J. Aguado

King Juan Carlos University, Madrid, Spain

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Publications (65)151.33 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Fuel production from plastics is a promising way to reduce landfilling rates while obtaining valuable products. The usage of Ni-supported hierarchical Beta zeolite (h-Beta) for the hydroreforming of the oils coming from LDPE thermal cracking has proved to produce high selectivities to gasoline and diesel fuels (>80%). In the present work, the effect of the Ni loading on Ni/h-Beta is investigated in the hydroreforming of the oils form LDPE thermal cracking. h-Beta samples were impregnated with Ni nitrate, calcined and reduced in H2 up to 550°C to achieve different Ni contents: 1.5%, 4%, 7% and 10%. Larger and more easily reducible metal particles were obtained on Ni 7%/h-Beta and Ni 10%/h-Beta. Hydroreforming tests were carried out in autoclave reactor at 310°C, under 20bar H2, for 45min. Ni content progressively increased the amount of gases at the expenses of diesel fractions, while gasoline remained approximately constant about 52-54%. Maximum selectivity to automotive fuels (∼81%) was obtained with Ni 7%/h-Beta. Ni loading also enhanced olefins saturation up to Ni 7%/h-Beta. High cetane indices (71-86) and octane numbers (89-91) were obtained over all the catalysts. Regarding the different studied Ni contents, Ni 7%/h-Beta constitutes a rather promising catalyst for obtaining high quality fuels from LDPE thermal cracking oils.
    Waste Management 11/2014; · 3.16 Impact Factor
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    ABSTRACT: The deactivation and regeneration of Ni supported over hierarchical Beta zeolite catalyst was investigated. Ni/h-Beta was deactivated by coke deposition during the hydroreforming of the product from LDPE thermal cracking, being this coke mostly located inside the micropores (71% coverage). Its regeneration by calcination in stagnant air at 550 °C followed by reduction under H2 up to 550 °C removed largely the coke and retrieved its activity. During the cycle of reaction–regeneration, the nickel particles fractured and moved out to the external surface forming larger size polynanocrystalline aggregates. NH3 TPD proved that the total acidity of the catalyst increased slightly after the regeneration treatment. No collapse of the structure of the Beta structure was appreciated although some changes of the textural properties of the catalyst were observed after the regeneration treatment. The hydroreforming tests pointed out that, after the regeneration, the hydrocracking augmented originating lighter products (gases and gasolines), due to the stronger acidity. The olefins were largely hydrogenated (>90%) while the amount of aromatics and isoparaffins decreased, likely because of the worse hydrogen transfer provoked by nickel sintering or to steric hindrances caused by the lower pore volumes detected. The main changes were observed after the first cycle, so a rather stable catalyst was obtained afterwards.
    Fuel 07/2013; 109:679–686. · 3.41 Impact Factor
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    ABSTRACT: Hierarchical ZSM-5 zeolites were prepared by crystallization of silanized protozeolitic units employing silylated polypropylene oxide diamine polymers as organosilanes. The influence of the (Sipol/Sigel) molar ratio was investigated within 0–0.15 range. High synthesis yields (∼90%) of well-crystallized hierarchical zeolites exhibiting a high proportion of secondary porosity (additional to the zeolitic micropores) was reached for (Sipol/Sigel) molar ratios lower than 0.08. The usage of the silylated polymer resulted in hierarchical ZSM-5 with larger mesopores (4–20 nm) in higher share than the hierarchical ZSM-5 prepared with a smaller organosilane (phenyl-aminopropyl-trimethoxysilane, PHAPTMS). However, it also contained meaningfully lower amount of acid sites and with less acid strength. The best catalytic performance in the cracking of low density polyethylene (LDPE) was showed by the material prepared from a (Sipol/Sigel) ratio of 0.03. Noteworthy, in addition to the gasoline range fraction (C6–C12), light C1–C5 olefins are the main reaction products, which are interesting feedstock for the petrochemical industry. Its catalytic performance is similar to the hierarchical ZSM-5 prepared using the smaller organosilane (PHAPTMS), which is indicative that the enhanced accessibility to the acid sites due to the presence of larger mesopores (4–20 nm) makes up for the lower amount and strength of its acid sites. Thereby, it is possible to enhance the mesoporosity by using bulkier organosilane (silylated polymers) but at the expense of losing acid properties.
    Catalysis Today 01/2013; · 3.31 Impact Factor
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    ABSTRACT: The thermal cracking at 400 °C of pure polyolefins—low density polyethylene (LDPE), high density polyethylene (HDPE) and polypropylene (PP) and a standard polyolefin mixture (46 % LDPE + 27 % HDPE + 28 % PP)—was studied together with the catalytic hydroreforming of the obtained oils over Ni/h-beta at 310 °C under 20 bar of hydrogen. The oils obtained after the thermal cracking of PP contain the highest amount of gasoline (58 %), while those coming from HDPE the lowest (39 %). The bromine index of the oils was very high, ranging from 54.1 (LDPE) to 83.8 (PP), indicating a high olefinic content of the oils. Additionally, the thermal cracking of the mixture indicates the occurrence of a synergestic effect among plastics, with transfer of methyl groups from PP to polyethylenes. Ni/h-beta (Si/Al = 25; Ni content = 6.2 wt%) catalyst was used in the hydroreforming since it contains a bimodal pore size distribution (0.6/3.1 nm), which improves accessibility of the oil molecules to the catalytic sites. After the hydroreforming and regardless of the plastics used, the share of lighter products (gasoline and gases) increases, reaching a remarkable 68 % of gasolines with the oils coming from PP. Regardless of the starting feed, the amount of useful fuels (gasoline + light diesel) was within 80–85 %. Additionally, the oils were successfully hydrogenated since the bromine indexes dropped below 7, indicating that more than 90 % of the starting olefins were saturated. The usage of catalysts increased the amount of aromatics in the obtained oils within 13–20 %, depending on the starting plastic. Likewise, the isoparaffin content of the gasolines was within 35–40 %, except for PP, where it was enhanced to 62 %. However, the research octane number (RON) of the gasolines from LDPE and PP and the cetane indexes of the diesel from all the plastics were promising for their application as fuels.
    Journal of Material Cycles and Waste Management 10/2012; 14(4). · 0.83 Impact Factor
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    ABSTRACT: The present review is aimed at exploring the field of the catalytic cracking of polyolefins over solid acids, focusing on the role played by the catalysts toward the synthesis of fuels and chemicals as well as on the reaction systems currently used. Initially, conventional solid acids, such as micrometer sized crystal zeolites and silica–alumina, were used to establish the relationship among their activity, selectivity, and deactivation in the polyolefin cracking and the inherent properties of the catalysts (acidity, pore structure); however, the occurrence of steric and diffusional hindrances for entering the zeolite micropores posed by the bulky nature of the polyolefins highlighted the importance of having easily accessible acid sites, either through mesopores or by a high external surface area. This fact led toward the investigation of mesoporous materials (Al-MCM-41, Al-SBA-15) and nanozeolites, which allowed increasing the catalytic activities, especially for the case of polypropylene. Further advances have come by the application of hierarchical zeolites whose bimodal micropore–mesopore size distribution has turned them into the most active catalysts for polymer cracking. In this regard, hierarchical zeolites may be regarded as a clear breakthrough, and it is expected that future research on them will bring new achievements in the field of catalytic cracking of polyolefins. In addition, other materials with high accessibility toward the active sites, such as extra-large pore zeolites, delaminated zeolites, or pillared zeolite nanosheets, can also be considered potentially promising catalysts. From a commercial point of view, two-step processes seem to be the most feasible option, including a combination of thermal treatments with subsequent catalytic conversion and reforming, which allows the catalytic activity to be preserved against different types of deactivation.
    ACS Catalysis 08/2012; 2(9):1924–1941. · 7.57 Impact Factor
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    ABSTRACT: The oil obtained from the thermal cracking of low-density polyethylene (LDPE) is formed mainly by linear hydrocarbons with a high quantity of olefins, which hinders the possible application of this product in the formulation of transportation fuels. However, hydroreforming of this oil using bifunctional catalysts with high accessibility to the active sites would allow for the properties of the gasoline and diesel fractions to be significantly upgraded. This is the case of the catalyst employed here because it consists of hierarchical Beta zeolite (with a bimodal micro-mesoporosity) and containing 7 wt % Ni. The presence of nickel in the catalyst increased the share of gasolines with regard to the h-Beta support. The effect of the main variables involved in the hydroreforming process has been investigated and optimized, showing that the extent of hydrocracking is favored when increasing the temperature, the pressure, and the catalyst/feed ratio, leading to enhanced gasoline yields at the expense of heavy (C19–C40) and especially light (C13–C18) diesel fractions because of the faster diffusion of the latter. Ni/h-Beta proved to be an especially adequate catalyst for obtaining gasolines; therefore, a maximum in the selectivity toward gasoline (up to 68.7%) was found in the hydroreforming at 40 bar of hydrogen pressure. On the other hand, the values of the bromine index indicated that 80–100% of the olefins present in the raw oil were hydrogenated depending upon the reaction conditions. In addition, the Ni/h-Beta catalyst showed high activity for aromatization and, especially, hydroisomerization reactions. Thus, a 53% share of isoparaffins in the gasolines was obtained at long reaction times. The gasoline and diesel fractions obtained showed a high research octane number (RON) (>80) and cetane indexes above specifications (>70), respectively, which is indicative of their high quality as transportation fuels.
    Energy & Fuels 06/2012; 26(6):3187–3195. · 2.73 Impact Factor
  • ChemInform 12/2011; 42(50).
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    ABSTRACT: The hydroreforming of the liquid product resulting from LDPE thermal cracking at 400°C (C5–C40) has been studied using Ni supported hierarchical zeolites (Ni/h-ZSM-5, Ni/h-Beta) and mesostructured materials (Ni/Al-MCM-41 and Ni/Al-SBA-15) as catalysts. Hydroreforming experiments were carried out at 310°C under 20bar of hydrogen. All the catalysts were synthesized with a Si/Al atomic ratio of 30 and a Ni content of 7wt%. According to XRD, TPR and TEM data, the activated catalysts displayed Ni particles both over the external surface and inside the catalyst pores in different percentages depending on their porous structure and nature. Complete hydrogenation of the olefins was observed over both mesostructured catalysts (Ni/Al-SBA-15 and Ni/Al-MCM-41) and hierarchical Ni/h-Beta. In contrast, over Ni/h-ZSM-5, there is always left about 30% of olefins, due to an imbalance in the acid and metal function. Ni/h-ZSM-5 led towards significant amounts of gases (∼18%) while gasoline range hydrocarbons were the main products (55%) over Ni/h-Beta, at the expense of diesel fractions. In contrast, the hydrocracking extent was far lower over Ni/Al-MCM-41 and Ni/Al-SBA-15, the latter showing additionally the appearance of a slight degree of oligomerization, which led towards an increase in the heavy diesel fraction (C19–C40). Hydroisomerization reactions also occur, mostly in the case of Ni supported hierarchical zeolites. Likewise, aromatics were formed over these catalysts in a large extent. The RON number of the gasolines obtained at 310°C was within 81–89 depending on the chosen catalysts while the cetane index (CCI) of the diesel fraction was around 70–80. On the other hand, Ni leaching was not detected.
    Applied Catalysis B Environmental 08/2011; 106(3):405-415. · 6.01 Impact Factor
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    ABSTRACT: Hierarchical ZSM-5 zeolite has been synthesized by means of a method involving a precrystallization stage to form the protozeolitic units, the addition and subsequent grafting of both silanization and alkoxylation agents, and a final hydrothermal crystallization. The influence of the alkoxylation with different alcohols (methanol, ethanol, 2-propanol and n-butanol) on the properties of the final hierarchical ZSM-5 samples has been investigated. In every case, the alcohol addition increased the incorporation of the seed silanization agent as it decreases the gel viscosity. In addition, the presence of alcohols deeply affects the physicochemical properties of the final materials. The samples prepared with 2-propanol and methanol were highly crystalline and presented improved textural properties with regard to the reference h-ZSM-5 and n-ZSM-5. In contrast, the samples obtained with ethanol and n-butanol were partially and totally X-ray amorphous, respectively. 1H and 13C-CP solid state MAS NMR spectra proved the alkoxylation of the external surface of the protozeolitic units. Catalytic cracking of LDPE pointed out the higher TOF values obtained over the hierarchical samples prepared with methanol and 2-propanol due to a right combination of accessibility and crystallinity in these materials. The differences observed among the samples prepared with alcohols were ascribed to the strong interaction produced between the silanization agent and the linear alcohols on the surface of the protozeolitic nanounits, which form a very stable protective layer, hindering their aggregation and subsequent crystallization.
    Catalysis Today 06/2011; 168(1):86-95. · 3.31 Impact Factor
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    ABSTRACT: Two series of hierarchical nanocrystalline ZSM-5 zeolites prepared by different synthesis strategies (at low temperature and from silanized seeds) and with external surface areas ranging from 150 to 250 m2 g-1 were tested in the cracking of pure LDPE and HDPE at 340ºC and of waste polyethylene at 360ºC. Hierarchical zeolites showed quite higher activity, with values even 6 times higher than a standard nanocrystalline sample used as reference (n-HZSM-5). The activity values decreased from LDPE to HDPE due to the occurrence of some degree of branching in the former polymer, which act as preferential cracking sites. The major products were C1 - C4 hydrocarbons (in the range 30 - 70%, mostly C3 - C4 olefins) and C5 - C12 hydrocarbons (20 - 60%), whose share depends on both the polyolefin and the catalyst. The amount of C13 - C40 hydrocarbons was practically negligible (< 1%) due to the high acid strength of the zeolites which promotes end-chain cracking reactions. Likewise, hierarchical nanocrystalline HZSM-5 zeolites prepared from silanized protozeolitic units showed higher activities than the hierarchical nanocrystalline HZSM-5 samples synthesized at low temperature and atmospheric pressure. The differences were especially remarkable in the case of waste polyethylene cracking. These results were ascribed to the stronger acidity of the hierarchical zeolite samples prepared from silanized seeds.
    Journal of Catalysis 11/2010; · 6.07 Impact Factor
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    ABSTRACT: Mesostructured Phillips catalysts (Cr/SBA-15 and Cr/Al-SBA-15) with different morphologies were synthesized and tested in ethylene polymerization. Morphological properties of mesoporous supports were modified by changing some synthesis variables like stirring rate, concentration of silica source, mixture acidity and the type of cosolvent molecule. Obtained solids were calcined and characterized by N2 adsorption–desorption, XRD, 27Al NMR and SEM. By decreasing the stirring rate during the synthesis, the size and shape of SBA-15 particles changes from small fibre-like to larger irregular agglomerates. As well, a higher amount of sphere-like particles were obtained by increasing TEOS/P123M ratio. On the contrary, for Al-SBA-15 material, agglomerated particles were obtained even at high stirring rate, but no sphere-like particles were observed by increasing the TEOS/P123M ratio. The increase of HCl/P123M ratio clearly modifies the SBA-15 particle morphology but the structure becomes disordered. Cosolvent incorporation in the SBA-15 synthesis produces a swelling effect in the order trimethylbencene > n-decane > toluene. Only the addition of toluene affects SBA-15 morphology from sphere-like to fibre-like particles.Chromium catalysts prepared by impregnation of SBA-15 supports synthesized at lower stirring rates (50 rpm) present higher activity in ethylene polymerization and produce polymers with larger particle size. On the other hand, Cr/SBA-15 catalysts lead to polyethylenes with slightly lower molecular weight and melting point than traditional Phillips catalyst like Cr/SiO2.
    Microporous and Mesoporous Materials 06/2010; 131:294-302. · 3.21 Impact Factor
  • J. Aguado, J.M. Escola, M.C. Castro
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    ABSTRACT: The influence of the thermal treatment over the textural properties of sol–gel mesoporous γ-Al2O3 (SGAL) synthesized in acid medium using cationic surfactants (e.g., hexadecyltrimethylammonium chloride/bromide) as templates was investigated. BET surface areas steadily decreased (at most 20–25%) on increasing either time or temperature of the conventional calcination, with a observed phase change to δ-Al2O3 at 700 °C. Controlled thermal treatment at 550 °C allowed for a more ordered condensation between aluminium oxo/hydroxo layers reducing grain growth, that disorders the mesostructured framework and decreases BET surface areas to 250–350 m2 g−1. Among the different heating procedures tested, method B, which comprises an isothermal step at 150 °C under flowing nitrogen, led towards the most remarkable results (mesoporous γ-Al2O3 with BET area ∼ 690 m2 g−1, Dp = 2.0 nm and Vp ∼ 0.49 cm3 g−1). XRD and 27Al MAS NMR bore out a mesoporous alumina framework formed mostly by γ-Al2O3 nanocrystals with an AlVI/AlIV ratio ∼4.1, with a slightly higher share of AlV (7.4%). Different alkyltrimethylammonium bromide surfactants (alkyl ∼ C10–C18) were used for the preparation of SGAL aluminas, leading also towards meaningfully better materials under thermal treatment B (SBET ∼ 570–700 m2 g−1, Dp = 2.0–2.3, Vp = 0.45–0.50 cm3 g−1) with the only exception of the C18 alkyl chain surfactant, due to the appearance of a lamellar phase.
    Microporous and Mesoporous Materials 03/2010; 128(s 1–3):48–55. · 3.21 Impact Factor
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    ABSTRACT: This paper deals with the potential of using sequential pyrolysis and catalytic reforming for the conversion of agriculture film waste into useful hydrocarbon products. The experiments were conducted in a two-step reaction system consisting of a pyrolytic batch reactor (450 °C) connected in series to a secondary fixed bed reactor where the organic vapors were reformed at temperatures between 425 and 475 °C. Two conventional zeolites (HZSM-5 and Beta) and a mesostructured aluminosilicate Al-MCM-41 were used as catalysts in the reforming stage. Conversion values were not affected by the temperature in the reforming stage and remained fairly constant in all the experiments (89−92 wt %). In the absence of catalyst, the process generated a high proportion of hydrocarbons in the gasoline (C5−C12) and diesel (>C13) range (between 51 and 56 wt % and between 18 and 19 wt %, respectively) and a consequently lower amount of light hydrocarbon products (between 17 and 23 wt %), all of which consisted essentially of a mixture of n-paraffins and olefins. Catalytic reforming over HZSM-5 favored the formation of light hydrocarbons (up to 53 wt %) consisting primarily of C3 and C4 olefins. Catalytic reforming over HZSM-5 also favored the formation of aromatics (up to 12.7 wt %), iso-parafins (8.9 wt %), and naphthenes (4.0 wt %) in the gasoline (C5−C12) fraction. Owing to their weaker acid properties, zeolite Beta and Al-MCM-41 exhibited inferior reforming activities to zeolite HZSM-5, as evidenced by the lower proportion of light hydrocarbons products and the reduced concentration of nonparaffinic products in the heavier fractions. The influence of reforming temperature on product distribution was not significant in the range 425−475 °C.
    Industrial & Engineering Chemistry Research - IND ENG CHEM RES. 09/2009; 48(18).
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    ABSTRACT: A method for immobilization-stabilization of thermolysin onto activated agarose gels is reported based on the formation of covalent bonds between the enzyme and the support. All derivatives prepared retained 100% of the enzymatic activity and they show higher stability than free thermolysin. The effect of different variables concerning the strength of the enzyme-support attachment on the stability of the immobilized thermolysin derivatives has been established under different inactivation conditions: presence of a water miscible solvent (DMF); stirred biphasic systems, 1, 2-dichloroethane/acetate buffer; acid conditions (pH = 3) as well as in the absence of calcium ions. The possible reactivation of the derivatives inactivated by the loss of calcium ions was also studied.
    Biocatalysis and Biotransformation 07/2009; 15(3):159-173. · 1.09 Impact Factor
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    ABSTRACT: The thermal cracking of HDPE in the presence of different amounts of phenol has been studied and compared with the reaction carried out without this solvent. HDPE conversion is enhanced with the amount of solvent, reaching a value of nearly 100% using a 1/10 HDPE/phenol ratio. The yield of the gaseous hydrocarbons also rose with the amount of phenol, olefins being the main products in this fraction. In all reactions, the main products of the C5–C32 fraction were linear hydrocarbons such as n-paraffins and α-olefins. The yields of both hydrocarbons increased in line with the amount of phenol. However, the increase was more significant in the case of α-olefins. All these results indicate that the phenol promotes the plastic degradation, enhancing the HDPE conversion and facilitating the formation of specific products. A reaction mechanism is proposed to explain these results, indicating random scissions and chain reactions which are favoured by the presence of this solvent during the HDPE thermal degradation.
    Journal of Analytical and Applied Pyrolysis 05/2009; 85(1):366-371. · 3.07 Impact Factor
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    ABSTRACT: Surface-passivating silanization of protozeolitic units has been shown to be an effective strategy for the preparation of ZSM-5 nanocrystals, showing a controlled aggregation degree and a hierarchical porosity. ZSM-5 zeolite materials are thus obtained with adjustable and relatively uniform mesoporosities that have a strong influence on resulting macroscopic reaction properties, especially for macromolecular reagents. The mean sizes of the nanounits and, therefore, the textural and accessibility of these materials can be varied by changing the precrystallization conditions and the concentration of the seed-silanization agent. In addition to conventional characterization techniques, solid-state two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy measurements and the application of the NLDFT model to the argon adsorption isotherms have allowed both the local and the mesoscopic compositions, as well as the structures of the hierarchically porous ZSM-5 materials, to be established. The resulting combination of mesopore sizes and exterior-nanocrystal surface properties of the hierarchically structured ZSM-5 zeolites is shown to catalyze reactions that are otherwise limited by steric and/or diffusional limitations, as demonstrated by their enhanced activity for polyethylene cracking.
    Chemistry of Materials - CHEM MATER. 02/2009; 21(4).
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    ABSTRACT: Beta zeolite with hierarchical porosity has been obtained by a new synthesis strategy, based on perturbing the growth of the zeolite crystals by functionalization of the zeolitic seeds with organosilanes in order to hinder and prevent their further aggregation and agglomeration. As a consequence, a secondary porosity in the supermicropore region has been generated in zeolite Beta, leading to a considerable increase in both the total surface area and the pore volume of the material. The enhancement of the textural properties can be controlled by changing the silanization agent molecular size and its quantity added to the synthesis medium. This type of hierarchical Beta zeolites presents interesting applications as catalysts in reactions involving bulky molecules. Thus, their catalytic activity in the catalytic cracking of LDPE has been found to be strongly enhanced compared to a standard Beta zeolite sample, due to the higher accessibility to the acid sites caused by the presence of the secondary porosity.
    Microporous and Mesoporous Materials 11/2008; 115(3):504-513. · 3.21 Impact Factor
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    ABSTRACT: Feedstock recycling of plastic waste by thermal and catalytic processes is a promising route to eliminate this refuse (which is harmful to the environment) by obtaining, at the same time, products that are useful as fuels or chemicals. During the past decade, this option has undergone an important evolution from a promising scientific idea to an alternative that is very close to reality with commercial opportunities. Thus, several commercial processes have been developed worldwide, most of them especially addressed toward the preparation of diesel fuel. The present review highlights the most remarkable achievements of the field, providing a fundamental insight into this fascinating area and highlighting the main milestones that should be achieved in the next future for this alternative to become applied commercially on a large scale.
    Industrial & Engineering Chemistry Research 10/2008; 47(21). · 2.24 Impact Factor
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    ABSTRACT: New CrAlSBA-15 mesoporous materials have been prepared by direct synthesis and characterized by ICP-AES, XRD, N2 adsorption, 27Al NMR, TEM, UV–vis and H2-TPR. CrAlSBA-15 materials exhibited high mesostructural order starting from chromium(III) nitrate (Si/Cr = 66; Si/Al = 35 at pH 3) and from chromium(III) acetate hydroxide (Si/Cr = 39; Si/Al = 51 at pH 1.5). The incorporation of chromium and aluminium into SBA-15 mesoporous structure is enhanced by increasing the pH and produces an increase in pore size and pore volume. After calcination, samples prepared by one-step synthesis showed Cr(VI) centres well dispersed with a proportion of chromate species higher than Cr/AlSBA-15 catalysts prepared by impregnation and grafting. H2-TPR measurements showed that only the 80% of Cr(VI) ions incorporated into the SBA-15 structure were reduced, so part of chromium ions may be located in non-accessible positions inside the solid walls.CrAlSBA-15 materials obtained by direct synthesis exhibited higher ethylene polymerization activity (381.1 kg PE/g Cr h) than Cr/AlSBA-15 and conventional Cr/SiO2 Phillips catalyst prepared by impregnation (260.5 and 216 kg PE/g Cr h, respectively).
    Chemical Engineering Journal 04/2008; 137(2):443-452. · 4.06 Impact Factor
  • D. P. Serrano, J. Aguado, C. Vargas
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    ABSTRACT: Mesostructured SBA-15 materials, with both pure silica and aluminosilicate compositions, have been investigated as supports for the heterogenization of the chiral Mn(salen) catalyst using different methods: impregnation, direct ion exchange, indirect ion exchange, and coordinative anchoring on organosilica-functionalized supports. In the last case, two different types of SBA-15 functionalization agents were tested: aminopropyltrimethoxysilane and aminophenyltrimethoxysilane. In all the methods studied, the incorporation of the Mn(salen) catalyst does not modify the SBA-15 structure although a significant decrease in the surface area, pore volume and pore size is observed. Enantioselective styrene epoxidation using m-CPBA as oxidant and NMO as co-oxidant has been used as test reaction for the different heterogeneous catalysts synthesized. The stability of the heterogenized systems has been studied by carrying out reusing tests. The main problem encountered is the extensive leaching of the Mn(salen) complex that occurs with most of the catalytic systems. However, a significant stability has been found for the catalyst prepared by anchoring the Mn(salen) complex on a SBA-15 support previously functionalized with aminophenyltrimethoxysilane. In this case, the extension of the Mn(salen) leaching has been reduced below 10% by increasing both the styrene/oxidant and catalyst/styrene ratios.
    Applied Catalysis A General 02/2008; 335(2):172-179. · 3.67 Impact Factor

Publication Stats

1k Citations
151.33 Total Impact Points

Institutions

  • 2001–2014
    • King Juan Carlos University
      • Chemical and Environmental Technology
      Madrid, Spain
  • 1992–2009
    • Universidad Complutense de Madrid
      • Departamento de Ingeniería Química
      Madrid, Madrid, Spain
  • 2006
    • University of Hamburg
      • Technical and Macromolecular Chemistry
      Hamburg, Hamburg, Germany