Method of obtaining multimetallic oxides derived from hydrotalcite-type compounds

(57) Abrégé/Abstract:

The invention relates to a method of preparing multimetallic hydrotalcites, the physicochemical characteristics thereof and the use of same as sulphur oxide (SOx) reducing materials, such as SO₂ or SO₃ which are contained in gaseous streams, particularly in flue gases emitted by the regeneration section of the fluid-bed catalytic cracking process. The inventive method improves the SO_Xabsorption capacity per unit of specific area of multimetallic hydrotalcite obtained and the absorption and regeneration speeds of the calcination products of the aforementioned hydrotalcites, with the incorporation of ternary and/or quaternary cations in the laminae of said precursor materials. In order to discover the effect of the composition of said hydrotalcites, a combination of physical and chemical methods were applied such as to characterise same by means of X-ray diffraction, textural analysis, CO₂absorption microcalorimetry and, primarily, SO₂ oxidation reduction.

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CA 02562014 2006-10-02 (12) SOLICITUD INTERNACIONAL PUBLICADA EN VIRTUD DEL TRATADO DE COOPERACIÔN

EN MATERIA DE PATENTES (PCT) (19) Organization Mundial de la Propiedad Intelectual

Oficina international (43) Fecha de publication internacional 13 de Enero de 2005 (13.01.2005)

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(10) Nûmero de Publicacion Internacional

PCT WO 2005/003034 Al (51) Clasificaciôn Internacional de Patentes⁷: COIF 5/00, 7/00, C01G 9/00, 53/00, 3/00, 51/00, 49/00 (21) Nûmero de la solicitud internacional:

PCT/MX2003/000051 (22) Fecha de presentation internacional:

de Julio de 2003 (07.07.2003) (25) Idioma de presentation: espanol (26) Idioma de publicacion: espanol (71) Solicitante (para todos los Estados designados salvo

US): INSTITUTO MEXICANO DEL PETROLEO [ΜΧ/ΜΧ]; Eje Central Lazaro Cardenas, Norte No.152, Col. San Bartolo Atepehuacân, C. P. 07730 México, D.F (MX).

(72) Inventores; e (75) Inventores/Solicitantes (para US solamente): SANCHEZ VALENTE, Jaime [ΜΧ/ΜΧ]; Prisco No. 526, Col. Lindavista, C. P. 07730 México, D. F. (MX). LOPEZ SALINAS, Esteban [ΜΧ/ΜΧ]; Calle 203 No.9 , D-403, Col. Sn. Bartolo Atepehuacân, C. P. 07730 México, D. F. (MX). SANCHEZ CANTÙ, Manuel [MX/MXJ; Calle 203 No. 209 D-403, Col. San Bartolo Atepehuacân, C. P. 07730 México, D.F (MX). HERNANDEZ BELTRAN, Francisco [ΜΧ/ΜΧ]; Fuente del

Mirador No. 26, Col. Tecamachalco, C. P. 53970 México D.F. (MX).

(74) Mandatario: RODRIGUEZ VÊLEZ, ROBERTO; Eje Central Lâzaro Cârdenas No. 152, Col. San Bartolo Atepehuacân, C. P. 07730 México, D.F. (MX).

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(84) Estados designados (regional): patente ARIPO (GH, GM, KE, LS, MW, MZ, SD, SL, SZ, TZ, UG, ZM, ZW), patente euroasiâtica (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), patente europea (AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HU, IE, IT, LU, MC, NL, PT, RO, SE, SI, SK, TR), patente OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, ML, MR, NE, SN, TD, TG).

Pubbcada:

— con informe de biisqueda internacional

Para côdigos de dos letras y otras abreviaturas, véase la seccion Guidance Notes on Codes and Abbreviations que aparece al principio de cada numéro regular de la Gaceta del PCT.

wo 2005/003034 Ai IIIIIIIIIIIIIIIIIIIIIIIIIM (54) Title: METHOD OF OBTAINING MULTIMETALLIC OXIDES DERIVED FROM HYDROTALCITE-TYPE COMPOUNDS (54) Titulo: OBTENCI0N DE ÔXIDOS MULTIMET ALICOS DERIVADOS DE COMPUESTOS DEL ΊΊΡΟ HIDROTALCITA.

(57) Abstract: The invention relates to a method of preparing multimetallic hydrotalcites, the physicochemical characteristics thereof and the use of same as sulphur oxide (SOx) reducing materials, such as SO₂ or SO₃ which are contained in gaseous streams, particularly in flue gases emitted by the regeneration section of the fluid-bed catalytic cracking process. The inventive method improves the SO_X absorption capacity per unit of specific area of multimetallic hydrotalcite obtained and the absorption and regeneration speeds of the calcination products of the aforementioned hydrotalcites, with the incorporation of ternary and/or quaternary cations in the laminae of said precursor materials. In order to discover the effect of the composition of said hydrotalcites, a combination of physical and chemical methods were applied such as to characterise same by means of X-ray diffraction, textural analysis, CO₂ absorption microcalorimetry and, primarily, SO₂ oxidation reduction.

(57) Resumen: La presente invention se relaciona con un procedimiento para la obtention de una serie de ôxidos mixtos multimetâlicos derivados de compuestos del tipohidrotalcita. En esta invention se describen las caracteristicas fisicas de las hidrotalcitas multimetâlicas y su aplicaciôn como materiales reductores de ôxido de azufre (SOx) tales como (SO2 ό SO3) contenidos en las corrientes gaseosas, particularmente en los gases de combustion emitidos por la seccion de regeneration del proceso de désintégration catalitica fluida (FCC). Estos materiales se pueden utilizar también para el propôsito anterior en los gases de combustion del carbon o combustion de hidrocarburos en las plantas generadores de energia y/o plantas quimicas. El procedimiento utilizado mejora la capacidad de absorciôn de SOx por unidad de ârea especifica de material obtenido, objeto de la presente invention, su velocidad de absorciôn y su velocidad de regeneration de los productos de calcination de las hidrotalcitas mencionadas al incorporer cationes terciarios y/o cuaternarios a las lâminas de estos materiales.

CA 02562014 2010-09-08

METHOD OF OBTAINING MULTIMETALLIC OXIDES DERIVED FROM

HYDROTALCITE-TYPE COMPOUNDS

DESCRIPTION TECHNICAL FIELD OF THE INVENTION

This invention is related to a procedure for obtaining a series of mixed multimetallic oxides derived from hydrotalcite type compounds. This invention describes the physical features of the multimetallic hydrotalcites and their application as sulfur oxide reducing materials (SO_X), such as (SO₂ or SO₃) contained in gas currents, particularly in combustion gases emitted by the regeneration section of the fluid catalyst disintegration process (FCC). These materials may be used also for the foregoing purpose in carbon combustion or hydrocarbon combustion gases in energy generating plants and/or chemical plants. The procedure employed improves the absorption capability of SO_X per specific area unit of obtained material, subject matter of this invention, the absorption speed and the regeneration speed of the calcining products of the aforementioned hydrotalcites by incorporating tertiary and/or quaternary cations to the plates of these materials.

BACKGROUND OF THE INVENTION

The FCC process effects the transformation of heavy fractions of oil, normally mixtures of atmospheric gas oils and vacuum, into valuable products such as gas, LP

CA 02562014 2006-10-02

Gas and light olefins, the latter, inputs of processes from the sintesis of fuels and petrochemicals, and it employes acid catalysts. The FCC industrial units are designed basically with two operation stages, the first one of reaction and the second one of regeneration, and between them the catalyst circulates permanently at a constant speed. Due to the nature of the chemical reactions involved, a carbonaceous subproduct is produced, better known as coke, and this is deposited on the surface on the catalyst surface and de-activates it. The catalyst regeneration takes place by means of the combustion of the coke deposited on the catalyst, and this occurs in the regeneration stage by means of controlled air injection. Coke combustion is an exothermic reaction increasing the catalyst temperature from about 773 to 803K in the reactor up to 923K in the regenerator. The coke combustion process produces, likewise, the oxidation of the sulfur associated to the latter, and this produces in turn the corresponding sulfur oxides in relative proportions very close to thermodynamic equilibrium. These, under the occurring operation conditions, are of approximately 10% SO₃ and 90% SO₂. In cases where a gas purifying system is not installed, they are emitted together with the combustion gases, into the atmosphere.

Sulfur oxides, named SOx, are toxic gases referring to sulfur dioxide mixtures (SO₂) and those of sulfur trioxide (SO₃), and these due to the action of ultraviolet light and the humidity of the atmosphere can be transformed into sulfuric acid and generate the so-called acid rain, according to the following chemical reactions:

The extremely negative environmental of the SO_X emissions has been recognized by the international scientifid and industrial communities, as well as by various government agencies of most countries in the world.

CA 02562014 2006-10-02

The number of S0_x emissions produced in the regenerator of an FCC unit is basically a function of the sulfur concentration on the load, the coke yield and the catalyst circulation rate. Approximately between 45 and 55% of the sulfur of the load is converted into H2S inside the FCC reactor, between 35 and 45% remains on the liquid products (gasoline, light cyclic oil and heavy oil) and between 5 and 10% is deposited on the catalyst associated to coke.

It is well known to persons familiar with the FCC process that control of the SOx emissions can be performed effectively and efficiently by using the catalyst itself, adequately modified with certain compounds or by means of the employment of materials known as Sox additives, added to the main catalyst inventory in relatively low (normally 10%) and controlled proportions.

Essentially, the materials that may be employed to reduce the SOx emissions should in principle be active for forming the corresponding sulfate and possess high adsorption capability. This is the case of magnesium oxide or aluminum oxide. On the other hand, thermodynamic calculations indicate that the capture of sulfur trioxide in alkaline metals is much more favorable in comparison with sulfur dioxide (Kocaefe and Karman, Cand. J. Chem. Eng., 63, 971-977 [1985]). This way, in order for a material to be employed efficiently in the FCC process, as an active agent in SOx additives, it should also possess sufficient activity to catalyze the transformation of sulfur dioxide into sulfur trioxide. Certain metals like cerium or vanadium and their oxides may be employed, due to their recognized activity as oxidation catalysts, especially suitable for oxidation from SO₂ to SO3. An essential attribute for an SOx additive is that referring to its capability for detaching itself from the absorbed sulfate,

CA 02562014 2006-10-02 and this permits regenerating the active entity and thus avoiding the saturation many materials show during the course of their use in the FCC unit. The loosening of sulfates takes place in the reaction stage upon contact of the material with the hydrocarbons found in the environment, or any other reducing agent, such as hydrogen produced as a subproduct.

The SO_X additives that have been most extensively employed in the FCC units are based on magnesium aluminate spinels (MgAI₂O₄) containing cerium oxide and vanadium oxide. These additives are described in USA patent No. 4,790,982, granted to Yoo and col. and USA patent No. 4,728,635, granted to Bhattacharyya and col. This type of additives, however, have shown in general a relatively limited absorption capability, a tendency to lose activity quickly due to the synthetization of the active phase and a slow regeneration speed regarding the residence time there is in the reaction stage in the FCC unit. The need to use materials permitting an increase in the activity of sulfur assimilation has been recognized, both due to a greater amount and due to a higher dispersion of the active metal. One of these materials is constituted by certain anionic clays known as hydrotalcites, comprised essentially of magnesium and aluminum in a sheet structure, and the general formula of the hydrotalcites is the following: Mg₆ Al₂ (OH)i₆ (CO3) 4H₂O. The presence of aluminum atoms produces negative charges in the stucture, and these are compensated with interlaminar anions. What is more common, these anions are carbonates, but they may be sulfates, chlorides or others. On the other hand, the Mg/AI atomic relationship in these materials may vary betwen 1.7 and 5 and it is possible that bivalent or trivalent cations substitute Mg or Al.

CA 02562014 2006-10-02 , &lt;

, I

The hydrotalcite synthesis is generally performed by means of a co-precipitation of metal salts. A classic preparation consists in mixing an aqueous solution of magnesium and aluminum salts, for example, nitrates or chlorides, and add it to a sodium carbonate solution under continuous stirring. The precipitate formed is submitted to heating for several hours at temperatures between 333 and 473K.

In USA patent 5,750,020 (1998), of Bhattacharyya and col., granted to AMOCO, Co., a collapsed hydrotalcite composition is described, and this may be obtained by calcining a mixed sheet hydroxide having monometallate anions on the interlaminar region. This collapsed composition is comprised substantially of microcrystals represented collectively by means of the formula: M2_m²⁺AI2-pMp ³⁺TrO γ+r.s, where M²⁺is a divalent metal, M³⁺ is a trivalent metal and T is Vanadium, Tungsten or Molybdenum. The little crystals are so small they cannot be detected by means of conventional X-ray difraction techniques; however, high resolution electronic microscopy reveals that a considerable portion of the little microcrystals is comprised of a solid solution of molecularly disperse aluminum oxide in the crystalline structure of the divalent metal monoxide. Another portion of the little microcrystals is constituted by the spinel phase. The collapsed composition functions to absorb sulfur oxide and has a comparatively high absorption capability and comparatively high absorption and desorption speeds, and also functions as a catalyst for nitrogen oxide reduction.

In USA patent 5,785,938 (1998) of Pinnavaia T. J. and col. a process to remove and later capture sulfur oxides from gas currents is described, particularly those effluents from the energy generating plants through coal burning, by using double

CA 02562014 2010-09-08 metal hydroxides containing Ni, as recyclable absorbents. The absorbing compositions contain metal components forming stable sulfites and sulfates at a temperature, but they are decomposed at a higher temperature to regenerate the absorbing material.

In USA patent 5,928,496 (1999), a process for the sorption of sulfur oxide by using hydrotalcite type materials, like contact solids, is described. Hydrotalcite type materials are stable when transformed to the crystalline structure of the oxide and are essentially reversible in an exchange of anions. These materials, made up of large crystal sheets and with a high SOx sorption capacity, are benefited in their sorption properties when modifying them with certain species of organic acid anions, which modify the hydrotalcite/brucite structure.

In USA patent 6,028,023 (2000) of Vierheilig A. A. , assigned to Bulldog Technologies Inc., a process for the preparation of hydrotalcite type compounds is described, where a non-hydrotalcite type (or hydrotalcite type) compound is thermally treated and afterwards hydrated to form hydrotalcite type compounds, thus obtaining properties (such as: greater hardness, and/or density) differing from those of hydrotalcite type compounds synthesized by methods reported in the prior state-ofthe-art, where non-hydrotalcite type materials (or hydrotalcite type compounds) are not thermally treated in a similar manner or hydrated for forming such hydrotalcite type compounds.

Hydrotalcite type compounds, also called: double or triple laminar metal hydroxides or anionic clays, are materials with laminar structrue represented by the following formula:

CA 02562014 2006-10-02 [Μ(ΙΙ)ι.χΜ(ΙΙΙ)_χ(ΟΗ)₂](Α_χ) .mH₂O where:

M(ll), represents a divalent cation.

M(lll), represents a trivalent cation.

A, represents any anion.

Metals form octahedrons joining their edges to form positively charged bidimensional sheets. The positive residual charge is originated in the metal or trivalent cation. To neutralize this residual charge, it is necessary for there to be anions located among the sheets, which may be exchanged by others of chemical composition different from the initial one. Due to the polar and hydrophilic nature of the sheets and depending on the space vacated by the anions, a certain amount of water may be accommodated among the anions and among the sheets.

Specialists in this field will notice that anionic clays are commonly called “mixed metal hydroxides.” This expresion is derived from the fat that, such as was indicated previously, the positively charged sheets of the metal hydroxides may contain two diverse metal cations in different oxidation states (for example, Mg²⁺, Al³⁺, and so forth). Additionally, and given that the X-ray difraction patterns of so many anionic clays are similar to the mineral named hydrotalcite, Mg₆AI₂(OH)-|₆(CO3)-4H₂O, it is common for them to be called “hydrotalcite type compounds.” This term has been broadly used in the literature of scientific articles and patents during many years (See for example: Pausch “Synthesis of Disordered and Al-Rich Hydrotalcite-Like Compounds”, Clays and Clay Minerals, Vol. 14, 507-510 (1986). Such compounds

CA 02562014 2006-10-02 are frequently referred to as “Anionic clays.” In fact, the terms “Anionic clays”, “Mixed metal hydroxides” and Hydrotalcite type compounds” are very closely related, if not used indistinctly. On the other hand, USA patent 5,399,329 contains the following sentence: The term “hydrotalcite type” is recognized in its field, defined and used consistently with the use comprised in the monograph type revision articles referred to by Cavani and col.” Therefore and for the purposes of this patent, the autores will use (unless otherwise indicated) the compound term(s) “hydrotalcite type” in the understanding that this term should be considered inclusive of anionic clays; the hydrotalcite itself, as well as any member of the class of materials known as “Hydrotalcite-type compounds.” What is more, and due to its frequent use in this document, the authors will continue to abbreviate the term “hydrotalcite-type” as “HT.”

It is also known that HT’s are decomposed in a predictable manner when heated without exceeding certain temperatures. The resulting materials from decomposition may be re-hydrated (and optionally, re-supplied with certain anions, e.g. CO3=, removed during heating); and likewise, the original HT or a similar one may be reproduced. Products from the decomposition of such heating are frequently referred to as “collapsed” or “meta-stable hydrotalcite type compounds. If these collapsed or meta-stable materials, however, are heated at certain temperatures higher than 1023K, then the products of the decomposition of such HT’s cannot be re-hydrated and/or reconstituted anymore. Therefore, they cannot rebuild the original HT.

Such termal decomposition process of hydrotalcite type compounds has been studied in detail in academic and patent literature. For example, Miyata, “Physico-Chemical

CA 02562014 2006-10-02

Properties of Synthetic Hydrotalcites in Relation to Composition”, Clays and Clay

Minerals, Vol. 28, 50-56 (1980).

One of the most difficult problems to solve when wishing to prepare ternary or multimetallic hydrotalcites, in which the three or more cations have actually been incorporated into the laminar structure, is the fact that depending on the chemical nature of the cation, its precipitation speed may be different from that of the other cations, assuming a constant pH. If the precipitation speeds are very different among themselves, non-hydrotalcite separate crystallographic phases will be obtained, that is, the three cations may not be incorporated uniformly into the hydrotalcite layers. If the situation is complicated when we have a binary system (two cations) due to the aforementioned reasons, the situation becomes even more complicated when we have three or more. Therefore, it is difficult to obtain ternary hydrotalcites whose crystallographic phases show that they are pure within an ample range of compositions of the three cations. Even so, there are some reports demonstrating it is possible to obtain them (J. Sanchez-Valente, Doctoral Thesis, “Synthèse et Characterisation des solides du type hydrotalcite et leurs applications en Catalyse’’ IRC, Francia 1999., M. Sânchez-Cantù, Bachelor’s Degree Thesis IMP, March 2002).

In scientific literature there are some examples of ternary hydrotalcites, that is, those made up in their laminar composition of three different cations. However, these examples are scarce, since a greater effort has been devoted to the study of binary hydrotalcites. For example, Kooli and col. (1995) have reported the preparation of NiAl-Cr and Ni-AI-Fe hydrotalcites containing carbonate anions in their interlaminar

CA 02562014 2006-10-02 region. These ternary hydrotalcites, where the traditional trivalent cation (Al³⁺) is partially substituted by Fe³⁺ or Cr³⁺ cations, were obtained by means of a coprecipitation with sodium carbonate and sodium hydroxide at a ph=10, at 333K, followed by a hidrotermal treatment at 423K. The ternary hydrotalcites were obtained in pure crystallographic phases when the following atomic relationship ranks were maintained between the cations: 3.6 &lt; Ni/(Cr+AI) &lt; 6.8 or 2.3 &lt; Ni/(Fe+AI) &lt;9.9; beyond these ranks other non-hydrotalcite phases were detected.

The foregoing group of authors (F. Kooli and col., 1995) have also described the preparation of ternary hydrotalcites where the divalent cation is partially substituted by others, for example Mg-Zn-AI and Zn-Cu-AI. In this procedure, the solids are obtained by means of co-precipitation with sodium carbonate and sodium hydroxide at 333K and pH=10. The atomic relationships between which it is possible to obtain crystallographically pure hydrotalcite phases were the following: 1.3 &lt; (Mg+Zn)/AI &lt; 5.9 and 2.7 &lt; (Zn+Cu)/AI &lt; 3.1; however, even within these ranks there were occasional non-hydrotalcite phases.

Cu-Ni-AI ternary hydrotalcites, where the divalent cation is partially substituted by another one and with carbonate and nitrate anions in the interlaminar region, have been obtained by means of co-precipitation with an aqueous solution of NaOH, at pH=10 and room temperature, as is reported by A. Alejandre and col. (2001). The precipitate obtained was aged at 343K during 2 h. However, in the case of these ternary hydrotalcites, where Cu is from 0.11 to 0.32, Ni is 0.15 to 0.36 and Al is constant and equal to 3, that is, in order to maintain a divalent / trivalent cation atomic

CA 02562014 2006-10-02 relationship =0.16, their difraction patterns always show different phases from those of hydrotalcite, or mixtures of such phases.

CA 02562014 2006-10-02

BRIEF DESCRIPTION OF THE DRAWINGS

In order to show the performance as SO₂ absorbers of the multimetallic oxides obtained from hydrotalcite type compounds, reference is made to the figures herein included.

Figures 1 to 4 show the X-ray difraction patterns ofthe solids synthesized in this invention, which are characteristic of pure hydrotalcite type compounds, where the formation of crystalline phases additional to the hydrotalcite type structure is not observed, thus indicating that with the procedure of this invention it is possible to incorporate three, four or more cations on the sheets of the hydrotalcite type materials.

Figure 5 represents the plan of the gravimetric evaluation process of solids in the oxidation-reduction of SO₂. This method allows us to compare and discriminate the oxidizing-reducing properties of the solids subject matter of this invention and commercial ones.

Figures 6 to 10 exemplify the gravimetric study of the absorption-reduction process of SO₂, described previously, in multimetallic oxides obtained as of the calcining, at 923 K, ofthe precursor multimetallic hydrotalcites.

DETAILED DESCRIPTION OF THE INVENTION

This invention is related to a procedure for obtaining a series of mixed multimetallic oxides derived from hydrotalcite type compounds and their use as absorbent materials, capable of being regenerated, to remove or reduce the sulfur oxides (SOx) contained in gas currents, preferably in combustion gases emitted by

CA 02562014 2006-10-02 the regeneration section of the fluid catalyst disintegration process (FCC). The syntheses of absorbent materials or multimetallic hydrotalcite type compounds of this invention are represented by the following formula.

[M(ll) ^.y-z M(ll)’_x M(lll)_y M(lll)'_z (OH)₂](Aⁿ'y_+z/_n)-mH2O₎ where: [M(II)+M(II)’J I [(M(lll)+M(lll)’], is the molar relationship between the divalent cations and the trivalent cations and is found between 0.5 and 10 ; M(ll), represents an element of group 2, 6- of the periodic table with valence equal to two; M(ll)', represents an element of group 2, 6-12 of the periodic table with valence equal to two or three, and this may be equal to M(ll) but with a different valence, M(lll), represents an element of group 4-8, with valence equal to 3 and different from M(ll) y M(ll)', M(lll), represents an element of group 4-8, 13 with valence equal to 3 and different from M(ll) and M(lll) or equal to M(lll) but with different valence.

A, represents any anion located between the sheets comprised of the aforementioned cations.

n- , represents the negative electronic charge of the interlaminar anion and may be from -1 to -8.

x= 0.01 up to 0.99 y=0.01 up to 0.99 z=0.01 up to 0.99

The procedure subject matter of this invention is characterized in that it is performed as follows: (1) Preparation of aqueous or organic solutions containing at least three or up to four cations, where the precursor compounds may be oxides, hydroxides, chlorides or any combination of them; (2) preparation of the alkaline solutions from 0.5 to 10 molar, preferably from 1 to 5 molar of KOH, K₂CO3,

CA 02562014 2006-10-02 (NH₄)OH, (NH₄)₂CO₃, Urea or any alkaline compound, different from sodium, or any combination of them; (3) a combination of solutions 1 and 2 until precipitation of the cations in the form of hydroxides is caused; (4) mechanic agitation at temperatures between 293 and 373K from 14 to 20 hours; (5) washing of the precipitate with enough water to eliminate the non-precipitated ions; (6) drying with air, oxygen or nitrogen current or any combination of them; (7) Finally, calcining of the obtained material is effected, between 673K and 1073K, preferably from 850K to 950K in air atmosphere during 4 hours.

The solids obtained with different concentrations of metallic cations in their laminar structure are classified in the series named: MgFeAl, MgZnAI, MgNiAl and MgZnAIFe; and in some cases binary hydrotalcites were prepared (MgAI, ZnAI, MgFe, and so forth) to compare them with the multimetallic ones subject matter of this invention. Material characterization techniques involve the determination of important parameters, such as surface area, pore diameter, pore volume, structural arrangements, crystallinity, crystalline phase composition, sulfur absorption and thermal analysis.

The elementary analysis for calculating the developed formula of the multimetallic hydrotalcites was effected by atomic absorption, X-ray analysis in a diffractometer with CuKa radiation (1.5406 Â) to identify the crystallographic phases of the solids and the textural properties in an equipment, ASAP, at 77 K by means of the adsorption-desorption of nitrogen.

CA 02562014 2006-10-02

The materials obtained presented the patterns of X-ray difraction characteristic of the pure multimetallic hydrotalcites subject matter of this invention, as shown in Figures 1 to 4; where the formation of compounds additional to the hydrotalcite type structure is not observed, and by this we wish to indicate that with the procedure of this invention it is possible to incorporate three, four or more cations on the sheets of hydrotalcite type materials. It is also demonstrated that the hydrotalcites, constituted by three or more cations in their laminar structure, are converted after being calcined between 673 and 973K, into materials with improved basic properties in comparison with a hydrotalcite constituted of only two cations.

It is important to emphasize that the product of calcining a conventional binary hydrotalcite, for example, Mg/AI, may function as an absorbent material for SO_X in gas currents, the removal of the sulfites or sulfates formed, or in other words, the regeneration of the absorbent material, becomes difficult due to the fact that the sulfates are strongly interlocked to the material mentioned. Hence, we need a third or up to a fourth highly disperse cation, forming part of the layers of the initial hydrotalcite, to modulate the basic strength of the sites where SOx acid molecules interact and/or which they capture.

This invention demonstrates that the reduction speed (that is, the removal of sulfates of absorbent matrial) increases considerably in calcined ternary or quaternary hydrotalcites. This parameter is crucial for the commercial utilization of these materials as SOx reducing additives in the FCC process, since contact times are usually between close to 2 to 5 seconds with reducing gases. The latter are the hydrocarbons and/or oxygen involved in the FCC process.

CA 02562014 2012-08-30

Microcalorimetric procedure to measure the heat emitted or absorbed in the hydrotalcites in CO₂ adsorption.

To measure the heat emitted or absorbed in the materials subject matter of this invention, a flow isothermal calorimeter of the Tian-Calvet type was used: The procedure is performed as follows: (a) All hydrotalcites obtained according to examples 1 to 24 were thermally treated at 723K during 5 hours, under a flow of nitrogen of 7 L/h, with a temperature ramp of 10 K/min. (b) The materials were placed inside the microcalorimetric cell, by using a glove bag in an argon atmosphere, in order to avoid contact of the solid with the air and consequently its de-activation, (c) Afterwards, the cell was heated in the pretreatment oven, until the necessary vacuum was reached to initiate the experiment (10-5 Torr), (d) Later, this was carried on to room temperature by keeping the vacuum in the cell, which was transferred to the microcalorimeter (Tian-Calvet™ Home-Made at IRC Lyon, France), e) Afterwards, successive dosages of CO₂ of a known volume were sent to the study sample, thus awaiting thermal equilibrium after every dosage. The pressure was determined with an absolute pressure meter (BARATRON™ MKS Instruments), until there was a residual equilibrium pressure of the order of 0.14 Torr.

Results of CO₂ adsorption.

On Table 1 we present the results of CO₂ adsorption in the calcined hydrotalcites, and these were previously treated according to the protocol described in the preceding experimental part. CO₂ is an acid gas molecule and it is adsorbed

CA 02562014 2006-10-02 only on the basic sites. To examine the effect of the different metallic cations on the solid basic quality, and at the same time the effect of the precursor salts of the metallic cations on the basic properties of the same, the samples were studies starting with nitrates and chlorides with different cations. The samples synthesized as of chlorides were exchanged by following the anionic exchange protocol described in this process. It is important to mention that the solids obtained from chlorated salts without being exchanged practically do not adsorb CO₂, and this indicates that the active basic sites are inhibited by the presence of chlorine.

An important result of this study, in the case of hydrotalcites containing only Mg and Al, is that there is almost no difference whatsoever between the number and the strength of basic sites, obtained starting either with nitrated or chlorated salts. On the other hand, in the case of hydrotalcite type compounds (HT), containing either Mg and/or Fe and/or Ni and/or Cu and/or Zn and/or Cr, there is a considerable difference between the solids obtained as of nitrates or chlorides. Solids synthesized as of chlorides present greater CO₂ adsorption enthalpies, and this indicates they are compounds of a greater strength and number of basic sites than those obtained starting with nitrates: When chlorated salts are used, the number of sites oscillates between 0.5-3.0 umol CO₂ adsorbed/m² with adsorption enthalpies comprised within a range of 60-120 KJ/mol, the number and strength of sites of the calcined solids will be determined by the nature and proportion of the cations present in the structure of the precursor HT type compound. Also varying the composition of the precursor HT, it is possible to obtain solids with a number of sites going from 0.4-1.5 pmo! CO₂ within

CA 02562014 2006-10-02 a range of ΔΗ adsorption: 60-110 KJ/mol. These results show that the number and strength of the active basic sites may be modulated within an ample gamut of energy.

Table 1. Microcalorimetric results of CO₂ adsorption on calcined hydrotalcite-like compounds (923K/4 h).

<td> Sample</td><td> pmolCO₂/m²*</td><td> ΔΗ (KJ/mol)</td>

<td> [Mgo.7i4Feo.io7Alo. ι7θ(ΟΗ)₂] (CO3)q₁₄₃ Ό.83 H₂0</td><td> 1.5</td><td> 60-110</td>

<td> [Mgo.65lFeo.063Alo 286(OH)₂] (003)0174-0.82 H₂0</td><td> 1.1</td><td> 60-100</td>

<td> [Mg₀ 704Fe₀.i92AI₀₁04(OH)2] (CO/io.us Ό.92 H₂0</td><td> 1.3</td><td> 60-105</td>

<td> [Mgo.493Zn_o 165AI0.342(0^1)2)(003)0.171 0.98H₂0</td><td> 0.8</td><td> 60-100</td>

<td> [Mgo.47₈Zn₀.₂₃2Alo.₂9o(OH)₂](C03)₀₁45O.86H₂0</td><td> 0.6</td><td> 60-95</td>

<td> [Mgo.segNio iiiAIo3oo(OH)₂] (COs)o 150'0.88H₂0</td><td> 1.3</td><td> 60-110</td>

<td> [Mgo 457Nio 292Alo.25l(OH)₂] (C0₃)o 1₂6'0.85H₂0</td><td> 1.0</td><td> 60-90</td>

<td> [Mg₀ 658CUo 098AIq.244(OH)₂] (CO₃)₀ i₂₂-0.69H₂0</td><td> 0.9</td><td> 60-80</td>

<td> [Mg₀,i7Nio,5iAI_0i32(OI-l)2](C03)o,i6· 0,91 H₂O</td><td> 1.3</td><td> 60-110</td>

<td> [Mgo 744Al₀.2₅₆(OH)₂](C03)o 128'0.85H₂0</td><td> 1.2</td><td> 60-100</td>

<td> [Mg₀.730 Alo.270 (ΟH)2] (003)0.135 0.71 H₂O**</td><td> 1.4</td><td> 60-100</td>

<td> [Mgo.688Fe_O.31 i(OH)₂] (COsjo.160 Ό.8ΟΗ2Ο</td><td> 0.5</td><td> 60-100</td>

<td> [Mgo.67o Fe_o.33o (OH)₂) (C0₃)o165 0.80 H₂O**</td><td> 2</td><td> 60-100</td>

<td> [Mg₀,₆9Cr₀,3i(OH)₂](C03)o,i73 0,84H₂O</td><td> 0.4</td><td> 60-105</td>

<td> [Mg 0,76 Ofo.24 (014)2] (C0₃)o,120 · 0,79 H₂O**</td><td> 3.5</td><td> 60-120</td>

<td> [COo,63 Alo,37 (OH)₂](C0₃)o,185 · 1,1 H₂O</td><td> 0.48</td><td> 60-80</td>

<td> [CUo,751 AIo,249 (ΟΗ)2](00₃)ο,418. 1,41 H₂O</td><td> 1.5</td><td> 60-78</td>

<td> [Nio 833AIo.167(OH)₂] (C0₃)o 0835'0.68H₂0</td><td> 0.8</td><td> 60-90</td>

<td> [Zrio 75AI0.25(014)2] (C0₃)o. 125'0.84H₂0**</td><td> 0.5</td><td> 60-96</td>

*Only the CO₂ adsorbed amount &gt;60 KJ/mol was considered as a real chemisorption.

**This solids were synthesized from chloride salts and exchanged post-synthesis with CO₃anions.

CA 02562014 2012-08-30

Evaluation of multimetallic hydrotalcites in the oxidation-reduction of SO₂.

By means of this method, the absorption-reduction efficiency was determined in the multimetallic hydrotalcites of this invention, of sulfur oxides (SOx), by means of thermo-gravimetric analysis. The temperature interval of every test was performed from the room temperature up to 923K. The temperature employed depended on the absorption-reduction properties of the materials studied.

The analysis equipment consists of the following:

• Perkin-Elmer thermo-gravimetric analyzer, Perkin Elmer TGA-7™ model: This consists mainly of an ultrasensitive microscale, measuring weight changes from 0.1pg up to 1300 mg; and of a high temperature oven, whose operation range is from 298 to 1773K, and thus an excellent accuracy is obtained.

• Perkin Elmer TAC 7/DX™ thermal analysis controlling instrument.

• Manual set of valves for the processes of oxidation-reduction absorption and cleansing of the system.

To evaluate the hydrotalcites, 40-60 mg was taken from the samples presented on Table 2, and these were transferred to a temperature of 923 K in an air atmosphere in order for them to be activated and stabilized. The absorption of SO₂ in the material is effected by exposure to a mixture of SO₂ (1.0% Vol.)/air at the same temperature. Once total saturation has finished, the system is purged with N₂. Immediately following, the sample is reduced with a current of H₂ at 823 and 923K, thus obtaining again the initial calcined hydrotalcite, and this may be submitted to a new absorption-reduction cycle. With this test the total adsorption capacity is

CA 02562014 2006-10-02 determined, as well as the adsorption speed and reduction speed, besides the material stability in several absorption cycles (Figure 5).

Some results with this evaluation method are presented in Figures 6 to 10.

With this test, the following parameters are determined:

• Total Absorption: The maximum amount of SO₂ (% weight) absorbed until reaching equilibrium at a given time (the latter depends on the sample studied).

• Absorption speed: Amount of SO₂ (% weight) absorbed per time unit, calculated for all cases after 30 minutes.

• % Reduction: Amount of SO₂ reduced at a given temperature (823 or 923 K).

• Reduction speed: Amount of SO₂ (% weight) absorbed per time unit at 823 and/or 923 K.

• Catalytic Stability: Intrinsic capability of the solid to recover its initial absorption capacity.

The results of these tests are summarized on Tables 2 and 3.

From the above described parameters, one of the most important and crucial ones for optimal performance of the additives in actual operation conditions is the reduction speed, since it is limited by the temperature of the riser reaction zone (its acronym in English) of the FCC process, and this oscillates between 793 and 873 K. Consequently, solids that present a greater reduction speed at temperatures situated within this range are better than those that need greater activation temperatures. From the results of Table 2, it is demonstrated that said speed may be modulated depending on the nature and content of the metallic cations constituting the solid,

CA 02562014 2010-09-08 thus obtaining results up to 9.7 times greater when compared with the better ones obtained in commercial additives, evaluated under the same conditions.

On Tables 2 and 3, it is demonstrated that the reduction speeds at 823 K of the ternary hydrotalcites with iron (series MgFeAl) are (between 9.7 and 14.7 times) faster than that of the binary MgAI hydrotalcite or that of commercial additives. The amount of SO2 in % weight that the MgFeAl ternary series of hydrotalcites can absorb is from 1.1 to 2.7 times greater than that of the best of the commercial additives (Additive C). This means that in one application lesser amounts of multimetallic hydrotalcite will be required, subject matter of this invention, in order to offer the same SO₂ absorption levels, thus contributing to the economy of the process. Additionally in this same series, the SO2 absorption speeds, although they are not so crucial as the SOx reduction speeds, as was explained previously, improve 1.3 and 2.0 times in comparison with the best of the additives (Additive C).

From the results on Table 3, it may be observed that the MgFeAl multimetallic hydrotalcite series has between 83 to 94% reduction at 823 K, whereas the additives have only between 20 to 29% at 823 K. Commercial additives need greater temperatures (923 K) to reach elevated reduction levels.

The MgZnAI multimetallic hydrotalcite series presented reduction speeds between 1.2 and 3.4 times greater than the MgAI binary hydrotalcite or commercial additives, although lower than the MgFeAl series, as is shown on Table 2. The absorption speeds were between 0.9 and 1.8 times grater than the best of the commercial additives (Additive C) and their capturing capacities were from 0.67 to 2 times better than the best of the commercial additives (Additive C).

CA 02562014 2006-10-02

In general, from Tables 2 and 3, it is clear that the type and amount of ternary cation has a positive impact on most of the evaluation parameters in order to be able to determine whether or not an SO_X absorbent is good.

CA 02562014 2006-10-02

Table 2. Total absorption and absorption-reduction rates of SO2 oxo-reduction test on calcined HT’s (923K/4h).

<td> Sample</td><td> Total Absorption* (%Wt SO₂/m²)</td><td>¹Absorption rate (1/min)</td><td colspan="2"> Reduction rate (1/min)</td>

<td></td><td></td><td></td><td> 823K</td><td> 923K</td>

<td> [Mgo.65iF^eo o63Alo.286(OH)₂] (COgjo 174 Ό.82 H₂O</td><td> 10</td><td> 1.44</td><td> 2.13</td><td> 0.10</td>

<td> [Mgo 71₄ΡθΟ I07AI0 i7g(OH)₂] (COgjo 143 Ό.83 H₂O</td><td> 13</td><td> 1.52</td><td> 2.13</td><td> 0.26</td>

<td> [Mg₀ 704^60192AI0 104(OH)₂] (C0₃)o 148'0 92 H₂O</td><td> 25</td><td> 2.24</td><td> 2.72</td><td> 0.49</td>

<td> [Mgo.6ioZno.o9oAI_{0 2}9o(OH)₂](C0₃)o. 15'0-73 H₂O</td><td> 6</td><td> 1.02</td><td> 0.27</td><td> 1.65</td>

<td> [Mgo.493Zn_o.i65Alo 342(OH)₂](C0₃)o 171 Ό.98 H₂O</td><td> 11</td><td> 1.97</td><td> 0.68</td><td> 1.79</td>

<td> [Mgo.487Zno.₂oiAlo.3i2(OH)₂](C0₃)o 156'0.90 H₂O</td><td> 14</td><td> 1.94</td><td> 0.72</td><td> 1.90</td>

<td> [Mgo ₄7δΖηο 232AI0 29o(OH)₂](C0₃)o 145Ό.86 H₂O</td><td> 18</td><td> 1.88</td><td> 0.74</td><td> 1.97</td>

<td> [Mg_{0 58}gNio.iiiAlo.30Q(OH)2] (C0₃)o 150'0.89 H₂O</td><td> 4</td><td> 1.08</td><td> 0.41</td><td> 1.47</td>

<td> [Mg₀ 483Nio 222AI0,295(0H)₂] (C0₃)o 147 Ο.88 H₂O</td><td> 7</td><td> 1.14</td><td> 0.89</td><td> 1.43</td>

<td> [Mg₀457N10,292Alo.25i(OH)₂] (C0₃)o.126'0.85 H₂O</td><td> 2</td><td> 0.56</td><td> 0.30</td><td> 0.43</td>

<td> [Mg₀ 307CUo.118Alo.578(OH)₂] (C0₃)o.289'θ·θθ H₂O</td><td> 4</td><td> 1.69</td><td> 0.15</td><td> 0.44</td>

<td> [Mgo658CUo.098Alo 244(OH)₂] (C0₃)o 122'0.69 H₂O</td><td> 2</td><td> 1.29</td><td> 0.17</td><td> 0.42</td>

<td> [MgosoqCUo ΐ4βΑΙο 252(OH)₂] (CO₃)q 126'O.71 H₂O</td><td> 2</td><td> 1.30</td><td> 0.21</td><td> 0.21</td>

<td colspan="5"> Binary hydrotalcites and Commercial Additives***</td>

<td> [Mg₀ 744AI₀.256(OH)₂](CO₃)₀.128'0.85 H₂0</td><td> 24</td><td> 3.42</td><td> 0.22</td><td> 1.41</td>

<td> [Mgo.688Feo.3ii(OH)₂] (C0₃)o 160 0.80 H₂O</td><td> 27</td><td> 3.44</td><td> 3.25</td><td></td>

<td> [Zn₀.₇₅A)₀.₂₅(OH)₂] (C0₃)o,125'0.84 H₂O</td><td> 35</td><td> 1.78</td><td> 1.10</td><td> *★</td>

<td> [Nio 833AI0 167(OH)₂] (C0₃)o.0335'0.68 H₂O</td><td> 3</td><td> 0.25</td><td> 1.15</td><td> **</td>

<td> Commercial Additive A</td><td> 7</td><td> 0.98</td><td> 0.22</td><td> 1.60</td>

<td> Commercial Additive B</td><td> 8</td><td> 1.02</td><td> 0.21</td><td> 1.26</td>

<td> Commercial Additive C</td><td> 9</td><td> 1.09</td><td> 0.21</td><td> 1.73</td>

Evaluated at 923K **The samples were completely reduced at 873 K, ¹ In all cases, the rate was measured at 30 min. Commercial catalyst A is mainly constituted of MgAI₂O₄, commercial catalysts B and C are made with hydrotalcite doped with Ce and V. *“ Binary hydrotalcites and commercial additives were only used as references and they are not object of this patent request.

CA 02562014 2010-09-08

Table 3. Total absorption, regeneration and reduction percentage of SO2 oxoreduction test on calcined HT’s (923K/4h).

<td> Sample</td><td> Total Absorption * (gSOj/gcat)</td><td colspan="2"> Reduction (%)</td><td> Regeneration (%)</td>

<td></td><td></td><td> 823K</td><td> 923K</td><td></td>

<td> [Mgo.65lF^e0.063Alo.286(ÛH)2] (C03)o17₄ 0.821 H2O</td><td> 1.031</td><td> 94</td><td> 6</td><td> 98</td>

<td> [MgojuFeojoiAlon^OHJal (CO₃)₀.i₄3 -0.828 H2O</td><td> 1.013</td><td> 92</td><td> 8</td><td> 100</td>

<td> [Mgo.7o₄Feo.i92Alo.io4(OH)₂] (C03)oj₄8-0.920 H₂0</td><td> 1.145</td><td> 83</td><td> 17</td><td> 98</td>

<td> [MgoeioZnoogoAloWOHjzKCO^o.! s’ 0.73H₂O</td><td> 0.774</td><td> 14</td><td> 86</td><td> 55</td>

<td> [Mgo.493Zno.₁65Alo.34₂(OH)2](C0₃)o.i7i0.978H₂0</td><td> 0.836</td><td> 30</td><td> 64</td><td> 32</td>

<td> [Mgo.₄87Zno.2oiAlo.3i2(OH)2](C03)o.i56’0.902H₂0</td><td> 0.881</td><td> 30</td><td> 65</td><td> 41</td>

<td> [Mgo.₄78Zno.232Alo.29o(OH)₂](C03)o.145-0.857H₂0</td><td> 0.918</td><td> 29</td><td> 67</td><td> 43</td>

<td> [Mgo.589Nio.iiiAlo.3oo(OH)2] (C03)oi5oO.885H₂0</td><td> 0.656</td><td> 30</td><td> 66</td><td> 104</td>

<td> [Mgo.483Nio.222Alo.295(OH)2] (C03)o.-|47O.876H₂0</td><td> 0.842</td><td> 42</td><td> 55</td><td> 104</td>

<td> [Mgo.457Nio.292Alo.25l(OH)₂] (C03)o.126'0.849H20</td><td> 0.293</td><td> 54</td><td> 44</td><td> 134</td>

<td> [Mgo,3O7CUo.ll8Alo.578(011)2] (00₃)ο.289·0.803Η20</td><td> 0.377</td><td> 16</td><td> 46</td><td> 168</td>

<td> [Mgo 658Cuo.o9eAlo.244(OH)2] (C0₃)o₁₂2'0.687H20</td><td> 0.309</td><td> 21</td><td> 49</td><td> 154</td>

<td> [Mgo60oC^u0.148Alo.252(OH)₂] (CO3)₀₁26 0.709H20</td><td> 0.227</td><td> 33</td><td> 36</td><td> 202</td>

<td colspan="5"> Binary Hydrotalcites and Commercial Additives**</td>

<td> [Mgo.744Alo.256(OH)2](C03)o.₁280.850H₂0</td><td> 1.214</td><td> 9</td><td> 52</td><td> 96</td>

<td> [Mgo.688FeQ.₃₁₁(OH)2] (C0₃)q.i6o Ό.8ΟΟΗ2Ο</td><td> 1.050</td><td> 96</td><td> 4</td><td> 102</td>

<td> [Zn₀ 75Alo.25(OH)₂] (C03)o.i25-0.840H₂0</td><td> 0.666</td><td> 82</td><td> 5</td><td></td>

<td> [Nio.833Alo.167(OH)2] (C0₃)o.0835 0.683H₂0</td><td> 0.294</td><td> 100</td><td> 0</td><td> _***</td>

<td> Commercial Additive A</td><td> 0.644</td><td> 26</td><td> 73</td><td> 100</td>

<td> Commercial Additive B</td><td> 0.550</td><td> 29</td><td> 68</td><td> 114</td>

<td> Commercial Additive C</td><td> 0.665</td><td> 20</td><td> 80</td><td> 109</td>

‘Evaluated at 923K “ Binary hydrotalcites and commercial additives were only used as references and they are not object of this patent request ‘“The activity was not regenerated at all. The regeneration is 5 calculated from a second absorption cycle. Commercial additive A is mainly constituted of MgAI₂O₄, commercial additives B and C are made with hydrotalcite doped with Ce and V.

CA 02562014 2006-10-02

To conclude, as if deriving from the results of Tables 2 and 3, it is possible to state that a third or up to a fourth cation on the sheets of the multimetallic hydtrotalcites offers a modulating function between the basic strength necessary to retain the SO_X and its commitment to loosen this molecule at relatively low temperatures and to regenerate the material.

It is important to emphasize that the product of calcining a conventional binary hydrotalcite, for example, constituted by magnesium and aluminum, may function as an absorbent material of SOx in gas currents. Removal of the sulfites or sulfates formed, or in other words the regeneration of the absorbing material, is rendered difficult due to the fact that the sulfites or sulfates are strongly interlinked to the material mentioned. Therefore, it is important for the hydrotalcites to contain a third or up to a fourth highly disperse cation, forming part of the layers of the initial hydrotalcite, to modulate the basic strength of the sites where SOx acid molecules interact and/or which they capture. In this invention, it is demonstrated that the reduction speed (that is, the removal of sulfates from the absorbent material) increases considerably in calcined ternary or quaternary hydrotalcites. The reduction speed is crucial for the commercial utilization of these materials as SO_X reducing additives in the FCC process, since contact times are usually between close to 2 to 5 seconds with reducing gases. The latter are the hydrocarbons and/or hydrogen involved in the FCC process.

The following examples will illustrate a few of the aspects described in this invention. These examples, however, should not be used to limit the sphere of this

CA 02562014 2006-10-02 invention, since there are many variations that can be derived without distancing ourselves from the topic of this invention.

Co-precipitation methods, at low and high superaturation for obtaining the HT’s compounds, were employed. The selection of one method or the other will be determined, in some cases, by the nature of the cations to be precipitated. The pH optimizations and the ageing time of the solids permit to obtain well crystallized solids.

a) Co-precipitation at low supersaturation.

In co-precipitation at low supersaturation, at a constant pH, the most commonly used conditions are the following: pH rank from 7 to 10, temperature from 333 to 353 K, low concentration of reagents and a slow addition speed for the cation solution and the alkaline solution. The precipitate obtained is given an ageing time under the conditions of co-precipitation, and this induces the dissolution of the small crystals and the growth of the large ones. Afterwards the solid is washed with hot water and finally dried at a temperature generally not exceeding 393K.

b) Co-precipitation at high supersaturation.

The main difference between this method and the foregoing one is that in this one the metal solution is added to the alkaline solution within a relatively short time (only the final precipitation pH is controlled). This method generally gives rise to less crystalline materials than those obtained by the low supersaturation method, due to the fact that in this case the nucleation speed is comparable to the speed of growth of the crystals.

CA 02562014 2006-10-02

EXAMPLES

Preparation of the MgFeAl series .

Hydrotalcite type solids with the developed formula [Mgi__y._z Fe_y Al_z (OH)₂]^X+ (Aⁿ' y+^,)^x'-mH20, were prepared by co-precipitation at high supersaturation.

Example 1

Obtaining the hydrotalcite with the developed formula [Mgo.714 Feo.107 AI0.179 (OH)₂] (00₃)ο.ΐ43 -0.828 H₂O, was carried out in the following manner: First an aqueous solution (A) was prepared with 49.06 g of Mg (ΝΟ₃)₂·6Η₂Ο, 13.28 g de ΑΙ(ΝΟ₃)₃·9Η₂Ο and 11.49 g Fe(NO₃)₃*9H₂O in 250 cm³ water. On the other hand, an alkaline solution was prepared (B), containing 23.27 g of K₂CO₃ and 22.00 g of KOH in 250 cm³ of water. The (A) solution was added to a glass reactor, the (B) solution began to drip slowly until it reached a final pH of 9. The solution obtained was kept under mechanical stirring at a temperature of 353K during 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (333-353K) during enough time to eliminate excess ions. Drying was performed at a temperature of 373 K during 24 h.

Example 2

Synthesis of [Mgo.704 Feo.192 Al_o.io4 (OH)₂] (C0₃)o.i48 O.920H₂O. An aqueous solution (A) was prepared with 49.06g of Mg(NO₃)2*6H₂O, 7.50g of ΑΙ(ΝΟ₃)₃·9Η₂Ο and 17.77g

CA 02562014 2006-10-02 of Fe(NO₃)₃«9H₂O in 250 cm³ of water. On the other hand, an alkaline solution (B) was prepared, containing 23.27 g of K₂CO₃ and 22.00 g of KOH in 250 cm³ of water. Solution (A) was added to a glass reagent, solution (B) began to drip slowly until it reached a final pH of 9. The solution maintained was kept under vigorous mechanical stirring, at a temperature of 353 K for 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (353 K) during enough time to eliminate excess ions. Drying took place at a temperature of 373K during 24 h.

Example 3

Synthesis of [Mgo.65i Fe0.063AI0.286 (OH)₂] (CO₃)₀.i74 Ό.821 H₂O. An aqueous solution (A) was prepared with 98.12g of Mg(NO₃)₂*6H₂O, 37.47g of ΑΙ(ΝΟ₃)₃·9Η₂Ο and 11.20g of Fe(NO3)₃*9H₂O in 500 cm³ of water. On the other hand, an alkaline solution (B) was prepared, containing 46.48g of K₂CO₃ and 44.03g of KOH in 500 cm³ of water. Solution (A) was added to a glass reagent; solution (B) began to drip slowly until it reached a final pH of 9. The solution obtained was kept under vigorous mechanical stirring, at a temperature of 353 K for 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (353 K) during enough time in order to eliminate excess ions. Drying took place at a temperature of 373K during 24 h.

Table 4 shows the texture properties of the sythesized compounds. Figure 1 exhibits the difraction patterns of these solids, which correspond to a hydrotalcite type structure.

CA 02562014 2006-10-02

Table 4. Developed formula and textural properties of HT’s .

<td> Sample*</td><td> BET Area (m²/g)</td><td> Dp (nm)</td><td> Vp (cm³/g)</td>

<td> [Mgo.65lFeo.063Alo.286(OH)₂] (C0₃)o.174 Ό.82 H₂O</td><td> 206</td><td> 12.36</td><td> 0.782</td>

<td> [MgovuFeo io7Alo.i79(OH)2] (CO₃)q 143 Ό.83 H₂O</td><td> 169</td><td> 9.13</td><td> 0.558</td>

<td> [Mg₀ 7o₄Fe₀19₂AI_O w₄(OH)₂] (C0₃)o.i₄s Ό.92 H₂O</td><td> 124</td><td> 14.30</td><td> 0.603</td>

*Textural properties of calcined samples at 923K in air atmosphere for 4h. Dp: Average pore diameter. Vp: Total pore volume.

Preparation of the MgZnAI series.

These solids, having a general developed formula: [Mg1-x-y Znx Aly (OH)2]X+(An-y/n)X-mH2O, were prepared by the co-precipitation method at low supersaturation.

Example 4

Synthesis of [Mgo.6i4Zno.093 AI0.293 (OH)₂] (C0₃)o.i46-0.731H₂0. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of Mg(NO₃)₂*6H₂O (19.51g), Zn (NO₃)₂ ·6Η2Ο (3.27g) and AI(NO₃)₃ ·9Η₂Ο (10.88g) in 116 cm³. On the other hand, an alkaline solution (Β, 2M) was prepared, containing K2CO3 (18.15g) and KOH (17.22g) in 200 cm³ of H2O. Solutions (A) and (B) were added simultaneously to a glass reactor, containing previously 100 cm³ of de-ionized H₂O, at a controlled pH of 9. The precipitate obtained was kept under vigorour mechanical stirring, at a temperature of 353 K for 18 hours. Afterwards, the final product was washed and filtered with hot de-ionized water (353 K) , enough in order to eliminate excess ions. Drying was carried out at a temperature of 373K for 24 h.

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Example 5

Synthesis of [Mgo.493 Zn₀,i65 AI₀.342(OH)₂] (CO₃)₀.i7r0.978H₂O. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of Mg(NO₃)₂*6H₂O (16.94g), Zn (NO₃)₂ «6H2O (5.35g) and AI(NO₃)₃ ·9Η₂Ο (10.50g) in 112 cm³. On the other hand, an alkaline solution (B, 2M) was prepared, containing K2CO3 (18.15g) and KOH (17.22g) in 200 cm³ of H2O. Solutions (A) and (B) were added simultaneously to a glass reactor, containing previously 100 cm³ of de-ionized H₂O, at a controlled pH of 9. The precipitate obtained was kept under vigorous mechanical stirring, at a temperature of 353 K for 18 hours. Afterwards, the final product was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions. Drying took place at a temperature of 373K for 24 h.

Example 6

Synthesis of [Mg₀.478 Zn₀.₂₃₂ Al₀.₂9o(OH)₂] (CO₃)₀.i45-0.857H₂O. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of Mg(NO₃)₂*6H₂O (14.12g), Zn (NO₃)₂ «6Η2Ο (7.73g) and AI(NO₃)₃ ·9Η₂Ο (10.13g) in 108 cm³. On the other hand, an alkaline solution (B, 2M) was prepared, containing K2CO3 (18.15g) and KOH (17.22g) in 200 cm³ of H2O. Solutions (A) and (B) were added simultaneously to a glass reactor, containing previously 100 cm³ of de-ionized H₂O, at a controlled pH of 9. The precipitate obtained was kept under vigorous mechanical stirring, at a temperature of 353 K for 18 hours. Afterwards, the final product was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions. Drying was performed at a temperature of 373K for 24 h.

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Example 7

Preparation of [Mg₀.487 Ζη₀₂οι AI0.312 (0H)₂] (C0₃)o.i56’0.902H₂0. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of Mg(NO3)₂*6H₂O (15.14g), Zn (NO₃)₂ ·6Η2Ο (6.84g) and AI(NO₃)₃ ·9Η₂Ο (10.13g) in 109 cm³. On the 5 other hand, an alkaline solution (B, 2M) was prepared, containing K₂CO₃ (18.15g) and

KOH (17.22g) in 200 cm³ of H2O. Solutions (A) and (B) were added simultaneously to a glass reactor, containing previously 100 cm³ of de-ionized H2O, at a controlled pH of 9. The precipitate obtained was kept under vigorous mechanical stirring, at a temperature of 353K for 18 horas. Afterwards, the final product was washed and 10 filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions.

Drying took place at a temperature of 373K for 24 h. Table 5 shows the results of the texture analyses of the solids obtained. Figure 2 shows the difraction patterns of these solids, and they correspond to a hydrotalcite type structure.

Table 5. Developed formula and textural properties of HT’s .

<td> Sample*</td><td> BET Area (m²/g)</td><td> Dp (nm)</td><td> Vp (cm³/g)</td>

<td> [Mgo.6i4Zno.o93 Alo 293 (OH)₂] (003)0.146'0.73H₂O</td><td> 175</td><td> 14.2</td><td> 0.480</td>

<td> [Mg₀ 493Zn₀ I65AI0 342(OH)2] (C0₃)o 171'0.98H₂O</td><td> 193</td><td> 16.22</td><td> 0.870</td>

<td> [Mgo487Zno.₂oiAlo.3i2(OH)₂] (C0₃)o 156'0.90H₂O</td><td> 175</td><td> 16.53</td><td> 0.842</td>

<td> [Mgo47sZno ₂₃₂AIo ₂9o(OH)₂] (CO₃)q i45'0.86H₂O</td><td> 139</td><td> 24.35</td><td> 0.925</td>

*Textural properties of calcined samples at 923K in air atmosphere for 4h. Dp: Average pore diameter. Vp: Total pore volume.

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Preparation of the MgNiAl series .

These solids, with the general developed formula: [Mgy._x._y Ni_x Al_y (OH)₂]^X+ (Aⁿ' _y/_n)^x' -mH₂0, were prepared by the co-precipitation method at low supersaturation.

Example 8

Synthesis of [Mgo.589Nio.niAl₀.3oo(OH)₂] (C0₃)o.i5o'0.885H₂0. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of Mg(NO₃)₂*6H₂O (45.69 g), Ni(NO₃)₂ -6H2O ( 3.79 g) and AI(NO₃)₃ -9H₂O (23.92 g) in 250 cm³. On the other hand, an alkaline solution (B, 2M) was prepared, containing K2CO3 (23.26 g) and KOH (20.67 g) in 250 cm³ of H2O. The two solutions (A and B) were mixed by dripping in a glass reactor containing 200 cm³ of de-ionized water; the addition was performed by maintaining a constant pH of 9. The addition time was ± 30 minutes. The precipitate obtained was kept at a temperature of 343 K during 18 h under vigorous stirring; afterwards it was washed/filtered 8 times with hot de-ionized water (333 K). Drying the paste obtained was performed at 373 K during 24 h.

Example 9

Synthesis of [Mgo.483 Nio.₂₂₂ Alo.₂95(OH)₂] (C0₃)o.i47'0.876H₂0. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of Mg(NO₃)₂»6H₂O (42.07 g), Ni(NO₃)₂ -6H2O ( 7.84 g) and AI(NO₃)₃ -9H₂O (23.92 g) in 250 cm³. On the other hand, an alkaline solution (B, 2M) was prepared, containing K2CO3 (23.26 g) and KOH (20.67 g) in 250 cm³ of H2O. The two solutions (A and B) were mixed by dripping in a glass reactor containing 200 cm³ of de-ionized water; the addition was

CA 02562014 2006-10-02 carried out by maintaining a constant pH of 9. The addition time was ± 30 minutes.

The precipitate obtained was kept at a temperature of 343 K for 18 h under vigorous stirring; afterwards it was washed/filtered 8 times with hot de-ionized water (333 K).

Drying the paste obtained was carried out at 373 K for 24 h.

Example 10

Synthesis of [Mgo.457 Nio.292 AI₀.25i(OH)₂] (C03)o.i26^-0.849H20. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of Mg(NO3)2«6H2O (38.25 g), Ni(NO3)2 ·6Η2Ο (12.13 g) and AI(NO3)3 -9H2O (23.92 g) in 250 cm³. On the 10 other hand, an alkaline solution (B, 2M) was prepared, containing K2CO₃ (23.26 g) and KOH (20.67 g) in 250 cm³ of H₂O.The two solutions (A and B) were mixed by dripping in a glass reactor containing 200 cm³ of de-ionized water; the addition was performed by maintaining a constant pH of 9. The addition time was approximately 30 minutes. The precipitate obtained was kept at a temperature of 343 K during 18 h 15 under vigorous stirring; afterwards it was washed/filtered 8 times with hot de-ionized water (333 K). Drying the final product was performed at 373 K for 24 h.

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Table 6. Developed formula and textural properties of HT’s .

<td> Sample*</td><td> BET Area (m²/g)</td><td> Dp (nm)</td><td> Vp (cm³/g)</td>

<td> [Mg₀ 589Nio.iiiAlo.3oo(OH)₂] (CO₃)₀.i5o^-0.89H₂O</td><td> 240</td><td> 6.96</td><td> 0.534</td>

<td> [Mgo 483Nio 222AI0 295(014)2] (00₃)ο.ΐ47·0.88Η₂0</td><td> 251</td><td> 7.23</td><td> 0.604</td>

<td> [Mg₀ 457Nio.292Alo.251 (OH)2] (CO₃)₀126'0.85H₂O</td><td> 231</td><td> 4.75</td><td> 0.373</td>

*Textural properties of calcined samples at 923K in air atmosphere for 4h. Dp: Average pore diameter. Vp: Total pore volume.

Table 6 shows the results of the texture analyses of the calcined hydrotalcites.

In Figure 3 we appreciate the difraction patterns of X-rays corresponding to a hydrotalcite type structure.

Preparation of the M(il) Cu Al series, where M(ll): Mg²⁺, Co²⁺ (Ternary) io These compounds, with the general developed formula: [M(ll)y__x__y Cu_x Al_y (OH)₂]^X+ (Aⁿy/n)^x' -mH20, were prepared by the co-precipitation method at low supersaturation. It is worth mentioning that to synthesize this type of solids, a very strict control should be exercised over the parameters, given that the cations presenting the well-known Jahn-Teller effect, in this case particularly Cu²⁺, tend not to 15 become incorporated or to exit the hydrotalcite structure easily.

Example 11

Synthesis of [Mg₀.₃07 Cu₀.n₈ Alo.₅₇₈(OH)₂] (CO₃)₀.₂₈9'0.803H₂O. A 2Molar solution was prepared, containing the metallic nitrates Mg(NO₃)₂-6H₂O (36.73g),

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ΑΙ(ΝΟ₃)₃·9Η₂Ο(19.14g), Cu(NO₃)₂-6H₂O (2.28 g), within a volume of 100 cm³, solution A. A second 2Molar solution was prepared, containing K₂CO₃ (111.68g) dissolved in 400 cm³ of de-ionized water, solution B. The two solutions were mixed by dripping in a glass reactor, containing previously 100 cm³ of de-ionized water at 333K. The addition was carried out by maintaining a constant pH of 10. The addition time was of approximately 25 minutes. The precipitate obtained was kept at a temperature of (333K) for 20 minutes under vigorous mechanical stirring; afterwards the greenish product was washed/filtered 5 times with hot de-ionized water (333K). Drying of the HT obtained was carried out at 373K during 24 h.

Example 12

Synthesis of [Mg₀.658 Cu_o.o98 AI0.244 (OH)₂] (C0₃)o.i22'0.687H₂0. A 2Molar solution was prepared, containing the metallic nitrates Mg (NO₃)₂-6H₂O (51.10g), AI(NO₃)₃-9H₂O(28.71g), Cu(NO₃)₂'6H₂0 (7.05g), within a volume of 150 cm³, solution A. A second 2Molar solution was prepared, containing K₂CO₃ (181.49g) dissolved in 650 cm³ of de-ionized water, solution B. The two solutions were mixed by dripping in a glass reactor, containing previously 100 cm³ of de-ionized water at 333K. The addition was performed by maintaining a constant pH of 10. The addition time was approximately 26 minutes. The precipitate obtained was kept at a temperature of (333K) during 20 minutes under vigorous mechanical stirring; afterwards the greenish product was washed/filtered 5 times with hot de-ionized water (333K). Drying of the HT obtained was carried out at 373K during 24 h.

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Example 13

Synthesis of [Mg_o.6oo Cu₀.u8 Alo.₂52(OH)₂] (CO₃)₀.-i26-0.709H20. A 2Molar solution was prepared, containing the metallic nitrates Mg(NO₃)2'6H₂O (31.13g),

AI(NO₃)₃-9H₂O(19.14g), Cu(NO₃)2-6H₂0 (7.35g), within a volume of 100 cm³, solution A. A second 2Molar solution was prepared, containing K2CO3 (139.61g) dissolved in 450 cm³ of de-ionized water, solution B. The two solutions (A and B) were mixed by dripping in a glass reactor containing previously 100 cm³ of de-ionized water at 333K. The addition was performed by keeping a constant pH of 10. The addition time was approximately 21 minutes. The precipitate obtained was kept at a temperature of (333K) for 20 minutes under vigorous mechanical stirring; afterwards the greenish product was washed/filtered 5 times with hot de-ionized water (333K). Drying of the HT obtained was carried out at 373K for 18 h.

Example 14

Synthesis of [Coo.₆₂o Cuo._2O6 AI₀.173(OH)₂] (CO₃)₀.i08 0.910 H₂O. A 1M solution was prepared, containing the metallic nitrates Co(NO₃)2'6H₂O (87g), AI(NO₃)₃-9H2O (37g), Cu(NO₃)₂-6H₂0 (23g), within a volume of 500 cm³, solution A. A second 2M solution was prepared, containing Κ₂ΟΟ₃ (117.97g) and KOH (9.89g) dissolved in 500 cm³ of de-ionized water, solution B. The two solutions (A and B) were mixed by dripping in a glass reactor containing previously 300 cm³ of de-ionized water at 353K. The addition was carried out by keeping a constant pH of 8. The precipitate obtained was kept at a temperature of 353K during 18 hours, under vigorous mechanical

CA 02562014 2006-10-02 stirring; afterwards, the product was washed/filtered 10 times with de-ionized water.

Drying of the HT obtained was performed at 373K for 18 h.

Table 7 shows the results of the texture analysis of the calcinated hydrotalcites.

Figure 4 presents the difraction patterns of X-rays coresponding to a hydrotalcite type structure.

Table 7. Developed formula and textural properties of HT’s .

<td> Sample*</td><td> BET Area (m²/g)</td><td> Dp (nm)</td><td> Vp (cm³/g)</td>

<td> [Mg₀ 307CU0 nsAlo 578(OH)₂] (C03)o₂89O.80H₂0</td><td> 200</td><td> 4.74</td><td> 0.346</td>

<td> [Mgo65sCuo οθδΑΙο 244(OH)₂] (CO₃)₀₁₂₂ 0.69H₂O</td><td> 184</td><td> 5.17</td><td> 0.338</td>

<td> [Mg₀.60oCUo 14δΑΙ₀ 252(OH)₂] (C0₃)o 126'0.71 H₂O</td><td> 136</td><td> 6.06</td><td> 0.334</td>

*Textural properties of calcined samples at 923K in air atmosphere for 4h. Dp: Average pore diameter. Vp: Total pore volume.

Example 15

Synthesis of [Mg₀.655 AI0.115 Mno.230 (OH)₂J (C0₃)o.i46· 0.729 H₂O. The preparation of this type of compounds required the employment of this special manner of synthesis, since due to the great size of the ionic radius of the metallic cation Μη (II) 15 with respect to the other metallic cations employed, which renders its incorporation into the structural network difficult, the procedure was the following: An aqueous solution (A) 2M was prepared with 38.85g of Mg(NO₃)₂*6H₂O, 9.57g of ΑΙ(ΝΟ₃)₃·9Η₂Ο and 14.64g MnCI₂*4H₂O in 500 cm³ of de-ionized water. On the other hand, an alkaline solution (B) 2M was prepared, containing 52.30g of K₂CO₃ and 37.75g of

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KOH in 500 cm³ of water. Solution B was placed previously in a glass reactor; solution A began to drip slowly until it reached a final pH of 9.5. The solution obtained was kept under vigorous mechanical stirring, at room temperature, during 3 hours. Afterwards, the precipitate obtained was washed and filtered with de-ionized water 10 times in order to eliminate excess ions. Drying took place at a temperature of 353K during 12 h. The BET specific area determined in this sample, calcined at 923K in air atmosphere for 4 hours, was of 200 m²/g, with a pore volume of 0.587cm³/g and an average pore diameter comprised between 5-12 nm.

Preparation of the MgZnAIFe (Quaternary) series

Solids of the hydrotalcite type [Mg^x.y.zZnxAly Fe_z(OH)2]^x+(Aⁿ’y_+z/_n)^x'^-mH2O, were prepared by co-precipitation at high supersaturation.

Example 16

Obtaining the HT type solid with the developed formula: [Mg₀.68Zn₀.07 AI₀.i7 Feo.os (OH)₂] (C0₃)o.i25 -0.90 H2O, was performed as follows: First, an aqueous solution (A) was prepared with 10.03g of Mg (ΝΟ₃)2·6Η₂Ο, 1.19g of Zn (NO₃)₂ ·6Η₂Ο, 3.75g of ΑΙ(ΝΟ₃)3·9Η₂Ο and 1.65g Fe(NO₃)₃’9H₂O in 57 cm³ of water. On the other hand, an alkaline solution (B) was prepared, containing 28.12g of K2CO3 and 25.80 g of KOH in 305 cm³ of water. Solution A was added previously to a glass reactor; solution B began to drip slowly until it reached a final pH of 9. The solution obtained was kept under vigorous mechanical stirring at a temperature of 353 K for 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized

CA 02562014 2006-10-02 water (353 K) 8 times in order to eliminate excess ions. Drying took place at a temperature of 373K during 24 h.

Example 17

Obtaining the HT type solid with the developed formula: [Mg₀.7i Zn_o.o4 AI₀.i4 Feo.n (OH)₂] (CO₃)₀.i25 -0.87 H₂O, was carried out as follows: First, an alkaline solution (A) was prepared with 10.51 g of Mg(NO3)₂*6H₂O, 0.56g of Zn (NO₃)₂ ·6Η₂Ο, 3.00g of ΑΙ(ΝΟ₃)₃·9Η₂Ο y 2.43g Fe(NO3)₃’9H₂O in 57 cm³ of water. On the other hand, an aqueous solution (B) was prepared, containing 28.12g of Κ₂ΟΟ₃ and 25.80 g of KOH in 305 cm³ of water. Solution A was added previously to a glass reactor; solution B began to drip slowly until it reached a final pH of 9. The solution obtained was kept under vigorous mechanical stirring at a temperature of 353 K during 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions. Drying took place at a temperature of 373K during 24 h.

Binary Hydrotalcites

The following examples refer to binary hydrotalcites used only with purposes comparative to multimetallic hydrotalcites. The characterization results of this group are integrated on the respective Tables and Figures of multimetallic hydrotalcites.

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Example 18

Synthesis of [Mgo.643 Fe₀.₃57 (OH)₂] (C0₃)o.i43- 0.807H₂0. An aqueous (A) 1 molar solution was prepared, containing the dissolved salts of Mg(NO₃)₂*6H₂O (21.62g) and Fe(NO₃)₃*9H₂O (11.55g) in 112 cm³ of de-ionized water. On the other hand, an alkaline solution (B) 2M was prepared, containing K₂CO₃ (9.3g) and KOH (8.51 g) with a molar relationship of KOH/K₂CO₃=2, in 100 cm³ of de-ionized water. Solution A was placed previoulsy in a glass reactor; then solution B began to drip slowly until it reached a final pH of 9 in the reactor. The solution obtained was kept under mechanical stirring at a temperature of 353K for 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions. Drying took place at a temperature of 373K during 24 h.

Example 19

Synthesis of [Mg0.744AI0.256 (OH)₂] (C0₃)o.i₂8’0.850H₂0. An aqueous solution (A, 1M) was prepared, containing the disolved salts of Mg(NO₃)₂«6H₂O (23.1g) and ΑΙ(ΝΟ₃)₃·9Η₂Ο (11.25g) in 120 cm³ of de-ionized water. On the other hand, an alkaline solution (B) 2M was prepared, with a moral relationship of KOH/K₂CO₃=2, and for this 11.17g of K₂CO₃ and 10.20g of KOH were dissolved in 120 cm³ of deionized water. Solutions A and B were added simultaneously to a glass reactor containing previously 100 cm³ of de-ionized water. The precipitation was performed at a constant pH of 10. The solution obtained was kept under vigorous mechanical stirring, at a temperature of 353 K, during 18 hours. Afterwards, the precipitate

CA 02562014 2006-10-02 obtained was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions. Drying took place at a temperature of 373K for 24 h.

Example 20

Preparation of the compound [Zno.750 Alû.250 (OH)₂] (C0₃)o.i₂₅O.840H₂0. An aqueous solution (A, 1M) was prepared, containing the disolved salts of Ζη(ΝΟ₃)₂·6Η₂Ο (19.63g) y ΑΙ(ΝΟ₃)₃·9Η₂Ο (8.25g) in 88 cm³ of de-ionized water. On the other hand, an alkaline solution (B) 2M was prepared, with a molar relationship of KOH/K₂CO₃=2, and for this 9.30g of K₂CO₃ and 8.51 g of KOH were disolved in 100 cm³ of de-ionized water. Solutions A and B were added simultaneously to a glass reactor containing previously 100 cm³ of de-ionized water. The precipitation was performed at a constant pH of 9. The solution obtained was kept under vigorous mechanical stirring, at a temperature of 353 K, for 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions. Drying took place at a temperature of 373K for 24 h.

Example 21

Synthesis of [Ni_{0 8}33 AI0.167 (OH)₂J (C0₃)o.o84'0.683H₂0. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of Ni(NO₃)₂*6H₂O (20.56g) and ΑΙ(ΝΟ₃)₃·9Η₂Ο (7.50g) in 90 cm³ of de-ionized water. On the other hand, an alkaline solution (Β) 2M was prepared, with a molar relationship of KOH/K₂CO₃=2, and for this 9.3g of K₂CO₃ and 8.51 g of KOH were dissolved in 100 cm³ of de-ionized water. Solutions A and B were added simultaneeously to a glass reactor containing

CA 02562014 2006-10-02 previously 100 cm3 of de-ionized water. The precipitation was performed at a constant pH of 9. The solution obtained was kept under vigorous mechanical stirring, at a temperature of 353 K, during 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminatte excess ions. Drying took place at a temperature of 373K for 24 h.

Example 22

Synthesis of (Mg 0.670 Fe 0.330 (OH)2) (CO3) 0.165. 0.80 H2O. An aqueous solution (A) 1 molar was prepared, containing the dissolved salts of MgCI₂*6H₂O (17.43g) and FeCI₃*9H₂O (7.72g) in 112 cm³ of de-ionized water. On the other hand, an alkaline solution (B) 2M was prepared, containing K₂CO₃ (9.3g) and KOH (8.51g) with a molar relationship of KOH/K₂CO₃=2, in 100 cm³ of de-ionized water. Solution A was placed previously in a glass reactor; later solution B began to drip slowly until it reaches a final pH of 9 in the reactor. The solution obtained was kept under mechanical stirring at a temperature of 353K during 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions. Drying took place at a temperature of 373K for 24 h.

Example 23

Synthesis of [Mgo.730 Al 0.270 (OH)₂] (C0₃)o.i₃5- 0.71 H₂O. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of MgCI₂«6H₂O (18.67g) and AICI₃«9H₂O (7.32g) in 120 cm³ of de-ionized water. On the other hand, an alkaline

CA 02562014 2006-10-02 solution (B) 2M was prepared, with a molar relationship of KOH/K₂CO₃=2, and for this 11.17g of K₂CO₃ and 10.20g of KOH were dissolved in 120 cm³ of de-ionized water. Solutions A and B were added simultaneously to a glass reactor containing previously 100 cm³ of de-ionized water. The precipitation was carried out at a constant pH of 10. The solution obtained was kept under vigorous mechanical stirring, at a temperature of 353 K for 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions. Drying took place at a temperature of 373K during 24 h.

Example 24

Preparation of compound [Zn_o.75o Alo.₂so (OH)₂J (C0₃)o.i25 -0.84 H₂O. An aqueous solution (A, 1M) was prepared, containing the dissolved salts of ZnCI₂*6H₂O (9.18g) and AICI₃*9H₂O (5.36g) in 88 cm³ of de-ionized water. On the other hand, an alkaline solution (B) 2M was prepared, with a molar relationship of KOH/K₂CO₃=2, and for this 9.30g of K₂CO₃ and 8.51 g of KOH were dissolved in 100 cm³ of de-ionized water. Solutions A and B were added simultaneously to a glass reactor containing previously 100 cm³ of de-ionized water. The precipitation was carried out at a constant pH of 9. The solution obtained was kept under vigorous mechanical stirring, at a temperature of 353 K for 18 hours. Afterwards, the precipitate obtained was washed and filtered with hot de-ionized water (353 K) 8 times in order to eliminate excess ions. Drying took place at a temperature of 373K during 24 h.

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Table 8 shows the results of the texture analyses of the calcined hydrotalcites.

Figures 1 to 4 show the difraction patterns of the X-rays of such compounds, where we may appreciate a hydrotalcite type structure.

Table 8. Developed formula and textural properties of HT’s .

<td> Sample*</td><td> Area BET (m²/g)</td><td> Dp (nm)</td><td> Vp (cm³/g)</td>

<td> [Mgo.643 Fe₀ 357(OH)2](C0₃)o 143 0.81 H₂O</td><td> 177</td><td> 2-12</td><td> 0.391</td>

<td> [Mgo.744 Al_o 25e(OH)₂] (C0₃)o i₂8’0.85H₂O</td><td> 276</td><td> 7-16</td><td> 0.674</td>

<td> [Zno 75 Alo.25(OH)₂] (C0₃)o 125’0.84H₂O</td><td> 48</td><td> 2-7</td><td> 0.085</td>

<td> [Nio.833 Alo 167(014)2] (C0₃)o 084’0.68H2O</td><td> 260</td><td> 2-5</td><td> 0.511</td>

<td> [Mg 0.670 Fe 0.330 (OH)₂](C0₃)o.i65 0.80 H₂O</td><td> 159</td><td> 5-10</td><td> 0.362</td>

<td> [Mgo.730 Al 0 ₂70 (OH)₂] (C0₃)o.135 0.71 H₂O</td><td> 234</td><td> 12</td><td> 0.564</td>

<td> [ΖΠο.750 Alo 250 (014)2] (C0₃)o i25 0.84 H₂O</td><td> 51</td><td> 2-12</td><td> 0.112</td>

*Textural properties of calcined samples at 923K in air atmosphere for 4h. Dp: Average pore diameter. Vp: Total pore volume.

CA 02562014 2010-09-08

Anion Exchange:

Given that in certain of the aforementioned preparations, all or some of the precursor salts, where there were metallic chlorides ((Mg 0.670 Fe 0.330 (OH2)) (CO3) 0.165.0.80 H₂O, [Mg_o.73oAl_o .270 (OH)₂] (003)0.135 0.71 H₂O, [Zno.750 Alo .250 (OH)₂] (003)0.125 -0.84 H2O, [Mgo.655 Alo.115 Mno.230 (OH)2](C03)o.i46- 0.729 H2O), an anionic exchage was effected after the synthesis in such compounds, to have carbonate anions in the interlaminar region, more easily removable than chlorides, since these latter anions remain in hydrotalcites up to 1073 K, thus inhibiting the basic sites. The exchange protocol was the following: An 0.2 M solution of K2CO3, was placed in contact with the sample to be exchanged, during 3 hours, under vigorous stirring, at a temperature of 343K. Afterwards, it was washed and filtered 8 times with de-ionized water. Drying of the product obtained was performed at 373K for 24 h. In order to obtain a high degree of carbonate anion exchange, the above operation is repeated once more.

CA 02562014 2013-06-11