WO2012017115A1 - Catalysts organized hierarchically by means of dry nanodispersion - Google Patents

Catalysts organized hierarchically by means of dry nanodispersion Download PDF

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WO2012017115A1
WO2012017115A1 PCT/ES2011/070504 ES2011070504W WO2012017115A1 WO 2012017115 A1 WO2012017115 A1 WO 2012017115A1 ES 2011070504 W ES2011070504 W ES 2011070504W WO 2012017115 A1 WO2012017115 A1 WO 2012017115A1
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co3o
zno
nanoparticles
catalysts
nanodispersion
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French (fr)
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José Francisco FERNÁNDEZ LOZANO
Fernando Rubio Marcos
Vanesa Calvino Casilda
Miguel Ángel BAÑARES GONZÁLEZ
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Consejo Superior De Investigaciones Científicas (Csic)
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/60—Mixing solids with solids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/74—Iron group metals
    • B01J23/75—Cobalt
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/20—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state
    • B01J35/23—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state in a colloidal state
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/391—Physical properties of the active metal ingredient
    • B01J35/393—Metal or metal oxide crystallite size
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G51/00—Compounds of cobalt
    • C01G51/40—Cobaltates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/76—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by a space-group or by other symmetry indications
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/82—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by IR- or Raman-data
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer

Definitions

  • the present invention relates to a process for obtaining catalysts by nanodispersion and anchoring of nanoparticles or nanoparticulate clusters smaller than 100 nm on submicron or micrometric supports using a low energy dry dispersion process.
  • Catalysts prepared at room temperature are characterized by presenting new nanoparticle support intercars capable of generating new reactive surfaces that favor high activity and catalytic selectivity.
  • the heat treatment of these catalytic systems causes the formation of stable crystalline species generating catalytically inactive interfaces by decreasing the number of free active sites.
  • Glycerin is a renewable chemical raw material, the use of which depends on its efficient conversion to products with high added value. However, glycerin reactivity provides too much chemical versatility, leading to a wide distribution of products that normally prevents its application [1-4].
  • the use of co-reactants to reduce product distribution is a particularly effective approach, for example, the use of ammonia to obtain acrylonitrile, both in the vapor phase and in the liquid phase provides yields of 40% to acrylonitrile with 90% selectivity [5- 7].
  • glycerin carbonate is also a product with high added value. Glycerin carbonate is one of the derivatives of glycerin that have more scientific and industrial interest thanks to the potential of its final uses.
  • Urea is a suggestive carbonylation agent, so in the year 2000, Mouloungui et al [15] patented the synthesis of glycerol carbonate by carbonylation of glycerol with urea using heterogeneous zinc catalysts such as zinc sulfate, organosulfate of zinc and ion exchange resins containing zinc.
  • the calcined zinc sulfate showed the best results by the reaction with urea (yields of glycerin carbonate of 86% in 2 hours) at 150 ° C and 40 mbar, eliminating the ammonia formed during the reaction.
  • heterogeneous catalysts are particularly effective in the reaction of glycerin carbonylation with urea [16,17], since they allow more moderate reaction conditions and good yields. There is therefore a great strategic and environmental benefit in the development of a heterogeneous catalyst for this process.
  • the reactions described above have a great environmental and sustainable value;
  • the development of environmentally acceptable catalytic processes requires heterogeneous catalysts.
  • the process of preparing a catalyst is a key component in terms of its environmental value.
  • the reactions described above have a significant environmental and sustainable value, thus the development of environmentally friendly catalytic processes requires heterogeneous catalysts.
  • the process of obtaining and preparing these catalysts is a key component both in the environmental value of the catalyst and in the development of a high catalytic activity (selectivity and conversion of the reactions involved).
  • the intercares created after the partial reaction by exposing both oxides generate the appearance of novel and interesting properties due to the proximity and diffusion effects of the materials involved [20,21], which acquire a greater relevance at the nanometric level.
  • the appearance of ferrimagnetism in the ZnO Co3O 4 system is related to intercara phenomena, although the constituent oxides of the system have diamagnetic and paramagnetic properties at room temperature, respectively [22,23]. Therefore, the present invention evaluates the effects on the process for preparing mixtures Co3O 4 ZnO obtained nanodispersion in dry process.
  • the process for preparing the family of catalysts modifies the structure and morphology of the Co3O 4 / ZnO system.
  • the present invention relates to a process for obtaining catalysts comprising the dry dispersion of nanoparticles or nanoparticulate clusters smaller than 100 nm on a support formed by micrometric particles.
  • the nanoparticles or nanoparticulate clusters are metal oxides or hydroxides that are selected from the list comprising oxides of aluminum, cobalt, copper, tin, nickel, silicon, titanium, zinc, brow, vanadium, niobium , tantalum, chromium, molybdenum, tungsten, phosphorus, antimony, iron, zirconium or any combination thereof.
  • the nanoparticles or nanoparticulate clusters are of cobalt oxides and more preferably of C03O
  • the particles that form the support are metal oxides or hydroxides, preferably aluminum oxides, zinc, silicon, titanium, zirconium, cerium, niobium or combinations thereof and more preferably ZnO.
  • the nanoparticles or nanoparticulate clusters are added to the dispersion in a percentage between 0.5 to 15 by weight with respect to the particles of the support.
  • the precursor materials of the nanoparticles and the support are subjected to a drying treatment.
  • Another aspect of the invention relates to the use of the catalyst described for the carbonylation of glycerin with urea. DESCRIPTION OF THE FIGURES.
  • FIG. 1 Micrograph of raw materials, (a) ZnO microparticles and (b) Co3O 4 nanoparticle agglomerates.
  • the insert shows a detail of the spherical nanoparticles Co3O 4 obtained by Transmission Electron Microscopy.
  • Figure 2. X-ray diffractograms corresponding to raw materials, Co3O 4 ZnO mixtures at room temperature and heat treated at 500 ° C / 36h as a function of Co3O 4 concentration.
  • Figure 3. (a) Raman spectra of the raw materials, of the Co3O 4 ZnO mixtures and of the Co3O 4 ZnO mixtures heat treated at 500 ° C for 36 hours depending on the Co3O 4 content. (b) Magnification of the Raman spectra in the range between 640 and 760 cm "1 of the heat treated Co3O 4 ZnO mixtures.
  • Figure 3 (b) shows the deconvolution by means of a Lorentzian function adjusted to the Raman mode associated with the appearance of the spinel phase (ZnCo2O 4 ).
  • Figure 5 Schematic representation of the binding of the nanoparticles to the surface of the micrometric ZnO obtained by the dry nanodispersion method, (a) Co3O 4 ZnO system before and (b) after the dry nanodispersion process, (c) Magnification of the surface of the hierarchically coated ZnO of Co3O 4 nanoparticles, where Co3O 4 - ZnO interleaves can be observed. (d) Schematic representation of the formation of the spinel phase after heat treatment at 500 ° C / 36h.
  • Figure. 6 Mechanism of the reaction between glycerol and urea. Reaction products: A urethane glycerol; B glycerol carbonate; C 5- (hydroxymethyl) -oxazolidin-2-one; D (2-methyl oxo-1, 3-dioxolan-4-yl) carbamate.
  • Nanodispersion procedure of Co3O 4 / ZnO mixtures Compositions with 0.5, 1, 5 and 10% by weight of Co3O 4 nanoparticles (hereinafter referred to as ZCo0.5-Nps, ZCo1 Nps, ZCo5 Nps and ZCo10 Nps, respectively) were prepared by incorporating the appropriate amounts of the Co3O 4 nanoparticles and ZnO microparticles by a previously described method of dry nanodispersion [18].
  • the process consists of dispersing the Co3O 4 / ZnO mixtures, with ZrO2 balls of 1 mm in diameter in a nylon container with a capacity of 60 cm 3 for 5 min at 50 rprn by means of a turbula type mixer.
  • the pure oxides ZnO and Co3O 4 have also been exposed to the same mixing process to ensure that contributions from the structural disorder produced by the mixing process are not introduced.
  • the raw materials used in this study are Cobalt oxide Co3O 4 (99.99%) and ZnO (99.99%) of analytical grade which were dried at 10 ° C for 2 hours before dry nanodispersion.
  • Morphology Characterization The particle size and morphology of the powders were evaluated using a Scanning Electron Microscope with field emission, FE-SEM (Hitachi S-4700) and by Transmission Electron Microscopy (MET, Hitachi H-7100 175) with an acceleration voltage of 120 kV. The samples analyzed by MET were suspended in isopropanol. Structural Characterization: The crystalline structure was determined by X-ray diffraction analysis (DRX, Siemens D5000, Kunststoff, Germany, CuK radiation). Raman spectra were obtained in the air atmosphere at room temperature, with radiation of 514 nm Ar + laser. The signal is collected by a Raman spectrometer equipped with a microscope (Micro-Raman Renishaw System 1000) and a measuring window between 100 cm "1 and 1 100 cm " 1 .
  • reaction procedure in the carbonylation of glycerin with urea The reaction procedure characteristic of this work consisted of mixing in a 10ml round bottom flask, glycerin and urea in equimolar amounts. Before adding the catalyst, this mixture was stirred for five minutes at 300 rpm in a batch reactor in a silicone bath heated to 140-145 ° C. After this type, the catalyst was added and the reaction began. This process was carried out in the absence of solvents at atmospheric pressure eliminating the ammonia formed during the reaction by passing a flow of air over the reaction mixture. The amount of catalyst used was 6% by weight with respect to the initial amount of glycerin used.
  • FIG. 1 (ab) The morphology of the raw materials ZnO and Co3O 4 is shown in Figure 1 (ab).
  • the FE-SEM micrograph, Figure 1 (a) shows the typical morphology of the ZnO consisting mainly of elongated prismatic particles and almost cubic particles, with sizes of 0.2-1 .0 fm, and an average particle size of 0.5 fm.
  • the morphology of the Co3O 4 nanoparticles is spherical with a size of 40-50 nm [see insert of Fig. 1 (b)] that form globular agglomerates of sizes between 0.5 to 4 fm Fig. 1 (b) .
  • the FE-SEM image of the ZnO mixture with 10% by weight of Co3O 4 nanoparticles can be seen in the figure. 1 C).
  • the Micrographs show that most of the Co3O 4 agglomerates disappear and the individual nanoparticles are attached to the surface of the ZnO, Fig. 1 (d).
  • the dispersion and adhesion of the nanoparticles could indicate the appearance of Co3O 4 ZnO intercalates at room temperature, due to the high initial reactivity of Co3O 4 and ZnO. All individual nanoparticles disperse below 10% by weight of Co3O 4 , but some agglomerates can be observed for high concentrations of Co3O 4 .
  • X-ray diffraction spectra of raw materials and mixtures of Co3O 4 / ZnO are shown in the Figure. 2, can be indexed based on a phase mixture consisting of a majority phase of ZnO and a minority of Co3O 4 . As expected, the intensity of the diffraction peaks of the Co3O 4 phase becomes increasingly intense with increasing Co3O 4 concentration.
  • High frequency, Ai g has been assigned to vibrations related to the movement of oxygen atoms within the octahedral unit of the spinel structure (for example, CoOe in Co3O 4 ) .Its width is related to the length of the anion-cation bonds, as well as with the distortions of the polyhedron that occur in the network of the spinel structure [26], while modes F 2g and E g combine the vibration of the spinel tetrahedron (for example, CoO 4 in Co3O 4 ) and octahedral sites [27]
  • Raman spectra of ZnO and Co3O 4 as raw materials and of Co3O 4 / ZnO mixtures are represented in Figure 3 (a), can be indexed in based on a mixture consisting of two phases, ZnO and Co3O 4.
  • the second band can be attributed to the emergence of the spinel phase ZnCo 2 O to -714 cm 4 "1 emerges concomitantly, Figure 3 (b).
  • the formation of the ZnCo 2 O 4 spinel is clearly observed
  • the spinel formation requires a wide diffusion of the Zn + 2 atoms and is therefore favored by the long calcination time to which the mixtures are subjected, 36 hours.
  • Recently, the formation of the spinel phase at low temperature ⁇ 400 ° C [28] has been described in this system, which could be related to the phenomena of diffusion of cations of Zn +2 .
  • Raman spectroscopy evidences a progressively intercalating reaction in Co3O 4 / ZnO mixtures, which is produced by the effective dispersion of nanoparticles on the surface of ZnO.
  • Prolonged heat treatments at low temperatures allow the diffusion of Zn cations and therefore the formation of new spinel-like structures, ZnCo 2 O 4 .
  • Zn cations are active at temperatures close to 400 ° C due to the thermal desorption of interstitial Zinc (Zn ⁇ + ) and the formation of surface oxygen vacancies (V 0 ) s .
  • urea reacts with glycerin when the mixture is heated in the presence of a catalyst.
  • the proposed reaction mechanism follows four possible steps: (I) carbamoylation of glycerin to glycerolurethane (A), (II) carbonylation of glycerolurethane to glycerin carbonate (4-hydroxymethyl-1, 3-dioxolan-2-one) (B) With ammonia abstraction or (III) carbonylation of glycerolurethane at 5- (hydroxymethyl) oxazolidin-2-one (C) without ammonia abstraction and (IV) glycerin carbonate can react with another urea molecule to give (2-) carbamate oxo-1, 3-dioxolan-4-yl) methyl (D), decreasing glycerin carbonate selectivity [15,17], see Fig 6.
  • Figure 4 shows the results of activity obtained during the carbonylation of glycerin using as catalysts the pure oxides of Co3O 4 and ZnO, the Co3O 4 ZnO catalytic system prepared by nanodispersion by dry route at room temperature and heat treated at 500 ° C / 36h.
  • Pure ZnO was not much more active than the reaction without catalyst, which is in agreement with the results published in the literature [30].
  • pure Co3O 4 oxide proved to be more active and selective.
  • the mixture of both oxides shows catalytic activity depending on the preparation procedure and treatment temperature. The catalytic activity increases considerably with the amount of cobalt oxide dispersed on zinc oxide in samples prepared at room temperature, however it increases slightly for the series of samples calcined at 500 ° C ( Figure 4).
  • Co3O 4 ZnO systems prepared by dry nanodispersion at room temperature showed the best results compared with pure starting oxides and with Co3O 4 ZnO systems calcined at 500 ° C / 36h.
  • the samples with high concentrations of Co3O 4 (10% by weight) showed the best activity (above 69% conversion and 97% selectivity to glycerin carbonate) demonstrating that a good dispersion of the active catalytic centers of Co3O 4 At the interface of the system, it plays a crucial role during the reaction.
  • the results highlight the importance of the synthesis method used in the preparation of this heterogeneous catalytic system.
  • Figure 5 (a) and (b) show a schematic representation of an individual ZnO particle hierarchically coated with Co3O 4 nanoparticles by the dry nanodispersion method. The dispersion and adhesion of the nanoparticles may indicate that a spontaneous reaction occurs at room temperature, between these materials, due to the high initial reactivity of Co3O 4 and ZnO [19].
  • Figure 5 (c) shows the magnification of the ZnO surface where it is possible to observe the formation of new interleaves between the ZnO microparticles and Co3O 4 nanoparticles.
  • the process performed nanodispersion dry mixing ZnO and Co3O 4 creates new reactive surfaces (as evidenced by FE-SEM and TEM) which can favor catalytic activity.
  • This new form of nanoparticle deagglomeration has been applied in the reaction of glycerol carbonylation with urea producing new properties in the intercars with high activity and catalytic selectivity.
  • the high reactivity of ZnO can promote greater availability of Zn cations to diffuse in the Co3O 4 nanoparticles, and therefore form stable crystalline species with spinel structure, ZnCo 2 O 4 , when the Co3O 4 ZnO system was heat treated to 500 ° C for 36h as can be seen in the figure. 5 d).
  • the heat treatment causes the formation of catalytically inactive species such as ZnCo 2 O 4 by decreasing the number of free active sites of Co3O 4 .

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Abstract

The invention relates to a method for producing catalysts by means of nanodispersion and anchoring of nanoparticles or nanoparticulate clusters smaller than 100 nm on submicronic or micrometric supports, using a process of low energy dry dispersion. The catalysts prepared at room temperature are characterized in that they have novel nanoparticle supporting interfaces capable of generating new reactive surfaces that promote high activity and catalytic selectivity. The thermal treatment of said catalytic systems induces the formation of stable crystalline species, generating catalytically inactive interfaces by reducing the number of free active sites.

Description

Catalizadores jerárquicamente organizados mediante nanodispersión por vía seca  Hierarchically organized catalysts by dry nanodispersion
La presente invención se refiere a un procedimiento para la obtención de catalizadores mediante nanodispersión y anclaje de nanopartículas o clusters nanoparticulados de tamaño inferior a 100 nm sobre soportes submicrónicos o micrométricos empleando un proceso de dispersión en vía seca de baja energía. Los catalizadores preparados a temperatura ambiente están caracterizados por presentar nuevas intercaras soporte-nanopartícula capaces de generar nuevas superficies reactivas que favorecen una alta actividad y selectividad catalítica. El tratamiento térmico de estos sistemas catalíticos provoca la formación de especies cristalinas estables generando interfases catalíticamente inactivas al disminuir el número de sitios activos libres. The present invention relates to a process for obtaining catalysts by nanodispersion and anchoring of nanoparticles or nanoparticulate clusters smaller than 100 nm on submicron or micrometric supports using a low energy dry dispersion process. Catalysts prepared at room temperature are characterized by presenting new nanoparticle support intercars capable of generating new reactive surfaces that favor high activity and catalytic selectivity. The heat treatment of these catalytic systems causes the formation of stable crystalline species generating catalytically inactive interfaces by decreasing the number of free active sites.
ESTADO DEL ARTE. La glicerina es una materia prima química renovable, cuyo uso depende de su conversión eficiente a productos de alto valor añadido. Sin embargo, la reactividad de la glicerina proporciona demasiada versatilidad química, conduciendo a una amplia distribución de productos que normalmente impide su aplicación [1 -4]. La utilización de co-reactantes para reducir la distribución de productos es un enfoque particularmente efectivo, por ejemplo, la utilización de amoníaco para obtener acrilonitrilo, ambos en fase vapor y en fase líquida proporciona rendimientos del 40% a acrilonitrilo con un 90% de selectividad [5- 7]. Al igual que el acrilonitrilo, el carbonato de glicerina es también un producto de alto valor añadido. El carbonato de glicerina es uno de los derivados de la glicerina que tienen más interés científico e industrial gracias al potencial de sus usos finales. La búsqueda de rutas para producir eficientemente carbonato de glicerina a partir de materias primas renovables es un tema fundamental para las diferentes áreas de producción ya que se pueden obtener compuestos que resultan competitivos con aquellos obtenidos a partir de derivados del petróleo [8-10]. Para esta reacción, el dióxido de carbono, se utiliza como agente de carbonilación en condiciones supercríticas [1 1 ], sin embargo, se emplean condiciones experimentales severas. Otros agentes de carbonización son el dimetil carbonato [12,13]; o dialquil carbonatos [14]. La urea es un sugerente agente de carbonilación, por lo que en el año 2000, Mouloungui y colaboradores [15], patentaron la síntesis de carbonato de glicerina por carbonilación de glicerol con urea empleando catalizadores heterogéneos de zinc como el sulfato de zinc, el organosulfato de zinc y resinas de intercambio iónica conteniendo zinc. El sulfato de zinc calcinado mostró los mejores resultados por la reacción con urea (rendimientos de carbonato de glicerina del 86% en 2 horas) a 150 °C y 40 mbar, eliminando el amoníaco formado durante la reacción. Sin embargo el sulfato de zinc es soluble en glicerina, por lo que se trata de una reacción de catálisis homogénea, pudiéndose ser el catalizador parcialmente recuperado después de la reacción. Los catalizadores heterogéneos, resultan particularmente eficaces en la reacción de carbonilación de glicerina con urea [16,17], ya que permiten condiciones de reacción más moderadas y buenos rendimientos. Existe por lo tanto un gran beneficio estratégico ymedioambiental en el desarrollo de un catalizador heterogéneo para este proceso. Así Climent y colaboradores [17] han publicado recientemente la carbonilación de glicerina (rendimientos para carbonato de glicerina del 72% en 5h) con urea a 145 °C empleando catalizadores heterogéneos, como los óxidos básicos (MgO y CaO) y los óxidos mixtos (Al/Mg, Al/Li) derivados de hidrotalcitas con efectivos pares de centros ácido- base [17]. STATE OF ART. Glycerin is a renewable chemical raw material, the use of which depends on its efficient conversion to products with high added value. However, glycerin reactivity provides too much chemical versatility, leading to a wide distribution of products that normally prevents its application [1-4]. The use of co-reactants to reduce product distribution is a particularly effective approach, for example, the use of ammonia to obtain acrylonitrile, both in the vapor phase and in the liquid phase provides yields of 40% to acrylonitrile with 90% selectivity [5- 7]. Like acrylonitrile, glycerin carbonate is also a product with high added value. Glycerin carbonate is one of the derivatives of glycerin that have more scientific and industrial interest thanks to the potential of its final uses. The search for routes to efficiently produce glycerin carbonate from renewable raw materials is a fundamental issue for the different production areas since compounds that are competitive with those obtained from petroleum derivatives [8-10] can be obtained. For this reaction, carbon dioxide is used as Carbonylation agent under supercritical conditions [1 1], however, severe experimental conditions are employed. Other carbonizing agents are dimethyl carbonate [12,13]; or dialkyl carbonates [14]. Urea is a suggestive carbonylation agent, so in the year 2000, Mouloungui et al [15] patented the synthesis of glycerol carbonate by carbonylation of glycerol with urea using heterogeneous zinc catalysts such as zinc sulfate, organosulfate of zinc and ion exchange resins containing zinc. The calcined zinc sulfate showed the best results by the reaction with urea (yields of glycerin carbonate of 86% in 2 hours) at 150 ° C and 40 mbar, eliminating the ammonia formed during the reaction. However, zinc sulfate is soluble in glycerin, so it is a homogeneous catalysis reaction, the catalyst being partially recovered after the reaction. Heterogeneous catalysts are particularly effective in the reaction of glycerin carbonylation with urea [16,17], since they allow more moderate reaction conditions and good yields. There is therefore a great strategic and environmental benefit in the development of a heterogeneous catalyst for this process. Thus, Climent and collaborators [17] have recently published the carbonylation of glycerin (yields for 72% glycerin carbonate in 5 hours) with urea at 145 ° C using heterogeneous catalysts, such as basic oxides (MgO and CaO) and mixed oxides ( Al / Mg, Al / Li) hydrotalcite derivatives with effective pairs of acid-base centers [17].
Las reacciones descritas anteriormente poseen un gran valor medioambiental y sostenible; el desarrollo de procesos catalíticos medioambientalmente aceptables precisa catalizadores heterogéneos. De este modo el proceso de preparación de un catalizador es un componente clave en cuanto a su valor medioambiental se refiere. En este artículo mostramos un método de preparación libre de residuos y de disolventes para obtener Las reacciones descritas anteriormente tienen un significativo valor medio ambiental y sostenible, de este modo el desarrollo de procesos catalíticos amigables con el medio ambiente requiere de catalizadores heterogéneos. El proceso de obtención y preparación de estos catalizadores es un componente clave tanto en el valor medio ambiental del catalizador como en el desarrollo de una elevada actividad catalítica (selectividad y conversión de las reacciones involucradas). The reactions described above have a great environmental and sustainable value; The development of environmentally acceptable catalytic processes requires heterogeneous catalysts. In this way the process of preparing a catalyst is a key component in terms of its environmental value. In this article we show a method of preparation free of residues and solvents to obtain The reactions described above have a significant environmental and sustainable value, thus the development of environmentally friendly catalytic processes requires heterogeneous catalysts. The process of obtaining and preparing these catalysts is a key component both in the environmental value of the catalyst and in the development of a high catalytic activity (selectivity and conversion of the reactions involved).
Bajo estas premisas recientemente hemos desarrollado un novedoso método de nanodispersion, libre de residuos y sin disolvente orgánicos para el diseño de catalizadores jerárquicamente nanodispersos. En este procedimiento se dispersan nanopartículas sobre la superficie de soportes de escala micrométrica [18,19]. Este método de nanodispersion abre un amplio abanico de oportunidades para obtener sistemas jerarquizados nano-microsoportados con propiedades extraordinarias, realizados por medio de mezclado de óxidos de diferente naturaleza. Under these premises we have recently developed a novel method of nanodispersion, free of residues and without organic solvents for the design of hierarchically nanodispersed catalysts. In this procedure nanoparticles are dispersed on the surface of micrometric scale supports [18,19]. This nanodispersion method opens a wide range of opportunities to obtain nano-micro-supported hierarchical systems with extraordinary properties, made by mixing oxides of different nature.
Las intercaras creadas después de la reacción parcial mediante la exposición de ambos óxidos generan la aparición de novedosas e interesantes propiedades debido a los efectos de proximidad y difusión de los materiales involucrados [20,21 ], que adquieren una mayor relevancia a nivel nanométrico. De este modo, hemos demostrado que la aparición ferrimagnetismo en el sistema ZnO Co3O4 se encuentran relacionadas con los fenómenos de intercara, a pesar de que los óxidos constituyentes del sistema presenten propiedades diamagnéticas y paramagnéticas a temperatura ambiente, respectivamente [22,23]. Por lo tanto, la presente invención evalúa los efectos en el procedimiento de preparación de las mezclas de Co3O4 ZnO obtenidas por nanodispersion en vía seca. Además, el procedimiento de preparación de la familia de catalizadores modifica la estructura y morfología del sistema Co3O4/ZnO. De este modo, las propiedades catalíticas (actividad/selectividad) se modifican y regulan debido a las intercaras generadas en el sistema, ya que ha sido probada en la reacción de carbonilación de glicerina con urea. DESCRIPCIÓN DE LA INVENCIÓN. The intercares created after the partial reaction by exposing both oxides generate the appearance of novel and interesting properties due to the proximity and diffusion effects of the materials involved [20,21], which acquire a greater relevance at the nanometric level. In this way, we have shown that the appearance of ferrimagnetism in the ZnO Co3O 4 system is related to intercara phenomena, although the constituent oxides of the system have diamagnetic and paramagnetic properties at room temperature, respectively [22,23]. Therefore, the present invention evaluates the effects on the process for preparing mixtures Co3O 4 ZnO obtained nanodispersion in dry process. In addition, the process for preparing the family of catalysts modifies the structure and morphology of the Co3O 4 / ZnO system. In this way, the catalytic properties (activity / selectivity) are modified and regulated due to the intercares generated in the system, since it has been tested in the reaction of carbonylation of glycerin with urea. DESCRIPTION OF THE INVENTION
En un primer aspecto, la presente invención se refiere a un procedimiento de obtención de catalizadores que comprende la dispersión en vía seca de nanopartículas o clusters nanoparticulados de tamaño inferior a 100 nm sobre un soporte formado por partículas micrométricas. In a first aspect, the present invention relates to a process for obtaining catalysts comprising the dry dispersion of nanoparticles or nanoparticulate clusters smaller than 100 nm on a support formed by micrometric particles.
En una realización preferida, en el procedimiento descrito las nanopartículas o clusters nanoparticulados son óxidos o hidróxidos metálicos que se seleccionan de la lista que comprende óxidos de aluminio, cobalto, cobre, estaño, níquel, silicio, titanio, zinc, ceño, vanadio, niobio, tántalo, cromo, molibdeno, wolframio, fósforo, antimonio, hierro, circonio o cualquiera de sus combinaciones. In a preferred embodiment, in the described process the nanoparticles or nanoparticulate clusters are metal oxides or hydroxides that are selected from the list comprising oxides of aluminum, cobalt, copper, tin, nickel, silicon, titanium, zinc, brow, vanadium, niobium , tantalum, chromium, molybdenum, tungsten, phosphorus, antimony, iron, zirconium or any combination thereof.
Preferiblmente, las nanopartículas o clusters nanoparticulados son de óxidos de cobalto y más preferiblemente de C03O Preferably, the nanoparticles or nanoparticulate clusters are of cobalt oxides and more preferably of C03O
En otra realización preferida, en el procedimiento descrito las partículas que forman el soporte son de óxidos o hidróxidos metálicos, preferiblemente óxidos de aluminio, zinc, silicio, titanio, circonio, cerio, niobio o combinaciones de los mismos y más preferiblemente de ZnO. In another preferred embodiment, in the described process the particles that form the support are metal oxides or hydroxides, preferably aluminum oxides, zinc, silicon, titanium, zirconium, cerium, niobium or combinations thereof and more preferably ZnO.
En otra realización preferida, las nanopartículas o clusters nanoparticulados se adicionan a la dispersión en un porcentaje de entre 0,5 a 15 en peso respecto a las partículas del soporte. En otra realización preferida, los materiales precursores de las nanopartículas y del soporte se someten a un tratamiento de secado. In another preferred embodiment, the nanoparticles or nanoparticulate clusters are added to the dispersion in a percentage between 0.5 to 15 by weight with respect to the particles of the support. In another preferred embodiment, the precursor materials of the nanoparticles and the support are subjected to a drying treatment.
En otra realización preferida, Procedimiento según cualquiera de las reivindicaciones anteriores donde los catalizadores obtenidos se someten a un tratamiento térmico. Otro aspecto de la invención se refiere a un catalizador obtenible por el procedimiento según se ha descrito anteriormente. In another preferred embodiment, Method according to any of the preceding claims wherein the catalysts obtained are subjected to a heat treatment. Another aspect of the invention relates to a catalyst obtainable by the process as described above.
Otro aspecto de la invención se refiere al uso del catalizador descrito para la carbonilación de glicerina con urea. DESCRIPCIÓN DE LAS FIGURAS. Another aspect of the invention relates to the use of the catalyst described for the carbonylation of glycerin with urea. DESCRIPTION OF THE FIGURES.
Figura 1. Micrografía de los materias primas, (a) micropartículas de ZnO y (b) aglomerados Co3O4 nanopartículado. El inserto muestra un detalle de las nanopartículas esféricas de Co3O4 obtenidas por Microscopía Electrónica de Transmisión. Micrografía, FE-SEM, de las partículas ZnO recubiertas por las nanopartículas de Co3O4 adheridas a la superficie después del proceso de nanodispersion en seco, (c) Mezcla de ZnO con un 10% en peso de nanopartículas Co3O4 nanopartículado; (d) Detalle de la micrografía obtenida por TEM de las nanopartículas de Co3O4 dispersas en una micropartícula de ZnO con morfología prismática observado en las mezclas con Co3O4 en concentraciones superiores al 5% en peso. Figure 1. Micrograph of raw materials, (a) ZnO microparticles and (b) Co3O 4 nanoparticle agglomerates. The insert shows a detail of the spherical nanoparticles Co3O 4 obtained by Transmission Electron Microscopy. Micrograph, FE-SEM, of the ZnO particles coated by the Co3O 4 nanoparticles adhered to the surface after the dry nanodispersion process, (c) ZnO mixture with 10% by weight of nanoparticle Co3O 4 nanoparticles; (d) Detail of the micrograph obtained by TEM of the Co3O 4 nanoparticles dispersed in a ZnO microparticle with prismatic morphology observed in mixtures with Co3O 4 in concentrations greater than 5% by weight.
Figura 2. Difractogramas de Rayos X correspondientes a las materias primas, las mezclas Co3O4 ZnO a temperatura ambiente y tratadas térmicamente a 500 °C/36h en función de la concentración de Co3O4. Figura 3. (a) Espectros Raman de las materias primas, de las mezclas Co3O4 ZnO y así como de las mezclas Co3O4 ZnO tratadas térmicamente a 500 °C durante 36h en función del contenido Co3O4. (b) Magnificación de los espectros Raman en el rango entre 640 y 760 cm"1 de las mezclas Co3O4 ZnO tratadas térmicamente. La figura 3 (b) presenta la deconvolución mediante una función Lorentziana ajustada al modo Raman asociado a la aparición de la fase espinela (ZnCo2O4). Figure 2. X-ray diffractograms corresponding to raw materials, Co3O 4 ZnO mixtures at room temperature and heat treated at 500 ° C / 36h as a function of Co3O 4 concentration. Figure 3. (a) Raman spectra of the raw materials, of the Co3O 4 ZnO mixtures and of the Co3O 4 ZnO mixtures heat treated at 500 ° C for 36 hours depending on the Co3O 4 content. (b) Magnification of the Raman spectra in the range between 640 and 760 cm "1 of the heat treated Co3O 4 ZnO mixtures. Figure 3 (b) shows the deconvolution by means of a Lorentzian function adjusted to the Raman mode associated with the appearance of the spinel phase (ZnCo2O 4 ).
Figura 4. Desarrollo de la actividad catalítica de los sistemas Co3O4 ZnO para la síntesis de carbonato de glicerina a 145 °C durante 4h. Figure 4. Development of the catalytic activity of Co3O 4 ZnO systems for the synthesis of glycerin carbonate at 145 ° C for 4h.
Figura 5. Representación esquemática de la unión de las nanopartículas a la superficie del ZnO micrométrico obtenida por el método seco nanodispersion, (a) Sistema Co3O4 ZnO antes y (b) después del proceso de nanodispersion por vía seca, (c) Magnificación de la superficie del ZnO recubierto jerárquicamente de nanopartículas de Co3O4, donde se puede observar intercaras de Co3O4- ZnO. (d) Representación esquemática de la formación de la fase espinela después de tratamiento térmico a 500 °C/36h. Figure 5. Schematic representation of the binding of the nanoparticles to the surface of the micrometric ZnO obtained by the dry nanodispersion method, (a) Co3O 4 ZnO system before and (b) after the dry nanodispersion process, (c) Magnification of the surface of the hierarchically coated ZnO of Co3O 4 nanoparticles, where Co3O 4 - ZnO interleaves can be observed. (d) Schematic representation of the formation of the spinel phase after heat treatment at 500 ° C / 36h.
Figura. 6 Mecanismo de la reacción entre el glicerol y urea. Productos de reacción: A uretano glicerol; B carbonato de glicerol; C 5-(hidroximetil)- oxazolidin-2-ona; D (2-metil oxo-1 ,3-dioxolan-4-il) carbamato. Figure. 6 Mechanism of the reaction between glycerol and urea. Reaction products: A urethane glycerol; B glycerol carbonate; C 5- (hydroxymethyl) -oxazolidin-2-one; D (2-methyl oxo-1, 3-dioxolan-4-yl) carbamate.
EJEMPLOS EXAMPLES
Procedimiento de Nanodispersión de las mezclas Co3O4/ZnO: Las composiciones con 0,5, 1 , 5 y 10% en peso de nanopartículas Co3O4 (en lo sucesivo, nombradas como ZCo0.5-Nps, ZCo1 Nps, ZCo5 Nps y ZCo10 Nps, respectivamente) fueron preparadas por la incorporación de las cantidades apropiadas de las nanopartículas de Co3O4 y micropartículas de ZnO mediante un procedimiento previamente descrito de nanodispersión por vía seca [18]. El proceso consiste en dispersar las mezclas de Co3O4/ZnO, con bolas de ZrO2 de 1 mm de diámetro en un contenedor de nylon con capacidad de 60 cm3 durante 5 min a 50 rprn por medio de un mezclador de tipo turbula. Los óxidos puros ZnO y Co3O4 también han estado expuestos al mismo proceso de mezclado para asegurar que no se introducen contribuciones procedentes al desorden estructural producido por el proceso de mezclado. Las materias primas utilizadas en este estudio son óxido de cobalto Co3O4 (99,99%) y ZnO (99,99%) de grado analítico los cuales se secaron a 1 10 °C durante 2 horas antes de la nanodispersión en seco. Nanodispersion procedure of Co3O 4 / ZnO mixtures: Compositions with 0.5, 1, 5 and 10% by weight of Co3O 4 nanoparticles (hereinafter referred to as ZCo0.5-Nps, ZCo1 Nps, ZCo5 Nps and ZCo10 Nps, respectively) were prepared by incorporating the appropriate amounts of the Co3O 4 nanoparticles and ZnO microparticles by a previously described method of dry nanodispersion [18]. The process consists of dispersing the Co3O 4 / ZnO mixtures, with ZrO2 balls of 1 mm in diameter in a nylon container with a capacity of 60 cm 3 for 5 min at 50 rprn by means of a turbula type mixer. The pure oxides ZnO and Co3O 4 have also been exposed to the same mixing process to ensure that contributions from the structural disorder produced by the mixing process are not introduced. The raw materials used in this study are Cobalt oxide Co3O 4 (99.99%) and ZnO (99.99%) of analytical grade which were dried at 10 ° C for 2 hours before dry nanodispersion.
Morfología Caracterización: El tamaño de partícula y la morfología de los polvos se evaluaron utilizando un Microscopio Electrónico de Barrido con emisión de campo, FE-SEM (Hitachi S-4700) y mediante Microscopía Electrónica de Transmisión (MET, Hitachi H-7100 175) con un voltaje de aceleración de 120 kV. Las muestras analizadas por MET fueron suspendidas en isopropanol. Caracterización Estructural: La estructura cristalina se determinó por análisis de difracción de rayos X (DRX, Siemens D5000, Munich, Alemania, la radiación de CuK(). Los espectros Raman se obtuvieron en la atmósfera de aire a temperatura ambiente, con una radiación de láser de Ar+ de 514 nm. La señal es recogida por un espectrómetro Raman provisto de un microscopio (Micro- Raman Renishaw Sistema 1000) y una ventana de medida comprendida entre los 100 cm"1 y los 1 100 cm"1. Morphology Characterization: The particle size and morphology of the powders were evaluated using a Scanning Electron Microscope with field emission, FE-SEM (Hitachi S-4700) and by Transmission Electron Microscopy (MET, Hitachi H-7100 175) with an acceleration voltage of 120 kV. The samples analyzed by MET were suspended in isopropanol. Structural Characterization: The crystalline structure was determined by X-ray diffraction analysis (DRX, Siemens D5000, Munich, Germany, CuK radiation). Raman spectra were obtained in the air atmosphere at room temperature, with radiation of 514 nm Ar + laser. The signal is collected by a Raman spectrometer equipped with a microscope (Micro-Raman Renishaw System 1000) and a measuring window between 100 cm "1 and 1 100 cm " 1 .
Figure imgf000009_0001
Tabla 1. Principales modos Raman observado en el ZnO y las fases de Co3O4. La intensidad de los picos se tabula desde muy bajas hasta muy intensas, (b: bajo, m: media; f: fuerte, v: muy).
Figure imgf000009_0001
Table 1. Main Raman modes observed in ZnO and Co3O 4 phases. The intensity of the peaks is tabulated from very low to very intense, (b: low, m: medium; f: strong, v: very).
Procedimiento de reacción en la carbonilación de glicerina con urea: El procedimiento de reacción característico de este trabajo consistió en mezclar en un matraz de fondo redondo de 10ml, glicerina y urea en cantidades equimolares. Antes de añadir el catalizador, esta mezcla era agitada durante cinco minutos a 300rpm en un reactor tipo batch dentro de un baño de silicona calentado a 140-145°C. Transcurrido este tipo se añadía el catalizador y la reacción comenzaba. Este proceso se llevaba a cabo en ausencia de disolventes a presión atmosférica eliminando el amoníaco formado durante la reacción haciendo pasar un flujo de aire sobre la mezcla de reacción. La cantidad de catalizador utilizada fue del 6% en peso respecto a la cantidad inicial de glicerina empleada. Transcurridas cuatro horas de reacción, se procedía a la toma de muestra empleando agua para su dilución y extrayendo el catalizador por filtración. El catalizador se lavaba con acetona varias veces y se secaba a temperatura ambiente durante 24 horas para poder ser utilizado posteriormente en un nuevo ciclo de reacción. La reacción era entonces seguida por cromatografía de gases utilizando un cromatógrafo de gases HP5890 provisto con una columna capilar Ultra 2-5% de fenil metil siloxano (50m) y detector de llama (FID). Reaction procedure in the carbonylation of glycerin with urea: The reaction procedure characteristic of this work consisted of mixing in a 10ml round bottom flask, glycerin and urea in equimolar amounts. Before adding the catalyst, this mixture was stirred for five minutes at 300 rpm in a batch reactor in a silicone bath heated to 140-145 ° C. After this type, the catalyst was added and the reaction began. This process was carried out in the absence of solvents at atmospheric pressure eliminating the ammonia formed during the reaction by passing a flow of air over the reaction mixture. The amount of catalyst used was 6% by weight with respect to the initial amount of glycerin used. After four hours of reaction, the sample was taken using water for dilution and the catalyst was removed by filtration. The catalyst was washed with acetone several times and dried at room temperature for 24 hours to be used later in a new reaction cycle. The reaction was then followed by gas chromatography using an HP5890 gas chromatograph provided with an Ultra 2-5% capillary column of phenyl methyl siloxane (50m) and flame detector (FID).
Morfología de las mezclas Co O4 ZnO Morphology of Co O 4 ZnO mixtures
En la Figura 1 (a-b) se muestra la morfología de las materias primas ZnO y Co3O4. La micrografía FE-SEM, Figura 1 (a), muestra la morfología típica del ZnO que consiste principalmente en partículas prismáticas alargadas y partículas casi cúbica, con tamaños de 0.2-1 .0 fm, y un tamaño de partícula promedio de 0,5 fm. La morfología de las nanopartículas de Co3O4 es esféricas con un tamaño de 40-50 nm [ver inserto de la Fig. 1 (b)] que forman aglomerados globulares de tamaños comprendidos entre 0,5 a 4 fm Fig. 1 (b). Por otro lado, la imagen FE-SEM de la mezcla de ZnO con un 10% en peso de nanopartículas de Co3O4 puede ser observada en la figura. 1 (c). Las micrografías muestran que la mayoría de los aglomerados Co3O4 desaparecen y las nanopartículas individuales están adheridas a la superficie del ZnO, Fig. 1 (d). La dispersión y una la adherencia de las nanopartículas podría indicar la aparición de intercaras Co3O4 ZnO a temperatura ambiente, debido a la alta reactividad inicial del Co3O4 y ZnO. Todas las nanopartículas individuales se dispersan por debajo del 10% en peso de Co3O4, pero algunos aglomerados pueden ser observados para concentraciones elevadas de Co3O4. Esto significa que para concentraciones > 10% en peso, el límite de dispersión de las nanopartículas sobre las micropartículas de ZnO se ha alcanzado. Es característico del proceso que la morfología de las partículas de ZnO se mantiene invariable como consecuencia de la baja energía utilizada durante el proceso de dispersión. La micrografía TEM, figura. 1 (d), confirma nuevamente la presencia de las intercaras ZnO-Co3O4 después del proceso de dispersión en seco. The morphology of the raw materials ZnO and Co3O 4 is shown in Figure 1 (ab). The FE-SEM micrograph, Figure 1 (a), shows the typical morphology of the ZnO consisting mainly of elongated prismatic particles and almost cubic particles, with sizes of 0.2-1 .0 fm, and an average particle size of 0.5 fm. The morphology of the Co3O 4 nanoparticles is spherical with a size of 40-50 nm [see insert of Fig. 1 (b)] that form globular agglomerates of sizes between 0.5 to 4 fm Fig. 1 (b) . On the other hand, the FE-SEM image of the ZnO mixture with 10% by weight of Co3O 4 nanoparticles can be seen in the figure. 1 C). The Micrographs show that most of the Co3O 4 agglomerates disappear and the individual nanoparticles are attached to the surface of the ZnO, Fig. 1 (d). The dispersion and adhesion of the nanoparticles could indicate the appearance of Co3O 4 ZnO intercalates at room temperature, due to the high initial reactivity of Co3O 4 and ZnO. All individual nanoparticles disperse below 10% by weight of Co3O 4 , but some agglomerates can be observed for high concentrations of Co3O 4 . This means that for concentrations> 10% by weight, the dispersion limit of the nanoparticles on the ZnO microparticles has been reached. It is characteristic of the process that the morphology of the ZnO particles remains unchanged as a result of the low energy used during the dispersion process. TEM micrograph, figure. 1 (d), again confirms the presence of the ZnO-Co3O 4 interleaves after the dry dispersion process.
Caracterización estructural del sistema Co O4 ZnO Structural characterization of the Co O 4 ZnO system
Los espectros de difracción de rayos X de las materias primas y las mezclas de Co3O4/ZnO, son representadas en la Figura. 2, pueden ser indexadas en base a una mezcla de fase constituido por una fase mayoritaria de ZnO y una minoritaria de Co3O4. Como era de esperar, la intensidad de los picos de difracción de la fase Co3O4se hace cada vez más intensa con el aumento de la concentración de Co3O4. X-ray diffraction spectra of raw materials and mixtures of Co3O 4 / ZnO are shown in the Figure. 2, can be indexed based on a phase mixture consisting of a majority phase of ZnO and a minority of Co3O 4 . As expected, the intensity of the diffraction peaks of the Co3O 4 phase becomes increasingly intense with increasing Co3O 4 concentration.
Con el fin de verificar el efecto de la temperatura del tratamiento térmico en la estructura de fases, las mezclas fueron tratadas térmicamente a 500 °C durante 36 horas. No se observan cambios en el espectro de difracción de rayos X después del tratamiento térmico tal y como se observa en la Figura 2. In order to verify the effect of the heat treatment temperature on the phase structure, the mixtures were heat treated at 500 ° C for 36 hours. No changes in the X-ray diffraction spectrum are observed after heat treatment as seen in Figure 2.
No hay evidencia de Co metálico, CoO o cualquier fase adicional diferente a ZnO, Co3O4 dentro de la resolución que proporciona la técnica de difracción de Rayos X. La reacción esperada entre Co3O4 y ZnO es la formación de una solución sólida Zni-xCoxO con estructura tipo wurtzita, que posee los mismos parámetros de red que los del ZnO. Esto explicaría el hecho de que sólo los picos de difracción de ZnO se observan a 500 °C. Hay poca diferencia entre los radios iónicos del Co+2 (0,058 nm) y Zn +2 (0,060 nm) y, por tanto, cabría esperar un pequeño cambio en el valor del eje c debido a la sustitución de Co+2 en ZnO. A mayor temperatura, la formación de la fase espinela ZnCo2O4 es del mismo modo posible, pero esta fase es isoestructurales con Co3O4, y por lo tanto los patrones de difracción de rayos X no pueden diferenciar entre ambas espinelas. There is no evidence of metallic Co, CoO or any additional phase other than ZnO, Co3O 4 within the resolution provided by the X-ray diffraction technique. The expected reaction between Co3O 4 and ZnO is the formation of a solid Zni -x solution Co x O with wurtzite type structure, which has the same network parameters as those of the ZnO. This would explain the fact that only ZnO diffraction peaks are observed at 500 ° C. There is little difference between the ionic radii of Co +2 (0.058 nm) and Zn +2 (0.060 nm) and, therefore, a small change in the value of the c axis could be expected due to the replacement of Co +2 in ZnO. At higher temperatures, the formation of the ZnCo2O 4 spinel phase is similarly possible, but this phase is isostructural with Co3O 4 , and therefore X-ray diffraction patterns cannot differentiate between both spinels.
Las mezclas de Co3O4 ZnO preparadas por el método de nanodispersión a temperatura ambiente y tratadas térmicamente a 500 °C han sido caracterizadas también mediante espectroscopia Raman y los espectros resultante se muestran en la Figura. 3 (a). El ZnO tiene una estructura tipo wurtzita, con dos fórmulas por celda unidad y simetría C3J . Para esta estructura, la teoría de grupos predice los siguientes modos Raman activos A1+E1+2E2 [24,25]. Estos distintos modos Raman activos del ZnO se pueden observar en la Tabla I, junto con la asignación propuesta. Por otra parte, en la Tabla I también se identifican los principales modos Raman del Co3O4, que se puede observar en los espectros Raman de la figura. 3 (a). Teniendo en cuenta que las estructuras espinelas pertenecen al grupo espacial Fd3m (Oh 7), cabría esperar cinco modos Raman activos (Aig+Eg+3F2g). El óxido de cobalto puro exhibe los cinco modos Raman predichos teóricamente en el rango espectral: Aig (689 cm"1); F2g (619, 521 y 191 cm"1) y Eg (481 cm"1). El modo de alta frecuencia, Aig, se ha asignado a las vibraciones relacionadas con el movimiento de los átomos de oxígeno dentro de la unidad octaédrica de la estructura espinela (por ejemplo, el CoOe en el Co3O4). Su anchura se relaciona con la longitud de los enlaces anión-catión, así como con las distorsiones del poliedro que ocurren en la red de la estructura espinela [26], mientras que los modos F2g y Eg combinan la vibración del tetraedro de la espinela (por ejemplo, el CoO4 en el Co3O4) y los sitios octaédricos [27]. Los espectros Raman del ZnO y del Co3O4 como materias primas y de las mezclas Co3O4/ZnO, son representados en la Figura. 3 (a), pueden ser indexados en base a una mezcla constituida por dos fases, ZnO y Co3O4. Tras el tratamiento térmico de las mezclas Co3O4 ZnO a 500 °C, las bandas Raman del óxido de cobalto presentan cambios. La posible difusión del Zn+2 en la red cristalina de espinela modifica ligeramente las frecuencias de las vibraciones como se observa en la figura. 3 (b), desplazándolas ligeramente hacia el azul. La banda Raman asociada al movimiento de los átomos de oxígeno dentro de la unidad octaédrica, Aig, en el Co3O4 es la más intensa para cualquier concentración de Co3O4. Por otra parte, la nanodispersión de Co3O4 produce un ligero ensanchamiento del modo Raman Aig y la aparición de una doble banda para tratamientos térmicos de 500 °C. La segunda banda se puede atribuir a la aparición de la fase espinela ZnCo2O4 a -714 cm"1 que emerge de forma concomitante, la figura 3 (b). En realidad, para concentraciones de Co3O4 tan bajas como 0,5% en peso, la formación de la espinela ZnCo2O4 es observada claramente. La formación de la espinela requiere una amplia difusión de los átomos de Zn+2 y por lo tanto esta favorecido por el largo tiempo de calcinación a las que son sometidas las mezclas, 36 horas. Recientemente, ha sido descrito en este sistema la formación de la fase espinela a baja temperatura ~ 400 °C [28], que podría estar relacionado con la fenómenos de difusión de cationes de Zn+2. En resumen, la espectroscopia Raman evidencia una reacción de intercara de forma progresiva en las mezclas Co3O4/ZnO, que se produce por la efectiva dispersión de las nanopartículas sobre la superficie del ZnO. Los tratamientos térmicos prolongados a baja temperatura permiten la difusión de los cationes de Zn y por lo tanto la formación de nuevas estructuras de tipo espinela, ZnCo2O4. Los cationes de Zn son activos a temperaturas cercanas a los 400 °C debido a la desorción térmica de Zinc intersticial (Zn¡+) y la formación de vacantes de oxígeno superficiales (V0)s. Este comportamiento facilita la volatilización de los cationes de Zn de la red cristalina de la wurtzita y la difusión del zinc en las partículas más cercanas, en este caso particular Co3O4, promoviendo así la reacción de estado sólido durante el tratamiento térmico [22,29]. Mixtures of Co3O 4 ZnO prepared by the nanodispersion method at room temperature and heat treated at 500 ° C have also been characterized by Raman spectroscopy and the resulting spectra are shown in the Figure. 3 (a). The ZnO has a wurtzite structure, with two formulas per unit cell and C3J symmetry. For this structure, group theory predicts the following active Raman modes A1 + E1 + 2E2 [24,25]. These different active Raman modes of ZnO can be observe in Table I, together with the proposed assignment. On the other hand, Table I also identifies the main Raman modes of Co3O 4 , which can be seen in the Raman spectra of the figure. 3 (a). Given that the spinel structures belong to the space group Fd3m (O h 7 ), five active Raman modes (Aig + E g + 3F 2 g) could be expected. Pure cobalt oxide exhibits the five Raman modes theoretically predicted in the spectral range: Ai g (689 cm "1 ); F 2g (619, 521 and 191 cm " 1 ) and E g (481 cm "1 ). High frequency, Ai g , has been assigned to vibrations related to the movement of oxygen atoms within the octahedral unit of the spinel structure (for example, CoOe in Co3O 4 ) .Its width is related to the length of the anion-cation bonds, as well as with the distortions of the polyhedron that occur in the network of the spinel structure [26], while modes F 2g and E g combine the vibration of the spinel tetrahedron (for example, CoO 4 in Co3O 4 ) and octahedral sites [27] Raman spectra of ZnO and Co3O 4 as raw materials and of Co3O 4 / ZnO mixtures, are represented in Figure 3 (a), can be indexed in based on a mixture consisting of two phases, ZnO and Co3O 4. After heat treatment of Co3O 4 ZnO mixtures at 500 ° C, the s Raman bands of cobalt oxide show changes. The possible diffusion of Zn +2 in the crystalline spinel network slightly modifies the frequencies of the vibrations as shown in the figure. 3 (b), moving them slightly towards blue. The Raman band associated with the movement of oxygen atoms within the octahedral unit, Ai g , in Co3O 4 is the most intense for any concentration of Co3O 4 . On the other hand, the nanodispersion of Co3O 4 produces a slight widening of the Raman Ai g mode and the appearance of a double band for 500 ° C heat treatments. The second band can be attributed to the emergence of the spinel phase ZnCo 2 O to -714 cm 4 "1 emerges concomitantly, Figure 3 (b). In fact, for Co3O 4 concentrations as low as 0.5 % by weight, the formation of the ZnCo 2 O 4 spinel is clearly observed The spinel formation requires a wide diffusion of the Zn + 2 atoms and is therefore favored by the long calcination time to which the mixtures are subjected, 36 hours. Recently, the formation of the spinel phase at low temperature ~ 400 ° C [28] has been described in this system, which could be related to the phenomena of diffusion of cations of Zn +2 . In summary, Raman spectroscopy evidences a progressively intercalating reaction in Co3O 4 / ZnO mixtures, which is produced by the effective dispersion of nanoparticles on the surface of ZnO. Prolonged heat treatments at low temperatures allow the diffusion of Zn cations and therefore the formation of new spinel-like structures, ZnCo 2 O 4 . Zn cations are active at temperatures close to 400 ° C due to the thermal desorption of interstitial Zinc (Zn¡ + ) and the formation of surface oxygen vacancies (V 0 ) s . This behavior facilitates the volatilization of the Zn cations of the crystalline network of wurtzite and the diffusion of zinc in the nearest particles, in this particular case Co3O 4 , thus promoting the solid state reaction during the heat treatment [22,29 ].
Medidas de actividad del sistema catalítico Co3O4/ZnO. Activity measures of the Co3O 4 / ZnO catalytic system.
Según los estudios realizados hasta el momento sobre la reacción de carbonilación de glicerina con urea, urea reacciona con glicerina cuando la mezcla se calienta en presencia de un catalizador. El mecanismo de reacción propuesto sigue cuatro pasos posibles: (I) carbamoilación de glicerina a gliceroluretano (A), (II) carbonilación de gliceroluretano a carbonato de glicerina (4-hidroximetil-1 ,3-dioxolan-2-ona) (B) con abstracción de amoníaco o (III) carbonilación de gliceroluretano a 5-(hidroximetil)oxazolidin-2-ona (C) sin abstracción de amoníaco y (IV) carbonato de glicerina puede reaccionar con otra molécula de urea para dar carbamato de (2-oxo-1 ,3-dioxolan-4-il)metil (D), disminuyendo la selectividad a carbonato de glicerina [15,17], ver Fig 6. According to the studies carried out so far on the carbonylation reaction of glycerin with urea, urea reacts with glycerin when the mixture is heated in the presence of a catalyst. The proposed reaction mechanism follows four possible steps: (I) carbamoylation of glycerin to glycerolurethane (A), (II) carbonylation of glycerolurethane to glycerin carbonate (4-hydroxymethyl-1, 3-dioxolan-2-one) (B) With ammonia abstraction or (III) carbonylation of glycerolurethane at 5- (hydroxymethyl) oxazolidin-2-one (C) without ammonia abstraction and (IV) glycerin carbonate can react with another urea molecule to give (2-) carbamate oxo-1, 3-dioxolan-4-yl) methyl (D), decreasing glycerin carbonate selectivity [15,17], see Fig 6.
La Figura 4 muestra los resultados de actividad obtenidos durante la carbonilación de glicerina utilizando como catalizadores los óxidos puros de Co3O4 y ZnO, el sistema catalítico Co3O4 ZnO preparado por nanodispersion por vía seca a temperatura ambiente y tratado térmicamente a 500 °C/ 36h. El ZnO puro no resultó ser mucho más activo que la reacción sin catalizador, lo que está de acuerdo con los resultados publicados en la bibliografía [30]. Sin embargo, el óxido puro de Co3O4 resultó ser más activo y selectivo. La mezcla de ambos óxidos muestra actividad catalítica dependiendo del procedimiento de preparación y temperatura de tratamiento. La actividad catalítica aumenta de forma considerable con la cantidad de óxido de cobalto dispersado sobre óxido de zinc en las muestras preparadas a temperatura ambiente, sin embargo aumenta ligeramente para la serie de muestras calcinadas a 500°C (Figura 4). Esto demuestra que la calcinación de las muestras disminuye su actividad catalítica. La serie de muestras del 1 % en peso de Co3O4dispersado en ZnO a temperatura ambiente mostraron 100% de selectividad a el carbonato de glicerina pero solo resultaron ligeramente más activas que la reacción blanco sin catalizador; para mayores concentraciones de Co3O4 dispersado sobre ZnO (10% en peso) la conversión alcanza 69% y 97% de selectividad a carbonato de glicerina en 4 horas de reacción. El comportamiento de esta serie difiere de otras ya estudiadas previamente [17], donde se mostraban conversión total y selectividades de alrededor del 75% a carbonato de glicerina en 5 horas de reacción. Por otro lado, la calcinación de la serie Co3O4 ZnO a 500°C no mejora su actividad catalítica respecto a la serie Co3O4 ZnO Figure 4 shows the results of activity obtained during the carbonylation of glycerin using as catalysts the pure oxides of Co3O 4 and ZnO, the Co3O 4 ZnO catalytic system prepared by nanodispersion by dry route at room temperature and heat treated at 500 ° C / 36h. Pure ZnO was not much more active than the reaction without catalyst, which is in agreement with the results published in the literature [30]. However, pure Co3O 4 oxide proved to be more active and selective. The mixture of both oxides shows catalytic activity depending on the preparation procedure and treatment temperature. The catalytic activity increases considerably with the amount of cobalt oxide dispersed on zinc oxide in samples prepared at room temperature, however it increases slightly for the series of samples calcined at 500 ° C (Figure 4). This shows that the calcination of the samples decreases their catalytic activity. The series of samples of 1% by weight of Co3O 4 dispersed in ZnO at room temperature showed 100% selectivity to glycerin carbonate but were only slightly more active than the white reaction without catalyst; for higher concentrations of Co3O 4 dispersed on ZnO (10% by weight) the conversion reaches 69% and 97% selectivity to glycerin carbonate in 4 hours of reaction. The behavior of this series differs from others previously studied [17], where total conversion and selectivities of around 75% to glycerin carbonate were shown in 5 hours of reaction. On the other hand, the calcination of the Co3O 4 ZnO series at 500 ° C does not improve its catalytic activity with respect to the Co3O 4 ZnO series
Cuando las nanopartículas de Co3O4 se dispersan en las micropartículas de ZnO, los sistemas Co3O4 ZnO resultaban catalíticamente más activos ya que el método de preparación por nanodispersión deja bien dispersos en el sistema los centros activos libres Co3O4. Con la calcinación de las muestras el fenómeno que tiene lugar se puede explicar de la siguiente manera: las micropartículas de ZnO puede interactuar con las nanopartículas de Co3O4 y formar especies inactivas tales como ZnCo2O4, lo que se confirma por Espectroscopia Raman, disminuyendo en el sistema el número de centros activos libres de Co3O4. La espinela de óxido de cobalto y zinc, ZnCo2O4, muestra muy poca actividad catalítica debido a la restricción de las especies activas de cobalto en su estructura tetraédrica. Un aumento de la cantidad de óxido de cobalto en el sistema (desde 1 al 10% en peso) conduce a un aumento en la actividad catalítica siendo dicho aumento menos significativo en el caso de las muestras calcinadas ya que la principal fase presente en su composición es la fase inactiva tipo espinela. Por último, el sistema catalítico ZnCo2O4/ZnO resultó ser completamente recuperable y reutilizable hasta tres veces sin mostrar pérdida significativa de actividad y selectividad en la reacción de la carbonilación de glicerina. When the Co3O 4 nanoparticles are dispersed in the ZnO microparticles, the Co3O 4 ZnO systems were catalytically more active since the nanodispersion preparation method leaves Co3O 4 free active centers well dispersed in the system. With the calcination of the samples the phenomenon that occurs can be explained as follows: ZnO microparticles can interact with Co3O 4 nanoparticles and form inactive species such as ZnCo2O 4 , which is confirmed by Raman Spectroscopy, decreasing in the system the number of free active sites Co3O 4. The cobalt and zinc oxide spinel, ZnCo2O 4, shows very little catalytic activity due to the restriction of active cobalt species in their tetrahedral structure. An increase in the amount of Cobalt oxide in the system (from 1 to 10% by weight) leads to an increase in catalytic activity, said increase being less significant in the case of calcined samples since the main phase present in its composition is the inactive spinel type phase. . Finally, the ZnCo 2 O 4 / ZnO catalytic system proved to be fully recoverable and reusable up to three times without showing significant loss of activity and selectivity in the glycerin carbonylation reaction.
Para concluir, los sistemas Co3O4 ZnO preparados por nanodispersion en seco a temperatura ambiente mostraron los mejores resultados comparados con los óxidos puros de partida y con los sistemas Co3O4 ZnO calcinados a 500°C/36h. Concretamente las muestras con concentraciones de Co3O4 elevadas (10 % en peso) mostraron la mejor actividad (por encima de 69% de conversión y 97% de selectividad a carbonato de glicerina) demostrando que una buena dispersión de los centros activos catalíticos de Co3O4 en la interíase del sistema, juega un papel crucial durante la reacción. Los resultados destacan la importancia del método de síntesis utilizado en la preparación de este sistema catalítico heterogéneo. To conclude, Co3O 4 ZnO systems prepared by dry nanodispersion at room temperature showed the best results compared with pure starting oxides and with Co3O 4 ZnO systems calcined at 500 ° C / 36h. Specifically, the samples with high concentrations of Co3O 4 (10% by weight) showed the best activity (above 69% conversion and 97% selectivity to glycerin carbonate) demonstrating that a good dispersion of the active catalytic centers of Co3O 4 At the interface of the system, it plays a crucial role during the reaction. The results highlight the importance of the synthesis method used in the preparation of this heterogeneous catalytic system.
La fenomenología descrita aquí, se puede interpretar como un modelo simple basado en la formación de las intercaras Co3O4 ZnO a temperatura ambiente y la formación de nuevas fases cristalinas, ZnCo2O4, para tratamientos térmicos de baja temperatura, ver Fig. 5. Así por lo tanto, la Figura 5 (a) y (b) muestran una representación esquemática de una partícula individual de ZnO jerárquicamente recubierta con nanopartículas Co3O4 mediante el método de nanodispersion en seco. La dispersión y la adherencia de las nanopartículas puede indicar que se produce una reacción espontánea a temperatura ambiente, entre estos materiales, debido a la alta reactividad inicial del Co3O4 y del ZnO [19]. La Figura 5 (c) muestra la magnificación de la superficie del ZnO donde se puede observar la formación de nuevas intercaras entre las micropartículas de ZnO y nanopartículas de Co3O4. El proceso de nanodispersion en seco realizado para mezclar el ZnO y el Co3O4 crea nuevas superficies reactivas (según lo evidenciado por FE-SEM y TEM) que pueden favorecer la actividad catalítica. Esta nueva forma desaglomeración de nanopartículas ha sido aplicada en la reacción de carbonilación de glicerol con la urea produciendo nuevas propiedades en las intercaras con una alta actividad y selectividad catalítica. La alta reactividad de ZnO puede promover una mayor disponibilidad de cationes de Zn para difundir en las nanopartículas de Co3O4, y por lo tanto formar especies cristalinas estables con estructura espinela, ZnCo2O4, cuando el sistema Co3O4 ZnO fue tratado térmicamente a 500 °C durante 36h como se puede observar en la figura. 5 (d). El tratamiento térmico provoca la formación de especies catalíticamente inactivas como ZnCo2O4 al disminuir el número de sitios activos libres del Co3O4. The phenomenology described here can be interpreted as a simple model based on the formation of the Co3O 4 ZnO intercalates at room temperature and the formation of new crystalline phases, ZnCo 2 O 4 , for low temperature heat treatments, see Fig. 5. Thus, Figure 5 (a) and (b) show a schematic representation of an individual ZnO particle hierarchically coated with Co3O 4 nanoparticles by the dry nanodispersion method. The dispersion and adhesion of the nanoparticles may indicate that a spontaneous reaction occurs at room temperature, between these materials, due to the high initial reactivity of Co3O 4 and ZnO [19]. Figure 5 (c) shows the magnification of the ZnO surface where it is possible to observe the formation of new interleaves between the ZnO microparticles and Co3O 4 nanoparticles. The process performed nanodispersion dry mixing ZnO and Co3O 4 creates new reactive surfaces (as evidenced by FE-SEM and TEM) which can favor catalytic activity. This new form of nanoparticle deagglomeration has been applied in the reaction of glycerol carbonylation with urea producing new properties in the intercars with high activity and catalytic selectivity. The high reactivity of ZnO can promote greater availability of Zn cations to diffuse in the Co3O 4 nanoparticles, and therefore form stable crystalline species with spinel structure, ZnCo 2 O 4 , when the Co3O 4 ZnO system was heat treated to 500 ° C for 36h as can be seen in the figure. 5 d). The heat treatment causes the formation of catalytically inactive species such as ZnCo 2 O 4 by decreasing the number of free active sites of Co3O 4 .
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Claims

REIVINDICACIONES
1 . Procedimiento de obtención de catalizadores que comprende la dispersión en vía seca de nanopartículas o clusters nanoparticulados de tamaño inferior a 100 nm sobre un soporte formado por partículas micrométricas. one . Process for obtaining catalysts comprising the dry dispersion of nanoparticles or nanoparticulate clusters smaller than 100 nm on a support formed by micrometric particles.
2. Procedimiento según la reivindicación 1 donde las nanopartículas o clusters nanoparticulados son óxidos o hidróxidos metálicos que se seleccionan de la lista que comprende óxidos o hidróxidos de aluminio, cobalto, cobre, estaño, níquel, silicio, titanio, zinc, ceño, vanadio, niobio, tántalo, cromo, molibdeno, wolframio, fósforo, antimonio, hierro, circonio o cualquiera de sus combinaciones. 2. The method according to claim 1 wherein the nanoparticles or nanoparticulate clusters are metal oxides or hydroxides that are selected from the list comprising oxides or hydroxides of aluminum, cobalt, copper, tin, nickel, silicon, titanium, zinc, frown, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, phosphorus, antimony, iron, zirconium or any combination thereof.
3. Procedimiento según la reivindicación 2 donde las nanopartículas o clusters nanoparticulados son de óxidos de cobalto. 3. Method according to claim 2 wherein the nanoparticles or nanoparticulate clusters are of cobalt oxides.
4. Procedimiento según la reivindicación 3 donde el óxido de cobalto es Co3O4. 4. The method according to claim 3 wherein the cobalt oxide is Co 3 O 4 .
5. Procedimiento según cualquiera de las reivindicaciones anteriores donde las partículas que forman el soporte son de óxidos metálicos. 5. Method according to any of the preceding claims wherein the particles that form the support are metal oxides.
6. Procedimiento según la reivindicación 5 donde las partículas que forman el soporte son de óxidos o hidróxidos de aluminio, zinc, silicio, titanio, circonio, ceño, niobio, o combinaciones de los mismos. 6. Method according to claim 5 wherein the particles that form the support are of oxides or hydroxides of aluminum, zinc, silicon, titanium, zirconium, frown, niobium, or combinations thereof.
7. Procedimiento según la reivindicación 6 donde las partículas que forman el soporte son de ZnO. 7. Method according to claim 6 wherein the particles forming the support are ZnO.
8. Procedimiento según cualquiera de las reivindicaciones anteriores donde las nanopartículas o clusters nanoparticulados se adicionan a la dispersión en un porcentaje de entre 0,5 a 15 en peso respecto a las partículas del soporte. 8. Method according to any of the preceding claims wherein the nanoparticles or nanoparticulate clusters are added to the dispersion in a percentage between 0.5 to 15 by weight with respect to the particles of the support.
9. Procedimiento según cualquiera de las reivindicaciones anteriores donde los materiales precursores de las nanopartículas y del soporte se someten a un tratamiento de secado. 9. Method according to any of the preceding claims wherein the precursor materials of the nanoparticles and the support are subjected to a drying treatment.
10. Procedimiento según cualquiera de las reivindicaciones anteriores donde los catalizadores obtenidos se someten a un tratamiento térmico. 10. Method according to any of the preceding claims wherein the catalysts obtained are subjected to a heat treatment.
1 1 . Catalizador obtenible por el procedimiento según cualquiera de las reivindicaciones anteriores. eleven . Catalyst obtainable by the process according to any of the preceding claims.
12. Uso del catalizador según la reivindicación 1 1 para la carbonilación de glicerina con urea. 12. Use of the catalyst according to claim 1 for the carbonylation of glycerin with urea.
PCT/ES2011/070504 2010-08-06 2011-07-08 Catalysts organized hierarchically by means of dry nanodispersion WO2012017115A1 (en)

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