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As low‐temperature conditions (e.g. in space) prohibit reactions requiring large activation energies, an alternative mechanism for follow‐up transformations of highly stable molecules involves the reactions of higher energy isomers that were generated in a different environment. Hence, one working model for the formation of larger organic molecules is their generation from high‐lying isomers of otherwise rather stable molecules. As an example, we present here the synthesis as well as IR and UV/Vis spectroscopic identification of the previously elusive 1,1,2‐ethenetriol, the higher energy enol tautomer of glycolic acid, a rather stable and hence unreactive biological building block. The title compound was generated in the gas phase by flash vacuum pyrolysis of tartronic acid at 400 °C and was subsequently trapped in argon matrices at 10 K. The spectral assignments are supported by B3LYP/6–311++G(2d,2p) computations. Upon photolysis at λ=180–254 nm, 1,1,2‐ethenetriol rearranges to glycolic acid and ketene., The simple yet uncharacterized high energy tautomer of glycolic acid, namely 1,1,2‐ethenetriol, an important molecule in the abiotic synthesis of sugar acids, has now been identified by IR and UV/Vis spectroscopy. With these data now in hand, it now awaits its identification in space as another building block for prebiotic chemistry.

Manganese nodules from ocean bed are potential resources of Cu, Ni, and Co for which land-based deposits are scarce in India. The present work describes a novel approach of using glycerol, a nontoxic biomass-derived reductant, for the reductive acid leaching of manganese nodules. Parameters such as acid concentration, time, temperature, and pulp density were optimized for leaching. The optimal leaching conditions were found to be 10% (w/v) pulp density and 10% (v/v) H2SO4 at 80 °C with 1% (v/v) glycerol yielding >95% of Ni and >98% Cu, Co, and Mn extraction within an hour. Kinetic analysis of the data based on the initial rate method showed that the leaching process was chemical reaction-controlled with an apparent activation energy of 55.47 kJ/mol. Various oxidation intermediates of glycerol formed during leaching were identified using mass spectrometry and Raman spectroscopy, and a probable oxidation pathway of glycerol during the leaching process has been elucidated based on the analysis. Glycerol was oxidized to glyceraldehyde, glyceric acid, tartronic acid, dihydroxyacetone, hydroxy pyruvic acid, glyoxalic acid, oxalic acid, and finally converted to CO2 during leaching. The fast reaction kinetics, near-complete dissolution of manganese, and other associated metals in the nodule can be attributed to the participation of all intermediate products of glycerol oxidation in redox reactions with MnO2, enhancing the overall reduction leaching efficiency.

Glycerol electro-oxidation offers a green route to produce the high value added chemicals. Here in, we report the glycerol electro-oxidation over a series of multi walled carbon nano tubes supported monometallic (Pt/CNT and Pd/CNT) and bimetallic (Pt-Pd/CNT) catalysts in alkaline medium. The cyclic voltammetry, linear sweep voltammetry and chronoamperometry measurements were used to evaluate the activity and stability of the catalysts. The Pt-Pd/CNT electrocatalyst exhibited the highest activity in terms of higher current density (129.25 A/m2) and electrochemical surface area (382 m2/g). The glycerol electro-oxidation products formed at a potential of 0.013 V were analyzed systematically by high performance liquid chromatography. Overall, six compounds were found including mesoxalic acid, 1,3-dihydroxyacetone, glyceraldehyde, glyceric acid, tartronic acid and oxalic acid. A highest mesoxalic acid selectivity of 86.42% was obtained for Pt-Pd/CNT catalyst while a maximum tartronic acid selectivity of 50.17% and 46.02% was achieved for Pd/CNT and Pt/CNT respectively. It was found that the introduction of Pd into Pt/CNT lattice facilitated the formation of C3 products in terms of maximum selectivity achieved (86.42%) while the monometallic catalysts (Pd/CNT and Pt/CNT) showed a poor performance in comparison to their counterpart.

Glycerol (C3H8O3), a waste product of bio‐diesel, is considered as a suitable substrate for electro‐oxidation process to generate high value added products. In this work, palladium nanoparticles supported over activated MWCNTs with loadings of 5%‐40% were prepared using chemical reduction method and further employed to explore their potential for electro‐oxidation of glycerol to produce various high‐value‐compounds. The catalysts were characterized by physiochemical methods, such as X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller (BET), and Transmission electron microscopy, while the electro‐oxidation activity of the catalysts was analysed using cyclic voltammetry (CV) and chronoamperometry (CA), and the products were identified by high performance liquid chromatography (HPLC). The electrochemical surface area (SESA) and mass activity (MA) were increased from 176.98 m2 g‐1 to 282.29 m2 g‐1 and 12.22 mA/mg to 49.53 mA/mg by increasing the Pd‐loading from 5% to 20%, respectively. While the further increase to 40% Pd loading, the SESA and MA values decreased to 231.45 m2 g‐1 and 47.63 mA/mg respectively. The results found that the optimum 20% Pd‐loading showed the excellent electrochemical properties due to exceptional distribution of Pd‐metal particles over MWCNTs. HPLC analysis showed the tartronic acid, glyceric acid and glyceraldehyde as dominant products. Mechanism of the reaction has also been proposed based on product distribution.

Production of biodiesel is a renewable and pollution free source but it increases co-product i.e. crude glycerol. This paper demonstrates applications of the side product in an efficient and cost effective manner. The crude glycerol hence produced can be utilized in varied industries and can be used as precursor for the production of various products having better economic significance. The majority of crude glycerol is used as feedstock for production of other value-added chemicals. The utilization of glycerol in production of Glycerol trinitrate, Tartronic acid and Glyceric acid has been reported successfully.

High-performance electrocatalysts with excellent activity and selectivity hold the key to the electrochemical conversion of glycerol. Herein, well-defined bimetallic Au@Ag and trimetallic PdAu@Ag core-shelled nanoparticles were fabricated using a seed-mediated growth process and further examined as electrocatalysts for glycerol oxidation in both alkaline and acidic solutions. The activity of the catalysts was evaluated via cyclic voltammetry, linear sweep voltammetry and chronoamperometric measurements. The Au@Ag and PdAu@Ag nanoparticles are highly active in alkaline solutions, but inactive in acidic solutions. In alkaline solutions, the PdAu@Ag and Au@Ag nanoparticles show current densities of 3.94 and 2.57 mA cm−2, which are 4.3 and 25.7 times those of the commercial Pd/C and Au/C catalysts, respectively. The products of glycerol electro-oxidation were analyzed by high performance liquid chromatography (HPLC). Three major products, namely dihydroxyacetone (DHA), glyceric acid, glyceraldehyde and five minor products including oxalate acid, tartronic acid, formic acid, glycolic acid (GA) and glyoxylic acid were detected. Notably, a remarkable DHA selectivity of 70.1% was obtained from the PdAu@Ag catalyst at 0.9 V. The Au@Ag yields the largest GA selectivity of 31.6% at 1.1 V. The PdAu@Ag tends to yield more C3 products at high applied potentials.

A series of platinum–palladium–silver nanoparticles with tunable structures were synthesized for glycerol electro-oxidation in both alkaline and acidic solutions. Electrochemical results indicate that the catalysts show superior activity in alkaline solutions relative to acidic solutions. In alkaline solutions, the peak current densities of ammonia-etched samples are approximately twice those of saturated-NaCl-etched samples. Ammonia-etched platinum–palladium–silver (PtPd@Ag-NH3) exhibits a peak current density of 9.16 mA cm−2, which is 18.7 and 10 times those of the Pt/C and Pd/C, respectively. The product distribution was analyzed by high performance liquid chromatography. Seven products including oxalic acid, tartronic acid, glyoxylic acid, glyceric acid (GLA), glyceraldehyde (GALD), glycolic acid, and dihydroxyacetone (DHA) were detected. The NH3·H2O etched samples tend to generate more GALD, while the NaCl etched samples have a great potential to produce DHA. The addition of Pd atoms can facilitate glycerol oxidation pathway towards the direction of GALD generation. The Pt@Ag-NaCl possesses the largest DHA selectivity of 79.09% at 1.3 V, while the Pt@Ag-NH3 exhibits the largest GLA selectivity of 45.01% at 0.5 V. The PtPd@Ag-NH3 exhibits the largest C3/C2 ratio of 17.45. The selectivity and product distribution of glycerol electro-oxidation can be tuned by engineering the surface atoms of the as-synthesized catalysts.

In this work, glycerol valorization into tartronic acid – one of the most valuable derivatives of glycerol – was reported over platinum supported on multi-walled carbon nanotubes (Pt/CNT) electroca...

Isoprothiolane (IPT) was one of the most commonly used pesticides around the world. It was reported to be the highest concentration and frequency of detection of 13 most commonly used pesticides in Mekong Delta recently. The oxidation degradation kinetic of ozone and chlorine with IPT and the identification of the degradation products was investigated in this research. The results showed that both ozone and chlorine oxidized IPT rapidly under typical water treatment condition, and that both reactions followed second order reaction kinetics. The ozone reaction rates exhibited no pH dependence with the rate constant of 247.1 (±11.0) M−1s−1 at 25 °C, whereas chlorine reaction rates increased dramatically with decreasing pH. The rate constant for hypochloric acid was 73.3 (±3.1) M−1s−1 at 25 °C, while the reaction of hypochlorite was negligible. The degradation products by chlorine and ozone were identified by LC-MS/MS and the reaction pathways were proposed. The thioether and the carbon-carbon double bond in IPT were the reactive sites during chlorine and ozone oxidation. The thioether group was oxidized into sulfoxide and further sulfone group, and the carbon-carbon double bone were cleaved to form diisopropyl ester of malonic acid, diisopropyl ester of tartronic acid and diisopropyl ester of ketomalonic acid monohydrate. Compared to ozone reaction, it was more complicated for chlorine reaction, which yielded chlorine substituted, hydroxylated and dithiolane ring-opening products.

Catalytic transformation of glycerol to value-added products has attracted the attention of scientists all over the world. Among various transformations, selective oxidation of glycerol with molecular oxygen to dihydroxyacetone, glyceric acid, glyceraldehydes, and tartronic acid is challenging both from the viewpoint of academic research and industrial application. Herein, we review the recent progresses in the selective oxidation of glycerol under base-free conditions. Those catalysts widely reported for the selective oxidation of the terminal hydroxyl and secondary hydroxyl groups in glycerol, such as monometallic Au, Pt, and Pd NPs, and bimetallic Au-Pt, Au-Pd, Pt-Bi, Pt-Sb, and Pt-Cu, were compared and discussed in detail. The reaction mechanism over Pt-based catalysts, possible catalyst deactivation, and the corresponding improvements are presented. Further, the recent progresses in the continuous oxidation of glycerol in fixed bed reactors and its excellent selectivity in the formation of dihydroxyacetone are highlighted.

International audience; In this work, we highlight the feasibility of new efficient catalytic processes by laser excitation, exemplified in the reaction of oxidation of glycerol over catalysts based on supported gold nanoparticles. We show that this catalytic oxidation reaction can efficiently proceed via laser excitation of surface plasmon resonance of gold nanoparticles, inducing local thermal heating effect. While the reaction did not occur in the absence of any external heat source, with this original approach, 88% of glycerol was converted after 2 h, leading to the formation of glyceric acid and tartronic acid as main products. The photonic activation led to 2.5 times more efficient conversion than an equivalent thermal activation by conventional heating source. Investigations of the laser power and the nature of support catalyst revealed a significant contribution of electron transfer from plasmonic nanoparticles to TiO² in the oxidation reaction.

2 Schemes, 3 Tables, 5 Figures., A high surface area mesoporous TiO2 material (110 m2/g) was synthesised using a nanocasting methodology, utilizing SBA‐15 as a hard template. This material was subsequently used as a support to prepare a series of 1 wt.% AuPt/TiO2 catalysts, synthesised by conventional impregnation and sol‐immobilisation. Catalysts were tested for the oxidation of glycerol to lactic acid and their performance was compared with corresponding catalysts supported on TiO2−P25, TiO2‐anatase and TiO2‐rutile. Higher rates of reaction and higher selectivity to lactic acid were observed over nanocast TiO2 supported catalysts. The increased performance of these catalysts was attributed to the presence of Si on the surface of the support, which likely arose from inefficient etching of the SBA‐15 template. The presence of Si in these catalysts was confirmed by X‐ray photoelectron spectroscopy and electron energy loss spectroscopy. It was proposed that the residual Si present increases the Brønsted acidity of the TiO2 support, which can lead to the formation of Lewis acid sites under reaction conditions; both sites are known to catalyse the dehydration of a primary alcohol in glycerol. Typically, under alkaline conditions, lactic acid is formed by the nucleophilic abstraction of a hydrogen. Thus, we propose that the improved selectivity to lactic acid over the nanocast TiO2 supported catalyst is attributed to the co‐operation of heterogeneous and homogeneous dehydration reactions, as both compete directly with a direct oxidation pathway, which leads to the formation of oxidation products such as glyceric and tartronic acid., T. García would like to acknowledge the Spanish MICINN through its Mobility program for stays of senior researchers and professors in foreign countries (grant number PRX18/00474) for funding. O.S.P acknowledges the FPI fellowship (BES-2016-077750) funded by Spanish MINECO. B.S. also thank MINECO (MAT2017-84118-C2-1-R project) for funding. We would also like to thank the Cardiff University TEM facility for the TEM and FEG-SEM electron microscopy data acquired and Diamond Light Source for access and support in use of the electron Physical Science Imaging Centre (Instrument E01 and proposal number MG21641 and MG22766) which contributed to the results presented here.

Here, we report the development of catalysts comprising highly dispersed Au on an alumina (Al2O3) support for the oxidation of glycerol to high-value carboxylic acids in a liquid-phase flow reactor. The catalysts were prepared by means of a deposition–precipitation method. To ensure that the catalysts could be used for long-term catalytic conversions in a liquid-phase flow reactor, we chose an alumina support with high temperature stability and a particle size (50–200 μm) large enough to prevent leakage of the catalyst from the reactor. One of the five catalysts had a high catalytic activity for the conversion of glycerol to the high-value carboxylic acids, glyceric acid and tartronic acid (conversion of glycerol >70%), and the catalyst retained its catalytic activity over long-term use (up to 1770 min). Pretreatment of the catalyst with fructose, a mild reductant, increased the activity of the catalyst. Scanning transmission electron microscopy revealed three Au species highly dispersed on the surface of the alumina support—Au nanoparticles (mode = 7.5–10 nm), Au clusters (1–2 nm), and atomic Au.

Rational control of catalytic selectivity still remains a grand challenge in the field of biomass conversion to value-added chemicals. In this paper, we used PtFe catalyst as an example to understand fundamentals for lattice strain, electronic reconfiguration, reaction kinetics and catalytic selectivity for aqueous conversion biopolyols. Structurally strained face centered tetragonal (fct) PtFe crystals were synthesized and it was confirmed that such unique PtFe nanostructures display intriguing electronic coupling effect and partial charge distribution, as revealed by surface characterization using TEM, XRD and XPS, as well as DFT calculation. Bimetallic PtFe-fct catalysts exhibit a remarkable catalytic activity (TOF: 24 312 h–1 at 65 °C and 1 MPa O2), enhanced selectivity (tartronic acid: 54%) and improved stability for aqueous phase oxidation of biopolyols, in comparison with conventional fcc morphology. Kinetic modeling further indicates that relatively lower oxidation barrier and restrained decarboxy...

This work focuses on the systematic study of porous anodic alumina films grown in novel moderately concentrated tartronic (2-hydroxymalonic) acid electrolyte. The morphological analysis enabled us to reveal new details of the alumina pore formation mechanism and to discover the processes responsible for such frequently occurring defects as branched pores and multiple pore openings within a single cell. The qualitatively new model developed herein explains satellite nanochannel formation from a colloidal electroconvection standpoint—namely, by the temporary change of the existing nanoconvective flows, which give rise to the cooperative cell pattern in porous alumina, from laminar to turbulent mode (such flow regimes are generally termed “transitional” or in some recent literature also “laminar unstable”). Our theoretical discussion demonstrates that the morphological parameters of self-organized layers are strongly related to such properties of the liquid phase as the dielectric constant and the Debye leng...

Phase transformation in anisotropic nanocrystals is critical for enhanced surface properties of bimetallic catalysts. In this work, we report a series of phase transformed PtFe nanocomposites as catalysts for facile oxidation of glycerol to value-added tartronic acid at mild operating conditions. The lattice mismatch between Pt and Fe intrinsically drives structure reconstruction from face centered cubic (fcc) to ordered and lattice distorted face centered tetragonal (fct) phase. Surface characterization reveals that there exists an interdiffusion of Pt and Fe during phase transformation and a downward shift of binding energy for Pt species. Such transformation induces the formation of strained PtFe nanocomposites and enhanced structural coherence leading to 3-fold enhancement in catalytic activity for one-pot glycerol oxidation to tartronic acid compared with the fcc structure.

A screening study of the chromatographic separation of Glyceric Acid (GCA) and Tartronic Acid (TTA) was performed using three different polystyrene-divinylbenzene ion-exchange resins in hydrogen form (Dowex® 50WX-8, Dowex® 50WX-4, Dowex® 50WX-2). The experiments were described by the axial dispersion flow model with the LDF approximation incorporated into the software gPROMS. From the three investigated adsorbents differing by the crosslinking, Dowex® 50WX-2 has presented the higher adsorption capacity, as well as the highest bed efficiency expressed by the number of theoretical plates. The adsorption equilibrium constants were determined from single breakthrough experiments, and a very good agreement between experimental and simulated data was achieved for both single components and binary mixtures. Therefore, the fundamental data determined within this work represents a key contribution to the design of continuous chromatographic processes for the purification of GCA and TTA.

International audience; Glycerol is a by-product produced from biodiesel, fatty acid, soap and bioethanol industries. Today, the value of glycerol is decreasing in the global market due to glycerol surplus, which primarily resulted from the speedy expansion of biodiesel producers around the world. Numerous studies have proposed ways of managing and treating glycerol, as well as converting it into value-added compounds. The electrochemical conversion method is preferred for this transformation due to its simplicity and hence, it is discussed in detail. Additionally, the factors that could affect the process mechanisms and products distribution in the electrochemical process, including electrodes materials, pH of electrolyte, applied potential, current density, temperature and additives are also thoroughly explained. Value-added compounds that can be produced from the electrochemical conversion of glycerol include glyceraldehyde, dihydroxyacetone, glycolic acid, glyceric acid, lactic acid, 1,2-propanediol, 1,3-propanediol, tartronic acid and mesoxalic acid. These compounds are found to have broad applications in cosmetics, pharmaceutical, food and polymer industries are also described. This review will be devoted to a comprehensive overview of the current scenario in the glycerol electrochemical conversion, the factors affecting the mechanism pathways, reaction rates, product selectivity and yield. Possible outcomes obtained from the process and their benefits to the industries are discussed. The utilization of solid acid catalysts as additives for future studies is also suggested.

© 2020 by the authors., Gold nanoparticles supported on various oxides (CeO2, CeO2/TiO2, MgO, MgO/TiO2, La2O3, La2O3/TiO2) (with 4 wt.% Au loading) were investigated in the liquid (aqueous) phase oxidation of glycerol by molecular oxygen under mild conditions, in the presence of alkaline earth (CaO, SrO and MgO) or alkaline (NaOH) bases. Full conversion and selectivity between 38 and 68% to sodium glycerate were observed on different Au supported catalysts (Au/MgO/TiO2, Au/La2O3/TiO2, Au/CeO2 and Au/CeO2/TiO2). The combined effect of Au particle size and basicity of the support was suggested as the determining factor of the activity. Agglomeration of gold nanoparticles, found after the reaction, led to the deactivation of the catalysts, which prevents the further oxidation of sodium glycerate into sodium tartronate. Promising results were obtained with the use of alkaline earth bases (CaO, SrO, MgO), leading to the formation of free carboxylic acids instead of salts, which are formed in the presence of the more usual base, NaOH., This work was partially supported by the Associate Laboratory for Green Chemistry (LAQV), financed by national funds from FCT/MCTES (UIDB/50006/2020) (Portugal), the Tomsk Polytechnic University Competitiveness Enhancement Program project VIU-RSCBMT-197/2020, and the Russian Foundation of Basic Research, project 18-29-24037.

International audience; Glycerol valorization through partial oxidation is a good way of obtaining many different molecules with high added value such as glyceric acid, tartronic acid, dihydroxyacetone, etc. Among the potential products, glyceraldehyde is an interesting chemical compound for its various applications in different domains such as organic chemistry, medical, and cosmetic industries. In the present paper, we studied the effect of different supports on the glycerol oxidation reaction in a batch reactor applying base-free conditions. The tested catalysts were Pt-based materials deposited on various supports (i.e., SiO2, TiO2, ZSM-5, γ-Al2O3), which were synthesized using a deposition method followed by a chemical reduction. The catalysts were extensively characterized (BET, ICP, XRD, TEM, XPS), highlighting differences in terms of specific surface areas, textural properties, and Pt nanoparticles sizes. We evidenced a direct relation between glycerol conversion and glyceraldehyde selectivity (i.e., an increase in glycerol conversion leads to a decrease in glyceraldehyde selectivity). The Pt/γ-Al2O3 catalysts exhibited the highest activity, but their selectivity to glyceraldehyde significantly decreased with time on stream. Pt/SiO2 presented the highest selectivity to glyceraldehyde owing to a slower reaction rate, which allows envisioning technical opportunities to continuously extract the formed glyceraldehyde from the mixture.

Over the past decades, research efforts are being devoted into utilizing the biomass waste as a major source of green energy to maintain the economic, environmental, and social sustainability. Specifically, there is an emerging consensus on the significance of glycerol (an underutilised waste from biodiesel industry) as a cheap, non-toxic, and renewable source for valuable chemicals synthesis. There are numerous methods enacted to convert this glycerol waste to tartronic acid, mesoxalic acid, glyceraldehyde, dihydroxyacetone, oxalic acid and so on. Among these, the green electro-oxidation technique is one of the techniques that possesses potential for industrial application due to advantages such as non-toxicity process, fast response, and lower energy consumption. The current review covers the general understanding on commonly used techniques for alcohol (C1 & C2) conversion, with a specific insight on glycerol (C3) electro-oxidation (GOR). Since catalysts are the backbone of chemical reaction, they are responsible for the overall economy prospect of any processes. To this end, a comprehensive review on catalysts, which include noble metals, non-noble metals, and non-metals anchored over various supports are incorporated in this review. Moreover, a fundamental insight into the development of future electrocatalysts for glycerol oxidation along with products analysis is also presented.

We present here a joint theoretical and experimental study on the oxidation reactivity of glycerol catalysed by chemically pure small Au clusters in the absence and presence of H2O2. From high-resolution mass spectrometry, fruitful products of glyceraldehyde, glyceric acid, tartronic acid, mesoxalic acid and glycolic acid are observed pertaining to the successive Jones oxidation process associated with C-O and C-H bond activation. We then fully demonstrate the reaction pathways on the basis of a complementary-active-sites mechanism, revealing the favourable dehydration of glycerol followed by oxidation to form glyceraldehyde and carboxylic acids in the presence of small Au clusters and H2O2. It is found that the Aun/H2O2 system undertakes a heterolytic mechanism by firstly transferring an O-atom from H2O2 to the Au cluster forming an active intermediate, on which hydride abstraction and subsequent oxygen rebound become thermodynamically possible, promoting the C-H insertion reaction and further oxidation of aldehyde to carboxylic acids.

Glycerol is a major by-product of the biodiesel production and is therefore produced in high quantities. While currently there are limited possible applications for this highly functionalized molecule, glycerol can be a cheap and abundant feedstock for value-added products that are accessible by selective oxidation. Usually, the selective oxidation of glycerol utilizes expensive noble metal catalysts, such as Au, Pt, and Pd. Here we report the selective oxidation of glycerol in basic media, using ordered mesoporous Cu–Al2O3 catalysts with various Cu loadings prepared by a facile soft-templating method. The materials were characterized in detail by nitrogen physisorption, vis-NIR spectroscopy, EDX, low- and wide-angle XRD, XPS, and TEM. Subsequently the reaction conditions for glycerol oxidation were optimized. The catalytic oxidation of glycerol yields C3 products, such as glyceric acid and tartronic acid, and also C2 and C1 products, such as glycolic acid, oxalic acid, and formic acid. Moreover, the role of the solvent on the catalytic reaction was investigated, and the addition of various co-solvents to the aqueous reaction mixture was found to increase the initial reaction rate up to a factor of three. The trends of the initial reaction rates correlate well with the polarity of the water/co-solvent mixtures. The prepared Cu–Al2O3 catalysts are a more cost-efficient and environmentally viable alternative to the reported noble metal catalysts.

Palladium-bismuth nanoparticles were supported into strongly basic anion-exchange resin of gel-type and tested as catalysts for the selective oxidation of glycerol with molecular oxygen at atmospheric pressure. Detailed study of the precursors preparation and reduction were undertaken. The catalyst 3%Pd-1%Bi where the bismuth was deposited on the palladium particles (3.4 nm) exhibited at 95% glycerol conversion more than 63% yield toward glyceric acid and tartronic acid after 3 h of reaction. The catalyst maintains practically similar catalytic performance as in fresh state for at least five consecutive catalytic cycles without extra catalyst treatment and reactivation.

Rationale The identification of hydroxy- and keto-dicarboxylic acids (diacids) in remote marine aerosol samples is important for a better understanding of the composition of organic particulate matter, as this chemical composition is essential for predicting the effects on climate, air quality, and human health. Molecular characterization of these compounds provides insights into sources and formation pathways of organic aerosols. Methods The method of chemical derivatization followed by gas chromatography–flame ionization detection (GC-FID), gas chromatography/quadruple mass spectrometry (GC/QMS) and gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) was used to identify hydroxy- and keto-diacids in remote marine aerosols. Atmospheric samples were collected at Chichijima Island in the western North Pacific and the diacids and related compounds were extracted with organic-free ultrapure water. A two-step derivatization technique was employed, using 14% BF3/n-butanol for the butylation of carboxyl groups and acidic ketones followed by N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) for the trimethylsilylation of hydroxyl groups. Results Several new peaks were detected in the gas chromatogram after trimethylsilylation of the dibutyl ester fraction. Based on mass spectral interpretation with authentic standards, we successfully identified and quantified a homologous series of hydroxydiacids, including tartaric and oxaloacetic acids. In addition, transformation of oxaloacetic acid into its enol form was elucidated. Conclusions Utilizing GC-FID, GC/QMS and GC/TOFMS, hydroxy- and keto-diacids were identified in the remote marine aerosols. A complete structural characterization was achieved with extensive mass spectral analysis. Molecular distributions of hydroxydiacids generally showed the predominance of malic acid followed by tartronic acid. We consider that these hydroxydiacids are important intermediates in the atmospheric oxidation of organic aerosols to result in smaller diacids. Copyright © 2016 John Wiley & Sons, Ltd.

As a dicarboxylic acid with the structural formula HOOCCH (OH) COOH, tartronic acid is considered as an inhibitor of the transformation of carbohydrates into fat under fat-deficient diet conditions. However, the effect of tartronic acid on lipogenesis under high-fat diet conditions has yet to be established. In this work, we investigated the regulatory role of tartronic acid in lipogenesis in 3T3-L1 adipocytes and C57BL/6J mice. The results confirmed that tartronic acid promoted weight gain (without affecting food intake) and induced adipocyte hypertrophy in epididymal white adipose tissue and lipid accumulation in the livers of high-fat diet-induced obese mice. In vitro, tartronic acid promoted 3T3-L1 adipocyte differentiation by increasing the protein expression of FABP-4, PPARγ and SREBP-1. Moreover, the contents of both acetyl-CoA and malonyl-CoA were significantly upregulated by treatment with tartronic acid, while the protein expression of CPT-1β were inhibited. In summary, we proved that tartronic acid promotes lipogenesis by serving as substrates for fatty acid synthesis and inhibiting CPT-1β, providing a new perspective for the study of tartronic acid.

Magnetically separable monometallic and bimetallic Au and Pt NPs anchored on TiO2 nanocomposite were prepared using dahlia flower extract through a greener approach. The prepared nanoparticles (NPs) act as an efficient active metal-based catalyst for glycerol oxidation reaction (GOR) and organic compounds reduction reaction (ORR). The phytochemicals present in dahlia flower extract acts as reducing and stabilizing agent for the development of metal NPs on TiO2 surface. For bimetallic (Fe3O4@TiO2–AuPt) NPs, the conversion efficiency for GOR was found to be 2-fold higher than those of monometallic NPs. The products of GOR over magnetically separable monometallic and bimetallic catalysts were analyzed by HPLC and products such as formic acid (FA), glycolic acid (GCA), glyceric acid (GLA), and tartronic acid (TA) were detected. In addition, ORR of 4-nitrophenol (4-NP), methylene blue (MB) and congo red (CR) in the existence of sodium borohydride (NaBH4) were studied. It was found that the reduction reactions were completed within a few seconds for mono- and bimetallic nanocomposites. Comparatively, Fe3O4@TiO2–AuPt nanocomposite showed much higher efficacy (8, 6 and 5 s) for 4-NP, MB and CR reduction along with very good stable catalytic activity (∼98%) after six cycles. We hypothesize that the improved yield in GOR and faster reduction in ORR by Fe3O4@TiO2–AuPt nanocomposites are related to the synergistic effect of metal alloy formation and support materials.

N-Doped mesoporous carbons (NMCs) with extra framework magnesium were prepared by a one-pot method and used as supports for Pt catalysts. The surface basicity of NMC improved in the presence of extra framework magnesium (e.g., -Ph-O-Mg), meanwhile, the electron density of Pt was enriched by the electron transfer from graphitic N in NMC to Pt. As a result, the catalytic activity of the supported Pt catalyst was improved to be able to selectively oxidize glycerol (GLY) to tartronic acid (TA) under base-free conditions.

Au and AuPd nanoparticles supported on MgO and Al2O3 supports were employed for the selective aqueous phase oxidation of glycerol under basic conditions. Catalysts were prepared by sol-immobilisation without the addition of a stabilizing agent such as polyvinyl alcohol (PVA), which is generally added to stabilize the noble metal sol prior to immobilisation on. The obtained materials prepared with and without stabilizing agent were active for glycerol oxidation and showed similar catalytic performances - implying that the stabilizing polymer is not required to obtain active materials. Depending on the support used, it was possible to tailor the selectivity towards desired oxidation products by using catalysts prepared with or without stabilizing agent. PVA-free Au/ Al2O3 exhibited a remarkably high selectivity towards tartronic acid (40% at 97% conversion), which was not observed for the analogous sample prepared with PVA. Selective glycerol oxidation performed under base-free conditions over AuPd/MgO catalysts also corroborated the previous results that the presence of a stabilizing polymer is not required to prepare active catalysts by sol-immobilisation. Thus, a facile way is presented herein to circumvent the inherent drawbacks encountered by the use of polymer stabilizers during catalyst preparation and the experimental results in fact suggest that the presence of the polymer stabilisers can affect the reaction pathways and control selectivity.

Tartronic acid (TA) is a high value-added chemical widely used as a pharmaceutical product and a preservative; however, its synthesis technology is complicated and high cost. In this study, aqueous solutions of lactic acid were photochemically converted into TA via green oxidation by using hydrogen peroxide (H2O2).

Au-Pt bimetallic catalysts were supported on different supports, including acidic (TiO 2 and CeO 2 ), basic (MgO, Mg(OH) 2 , (MgCO 3 ) 4 Mg(OH) 2 , ZnO, and CaCO 3 ), and amphoteric (Al 2 O 3 and hydrotalcite) supports with the aim to study the effect of the acid/base properties of supports upon the performance of Au-Pt bimetallic catalysts in glycerol oxidation. The results showed that these properties significantly affected the selectivity of products. The selectivity to glyceraldehyde was inversely proportional to the strength of supports’ basic sites, and the selectivity to tartronic acid (or glycolic acid, or glyoxalic acid) was proportional to the strength of basic sites. In contrast, the selectivity to glyceric acid was neither proportional to the strength of basic sites nor proportional to the strength of acid sites. The doping of another weaker basic site also affected the selectivity to glyceric acid. Furthermore, the role of the acid/base nature of the supports in affecting the products’ distribution is proposed.

Made available in DSpace on 2018-11-26T17:40:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-09-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The electrochemical degradation of tebuthiuron (TBH; 100 mg L (1)) was carried out under enhanced mass transport conditions (using a flow cell with a BDD anode), while investigating the effect of solution pH, absence and presence of Cl ions in the supporting electrolyte solution (0.1 mol L (1) Na2SO4), and current density (j = 10, 30, 50 mA cm (2)) on the herbicide degradation and resulting oxidation intermediates. The enhanced mass transport conditions led to significantly improved performances, comparatively to previous results obtained with a common electrochemical cell. The solution pH or presence of Cl ions did not affect the TBH removal rate. However, the COD removal rate, despite being independent of pH, was significantly faster in the presence of Cl ions, most probably due to false results caused by organochlorinated intermediates. In the absence of Cl ions in solution, the TBH removal rate increased with j, whereas the COD removal rate was not affected, but significantly increased removal rates were attained in the presence of Cl ions, most probably because of increased formation of organochlorines. As expected, higher values of the general and mineralization current efficiencies as well as lower energy consumptions per unit TOC mass removed (ECTOC) were attained at 10 mA cm (2); in the absence of Cl ions, complete removal of TBH and 80% removal of TOC were attained with ECTOC = 0.2 kW h g (1) (less than 1/10 of those for electrolyses using a conventional electrochemical cell). From the identified intermediates, an initial TBH oxidation pathway like those of coupled processes involving photochemistry is expected. Most carboxylic acid intermediates were removed or being removed by the end of the electrolyses (except tartronic acid, which accumulated). As expected, organochlorinated intermediates were identified in the presence of Cl ions, but were completely removed by the end of the electrolyses. In summary, the electrochemical degradation of TBH in the presence of Cl ions is not advantageous; no significant improvement in the TBH and TOC removal rates, or in the energy expense, is achieved and the formation of organochlorines is a real possibility. (C) 2017 Elsevier Ltd. All rights reserved. Univ Fed Sao Carlos, Dept Quim, CP 676, BR-13560970 Sao Carlos, SP, Brazil Univ Estadual Paulista, Inst Quim Araraquara, Dept Quim Analit, BR-14800900 Araraquara, SP, Brazil Univ Estadual Paulista, Inst Quim Araraquara, Dept Quim Analit, BR-14800900 Araraquara, SP, Brazil FAPESP: 2008/10449-7 CNPq: 487270/2012-6

Solutions of ribose, glucose, and sucrose in water and phosphate buffer were treated with non-thermal plasma generated by using a dielectric barrier discharge (DBD) device and the oxidation products were characterized by 1H NMR and GC–MS. Our results demonstrate that these sugars are decomposed to formic acid, glycolic acid, glyceric acid, tartronic acid, tartaric acid, acetic acid, and oxalic acid after direct exposure to DBD plasma. The concentrations of these compounds are time-dependent with plasma treatment. The decomposition mechanisms of these sugars under the DBD plasma are also proposed in this study.

This is a comparative study of photolytic degradation under exposure to UV254 nm and solar-simulator irradiation of a mixture of eight equally concentrated relevant micropollutants in the presence of H2O2 and Fe(II) in ultrapure water, Lake Geneva water, and effluent from a wastewater treatment plant (WWTP). The electron-spin resonance (ESR) experiments point to a low efficiency of singlet oxygen formation by the mixture of micropollutants. This finding corroborates with the chemical stability of the micropollutants under UVC irradiation (in decreasing order: gabapentin, metformin, metoprolol, atenolol, clarithromycin, primidone, methylbenzotriazole, and benzotriazole). The oxidation rate increased in the presence of low-concentration H2O2 and Fe(II), except for metformin and gabapentin. Gabapentin and metformin were the most persistent compounds, less than 24% were removed after 60 minutes of UV254/H2O2/Fe(II) treatment. The low micropollutant removal rates were observed in WWTP effluent and lake water, and using sunlight simulation. Guanylurea, phenol, oxalic acid, tartronic acid, glycolic acid, oxamic acid, and maleic acid, could also be detected as fragmental oxidation products. Furthermore, up to 300 µg/L of nitrate and ammonia were identified as final degradation products. Ecotoxicological tests showed that the degradation products are more toxic for algae Chlamydomonas reinhardtii than the parent compounds themselves.