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The green catalytic system (Al2O3/H2O2/ethyl acetate) used in the oxidation of (R)-limonene has many advantages since the reagents have low cost, it is toxicity-free (no heavy metals and no toxic solvents are utilized), and water is the only by-product. The synthesized epoxide may have applications in several industrial segments like adhesives, polymers, resins, and others that require a clean process, especially as a precursor for medical biomaterial applications. An experimental design 23 with 17 assays (6 axial points and central point triplicate) has been carried out for the optimization of the conversion and selectivity towards limonene diepoxide. The assessed variables included the quantities of alumina, limonene, and hydrogen peroxide (70% aq). The analysis of variance (ANOVA) confirmed the validity of the mathematical model obtained with a 90% confidence interval in the studied range. The conversion and selectivity towards limonene diepoxide was >99%, with a reaction time of 10 h, showing the high efficiency of this catalytic system. FTIR, Raman, GC/MS, 1H, 13C, and HSQC NMR techniques confirmed the structure of the synthesized and purified limonene diepoxide.

In the present paper we described the oxidation of 2-butanol as a representative of secondary aliphatic alcohols. The oxidizing system FeCl3-H2O2 was used. A kinetic study of the oxidation reaction has been carried out. Different substituted pyrazines and pyrazoles, namely 2-pyrazinecarboxylic acid (PCA), 5-methyl-2-pyrazinecarboxylic acid (5MPCA), 2-methylpyrazine (2MPZINE), 3-(trifluoromethyl)pyrazole (3TFMPZOLE), 3-methylpyrazole (3MPZOLE) and 1-methylpyrazole (1MPZOLE) were added as cooperating ligands in aqueous solutions. DFT based calculations were also used in order to evaluate the different results obtained. Addition of PCA, 5MPCA and 3TFMPZOLE led to a better reaction performance, while the other ligands led to lower accumulation of products than the reaction without additives. Performed DFT studies suggested that the metal-ligand π-backbonding might be responsible for the reaction activity increase, while ligands more strongly bonded to Fe make it more difficult the access to the metal, leading to lower yields.

Activate carbon (AC) demand has increased worldwide, with application in adsorption, heterogeneous catalysis, and most recently as electrocatalyst support. However, while AC production from agro-industrial waste are widely researched, textile waste is neglected as raw material. In this study, cotton fabric was first applied as textile dye adsorbent after iron impregnation, which enhanced the adsorption capacity. The dye adsorbed fabric was than sequentially pyrolyzed at 800 °C for 2 h under N2 atmosphere, producing a magnetic mesoporous activated carbon (MAC) of 472 m2 g-1 BET surface area with 82% micropores and magnetization saturation of 34.2 emu g-1 deriving from encapsulated metallic αFe. This new simple and fast one-step carbonization, activation and iron incorporation method, has very low chemicals consumption and waste generation compared to the traditionally applied ones. The so produced MAC was loaded with 20 % Pd and tested for electrocatalyst properties: high density current for ethanol oxidation of 549 mA mg-1Pd, 1.37 times higher than using commercial Pd catalyst, lower onset potential of -0.48 V vs NHE. Application of the electrocatalyst for direct ethanol fuel cell achieved a high energy production of 27 mW cm-2 at 353 K.

Xylitol is one of the Top Value-Added chemicals from biomass released by DOE, with no petrochemical alternative. Industrially, this polyol is obtained by catalytic hydrogenation of xylose, a major component of hemicellulose. From xylitol it is possible to obtain various products, such as polyethylene glycol and ethylene glycol, and thus substitute fossil-based raw material. To reduce production costs and make the process environmentally friendly, it is necessary to reduce the stages of chemical conversion of lignocelluloses to xylitol. The present paper discusses the research advances focused on integrating several types of catalytic processes in a single container. The mechanism of catalytic hydrogenation of xylose to xylitol is detailed. The domain of the different parameters of the reaction will allow to increase the efficiency of the transformation of the biomass.

Aluminium oxide and gallium oxide nanorods were identified as highly efficient heterogeneous catalysts for the selective oxidation of aromatic amines to azoxy compounds using hydrogen peroxide as environmentally friendly oxidant. This is the first report of the selective oxidation of aromatic amines to their azoxy derivatives without using transition metal catalysts. Among the tested transition-metal-free oxides, gallium oxide nanorods with small dimensions (9-52 nm length and 3-5 nm width) and fully accessible, high surface area (225 m(2) g(-1)) displayed the best catalytic performance in terms of substrate versatility, activity and azoxybenzene selectivity. Furthermore, the catalyst loading, hydrogen peroxide type (aqueous or anhydrous), and the amount of solvent were tuned to optimise the catalytic performance, which allowed reaching almost full selectivity (98 %) towards azoxybenzene at high aniline conversion (94 %). Reusability tests showed that the gallium oxide nanorod catalyst can be recycled in consecutive runs with complete retention of the original activity and selectivity.

International audience; In the present work, dehydrodieugenol B (1) and its methyl ether (2), isolated from Nectandra leucantha twigs, were used as starting material for the preparation of two new derivatives (1a and 2a) containing an additional methoxycarbonyl unit on allyl side chains. Compounds 1a and 2a demonstrated activity against trypomastigotes (EC(50) values of 13.5 and 23.0 μM, respectively) and against intracellular amastigotes (EC(50) values of 10.2 and 6.1 μM, respectively). Additionally, compound 2a demonstrated no mammalian cytotoxicity up to 200 μM whereas compound 1a exhibited a CC(50) value of 139.8 μM. The mechanism of action studies of compounds 1a and 2a demonstrated a significant depolarization of the plasma membrane potential in trypomastigotes, followed by a mitochondrial membrane potential collapse. Neither calcium level nor reactive oxygen species alterations were observed after a short-time incubation. Considering the potential of compound 2a against T. cruzi and its simple preparation from the natural product 2, isolated from N. leucantha, this compound could be considered a new hit for future drug design studies in Chagas disease.

We report a new, straightforward and inexpensive sol-gel route to prepare boehmite nanorods [gamma-AlO(OH)-NR] with an average length of 23 nm +/- 3 nm, an average diameter of 2 nm +/- 0.3 nm and a high specific surface area of 448 m(2)/g, as evidenced by TEM and N-2-physisorption, respectively. The boehmite was converted to gamma-alumina with preserved nanorod morphology (gamma-Al2O3-NR) and high surface area upon calcination either at 400 or 600 degrees C. These nanostructured materials are active and selective heterogeneous catalysts for the epoxidation of alkenes with the environmentally friendly H2O2. The best catalyst, gamma-Al2O3-NR-400, showed to be versatile in the scope of alkenes that could be converted selectively to their epoxide and displayed enhanced reusability compared to previously reported alumina catalysts. Furthermore, the catalytic performance of the material was enhanced by optimising the reaction conditions such as the solvent and the type of hydrogen peroxide source. Under the optimised reaction conditions, the gamma-Al2O3-NR-400 catalyst displayed 58% cyclooctene oxide yield after 4h of reaction at 80 degrees C with full selectivity towards the epoxide product. The correlation between the catalytic activity of these materials and their physicochemical properties such as surface area, hydrophilicity and number and type of acid sites was critically discussed based on a detailed characterisation study.

In this work, we investigated the use of cotton scraps in natura and modified with iron nitrate,in the adsorption of one of the main water contaminants of the textile industries, the reactive black dye. Special attention was paid to the appropriate destination of the spent adsorbent, in compliance with the precepts of the circular economy. Cotton and polyester are excellent candidates for adsorbents and are produced on a large scale worldwide, but fabric wastes do not yet have a wellestablished method of application. We found that fabrics containing different types of fibers or colors maintain the ability to remove dye. The retention promoted by the cotton fabric in natura reached 18.8 mg g-1. After treatment with iron ions, there was an increase in the dye adsorption capacity to 31.0 mg g-1. In addition, the spent iron-containing adsorbent was pyrolyzed at 973 K, resulting in an activated magnetic carbon with a specific surface area ranging from 300 to 565 m2 g-1. Thus, it was possible to convert the used adsorbent into a new material with wide application possibilities.

International audience; The straightforward functionalization of sterically demanding alpha,alpha-disubstituted double bonds of beta-pinene, (-)-limonene and (-)-limonene terpenoids has been achieved via cross metathesis with internal olefins. The reactions are catalyzed by second generation ruthenium catalysts in dimethyl carbonate as green solvent or under neat conditions. This transformation provides a clean process for the access to functionalized bulky cyclic terpenes where the terminal double bond generates a trisubstituted olefin.

Both the catalytic production of 5-hydroxymethylfurfural (5-HMF) from carbohydrates and the use of a catalyst obtained from residues stand out for adding value to by-products and wastes. These processes contribute to the circular economy. In this work it was evaluated optimized conditions for 5-HMF production from fructose with high yield and selectivity. The reaction was catalyzed by an acidic carbon obtained from glycerol, a byproduct of the biodiesel industry. Special attention has been given to the use of dimethyl sulfoxide (DMSO) as a solvent and its influence on system activity, both in the presence and absence of O2. Glycerol's carbon with acidic properties can be effectively used as catalyst in fructose dehydration, allowed achieving conversions close to 100% with 5-HMF selectivities higher than 90%. The catalyst can be reused in consecutive batch runs. The influence of DMSO in the presence of O2 should be considered in the catalytic activity, as the stabilization of a reaction intermediate by the [O2:DMSO] complex is favored and, both fructose conversion and 5-HMF yield increase.

International audience; The straightforward functionalization of sterically demanding α,α-disubstituted double bonds of the natural products β-pinene and limonene via cross metathesis with symmetrical internal olefins is described. The reaction is catalyzed by Hoveyda-Grubbs type ruthenium catalysts in dimethyl carbonate as green solvent and makes possible the clean introduction of ester and nitrile groups in one step without formation of byproducts.

Acidic carbons were prepared by carbonization and in situ sulfonation of glycerin, a by-product from biodiesel production, and glycerol. The synthetic method used allowed the production of solids containing a large amount of surface functional groups, mainly sulfonic groups. The catalytic performance of the prepared materials was evaluated in reactions typically promoted by acidic catalysts. Conversions as high as 78% for the glycerol acetalization at room temperature and 85% for the glycerol etherification at 393 K were obtained. Furthermore we studied the reaction conditions of fructose dehydration using the prepared materials as catalysts, resulting in milder conditions than those found in the literature for this reaction using carbons as catalysts, with a 5-HMF yield close to 69%.

Biodiesel is one of the most common biofuels, and its production yields a large amount of glycerol as a by-product. It is necessary to develop new technologies for the use of this by-product, adding value to the biodiesel production chain. In this work we investigated glycerol oxidation under mild reaction conditions (air as oxidizing agent and base-free medium) promoted by suitable catalysts. We prepared mono- and bimetallic catalysts of platinum, copper and nickel in the form of nanoparticles by conventional heating and by an alternative method using microwave heating. The nanoparticles were dispersed in activated carbon and tested in glycerol oxidation aiming its valorization into molecules with high added value. Copper and nickel monometallic materials were not active in glycerol oxidation. Platinum monometallic and platinum–copper and platinum–nickel bimetallic materials showed catalytic activity, with platinum–nickel prepared by microwave heating being the most active material in reactions tested. This catalyst presented glycerol conversion of approximately 20% with a turnover number of 9465 in a reaction time of 6 h and 58% of selectivity to glyceric acid, the main product obtained. The best performance of platinum–nickel prepared by microwave heating catalyst was attributed to the probable formation of a metallic alloy between Pt and Ni, as evidenced by the decrease in the lattice parameter for PtNi bimetallic nanoparticles. The results showed that it was possible to obtain an active catalyst in glycerol oxidation reaction under mild conditions via a simple methodology using microwave heating, which demands 94% less time in comparison with conventional heating.

New copper(II) catalytic systems for the mild oxidative C–H functionalization of cycloalkanes and cycloalkenes were developed, which are based on a series of mixed-ligand aminoalcohol-dicarboxylate coordination polymers, namely [Cu2(μ-dmea)2(μ-nda)(H2O)2]n·2nH2O (1), [Cu2(μ-Hmdea)2(μ-nda)]n·2nH2O (2), and [Cu2(μ-Hbdea)2(μ-nda)]n·2nH2O (3) that bear slightly different dicopper(II) aminoalcoholate cores, as well as on a structurally distinct dicopper(II) [Cu2(H4etda)2(μ-nda)]·nda·4H2O (4) derivative [abbreviations: H2nda, 2,6-naphthalenedicarboxylic acid; Hdmea, N,N′-dimethylethanolamine; H2mdea, N-methyldiethanolamine; H2bdea, N-butyldiethanolamine; H4etda, N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine]. Compounds 1–4 act as homogeneous catalysts in the three types of model catalytic reactions that proceed in aqueous acetonitrile medium under mild conditions (50–60°C): (i) the oxidation of cyclohexane by hydrogen peroxide to cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone, (ii) the oxidation of cycloalkenes (cyclohexene, cyclooctene) by hydrogen peroxide to a mixture of different oxidation products, and (iii) the single-pot hydrocarboxylation of cycloalkanes (cyclopentane, cyclohexane, cycloheptane, cyclooctane) by carbon monoxide, water, and a peroxodisulfate oxidant into the corresponding cycloalkanecarboxylic acids. The catalyst and substrate scope as well as some mechanistic features were investigated; the highest catalytic activity of 1–4 was observed in the hydrocarboxylation of cycloalkanes, allowing to achieve up to 50% total product yields (based on substrate).

Hierarchical zeolite possessing MFI framework type was hydrothermally prepared using C22H45 − N+(CH3)2 − C6H12 − N+(CH3)2 − C6H13 as a structure-directing agent in a seed-assisted synthesis method. The nanosponge-like morphology was composed of a three-dimensional disordered network of MFI layers with 2.5 nm thickness supporting each other. Catalytic performance of the MFI nanosponge was investigated in glycerol etherification with tert-butyl alcohol in liquid phase and compared to conventional microporous MFI zeolite and MFI unilamelar nanosheet. The hierarchical zeolites were much more active, which can be attributed to the acid sites located on the external surfaces accessible for the reaction of bulky reactants.

α-Hydroxyacetone (acetol) which is easily produced from glycerol can be oxidized to other products of industrial interest. In this work the acetol oxidation by homogeneous cheap and green catalytic system FeCl3/H2O2 has been studied. Acetonitrile or water was used as solvent. Acetol (0.5 M) gave acetic acid (0.25 M) and formic acid (0.35 M) as the main products. Some amount of CO2 was also detected. For quantification of the CO2 amount, a novel method has been developed which uses GC–MS for monitoring the signals produced by the CO2 and argon (used as internal standard) present in the headspace of the reaction vessel. The formation of 0.028 M CO2 after 4 h under typical conditions was demonstrated. The effects of reactant concentration on the initial reaction rate were studied. The experiments in atmosphere of 16O2 and 16O2 + 18O2 led to the conclusion that molecular oxygen from atmosphere takes part in the reaction and these atoms are incorporated into the products.

Oxidized and sulfonated-activated carbons (AC) were tested in the catalytic conversion of glycerol by acetalization reactions. The solids were treated with concentrated nitric acid and/or fuming sulfuric acid (AC, AC-N, AC-S, and AC-NS). The presence of sulfur and an increase in the acidity of the solids demonstrate the suitability of the oxidation as well as the sulfonation process, especially in the sample treated with concentrated nitric acid and fuming sulfuric acid (AC-NS). The best catalyst for the reaction of glycerol acetalization with phenylacetaldehyde was AC-NS, with a phenylacetaldehyde conversion of 95 % after 90 min at 383 K and selectivity of 88 and 12 %, respectively, to dioxolane and dioxane. These products can be used as hyacinth fragrance flavoring compounds. Furthermore, a contribution of homogeneous catalysis in these systems was not identified. Thus, we identified a possibility of glycerol conversion, a biodiesel by-product, into value-added products by suitable catalysts produced from activated carbons.

International audience; Stimulated by the strong interest in replacing fossil raw materials by renewable feedstocks in chemical industry, alkene metathesis of unsaturated bio-sourced olefins has been recently investigated with the objective of producing high-value molecules using green and atom economic strategies. It is due time to review what has been achieved in this field using terpenes and terpenoids as olefin metathesis partners. These substrates, derived from the isoprene structure, present different types of carbon-carbon double bonds that can be involved in self metathesis, ring closing metathesis, cross metathesis including ethenolysis, and ring opening metathesis. The successful achievements and remaining bottlenecks in this field will be discussed.

The efficient (turnover numbers attained 1200) oxidation of alkanes to the corresponding alkyl hydroperoxides by H2O2 in the presence of catalytic amounts of ferrocene proceeds in MeCN at 40–50 °C. Benzene is oxidized in the same system to phenol. An obligatory component of the catalytic system for both reactions is pyrazine-2-carboxylic acid (PCA) or trifluoroacetic acid (TFA). Kinetic study as well as selectivity parameters testified that the oxidation proceeds with the participation of hydroxyl radicals. In the case of PCA as a co-catalyst the initial rate W0 of the reaction with both cyclohexane and benzene depends quadratically on [Cp2Fe]0 whereas the two reactions in the presence of TFA are of half order in ferrocene. The ferrocene-catalyzed reaction of cyclohexane with H 2 O 2 16 in an atmosphere of labeled 18O2 gave after 2 h a mixture of labeled and unlabeled cyclohexyl hydroperoxide (total yield 20% based on starting cyclohexane) containing up to 69% of 18O (the analysis was after reduction of cyclohexyl hydroperoxide into cyclohexanol with PPh3).

A highly efficient oxidation of limonene with hydrogen peroxide promoted by cheap aluminum oxide has been studied. The reaction is a rare example of the epoxidation promoted by a derivative of non-transition metal having a single stable non-zero oxidation state (SSOS metal), and it affords epoxides which are highly valuable products (fragrances, food additives and monomers). Typically, ethyl acetate at 80°C was used as a solvent. The experimental data have been described by the proposed kinetic scheme. The optimization of the limonene epoxidation using a 2³ experimental design has been carried out.

Sulfonated niobia (HY-340 CBMM) and pillared clay (Fluka) were tested in the catalytic conversion of glycerol by etherification reactions. The solids were treated with concentrated fuming sulfuric acid (AS100 and NS100), and a 30% aqueous solution of this acid (AS30 and NS30). Both the presence of sulfur and the increase in the acidity of the solids demonstrate the suitability of the sulfonation process, especially in samples treated with concentrated fuming sulfuric acid. The best catalyst for the reaction of etherification with tert -butyl alcohol was AS100, with a glycerol conversion of 95% after 5 h at 393 K and yield of 60.3, 33.2 and 5.4%, respectively for mono- tert -butyl-glycerol (MTBG), di- tert -butyl-glycerol (DTBG) and tri- tert -butyl-glycerol (TTBG).

Niobium-aluminum-based catalysts were synthesized by a sol–gel process and successfully applied to the reaction of acetalization of acetone with glycerol yielding 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal) and 2,2-dimethyl-1,3-dioxan-5-ol. The synthesis procedure was developed using high-throughput techniques and the materials prepared with molar ratio1 Metal (1Nb:xAl): 100H2O: 1.5NH4OH (in which x = 1, 0.6, 0.3, 0.1 and 0.05) were selected to be further investigated. The obtained series of mixed oxides displayed high catalytic activity reaching glycerol conversion up to 84%, with 98% of selectivity towards solketal. The physicochemical properties of the investigated catalysts were characterized by N2-adorption/desorption, thermal analysis, X-rays diffraction, FTIR and Raman spectroscopy, and by adsorption of pyridine monitored by FT-IR spectroscopy and TGA. The catalysts are truly heterogeneous and can be reused in consecutive runs without loss of activity.

New hexanuclear nickel(II) silsesquioxane [(PhSiO1.5)12(NiO)6(NaCl)] (1) was synthesized as its dioxane-benzonitrile-water complex (PhSiO1,5)12(NiO)6(NaCl)(C4H8O2)13(PhCN)2(H2O)2 and studied by X-ray and topological analysis. The compound exhibits cylinder-like type of molecular architecture and represents very rare case of polyhedral complexation of metallasilsesquioxane with benzonitrile. Complex 1 exhibited catalytic activity in activation of such small molecules as light alkanes and alcohols. Namely, oxidation of alcohols with tert-butylhydroperoxide and alkanes with meta-chloroperoxybenzoic acid. The oxidation of methylcyclohexane gave rise to the isomeric ketones and unusual distribution of alcohol isomers.

Methyl oleate can be efficiently (yield and selectivity attain 100%, turnover number is up to 2000) epoxidized with hydrogen peroxide in acetonitrile solution at 25 °C using the combination “[Mn 2 L 2 O 3 ](PF 6 ) 2 (L = 1,4,7-trimethyl-1,4,7-triazacyclononane)/oxalic acid” as a catalyst. Kinetic features of the reaction were studied and the conclusion has been made that high-valent oxo-manganese rather than hydroxyl radicals is a crucial oxidizing species in this process.

Catalysts of Pt/ x %Nb 2 O 5 /Al 2 O 3 (where x = 0, 1, 5, 10, 20 or 100) + Amberlyst 15 were evaluated through the reaction of glycerol hydrogenolysis in a batch system at 413 K and 50 bar of H 2 , with the aim of producing 1,2-propanediol. The supports were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), scanning electron microscopy (SEM) and nitrogen adsorption (surface area – BET and pore size and volume – BJH). Niobia is present as islands on alumina surface, which reduces the interaction between these oxides and favors the creation of Bronsted acidic sites, so that the observed behavior is similar to pure niobia. All systems showed a high yield and selectivity for the production of 1,2-propanediol. The presence of niobia as a support leads to a highly active and selective catalyst for 1,2-propanediol production. The change in the behavior of the active metal can be related to the SMSI effect, inherent to systems containing niobia as support.

The homogeneous catalytic system composed of the aqua-soluble tetracopper(II) triethanolaminate complex [ O ⊂ Cu 4 { N ( CH 2 CH 2 O ) 3 } 4 ( BOH ) 4 ] [ BF 4 ] 2 (1), t-BuOOH (TBHP), water and acetonitrile solvent (optional) has been applied for the mild oxidation of (i) linear and cyclic alkanes to the corresponding alkyl peroxides, alcohols and ketones, (ii) secondary or primary alcohols to ketones or aldehydes, respectively and (iii) glycerol (GLY) to dihydroxyacetone (DHA). Unusual regio-, bond and stereoselectivity parameters have been determined for the alkane oxygenations and discussed in terms of possible steric, hydrophobic and electronic effects. In alcohol oxidations, secondary alcohols are the most reactive substrates. Yields and TONs up to 82% and 1200, respectively, have been obtained in the oxidation of isopropanol to acetone. The selective oxidation of GLY to DHA by the 1/TBHP system has been also achieved, although providing lower conversions. The 1/H2O2 system for the GLY oxidation is particularly advantageous in terms of selectivity and oxidant efficiency. These systems constitute one of the first examples of a metal-catalyzed oxidation of glycerol under homogeneous conditions.

Mesoporous titanium-silicate Ti-MMM-2 catalyzes oxidation of alkanes (cyclooctane, n-heptane, n-octane, isooctane, methylcyclohexane, cis- and trans-1,2-dimethylcyclohexane) and olefins (cyclooctene, 1-decene, (S)-limonene) by H2O2 in acetonitrile solution at 60 °C. The catalytic reaction is truly heterogeneous in nature. The oxidation occurs via the formation of a ‘Ti–OOH’ species on the catalyst surface which either epoxidizes a nucleophilic double bond or generates, after O–O bond splitting, hydroxyl radical. The HO radical attacks an alkane or olefin C–H bond producing alkyl radical. The reaction R + O2 → ROO leads to the formation of alkyl hydroperoxide as the main product of the alkane oxidation. In the case of alkenes this reaction leads to allylic oxidation products. The composition of products of the olefin oxygenation (the epoxide/alkyl hydroperoxide or epoxide/diol ratios, etc.) strongly depends on the nature of the substrate. In the oxidation of (S)-limonene, isomeric diepoxides are formed along with monoepoxides even at the early stage of the reaction and (SRR)-diepoxide predominates among other products. This can be rationalized by suggesting the epoxidation of the two double bonds to occur simultaneously on two adjacent ‘Ti–O–OH’ centers on the catalyst surface.

Environmentally friendly acid carbon (CG) catalysts, containing a high amount of sulfonated and oxygenated groups, were prepared from glycerin, a biodiesel waste. CGs were produced by glycerin carbonization in the presence of H2SO4 at 1:3 m:m ratio in a closed autoclave at 180oC for different times: 0.25; 1; 3 and 6 hours (CG-0.25h; CG-1h; CG-3h and CG-6h, respectively). The catalyst properties for all carbons were evaluated in the glycerol etherification reaction with tert-butyl alcohol (TBA). The yield for mono-tert-butyl glycerol (MTBG), di-tert-butyl glycerol (DTBG) and tri-tert-butyl-glycerol (TTBG) was high and very similar for all CGs, of about 43% and 20% for the MTBG and DTBG + TTBG, respectively. Furthermore, the activity of these catalysts were close to those obtained using a commercial resin, Amberlyst-15, of about 50% and 27% for MTBG and DTBG + TTBG, respectively.

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 adsorption capacities of commercial and Brazilian natural clays were evaluated to test their applications in wastewater control. We investigated the process of sorption of manganese(II) and cadmium(II) present in synthetic aqueous effluents, by calculating the adsorption isotherms at 298 K using batch experiments. The influence of temperature and pH on the adsorption process was also studied. Adsorption of metals was best described by a Langmuir isotherm, with values of Q 0 parameter, which is related to the sorption capacity, corresponding to 6.3 mg g− 1 for K-10/Cd(II), 4.8 mg g− 1 for K-10/Mn(II), 11.2 mg g− 1 for NT-25/Cd(II) and 6.0 mg g− 1 for NT-25/Mn(II). We observed two distinct adsorption mechanisms that may influence adsorption. At the first 5 min of interaction, a cation exchange mechanism that takes place at exchange sites located on (001) basal planes is predominant. This process is inhibited by low pH values. After this first and fast step, a second sorption mechanism can be related to formation of inner-sphere surface complexes, which is formed at edges of the clay. The rate constants and the initial sorption rates correlate positively with temperature in all studied systems, denoting the predominance of a physisorption process. The addition of complexing agents that are incorporated within the K10 structure, enhance metal uptake by the adsorbent. The results have shown that both Cd(II) and Mn(II) were totally retained from a 50 mg L− 1 solution when K10 grafted with ammonium pyrrolidinedithiocarbamate (APDC) was used as adsorbent.

Oxidation of alkanes with hydrogen peroxide in water solution at 10–50 � C is efficiently catalyzed by the cationic dinuclear manganese (IV) derivative [Mn2L2O3] 2+ (1, with L = 1,4,7-trimethyl-1,4,7-triazacyclononane, TMTACN) in the form of the hexafluorophosphate salt ([1][PF6]2) if oxalic acid is present as a co-catalyst. Methane gives methanol and formaldehyde (turnover numbers, TONs, were 7 and 2, respectively, after reduction of the reaction mixture with ascorbic acid) whereas cyclohexane was oxidized with TONs up to 160 affording cyclohexyl hydroperoxide, cyclohexanone and cyclohexanol (the ketone was the main product, although at room temperature almost pure alkyl hydroperoxide was formed). In contrast to the oxidation in acetonitrile, the reaction with linear n-alkanes in water exhibits an unusual distribution of oxygenates. For example, in the oxidation of n-heptane the normalized reactivity of the methylene group in position 4 of the chain is 3–7 times higher than that of the CH2 group in position 2. Dec-1-ene is epoxidized by hydrogen peroxide in water (a biphasic system) catalyzed by [1][PF6]2 and oxalic acid in the presence of a small amount of acetonitrile with TONs up to 1000 (no epoxidation has been detected in the absence of MeCN). � 2005 Elsevier B.V. All rights reserved.

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

Tetradentate amine N,N′-bis(2-pyridylmethylene)-1,4-diaminodiphenyl ether (compound 1) dramatically accelerates the oxidation of alkanes with MCPBA in acetonitrile catalyzed by FeCl3, whereas N,N′-bis(2-pyrrolidinmethylene)-1,4-diaminodiphenyl ether (2) does not affect the reaction. The selectivity of the reaction in the presence of 1 is noticeably higher than that in its absence. On the basis of the kinetic study and selectivity parameters a mechanism has been proposed which includes the formation of a complex between a molecule of MCPBA and coordinated to ligand 1 iron ion. This complex decomposes to produce a Fe(II) derivative which is further oxidized by MCPBA to generate a (1•Fe=O)4+ species reacting with both alkane and acetonitrile. Finally, alkyl hydroperoxide is formed which partially decomposes to produce more stable corresponding alcohol and ketone (aldehyde).

Environmentally friendly sulfonated black carbon (BC) catalysts were prepared from biodiesel waste, glycerol. These black carbons (BCs) contain a high amount of acidic groups, mainly sulfonated and oxygenated groups. Furthermore, these catalysts show a high catalytic activity in the glycerol etherification reaction with tert-butyl alcohol, the activity being larger for the sample prepared with a higher glycerol:sulfuric acid ratio (1:3). The yield for mono-tert-butyl glycerol (MTBG), di-tert-butyl glycerol (DTBG) and tri-tert-butyl-glycerol (TTBG) were very similar to those obtained using a commercial resin, Amberlyst-15. Furthermore, experimental results show that the carbon with the lowest acidic surface group content, BC prepared in minor glycerol:sulfuric acid ratio (10:1), can be chemically treated after carbonization to achieve an improved catalytic activity. The activity of all BCs is high and very similar, about 50% and 20% for the MTBG and DTBG + TTBG, respectively. This work was supported by FAPESP-Brazil (Project number 2011/22264-4, 2011/14626-3).

Inexpensive Al 2 O 3 can be used as a simple catalyst for alkene epoxidation, using anhydrous hydrogen peroxide as oxidant. This system is active and selective in the epoxidation of several alkenes. Besides the epoxidation of the terpenes limonene and α-pinene, we studied the epoxidation of cyclohexene and cyclooctene, as well as α-olefins, such as 1-octene and 1-decene. Productivities of up to 4.3 g products per gram catalyst were obtained and the catalyst was recycled without significant loss of activity.

Many efforts have been made to develop new catalysts to oxidize cyclohexane under mild conditions. Herein, we review the most interesting systems for this process with different oxidants such as hydrogen peroxide, tert -butyl hydroperoxide and molecular oxygen. Using H 2 O 2 , Na-GeX has been shown to be a most stable and active catalyst. Mesoporous TS-1 and Ti-MCM-41 are also stable, but the use of other metals such as Cr, V, Fe and Mo leads to leaching of the metal. Homogeneous systems based on binuclear manganese(IV) complexes have also been shown to be interesting. When t -BuOOH is used, the active systems are those phthalocyanines based on Ru, Co and Cu and polyoxometalates of dinuclear ruthenium and palladium. Microporous metallosilicates containing different transition metals showed leaching of the metal during the reactions. Molecular oxygen can be used directly as an oxidant and decreases the leaching of active species in comparison to hydrogen peroxide and tert -butyl hydroperoxide. Metal aluminophosphates (metal: Mn, Fe, Co, Cu, Cr V) are active and relatively stable under such conditions. Mn-AlPO-36 yields directly adipic acid, but large amounts of carboxylic acids should be avoided, as they cause metal leaching from the catalysts. Rare earth exchanged zeolite Y also shows good selectivity and activity. In the last part of the review, novel alternative strategies for the production of cyclohexanol and cyclohexanone and the direct synthesis of adipic acid are discussed.

Rhenium oxides supported on zeolite Y, mixed silica–alumina and pure alumina were prepared by impregnation of the supports with Re 2 O 7 or NH 4 ReO 4 . The materials are active catalysts in the epoxidation of cyclooctene and cyclohexene with anhydrous H 2 O 2 in EtOAc. Catalyst stabilities with regard to metal leaching are closely correlated with the alumina content of the support and almost no leaching was observed with ReO 4 − supported on pure alumina. Stable catalysts ReO 4 –Al 2 O 3 with ReO 4 − contents up to 12 wt.% can be prepared. Higher contents result in extensive metal leaching and catalysis in the homogeneous phase. The catalyst ReO 4 (12 wt.%)–Al 2 O 3 was re-used in three catalytic runs, without loss of activity. Selectivities for cyclooctene epoxide were around 96%, whereas cyclohexanediol was obtained as the only product in cyclohexene epoxidation. Adding pyridine to the reaction mixtures, the selectivity for cyclohexene epoxide increased from 0 to 67%, however, a significant decrease in conversion was observed.

Microporous metallosilicates containing various transition metals have been prepared by the acid-catalyzed sol–gel process. The catalytic activity of the materials has been tested for the epoxidation of cyclooctene with tert -butyl hydroperoxide. Silicates containing molybdenum showed high activities and epoxide selectivities. The catalytic activities of catalysts prepared with molybdenyl acetylacetonate as metal precursor are mainly due to metal leached into the homogeneous phase. A catalyst for the heterogeneous phase epoxidation was obtained, using Mo(V)isopropoxide as metal precursor. This catalyst was tested in the epoxidation of various alkenes and conversions increase in the order 1-decene≈α-pinene 2 -physisorption, UV–VIS and FTIR spectroscopy.

Impregnation of SiO2.Al2O3 (24.3% Al2O3 with 6% B2O3 increases the activity of supported Re2O7 in the ethenolysis of methyl oleate, but reduces the activity of CH3ReO3 on the same support. Re2O7/SiO2.Al2O3/B2O3-SnBu4 is shown to be an effective catalyst for the ethenolysis of methyl linoleate and of the methyl esters of olive oil, and can be recycled after calcination at least five times without loss of activity.

In esterification of oleic acid with methanol at 25 °C HPA displayed the highest activity. Moreover the HPA could be reused after being transformed into its cesium salt. In the reaction of etherification of glycerol HPA and Amberlyst 35W showed similar initial activity levels. The results of acid properties demonstrate that HPA is a strong protonic acid and that both surface and bulk protons contribute to the acidity. Because of its strong affinity for polar compounds, HPA is also seemingly dissolved in both oleic acid and methanol. The reaction in this case proceeds with the catalyst in the homogenous phase.