Paulo A. Z. Suarez

The use of new ionic liquids in two-phase catalytic hydrogenation reaction by rhodium complexes

Abstract The reaction of 1-n-butyl-3-methylimidazolium chloride (BMIC) with sodium tetrafluoroborate or sodium hexafluorophosphate produced the room temperature-, air- and water-stable molten salts (BMI+)(BF4−) (1) and (BMI+)(PF6−) (2), respectively, in almost quantitative yield. The rhodium complexes RhCl(PPh3)3 and [Rh(cod)2][BF4] are completely soluble in these ionic liquids and they are able to catalyse the hydrogenation of cyclohexene at 10 atm and 25°C in a typical two-phase catalysis with turnovers up to 6000.

Physico-chemical processes in imidazolium ionic liquids

Among the various properties exhibited by ionic liquids (ILs)--especially those based on the imidazolium cation-their inherent ionic patterns, very low vapour pressure and pronounced self-organization in the solid, liquid and even in the gas phase are particularly interesting since this allows the use of these fluids as alternative and complementary media to classical organic solvents and water in many applications. Hence, reaction paths that involve charge-separated intermediates or transition states are accelerated--by lowering the activation barrier-in the presence of ILs when compared with those performed in classical organic solvents. It is also possible, for example, to observe, by electrochemical methods, transient species (ionic and radical) that are otherwise undetectible in water or in molecular organic solvents and to investigate the interactions and behaviour of molecular, biological and macromolecular species in solution using physical and chemical methods which require special conditions such as high-vacuum, and which have been traditionally limited to solid state chemistry.

C-H-π Interactions in 1-n-Butyl-3-methylimidazolium Tetraphenylborate Molten Salt: Solid and Solution Structures

The crystal structure of 1-n-butyl-3-methylimidazolium tetraphenylborate molten salt (1) shows C-H-pi interactions between the hydrogens of the imidazolium cation and the phenyl rings of the tetraphenylborate anion. The imidazolium ring is surrounded by three tetraphenylborate anions that are connected with the same cation by C-H-pi (phenyl rings) interactions. The nearest inter-ion interaction is found between the N-CH-N proton of the cation and the B-phenyl centroid (2.349 A) with a nearly T-shaped geometry. The inter-ionic solution structure of 1 has been investigated by the detection of inter-ionic contacts in 1H NOESY NMR spectra between the protons of the cation and the anion. The 1H-NMR spectra of molten salt 1 is almost independent of its concentration in [D6]DMSO solution, the imidazolium proton chemical shifts are in the expected region and there are no observable NOE effects between the protons of the cation with those of the anion, indicating that 1 behaves in [D6]DMSO as a solvent-separated ion pair. In CDCl3 the 1H-NMR spectra of 1 are concentration dependent and all the imidazolium protons are shielded as compared with those observed in [D6]DMSO. Moreover, the 1H NOESY NMR spectra show all the peaks affected by the interaction between the protons of the imidazolium cation and those of the anion, indicating that in CDCl3 1 possesses a contact ion pair structure. The NCHN proton of the cation exhibits the greatest shielding (up to -4.5 ppm). an indication of the existence of C-H-pi interactions, even in solution. The calculated distance of this proton to the phenyl centroid is 2.3 A for a C-H -pi angle of 180 degrees. The apparent volumes for the cation and anion, calculated from the measured 13C-NMR relaxation times, increase from 38 and 140 A3 in [D6]DMSO to 360 and 600 A3 in CDCl3, respectively; this indicates the formation of floating aggregates of the type (1)(n) in CDCl3 via weak hydrogen bonds, with increasing concentration.

Two-phase catalytic hydrogenation of olefins by Ru(II) and Co(II) complexes dissolved in 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

Abstract The interaction of RuCl 2 (PPh 3 ) 3 and 1-n-butyl-3-methylimidazolium tetrafluoroborate molten salt yields an air and water stable solution that is able to hydrogenate olefins with turnover frequencies up to 537 h −1 in a typical two-phase catalytic reaction. The complex K 3 Co(CN) 5 also affords a catalytic system with the ionic liquid that catalyzes the reduction of butadiene into but-1-ene with 100% conversion and selectivity.

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.

TEREPHTHALIC ACID, NEOPENTYL GLYCOL AND TRIMETHYLOLPROPANE POLYESTERIFICATION USING VERSATILE AND HIGHLY EFFICIENT TIN COMPLEXES AS CATALYSTS PRECURSORS

The catalytic performance of the tin complexes bis(acetylacetonato)tin(II) (1), dibutyltin oxide (2), bis(chloroacetato)tin(II) (3), bis(3-hydroxy-2-methyl-4-pyrona)tin(II) (4), dibenzoatotin(II) (5) and dihydroxybutyltin chloride (6) are described for terephthalic acid, neopentyl glycol and trimethylolpropane polyesterification. The synthesized complexes, which are easy to prepare from inexpensive commercial chemicals, showed catalytic behavior comparable to the industrially used (2) and (6). The productivity values varied from 72.2 when (2) was used as a catalyst to 192.0 with (1). The best values for reaction time was obtained for the commercial catalyst (6) (6 h 26 min) and for (1) (7 h 36 min). The infrared analyses allowed us to observe bands relative to ester formation and to confirm the hydroxylation for all polymers samples. 1. INTRODUTION Polyesters have been widely used as polymeric materials. Indeed, terephthalic acid based polyesters have received special attention due to several interesting properties of Polyethylene terephthalate) or PET. This polyester is the most widely used synthetic fiber which is sold under many different trade names. PET is also commonly encountered in plastic bottles for soft drinks and in films which are used for food or liquid packaging, magnetic tapes and novelty balloons, among others applications [1], Polyesters based on isophthalic acid and terephthalic acid have been developed for use in polyester powder coatings [2]. Terephthalic acid has historically been the primary monomer providing polymers with the required glass transition temperature for coating storage stability, while contributing flexibility, weathering and chemical resistance [2]. Different metallic ions have been described that catalyse efficiently esterification and polyesterification reactions. Nondek and Mälek [3] ordered the activities of catalysts for reaction of ethylene glycol with isophthalic acid as Sn> T i 4 + »Zn >Pb,Co,Cd. The development of simple and cheaper catalytic systems for polyesterification reaction as well as new polymer materials using different monomers is important for technological and academic purposes. We have recently shown that the tin complex, bis(3hydroxy-2-methyl-4-pyrona)tin(II) (4), is highly active as polyesterification catalyst [4], In this paper we wish to report highly efficient catalysts systems based upon tin complexes, using differents ligands, for terephthalic acid (TFA), neopentyl glycol (NPG) and trimethylolpropane (TMP) polyesterification. 2. MATERIALS AND METHODS 2.1. General Procedures Routine infrared spectra were recorded on a Bomenn MB-Series Hartmann & Braun spectrophotometer. Molecular weights of the polymers were determined by gel permeation chromatography with a GPC Data Station 4.0. The acid number, i.e, the total concentration of the carboxylic groups in the reaction medium, are measured by diluting about 1.0 g of the sample in 50cm DMF. The sample is heated until fusion without boiling. Then the sample is cooled at room temperature and titrated with 0.1 Ν KOH in methanol with Phenolphthalein as indicator. The acid number [5] is calculated by (AN=V(mL) χ 56.1 χ N)/P[mgKOH/g] were V= volume of titrate liquid; N= Normality of titrate liquid and P= sample mass viscosity. 2.2. Preparation of the catalysts The complexes, (1), (3) , (4) and (5) were prepared according the procedures described in the literature [6,7,4,8], The catalysts (2) and (6) were obtained from commercial sources and used as received without further purification. 2.3. Polymerization Reactions Polymerization was carried out in a 2L reactor system consisting of a four necked round-bottom flask. The flask was equipped with an air-driven stirrer, a thermocouple, nitrogen inlet tube and two adjacent partial reflux condensers one of them charged with a packing, and the other a steam-jacketed partial reflux condenser. A tube test receiver is installed in one of the four necks. The flask is heated by means of an electrical heating mantle. The temperature is monitored via an Pt 100 thermocouple with a temperature

Synthesis and Evaluation of Biocide and Cetane Number Improver Additives for Biodiesel from Chemical Changes in Triacylglycerides

Biodiesel demand is increasing all over the world and the inhibition of microbial growth during the storage of this biofuel is extremely important. There are few studies involving the evaluation of biocides specifically for biodiesel. In the present work, we synthesized and evaluated a set of biocide candidates from chemical transformations in triacylglycerides. Samples of pure biodiesel with the products were evaluated against microorganisms which have been isolated from biodiesel/diesel blends (fungi A. niger, A. fumigatus, C. albicans and S. cerevisiae; and bacteria B. subtilis and Acinetobacter sp.). None of the products inhibited the growth of bacteria. Four nitrated derivatives presented fungicidal activity. The nitrated derivatives were also evaluated as cetane number improvers for B7 biodiesel/diesel blend. The nitrates of soybean methoxylated ethylene glycol esters increased the cetane number by more than three points. Despite showing modest biocide activity, the results can guide the planning of new products from triacylglycerides.

Evaluating the Potential of Biodiesel Production through Microalgae Farming in Photobioreactor and High Rate Ponds from Wastewater Treatment

In the last decade, the research works on microbial as a potential source of lipid for biodiesel production have been growing. In this work, the potential of a sludge from high-rate lagoons in urban sewage treatment, composed mainly by Chlorella sp., as oil source for biodiesel production, was studied. The potential of Chlorella sp. growth in photobioreactor under controlled conditions was also investigated. Low lipid content (up to 3%) was observed in both cases. The composition of both oils showed high amount of fatty acids and fatty acid based compounds, however there are also other non-fatty acid based lipids. Density and viscosity of biodiesel from biosolid oil were determined and the results showed that these physico-chemical properties do not match the specification required for biodiesel. The results showed that sewage sludge from Samambaia treatment station (DF, Brazil) and Chlorella sp. cultivated under the conditions described in this work are not potential sources of fatty material for biodiesel production.

Do Óleo de Amendoim ao Biodiesel- Histórico e Política Brasileira para o Uso Energético de Óleos e Gorduras

A historia do uso de oleos e gorduras como combustiveis liquidos em motores do ciclo Diesel se confunde com a historia do proprio motor. No entanto, foi somente no Seculo XXI que o Brasil e outros paises iniciaram o seu uso comercial em larga escala. Especificamente no Brasil, foi iniciado em 2005 um ousado programa para a substituicao de oleo diesel por biodiesel. Como resultado, em apenas 10 anos foi instalado no pais um parque industrial capaz de produzir cerca de 4 bilhoes de litros de esteres metilicos de acidos graxos anualmente, gerando milhares de empregos. Apesar da biodiversidade brasileira apresentar diversas possiveis fontes de oleos e gorduras, a industria brasileira hoje praticamente utiliza apenas o oleo de soja e gorduras residuais do processamento de animais de corte. O futuro desta industria e bastante promissor, ja havendo metas governamentais para o aumento da substituicao do oleo diesel por este biocombustivel.

Nuclear magnetic resonance (1.40 T) and mid infrared (FTIR-ATR) associated with chemometrics as analytical methods for the analysis of methyl ester yield obtained by esterification reaction.

In this work, we compared 1.40 T nuclear magnetic resonance (NMR) to 7.05 T (60 and 300 MHz for proton, respectively), and mid-infrared with attenuated total reflectance (FTIR-ATR), associated with chemometrics methods, for the quantification of the reaction yield during esterification of fatty acids with methanol. The results showed that the integrated intensities of the ester C=O stretching region, relative to the total C=O stretching region, is useful to quantify the fatty acid methyl ester (FAME) concentration. Comparing the results obtained by the different final models: NMR (1.40 T and 7.05 T), FTIR-ATR using multivariate partial last squares regression (PLS) with orthogonal signal correction (OSC), and univariate ordinary least squares (OLS), the NMR of 1.40 T (60 MHz for proton) showed more advantages when compared to a high field spectrometer, due to the non-use of cryogenic and solvents and less laborious work for obtaining results.