Selective Oxidation Of Glycerol Research Articles

Mofs-derived transition metal carbon-based compounds supported Au-Pt catalyst for the catalytic oxidation of glycerol to glyceric acid

Accurately controlling the directional activation of the primary and secondary hydroxyls and preventing the deep oxidation of oxygen-containing functional groups and the degree of C–C cleavage is still a great challenge for the selective oxidation of glycerol to glyceric acid. Hence, a series of bimetallic Au-Pt/MxOyCz catalysts (M = Cu, Co, Ce, Mn, Ni, Zn, Zr) were prepared using MOFs-derived transition metal carbon-based compounds as the support. These catalysts were utilized for glycerol catalytic oxidation to glyceric acid under basic conditions. The experimental date indicated that the type of transition metal makes a big difference on the conversion of glycerol and the selectivity of glyceric acid under the mild condition of 60 ℃. Among them, the Mn-modified carbon-based compound supported Au-Pt/MnxOyCz catalyst has the best catalytic activity. After reaction for 2 h, the conversion of glycerol could reach 100 %, and the selectivity of glyceric acid could reach 57.3 %. The reason for the best activity of the Au-Pt/MnxOyCz catalyst is that the particle size of active molecules is small, and the strong metal-support interaction produces more active sites. Specifically, Au-Pt/MnxOyCz catalyst forms an Au-Pt alloy, and the synergy between alloyed Au-Pt and Mn&+ enhances the acidity of the catalyst, causing it to produce the most acidic sites and promoting the dispersion of metal nanoparticles. The strong basic site of the catalyst can promote Au-Pt electron transfer, which in turn changes the reducing properties of Au-Pt and enriches the oxygen vacancies of the catalyst. Therefore, the synergistic interaction between the acidic sites and strong basic sites promotes the activation of Au-Pt, which in turn promotes the reduction of Mn-based oxides and the activation and migration of oxygen. This work will offer some new recommendations for the development of MOFs-derived transition metal-based catalysts for the catalytic oxidation of bio-polyols under mild conditions.

Long-Term Selective Photoelectrochemical Glycerol Oxidation via Oxygen Vacancy Modulated Tungsten Oxide with Self-Healing.

The photoelectrochemical selective oxidation of biowaste glycerol into the high value-added material, along with hydrogen production, holds significant promise for advancing renewable and sustainable energy technologies. Here, the surface oxygen state of tungsten oxide is modified to selectively oxidize glycerol into glyceraldehyde, a high-value-added material, and the selectivity is maintained over a prolonged period using the photo-stimulated self-recovery capability. The surface-coordinated photoelectrode exhibits high charge transfer efficiency to glycerol and favorable glycerol adsorption capacity, enabling the selective conversion of glycerol. At 1.2 VRHE in a 2m glycerol electrolyte adjusted to pH 2, the tungsten oxide photoelectrode achieves a photocurrent density of 2.58mA cm-2 and a production rate of 378.8mmol m-2h-1 with selectivity of 86.1%. The high selectivity is preserved for 18 h by utilizing the self-healing capability of tungsten oxide to restore initial states modified by photoelectrochemical oxidation. This work sheds light on the design of highly efficient metal oxide photoelectrodes for selective biomass oxidation over extended periods.

Dynamic Fe-O-Cu induced electronic structure modulation on CuOx electrode for selective electrocatalytic oxidation of glycerol

Electrocatalytic glycerol oxidation reaction to produce high-value organic chemicals has research significance for managing the overproduction of glycerol and handling the energy crisis. Herein, a copper-based self-supporting catalytic electrode with a dynamic Fe-O-Cu optimized coordination (Fe-CuOx/CF) was prepared. The oxygen-bridged asymmetric coordination structure (Fe-O-Cu) optimized the electronic configuration and promoted the formation of the crucial intermediate species. After Fe was embedded in the lattice of copper oxides, a remarkable enhancement in the adsorption capacity of OH- and glycerol was confirmed. As a result, Fe-CuOx/CF exhibited an excellent production capacity of formate, with high faradaic efficiency and selectivity values of 93.65 % and 95.10 %. Concurrent production of formate and high purity hydrogen was achieved in the double-electrode flow electrolyzer. This work provides guiding significance for the optimization of the catalytic coordination and the design of high-efficiency transition metal-based catalysts for electrooxidation of biomass platform molecules.

Manipulating Pt-ZnO interface for fast selective oxidation of glycerol to glyceric acid in base-free medium

Fine constructing the desirable active sites of catalysts is critical for the efficient polyol oxidation. Herein, we conceptually manipulate the Pt-ZnO interfacial active site instead of traditional Pt-Pt active site to isolate oxidation reaction and carboxylic acid desorption for fast selective oxidation of glycerol to glyceric acid in base-free medium. Multiple characterizations (including in-situ spectroscopy, reaction kinetics and density functional theory calculation, etc.) revealed that the strong electronic delocalization of Pt d-partial and the synergistic effect of ZnO adsorption could collectively strengthen the adsorption of glycerol and then promote the C-H bond of RCH2O intermediate in the primary hydroxyl group oxidation, resulting in higher catalytic activity over the Pt-ZnO interface. Meanwhile, the abundant oxygen vacancy of well-dispersed nano-ZnO could preferentially adsorb the formed glyceric acid product, preventing the coverage of the efficient Pt-Pt and Pt-O-Zn active sites by carboxylic acid products. Such tailored interface strategy achieves 80.4 % glycerol conversion and 84.6 % glyceric acid selectivity in only 1 h, and the turnover frequency could also be as high as 1338.4 h−1 over the optimal Pt/ZnO-MCM-41 (200) catalyst. The methodology provided here constitutes a promising basis for highly efficient polyol oxidation catalysis under mild and green conditions.

Enhanced Selective Oxidation of Glycerol to Dihydroxyacetone over Pt@Sn-MFI Zeolites

Enhanced Selective Oxidation of Glycerol to Dihydroxyacetone over Pt@Sn-MFI Zeolites

Improving the Electrochemical Glycerol-to-Glycerate Conversion at Pd Sites via the Interfacial Hydroxyl Immigrated from Ni Sites.

The electrochemical conversion of glycerol into high-value chemicals through the selective glycerol oxidation reaction (GOR) holds importance in utilizing the surplus platform chemical component of glycerol. Nevertheless, it is still very limited in producing three-carbon chain (C3) chemicals, especially glyceric acid/glycerate, through the direct oxidation of its primary hydroxyl group. Herein, Pd microstructure electrodeposited on the Ni foam support (Pd/NF) is designed and fabricated to achieve a highly efficient GOR, exhibiting a superior current density of ca. 120 mA cm-2 at 0.8 V vs. reversible hydrogen electrode (RHE), and high selectivity of glycerate at ca. 70%. The Faradaic efficiency of C3 chemicals from GOR can still be maintained at ca. 80% after 20 continuous electrolysis runs, and the conversion rate of glycerol can reach 95% after 10-h electrolysis. It is also clarified that the dual-component interfaces constructed by the adjacent Pd and Ni sites are responsible for this highly efficient GOR. Specifically, Ni sites can effectively strengthen the generative capacity of the active adsorbed hydroxyl (OHad) species, which can steadily immigrate to the Pd sites, so that the surface adsorbed glycerol species are quickly oxidized into C3 chemicals, rather than breaking the C-C bond of glycerol; thus, neither form the C2/C1 species. This study may yield fresh perspectives on the electrocatalytic conversion of glycerol into high-value C3 chemicals, such as glyceric acid/glycerate.

Selective oxidation of glycerol mediated by surface plasmon of gold nanoparticles deposited on titanium dioxide nanowires

This paper describes an alternative method for the in situ synthesis of gold nanoparticles (AuNPs) with a particle size of less than 3 nm, using nanoreactors formed by reverse micelles of 1,4-bis-(2-ethylhexyl) sulfosuccinate sodium (AOT) and nanoparticle stabilization with l-cysteine, which favor the preparation of nanoparticles with size and shape control, which are homogeneously dispersed (1% by weight) on the support of titanium dioxide nanowires (TNWs). To study the activity and selectivity of the prepared catalyst (AuNPs@TNWs), an aqueous solution of 40 mM glycerol was irradiated with a green laser (λ = 530 nm, power = 100 mW) in the presence of the catalyst and O2 as an oxidant at 22 °C for 6 h, obtaining a glycerol conversion of 86% with a selectivity towards hydroxypyruvic acid (HA) of more than 90%. From the control and reactions, we concluded that the Ti–OH groups promote the glycerol adsorption on the nanowires surface and the surface plasmon of the gold nanoparticles favors the selectivity of the reaction towards the hydroxypyruvic acid.

Modulating Surface Oxygen Valence States via Interfacial Potential in BiVO4/CoOx/Au Photoanode for Enhanced Selective Photoelectrochemical Oxidation of Glycerol to Dihydroxyacetone

AbstractThe concept of photoelectrochemical conversion of biomass into industrially valuable chemicals presents a compelling strategy to supplant the lower‐value oxygen evolution typically associated with photoanodes. Here, a surface potential manipulation method by regulating the surface oxygen valence states is put forward, which is demonstrated to be effective in enhancing the selective photoelectrochemical oxidation of glycerol to dihydroxyacetone (DHA). This involves the concurrent establishment of a BiVO4/CoOx heterojunction and a BiVO4/Au Schottky junction, aiming to fine‐tune the BiVO4 photoanode's surface potential and improve both its charge carrier separation and interfacial transfer kinetics. The BiVO4/CoOx/Au photoanode exhibits a photocurrent density of 6.15 mA cm−2 at 1.23 V versus reversible hydrogen electrode (RHE). Meanwhile, selective glycerol oxidation efficiency achieves a DHA evolution rate of 339.74 mmol m−2 h−1 and a selectivity exceeding 60%. Experiments and theoretical analysis underscore the pivotal role played by the surface potential in mediating glycerol and DHA adsorption and desorption processes. Additionally, the diminished surface potential attributed to the CoOx and Au amendments is responsible for the decreased Gibbs free energy of the dehydrogenation's rate‐limiting step involving the intermediate carbon species. This work demonstrates a method to design glycerol oxidation catalysts by modulating the interfacial molecular adsorption/desorption by surface potential regulation.

Elucidation of synergism in Ce-Zr/SBA-15 mesoporous catalysts and the effects on the activity in selective glycerol to lactic acid reaction

The continued conversion of glycerol to value-added chemicals is essential in ensuring the sustainable development of the biodiesel industry. Selective catalytic oxidation of glycerol to lactic acid provides an alternative approach to valorizing glycerol. A mesoporous SBA-15 supported mixed-metallic oxide catalyst is deemed essential to selectively produce lactic acid in this mixed parallel and multi-step reaction. SBA-15-supported bimetallic Ce and Zr oxides were proved to be highly efficient catalysts for the selective glycerol oxidation into lactic acid in base-free media. The synergism between Ce and Zr in the bimetallic oxide compounds could enhance the creation of oxygen vacancies in the catalyst via the reduction of Ce4+ to Ce3+. The 2:1CeZr/SBA-15 catalyst exhibited prominent catalytic activity in selectively oxidizing glycerol to lactic acid, with a glycerol conversion of 91.8% and a lactic acid yield of 35.1%. This work achieved superior catalytic performance compared to previously conducted studies, primarily due to the significantly higher initial glycerol concentration employed in this study. To ascertain the intrinsic active sites of the catalyst, the physicochemical properties of the catalyst were thoroughly examined using BET, FTIR, XRD, FESEM, TEM, CO2-TPD, O2-TPD, and H2-TPR analysis. This work concluded that the synergistic interaction of the active sites, which led to the formation of active oxygen species, facilitated primary dehydrogenation of the terminal -OH bond in glycerol. Hence, in this work, a plausible glycerol conversion mechanism over the 2:1CeZr/SBA-15 catalyst was also proposed.

Unsaturated Fe–Ov–Ti5c Structure with Enhanced C–H and C–C Bond Activation Ability for Selective Oxidation of Glycerol to Glycolic Acid

Unsaturated Fe–O_v–Ti_5c Structure with Enhanced C–H and C–C Bond Activation Ability for Selective Oxidation of Glycerol to Glycolic Acid

Electrocatalytic and Selective Oxidation of Glycerol to Formate on 2D 3d-Metal Phosphate Nanosheets and Carbon-Negative Hydrogen Generation.

In the landscape of green hydrogen production, alkaline water electrolysis is a well-established, yet not-so-cost-effective, technique due to the high overpotential requirement for the oxygen evolution reaction (OER). A low-voltage approach is proposed to overcome not only the OER challenge by favorably oxidizing abundant feedstock molecules with an earth-abundant catalyst but also to reduce the energy input required for hydrogen production. This alternative process not only generates carbon-negative green H2 but also yields concurrent value-added products (VAPs), thereby maximizing economic advantages and transforming waste into valuable resources. The essence of this study lies in a novel electrocatalyst material. In the present study, unique and two-dimensional (2D) ultrathin nanosheet phosphates featuring first-row transition metals are synthesized by a one-step solvothermal method, and evaluated for the electrocatalytic glycerol oxidation reaction (GLYOR) in an alkaline medium and simultaneous H2 production. Co3(PO4)2 (CoP), Cu3(PO4)2 (CuP), and Ni3(PO4)2 (NiP) exhibit 2D sheet morphologies, while FePO4 (FeP) displays an entirely different snowflake-like morphology. The 2D nanosheet morphology provides a large surface area and a high density of active sites. As a GLYOR catalyst, CoP ultrathin (∼5 nm) nanosheets exhibit remarkably low onset potential at 1.12 V (vs RHE), outperforming that of NiP, FeP, and CuP around 1.25 V (vs RHE). CoP displays 82% selective formate production, indicating a superior capacity for C-C cleavage and concurrent oxidation; this property could be utilized to valorize larger molecules. CoP also exhibits highly sustainable electrochemical stability for a continuous 200 h GLYOR operation, yielding 6.5 L of H2 production with a 4 cm2 electrode and 98 ± 0.5% Faradaic efficiency. The present study advances our understanding of efficient GLYOR catalysts and underscores the potential of sustainable and economically viable green hydrogen production methodologies.

Perspectives on the highly selective oxidation of copper-mediated C3N4-BiVO4 organic-inorganic hybrid catalysts and the efficient generation of reactive oxygen species

Singlet oxygen (1O2) is a kind of reactive oxygen species (ROS) with both oxidizability and selectivity. The construction of 1O2 is the key to improve the selectivity of various organic reactions. In this study, Cu/C3N4-BiVO4 (CCN-BVO) ternary system significantly improved the catalytic effect of selective oxidation of glycerol to prepare high value chemical dihydroxyacetone (DHA). At the same time, CCN-BVO also has a strong environmental catalytic effect, and the decomposition effect of liquid phase organic pollutants can reach more than 90 % within 2 h. The superior ROS production capacity of CCN-BVO, particularly its ability to produce 1O2, has been confirmed by electron spin resonance (ESR) and quenching experiments as the reason for its excellent catalytic effect. Electrochemical characterization and X-ray photoelectron spectroscopy (XPS) proved that Cu can be used as an intermediary to accelerate electron conduction, and can also effectively construct defects to improve oxygen absorption efficiency, thus effectively increasing ROS yield. This study also theoretically confirmed the reaction path of glycerol catalysis through DFT calculation, which provided a theoretical basis for the subsequent design of efficient catalytic materials.

Regulation of the d-band center of metal–organic frameworks for energy-saving hydrogen generation coupled with selective glycerol oxidation

The hybrid electrolyzer coupled glycerol oxidation (GOR) with hydrogen evolution reaction (HER) is fascinating to simultaneously generate H2 and high value-added chemicals with low energy input, yet facing a challenge. Herein, Cu-based metal-organic frameworks (Cu-MOFs) are reported as model catalysts for both HER and GOR through doping of atomically dispersed precious and nonprecious metals. Remarkably, the HER activity of Ru-doped Cu-MOF outperformed a Pt/C catalyst, with its Faradaic efficiency for formate formation at 90% at a low potential of 1.40 V. Furthermore, the hybrid electrolyzer only needed 1.36 V to achieve 10 mA cm-2, 340 mV lower than that for splitting pure water. Theoretical calculations demonstrated that electronic interactions between the host and guest (doped) metals shifted downward the d-band centers (εd) of MOFs. This consequently lowered water adsorption and dissociation energy barriers and optimized hydrogen adsorption energy, leading to significantly enhanced HER activities. Meanwhile, the downshift of εd centers reduced energy barriers for rate-limiting step and the formation energy of OH*, synergistically enhancing the activity of MOFs for GOR. These findings offered an effective means for simultaneous productions of hydrogen fuel and high value-added chemicals using one hybrid electrolyzer with low energy input.

Isolated Iridium Sites on Potassium‐Doped Carbon‐nitride wrapped Tellurium Nanostructures for Enhanced Glycerol Photooxidation

AbstractMany industrial processes such transesterification of fatty acid for biodiesel production, soap manufacturing and biosynthesis of ethanol generate glycerol as a major by‐product that can be used to produce commodity chemicals. Photocatalytic transformation of glycerol is an enticing approach that can exclude the need of harsh oxidants and extraneous thermal energy. However, the product yield and selectivity remain poor due to low absorption and unsymmetrical site distribution on the catalyst surface. Herein, tellurium (Te) nanorods/nanosheets (TeNRs/NSs) wrapped potassium‐doped carbon nitride (KCN) van der Waal (vdW) heterojunction (TeKCN) is designed to enhance charge separation and visible‐NIR absorption. The iridium (Ir) single atom sites decoration on the TeKCN core‐shell structure (TeKCNIr) promotes selective oxidation of glycerol to glyceraldehyde with a conversion of 45.6% and selectivity of 61.6% under AM1.5G irradiation. The catalytic selectivity can reach up to 88% under 450 nm monochromatic light. X‐ray absorption spectroscopy (XAS) demonstrates the presence of undercoordinated IrN2O2 sites which improved catalytic selectivity for glycol oxidation. Band energies and computational calculations reveal faile charge transfer in the TeKCNIr heterostructure. EPR and scavenger tests discern that superoxide (O2•−) and hydroxyl (•OH) radicals are prime components driving glycerol oxidation.

Pulse potential mediated selectivity for the electrocatalytic oxidation of glycerol to glyceric acid

Preventing the deactivation of noble metal-based catalysts due to self-oxidation and poisonous adsorption is a significant challenge in organic electro-oxidation. In this study, we employ a pulsed potential electrolysis strategy for the selective electrocatalytic oxidation of glycerol to glyceric acid over a Pt-based catalyst. In situ Fourier-transform infrared spectroscopy, quasi-in situ X-ray photoelectron spectroscopy, and finite element simulations reveal that the pulsed potential could tailor the catalyst’s oxidation and surface micro-environment. This prevents the overaccumulation of poisoning intermediate species and frees up active sites for the re-adsorption of OH adsorbate and glycerol. The pulsed potential electrolysis strategy results in a higher glyceric acid selectivity (81.8%) than constant-potential electrocatalysis with 0.7 VRHE (37.8%). This work offers an efficient strategy to mitigate the deactivation of noble metal-based electrocatalysts.

Sunlight-driven selective oxidation of glycerol on formate oxidase mimicking AuPt/TiO2

We report selective photocatalytic partial oxidation of glycerol on bimetallic formate oxidase mimicking AuPt/TiO2, with a unique self-accelerating reaction kinetics discovered for the first time. Systematic investigation on the glycerol oxidation in the presence of externally added formic acid and various scavengers reveals a positive correlation between photocatalytic activity and solution H2O2 level. A reaction mechanism has been put forward, where the in situ generated formic acid consumes photogenerated holes, and enables on-site H2O2 production on AuPt/TiO2, resulting in accelerated glycerol oxidation and improved C3 product selectivity. In pH 9 borate buffer solution, C3 products selectivity of 72% (60% for glyceric acid) has been achieved at 90% glycerol conversion under AM 1.5 G irradiation for 4 h, at ambient conditions. Our findings presented here may help guiding catalyst design for the photocatalytic biomass valorization in the future.

Selective Oxidation of Glycerol to Lactic Acid Catalyzed by CuO/Activated Carbon and Reaction Kinetics.

Activated carbon-supported CuO catalysts were prepared by an ammonia evaporation method and applied to catalyze the selective oxidation of glycerol to lactic acid. The effects of CuO loadings on the structure and catalytic performance of the catalyst were investigated. Results showed that CuO could be dispersed uniformly on the surface of activated carbon, promoting the increase of the reaction rate and accelerating the glycerol conversion significantly. As CuO loadings increased, the rate of glycerol consumption and yield to lactic acid was increased. However, too high CuO loadings would destroy the original pore structure of activated carbon and aggravate the agglomeration of CuO, resulting in a decrease in the catalytic performance of the catalyst. The best catalytic performance was obtained over 10% CuO/AC when the reaction temperature was 190 °C and the reaction time was 5 h. At this point, the selectivity to lactic acid reached 92.61%. In addition, power-function type reaction kinetic equations were used to evaluate the effect of glycerol and NaOH concentrations and the reaction temperature on the oxidation of glycerol to lactic acid over 10% CuO/AC. The activation energy of the reaction is 134.39 kJ·mol-1, which is higher than that using single CuO as the catalyst. This indicates that CuO/AC is more temperature-sensitive than CuO and can probably achieve a higher lactic acid yield at high temperatures. At the same time, it is indicated that CuO supported on activated carbon can enhance the catalytic activity of CuO effectively.

Selective Photoelectrochemical Oxidation of Glycerol to Glyceric Acid on (002) Facets Exposed WO3 Nanosheets

AbstractGlycerol is a byproduct of biodiesel production. Selective photoelectrochemical oxidation of glycerol to high value‐added chemicals offers an economical and sustainable approach to transform renewable feedstock as well as store green energy at the same time. In this work, we synthesized monoclinic WO3 nanosheets with exposed (002) facets, which could selectively oxidize glycerol to glyceric acid (GLYA) with a photocurrent density of 1.7 mA cm−2, a 73 % GLYA selectivity and a 39 % GLYA Faradaic efficiency at 0.9 V vs. reversible hydrogen electrode (RHE) under AM 1.5G illumination (100 mW cm−2). Compared to (200) facets exposed WO3, a combination of experiments and theoretical calculations indicates that the superior performance of selective glycerol oxidation mainly originates from the better charge separation and prolonged carrier lifetime resulted from the plenty of surface trapping states, lower energy barrier of the glycerol‐to‐GLYA reaction pathway, more abundant active sites and stronger oxidative ability of photogenerated holes on the (002) facets exposed WO3. Our findings show great potential to significantly contribute to the sustainable and environmentally friendly chemical processes via designing high performance photoelectrochemical cell via facet engineering for renewable feedstock transformation.

Selective Photoelectrochemical Oxidation of Glycerol to Glyceric Acid on (002) Facets Exposed WO3 Nanosheets.

Glycerol is a byproduct of biodiesel production. Selective photoelectrochemical oxidation of glycerol to high value-added chemicals offers an economical and sustainable approach to transform renewable feedstock as well as store green energy at the same time. In this work, we synthesized monoclinic WO3 nanosheets with exposed (002) facets, which could selectively oxidize glycerol to glyceric acid (GLYA) with a photocurrent density of 1.7 mA cm-2 , a 73 % GLYA selectivity and a 39 % GLYA Faradaic efficiency at 0.9 V vs. reversible hydrogen electrode (RHE) under AM 1.5G illumination (100 mW cm-2 ). Compared to (200) facets exposed WO3 , a combination of experiments and theoretical calculations indicates that the superior performance of selective glycerol oxidation mainly originates from the better charge separation and prolonged carrier lifetime resulted from the plenty of surface trapping states, lower energy barrier of the glycerol-to-GLYA reaction pathway, more abundant active sites and stronger oxidative ability of photogenerated holes on the (002) facets exposed WO3 . Our findings show great potential to significantly contribute to the sustainable and environmentally friendly chemical processes via designing high performance photoelectrochemical cell via facet engineering for renewable feedstock transformation.

Vacancy Optimized Coordination on Nickel Oxide for Selective Electrocatalytic Oxidation of Glycerol

Vacancy Optimized Coordination on Nickel Oxide for Selective Electrocatalytic Oxidation of Glycerol