Insight into the basic strength-dependent catalytic performance in aqueous phase oxidation of glycerol to glyceric acid

Enhancing polyol/sugar cascade oxidation to formic acid with defect rich MnO2 catalysts

Oxidation of renewable polyol/sugar into formic acid using molecular O₂ over heterogeneous catalysts is still challenging due to the insufficient activation of both O₂ and organic substrates on coordination-saturated metal oxides. In this study, we develop a defective MnO₂ catalyst through a coordination number reduction strategy to enhance the aerobic oxidation of various polyols/sugars to formic acid. Compared to common MnO₂, the tri-coordinated Mn in the defective MnO₂ catalyst displays the electronic reconstruction of surface oxygen charge state and rich surface oxygen vacancies. These oxygen vacancies create more Mn^δ+ Lewis acid site together with nearby oxygen as Lewis base sites. This combined structure behaves much like Frustrated Lewis pairs, serving to facilitate the activation of O₂, as well as C-C and C-H bonds. As a result, the defective MnO₂ catalyst shows high catalytic activity (turnover frequency: 113.5 h^-1) and formic acid yield (>80%) comparable to noble metal catalysts for glycerol oxidation. The catalytic system is further extended to the oxidation of other polyols/sugars to formic acid with excellent catalytic performance.

A multiplatform metabolomics/reactomics approach as a powerful strategy to identify reaction compounds generated during hemicellulose hydrothermal extraction from agro-food biomasses

Hydrothermal treatment is commonly used for hemicelluloses extraction from lignocellulosic materials. In this study, we thoroughly investigated with a novel approach the metabolomics of degradation compounds formed when hazelnut shells are subjected to this type of treatment. Three different complementary techniques were combined, namely GC-MS, ¹H NMR, and UHPLC-IM-Q-TOF-MS. Organic acids, modified sugars and aromatic compounds, likely to be the most abundant chemical classes, were detected and quantified by NMR, whereas GC- and LC-MS-based techniques allowed to detect many molecules with low and higher Mw, respectively. Furans, polyols, N-heterocyclic compounds, aldehydes, ketones, and esters appeared, among others. Ion mobility-based LC-MS method was innovatively used for this purpose and could allow soon to create potentially useful datasets for building specific databases relating to the formation of these compounds in different process conditions and employing different matrices. This could be a very intelligent approach especially in a risk assessment perspective.

The Efficiency of Carbon Conversion and Hydrogen Production from Tar Steam Reforming of Biomass Using Ni-Based Catalysts with Alkaline Earth Promoters

H2 production can be used as a clean and renewable energy source for various applications, including fuel cells, internal combustion engines, and chemical production. Using nickel-based catalysts for steam reforming biomass tar presents challenges related to catalyst deactivation, poisoning, heterogeneous composition, high process temperatures, and gas impurities. To overcome these challenges, adopting a nickel-based catalyst with selected oxide support and MgO and CaO promoter is a promising approach for improving the efficiency and sustainability of steam reforming for hydrogen production. The majority of studies conducted to date have focused on the steam reforming of particular tar compounds, most commonly benzene, phenol, toluene, or naphthalene, over a range of support catalysts. However, the actual biomass tar composition is complex, and each component impacts how well steam reforming works. In this research, a multi-compound biomass tar model including phenol, toluene, naphthalene, and pyrene underwent a steam reforming process. Various types with 10 wt.% of nickel-based catalysts were generated by the co-impregnation technique, which included 90 wt.% different oxide supports (Al2O3, La2O3, and ZrO2) and 10 wt.% of combination alkaline oxide earth promoters (MgO and CaO). Thermogravimetric analysis, Brunauer–Emmett–Teller (BET) method, N2 physisorption, temperature-programmed reduction (H2-TPR), temperature-programmed desorption (CO2-TPD), and X-ray diffraction (XRD) of ni-based catalyst characterized physiochemical properties of the prepared catalyst. The reaction temperature used for steam reforming was 800 °C, an S/C ratio of 1, and a GHSV of 13,500 h−1. Ni/La2O3/MgO/CaO (NiLaMgCa) produced the most carbon to-gas conversion (86.27 mol%) and H2 yield (51.58 mol%) after 5 h of reaction compared to other catalysts tested in this study. Additionally, the filamentous carbon coke deposited on the spent catalyst of NiLaMgCa does not impact the catalyst activity. NiLaMgCa was the best catalyst compared to other catalysts investigated, exhibiting a stable and high catalytic performance in the steam reforming of gasified biomass tar. In conclusion, this study presents a novel approach by adding a combination of MgO and CaO promoters to a ni-based catalyst with various oxide supports, strengthening the metal-support interaction and improving the acid-base balance of the catalyst surface. The mesoporous structure and active phase (metallic Ni) were successfully developed. This can lead to an increase in the conversion of tar to H2 yield gas and a decrease in the production of undesired byproducts, such as CH4 and CO.

Catalytic Oxidation of Glycerol over Pt Supported on MOF-Derived Carbon Nanosheets

A series of nitrogen-doped porous carbon nanosheets (NPCNs) doped with transition-metal-supported Pt catalysts were prepared by colloidal deposition and evaluated for the selective oxidation of glycerol to glyceric acid (GLYA) under nonalkaline conditions. The transition metal contained in the catalyst was found to affect its performance and selectivity for GLYA, with the Pt/Zr@NPCN catalyst showing the highest catalytic activity and selectivity. These materials were characterized using Brunauer-Emmett-Teller surface area analysis, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and CO₂ temperature-programmed desorption. The results showed that the small size of the Pt nanoparticles, the interaction between the Pt nanoparticles and the support, and the unique textural properties of the catalyst all promoted glycerol conversion and GLYA selectivity. A Zr concentration of 1.5 wt % and a support preparation temperature of 800 °C were found to provide a catalyst with the optimal performance that exhibited a glycerol conversion and selectivity for GLYA of 68.62 and 77.29%, respectively, at an initial O₂ pressure of 10 bar and 60 °C after 6 h. Even after being recycled five times, this material provided a GLYA selectivity of approximately 75%, although the glycerol conversion decreased from 68 to 50%. The insights may provide new suggestions on the design of efficient support for the selective oxidation of polyols.

Combined dehydrogenation of glycerol with catalytic transfer hydrogenation of H2 acceptors to chemicals: Opportunities and challenges

Catalytic transformation of low-cost glycerol to value-added lactic acid (LA) is considered as one of the most promising technologies for the upgradation of glycerol into renewable products. Currently, research studies reveal that anaerobic transformation of glycerol to LA could also obtain green H₂ with the same yield of LA. However, the combined value-added utilization of released H₂ with high selectivity of LA during glycerol conversion under mild conditions still remains a grand challenge. In this perspective, for the first time, we conducted a comprehensive and critical discussion on current strategies for combined one-pot/tandem dehydrogenation of glycerol to LA with catalytic transfer hydrogenation of H₂ acceptors (such as CO₂) to other chemicals. The aim of this overview was to provide a general guidance on the atomic economic reaction pathway for upgrading low-cost glycerol and CO₂ to LA as well as other chemicals.

PO4 3- Coordinated Robust Single-Atom Platinum Catalyst for Selective Polyol Oxidation

Achieving efficient catalytic conversion over a heterogeneous catalyst with excellent resistance against leaching is still a grand challenge for sustainable chemical synthesis in aqueous solution. Herein, we devised a single-atom Pt₁ /hydroxyapatite (HAP) catalyst via a simple hydrothermal strategy. Gratifyingly, this robust Pt₁ /HAP catalyst exhibits remarkable catalytic selectivity and catalyst stability for the selective oxidation of C₂ -C₄ polyols to corresponding primary hydroxy acids. It is found that the Pt-(O-P) linkages with strong electron-withdrawing function of PO₄ ^3- (Pt₁ -OPO₄ ^3- pair active site) not only realize the activation of the C-H bond, but also destabilize the transition state from adsorbed hydroxy acids toward the C-C cleavage, resulting in the sharply increased selectivity of hydroxy acids. Moreover, the strong PO₄ ^3- -coordination effect provides electrostatic stabilization for single-atom Pt, ensuring the highly efficient catalysis of Pt₁ /HAP for over 160 hours with superior leaching resistance.