Leandro Pierroni Martins

São Paulo State University | Unesp · Department of Biochemistry and Technology

The oxidation catalysts are essential since the oxidation processes yield 25% of the foremost organic compounds and industrial intermediates. The review considers the fundamental concepts of catalytic oxidation, highlighting acrolein oxidation, the main product of which is acrylic acid. Besides presenting the evolution of catalysts based on mixed o...

BEST PRACTICES AND PITFALLS IN THE MEASUREMENTS OF THE CATALYTIC ACTIVITY OF MATERIALS IN THERMO-CATALYSIS. As catalysis grows as a multidisciplinary research area, many questions arise regarding the procedures used to determine the activity of materials in different chemical reactions. To correct inconsistencies, whether in definitions, concepts,...

Accessibility and amphiphilicity of catalysts play an important role in the ketalization of glycerol with acetone. Delamination and functionalization with organosilane were performed to improve the accessibility and amphiphilicity of MWW zeolites.

Modifying the physical and chemical properties of zeolites by altering the synthesis parameters or using post-synthesis treatments may offer additional properties other than those that make them widely used materials. Remarkably, the chabazite SSZ-13 zeolite possesses a small pore opening that provides access to a large cavity, making the structure...

Operando time‐resolved X‐ray absorption spectroscopy (XAS) was used to determine nickel species supported on porous MgO during the ethanol steam reforming reaction. The Principal Component Analysis (PCA) of the nickel K‐edge XAS spectra revealed Ni(OH)2, NiMgO, and metallic Ni during the activation and reaction of the catalysts. The Multivariate Cu...

The use of zeolites in several fields, especially in base or acid-catalyzed reactions and adsorption, depends on their physical and chemical properties tuned by modification of the synthesis (bottom-up methods) or post-synthesis procedures (top-down). Among the various possibilities, three stand out: (1) the embryonic zeolites, (2) partially formed...

The delamination of MCM-22 using shear forces in a vibratory ball mill, rather than chemical surfactants and sonication, is illustrated. The resulting material has comparable or improved physical properties compared to chemically delaminated MCM-22 without a significant loss of acid sites. The mechanical treatment affected the initial rate of 4-pro...

Glycerol conversion into value‐added chemicals has received much attention due to the prospect of increasing the biodiesel industry‘s profitability. The dehydration of glycerol is one of the most explored reactions in the valorization of glycerol, and the zeolite H‐ZSM‐5 is one of the furthermost used structures. In this study, several characteriza...

The pore size of the chabazite structure is exceptionally suitable for the methanol to olefins (MTO) reaction. The reaction has an induction period required for the formation of a hydrocarbon pool (HP), usually composed of aromatic compounds of different sizes. HP is alkylated by methanol and afterward cracked, leading to the formation of olefins....

This work reports the improved catalytic activity of nickel catalysts supported on nanocrystalline magnesium oxide prepared by a sol–gel method, using Pluronic P123 as a structure-directing agent for pore formation. The presence of Pluronic also provided a reduction of the magnesium oxide crystallite size from 54 to 18 nm, as well as the attainment...

Herein, ZSM-5 zeolites of several Si/Al mole ratios, and varying hydrophobicity were used as catalysts in the ketalization of glycerol. The water formed in the reaction adsorbs on acidic sites, hampering the catalytic conversion of glycerol. The conversion drops even more by adding water in the reaction mixture, intensifying the adsorption in hydro...

Acrylic acid is one of the most attractive products directly produced from glycerol, and many efforts are still made to thoroughly understand the role of different catalytic sites in the reaction. In this work, we prepared Al-free vanadosilicates presenting structures analog to ferrierite and ITQ-6 zeolites (2D and 3D structures). The materials wer...

Porous sulfated zirconia was prepared using a sol-gel process associated with liquid crystal templates (LCTs). Evaluation was made of the effects of the Zr⁴⁺:SO4²⁻ molar ratio and aging time on the formation and stability of the lyotropic arrangement of the LCT gel and the features of the resulting mesoporous powders. Polarized light microscopy and...

Lately, to considerably reduce the diffusion constraints in the catalysis performed by zeolites, there has been significant interest in syntheses of partially formed zeolites with extremely accessible active sites, named embryonic zeolites. Their preparation relies on stopping the crystallization of conventional micron-sized zeolites before the zeo...

Chromium silicates with MFI topology were hydrothermally synthesized, characterized, and applied as heterogeneous catalysts on the one-step gas-phase glycerol conversion into acetaldehyde and acrolein. The catalysts were characterized by XRD, SEM, FT-IR, ICP-OES, XPS, pyridine adsorption, nitrogen adsorption/desorption, and TGA. The experimental re...

The Cover Feature shows vanadium oxide species supported on a lamellar silica and the corresponding oxidation of methanol to formaldehyde on these active sites. In the Full Paper, Luiz H. Vieira et al. explain that surface speciation and active site‐support interactions in these materials play a substantial role in their reactivity. Isolated silano...

Supported transition metal catalysts have been extensively applied to oxidative and reductive processes. The understanding of surface speciation and active site‐support interactions in these materials play a substantial role in developing improved heterogeneous catalysts. Herein, a series of impregnated 3D ferrierite and 2D ITQ‐6 siliceous supports...

The coupling of ethanol to produce C 4 -compounds by Guerbet condensation at 325 °C was studied using porous mixed oxide catalysts of AlMgO and AlCaO prepared by the emulsion mediated method with and without the addition of Cu. The synthesis procedure was effective in preparing materials with higher porosity and BET area. Cu catalysts show improved...

Mixed aluminum and magnesium oxides (AlMgO) prepared by means of an emulsion-mediated sol-gel method was impregnated with copper nitrate solution and used in the ethanol dehydrogenative reactions to produce acetaldehyde and ethyl acetate. The emulsified system allowed to obtain a macro-mesoporous support that resulted in an outstanding dispersion o...

Levoglucosanol (LGOL) is a critical intermediate for the bio-based production of hexane-1,2,5,6-tetrol, 1,2,6-hexanetriol, and 1,6-hexanediol.

Aluminum-free MWW structure containing vanadium was easily prepared from a mixture of suitable templates (N,N,N-trimethyl-1-adamantamonium hydroxide (TMAdaOH) and hexamethyleneimine (HMI)). Besides, the use of VCl3 as vanadium source, in which this metal is in low oxidation state (V³⁺) and the preparation of the synthesis gel under inert atmosphere...

Hierarchical micro-mesoporous MCM-22 zeolites were synthesized using hexamethyleneimine and organosilanes as structure directing agents, which enabled the formation of hierarchical zeolites with mesopores created by the voids left by the organosilanes after thermal treatment, without loss of the intrinsic microporosity of the zeolite. The addition...

The acetalization of acetone with glycerol was investigated using vanadiumimpregnated catalysts. The siliceous supports FER, a purely microporous material, and ITQ-6, a micro/mesoporous material, were obtained from a ferrierite lamellar precursor, PreFER. Both supports were impregnated with 1, 5 or 10 wt.% of vanadium. The structural properties wer...

This study presents an easy route to induce pore formation, increase the specific surface area and control the crystallite size of magnesium oxides obtained using the sol-gel method with addition of Pluronic P123 surfactant. The structural characteristics of the materials were evaluated using X-ray diffraction, N2 physisorption isotherms, mercury i...

The recyclability of coked ethanol steam reforming catalyst (Co/Al 2 O 3 ) is studied during several cycles. Oxidative regeneration burns coke however part of cobalt is oxidized. H 2 produced during reforming promotes the...

Herein, a sol-gel one-pot methodology to tune the activity of Co-catalysts supported on silica-titania to CO oxidation is described. SEM, TEM, EDS, XPS and H2-TPR evidenced a higher Co dispersion from that method when compared to catalysts prepared by impregnation. Furthermore, the simultaneous addition of cobalt oxalate during the incorporation by...

This paper describes the activation and catalytic performance of a multifunctional catalyst consisting of mixed oxides of vanadium and molybdenum supported on an acidic ZSM-5 zeolite. The zeolite was wet-impregnated with an aqueous solution containing a mixture of NH4VO3 and (NH4)6Mo7O24 precursors at a V/(Mo+V) molar ratio of 0.6. Evolution of the...

SiMCM-41 and V-MCM-41 were hydrothermally synthesized with different quantities of vanadium, characterized by small angle X-ray scattering, nitrogen physisorption, and the insertion of vanadium was assessed by temperature-programed desorption of ammonia, pyridine chemisorption followed by infrared spectroscopy and H2 temperature-programed reduction...

Zeolites are solid acids with several industrial applications, but usually their syntheses are difficult or costly and these facts negatively interfere in their use as catalysts or adsorbents. The seed-assisted approach is an alternative to facilitate the zeolite synthesis, shortening crystallization time, the possibility of performing template fre...

The catalytic properties of Mo-V mixed oxides hydrothermally synthetized in the presence of ionic surfactants (SDS and CTAB) were investigated in the gas-phase oxidative dehydration of glycerol. The presence of surfactants promoted a change in morphology of MoV 2 O 8 phase, directing to formation of rod-shaped crystals, and, consequently, an increa...

Mixed oxides of aluminum and magnesium derived from hydrotalcites were prepared by means of a sol–gel method mediated by an emulsified sol as pore template. The emulsion consisted of ethanol as the continuous phase and n-dodecane droplets as the dispersed phase, which was stabilized by the presence of the surfactant Pluronic P123. The use of such a...

Resumo-Abstract RESUMO-O ácido acrílico geralmente é obtido a partir da oxidação do propeno, por meio de duas reações realizadas com condições e catalisadores diferentes. A primeira reação é a para a obtenção de acroleína utilizando catalisadores a base de molibdênio, bismuto e promotores e a segunda reação é a oxidação de acroleína a ácido acrílic...

This paper presents an in situ study of the crystallographic phases formed during the thermal treatment of precursors of vanadium and molybdenum oxides, measured under synchrotron X-ray diffraction. The interest in the speciation of MoxVyOz mixed oxides lies in the excellent catalytic performance of these materials for the selective conversion of g...

A new sol-gel method mediated by the use of paraffin emulsions is presented for the synthesis of hierarchical mesoporous-macroporous Al-Mg hydrotalcites. Prior to the synthesis, the construction of ternary diagrams for paraffin/surfactant/ethanol helped to identify the most suitable compositional synthesis domain. Two distinct regions, denoted L1 (...

Abstract The ZSM-5 zeolite (MFI structure, Si/Al = 40) was treated using NaOH and either oxalic acid or HCl to obtain hierarchical materials with different characteristics, followed by impregnation with vanadium oxides (V2O5) to generate redox-active sites. The impact of the multiple treatments on the efficiency and stability of the catalysts in th...

Vanadosilicates isostructural to ETS-10 and AM-6 microporous materials were synthesized hydrothermally using derivatives of cis- and trans-3,5-dimethyl-piperidine as organic structure directing agents (SDAs) and were subsequently tested as heterogeneous catalysts for the oxidehydration of glycerol to acrylic acid. The best performances were obtaine...

Selective ethanol dehydrogenation using Cu/Al2O3 catalyst was investigated by time-resolved XAS/MS/Raman techniques. On-line monitoring of reaction products revealed that formation of H2 and acetaldehyde occurs over intermediate Cu+ species self-reduced upon reaction and the selectivity to ethyl acetate results of coupling of acetyl and ethoxy spec...

Sulfated zirconia ceramic foams were produced by the sol-gel process using air-liquid foam and surfactants as dual pore templates. The results showed the presence of high porosity (until 93%) and surface area (105 m2g-1), and a hierarchical structure of pores size in the range of macro (between 10 and 76 μm), and meso-scales (3.9 nm). The hierarchi...

The influence on gas-phase catalytic glycerol dehydration of crystal size (S: small, or L: large crystals), acidity, and synthesis procedure for isomorphous incorporation of gallium (Ga-S; Ga-L) or aluminum (Al-S; Al-L) in MFI zeolites was studied. The main product observed was acrolein, with the undesirable parallel formation of deactivating coke...

A tecnologia descrita na presente invenção se refere ao processo de obtenção de ácido acrílico a partir do glicerol, utilizando vanadosilicatos microporosos como catalisadores de maior seletividade, estabilidade frente à deposição de coque e alta conversão de glicerol em ácido acrílico. Ainda, menciona-se a utilização de catalisadores bifuncionais...

Structural and surface features of highly dispersed copper catalysts supported on hierarchical porous alumina were evaluated for the ethanol dehydrogenation reaction. The catalysts were prepared by incipient wetness impregnation of alumina obtained by a dual template sol–gel procedure. Structural characterizations provided evidence that the copper...

Members of the layered MWW family, including microporous MCM-22, pillared MCM-36 and delaminated ITQ-2 zeolites, were used as catalysts for the gas phase dehydration of glycerol. The chemical, structural and surface properties of the catalysts were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, SEM, TEM, NH3-TPD and pyridin...

The catalytic behavior of bifunctional V2O5/MFI catalysts with acid and oxidizing properties was investigated for the gas-phase oxidehydration of glycerol. One of the main reaction products was acrylic acid, produced by dehydration of glycerol to acrolein at an acidic site and subsequent oxidation at a redox site. Comparison of wet impregnation wit...

Porous sulfated zirconia foams were manufactured by a simple methodology based on the sol–gel process combined with a liquid foam template that used a surfactant mixture. A block copolymer (Pluronic F-127) and an anionic surfactant [sodium dodecylsulfate (SDS)] were mixed in different proportions in order to optimize the porous and surface properti...

This work presents a method that enables the synthesis of porous alumina in the presence of different types of surfactant. The method is based on a sol–gel transition, using surfactants and droplets of a nonpolar phase as templates. The main purpose was to establish a relationship between the templates and the resulting pore structure. The results...

Seed-assisted synthesis of zeolites diminishes crystallization time and enables the industrial use of certain zeolites, which was conventionally unfeasible due to the complexity of synthesis and the cost of organic structure-directing agents. This study reports the primary results of zeolite crystallization in the presence of seeds, which are used...

Vanadium-based compounds have received a lot of attention in the last years due to their high and selective catalytic activities in major industrial reactions. The catalytic properties of V2O5 may be strengthened and modified when it is dispersed in pure oxides like SiO2, TiO2, and Al2O3. In this work, mixed oxides V2O5/SiO2, V2O5/TiO2, and V2O5/Al...

In this work, we investigate the correlations between structural and rheological properties of emulsified aqueous sol and the porous microstructure of monolithic zirconia foams, manufactured by the integrative combination of the sol-gel and emulsification processes. Macroporous zirconia ceramics prepared using different amounts of decahydronaphthal...

Hierarchical aluminas with pore sizes ranging from a few nanometers to micrometers were obtained using an one-pot sol–gel synthesis. The aluminas were synthesized under acid conditions from aluminum isopropoxide in presence of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer template and decahydronaphthalene as emu...

Organic-inorganic hybrids constitute a new class of compounds in the research area of materials design. In this context, the preparation of hybrid organic-inorganic catalysts is presented, focusing on catalysts where an organic molecule is ionically bonded to the surface of an inorganic material. The application of this class of hybrid catalysts in...

Bimodal porous alumina catalysts with both continuous macropores and mesopores were prepared using a dual soft template method. The addition of decahydronaphthalene as emulsifier agent successfully contributed to the formation of macropores. The effectiveness of macropore insertion was evaluated in the model reaction of ethanol dehydration at 300 °...

The present work deals with the design and construction of an equipment for studying the drying process of gels and solids. The equipment was built using mainly a commercial oven and others peripherals for programmed control of temperature, humidity and data acquisition. The system allows the in situ monitoring of the gel drying, registering the we...

The present work deals with the design and construction of an equipment for studying the drying process of gels and solids. The equipment was built using mainly a commercial oven and others peripherals for programmed control of temperature, humidity and data acquisition. The system allows the in situ monitoring of the gel drying, registering the we...

A general and potentially easy method of synthesizing aluminas possessing hierarchical pore structure is presented in this paper. This method is based on the integration of the sol–gel process with micelles of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) block copolymer and oil droplets of decahydronaftalen (DHN) as dual pore tem...

In the present work, the basicity of three different Si–MCM-41 mesoporous materials, namely, (1) as-synthesized Si–MCM-41, (2) Si–MCM-41 modified by dispersing cesium oxide (Cs2O) and (3) Si–MCM-41 with anchored aminopropylsilyl group was compared for the first time. The fact that Knoevenagel and Claisen–Schmidt condensations stand out to be import...

A series of as-synthesized molecular sieves have been tested and revealed useful as basic catalysts for Knoevenagel condensation under mild conditions. In order to understand the role of the Si/Al ratio, the structure, porosity and template agent, fifteen structures were synthesized and studied in this reaction. Siliceous and large pore molecular s...

The basicity of methylammonium-faujasite zeolites (FAU) was evaluated in the Knoevenagel and Claisen–Schmidt condensation reactions and in the alcoholysis of propylene oxide with methanol. The basic character of FAU zeolites (Y zeolite with Si/Al=2.5 and X zeolite with Si/Al=1.4) was systematically altered by incorporating cesium and methylammonium...

This work concerns about ion exchange and basic properties evaluation of faujasite zeolites containing alkylammonium cations. The starting materials were sodium FAU zeolites with two Si/Al ratios (1.4 and 2.5) and alkylammonium cations with different degrees of substitution of methyl radical or alkyl chain length. Results showed that aqueous ion ex...

Some silica/surfactant mesoporous materials have been synthesized in water:ethanol mixtures by combining tetraethoxysilane with a CnTMA+Br− solution. The effects of the water:ethanol ratio and water:NH3 ratio on the formation of the mesoporous solid and particle size and morphology of the materials are reported. These as-synthesized Si-MCM-41 mater...

The activity of copper-doped hematite in the SCR with propane, in the presence of oxygen, was evaluated in this work. It was found that copper sulfate led to the production of solids with different specific surface areas depending on the amount of copper. The sulfur and copper species were mainly located on the surface. The copper-containing cataly...

The activity of copper-doped hematite in the SCR with propane, in the presence of oxygen, was evaluated in this work. It was found that copper sulfate led to the production of solids with different specific surface areas depending on the amount of copper. The sulfur and copper species were mainly located on the surface. The copper-containing cataly...

Ion exchange of methylammonium cations (Me) in Na-Y zeolite (FAU) and the properties of the resulting Me-Y material (Me=(CH3)iNH4-i+;i=0–4) was studied. Results indicated that the ion exchange equilibrium can quickly be reached, even when voluminous tetramethylammonium cations are used. XRD results indicated that the cation distribution along zeoli...

Si-MCM-41 molecular sieves, which are largely used in a number of acid and redox catalyzed reactions, as reported by the literature, were used as basic catalyst for the Knoevenagel condensation. This reaction involves the condensation of carbonyl compounds with active methylene compounds to generate unsaturated products. The catalyst, which pores w...

Catalysis by solid acids has received much attention due to its importance in petroleum refining and petrochemical processes. Relatively few studies have focused on catalysis by bases and even les on using basic molecular sieves. This paper deals with the potential application of micro and mesoporous molecular sieves in base catalysis reactions. Th...

Catalysis by solid acids has received much attention due to its importance in petroleum refining and petrochemical processes. Relatively few studies have focused on catalysis by bases and even les on using basic molecular sieves. This paper deals with the potential application of micro and mesoporous molecular sieves in base catalysis reactions. Th...

|Cu x|[Si yAl]-MFI and |Co x|[Si yAl]-MFI catalysts were prepared by ion exchange from |Na|[Si yAl]-MFI zeolites (y = 12, 25 and 45). The activity of the catalysts was evaluated in the reduction of NO to N2 in an oxidative atmosphere using propane or methane as reducing agents. The Cu catalysts were only active with propane and they presented highe...

SBA-15 was prepared under reflux, resulting, unlike SBA-15 prepared under autogenous pressure, in a mesoporous material with thicker pore walls but with a slightly smaller unit cell parameter and pore diameter. Under the conditions employed, only a very minor portion of the aluminum present in the reaction mixture was found to have been incorporate...

ZSM-5 catalysts containing either Cu or Co cations individually or Cu/Ca or Co/Ca cation combinations were prepared by ion exchange. These materials were tested as catalysts for the reduction of NO to N2 in the presence of propane or methane. Cu2+ and [Cu-O-Cu]2+ species were identified in ion exchangeable sites in the copper-containing catalysts....

Products resulting from the ethoxylation of hydroxylated compounds, especially water and ethanol, are of great commercial importance. This work presents several aspects concerning the catalytic reactions of ethylene oxide, a chemical substance used in the production of a wide variety of products. Mechanisms of ethoxylation, distribution of products...

Products resulting from the ethoxylation of hydroxylated compounds, especially water and ethanol, are of great commercial importance. This work presents several aspects concerning the catalytic reactions of ethylene oxide, a chemical substance used in the production of a wide variety of products. Mechanisms of ethoxylation, distribution of products...