Selective Oxidation Of Glycerol Research Articles

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.

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

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

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

Oxidation of glycerol to dihydroxyacetone over highly stable Au catalysts supported on mineral-derived CuO-ZnO mixed oxide

Selective oxidation of glycerol to dihydroxyacetone (DHA) is a promising pathway for glycerol utilization. In order to fabricate a highly stable supported Au catalyst for the reaction, a series of CuO-ZnO mixed oxides derived from different minerals were synthesized. Then, the Au/CuO-ZnO catalysts were prepared by the deposition-precipitation. High yield of DHA (70%) and conversion of glycerol (76%) were obtained over the rosasite-derived Au/CuO-ZnO catalyst. While over the aurichalcite-derived Au/CuO-ZnO catalyst, the yield of DHA was only 20%. By means of XRD, H2-TPR, TEM, XPS, CO2-TPD characterization, it was found that the higher yield of DHA was attributed to the stronger interaction between CuO and ZnO, higher dispersion of Au species, higher content of Au0 and proper amount of surface basic sites. The rosasite-derived Au/CuO-ZnO catalyst also showed good stability and no obvious decrease in reactivity and DHA selectivity could be seen after five recycles. The stable structure of the support not only enhanced the interaction between CuO-ZnO that stabilized the support itself, but also improved the interaction between Au and the support, further stabilizing the particle size and chemical valence of Au.

Photoelectrochemical Glycerol Oxidation Coupled with Hydrogen Production

AbstractThe catalytic oxidation of glycerol, a surplus byproduct of biodiesel, has received increasing attention due to the popular applications of its oxidation products, such as aldehydes, ketones, and carboxylates. Photoelectrochemical (PEC) methods provide a clean and sustainable pathway for glycerol oxidation and upgrading. However, selective oxidation of glycerol is a challenge due to its complex oxidation path, where the cleavage of C−O or C−C bonds at different positions can lead to a variety of products. This concept aims to describe the recent advances in PEC selective glycerol oxidation for the preparation of multiple high value‐added products, and discuss the reaction mechanism and selective production strategies in detail. Finally, the remaining challenges and future prospects for the PEC glycerol oxidation system are presented.

Glycerol selective oxidation to lactic acid over platinum–vanadium bimetallic catalysts supported on activated carbon

Highly effective bimetallic catalysts for the selective oxidation of glycerol to lactic acid.

Recent advances in the selective oxidation of glycerol to value-added chemicals via photocatalysis/photoelectrocatalysis

This work summarizes a review on the selective oxidation of glycerol via photocatalysis/photoelectrocatalysis. We elucidate the unique reaction pathways induced by photo-generated reactive species from a green chemistry point of view.

Achieving high selectivity in photoelectrochemical oxidation of glycerol on WO3 nanosheets coupled with TiO2 nanorods arrays

Developing highly efficient photocatalysts for the selective conversion of glycerol into valuable chemicals is of paramount importance. However, achieving the selective oxidation of glycerol to valuable C3 chemicals poses significant challenges. In this study, we employed a two-step hydrothermal method to synthesize a photoelectrochemical (PEC) photocatalyst composed of WO3 nanosheets assembled on TiO2 nanorod arrays. The synergistic interaction between WO3 and TiO2 led to outstanding performance in the selective conversion of glycerol (GLY) into glyceraldehyde (GLD) and 1,3-dihydroxyacetone (DHA). The photocatalyst achieved a selectivity of 61% for GLD and 92% for GLD + DHA, with formation rates of 319 and 160 mmol m-2h−1, respectively. Despite the excellent charge transfer properties of TiO2 nanorods, they displayed suboptimal glycerol conversion rates and tended to oxidize glycerol into lower-value products. The introduction of WO3 nanosheets in the Z-scheme heterojunction improved charge separation, enhanced glycerol adsorption and facilitated the desorption of GLD and DHA, thus improving the selectivity of GLD + DHA. This study unveils a promising approach to efficiently oxidize glycerol and demonstrates the crucial role of catalyst design in achieving selective and high-yield chemical transformations.

Application of nonthermal atmospheric‐pressure plasma irradiation as a new method for noncatalytic liquid‐phase selective oxidation of polyhydric alcohols

AbstractWe have developed a new liquid‐phase noncatalytic selective oxidation of polyhydric alcohols such as glycerol. This method involves the use of a nonthermal atmospheric‐pressure plasma instead of precious‐metal catalysts. We found that noncatalytic selective oxidation of glycerol achieved a conversion comparable to that achieved by gold‐catalyzed oxidation, and the desired glyceric acid, which is a pharmaceutical raw material, was obtained. When the solution pH was changed from strongly alkaline to neutral, the main reaction switched from the one that occurs in the presence of gold catalysts to the one that occurs in the presence of platinum catalysts. These results suggest that the reactive oxygen species generated by nonthermal atmospheric‐pressure plasma irradiation vary depending on the solution pH.

Role of the surface chemistry of carbon xerogel-based supports and Cu catalysts in the oxidation reaction of glycerol

Carbon xerogel with pore size of about 10 nm were obtained using the sol–gel method and applying different thermal treatments. Catalysts were prepared depositing 3 wt% of copper on the xerogel. The catalytic activities of catalysts and supports were evaluated in the selective oxidation of glycerol (GLY). The supports showed good conversion and selectivity to glyceric acid (GA) and lactic acid (LA), with higher preference to GA. For the catalysts, the conversions were slightly higher, and the order of selectivity changed, benefiting the production of LA. Changes in selectivity between supports and catalysts were mainly associated with the different acid-base surface characteristics and the presence of the Cu domains in the catalysts. In the supports, even if the thermal treatment applied modifies the type and content of oxygenated functional groups (OFG) on the surface, predominates a superficial acid character, addressing the selectivity to GA. On the other hand, the basic character of the catalysts due to the Cu presence and the large metallic domain sizes favoured the production of LA. During the recycle test, supports and catalysts showed a decrease in catalytic activity. After three recycles, the catalytic performances of catalysts and supports were similar due to metal leaching.

PtBi Intermetallic Compounds with Enhanced Stability towards Base-Free Selective Oxidation of Glycerol

PtBi Intermetallic Compounds with Enhanced Stability towards Base-Free Selective Oxidation of Glycerol