Conversion Of Dihydroxyacetone Research Articles

Solar-driven highly selective conversion of glycerol to dihydroxyacetone using surface atom engineered BiVO4 photoanodes

Dihydroxyacetone is the most desired product in glycerol oxidation reaction because of its highest added value and large market demand among all possible oxidation products. However, selectively oxidative secondary hydroxyl groups of glycerol for highly efficient dihydroxyacetone production still poses a challenge. In this study, we engineer the surface of BiVO4 by introducing bismuth-rich domains and oxygen vacancies (Bi-rich BiVO4-x) to systematically modulate the surface adsorption of secondary hydroxyl groups and enhance photo-induced charge separation for photoelectrochemical glycerol oxidation into dihydroxyacetone conversion. As a result, the Bi-rich BiVO4-x increases the glycerol oxidation photocurrent density of BiVO4 from 1.42 to 4.26 mA cm−2 at 1.23 V vs. reversible hydrogen electrode under AM 1.5 G illumination, as well as the dihydroxyacetone selectivity from 54.0% to 80.3%, finally achieving a dihydroxyacetone production rate of 361.9 mmol m−2 h−1 that outperforms all reported values. The surface atom customization opens a way to regulate the solar-driven organic transformation pathway toward a carbon chain-balanced product.

Tailoring and Identifying Brønsted Acid Sites on Metal Oxo-Clusters of Metal-Organic Frameworks for Catalytic Transformation.

Metal-organic frameworks (MOFs) with Brønsted acidity are an alternative solid acid catalyst for many important chemical and fuel processes. However, the nature of the Brønsted acidity on the MOF's metal cluster or center is underexplored. To design and optimize the acid strength and density in these MOFs, it is important to understand the origin of their acidity at the molecular level. In the present work, isoreticular MOFs, ZrNDI and HfNDI (NDI = N,N'-bis(5-isophthalate)naphthalenediimide), were prepared as a prototypical system to unravel and compare their Brønsted and Lewis acid sites through an array of spectroscopic, computational, and catalytic characterization techniques. With the aid of solid-state nuclear magnetic resonance and density functional calculations, Hf6 oxo-clusters on HfNDI are quantitatively proved to possess a higher density Brønsted acid site, while ZrNDI-based MOFs display stronger and higher-population Lewis acidity. HfNDI-based MOFs exhibit a superior catalytic performance in activating dihydroxyacetone (DHA) and converting DHA to ethyl lactate, with 71.1% selectivity at 54.7% conversion after 6 h. The turnover frequency of BAS-dominated Hf-MOF in DHA conversion is over 50 times higher than that of ZSM-5, a strong BAS-based zeolite. It is worth noting that HfNDI is reported for the first time in the literature, which is an alternative platform catalyst for biorefining and green chemistry. The present study furthermore highlights the uniqueness of Hf-based MOFs in this important biomass-to-chemical transformation.

Aluminum‐based Metal‐Organic Framework as Water‐tolerant Lewis Acid Catalyst for Selective Dihydroxyacetone Isomerization to Lactic Acid

AbstractLactic acid is a renewable and versatile chemical for food, pharmaceuticals, cosmetics, and other chemicals. Lactic acid can be produced from biomass‐derived dihydroxyacetone. However, selective and recyclable water‐tolerant acid catalysts need to be developed for the specific production of lactic acid. Here we show that the MIL‐101(Al)−NH2 metal‐organic framework (MOF) is a water‐tolerant and selective solid Lewis acid catalyst for dihydroxyacetone isomerization to lactic acid. The Lewis acidic MIL‐101(Al)−NH2 catalyst promoted a high lactic acid selectivity of 91 % at 96 % dihydroxyacetone conversion at 120 °C in water. The reaction proceeded by temperature and/or MIL‐101(Al)−NH2 MOFs mediated dihydroxyacetone dehydration to pyruvaldehyde. Subsequently, the MIL‐101(Al)−NH2 facilitated rehydration of the pyruvaldehyde to lactic acid. The Lewis acidic MIL‐101(Al)−NH2 catalyst was stable and reusable four times without any decrease in catalytic performance.

Bimetallic Zeolite Beta Beads with Hierarchical Porosity as Brønsted-Lewis Solid Acid Catalysts for the Synthesis of Methyl Lactate

Bimetallic zeolite Beta in bead format and containing Al sites with Brønsted acid behavior and Sn, Zr or Hf sites with Lewis acid character, were prepared using a two-step synthetic route. First, zeolite Beta in the format of macroscopic beads (400 to 840 μm) with hierarchical porosity (micropores accessed through meso- and macropores in the range of 30 to 150 nm) were synthesized by hydrothermal crystallization in the presence of anion-exchange resin beads as hard template and further converted into their H-form. Next, the zeolite beads were partially dealuminated using different concentrations of HNO3 (i.e., 1.8 or 7.2 M), followed by grafting with one of the above-mentioned metals (Sn, Zr or Hf) to introduce Lewis acid sites. These bimetallic zeolites were tested as heterogeneous catalysts in the conversion of dihydroxyacetone (DHA) to methyl lactate (ML). The Sn-containing zeolite Beta beads treated by 1.8 M HNO3 and grafted with 27 mmol of SnCl4 (Sn-deAl-1.8-Beta-B) demonstrated the best catalytic activity among the prepared bimetallic zeolite beads, with 99% selectivity and 90% yield of ML after 6 h at 90 °C. This catalyst was also tested in combination with Au-Pd nanoparticles supported on functionalized carbon nanotubes (CNTs) as multifunctional catalytic system for the conversion of glycerol to ML, achieving 29% conversion of glycerol and 67% selectivity towards ML after 4.5 h at 140 °C under 30 bar air. The catalytic results were rationalized by means of a thorough characterization of the zeolitic beads with a combination of techniques (XRD, N2-physisorption, SEM, XRF, TEM, UV-vis spectroscopy and pyridine-FT-IR).

Comparison of Synthetic and Natural Zeolite Catalysts’ Behavior in the Production of Lactic Acid and Ethyl Lactate from Biomass-Derived Dihydroxyacetone

This article presents the results of the conversion of dihydroxyacetone (DHA) to lactic acid (LA) with the use of zeolite catalysts. For this purpose, synthetic zeolite beta (BEA) and natural clinoptilolite (CLI) were used as a matrix. The zeolites were modified with various metals (Sn, Fe, Cu and Zn) during ion exchange under hydrothermal conditions. The DHA conversion process with the participation of metal-functionalized zeolites allowed us to obtain intermediates, i.e., pyruvic aldehyde (PAL), which during the further reaction was transformed into a mixture of products such as ethyl lactate (EL), pyruvic aldehyde (PA), lactic acid and ethyl acetate (EA). The best selectivity towards lactic acid was achieved using Sn-CLI (100%) > Na-BEA (98.7%) > Sn-BEA (95.9%) > Cu-BEA (92.9%), ethyl lactate using Cu-CLI, and pyruvic aldehyde using the Zn-BEA catalyst. In the case of a natural zeolite, modification with Sn is promising for obtaining a pure lactic acid with a relatively good carbon balance.

Desarrollo de Zeolitas Ga-ZSM-11 para la Síntesis de Ácido Láctico

En el presente trabajo se analiza la influencia de la temperatura de reacción y del contenido de galio en la zeolita ZSM-11 (estructura MEL) en la obtención de ácido láctico a partir de dihidroxiacetona (DHA). El catión metálico fue incorporado por impregnación húmeda en distintas concentraciones (~ 2-10% p/p). La estructura ZSM-11 se confirmó por DRX para todas las muestras, en tanto que en los materiales impregnados la cristalinidad disminuyó a medida que se incrementó la cantidad del catión incorporado al catalizador. Por el método BET se analizó el área superficial y se encontró que la misma disminuye al aumentar el contenido de Ga incorporado. Mediante FTIR con adsorción de piridina se determinó la cantidad, fuerza y relación de sitios ácidos. El estudio por TPR señaló la reducción de las especies superficiales vecinas a los enlaces Ga-O y la reducción de Ga+3 a Ga+. El análisis de reflectancia difusa de UV-visible indicó la dispersión de los posibles aglomerados de óxidos de galio. Dichos materiales exhibieron un buen desempeño catalítico en la conversión de dihidroxiacetona (DHA) a ácido láctico, molécula plataforma de gran interés actual

Selective Oxidation of Crude Glycerol to Dihydroxyacetone in a Biphasic Photoreactor

In this paper, the first biphasic photoreactor was introduced and utilized for the conversion of glycerol to glyceraldehyde (GAD) and dihydroxyacetone (DHA) using water and ethyl acetate as dispersed (active) and continuous (inactive) phases, respectively. Increasing the ethyl acetate content in the reactor improved the DHA yield; however, the optimal DHA selectivity was obtained at an ethyl acetate to water ratio of 90:10 (vol/vol). Compared to a monophasic photoreactor containing only water and identical amounts of glycerol and photocatalyst, the biphasic reactor containing 90 vol % ethyl acetate increased the DHA yield by a factor of 2.9 (from 4.5% to 13%) and the concentration of DHA by approximately 14 times (from 0.08 mM to 1.1 mM) after 240 min. Additionally, photocatalytic conversion of crude glycerol extracted using a 90:10 (vol/vol) ethyl acetate-water mixture showed a similar DHA conversion and yield to that of pure glycerol.

Conversion of Dihydroxyacetone to Methyl Pyruvate Catalyzed by Hybrid Molecular Sieves at Low Temperature: A Strategy for the Green Utilization of Glycerol

Methyl pyruvate (MPA) was synthesized from dihydroxyacetone (DHA), the oxidation product of glycerol, over Sn-β and TS-1 hybrid molecular sieves at low temperature. Sn-β and TS-1 provide the active sites for conversion of DHA to methyl lactate (MLA) and oxidation of MLA to MPA, respectively. Synergism of Lewis acid sites on Sn-β and TS-1 realize the production of MPA from DHA. After optimization, 71% yield of MPA can be obtained under 50 °C. This is the first report for the synthesis of MPA from DHA directly.

Desarrollo de Zeolitas Sn-ZSM-11 para la Síntesis de Lactatos de Alquilo

En el presente trabajo se exponen distintas alternativas de incorporación de Sn en la zeolita ZSM-11 (estructura MEL): impregnación por vía húmeda, tratamiento alcalino y síntesis hidrotérmica con estaño como heteroátomo; así como diferente contenido de catión metálico (~2-10% p/p). La estructura ZSM-11 se confirmó por DRX para todas las muestras, en tanto que en los materiales impregnados la cristalinidad disminuyó a medida que se incrementó la cantidad del metal incorporado al catalizador. El estudio por TPR señaló la reducción de las especies superficiales vecinas a los enlaces Sn-O y la reducción de Sn+4 a Sn+2. Por el método BET se analizó el área superficial y se encontró que la misma disminuye al aumentar el contenido de Sn incorporado por impregnación húmeda y por síntesis hidrotérmica. Mediante FTIR con adsorción de piridina se determinó la cantidad, fuerza y relación de sitios ácidos. Dichos materiales exhibieron un buen desempeño catalítico en la conversión de dihidroxiacetona (DHA) a alquil lactatos de cadena corta, éstos últimos representan solventes verdes prometedores.

Toxicity of dihydroxyacetone is exerted through the formation of methylglyoxal in Saccharomyces cerevisiae: effects on actin polarity and nuclear division.

Dihydroxyacetone (DHA) is the smallest ketotriose, and it is utilized by many organisms as an energy source. However, at higher concentrations, DHA becomes toxic towards several organisms including the budding yeast Saccharomyces cerevisiae In the present study, we show that DHA toxicity is due to its spontaneous conversion to methylglyoxal (MG) within yeast cells. A mutant defective in MG-metabolizing enzymes (glo1Δgre2Δgre3Δ) exhibited higher susceptibility to DHA. Intracellular MG levels increased following the treatment of glo1Δgre2Δgre3Δ cells with DHA. We previously reported that MG depolarized the actin cytoskeleton and changed vacuolar morphology. We herein demonstrated the depolarization of actin and morphological changes in vacuoles following a treatment with DHA. Furthermore, we found that both MG and DHA caused the morphological change in nucleus, and inhibited the nuclear division. Our results suggest that the conversion of DHA to MG is a dominant contributor to its cytotoxicity.

Facile synthesis of Sn-containing MFI zeolites as versatile solid acid catalysts

Sn-containing MFI zeolites with controllable Al contents were successfully synthesized with the utilization of the EDTA-Sn complex as tin source and citrate as buffer solution for the first time. The elaborately strategy achieves a right release of Sn4+ ions rate to combine with the silicon tetrahedron species in the synthesis process which could make the heteroatom tin warmly incorporate into the zeolite frameworks. The structural information about the Sn-containing MFI zeolites was confirmed by XRD, FTIR, and solid-state NMR spectroscopy. Characterization results of HRTEM, FTIR, XPS, and UV-vis spectroscopy illustrated that most Sn species exist as isolated tetrahedral Sn(IV) in the as-prepared zeolites. The creation of Lewis acid sites in Sn-MFI and Sn-Al-MFI zeolites, and Brønsted acid sites in Sn-Al-MFI zeolites were determined by FTIR spectroscopy of pyridine adsorption and 1H and 31P MAS NMR spectroscopy after ammonia and trimethylphosphine oxide (TMPO) adsorption. Both the Sn-MFI and Sn-Al-MFI zeolite catalysts exhibit a remarkable catalytic performance in the conversion of dihydroxyacetone (DHA) to methyl lactate (ML), while the bifunctional Sn-Al-MFI catalyst exhibits a significant combination effect, and a remarkable active site-based turnover frequency with a high methyl lactate productivity can be achieved.

Rapid room temperature synthesis of tin-based mesoporous solids: Influence of the particle size on the production of ethyl lactate

A series of tin-based mesoporous catalysts was prepared via a novel straightforward sol-gel procedure leading to an extremely short synthesis time decreased up to 5 min at room temperature. This synthesis, together with the precise control of the selected particle size, represents an advancement compared to the state of the art and can be easily applied to large scale production. Characterization of the materials revealed the presence of MCM-41 like architecture with a high specific surface area, narrow pore size distribution, insertion of tin in tetrahedral coordination and a good balance of Lewis/Brønsted acidity. Moreover, all these characteristics were almost identical for the entire series thus making these solids an ideal case study to investigate the influence of the particle size on the catalytic behavior. The Sn-containing materials were tested as catalysts in the conversion of dihydroxyacetone into ethyl lactate. The excellent correlation between particle size and catalytic performances proves the importance of size control. In addition, the absence of leaching was proved via hot filtration experiments and the materials preserved their activity in multiple catalytic cycles.

Dihydroxyacetone conversion into lactic acid in an aqueous medium in the presence of metal salts: influence of the ionic thermodynamic equilibrium on the reaction performance

Different Lewis acid aluminium complexes catalyse the successive reactions to convert dihydroxyacetone into lactic acid in an aqueous medium.

Kinetic and mechanistic study of triose sugar conversion on Lewis and Brønsted acid solids

The effect of catalyst acid site nature on the reaction kinetics of the liquid-phase conversion of dihydroxyacetone with ethanol was investigated using Brønsted and Lewis acid solids. The reaction proceeds through a complex reaction network involving a sequence of consecutive and parallel reaction steps. Main final products were ethyl lactate and pyruvic aldehyde diethyl acetal. Different catalysts such as the cesium salt of tungstophosphoric acid (Cs-HPA), Amberlyst resin and alumina-supported tin and zinc oxides were used. Catalysts were characterized by ICP, X-ray diffraction, N2 physisorption, TPD of NH3 and FTIR of adsorbed pyridine. Cs-HPA contains only Brønsted acid sites and alumina-supported tin and zinc samples show exclusively Lewis acidity. During dihydroxyacetone conversion, the selectivities to the final products strongly depend on the nature of the surface acid sites present on the solids. Brønsted acid solids favor the synthesis of pyruvic aldehyde diethyl acetal with final yields of up to 93%, whereas the ethyl lactate is the main product on Lewis acid solids, reaching final yields of about 51%. A kinetic model based on a pseudohomogeneous mechanism was proposed to interpret the experimental catalytic data. The comparison of the kinetic rate constants obtained on both kinds of acid solids confirms that on Brønsted catalysts the route toward pyruvic aldehyde diethyl acetal is clearly favored. On Lewis solids, the synthesis of ethyl lactate occurs selectively via isomerization of the pyruvic aldehyde hemiacetal intermediate.

Kinetics of conversion of dihydroxyacetone to methylglyoxal in New Zealand mānuka honey: Part III – A model to simulate the conversion

A kinetic model for the conversion of dihydroxyacetone (DHA) to methylglyoxal (MGO) in honey is proposed; a building block approach was used to create the model. Artificial honeys doped with DHA and individual perturbants were fitted first, then multiple perturbants (alanine, proline and iron, and combinations of these) were fitted before comparing the simulation to real honey samples (doped clover and mānuka honey). The main responses in the prediction model were DHA, MGO, proline, primary amino acids, acidity, 3-phenyllactic acid and 4-methoxyphenyllactic acid. Three temperatures (20, 27 and 37°C) were studied and the conversion of DHA to MGO was monitored over at least 1year. Differences in the conversion between clover doped with DHA and mānuka honey were observed. The simulation fitted well for the honeys tested.

Kinetics of the conversion of dihydroxyacetone to methylglyoxal in New Zealand mānuka honey: Part II – Model systems

The irreversible dehydration reaction of dihydroxyacetone (DHA) to methylglyoxal (MGO) in a honey model system has been examined to investigate the influence of added perturbant species on the reaction rate. The secondary amino acid proline, primary amino acids (alanine, lysine and serine), and iron, or combinations of these perturbants, were added to artificial honey with either DHA or MGO and stored at 20, 27 and 37°C. These systems were monitored over time. A 1:1 conversion of DHA to MGO was not observed in any system studied, including the control system with no added perturbants. Addition of proline to the matrix increased consumption of DHA but did not produce any more MGO than the control sample. Lysine and serine behaved similarly. Alanine enhanced the conversion of DHA to MGO and had the best efficiency of conversion of DHA to MGO for the amino acids studied. An iron II salt enhanced the conversion of DHA to MGO, even in the presence of proline.

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Metal-containing TUD-1 mesoporous silicates as versatile solid acid catalysts for the conversion of bio-based compounds into valuable chemicals

Three-dimensional mesoporous silicates of the TUD-1 family were synthesised with different metals (Zr, Hf and Sn) incorporated in the framework of the material. The mesoporosity of the prepared TUD-1s was confirmed by X-ray diffraction (XRD), nitrogen physisorption and TEM. The incorporation of the metals in the silicate structure was investigated by FT-IR and UV–Vis spectroscopy. All three TUD-1 materials present a combination of Lewis and mild Brønsted acid sites, as determined by TPD-FT-IR of pyridine adsorption. The metal-containing TUD-1 materials were tested as solid acid catalysts for the conversion of three bio-based compounds into valuable chemical products. In the conversion of dihydroxyacetone into ethyl lactate, complete selectivity towards the desired lactate product was achieved with Zr-, Hf- and Sn-TUD-1. The three heterogeneous catalysts displayed similar activity, with Hf-TUD-1 reaching the highest conversion and metal-based turnover number. Sn-TUD-1 also displayed high activity and selectivity in two acetalisation reactions, i.e. the synthesis of solketal from acetone and glycerol and the reaction of vanillin with propylene glycol. The catalytic performance of these TUD-1 materials is ascribed to the high accessibility of their active sites and to the suitable combination of acid sites. The catalysts were successfully reused in consecutive runs and did not suffer from leaching.

Activity and Selectivity of an Amphoteric ZrO2–TiO2 Catalyst in the Conversion of Dihydroxyacetone into Ethyl Lactate and Lactic Acid

A 96% conversion of dihydroxyacetone dissolved in aqueous ethanol mixtures was achieved on an amphoteric ZnO2–TiO2 catalyst in a flow reactor at 140 °C and 1.0 MPa with identical selectivity relative to the two reaction products, lactic acid and ethyl lactate. Variation of the ethanol : water ratio significantly affects the activity and selectivity of the catalyst. The maximum catalyst efficiency was achieved using an aqueous solution containing 65 mass % ethanol.

Extra-small porous Sn-silicate nanoparticles as catalysts for the synthesis of lactates

A series of Sn-MCM-41 nanoparticles (XS-Sn-MCM-41) with a diameter ranging from 20 to 140nm and very high specific surface area were successfully prepared and tested as heterogeneous catalysts for the conversion of the triose sugar dihydroxyacetone to ethyl lactate. Characterization of the materials indicated that the physicochemical properties of the nanoparticles can be significantly affected by different synthesis parameters, including the metal loading, the sequence of adding the Si and Sn precursors into the synthesis mixture, the preparation time and temperature. Most of the XS-Sn-MCM-41 catalysts displayed higher activity compared to conventional Sn-MCM-41 with large particle size in the conversion of dihydroxyacetone into ethyl lactate. The superiority of the best XS-Sn-MCM-41 catalyst in terms of conversion and turnover number is correlated to its high amount of accessible acid sites, which in turn is ascribed to a combination of different physicochemical features such as high surface area, particles morphology and coordination of the tin atoms in tetrahedral framework sites. The best catalyst can be reused in consecutive runs without loss of activity.