and sodium aluminate Mg sources which promote 3R2 type anionic clay formation have been described above. Mg sources which promote uR, type anionic clay formation are magnesium salts such as magnesium acetate, magnesium formate, magnesium hydroxy acetate, hydromagnesite (Mg5(C03)4(OH)2), magnesium carbonate, magnesium bicarbonate, magnesium nitrate, and magnesium chloride. It should be noted that it is not necessary that all the Al source and all the Mg is converted into anionic clay. In some catalytic applications is advantageous to have some unreacted {meaning: not reacted to anionic day) Al-source and/or Mg source left in the product. For instance, in shaped bodies excess alumina improves the binding properties and both Mg and Al provide different types of desirable functionalities. For example, Al provides acid sites for catalytic cracking and improved nickel encapsulation and Mg provides basic sites which improve the suitability for removing or neutralizing strong acid streams of gasses or liquids. The present invention is further directed to catalyst compositions comprismg Mg-Al anionic clay having SRa stacking. Said catalyst composition may comprise all components usually present in catalyst compositions such as matrix and/or binder materia!, zeolites and additive components. The new polytype Mg-Al anionic day may be incorporated into the catalyst composition as such or as shaped bodies. Said catalyst compositions may be used for hydrocarbon conversion reactions such catalytic cracking, hydrocracking, hydrogenation, polymerisation, steam reforming, base-catalysted reactions etcetera. The new polytype Mg-Al anionic cisy may also be combined with catalysts as additive compositions. Therefore, the present invention is also directed to catalyst additive compositions comprising Mg-Ai anionic clay having 3R; stacking. Said additive compositions usually comprise a matnx of binder material and optionally additional additrve components. Again the new polytype Mg-W anionic clay may be incorporated into the additive composjtion as such or as shaped bodies. Anionic clays are for instance known active components for SO^ or NO, removal additive compositions in catalytic hydrocartson convei^ion reactions. The SR^ Mg-AI anionic clays according to the invention are also suitable active components for SO^ or NO, removal additive compositions, especially when metals such as Ce and V are present in or on the anionic clay. The 3R2 Mg-AI anionic clays according to the invention are further suitable for use as catalyst support, both when applied as such and applied as shaped bodies. For instance, the anionic clay may be used as support for Ziegler-Natta catalysts, for CeOj catalysts etctera. The new polytype Mg-AI anionic clay can also be used in absorbent compostions and stabiliser compositions, both as such and as shaped bodies. For instance, the SR; Mg-AI anionic clay are excellent for use in stabiliser compositions for chlorine-containing (co)polymers, as halogen scavenger or as absorbent for waste water treatment or as flame retardanl Furthermore, the SRj Mg-AI anionic day as a suitable active component in medicaments such as antiacids, antipeptin and stabiliser. The present invention will be further illustrated by Examples which are not to be constmed as limitative In any way. EXAMPLES Comparative example 1 A Mg-AI hydrotalcite is prepared by thermally treating a slurry compnsing gibbsite, flash calcined gibbsite and MgO at a temperature of 65 "C for 4hours. The XRD pattern of the product shows that a Mg-AI anionic day is formed having SR, stacking. Example 2 A Mg-AI hydrotalcite is prepared by hydrothermally treating a slurry comprising gibbsite. flash calcined gibbsite and milled MgO at a temperature of 180 "C for 1 hour. The XRD pattern of the product shows that a Mg-AI anionic clay is formed having SR; stacking. Example 3 in a 10 iiter autoclave MgO (ex Merck ®) and BOC in a ratio 4:1 were slunied. The slurry was milled and hydrothernially treated at 170 "C for 90 minutes. The XRD pattern of the product showed the presence of SRj type anionic clay. Example 4 in a 10 liter autoclave MgO (ex Nedmag ®) and BOC in a ration 4:1 were slurried. The slurry was milled and hydrothermally treated at 170 "C for 90 minutes. The XRD pattern of the product showed the presence of 3R; type anionic clay. WE CLAIM: 1. Mg-Al anionic clay having interlayer spacing with a hydroxyl group anion contained in the interlayer spacing, said clay having 3R2 stacking. 2. Mg-Al anionic clay as claimed in claim 1, wherein the interlayers contain in addition to hydroxyl, N03", OH, CI", Br\ I", C032", S042", Si032\ Cr042", B032\ Mn04\HGa032\HV042" C1O4 B032" pillaring anions such as V](,02s6 and MO7O24", monocarboxylates such as acetate, dicarboxylates such as oxalate, alkyl sulphonates such as laurysulphonate as intercalating anions. 3. Mg-Al anionic clay as claimed in claim 1 or 2, wherein additives are present in the anionic clay. 4. Mg-Al anionic clay as claimed in claim 3, wherein the additives are selected from rare earth metals, Si, P, B, group VI, group VIII, alkaline earth such as Ca and Ba and transition metals such as Mn, Fe, Ti, Zr, CV, Ni, Zn, Mo, Sn and mixtures thereof. 5. A process for the preparation of an Mg-Al anionic clay with hydroxyl in its interlayer having 3R2 stacking wherein a slurry containing an aluminium source and a magnesium source is hydrothermally treated to form a Mg-Al anionic clay having 3R2 stacking. 6. The process as claimed in claim 5, wherein the magnesium source has been milled prior to the hydrothermal treatment of the slurry. 7. The process as claimed in claim 6, wherein the magnesium source is milled prior to the addition to the slurry. 8. The process as claimed in claims 5 or 6, wherein the magnesium source and aluminium source are milled. 9. The process as claimed in any one of claims 5 to 8, comprises the steps of a) shaping the slurry of magnesium source and aluminium source into shaped bodies, b) optionally thermally treating the shaped bodies, and) hydrothermally treating the shaped bodies to form anionic clay having 3R2 stacking in the shaped bodies. 10. A process for the preparation of Mg-Al anionic clay with hydroxyl in its interlayer having 3R2 stacking wherein an anionic clay having 3R1 stacking is calcined, rehydrated and hydrothermally treated in a hydroxyl rich environment to form Mg-Al anionic clay with 3R2 stacking. 11. A catalyst composition comprising Mg-Al anionic clay as claimed in any one of the preceding claims.

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in-pct-2002-0214-che abstract duplicate.pdf

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in-pct-2002-0214-che claims duplicate.pdf

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in-pct-2002-0214-che correspondence others.pdf

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in-pct-2002-0214-che petition.pdf