Tailored Synthesis of Catalytically Active Cerium Oxide for N, N-Dimethylformamide Oxidation.

Cerium oxide nanopowder (CeOx) was prepared using the sol-gel method for the catalytic oxidation of N, N-dimethylformamide (DMF). The phase, specific surface area, morphology, ionic states, and redox properties of the obtained nanocatalyst were systematically characterized using XRD, BET, TEM, EDS, XPS, H2-TPR, and O2-TPO techniques. The results showed that the catalyst had a good crystal structure and spherelike morphology with the aggregation of uniform small grain size. The catalyst showed the presence of more adsorbed oxygen on the catalyst surface. XPS and H2-TPR have confirmed the reduction of Ce4+ species to Ce3+ species. O2-TPR proved the reoxidability of CeOx, playing a key role during DMF oxidation. The catalyst had a reaction rate of 1.44 mol g-1cat s-1 and apparent activation energy of 33.30 ± 3 kJ mol-1. The catalytic performance showed ~82 ± 2% DMF oxidation at 400 °C. This work's overall results demonstrated that reducing Ce4+ to Ce3+ and increasing the amount of adsorbed oxygen provided more suitable active sites for DMF oxidation. Additionally, the catalyst was thermally stable (~86%) after 100 h time-on-stream DMF conversion, which could be a potential catalyst for industrial applications.

A Density Functional Theory and Microkinetic Study of Acetylene Partial Oxidation on the Perfect and Defective Cu2O (111) Surface Models.

The catalytic removal of C2H2 by Cu2O was studied by investigating the adsorption and partial oxidation mechanism of C2H2 on both perfect (stoichiometric) and CuCUS-defective Cu2O (111) surface models using density functional theory calculations. The chemisorption of C2H2 on perfect and defective surface models needs to overcome the energy barrier of 0.70 and 0.81 eV at 0 K. The direct decomposition of C2H2 on both surface models is energy demanding with the energy barrier of 1.92 and 1.62 eV for the perfect and defective surface models, respectively. The H-abstractions of the chemisorbed C2H2 by a series of radicals including H, OH, HO2, CH3, O, and O2 following the Langmuir−Hinshelwood mechanism have been compared. On the perfect Cu2O (111) surface model, the activity order of the adsorbed radicals toward H-abstraction of C2H2 is: OH > O2 > HO2 > O > CH3 > H, while on the defective Cu2O (111) surface model, the activity follows the sequence: O > OH > O2 > HO2 > H > CH3. The CuCUS defect could remarkably facilitate the H-abstraction of C2H2 by O2. The partial oxidation of C2H2 on the Cu2O (111) surface model tends to proceed with the chemisorption process and the following H-abstraction process rather than the direct decomposition process. The reaction of C2H2 H-abstraction by O2 dictates the C2H2 overall reaction rate on the perfect Cu2O (111) surface model and the chemisorption of C2H2 is the rate-determining step on the defective Cu2O (111) surface model. The results of this work could benefit the understanding of the C2H2 reaction on the Cu2O (111) surface and future heterogeneous modeling.

Ab Initio Calculation of Surface Thermochemistry for Popular Solid Transition Metal-Based Species.

This work reports the thermochemistry calculations for solid-phase periodic models of ten popular transition metal-based species. These model structures were refined to stable geometry by geometric optimization along with calculating the thermodynamic properties including enthalpy, entropy, heat capacity at constant pressure, and Gibbs free energy by DMol3 package via first-principles ab initio calculations. The temperature-dependent thermochemistry values were converted to a NASA seven-polynomial format. The behavior of different thermodynamic parameters based on temperature was investigated and their comparative analysis was done. A higher number of atoms tends to show higher thermodynamic values. Moreover, these thermodynamic values agree reasonably well with previously reported experimental and computational values. Metal copper shows higher thermodynamic values as compared to its oxide. The thermodynamic properties of lanthanum-based oxides have been newly calculated through the ab initio method. Amorphous structures reveal higher thermodynamic values compared to their crystalline counterparts. A comparison between different transition metal-based species gives a better understanding of the different crystalline structures and their surface sites. These calculated thermodynamic data and polynomials can be used for a variety of thermodynamic calculations and kinetic modeling.

An efficient and innovative catalytic reactor for VOCs emission control.

Efficient mixing and thermal control are important in the flow reactor for obtaining a high product yield and selectivity. Here, we report a heterogeneous chemical kinetic study of propene oxidation within a newly designed catalytic jet-stirred reactor (CJSR). To better understand the interplay between the catalytic performances and properties, the CuO thin films have been characterized and the adsorbed energies of propene on the adsorbed and lattice oxygen were calculated using density functional theory (DFT) method. Structure and morphology analyses revealed a monoclinic structure with nano-crystallite size and porous microstructure, which is responsible for holding an important quantity of adsorbed oxygen. The residence time inside the flow CJSR (1.12-7.84 s) makes it suitable for kinetic study and gives guidance for scale-up. The kinetic study revealed that using CJSR the reaction rate increases with O2 concentration that is commonly not achievable for catalytic flow tube reactor, whereas the reaction rate tends to increase slightly above 30% of O2 due to the catalyst surface saturation. Moreover, DFT calculations demonstrated that adsorbed oxygen is the most involved oxygen, and it has found that the pathway of producing propene oxide makes the reaction of C3H6 over CuO surface more likely to proceed. Accordingly, these findings revealed that CJSR combined with theoretical calculation is suitable for kinetic study, which can pave the way to investigate the kinetic study of other exhaust gases.

Online study on the co-pyrolysis of coal and corn with vacuum ultraviolet photoionization mass spectrometry.

With the aim to support the experimental tests in a circulating fluidized bed pilot plant, the pyrolysis processes of coal, corn, and coal-corn blend have been studied with an online pyrolysis photoionization time-of-flight mass spectrometry (Py-PI-TOFMS). The mass spectra at different temperatures (300-800°C) as well as time-evolved profiles of selected species were measured. The pyrolysis products such as alkanes, alkenes, phenols, aromatics, as well as nitrogen- and sulfur-containing species were detected. As temperature rises, the relative ion intensities of high molecular weight products tend to decrease, while those of aromatics increase significantly. During the co-pyrolysis, coal can promote the reaction temperature of cellulose in corn. Time-evolved profiles demonstrate that coal can affect pyrolysis rate of cellulose, hemicellulose, and lignin of corn in blend. This work shows that Py-PI-TOFMS is a powerful approach to permit a better understanding of the mechanisms underlying the co-pyrolysis of coal and biomass.

Synthesis and In Vitro Anti-Influenza Virus Evaluation of Novel Sialic Acid (C-5 and C-9)-Pentacyclic Triterpene Derivatives.

The emergence of drug resistant variants of the influenza virus has led to a great need to identify novel and effective antiviral agents. In our previous study, a series of sialic acid (C-2 and C-4)-pentacyclic triterpene conjugates have been synthesized, and a five-fold more potent antiviral activity was observed when sialic acid was conjugated with pentacyclic triterpene via C-4 than C-2. It was here that we further reported the synthesis and anti-influenza activity of novel sialic acid (C-5 and C-9)-pentacyclic triterpene conjugates. Their structures were confirmed by ESI-HRMS, ¹H-NMR, and 13C-NMR spectroscopic analyses. Two conjugates (26 and 42) showed strong cytotoxicity to MDCK cells in the CellTiter-Glo assay at a concentration of 100 µM. However, they showed no significant cytotoxicity to HL-60, Hela, and A549 cell lines in MTT assay under the concentration of 10 µM (except compound 42 showed weak cytotoxicity to HL-60 cell line (10 µM, ~53%)). Compounds 20, 28, 36, and 44 displayed weak potency to influenza A/WSN/33 (H1N1) virus (100 µM, ~20-30%), and no significant anti-influenza activity was found for the other conjugates. The data suggested that both the C-5 acetylamide and C-9 hydroxy of sialic acid were important for its binding with hemagglutinin during viral entry into host cells, while C-4 and C-2 hydroxy were not critical for the binding process and could be replaced with hydrophobic moieties. The research presented herein had significant implications for the design of novel antiviral inhibitors based on a sialic acid scaffold.

[Distribution and assessment of mercury in the ambient soil of a municipal solid waste incinerator].

The emission of mercury (Hg) from the municipal solid waste incineration has inspired widespread attention, especially regarding to the deposition of Hg in the surrounding soil, which is issued to be the potential negative factor of ambient environment and human health. This study mainly focused on the distributions of Hg in the ambient soil of a municipal solid waste incinerator located in North China. The pollution of the mercury and its risks to the local environment and human health were assessed. Results showed that Hg levels were in the range of 0.015-0.25 mg x kg(-1), with an average (0.088 +/- 0.064) mg x kg(-1). The concentrations of Hg in the soil were obviously influenced by wind direction and they were relatively higher in the northwest (downwind) comparing with that in the southeast (upwind). The Kriging interpolation method was adopted to create a contour map, which intuitively displayed a spatial mercury distribution in the soil. The regions with a higher Hg concentration are mainly distributed in the north northwest, the north northeast and the west southwest of the municipal solid waste incinerator. According to the evaluation results of single factor pollution index and geoaccumulation Index, some ambient soil samples were polluted by the mercury emission from the municipal solid waste incinerator; however, the results of the health risk assessment showed that the mercury in the soil had not pose a health hazard to the local population.