Search

Ripple effects of solvent on the extracted lignin oligomers and generated LNPs.

Catalytic production of several representative active pharmaceutical ingredients (APIs) from lignin.

Sub-supercritical methanol and the phenol/quinone redox system were combined to promote the conversion of glucose to methyl glycolate.

The photocatalytic activity of TiO2 in the simultaneous photocatalytic oxidation of organic molecules and H2 production is optimized via crystal phase engineering of Ru cocatalysts.

Cs3Bi2Br9 decorated with crystalline-amorphous Pd nanocubes as cocatalysts is reported to photocatalytically coproduce ca. 1400 μmol h−1 g−1 of H2 and benzaldehyde from the selective benzyl alcohol oxidation. This route offers an alternative for photocatalytic H2 generation using metal halide perovskites under mild conditions.

Bearing plays an important role in industrial equipment and it may operate under varying conditions. When the speed of shaft changes, whether monotonous or non-monotonous speed, common diagnostic approaches cannot effectively extract fault features. But encoders and tachometers are not always available. Therefore, tacholess order tracking methods which can directly extract the instantaneous rotating frequency (IRF) from vibration signal are very useful in bearing fault diagnosis under varying speed. Among these methods, the generalized linear chirplet transform (GLCT) can produce time-frequency representation without constructing any mathematical model, but there are two parameters must be set in advance. The parameters have great influence on the analysis result. To reduce the dependence on the prior knowledge of presetting the parameters in varying conditions, two different improved GLCT methods are proposed in this paper. To do with the situation where the trend of speed changes is monotonous, the scale-space is introduced to lift GLCT which can adaptively set a vital parameter, and the other parameter is set to default value. When faced with non-monotonous speed, the second method is proposed which the grey wolf optimizer (GWO) and Gini index are introduced to search the optimal parameters of GLCT without any prior knowledge. With the help of the proposed methods, the IRF can be extracted directly from vibration signal. Then, the raw signal can be resampled based on the IRF to eliminate the influences of speed. The morphological filtering is adopted to remove the noise and extract the fault characteristics order (FCO). Another two typical time-frequency analysis methods are used for comparisons. Three different signals are used for analysis to demonstrate the superiority of the proposed methods.

Crystal phase engineering of metal nano and microparticles is a new and promising route to tune their properties, complementary to their often exploited optimization via size and shape control. Ag microparticles have attracted much attention over the last decades due to their unique properties and their scalability. The colloidal synthesis of allotropic Ag microparticles has already been reported, but detailed knowledge of the synthesis and properties of allotropic Ag microparticles remains limited. In this work, we optimize the formation of hcp Ag via colloidal growth by tuning the chemical reduction kinetics and the surface stabilization through surfactants. The stability of allotropic Ag microparticles was investigated under catalytic conditions. It was shown that hcp Ag microparticles are stable under high pressures of N2, O2 and H2 and in various solvents, but that their thermal stability is limited to 70°C. These new insights on the stability of allotropic Ag microparticles will serve as a starting point to study the catalytic properties of allotropic Ag microparticles. ispartof: New Journal Of Chemistry vol:46 issue:27 status: Published online

Via hydrothermal synthesis of Sn-Al gels, mild dealumination and ion exchange, a bimetallic Sn-Ni-Beta catalyst was prepared which can convert glucose to methyl lactate (MLA) and methyl vinyl glycolate (MVG) in methanol at yields of 71.2 % and 10.2 %, respectively. Results from solid-state magic-angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy, transmission electron microscopy, spectroscopic analysis, probe-temperature-programmed desorption, and density functional theory calculations conclusively reveal that the openness of the Sn sites, such as by the formation of [(SiO)

Cs

In the context of a carbon neutral economy, catalytic CO2 hydrogenation to methanol is one crucial technology for CO2 mitigation providing solutions for manufacturing future fuels, chemicals, and materials. However, most of the presently known catalyst systems are used at temperatures over 220 °C, which limits the theoretical yield of methanol production due to the exothermic nature of this transformation. In this review, we summarize state-of-the-art catalysts, focusing on the rationales behind, for CO2 hydrogenation to methanol at temperatures lower than 170 °C. Both hydrogenation with homogeneous and heterogeneous catalysts is covered. Typically, additives (alcohols, amines or aminoalcohols) are used to transform CO2 into intermediates, which can further be reduced into methanol. In the first part, molecular catalysts are discussed, organized into: (1) monofunctional, (2) M/NH bifunctional, and (3) aromatization-dearomatization bifunctional molecular catalysts. In the second part, heterogeneous catalysts are elaborated, organized into: (1) metal/metal or metal/support, (2) active-site/N or active-site/OH bifunctional heterogeneous catalysts, and (3) cooperation of catalysts and additives in a tandem process via crucial intermediates. Although many insights have been gained in this transformation, in particular for molecular catalysts, the mechanisms in the presence of heterogeneous catalysts remain descriptive and insights unclear. ispartof: Chemical Society Reviews vol:50 issue:7 pages:4259-4298 ispartof: location:England status: published

The vibration response of faulty bearing is always characterized by periodic transient impulses in the signal. Generally, these fault-related features are inevitably submerged in noise and harmonic components. Mathematical morphology is an excellent method of noise reduction, which can retain the detail information of impulses in the time domain. However, the filtering effect of traditional morphological operator (MO) might be easily affected by random impulses, and the proper selection of the structure element (SE) depends heavily on the experience of researchers. In order to effectively remove these interferences and extract the fault features accurately, an improved method, named adaptive morphological filter (AMF), is proposed in this article. This method utilizes autocorrelation to lift MO in time domain to enhance periodic components, and the scale of SE can, therefore, be calculated with the local maximum of the autocorrelation spectrum. Since the selection of the optimal SE scale is adaptive, researchers’ experience is no longer needed, and there is also no need to calculate the fault characteristic frequency (FCF) for the determination of maximum scale of SE. The vibration and acoustical signals of faulty locomotive wheel set bearing are analyzed with this method, and the results verify its effectiveness and ability.

Lignin is a potential non-fossil resource of diverse functionalized phenolic units. The most important lignin-derived monomers are 4-alkylphenols, 4-hydroxybenzaldehydes, 4-hydroxybenzoic acids, and 4-hydroxycinnamic acids/esters. Efficient transformation of lignin and/or its monomers into valuable aromatics and their derivatives is crucial, not only for a sustainable lignocellulose biorefinery, but also to reduce our dependence on fossil feedstocks. This review provides a concise account of the recent advances in lignocellulose fractionation/lignin depolymerization processes towards lignin-derived monomers. Subsequently, numerous potential atom-efficient catalytic routes for upgrading lignin monomers into drop-in chemicals and new polymer building blocks are discussed.

The selective conversion of lignin or lignin-derived products into bulk chemicals is the foremost challenge for near-future lignocellulosic biorefineries. This study investigates the production of ...

Every twig and splinter used Plant-based production of commodity chemicals faces steep competition from fossil resources, which are often cheaper and easier to partition. Sustainable use of renewable resources requires strategies for converting complex and recalcitrant biomolecules into streams of chemicals with extraordinary efficiency. Liao et al. developed a biorefinery concept in which wood is eventually fully converted into useful chemicals: phenol, propylene, pulp amenable to ethanol production, and phenolic oligomers that can be incorporated into ink production (see the Perspective by Zhang). A life-cycle assessment and techno-economic analysis highlight the efficiency of the process and reveal the potential for such biorefinery strategies to contribute to sustainable chemicals markets. Science , this issue p. 1385 ; see also p. 1305