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The aviation industry has set ambitious goals to reduce carbon emissions in coming decades. The strategy involves the use of sustainable biofuels, aiming to achieve benefits from environmental, social, and economic perspectives. In this context, Brazilian conditions are favorable, with a mature agroindustry that regularly produces automotive biofuel largely adopted by Brazilian road vehicles, while air transportation has been growing at an accelerating pace and a modern aircraft industry is in place. This paper presents the main conclusions and recommendations from a broad assessment of the technological, economic, and sustainability challenges and opportunities associated with the development of drop-in aviation biofuels in Brazil. It was written by a research team that prepared the initial reports and conducted eight workshops with the active participation of more than 30 stakeholders encompassing the private sector, government institutions, NGOs, and academia. The main outcome was a set of guidelines for establishing a new biofuels industry, including recommendations for (a) filling the identified research and development knowledge gaps in the production of sustainable feedstock; (b) overcoming the barriers in conversion technology, including scaling-up issues; (c) promoting greater involvement and interaction between private and government stakeholders; and (d) creating a national strategy to promote the development of aviation biofuels.

Sodium titanate was synthesized by the sol–gel method and characterized using X-ray diffraction, thermogravimetry-mass spectrometry, atomic absorption spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis and nitrogen physisorption. The non-calcined material was active as a catalyst in transesterification reactions and showed high stability. An appreciable loss of activity on the fourth reuse was accompanied by the appearance of a new species of oxygen and segregated sodium, identified by X-ray photoelectron spectroscopy (XPS). The XPS spectrum showed that the basic nature of the framework oxygen was inferior to the original basicity, which explained the decline in catalytic activity.

In an editorial of a recent issue of a known academic journal, Prof. Hartmut Michel affirmed that “…the production of biofuels constitutes an extremely inefficient land use… We should not grow plants for biofuel production.”, after comparing the area occupied with plants for bioenergy production with the one required for photovoltaic cells to supply the same amount of energy for transportation. This assertion is not correct for all situations and this comparison deserves a more careful analysis, evaluating the actual and prospective technological scenarios and other relevant aspects, such as capacity requirements, energy consumed during the life cycle of energy systems and the associated impacts. In this communication this comparison is revaluated, presenting a different perspective, more favorable for the bioenergy routes.

In 2013, the International Air Transport Association, in agreement with the International Civil Aviation Organization, approved a resolution setting out ambitious targets for addressing carbon emission reduction entitled ‘Aviation Carbon-Neutral Growth Strategy (CNG2020)’. The strategy involves the use of sustainable biofuels (drop-in), aiming to achieve benefits from environmental, social, and economic perspectives. In this context, Brazilian conditions are favourable, with a mature agroindustry that regularly produces large amounts of grains and cereals, and automotive biofuel largely adopted by all Brazilian road vehicles. At the same time, air transportation has been growing at an accelerating pace and a modern aircraft industry is in place. In order to identify the main opportunities, and the main gaps and barriers to developing a modern and sustainable aviation industry in Brazil, a roadmapping methodology was implemented involving stakeholders and players in the biofuels and aeronautics industries. The process was carried out using a workshop setting to stimulate discussions on the following topics: Feedstock, Refining Technologies, Sustainability, Policy and Incentives, Logistics & Support, Research & Development, and Commercialization Gaps. The effort involved an active participation of more than 30 stakeholders encompassing the private sector, government institutions, non-governmental organizations, and academia, and a full report was published (Roadmap for Sustainable Aviation Biofuels for Brazil: A Flightpath to Aviation Biofuels in Brazil). Aiming to present the main outcomes, in the following topics relevant aspects concerning feedstocks, land availability, sustainability, and refining processes are discussed. The conclusion gives a summary of limiting factors and policy recommendations.

Mixed xCeO2–Al2O3 oxides with different CeO2 content (x = 1–20 wt%) were prepared by sol–gel method. The effect of the CeO2 content, atmosphere and temperature treatment during synthesis on the structure and properties of the xCeO2–Al2O3 was investigated. xCeO2–Al2O3 xerogels prepared from aluminum tri-sec-butoxide and Ce(III) nitrates have a pseudo boehmite-like structure. The Ce(III) ions stabilized under a reductive atmosphere randomly occupy vacant sites in tetrahedral and octahedral positions of Al2O3. The crystallization of γ-Al2O3 is suppressed and the textural properties of the mixed xCeO2–Al2O3 oxides are stabilized at high temperature. Conversely, the treatment xCeO2–Al2O3 xerogels in an oxidative atmosphere shows a progressive oxidation of Ce(III) to Ce(IV) with crystallization of γ-Al2O3 and formation of CeO2 with fluorite-like structure as the temperature rises. The effect of CeO2 on the catalytic performance xCeO2–Al2O3-supported Pt catalysts in partial oxidation of methane reaction was tested. The Pt catalysts were obtained by two methods: (i) impregnation of the xCeO2–Al2O3 supports with H2PtCl6·6H2O and (ii) one-step preparation by addition of Pt precursor during the sol–gel synthesis. CeO2-containing catalysts showed higher stability than Pt/Al2O3 catalyst obtained by impregnation method. The effect of the support was less evident when the catalysts were obtained by the one-step method. Pt catalysts based on sol–gel oxides preparation show higher thermal stability and result in higher Pt sintering resistance than conventional ones.

Simple aluminum salts activate hydrogen peroxide towards α,β-unsaturated ketones, affording as major products α,β-epoxyketones. The pathway of this reaction involves the interaction between [Al(H 2 O) 6 ] 3+ and H 2 O 2 , through hydrogen bonds, in the second-coordination sphere. This interaction enhances the proton exchange between non-coordinated water and hydrogen peroxide, as detected by 1 H NMR experiments. By this means, the hydroperoxide anion, formed as reactive intermediate in the proton exchange between H 2 O and H 2 O 2 , can be trapped by α,β-unsaturated ketones. Surprisingly, this pathway is not followed when diethylmaleate is used as substrate. In this case, the radical addition of THF to the C C bond of diethylmaleate takes place with high selectivity, affording 2-(THF)-derivatives with high yields.

The effect of La2O3 content on the structural properties and catalytic behavior of Pt/xLa2O3–Al2O3 catalysts in steam reforming of methane and partial oxidation of methane was investigated. There was a decrease in the density of Pt sites with the increase of La2O3 loadings according to Fourier transform infrared spectroscopy of adsorbed CO and to dehydrogenation of cyclohexane results. However, transmission electron microscopy data indicates an opposite trend. This apparent disagreement could be due to the partial coverage of Pt sites by LaOx species. CH4 turnover rates and specific rates of steam reforming of methane increased for higher La2O3 loadings. The Pt/Al2O3 catalyst was strongly deactivated during partial oxidation of methane, while La2O3-containing catalysts exhibited higher stability. The increase of activity observed during the reactions was ascribed to the ability of the [LaPtxO]Pt0-like species to promote the gasification of coke. This cleaning mechanism led to higher accessibility of the active sites to CH4.

Liquid phase cyclohexanol catalytic oxidation to cyclohexanone and epsilon(ε)-caprolactone were studied using aqueous hydrogen peroxide as oxidant and H3PW12O40 (HPA) and H0.5Cs2.5PW12O40 (Cs-salt) as catalysts. The hydrophobic and insoluble Cs-salt showed the highest activity (per unit catalytic weight and turnover number) and selectivity to (ε)-caprolactone. The ultrafine Cs-salt crystallites could be filtrated and recycled. Solvent effects on the activity and selectivity and the rate of peroxide decomposition were assessed and they were correlated to their polarity and protic/aprotic nature. When employing acetonitrile at 90 °C the highest activity and selectivity were achieved and also the lowest rate of hydrogen peroxide decomposition. Fil: Balbinot, L.. Universidade Estadual de Campinas; Brasil Fil: Schuchardt, U.. Universidade Estadual de Campinas; Brasil Fil: Vera, Carlos Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Sepúlveda, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina

Alumina catalyzes the Baeyer–Villiger oxidation of cyclohexanone, using 70 wt.% aqueous or anhydrous hydrogen peroxide as oxidant. The best methodology was to carry out the reaction in ethyl acetate under azeotropic water removal at 90 °C, and a molar ratio cyclohexanone:oxidant of 1:4. Under these conditions, the conversion was 53% with a selectivity of 98% for ɛ-caprolactone. The weak and strong acid sites of alumina were correlated with the substrate conversion and hydrogen peroxide consumption for the Baeyer–Villiger oxidation. It is shown that the weak acid sites, which activate hydrogen peroxide for the catalytic epoxidation of nucleophilic olefins, are also responsible for the Baeyer–Villiger oxidation. Stronger acid sites, however, also participate in the Baeyer–Villiger oxidation, by activation of the carbonyl group. The interaction of the carbonyl group with strong acid sites also reduces the hydrogen peroxide decomposition.

[Nb]-MCM-41 was synthesized at room temperature by varying the base (tetramethylammonium hydroxide or ammonium hydroxide), the silica source (tetraethyl orthosilicate or tetramethyl orthosilicate), the niobium source (ammonium niobium oxalate, NH 4 [NbO(C 2 O 4 ) 2 (H 2 O) 2 ] · 3H 2 O, or potassium niobate, K 8 Nb 6 O 19 ) and the order of addition of the niobium source (before or after the silica source). These variations were determinant in the amount of niobium incorporated into the framework and in the structural order of the [Nb]-MCM-41 obtained. Only one method led to the formation of [Nb]-MCM-41 with the desired characteristics and active in the epoxidation of cis -cyclooctene with tert -butyl hydroperoxide leading to 19% conversion and 95% selectivity for cyclooctene oxide after 10 h.

In this work, the base-catalyzed transesterification of soybean oil with ethanol was monitored on-line using mid-infrared spectroscopy (MIRS) and the yield of fatty acid ethyl esters (biodiesel) was obtained by (1)H NMR spectroscopy. The MIRS monitoring carried out for 12min, was performed using a cylindrical internal reflectance cell of PbSe in the range of 3707-814cm(-1) with eight co-added scans. Two different data treatment strategies were used: in the first, the models were built using the raw data and in the other, evolving factor analysis (EFA) was used to overcome the sensor time delay due to the on-line analysis, producing significantly better results. In addition, models based on partial least squares (PLS) using three batches for calibration and another for validation were compared with models with just one batch for calibration and three for validation. The models were compared between each other using root mean square error of prediction (RMSEP) and root mean square prediction difference (RMSPD), obtaining relative errors under 3%.

Direct infusion electrospray ionization mass spectrometry (ESI-MS) of aqueous/methanolic extracts of biodiesel samples is shown to permit simple and fast fingerprinting typification, identification of the alcohol used in the trans-esterification process, monitoring of degradation and adulteration, and screening of residual glycerin and mono-, di-, and tri-glycerides. As proof-of-principle cases, ESI-MS fingerprints in both the positive and the negative ion modes were acquired for biodiesel samples derived from soybean oil, sunflower oil, canola oil, olive oil, castor oil, jatropha curcas oil, palm oil, lard, and tallow. In the negative ion mode, characteristic sets of ions corresponding to de-protonated fatty acids were detected for each type of biodiesel, thus allowing their reliable typification via these taxonomic markers. Biodiesel degradation was also monitored by ESI(−)-MS with the detection of degradation markers, mainly oxidized fatty acids. When using ESI(+)-MS, the main diagnostic ions detected ...

The contextualized understanding of concepts in Chemistry by students from other areas is a challenging task. In this experiment, the synthesis of biodiesel is done by base catalyzed transesterification of refined soy oil with methanol at room temperature and common glassware found in any chemistry laboratory. The proposal permits introducing several concepts, such as that of emulsion, viscosity and catalysis to illustrate an activity based on an actual problem. In this didactic approach, some common problems of biodiesel production, such as soap formation and phase separation, are introduced into the procedure in order to raise questions and motivate the students to participate in the experimental work and stimulate reflections about critical aspects of biodiesel production. This experiment was carried out in the first semester of 2006, in experimental general chemistry taken by physics and agricultural, civil and chemical engineering students of UNICAMP.

Polyester reinforced PTFE membranes with a nominal pore size of 0.02 μm are very effective in pervaporating HCl gas from hydrochloric acid solutions and cellulose hydrolysates. The efficiency of such membranes, which may be as high as 1.8x10−2 mmol HCl min−1 cm−2 at 40°C, is almost independent of the flow rate and the static pressure of the acidic solution but depends strongly on the acid concentration. At an acid concentration of 26% (w/v) the pervaporation of HCl is negligible at 40°C, but can be accelerated by increasing the temperature. A slow increase of temperature during the pervaporation process is proposed, as this promotes post-hydrolysis of the sugars. Lithium chloride induces structural changes in the membrane which increase efficiency without compromising performance. The use of this new technology in conjunction with the original Bergius process could improve the performance of the latter and reduce its overall costs. The use of the improved process for the hydrolysis of sugar cane bagasse could double the yields of sugar or alcohol per hectare of planted sugar cane.

Lithium chloride, in combination with commercial grade hydrochloric acid, is very effective in the hydrolysis of prehydrolysed sugar cane bagasse. After 10 min at 50°C the holocellulosic portion is completely dissolved and after 20 min most of the sugar oligomers are hydrolysed to monomers, making the time-and energy-consuming post-hydrolysis unnecessary. With longer reaction times the sugars start to reoligomerise and decompose. Zinc chloride is a milder promoter, requiring post-hydrolysis even after reaction for 30 min at 50°C. On the other hand, it does not decompose the sugars giving the highest sugar yields after prolonged reaction time and post-hydrolysis. Ferric chloride is mostly ineffective in the hydrolysis of cellulose but is a good promoter of the hydrolysis of the sugar oligomers, under the reaction conditions.

Ultrasound effectively promotes the hydrolysis of pre-hydrolysed sugar cane bagasse using 38% concentrated hydrochloric acid. In combination with lithium chloride, ultrasonic promotions as high as 62% were observed. Of the three frequencies (25, 35 and 40 kHz) studied, the lowest promoted the hydrolysis most effectively but, when in combination with lithium chloride, reoligomerised the sugars. The higher frequencies of 35 and 40 kHz required larger concentrations of lithium chloride for complete conversion. Irradiation with 40 kHz also promoted subsequent acid hydrolysis of the sugar oligomers.

Reduced anatase TiO 2 is used as an alternative support for TiCl 4 , leading to good results in the polymerization of ethylene and propylene with isotacticity above 80%. However, due to the low concentration of active sites, approximately 1 wt% of active titanium, the system leads to low productivity. With the objective of increasing the amount of active sites and the productivity, a catalytic system with a high surface area was developed. The synthesis consists in the chemical vapor deposition, known as Atomic Layer Epitaxy (ALE), of TiCl 4 onto a silica surface. The deposited titanium is then transformed into anatase by heating between 300 and 500 °C. The synthesis of the catalyst is carried out by chemical reduction of the oxide with n -butyl lithium and heterogenization of TiCl 4 . The amount of supported TiO 2 was, on average, 13 mg TiO 2 (g SiO 2 ) −1 . The content of active titanium was 23 μmol Ti(III) (g cat) −1 . Two resonance peaks for Ti(III) ( g = 1.98 and g = 1.96) in the EPR spectrum suggest the presence of two different active species on the catalyst surface. The catalyst was tested in the polymerization of ethylene in the liquid and in the gas phase, leading to productivities of 140 and 120 g PE (g cat) −1 , respectively. The polymers presented a melting point of 137 °C, molar masses around 3000 kg mol −1 and crystallinities between 49 and 69%.

A bis(diketiminate)bromosamarium(III) complex was successfully synthesized and, after the activation with butyl lithium, was shown to be active in methyl methacrylate (MMA) polymerization. The effects of temperature, polymerization time and catalyst concentration were studied. Activities of ca. 16,000 g of poly(methyl methacrylate) (PMMA) per mol of samarium and per hour were obtained under optimum conditions (0 °C and a MMA/catalyst molar ratio of 90/1), providing a polymer with a molar mass Mn > 23.0 kg mol−1 and a molar mass distribution (Mw/Mn)

Two commercial aluminas and one produced by the sol–gel process were compared for the epoxidation of unsaturated fatty esters using anhydrous or aqueous hydrogen peroxide as oxidant and ethyl acetate as solvent. The aluminas show a good catalytic activity and excellent selectivity towards the epoxides. The sol–gel alumina was more efficient and when using aqueous hydrogen peroxide could be recycled several times.

This report addresses several questions regarding the deactivation of alumina in catalytic epoxidation using aqueous 70% H 2 O 2 . The structural, textural, morphological, and chemical changes of a polycrystalline alumina ( γ -Al 2 O 3 and boehmite) were studied in five consecutives reactions of 24 h. The chemical and physical processes involved in the transformations during alumina recycling are attributed mainly to the presence of water in the reaction mixture. Water plays a dual role in the catalytic system. On the one hand, water may cause deleterious changes of the structure of γ -Al 2 O 3 and its textural properties. On the other hand, the presence of water shifts the adsorption equilibria of the organic molecules (acetic acid, diols, and oligomers), preserving the type Ia Al OH sites, which are active for catalytic epoxidation. In this way, the water in the alumina/H 2 O 2 catalytic system seems to be significant in prolonging the lifetime of the catalyst.

This study answers several pending questions about alumina-catalyzed epoxidation with aqueous 70 wt% H 2 O 2 . To evaluate the effect of the water-to-aluminum tri- sec -butoxide molar ratio, this was systematically changed from 1 to 24. The xerogels were calcined at 450 °C and gave different γ -Al 2 O 3 's with distinct textural and acidic properties. A combination of 27 Al MAS NMR and TPD-NH 3 results of calcined aluminas allowed us to assign the type Ia Al OH sites as the catalytic sites for epoxidation. The type Ib Al OH sites have no function in catalytic epoxidation, because ethyl acetate poisons these sites. The strong acid sites of types IIa, IIb, and III Al OH groups are responsible for the undesired H 2 O 2 decomposition and decreased oxidant selectivity.

The changes in the structural, morphological and acidity properties of nanocrystalline aluminas provoked by hydration under a controlled humidity atmosphere at room temperature were studied. Besides the physical and chemical adsorption of water on the surface, the hydration process causes the formation of aluminum oxy-hydroxide and trihydroxide (boehmite and bayerite). The recalcination of hydrated γ-Al2O3 cannot recuperate the initial acidic properties of the material. The populations of weak to moderate acid sites strongly decrease under recalcination of hydrated aluminas. On the other hand, the stronger acid site populations are not strongly affected by recalcination.

Well-ordered [Nb]-MCM-41 was synthesized at room temperature with essentially all niobium present in the sample substituted into the silica framework. The material was calcined and then silylated using hexamethyldisilazane (HMDS). Both calcined and silylated materials were characterized by X-ray diffraction (XRD), diffuse reflectance UV–vis, inductively coupled plasma emission (ICP-OES), infrared spectroscopy (FTIR), N2 adsorption at low temperatures, thermogravimetry (TG), and nuclear magnetic resonance of 29 Si with magic-angle spinning (NMRMAS). The materials were used as catalysts in the epoxidation of cis-cyclooctene with tert-butyl hydroperoxide (TBHP) and 70 wt% aqueous hydrogen peroxide as oxidants, to verify the influence of the silylation on the activity and selectivity. It was observed that the silylated material was more active for both oxidants, reaching 62% conversion and 94% selectivity after 48 h with TBHP and 13% conversion and 80% selectivity after 5 h with aqueous hydrogen peroxide. © 2006 Elsevier Inc. All rights reserved.

Montmorillonite K10 was ion-exchanged with polyhydroxyniobium obtained from niobium pentachloride by hydrolysis. This modified clay was characterized by X-ray diffraction, thermogravimetric analysis, inductively coupled plasma emission (ICP-OES) and nitrogen adsorption/desorption. The obtained material was used in the alcoholysis of epoxidized methyl oleate with methanol, leading to β-hydroxyethers. The reaction with ion-exchanged montmorillonite (Nb-Mont) was four times faster at 60 °C and three times faster under reflux than the one using the original clay. This proves the increase of Bronsted acidity when polyhydroxyniobium is present. The Nb-Mont was also calcined at 300, 500 and 900 °C to obtain the Nb-pillared montmorillonite. However, the activity of the calcined Nb-Mont decreased with increasing calcination temperature. On the other hand, calcined montmorillonite maintained its basal distance, even after treatment at 900 °C.

Half-sandwich samarium(III) diketiminate bromide was successfully synthesized and was shown to be active in methyl methacrylate (MMA) polymerization. The effects of temperature, polymerization time and catalyst concentration were studied. Activities of ca. 18 kg of polymethacrylate (PMMA) per mol of samarium per hour were obtained under optimum conditions (0 °C and a MMA/catalyst molar ratio of 100/1), giving a polymer with a molar mass Mn>24,000 g mol−1 and a molar mass distribution (Mw/Mn)

The selectivity of the alumina catalyzed epoxidation of (S)-limonene, citronelal, citral, citronelol and (1S)-(α)-pinene with aqueous 70 wt% and anhydrous 24 wt% hydrogen peroxide is described. DFT molecular orbital calculations were used aiming at a better understanding of the reactivity of these terpenes. The more nucleophilic carbon–carbon double bond, which has a higher molecular orbital energy, is preferentially epoxidized (site-selectivity). Furthermore, a preference for epoxidation in competition with other possible reactions is observed for citronelal, citral, citronelol and (1S)-(α)-pinene (chemo-selectivity). Nonetheless, we were not able to achieve a stereo-selective epoxidation of the terpenes using alumina and hydrogen peroxide.

The aluminas obtained by calcination of nanocrystalline boehmite, prepared by the sol–gel method, in the range 200–1000 °C were characterized by powder X-ray diffraction, thermogravimetric analysis, Fourier transformed infrared spectroscopy, nitrogen adsorption–desorption, and scanning electron microscopy. The catalytic activity of these aluminas in the epoxidation of cis -cyclooctene with aqueous 70 wt% hydrogen peroxide shows, after 24 h, a profile with two maxima at 400 and 700 °C that corresponds to 85 and 80% yield, respectively. However, this profile cannot be directly related to the structural and textural properties of the calcined aluminas. Regarding the hydrophilicities of the calcined aluminas, determined by the amount of water molecules per nm 2 , the epoxide yield of the aluminas can be segregated into three groups corresponding to the general crystallographic classification of these aluminas: boehmite, γ -series, and δ -series. The aluminas from the γ -series show the highest cyclooctene oxide yield after 1 h; however, due to surface modifications occurring during the reaction, the aluminas from the δ -series also give good yields after 24 h. The water adsorption capacity or hydrophilicity of these aluminas shows a strong correlation with epoxide productivity of the calcined aluminas at 24 h. Generally, better epoxide productivity is observed for lower hydrophilicities. The hydrogen peroxide efficiencies are typically 2.0–2.5 mmol of oxidant per mmol of epoxide formed after 24 h. However, the aluminas of the δ -series show poor efficiency at the beginning of the reaction that improves from an average of 4.1 to 2.3 mmol of oxidant per mmol of epoxide after 2 h due to modification of their surfaces.

Dinuclear manganese(IV) complex [LMn(O)3MnL](PF6)2 (1, L = 1,4,7-trimethyl-1,4,7-triazacyclononane) efficiently catalyzes epoxidation of sterically accessible olefins, including natural compounds by hydrogen peroxide in acetonitrile at room temperature if a small amount of a carboxylic acid is present in the solution. The kinetics of dec-1-ene epoxidation and accompanying dioxygen evolution (catalase activity) under the action of this system in the presence of acetic acid has been studied. The initial rates of both epoxidation and O 2 evolution are proportional to the catalyst initial concentration. First order has been found for catalyst 1 for both processes, whereas the rate dependences of the dec-1-ene epoxidation is first order and the O 2 evolution is second order for H2O2. The epoxidation rate increases and the O2 evolution rate decreases with growing of acetic acid concentration. Zero order has been found for dec-1-ene in its epoxidation. The reaction proceeds with an induction period for a few minutes during which changes in the electronic spectra of the reaction solution are observed. It has been proposed that the processes of the alkane oxidation and dioxygen evolution on the one hand and of the olefin epoxidation on the other hand are induced by different intermediate species. An assumption has been made that the epoxidation occurs with participation of oxo-hydroxy Mn(V) derivative [LMn V ( O)(O)2(HO)Mn IV L] 2+ , whereas di(hydroperoxy) complex [LMn III (OOH)(O)2(HOO)Mn IV L] + is responsible for the alkane oxidation with simultaneous dioxygen evolution. The following equations for the initial rates were proposed for [CH 3CO2H] = 0.25 mol dm −3 : d[epoxide]/dt = keff (epoxide)[1][H2O2] with keff (epoxide) = 2.8–3.7 mol −1 dm 3 s −1 ; d[CyOOH]/dt = keff (CyOOH)[1][H2O2] 2 [CyH] with keff (CyOOH) = 4.1–6.2 mol −3 dm 9 s −1 ; d[O2]/dt = keff (O2)[1][H2O2] 2 with keff (O2) = 2.8–7.0 mol −2 dm 6 s −1 . Many different carboxylic acids were checked as cocatalysts and it has been found that oxalic acid acts with the highest efficiency in the epoxidation whereas the accompanying catalase activity of the system is very low in this case. It has been also demonstrated that complex 1 is unique catalyst because similar compounds containing only one Mn(IV) center (2) or dinuclear complex with bridging phenylboronic acid (3) are very poor catalysts in the olefin epoxidation. No epoxidation has been found when hydrogen peroxide was replaced by tert-butyl hydroperoxide. The system based on 1 ,H 2O2 and acetic and/or oxalic acid was employed for the efficient epoxidation of terpenes limonene, citral, carvone and linalool, while other terpenes containing sterically hindered double bonds (citronellal, - and -isomers of pinene) were epoxidized only with

The Wacker oxidation of cyclohexene to cyclohexanone, using the chloride ion-free catalytic system Pd(NO3)2/CuSO4/H3PMo12O40, was investigated at different air pressures, temperatures, and catalyst concentrations. The results show that this system is very efficient and highly selective. After 1 h of reaction at 80 °C and an air pressure of 50 bar, a conversion of 80%, with a turnover frequency of 260 h−1, and a selectivity of more than 99% for cyclohexanone was obtained. Using aqueous hydrogen peroxide and no external pressure, the oxidation was more rapid, giving 80% conversion already after 30 min and 95% conversion after 60 min without the formation of any byproducts.

The structural, textural, and chemical properties as well as the hydrophilicity of four different sol–gel aluminas were determined by different methods and compared with their activity in the catalytic epoxidation of cis-cyclooctene with aqueous H2O2. It was found that the hydrophilicity of the γ-alumina surface is the principal factor responsible for the difference in catalytic activity. The hydrophilicity of γ-alumina should be sufficient to guarantee a fast reaction with hydrogen peroxide on the surface but should not to be too high in order to allow the approach of olefin to the active sites.

An efficient and simple method for preparing titanium or niobium containing MCM-41 has been developed. The mesoporous materials were synthesized at room temperature using tetraethoxysilane (TEOS), cetyltrimethylammonium bromide (CTMABr) as template and (NH 4 ) 2 TiF 6 or NH 4 [NbO(C 2 O 4 ) 2 (H 2 O) 2 ]·(H 2 O) 3 as metal source. The materials were characterized by X-ray diffraction (XRD), FT-IR and diffuse reflectance UV-Vis spectroscopies, which showed that most of the metal was incorporated into the framework of MCM-41. Ti and Nb containing MCM-41 were tested in the solvent-free epoxidation of cis -cyclooctene using tert -butyl hydroperoxide as oxidant and a catalyst:cyclooctene molar ratio of 1:1000. After 24 h of reaction using Ti-MCM-41 and Nb-MCM-41 as catalyst, we obtained 82 and 65% yields of cyclooctene oxide, respectively, without formation of any by-products.

A significant effort has been done towards the development of new catalysts for the synthesis of epoxides in a more environmental friendly way. We have found that a simple hexaaquoaluminum salt (2 mol% of Al(NO 3 ) 3 · 9H 2 O) is able to catalyze the epoxidation of cis -cyclooctene with high yields using aqueous (70 wt%) hydrogen peroxide. In THF we obtained 98% of conversion with 88% of selectivity for cyclooctene epoxide after 12 h.

The iron-based catalyst 2,6-bis[1-(4-bromo-2,6-dimethylphenylimino)ethyl]-pyridineiron(II) chloride, 1 , has been successfully synthesized and characterized. Its catalytic activity was evaluated for the polymerization of ethylene at different temperatures and Al/Fe ratios and compared with that of 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridineiron(II) chloride, 2 . The results show that the catalytic activity of catalyst 1 is highly dependent on the amount of MAO used in the polymerization of ethylene and presents a maximum value at about 20 °C.

It is shown that sol-gel alumina calcined at 400 0C is a very efficient catalyst for the epoxidation of cyclohexene and cyclooctene with aqueous 70 wt % hydrogen peroxide. The overall yield per g of catalyst was 0.28 mol of cyclohexene oxide in 5 cycles of 450 min each and 0.43 mol of cyclooctene oxide in 4 cycles of 750 min each. The selectivity for the epoxides was always better than 99%. However, the catalyst deactives slowly, which we believe is caused by a non-radical decomposition of hydrogen peroxide.

Alumina and 1:1 mixed oxides of Al2O3–ZrO2, Al2O3–TiO2, SiO2–TiO2 and ZrO2–TiO2 were synthesized via a sol–gel process by the so-called neutral amine route, followed by calcination at 600 °C. The mixed oxides were characterized before calcination by X-ray diffraction, revealing ordered hexagonal (Al2O3, Al2O3–ZrO2, ZrO2–TiO2) and lamellar (SiO2–TiO2, Al2O3–TiO2) structures. After calcination, all samples exhibited amorphous structures. Surface areas and pore characteristics of all materials were determined by nitrogen adsorption isotherms. The calcined oxides are active catalysts in the epoxidation of cyclooctene with tert-butyl hydroperoxide as oxidant. Epoxide yields from 14 to 45% were found for reaction times of 24 h. The titanium oxide containing catalysts are the most active and selective ones. On the other hand, the poisoning of acidic centers yields a decreasing activity while increasing selectivity.

The kinetics of the epoxidation of cis-cyclooctene, 2-norbornene and limonene catalyzed by cis-[RuCl2(dppb)(2,2′-bipy)] (1) or trans-[RuCl2(dppb)(2,2′-bipy)] (2) (where, dppb: 1,4-bis(diphenylphosphino)butane; 2,2′-bipy: 2,2′-bipyridine) in the presence of iodosylbenzene (PhIO) follow a Michaelis–Menten type mechanism. The performance of 1 and 2 in the epoxidation of cis-cyclooctene, 2-norbornene and limonene are respectively (1) Vmax=8.62, 11.6 and 4.98 mol l−1 min−1 and (2) Vmax=4.28, 7.55 and 5.66 mol l−1 min−1. The activation energies of the epoxidations catalyzed by 1 are 1.5–3.3 kcal mol−1 lower than those measured for 2.

This account describes our efforts to heterogenize epoxidation catalysts. Anchored and sol-gel entrapped molybdenum were shown to be very selective, but had a strongly reduced activity. On the other hand, molybdenum silicates were very active and stable as long as no diols were present in the reaction mixture. Heterogenized rhenium catalysts were less active but allowed the use of anhydrous hydrogen peroxide as oxidant. However, the high cost and difficult regeneration prevents the industrial use of these catalysts. During these investigations, we found that alumina alone is active in the epoxidation with anhydrous hydrogen peroxide, giving good conversions to epoxides with high selectivity. More research is needed in order to clarify the nature of the hydroxyl groups responsible for its catalytic activity and thus to produce an appropriate material which would allow the obtention of epoxides with high selectivity under industrial conditions. Este trabalho descreve nosso esforço em heterogeneizar catalisadores para epoxidação. Tanto o molibdênio ancorado quanto o engaiolado pelo método de sol-gel mostraram grande seletividade, mas possuem suas atividades fortemente reduzidas. Por outro lado, silicatos de molibdênio foram muito ativos e estáveis até a formação de diols na mistura reacional. Catalisadores heterogeneizados de rênio foram menos ativos, mas permitiram o uso do peróxido de hidrogênio anidro como oxidante. Contudo, o alto custo e a dificuldade de regeneração impedem a aplicação industrial destes catalisadores. Durante estas investigações, descobrimos que a alumina sozinha é ativa para epoxidação com peróxido de hidrogênio anidro, fornecendo boas conversões para epóxidos com alta seletividade. Mais pesquisa é necessária para esclarecer a natureza dos grupos hidroxilas responsáveis pela atividade catalítica, para produzir materiais que permitem a obtenção de epóxidos com alta seletividade em condições industriais.

Organoterbium compounds TbBr2CpHPz and TbBr2CpPPh3 were obtained by reaction of pyrazole or triphenylphosphine ligands with cyclopentadienylterbium dibromide. These compounds were characterized by elemental analysis, complexometric titration with EDTA, thermal analysis, vibrational spectra in the infrared region and 1H NMR. In a preliminary catalytic study, these compounds were active in ethylene polymerization when MAO was used as cocatalyst, producing low crystalline polyethylene.

Cobalt acetylacetonate encapsulated in sol–gel silica is shown to be a very efficient bifunctional acidic and redox catalyst, giving 2,5-furandicarboxylic acid with 99% selectivity directly from fructose at a conversion of 72%. A cooperative effect of the functions of the catalyst is operative, as the same reaction performed in two consecutive steps gives much lower conversions.

In this work the synthesis of mono(cyclopentadienyl)lanthanide compounds containing methanesulfonate anion and pyrazinamide ligand is presented. The compounds were characterized by elemental analyses, complexometric titration with EDTA, thermal analyses, and vibrational spectra in the infrared region. In a preliminary catalytic study these compounds were active in ethylene polymerization when MAO was used as cocatalyst producing low crystalline polyethylene.

In this work we report the synthesis of some organolanthanide compounds which were identified as LnCl2Cp(PzA)2, Ln = Nd, Sm, Eu and Tb, Cp = cyclopentadienyl and PzA = pirazinamide, by elemental analyses, complexometric titration with EDTA, thermal analyses and IR spectra. Thermal analysis and infrared spectra indicated that the coordination of the pyrazinamide to the lanthanide ions was made by the O atom of the carbonyl group and by one or both N atoms of the pyrazinamide ring. This class of compound showed catalytic activity of ca. 4.0 to 6.4 kgPE molLn-1 h-1 bar-1, in ethylene polymerization, using methylaluminoxane as cocatalyst. The resulting polyethylene presented low crystallinity (20%).

Commercial alumina looses some activity after the first epoxidation reaction of (S)-limonene with hydrogen peroxide, but maintains a good activity and a very high selectivity in the subsequent three reactions. After this its activity is strongly reduced, probably due to structural modifications. Aluminas obtained by sol-gel methods are normally less active than the commercial alumina. However, the use of monomeric aluminum sec-butoxide and of oxalic acid to form stable alumina mesophases allows a very active alumina to be obtained, which catalyses the epoxidation of the less reactive cyclohexene with hydrogen peroxide in 98% yield. Close to 50% of the active oxygen is used up in the formation of molecular oxygen.