Simoni Margareti Plentz Meneghetti

Transformação de triglicerídeos em combustíveis, materiais poliméricos e insumos químicos: algumas aplicações da catálise na oleoquímica

The use of biomass as raw-material for obtaining chemicals, polymers and fuels is emerging as a clever alternative solution for the increasing energy demand, environmental awareness and petroleum shortage. In this work, some attempts in order to develop catalytic systems suitable for triglyceride transformation into fuels, polymers and intermediates are reviewed.

Catalytic production of biodiesel and diesel-like hydrocarbons from triglycerides

Because of their high viscosity and density, crude fats and oils extracted from animal or vegetable sources (containing mainly triglycerides) cannot be directly combusted in modern diesel engines; therefore, they must be converted into biofuels. This important transformation is currently a technological bottleneck for the generation of biofuels either by thermocatalytic cracking to produce diesel-like hydrocarbons or by alcoholysis to yield mono-alcohol fatty acid esters (biodiesel). Although both transformations are relatively simple chemical reactions (thermolysis ((hydro)cracking) and (trans)esterification of triglycerides), they have several drawbacks, mainly related to catalyst efficiency and water and energy consumption. The most recent catalytic approaches and achievements, such as alcoholysis of triglycerides under multiphase conditions using classical acid or base catalysts as well as biocatalysts, are highlighted and discussed.

Sn(IV)-based organometallics as catalysts for the production of fatty acid alkyl esters

This paper discusses mechanistic aspects and applications of organotin(IV) catalysts. Particularly, these complexes are employed in a series of industrial reactions in which esters are obtained via (trans)esterification, e.g., polyesters and lactones. Due to the recent results pointed out in the literature, the potential application of this type of catalyst in the synthesis of fatty acid alkyl esters (FAAEs) is also presented.

Cellulose conversion in the presence of catalysts based on Sn(IV)

A systematic study of the dissolution and conversion of cellulose in the presence of Sn(IV) complexes under several reaction conditions was conducted to evaluate their potential as catalysts. Results were compared with those obtained from non-catalyzed reactions, and from reactions using H2SO4 as a catalyst. Sn(IV) catalysts are capable of converting cellulose into valuable chemicals with interesting yield and selectivity, without the problems associated with the use of inorganic acids in these processes.

Fructose conversion in the presence of Sn(IV) catalysts exhibiting high selectivity to lactic acid

The catalytic performance of a series of Sn(IV)-based organometallic complexes in fructose conversion was studied under several reaction conditions, and the conversion, yields, and selectivity measurements of this transformation have been evaluated. The results were compared to those obtained from non-catalysed reactions and those in the presence of a conventional catalyst (H2SO4). These organometallic Sn(IV)-based catalysts demonstrated the ability to fully convert fructose into valuable chemicals. Under particular reaction conditions, lactic acid is obtained in good yields and selectivity.

Quantum mechanics/molecular mechanics investigation of the ethene polymerization mechanism catalyzed by a bulky diimine-Ni(II) complex

In this work we describe a theoretical investigation of the ethene polymerization reaction catalyzed by a bulky cationic α-diimine Ni(II) complex. We employed the combination of density functional theory (DFT) and molecular mechanics (MM), within the ONIOM approach, to evaluate the structures and energies involved on the most representative reactions observed on ethene polymerization, using the Brookhart catalytic system. All intermediates and transition state structures along these elementary steps were treated as representatives of the polymerization process. We discuss the conformation of the ligands around the active site along the polymerization reaction steps, the coordination angle of the coordinated olefin, p-complexes, and branch formation of the growing chain during the polymerization process.

Catalysts based on TiO2 anchored with MoO3 or SO42− for conversion of cellulose into chemicals

Biomass is composed of a high percentage of cellulosic material, with great potential for transformation into chemical reagents, and thus it is of interest to the chemical, food, medical and fuel industries. The conversion of cellulose was evaluated in the presence of solid acid catalysts based on TiO2 anchored with MoO3 and SO42−. The catalysts were characterized by infrared and Raman absorption spectroscopy, pyridine-adsorption infrared spectroscopy, thermogravimetric analysis, N2 adsorption–desorption isotherms and temperature-programmed desorption of NH3 (NH3-TPD). The catalysts showed low to moderate acid sites: TiO2/MoO3-30 > TiO2/SO42−-35 > TiO2/SO42−-25 > TiO2, and the cellulose conversion was between 27 and 35%.

Synthesis and evaluation of the antibiotic and adjuvant antibiotic potential of organotin(IV) derivatives

A series of organotin(IV) derivatives was investigated in vitro for their antibiotic and adjuvant antibiotic properties (efflux pump inhibitors) against Staphylococcus aureus strains that overexpress efflux pump proteins for norfloxacin (SA-1199B), erythromycin (RN-4220) and tetracycline (IS-58). Most organotin(IV) compounds showed significant antibacterial activity with small Minimum Inhibitory Concentration (MIC) values, some of which were close to 1.0μg/mL (3.1μM), but this feature was also associated with substantial cytotoxicity. Nevertheless, the cytotoxicity of these organotin(IV) compounds can be overcome when they are used as antibiotic adjuvants. Their remarkable adjuvant antibiotic properties allow potentiation of the action of tetracycline (against IS-58 strain) by up to 128-fold. This likely indicates that they can act as putative inhibitors of bacterial efflux pumps. These results reinforce organotin(IV) complexes as promising antibacterial agents, and many of these complexes, if associated with antibiotics, can act as potential adjuvant antibiotic candidates.

Microwave hydrothermal synthesis, characterisation, and catalytic performance of Zn1-xMnxO in cellulose conversion

Wurtzite-type Zn1−xMnxO (x = 0, 0.03, 0.05, 0.07) nanostructures were successfully synthesised using a simple microwave-assisted hydrothermal route and their catalytic properties were investigated in the cellulose conversion. The morphology of the nanocatalysts is dopant-dependent. Pure ZnO presented multi-plate morphology with a flower-like shape of nanometric sizes, while the Zn0.97Mn0.03O sample is formed by nanoplates with the presence of spherical nanoparticles; the Zn0.95Mn0.05O and Zn0.93Mn0.07O samples are mainly formed by nanorods with the presence of a small quantity of spherical nanoparticles. The catalyst without Mn did not show any catalytic activity in the cellulose conversion. The Mn doping promoted an increase in the density of weak acid sites which, according to the catalytic results, favoured promotion of the reaction.

Catalytic Behaviors of CoII and MnII Compounds Bearing α-Diimine Ligands for Oxidative Polymerization or Drying Oils

The oxidative polymerization of linseed oil was investigated comparing the classical catalysts cobalt(II) 2-ethylhexanoate and manganese(II) 2-ethylhexanoate and their derivatives modified by the presence of chelating nitrogen ligands, i.e., 2,2’-bipyridyl, 2-(acetyl-2,6-diisopropylphenylimine)pyridine and [N-(2,6-diisopropylphenyl)imine]acenaphthoquinone. The suitable stoichiometries between the two precursor complexes with the three ligands were determined by UV-visible spectroscopy. All complexes were characterized by infrared spectroscopy, and one complex was characterized also by X-ray diffraction. The apparent kinetic constants of oxidative polymerization of linseed oil was determined, for each catalytic system, via the periodic measurements of the oil viscosity during the oxidation reaction. The results indicated that the modifications of the classical two complexes with the chelating nitrogen ligands improved the catalytic efficiency at least to the manganese complex.