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Brazil is one of the most powerful agro-industrial countries in the world impacting important chains of food, energy, and materials supplies. Residues resulting from this manufacture attract environmental and economic concerns for those producers. Aiming to focus on decentralized bioenergy production for local communities of the Midwest region, this work reports the physicochemical characterization of fruit peels of Baru (FPB), barks of Jatoba-do-cerrado tree (BJC), and their potential as raw materials for energy generation by gasification. FPB and BJC were analyzed by proximate analysis (12.0 and 11.6% of moisture, 71.2 and 75.4% of volatiles, 2.6 and 1.1% of ashes, and 26.2 and 23.5% of fixed carbon content), lignocellulosic analysis (21.7 and 13.3% of extractives, 65.8 and 60.7% of holocellulose, and 31.8 and 38.1% of lignin), and higher heating value (HHV), 19.7 kJ g−1 and 20.4 kJ g−1 for FPB and BJC, respectively. Both were used as fuel in a countercurrent gasifier (updraft) for the production of synthesis gas to generate energy, achieving satisfactory results, 25% and 15% of H2, 33% and 36% of CO, and 14% and 4% of CO2 for FPB and BJC, respectively. These results were similar or better than other biomasses reported in the literature. Since FPB and BJC are agricultural residues without a specific purpose, this work showed that decentralized bioenergy conversion by thermochemical process can benefit local producers.

O presente trabalho é um apanhado bibliográfico versando sobre a perícia de impressões digitais latentes em suportes porosos, especialmente em dinheiro. São expostos reveladores pertinentes a esse tipo de suporte e os esforços envidados, por instituições de diversas nacionalidades, ao tentar definir metodologias eficazes à revelação de impressões latentes em cédulas de dinheiro, tanto verdadeiro quanto falso. As metodologias encontradas apontaram procedimentos tão diversos quanto a variedade de espécies de cédulas estudadas, demonstrando que uma metodologia adequada ao dinheiro brasileiro não pode ser trazida de estudos internacionais sem devidas considerações e um processo de contextualização. A busca por impressões em cédulas falsas também deve ser tomada com a complexidade que representa, apesar de ser mais simples do que dinheiro verdadeiro, o conhecimento prévio dos aspectos intrínsecos ao suporte é determinante para o sucesso dos exames periciais e imprescindível ao definir como estes serão conduzidos.

The main objective of this work was to design an innovative method to prepare heterogeneous heteropolyacid catalysts. The heteropolyacid H3PW12O40 (HPW) was modified with tin(II) by two methodologies: a conventional aqueous ion-exchange (CS) and a redox solid-state (SS). In both cases, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) measurements evidenced that Keggin structure was preserved. All materials were active in the esterification of lactic acid with several alcohols and a mechanism was proposed. The best results were obtained for octanol and benzyl alcohol, where higher conversion values were obtained. The catalytic activity (turnover frequency, TON) showed an efficient performance for the materials prepared with 4 h of calcination (CS4h and SS4h). However, the catalyst prepared by the SS method was in accordance with the development of environmentally friendly processes.

Understanding the effects of synthetic parameters in the catalytic activity of heterogeneous catalysts is of utmost importance when aiming for optimal reaction conditions. Hence, we disclose in this work the synthesis and characterization of cerium-modified MCM-41 materials. In addition, it was observed for the first time, differences in catalytic activity when using different cerium synthetic precursors: CeCl3&middot, 7H2O and Ce(NO3)3&middot, 6H2O (Ce-MCM-Cl and Ce-MCM-NO3, respectively). A mechanism for cerium incorporation in MCM-41 was proposed, where [Ce(OH)3] species were hydrogen bonded to silicate anions, forming framework Ce-O-Si bonds during condensation and, consequently, causing distortion of the typical hexagonal mesophase. It was also observed that Ce(OH)3 formed aggregated layers with template assemblies during synthesis, resulting in non-framework CeO2 species on the MCM-41 surface after calcination. These CeO2 species were preferentially formed for Ce-MCM-NO3 and were attributed to the nitrate ions&rsquo, strong binding to template molecules. In the solvent free liquid-phase oxidation of benzyl alcohol (BzOH), Ce-MCM-Cl achieved better BzOH conversions and benzaldehyde (BzD) yields, while Ce-MCM-NO3 offered increased BzD selectivity. The catalysts&rsquo, reusability was also studied over three catalytic runs, where Ce-MCM-NO3 was more resistant than Ce-MCM-Cl towards deactivation. The observed catalytic behavior shows the importance of metal precursors in the obtainment of materials with desirable final properties.

Zeolite Y was dealuminated in the solid-state at several degrees (5, 10, 15 and 20%) using (NH 4 ) 2 SiF 6 as dealumination agent. The materials were heated to 80, 100, 120, 140, 160, 180 and 200 °C to investigate the best temperature at which the samples retain their crystallinity and acidity. The solids obtained were characterized by XRD, FTIR, TG/DTG, XRF, 27 Al and 29 Si MAS NMR and N 2 physisorption. They were also subjected to pyridine adsorption and calorimetric experiments. Structural and textural results showed that lower temperatures (80 and 100 °C) and smaller degrees of dealumination (5 and 10%) maintained the zeolite crystallinity and increased its specific surface area, microporosity and mesoporosity. The study of the materials acidity indicated the presence of Bronsted acid sites with different strength, hydrogen bonding sites and Lewis sites originated from acid leaching. The calorimetric measurements showed higher enthalpy values for some of the dealuminated materials than for the parent zeolite. It also evidenced an increase for the number of acid sites between −160 and −140 kJ mol −1 and a reduction for the other sites, between −140 and −80 kJ mol −1 .

In this study, we report the synthesis and physicochemical characterization of a novel one-dimensional copper(II) coordination polymer ([Cu(L)2]n) based on 2-acetylfuranisonicotinichydrazone, as well as its catalytic activity in the liquid-phase oxidation of benzyl alcohol. Based on spectroscopic and single crystal X-ray diffraction crystallography, the Cu(II) ion is pentacoordinated, bonded to two anionic hydrazones through the N,O chelating sites, and to the N-pyridyl atom from a third ligand molecule, which provides the formation of a one-dimensional network. The coordination polymer was evaluated as homogeneous catalyst, attaining high selectivity (90.1 %) and yield (36.9 %) towards benzaldehyde under mild conditions (70 °C, 2.10 mol% and 1:1 substrate-to-oxidant molar ratio). The efficiency was attributed to the slow tuning of the catalyst’s solubility in the reaction medium during the oxidation process by commitment of the use of an adequate solvent (acetonitrile) for efficient consumption of oxidant (TBHP) and formation of benzaldehyde. Titration experiments with TBHP, as well as an inhibitory essay, have shown the possible involvement of radical and peroxo reactive pathways in the reaction mechanism. Altogether, the results demonstrates that [Cu(L)2]n is suitable for accessible and mild fine chemical processes, in alignment with the search of environmentally friendly applications for industrial purposes.

The current manuscript describes the use of a heteropolyacid-containing task-specific ionic liquid, supported in imidazolium-based ionic liquids, as the catalyst for an efficient multicomponent synthesis of hexahydroimidazo[1,2-α]pyridine derivatives. The reactions conditions were fully optimized, and the bridgehead nitrogen heterocycle derivatives could be obtained in just 1 h exclusively as a single isomer ( trans). Single crystal X-ray analysis confirmed the trans derivative as the only isomer. The mechanism of the reaction was investigated by ESI(+)-MS(/MS), and the use of the elegant charge-tag strategy allowed a catalytic cycle to be proposed for the current transformation and revealed the possibility of at least two reaction pathways. One derivative bearing a coumarin scaffold was synthesized, and its fluorescent properties allowed it to be tested as a probe for live-cell imaging experiments with a preference for mitochondria.

The dealumination of zeolites has been studied to tune acidity, resulting in enhanced catalytic efficiency. MOR, FER, and ZSM-5 were dealuminated to remove 5, 10, 15, or 20 mol% of Al with (NH4)2SiF6 (solid-state reaction at 80 °C). XRD, SEM, and FT-IR showed structural maintenance. Aluminum removal was confirmed by the total Si/Al ratio (XRF and AAS) and 27Al MAS NMR. The dealuminated samples were tested in the dehydration of different alcohols and compared to the protonic parent zeolites. Dealuminated MOR samples exhibited a decrease in coke formation (maximum decrease of 18.3%, 18.2%, and 6.1% for methanol, ethanol, and 1-propanol dehydration, respectively), and an increase in conversion values (maximum increase of 29.0%, 13.9%, and 6.2% for methanol, ethanol, and 1-propanol dehydration). H-FER/20% showed an improvement in methanol (19.9%) and ethanol (3.8%) conversions and a reduction of coke (decrease of 8.6% and 5.6%, respectively), corroborating the highest value of acid sites (0.73 mmol g−1). All catalysts showed 100% selectivity to each desired product. The mechanisms for all dehydrations were related to the presence of Bronsted acid sites. Methanol dehydration might involve the generation of methoxonion ion, and ethoxy groups might be formed for ethanol conversion. For ZSM-5, Lewis acid sites may also participate in the elimination mechanism. High reaction temperature (300 °C) favored intramolecular dehydration to ethylene, avoiding formation of diethyl ether and oligomers. Structural defects on H-ZSM-5/15% could facilitate the access of 1-propanol to active sites, leading to the best combination of TON (0.67), conversion (100%), and coke formation (0.35%).

A task-specific ionic liquid with a Bronsted acid (1-(3-sulfopropyl)-3-methylimidazolium hydrogen sulfate, namely MSI ) bearing an anionic heteropolyacid derivative ([PW 12 O 40 ] 3− , namely PW ) were used as an efficient catalyst for the three-component Mannich and Hantzsch reactions. Using ( MSI ) 3 PW as the catalyst supported in imidazolium-based ionic liquids allowed these multicomponent reactions to take place in good to excellent yields. The Mannich reaction, performed at room temperature, was also evaluated by means of electrospray (tandem) mass spectrometry—ESI-MS(/MS). ESI-MS data pointed to the origin of the ionic liquid effect, i.e., formation of ion pairs with the charged reaction intermediates and furthers association into larger supramolecular aggregates. DFT calculations revealed the strength of the supramolecular interactions between the charged species detected by ESI-MS and the spontaneity association of these ion pairs affording larger supramolecular aggregates.

A celulose é o constituinte da biomassa mais abundante do mundo e é composta por biopolímeros de glicose. Um estudo prospectivo sobre celulose com ênfase em nanocelulose e catálise é apresentado sob duas perspectivas: indicadores tecnológicos baseados em documentos patentários e em artigos científicos indexados. Foram encontrados um total de 190.615 documentos patentários relacionados à celulose, sendo que 47,6% desse valor está compreendido no período de 2012-2016, majoritariamente depositados pela China e Estados Unidos. A fim de agregar valor à celulose, a nanocelulose tem apresentado destaque nas áreas de química e de materiais nos últimos anos. Dentre os subdomínios, a nanocelulose aplicada à catálise ainda apresenta baixa maturidade tecnológica sendo apresentados os indicadores desta baixa prontidão tecnológica e estabelecidas perspectivas para suas futuras aplicações.

Bronsted and Lewis acid catalysts with ionic tags under homogeneous and heterogeneous conditions have been tested to perform the Biginelli synthesis of 3,4-dihydropyrimidin-2(1H)-one (DHPMs). Metal-containing ionic liquids were evaluated as the catalysts with reasonable results (homogeneous systems). Heterogeneous catalysts (zeolite β and H3PW12O40 supported on zeolite β) have been tested, as well, with good to excellent results. The use of a functionalized acid ionic liquid with a heteropolyacid in the anion moiety (homogeneous system) gave the best results using no excess of the three reagents. The preferred mechanistic pathway was investigated by electrospray ionization (tandem) mass spectrometry in both positive and negative ion modes with very elucidative results. The ionic liquid effect and its origin were also investigated using mass spectrometry and DFT calculations.

This work deals with preparation and characterization of H3PW12O40 (H3PW) supported on silica-alumina. Impregnation of H3PW (15, 20, 30 and 40 wt.%) on commercial silica-alumina support in acidic aqueous solution is effective for preparing this catalyst keeping its Keggin structure, according to different methods of characterization. The catalysts were tested in a model reaction of acetic acid with ethanol and 30 wt.% H3PW/SiO2-Al2O3 had the highest activity under the conditions: catalyst calcination at 300 ºC, temperature of 100 ºC, acetic acid:ethanol molar ratio of 2:1 and catalyst:acetic acid mass ratio of 10 wt.%. The reaction yield was 79 and 100% selectivity for ethyl acetate over three reutilizations, for reaction time of 2 h. The calculated total acid site distribution was 0.299 mmol g-1 (97% of the theoretical probed by pyridine), and most of these (0.236 mmol g-1) were Brønsted weak-medium strength (pyridine desorption between 300 and 500 ºC).

In this work, activities of HUSY and Ce/HUSY zeolites were studied in transesterification cycles of soybean oil and ethanol to produce biodiesel. The characterization of the materials was performed by FT-IR, XRD, BET method and pyridine adsorption followed by thermal analyses. TG/DTG results indicated a decrease of acid sites for both samples after each reaction cycle. However, Ce/HUSY zeolite showed a superior stabilization of acidic sites after three catalytic cycles and intermediary activation procedures. Biodiesel production exhibited high conversion levels (>96%) for both zeolites in all transesterification cycles. Surface area and pore volume measurements evidenced that cerium incorporation reduced the number of acid sites by interacting with OH groups in the micropore and external area of the zeolitic surface. This interaction resulted in an acid and structural stability, which provided a better activity (99%) than HUSY (96%). The higher conversion values obtained by zeolites showed a final product with a different distribution when compared with the traditional transesterification process. The identification of free fatty acids, diethyl and glycerol ethers in the final products and the reduction of unsaturated compounds indicated that parallel reactions also occurred in the studied systems. Nonetheless, the biofuel produced showed high ester content and did not present changes in its calorific power.

Ammonium and cesium derivatives from H3PW12O40 (H3PW), namely (NH4)xCs2.5−xH0.5PW12O40 (x = 0.5, 1, 1.5, 2), were synthesized and structurally characterized by FT-Raman spectroscopy, and their thermal stability was evaluated by FTIR and TGA/DTA. The acidity was characterized by the adsorption/desorption of gaseous pyridine, by FTIR and TGA/DTA as well as by the reaction of oleic acid and ethanol. The stability of the mixed salts regarding the Keggin structure was much higher than the parent acid, with the onset decomposition around 520 °C. Nonetheless, calcination up to 300 °C is recommended for the integrity of the mixed salt. The FTIR of adsorbed pyridine displayed only Bronsted acidic sites, which was confirmed by TGA measurements of the formation of Py–H+⋯Py adducts. The best esterification result was for (NH4)2Cs0.5H0.5PW12O40 with TOF = 1.314 molEO mol−1 proton s−1 with a 1:6 (oleic acid:ethanol) molar ratio, at 80 °C and 10 wt% catalyst in relation to the acid.

Supported heteropolyacids (HPAs) have been used as catalysts by fine-tuning their heterogenous and Bronsted acidic properties. In this work, supported H 3 PW 12 O 40 (HPW) on MCM-41 was prepared (2–40 wt%) and applied in the intramolecular cyclization of (+)-citronellal. The synthesized materials were characterized by 31 P MAS NMR, XRD, FTIR, pyridine gaseous adsorption, low temperature nitrogen adsorption and thermal analysis. The impregnation of 20% HPW on the surface of MCM-41 decreased the characteristic crystallographic reflections of the support, suggesting that HPW modifies the long-range order. The results show that the HPW was deposited preferentially inside the mesopores of the support and affected the acid strength of the supported catalyst. FTIR studies of pyridine adsorption confirmed the presence of Bronsted and hydrogen bonded acid sites. All synthesized materials were active in the cyclization reaction, but the 20%HPW/MCM-41 sample was the most active. This catalyst showed about 96% conversion and 65% selectivity to the most important stereoisomer (−)-isopulegol, under 1 h reaction. This catalyst was reused four times with a fair degree of deactivation. The decreased activity was attributed to the formation of small agglomerates in the channels of MCM-41.

This work reports the synthesis, characterization and application of rare earth (La, Ce, Sm and Gd) trisdodecylsulfate materials as Lewis acid-surfactant-combined catalysts for the production of biodiesel from waste cooking soybean oil. All the solid materials showed a bilayer lamellar arrangement with the dodecylsulfate molecules in a head to head, tail to tail packing. The reaction between commercial feedstocks (soybean oil and oleic acid) with ethanol was used separately to study La, Ce, Sm and Gd catalyst activities for transesterification (conversions of 73, 92, 53 and 73%) and esterification (conversions of 87, 80, 75 and 85%) after 1 h, respectively. Among them, cerium(III) trisdodecylsulfate showed the highest catalytic activity (TOF = 29.5 mol h −1 mol cat −1 ) for transesterification, while lanthanum(III) and gadolinium(III) trisdodecylsulfates were the most active for esterification (TOF = 28.7 mol h −1 mol cat −1 ). The application of the studied catalysts for the simultaneous transesterification and esterification reaction of waste cooking oil, containing 8.8 wt.% of free fatty acids (FFAs), with ethanol showed conversions of 76 (3.3 wt.% of FFAs), 79 (5.3 wt.% of FFAs), 81 (2.5 wt.% of FFAs) and 86% (0.0 wt.% of FFAs) after 1 h for La, Ce, Sm and Gd catalysts, respectively. Thus, gadolinium(III) trisdodecylsulfate was the best material for the conversion of waste feedstock to produce biodiesel. However, cerium(III) trisdodecylsulfate was less susceptible to deactivation, exhibiting conversion values of 92, 81 and 77% for the 1st, 2nd and 3rd reaction cycles. The catalysts were characterized by elemental analysis, X-ray powder diffraction (XRD), 1 H NMR, thermal analysis (TG/DTG/DTA) and FTIR measurements.

Mixed oxides of CexZr1−xO2 (0.1 ≤ x ≤ 0.9) were prepared by sol–gel method, in aqueous ammonia solution with CeCl3·7H2O and ZrOCl2·8H2O as precursors, and employed in diesel soot combustion. The catalysts were characterized by XRF/EDX, nitrogen adsorption, TGA/DTG, powder XRD, FTIR/DRIFTS and Raman. In addition, the acidity was evaluated by adsorption and desorption of pyridine. XRD indicated the formation of solid solutions that progressively distorted from cubic into tetragonal lattices. Raman studies confirmed that the Ce–O bonding was stronger in the mixed oxide series because of the cell contraction, as a result of the zirconium insertion. Ce0.8Zr0.2O2 was the most acidic and active material, shifting the combustion temperature (Tm) from 622 to 547 °C (loose contact) or 404 °C (tight contact). The calculated activation energy for the catalytic combustion of this optimized oxide attested that the combustion temperature was lower under all conditions, compared to the thermal process. The catalyst was utilized five times without any appreciable loss of activity and maintained its structural properties.

Zeolites have occupied a distinguished position due to their unique properties as solid acids and catalytic results achieved in several industrial reactions. This work studied the influence of supported WO 3 on USY zeolite structure, acidity and activity towards an esterification reaction. High dispersion of WO 3 species on USY was achieved, but at higher loading (⩾11.4%), microcrystalites of WO 3 were detected below the theoretical monolayer coverage (∼32%). Tungsten species were deposited preferentially inside the zeolite structure and interacted with the Bronsted sites of USY as well as on silanol surface groups with the formation of small aggregates. In addition, dealumination took place, especially in the samples with high WO 3 loading. USY had the most and the strongest acidic sites (Bronsted type), but the incorporation of WO 3 decreased the amount and the strength of the new sites. However, all WO 3 /USY catalysts were more active than USY in the esterification of oleic acid with ethanol (conversion above 74%, 2 h at 200 °C). The calculation of the TOF for a 1 h reaction demonstrated that 11.4% WO 3 /USY was the most active catalyst. Furthermore, it had the lowest rate of deactivation of acid sites after the reaction (∼13% after four cycles). The better performance of the 11.4% WO 3 /USY sample was also attributed to a better distribution of strength of the acidic sites and a more hydrophobic character of the synthesized material.

Este trabalho descreve detalhadamente o efeito da quantidade de cério na estrutura e morfologia da zeólita NH4USY. Ce-USY (2-25% m/m de CeO2) foi obtido por impregnação úmida de CeCl3 seguida de calcinação a 550ºC por 8 h. Em quantidades baixas (2-10%), foi observado que as espécies de cério encontram-se nas posições de troca iônica na rede, enquanto em maiores teores (15-25%) pequenos agregados formaram-se na superfície da HUSY. Difratometria de raios X (XRD) mostrou apenas reflexões relacionadas à HUSY, confirmando a alta dispersão das espécies de cério, porém as análises por espectroscopia Raman com transformada de Fourier (FT-Raman) detectaram CeOx para os materiais acima de 10%. A reação do CeCl3 com NH4USY produziu NH4Cl, o qual se decompõe em HCl, ocasionando a desaluminização da rede. Os materiais apresentaram um aumento da razão Lewis/Brønsted com o aumento da quantidade de cério, devido a interação do excesso de cério com os grupos OH da USY e consequente formação de espécies CeOx. This work describes comprehensibly the effect of cerium loading on the structure and morphology of NH4USY zeolite. The Ce-USY (2-25 wt.% of CeO2) was obtained by wet impregnation of CeCl3 followed by calcination at 550ºC for 8 h. At low loadings (2-10%), cerium species are mainly located at ion exchange positions in the framework, whereas at higher loadings (15-25%), small aggregates were formed on the HUSY surface. X-ray diffractograms (XRD) exhibited only the reflections related to HUSY, demonstrating the high dispersion of cerium species, but Fourier transform Raman spectroscopy (FT-Raman) detected CeOx for the materials above 10%. Reaction of CeCl3 with NH4USY produced NH4Cl, which decomposed to form HCl, leading to framework dealumination. The materials showed an increased Lewis/Brønsted ratio with increasing cerium loadings due to the interaction between the excess cerium and the OH groups of USY, and the consequent formation of CeOx species.

The surface acidity of the molecular sieve Si-MCM-41 was investigated by liquid phase calorimetric-adsorption analysis (Cal-Ad), gas adsorption measurements (TG-TPD) and infrared spectroscopy using pyridine as the probe molecule. The results showed that Si-MCM-41 evacuated at 200 °C had one type of hydrogen bonding site (n1 = 2.27 mmol g−1 with ΔH1 = −95.3 kJ mol−1) that was much stronger than those in silica gel. These sites corresponded to the total OH groups of the material surface and were able to retain pyridine at higher temperatures than silica gel (400–600 °C). In addition, the material had a higher entropy value (ΔS1 = −250 J K−1 mol−1) than silica gel. This indicates that pyridine is more strongly adsorbed on the surface of Si-MCM-41 than silica-gel, which leads to better catalyst properties. Solid-state 29Si MAS-NMR measurements showed a high amount of silanol groups (52%) in the Si-MCM-41 structure (for the Q2 and Q3 species). These results suggest a highly polar environment caused by the hydroxyl groups that line the walls of the hexagonal long-range ordered pores.

Mixed salts of cesium and ammonium derivatives of H3PW12O40 ((NH4)xCsyH0.5PW) were synthesized by a precipitation/ion exchange method with a different addition order for each cation. The produced salts were characterized by FTIR, XRD, 31P MAS NMR, SEM, pore size and the BET method. FTIR demonstrated that the materials maintained the Keggin structure under all tested conditions. BET results showed that salts formed by proton substitution from ammonium to cesium had much higher surface areas. Characterization by 31P MAS NMR and XRD, demonstrated that the salt structures varied sharply with the degree of hydration. After calcination, the materials were confirmed to have characteristics of solid solutions with random distribution of the cations with similar crystallographic patterns. The primary nanocrystals aggregated to form solids with mesoporous and microporous structures, created by partial unidirectional growth of the nanocrystals during formation of the bigger, round microcrystallites about 0.3–1 μm in size.

Catalysts of H3PW12O40 (H3PW) supported on Nb2O5 were prepared with a wide range of loadings (20–60 wt%) and characterized by FTIR, FT-Raman, XRD, 31P MAS NMR, the BET method and pyridine adsorption in the gas phase. In addition, the acidity was measured by the Cal-Ad method, which combines microcalorimetry and adsorption of pyridine on the solid samples in cyclohexane slurry. Preparation of the catalysts involved two procedures: impregnation in aqueous acid or acetonitrile solutions with further calcination at 200 °C for 8 h. No decomposition of H3PW was observed under these conditions. The results indicated the formation of well-dispersed H3PW species on materials with loadings up to 30 wt%, prepared preferentially in aqueous acid solution. A strong interaction between the heteropolyacid and niobia surface was observed forming species such as [ NbOH 2 ] n + [ H 3 - n PW 12 O 40 ] n - 3 . The H3PW/Nb2O5 materials containing 20–40 wt% presented type II isotherms and showed that surface area, pore volume and pore size decreased as the amount of H3PW increased, whereas the micropore area increased with H3PW loading. According to gaseous pyridine adsorption results, the catalysts presented only Bronsted sites. Microcalorimetric titration demonstrated that the 25 wt% material was the most acidic. The Cal-Ad method provided the enthalpy and number of sites for the strongest interaction with pyridine as: ΔH1 = −119.7 kJ mol−1 and n1 = 0.086 mmol g−1. About 33% of the protons were available for 25% H3PW/Nb2O5, in comparison to only 8% for pure H3PW. A considerable increase in the surface protons was achieved by H3PW on niobia surface.

Esterification of organic acids with alcohols produces an industrially important class of substances with a variety of applications. This work presents an impregnation route to support H3PW12O40 (H3PW) on zirconia (ZrO2) in acidic aqueous solution (HCl 0.1 mol L−1) at different ratios (5, 10, 15, 20, 25, 40 and 60 wt%), which were further applied in the esterification of oleic acid with ethanol. Impregnated samples calcined at 200 °C for 4 h were characterized by FTIR, FT-Raman, XRD, 31P MAS NMR and BET surface area. No decomposition of the Keggin anion structure was observed under these conditions. The XRD results, surface area determination and catalytic tests pointed out that H3PW was well dispersed over the support and only a monoclinic phase of the commercial ZrO2 was detected. An optimum reaction performance (88% of oleic acid conversion) was achieved at 20 wt% loading, 100 °C, 4 h reaction and 1:6 (acid:ethanol) molar ratio. A small leaching of 8 wt% of the initial mass of this catalyst (i.e., the actual loading was 18.4 wt%) was also observed at the end of reaction, which affects the reaction kinetics. Thermal stability studies of 20%H3PW/ZrO2 catalyst, determined by 31P MAS NMR, XRD and FT-Raman revealed that Keggin anion decomposition begins at ca. 500 °C, which was confirmed by the respective decrease of the catalytic activity. A preliminary study of recyclability indicated that a treatment of the spent catalyst involving a sequence of washing with n-hexane, drying at 100 °C and calcining at 300 °C for 4 h, recovered conversion values as high as 70%.

This article reports the synthesis, characterization and application of cerium(III) trisdodecylsulfate trihydrate (Ce[OSO3C12H25]3·3H2O) as a Lewis acid-surfactant-combined catalyst for the production of alkyl esters by solvent-free transesterification and esterification reactions. The new material presents a bilayer lamellar arrangement with an interplanar spacing of d001 = 3.76 nm, and the dodecylsulfate headgroup in a C2v symmetry. The reaction of soybean oil and oleic acid with light alcohols (methanol and ethanol) was used as model reactions and high catalytic activity (TOF = 57.4 mol h−1 molcat−1) was observed. The catalyst converted the used feedstocks to esters in less than 4 h with yields greater than 95%. In addition, it can be used to produce biofuels from unrefined and waste oils in which both triacylglyceride and free fatty acid molecules are present. After reaction, the recovered catalyst maintained its activity (≥95%) for three cycles. The catalyst was characterized by elemental analysis, X-ray powder diffraction (XRD), thermal analysis (thermogravimetry (TG)/derivative thermogravimetry (DTG)/differential thermal analysis (DTA)), pyridine adsorption, and spectroscopic analysis (FTIR and NMR).

This work deals with the preparation and application of new catalysts based on CuO, Nb 2 O 5 , and Si-MCM-41 for the abatement of diesel soot particulates. The properties of Si-MCM-41 mesoporous material were enhanced by studying the effect of the template removal method on specific surface area, terminal silanol groups, and long-range ordering. Template removal experiments indicated that thermal decomposition by double-step calcination at 300 °C for 3 h and 550 °C for 3 h produced a material with the best morphological characteristics. This material was used to prepare CuO/Nb 2 O 5 /MCM-41 catalysts with a 1:1 mass ratio (CuO:Nb 2 O 5 ) and 2, 5, 10, 15, and 25 wt.% loadings. The incorporation of CuO and Nb 2 O 5 leads to the formation of well-dispersed small crystallites and an amorphous phase, respectively, for the samples with lower oxide loadings. For the samples with higher oxide loadings, the crystallites increase in size, leading to the formation of copper–niobium mixed oxide phases and agglomerates. All the prepared materials presented considerable activity towards the oxidation of diesel soot particulates, shifting the maximum oxidation temperature ( T ox ) to lower values. The most promising catalyst was CuO/Nb 2 O 5 /MCM-41 with 25 wt.% of each oxide, which presented an onset temperature of 388 °C and appreciable activity at temperatures as low as 450 °C without the addition of any chemical promoter.

Metalloporphyrin catalysts are able to carry out selective oxidation of organic substrates with several oxidizing agents. Recently, mesoporous materials have been studied as supports because they present high specific surface area, better dispersion and regeneration properties. This work presents the results of synthesis, characterization and application of three metalloporphyrin catalysts (FeTPPCl, MnTPPCl and CoTPP, where TPP = tetraphenylporphyrin) anchored on MCM-41, in the reaction of cyclohexene oxidation with hydrogen peroxide. A modified sol–gel preparation was chosen for the synthesis of the MCM-41 mesoporous material, as well as the anchoring was followed by Soxhlet extraction to ensure strong adsorption of the complex. The supported materials were much more stable than pure metalloporphyrins. The synthesized catalysts were characterized by UV–vis, FTIR, XRD, ICP-AES, 29 Si MAS-NMR and thermal analysis, before and after incorporation. Evidence of the metalloporphyrin immobilization was confirmed by elemental analysis and their activity in the oxidation reaction. FeTPPCl/MCM-41 showed higher conversion than CoTPP/MCM-41 and MnTPPCl/MCM-41. However, MnTPPCl/MCM-41 even in low concentration on the support showed a good conversion for the direct oxidation of cyclohexene with the highest turnover number (1.54 × 10 5 ). All catalysts showed similar selectivity that favors allylic oxidation products over epoxidation. No leaching of the metalloporphyrins was observed after the reaction.

Incorporation of niobium into microporous molecular sieves brings up new properties for these materials. ZSM-5 supported catalysts containing 2, 5, 13 and 19 wt.% of niobium pentoxide were prepared by aqueous impregnation and characterized by the combination of thermal (TG/DTA) and spectroscopic methods such as FTIR, FT-Raman, DRIFTS, and 29 Si and 27 Al MAS and 29 Si CP-MAS-NMR. In addition, X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and measurements of specific surface area by nitrogen adsorption (BET method) were carried out in order to obtain structural, textural and stability information about the solids. The samples were studied at different temperatures and heating time to optimize these parameters and to avoid a possible reduction of acidic properties by dehydroxylation. MAS-NMR and XRD results showed that the zeolite structure containing Nb did not undergo dealumination after thermal treatment, according to the presence of Si O Nb units on the zeolites structure in FTIR and Raman studies. Thermal analysis confirmed that Nb 2 O 5 impregnation reduced zeolite ZSM-5 dehydroxylation and thus promoted thermal stabilization. Nitrogen adsorption isotherms by the BET method indicated that surface area and pore volume decreased with the increase of Nb loading on the calcined samples at 450 °C. In addition, the nature of the zeolite active sites was investigated by spectroscopic and thermal analysis after pyridine adsorption. It was proposed that there are two different acidic sites (Bronsted and hydrogen bond site types) on the studied systems.

Biodiesel fuel (fatty acid esters) has become more and more attractive due to its environmental benefits. Transesterification is the most common and important method for making biodiesel from vegetable oils or animal fats. Several studies have focused on the development and improvement of analytical methods for monitoring biodiesel production and determining the fuel quality. Analytical procedures reported in the literature include chromatographic methods (e.g., gas chromatography, high-performance liquid chromatography, gel permeation chromatography, etc.) and spectroscopic methods [e.g., 1H and 13C NMR, near infrared, Fourier transform infrared spectroscopy, and recently, Fourier transform (FT)-Raman]. The study presented in this paper expands our previous research, in which FT-Raman spectroscopy combined with partial least squares (PLS) multivariate analysis was successfully applied to the quantification of soybean oil/ethyl ester mixtures. The FT-Raman/PLS methods developed by our group were used to m...

USY (ultrastabilized Y) and Ce/USY (5 wt.% supported) zeolite acidities were characterized by microcalorimetric and adsorption studies of pyridine using liquid phase (Cal-Ad), thermogravimetry, and infrared analysis. The average adsorption enthalpies determined by microcalorimetry were −125.0 kJ mol−1 for USY and −97.2 kJ mol−1 for Ce/USY. A heterogeneous distribution of acid sites with heats of adsorption ranging from −134.0 (maximum heat value for USY) to −73.5 (minimum heat value for Ce/USY) kJ mol−1 was found for both zeolites. A two-site model was best fitted by the Cal-Ad method for HUSY (n1 = 0.1385 mmol g−1 with ΔH1 = −134.0 kJ mol−1, and n2 = 0.7365 mmol g−1 with ΔH2 = −101.5 kJ mol−1) and Ce/HUSY (n1 = 0.0615 mmol g−1 with ΔH1 = −117.6 kJ mol−1, and n2 = 0.7908 mmol g−1 with ΔH2 = −83.6 kJ mol−1). DRIFTS measurements after pyridine adsorption showed that USY zeolite possesses only Bronsted acidity and that cerium impregnation leads to the appearance of Lewis sites. Based on these results, three families of acid strength were distinguished: (i) strong Bronsted sites (ΔH > −130 kJ mol−1); (ii) Bronsted sites with intermediate strength (−100

Biodiesel (FA esters) has become very attractive as an alternative diesel fuel owing to its environmental benefits. Transesterification is the most usual and important method to make biodiesel from vegetable oils. This article investigates the potential for using Raman spectroscopy to monitor and quantify the transesterification of soybean oil to yield ethyl esters. The differences observed in the Raman spectra of soybean oil after transesterification were a peak at 2932 cm−1 ( $$v_{CH_2 }$$ ), the displacement of the v C=O band from 1748 to 1739 cm−1, and the bands at 861 (v R-C=O and v C-C) and 372 cm−1 (δ CO-O-C). Uni- and multivariate analysis methods were used to build several analytical curves and then applied in known samples, treated as unknowns, to test their ability to predict concentrations. The best results were achieved by Raman/PLS calibration models (where PLS=partial least squares regression) using an internal normalization standard (v =C-H band). The correlation coefficient (R 2) values so obtained were 0.9985 for calibration and 0.9977 for validation. Univariate regression analysis between biodiesel concentration and the increasing intensity of $$v_{CH_2 }$$ band or v C=O displacement showed R 2 values of 0.9983 and 0.9742, respectively. Although spectroscopic methods are less sensitive than chromatographic ones, the data obtained by spectroscopy can be correlated with other techniques, allowing biodiesel yield and quality to be quickly assessed.

Supported niobium pentoxide materials have been effective catalysts for a variety of acid and redox reactions (e.g., dehydration of alcohols, esterifications, etc.). To the best of our knowledge, there are no reports about Nb2O5 supported on silica−alumina. Catalysts of Nb2O5/SiO2−Al2O3 were prepared with 2, 5, 10, 15, 20, and 25 wt % of Nb2O5 by aqueous solution impregnation using ammonium niobium oxalate on silica−alumina. The materials, after being dried at 100 °C, were calcined at 800 °C and characterized by several methods. Investigation through X-ray diffraction showed the typical patterns of crystalline Nb2O5, which were composed of mixtures of orthorhombic and monoclinic phases (T, M, and H, respectively) present in the materials with content higher than 10 wt %. DTA curves displayed an exothermic peak at 1356 °C (average) without mass loss (confirmed by TG), which may be ascribed to a phase transition (H phase formation) of Nb2O5 supported on silica−alumina. Pure Nb2O5·nH2O showed a transition fr...

The interaction of hydrophobic chitin and chitosan with sodium dodecyl sulfate (SDS) has been studied by titration calorimetry at 298.15K. The nature of interaction of the surfactant and biopolymers was followed by enthalpy interaction profiles. The mixing enthalpy curves were determined by mixing SDS solutions above their critical micelle concentration with chitin and chitosan suspensions in different concentrations. The Gibbs free energy of aggregation values were -23.21, -22.71 and -21.53 kJ mol(-1) for chitin in 0.02, 0.05 and 0.1% concentration, respectively, and 28.30, 24.38 and 24.20 kJ mol(-1) for chitosan in 0.02, 0.05 and 0.1% concentration, respectively. The critical aggregation concentration (cac) obtained by calorimetric data gave 6.32, 7.07 and 9.14 mmol kg(-1) in 0.02, 0.05 and 0.1% concentration, respectively, for chitin and 2.09, 4.91 and 5.11 mmol kg(-1) for chitosan in 0.02, 0.05 and 0.1% concentration, respectively.

O biodiesel é um biocombustível importante para a matriz energética nacional é produzido de diferentes fontes oleaginosas, desempenhando papel importante na produção final do biocombustível. Diante de sua cadeia produtiva e da importância de métodos mais sustentáveis, realizou-se um estudo prospectivo sobre o processo simultâneo de produção de biodiesel visando à condensação das etapas de produção via simultaneidade de extração e respectiva conversão a partir de resíduos agroindustriais oleaginosos. Além disso, tem-se como objeto de estudo a utilização de catálise heterogênea ao sistema, agregando facilidades na separação do produto e do meio catalítico. Neste nicho de pesquisa e desenvolvimento de métodos alternativos para o setor do biodiesel encontram-se poucas patentes e artigos, sendo em sua maioria evidenciados processos em escala laboratorial. Sendo assim, tal tecnologia merece atenção, investimento e desenvolvimento para seu escalonamento, tendo em vista agregar diversos benefícios ao setor, desde a matéria-prima até o processo e distribuição.

A task-specific ionic liquid with a Bronsted acid (1-(3-sulfopropyl)-3-methylimidazolium hydrogen sulfate, namely MSI ) bearing an anionic heteropolyacid derivative ([PW 12 O 40 ] 3− , namely PW ) were used as an efficient catalyst for the three-component Mannich and Hantzsch reactions. Using ( MSI ) 3 PW as the catalyst supported in imidazolium-based ionic liquids allowed these multicomponent reactions to take place in good to excellent yields. The Mannich reaction, performed at room temperature, was also evaluated by means of electrospray (tandem) mass spectrometry—ESI-MS(/MS). ESI-MS data pointed to the origin of the ionic liquid effect, i.e., formation of ion pairs with the charged reaction intermediates and furthers association into larger supramolecular aggregates. DFT calculations revealed the strength of the supramolecular interactions between the charged species detected by ESI-MS and the spontaneity association of these ion pairs affording larger supramolecular aggregates.

Polyoxometalates are large metal–oxygen nanostructured compounds that can be modified at the molecular level. Catalysts based on 12-tungstophosphoric acid (H3PW12O40) supported on different carries such as silica, silica–alumina, zirconia, and mesoporous MCM-41 have been successfully prepared and characterized by several physicochemical techniques (e.g., FTIR, FT-Raman, 31P MAS-NMR, calorimetry, thermal analysis, TPD of pyridine). The materials were tested in different reactions: transalkylation of benzene with aromatics, esterification of acetic acid and ethanol, esterification of oleic acid with ethanol, and cyclization of (+)-citronellal. The results, coupled with other applications of heteropoly acids in the literature, illustrate the potential for these catalysts to be used in greener processes, i.e., a more effective, selective, economical, and environmentally benign technique. The effects of support interaction, loading of H3PW12O40, calcination temperature and stability, leaching, and acidity were addressed for all studied catalysts. These data were correlated to the conversion and/or selectivity of the main product and were used for recovery of the catalysts. Moreover, it was clear that the strength of interaction of the heteropoly acid with the surface support as well as the acidity define the capacity of utilization of these catalysts. Effective ways to recovery the initial activity is still a challenge to take full advantage of these materials.

Neste trabalho, teve-se como objetivo a preparação de zeólitas básicas através da modifcação de zeólitas USY com bário e estrôncio e sua aplicação na reação de transesterifcação de óleo de soja com etanol, para produção de ésteres de etila (biodiesel). Além disso, foram estudados os efeitos da geração de sítios básicos na superfície dos catalisadores, bem como suas respectivas atividades por três ciclos catalíticos. O biodiesel obtido nos ciclos foi analisado por HPLC, CG-FID e espectroscopia Raman. Já os catalisadores foram caracterizados por FTIR, análises térmicas e adsorção gasosa de piridina e CO2. Soybean oil transesterifcation with ethanol was carried out in a batch reactor using USY zeolites modifed with barium and strontium (15 wt.%) as catalysts. A series of three catalytic cycles were performed for each zeolite without any loss of activity. The biodiesel product was analyzed by HPLC and FT-Raman, and the catalysts by pyridine and CO2 adsorption. Ba/USY provided higher conversions (> 97%) than Sr/USY (< 75%). The increased catalytic activity of Ba/USY was attributed to two different effects: a larger number of basic sites; and a lower interaction between barium species and HUSY Brønsted sites.

Zeolite beta acidity, activated at 550 degrees C, was characterized by calorimetric and adsorption studies of pyridine in cyclohexane (Cal-Ad). Two different acid sites were found: n(1) = 0.1612 mmol g(-1) with DeltaH(1) = -83.6 kJ mol(-1); and n(2) = 0.3820 mmol g(-1) with DeltaH(2) = -62.8 kJ mol(-1). Step calcinations followed by FTIR indicated n(1) as Lewis sites and n(2) as weak Brønsted sites. When activated at 450 degrees C, zeolite beta showed three different sites: n(1) = 0.0467 mmol g(-1) with DeltaH(1) = -227.3 kJ mol(-1); n(2) = 0.1163 mmol g(-1) with DeltaH(2) = -93.3 kJ mol(-1); and n(3) = 0.3322 mmol g(-1) with DeltaH(3) = -80.4 kJ mol(-1). Sites n(1) and n(2) were assigned as Brønsted centers, while n(3) as a combination of Brønsted and Lewis sites. These results suggest that the zeolite beta strongest Brønsted sites are converted to Lewis sites at 550 degrees C. These Lewis sites are not only related to extra-framework Al species, but also to aluminium atoms partially bonded to the zeolite framework, as evidenced by infrared bands at 3777 and 875 cm(-1). FTIR and thermogravimetric analyses of gas phase adsorbed pyridine were also used to investigate the materials acidity and a good agreement was found with Cal-Ad data. The results showed that the Cal-Ad method offers a more detailed description of the zeolite surface acidity by providing thermodynamic parameters not easily obtained by other techniques. A linear relationship between enthalpy and entropy values for several zeolites (ZSM-5, TS-1, MOR, Y and BEA) is also reported.

Acid strength distribution measurements of zeolite Y by a combined analysis of calorimetric and adsorption data, Cal-ad, for the reaction of zeolite Y with pyridine, 2,6-lutidine, 2,6-di-tert-butylpyridine, quinoline, tetrahydrothiophene and benzonitrile show the presence of three families of acid sites. The strongest sites (heats above −29 kcal mol−1) contain a significant number of Bronsted sites (n = 0.1 mmol g−1), which are located inside the large cages. The sites of intermediary strength (heats around −17 kcal mol−1) are of Lewis and Bronsted types and the weaker sites (heats below −10 kcal mol−1) contain significant hydrogen bonding. The strength of these sites is probably due to mutual interaction between Lewis and Bronsted sites. The accessibility on zeolite and the size of the probe molecules play fundamental role on the determination of acid site distribution. Application of the electrostatic–covalent model (ECW) to this acid provides quantitative parameters for determination of donor-acceptor contributions based on electrostatic (EA) and covalent (CA) intrinsic characters to each chemical bonding. The results demonstrate that zeolite Y has a stronger covalent character with EA = 5.25, CA = 6.89 (CA/EA = 1.31) consistent with softness properties suggested in the literature.