Tailored MgAl2O4 supported Ru catalyst for selective C–O bond cleavage in diphenyl ether hydrogenolysis

The direct cleavage of C−O bonds in lignin and its derivatives via hydrogenolysis is an essential reaction process for lignin conversion. Herein, we design a MgAl2O4 supported Ru catalyst using a facile and green method involving ball milling and microwave heating. The optimal catalyst, 0.5Ru/MgAl2O4, displayed enhanced catalytic performance for 4−O−5 linkage scission compared to 0.5Ru/Al2O3 and 0.5Ru/MgO, achieving a tuenover frequency of 352.9 h−1 for diphenyl ether (DPE) conversion. 0.5Ru/MgAl2O4 with low Ru loading achieved complete conversion of DPE, with 43.8% yield of cyclohexane (CHE) and 42.6% yield of cyclohexanol (CHL) after 2 h at 160 °C and 1.5 MPa H2. The promising catalytic activity can be attributed to the abundant electron-rich Ru0 species with high dispersion formed on MgAl2O4, derived from the strong electron transfer from the support to Ru. The reaction mechanism for the direct cleavage of the 4−O−5 bond, followed by phenyl ring hydrogenation, was confirmed by rigorous experiments. This work provides an inspiring idea for developing efficient heterogeneous catalysts for the utilization of lignin resources via hydrogenolysis

Plasma-enabled catalytic steam reforming of toluene as a biomass tar surrogate: Understanding the synergistic effect of plasma catalysis

In this study, steam reforming of toluene was carried out in a dielectric barrier discharge (DBD) plasma reactor combined with Ni/γ-Al2O3 catalysts. The effect of reaction temperature, calcination temperature of catalysts, and relative permittivity of packing materials, on the reaction performance and synergistic effect of plasma catalysis was investigated. The results showed that toluene conversion decreased initially and then increased with increasing temperature, due to a decreasing average reduced electric field and increasing catalytic activity at higher temperatures. At 450 °C, the process achieved a high toluene conversion of 87.1%, a total gas yield of 72.6%, and an energy efficiency of 18.2 g/kWh, demonstrating the potential of this approach for sustainable hydrogen production. Catalysts prepared at lower calcination temperatures or with higher relative permittivity packing materials perform better, owing to the larger Ni surface area available for catalytic reactions and the higher surface discharge facilitating the occurrence of surface reactions. In addition, the synergistic capacity in terms of toluene conversion and gas production exhibited a positive relationship with the metal surface area of catalysts and the relative permittivity of packing materials, while the relationship between reaction temperature and toluene conversion was negative

Three-Dimensional MoS2/Reduced Graphene Oxide Nanosheets/Graphene Quantum Dots Hybrids for High-Performance Room-Temperature NO2 Gas Sensors

This study presents three-dimensional (3D) MoS2/reduced graphene oxide (rGO)/graphene quantum dots (GQDs) hybrids with improved gas sensing performance for NO2 sensors. GQDs were introduced to prevent the agglomeration of nanosheets during mixing of rGO and MoS2. The resultant MoS2/rGO/GQDs hybrids exhibit a well-defined 3D nanostructure, with a firm connection among components. The prepared MoS2/rGO/GQDs-based sensor exhibits a response of 23.2% toward 50 ppm NO2 at room temperature. Furthermore, when exposed to NO2 gas with a concentration as low as 5 ppm, the prepared sensor retains a response of 15.2%. Compared with the MoS2/rGO nanocomposites, the addition of GQDs improves the sensitivity to 21.1% and 23.2% when the sensor is exposed to 30 and 50 ppm NO2 gas, respectively. Additionally, the MoS2/rGO/GQDs-based sensor exhibits outstanding repeatability and gas selectivity. When exposed to certain typical interference gases, the MoS2/rGO/GQDs-based sensor has over 10 times higher sensitivity toward NO2 than the other gases. This study indicates that MoS2/rGO/GQDs hybrids are potential candidates for the development of NO2 sensors with excellent gas sensitivity

Torrefaction of waste wood-based panels: More understanding from the combination of upgrading and denitrogenation properties

As a type of special biowaste, waste wood-based panels (WWPs) have a high nitrogen content and typical biomass defect properties, which limit their clean and efficient thermal utilization. An upgrading and denitrogenation procedure prior to thermal utilization is necessary, but the relevant mechanisms and characteristics have not been clearly elucidated. Torrefaction pretreatment of three typical WWPs (plywood, fiberboard, particleboard) was conducted to investigate the evolution of carbon and nitrogen functionalities in relation to the upgrading/denitrogenation procedure. The results demonstrated that the combined upgrading/denitrogenation of WWPs was possible. Under optimal operating conditions (300 degrees C and 10 min), the denitrogenation efficiency could reach 60-70 wt% with a slight energy loss of < 30% and a high HHV (20-22 MJ/kg) of the corresponding torrefied products. The carbon functionality evolution (upgrading) was believed to be the continuous change from low-energy "-C-H/-C-O/-C=O" to high-energy "aromatic -C-C/-C=C", which was related to the reactions of lignin (demethoxylation, chain scission and polycondensation), hemicellulose (deacetylation and degradation) and cellulose (degradation). The nitrogen functionality evolution (denitrogenation) was regarded as a conversion of amide-N into more stable heterocyclic-N (pyrrolic-N and pyridinic-N) through cross-linking reactions, together with a significant release of nitrogen containing gases (NH3 and HCN)

Removal of toluene as a biomass tar surrogate by combining catalysis with nonthermal plasma: understanding the processing stability of plasma catalysis

In this study, toluene (tar surrogate) removal under a simulated gasification gas (SGG) atmosphere was conducted by combining DBD plasma with a nickel catalyst. The processing stability of plasma catalysis was investigated in terms of toluene removal and SGG reactions, and some attempts at stability improvement including the addition of H(2)or H2O and K-modification of the catalyst were conducted. The results indicate that plasma exerts great effects on the carbon deposition rate on the plasma-covered catalyst surface to affect the processing stability, and the effect, increasing or to some extent decreasing the carbon deposition rate, depends on the operating conditions and catalysts. In a Ni/gamma-Al(2)O(3)reactor with a SGG atmosphere and H(2)or H2O addition, the higher carbon deposition rate induced by plasma leads to poor stability, while under the high H2O addition amount condition, the activation effect of plasma combined with the H2O/CO(2)adsorption enhancement of K-modified Ni/gamma-Al(2)O(3)prevented the higher carbon deposition rate in the plasma-covered area and hence successfully improved the processing stability

In Situ Growth of COF/PVA-Carrageenan Hydrogel Using the Impregnation Method for the Purpose of Highly Sensitive Ammonia Detection

Flexible ammonia (NH3) gas sensors have gained increasing attention for their potential in medical diagnostics and health monitoring, as they serve as a biomarker for kidney disease. Utilizing the pre-designable and porous properties of covalent organic frameworks (COFs) is an innovative way to address the demand for high-performance NH3 sensing. However, COF particles frequently encounter aggregation, low conductivity, and mechanical rigidity, reducing the effectiveness of portable NH3 detection. To overcome these challenges, we propose a practical approach using polyvinyl alcohol-carrageenan (κPVA) as a template for in the situ growth of two-dimensional COF film and particles to produce a flexible hydrogel gas sensor (COF/κPVA). The synergistic effect of COF and κPVA enhances the gas sensing, water retention, and mechanical properties. The COF/κPVA hydrogel shows a 54.4% response to 1 ppm NH3 with a root mean square error of less than 5% and full recovery compared to the low response and no recovery of bare κPVA. Owing to the dual effects of the COF film and the particles anchoring the water molecules, the COF/κPVA hydrogel remained stable after 70 h in atmospheric conditions, in contrast, the bare κPVA hydrogel was completely dehydrated. Our work might pave the way for highly sensitive hydrogel gas sensors, which have intriguing applications in flexible electronic devices for gas sensing

Microscopies Enabled by Photonic Metamaterials

In recent years, the biosensor research community has made rapid progress in the development of nanostructured materials capable of amplifying the interaction between light and biological matter. A common objective is to concentrate the electromagnetic energy associated with light into nanometer-scale volumes that, in many cases, can extend below the conventional Abb&eacute; diffraction limit. Dating back to the first application of surface plasmon resonance (SPR) for label-free detection of biomolecular interactions, resonant optical structures, including waveguides, ring resonators, and photonic crystals, have proven to be effective conduits for a wide range of optical enhancement effects that include enhanced excitation of photon emitters (such as quantum dots, organic dyes, and fluorescent proteins), enhanced extraction from photon emitters, enhanced optical absorption, and enhanced optical scattering (such as from Raman-scatterers and nanoparticles). The application of photonic metamaterials as a means for enhancing contrast in microscopy is a recent technological development. Through their ability to generate surface-localized and resonantly enhanced electromagnetic fields, photonic metamaterials are an effective surface for magnifying absorption, photon emission, and scattering associated with biological materials while an imaging system records spatial and temporal patterns. By replacing the conventional glass microscope slide with a photonic metamaterial, new forms of contrast and enhanced signal-to-noise are obtained for applications that include cancer diagnostics, infectious disease diagnostics, cell membrane imaging, biomolecular interaction analysis, and drug discovery. This paper will review the current state of the art in which photonic metamaterial surfaces are utilized in the context of microscopy