Supported Au-Pd nanoparticles (NPs) have been extensively studied in alcohol oxidation reactions. However, few studies use reducible metal oxides as support, which can activate oxygen molecules and boost the selectivity of the reaction. In this work, Au-Pd NPs were supported on α-MoO3 and evaluated in the selective oxidation of cinnamyl alcohol without solvent. The Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoemission spectroscopy (XPS) analyses showed that the catalyst is richer in oxygen vacancies than the support, being probably responsible for the stability of the NPs (average size 4.62 ± 0.15 nm) and the high conversion and selectivity for the oxidation of cinnamyl alcohol. Furthermore, experiments have shown that the Au:Pd molar ratio influences the catalytic performance and can be optimized by controlling temperature, pressure, and reaction time. The catalyst proved to be active and selective for cinnamaldehyde in short reaction times. It showed satisfactory performance at 30 min and its best activity at 1 h with 94% conversion and 87% selectivity, without loss of activity and selectivity after four runs under the same reaction conditions.

A catalyst comprised of SnO2 impregnated on ZnO nanowires, which presented remarkable ability to catalyze fatty acid esterification/transesterification reactions, is reported. For optimization of reaction conditions, artificially acidified soybean oil with 10 wt.% oleic acid was used as a model feed. The optimized conditions were: 150 °C, 6 h, 5 g of oil, catalyst concentration of 5%, and methanol:oil molar ratio of 15:1. The catalyst achieved 92% of total fatty acid methyl esters (FAME) content and was used five times without the necessity of catalyst washing from one reaction to the other. Then, such conditions were applied to produce biodiesel from the oil extracted from Scenedesmus sp. microalgae; the system reached 72% of FAME content, without any previous refining or degumming process of the oil. Rietveld refinement, X-ray diffraction, elemental mapping in scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and pyridine-desorption Fourier-transform infrared spectroscopy were used to characterize the material.

AuPd nanoparticles have gained substantial attention due to their application in selective oxidation of alcohols. However, due to the radical nature of the oxidation of benzyl alcohol, under specific conditions, even without a catalyst, the reaction occurs and affects the selectivity of the system. Therefore, we aimed to develop a catalyst that enables the control of the oxidation leading to higher reaction selectivity. To accomplish this, we have prepared a catalytic support comprised of CoFe2O4 nanoparticles impregnated with Sr(OH)2 that presented a significant control of the reaction selectivity without any metal or external base addition. After the impregnation of AuPd nanoparticles in a specific ratio, the reaction reached a selectivity of > 99% for benzaldehyde, in 3.5 h, with a recycle regime of five runs without loss of activity and selectivity. Our results show that the judicious choice of the ratio of the metals prevents the necessity of manipulating the reaction conditions to improve the performance of the system. Additionally, studies under N2 and O2 environments, with or without water, confirmed the role of the O2 in the system. Holding all this information, we propose a possible mechanism for the prepared system.

We have prepared, by a sol-immobilization method, bimetallic catalysts with different Au:Pt atomic ratios supported on commercial SrCO3. The catalytic performance for the oxidation reaction of benzyl alcohol of such materials was compared to the monometallic counterparts, aiming at the obtaining of the best composition of the material. It was found that the Au:Pt atomic ratio presents a remarkable effect on the system performance, i.e., Pt-rich systems are more selective; however, less active. Thus, an equilibrium related to the activity and selectivity of the system was obtained by considering the yield of the system. Also, some density functional theory (DFT) insights were obtained by using a cluster of 14 atoms of Au and 1 or 2 atoms of Pt. X-ray photoelectron spectroscopy, elemental mapping in scanning transmission electron microscopy before and after catalyst usage, flame atomic absorption spectroscopy, Rietveld refinement, among other techniques, were used and associated to the experimental data, which allowed us to propose a catalytic mechanism for the system, which was important since SrCO3 has not been considered before as catalyst support for alcohol oxidation reactions.

The synthesis of efficient and reusable gold-based catalysts for the selective oxidation of alcohols is a strategy for the development of green processes. Pre-formed nanoparticles syntheses are an easy way to produce controlled-nanosized gold materials; however, the selection of a support is not trivial. Herein, we proposed a CoFe2O4 support enriched with Sr(OH)2, which holds remarkable properties and is suitable for the synthesis of a stable gold-based catalyst for the oxidation of benzyl alcohol. We suggested that the interaction between the CoFe2O4 and the Sr(OH)2 is highly important for the performance of the catalyst. Under the base-free condition of 2.5 h, 100 ºC and 2 bar of O2, the catalyst reached 58% of conversion with 76% of selectivity to benzaldehyde. With K2CO3 addition, the conversion and selectivity to benzaldehyde increased to 87% and 88%, respectively. Any gold leaching was detected in 5 successive runs, attesting the noticeable stability that the catalyst presents. This work provides great potential for the selective oxidation of alcohols with high activity since the magnetic properties of the catalyst provide an easy route and allows the separation of the medium reaction. In addition, we are here proposing an important interaction between the Sr(OH)2 and the magnetic nanoparticles.

Microalgae lipid-derived biofuels is considered promising candidates for substitution of petroleum-based energy sources. However, the lipid extraction from the algal biomass stands as a challenge due to its low yields and cost-intensive cell disruption procedures. In this study a multivariate optimization of the extraction conditions was suggested, aiming a maximization of the lipid extraction from Scenedesmus sp. microalgae grown using wastewater as a nutrient medium. The extraction method, extraction time, solvent mixture and pretreatment were considered between upper and lower levels in order to access their significance, including their interactions, on the experimental response, while using a reduced number of experiments. The studies were performed using low-cost extraction methods (magnetic stirring and ultrasonication). The optimal extraction condition was obtained using CHCl3:MeOH (2:1) solvent mixture, in a 2-hour extraction period using ultrasonication. Fatty acid profiles of extracted lipids were also evaluated.

Solid state reaction of serpentinite Mg3Si2O5(OH)4 with NaOH was investigated to produce new NaMgSi oxide phases with basic properties for application in catalysis. X-ray powder diffraction (XRD) showed that NaOH impregnated on serpentinite, specially 20% sodium and treated at 700 ºC (20Na700), led to the formation of a new crystalline phase Na2Mg2Si2O7. This solid state reaction is discussed in terms of a first step involving Na+ diffusion and intercalation in the interlayer space of the serpentinite structure followed by a dihydroxylation and formation of the NaMgSi oxides. Temperature programmed reaction and desorption experiments with 20Na700 combined with XRD suggested a strong basicity with high CO2 uptake likely due to diffusion and interaction with the basic sites in the material structure. These materials were tested as catalysts for the transesterification of soybean oil with methanol. The obtained results are discussed in terms of a basic site Si-O-Na+ present in the in the Na2Mg2Si2O7 structure.

It is presented herein heterogeneous catalysts comprised of strontium and nickel oxides synthesized using a coprecipitation method. They were applied for the preparation of biodiesel from macaw palm oil. The catalysts were characterized by X-ray diffraction (XRD), adsorption and desorption of nitrogen by Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and differential thermogravimetric analysis (TG-DTA). The conversion was determined by gas chromatography with flame detector (GC-FID). The best activity was obtained when the catalyst was calcined at 1100 °C for 3 hours. The highest conversion was reached (97%) when the following conditions were used: 5 hours, 2% of metal loading, 65 °C and oil/alcohol molar ratio of 1:9.

In this work, it was described the preparation and the characterization of a solid acid catalyst obtained by the mixture of Cr/Al oxides (CRAL). The catalyst was tested in the transesterification reaction of babassu oil with 5% of free fatty acid (FFA). The results of textural and acidity characteristics of CRAL were: area (56 m2 g-1), pore size (7.0 µm), total acidity (182.28 µmol g-1), wherein Brönsted sites are the most active. Powder X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) show three phases of the catalyst (Cr2O3/Na2Cr2O3/Al2O3), 0.25:0.25:0.50, respectively. The reaction reached conversion about 98.6% under the conditions: alcohol/oil molar ratio (24:1), catalyst to oil mass ratio of 3.0%, 15 h and 70 ºC. The turnover frequency (TOF) found was 24.5 × 10-4 s-1. Kinetic of the reaction was researched over a temperature range of 60-80 ºC. A pseudo first-order model was proposed with the activation energy (Ea) of 49.18 kJ mol-1. CRAL is active in the biodiesel production for just one cycle, because in the second one it loses its activity. The leaching of catalyst is about 13%, demonstrating that the catalyst is not totally heterogeneous.

Este trabalho descreve a preparação de biodiesel proveniente de óleo de babaçu, mamona e misturas destes em várias proporções, utilizando compostos alcalinos de estrôncio (SrO + SrCO3 + Sr(OH)2) como catalisadores heterogêneos. A mistura de óleos dessas oleaginosas foi utilizada na produção de biodiesel com parâmetros de qualidade que atendam a legislação vigente. O catalisador foi caracterizado por difratometria de raios X (XRD), fisissorção de gas (método BET), microscopia eletrônica de varredura (SEM), espectroscopia de raios X por dispersão em energia (EDX) e espectroscopia no infravermelho com transformada de Fourier (FTIR). Os parâmetros reacionais foram acompanhados através da viscosidade dos biodieseis obtidos. As reações de transesterificação usando os compostos de estrôncio apresentaram taxas de conversões de 97,2% (óleo de babaçu), 96,4% (óleo de mamona) e 95,3% (mistura de óleo de babaçu com óleo manona na proporção de 4:1).

This work describes the preparation of babassu, castor oil biodiesel and mixtures in various proportions of these oils, using alkaline compounds of strontium (SrCO3 + SrO + Sr (OH)2) as heterogeneous catalysts. The mixture of oils of these oleaginous sources was used in the production of biodiesel with quality parameters that meet current legislation. The catalyst was characterized by X-ray diffractometry (XDR), physisorption of gas (BET method), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). The viscometric technique was used to monitor the optimization. The transesterification reactions performed using strontium compounds reached conversion rates of 97.2% babassu biodiesel (BB), 96.4% castor oil biodiesel (COB) and 95.3% Babassu/Castor Oil Biodiesel 4:1 (BBCO41).

Glicerol, um sub-produto da produção de biodiesel, pode reagir com ácidos di-carboxílicos, resultando em poliésteres, e ser usado na composição de resinas do tipo uréia/formaldeído ou fenol/formaldeído para melhorar as qualidades de aderência e resistência à umidade dessas resinas. Neste trabalho, foram sintetizados seis tipos de resinas derivadas do glicerol, sendo nomeadas GAA (glicerol/ácido adípico), GAAU (glicerol/ácido adípico/uréia), GAF (glicerol/ácido ftálico), GU (glicerol/uréia), GUF (glicerol/uréia/formaldeído) e GF (glicerol/formaldeído). As resinas derivadas dos ácidos carboxílicos tiveram melhor estabilidade térmica (até 350 ºC) do que as resinas derivadas do formaldeído (até 200 ºC). As massas moleculares médias das resinas foram determinadas por espectrometria de massas por tempo de vôo acoplada à ionização dessortiva de matriz por laser (MALDI-TOF MS) e cromatografia de permeação em gel (GPC), e encontram-se na faixa de 1800-2800 Da, sendo portanto, oligômeros, e os índices de polidispersão no intervalo de 1,3 a 1,8. As técnicas de ressonância magnética nuclear (NMR) de ¹H e 13C foram usadas para identificar as estruturas das resinas.

Glycerol, a by-product from biodiesel production can react with di-carboxylic organic acids, resulting in polyesters, and can be used in the composition of urea/formaldehyde or phenol/formaldehyde resins to improve the qualities of adhesion and moisture resistance of them. In this work, six kinds of resins derived from glycerol, named as GAA (glycerol/adipic acid), GAAU (glycerol/adipic acid/urea), GAF (glycerol/phtalic acid), GU (glycerol/urea), GUF (glycerol/urea/formaldehyde) and GF (glycerol/formaldehyde), were synthesized. The resins derived from carboxylic acids had better thermal stability (up to 350 ºC) than those derived from formaldehyde (up to 200 ºC). The average molecular weights of the resins were determined by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and gel-permeation chromatography (GPC), and are in the range of 1800-2800 Da, being oligomers, and the polydispersity indexes are in the range of 1.3 to 1.8. The ¹H and 13C nuclear magnetic resonance (NMR) techniques were used to identify the structure of the resins.