Highly Selective Production of Acrylic Acid from Glycerol via Two Steps Using Au/CeO₂ Catalysts

Using biomass resources for chemical production can provide more sustainable development in the chemical industry. In this work, acrylic acid was selectively produced from glycerol via two steps: Glycerol was efficiently converted to allyl alcohol by formic acid-mediated deoxydehydration (DODH), and then, the obtained allyl alcohol was oxidized without purification into acrylic acid in a basic aqueous solution. The Au/CeO₂ catalysts were used for the selective oxidation, and it worked well even in the presence of residual formic acid and impurities. A high yield of 87% was obtained for the production of acrylic acid from glycerol: 94.5% from glycerol to allyl alcohol and 92% from allyl alcohol to acrylic acid. The different shapes of CeO₂ such as rods, octahedra, and cubes were used as supports to deposit the Au active phase. Au deposited on octahedral CeO₂ presented the highest yield toward acrylic acid, and it was the most stable for the repeated oxidations. The effects of reaction time, temperature, O₂ pressure, and allyl alcohol concentration were evaluated to maximize the yield toward acrylic acid

Atomically Dispersed Platinum on Gold Nano-Octahedra with High Catalytic Activity on Formic Acid Oxidation

Platinum was epitaxially deposited on gold octahedral nanocrystals using an electrochemical method. The coverage of platinum on the gold surface was finely controlled from fully covered multiple overlayers (5 monolayers; denoted as ML) to atomically dispersed submonolayer (0.05 ML). Catalytic activity for formic acid oxidation increased significantly (0.52 A/mg_Pt for 5 ML to 62.6 A/mg_Pt for 0.05 ML) with decreasing coverage. This high activity resulted from the control of the reaction pathway toward direct oxidation producing no surface-poisoning species, induced by the absence of platinum ensembles and the bifunctional effect from neighboring Pt–Au sites. The distribution of atomically dispersed platinum was further confirmed by no activity for methanol oxidation, which necessitates platinum ensembles. This result exemplifies that a rational design of the catalyst nanostructure can lead to contrasting activities with the same catalyst, unprecedentedly high activity for formic acid oxidation vs no activity for methanol oxidation

Surface Plasmon Aided Ethanol Dehydrogenation Using Ag–Ni Binary Nanoparticles

Plasmonic metal nanoparticles absorb light energy and release the energy through radiative or nonradiative channels. Surface catalytic reactions take advantage of the nonradiative energy relaxation of plasmons with enhanced activity. Particularly, binary nanoparticles are interesting because diverse integration is possible, consisting of a plasmonic part and a catalytic part. Herein, we demonstrated ethanol dehydrogenation under light irradiation using Ag–Ni binary nanoparticles with different shapes, snowman and core–shell, as plasmonic catalysts. The surface plasmon formed in the Ag part enhanced the surface catalytic reaction that occurred at the Ni part, and the shape of the nanoparticles affected the extent of the enhancement. The surface plasmon compensated the thermal energy required to trigger the catalytic reaction. The absorbed light energy was transferred to the catalytic part by the surface plasmon through the nonradiative hot electrons. The effective energy barrier was greatly reduced from 41.6 kJ/mol for the Ni catalyst to 25.5 kJ/mol for the core–shell nanoparticles and 22.3 kJ/mol for the snowman-shaped nanoparticles. These findings can be helpful in designing effective plasmonic catalysts for other thermally driven surface reactions

Support Effects in Single-Atom Platinum Catalysts for Electrochemical Oxygen Reduction

Single-atom catalysts (SACs) provide an ideal platform for reducing noble-metal usage. SACs also exhibit unusual catalytic properties due to the absence of a metal surface. The role of the support may have a significant effect on the catalytic properties, similar to that of the ligand molecules in homogeneous catalysts. Here, the support effect was demonstrated by preparing a single-atom platinum catalyst on two different supports: titanium carbide (Pt1/TiC) and titanium nitride (Pt1/TiN). The formation of single-atom Pt was confirmed by STEM, EXAFS, and in situ IR spectroscopy. Pt1/TiC showed higher activity, selectivity, and stability for electrochemical H₂O₂ production than Pt1/TiN. Density functional theory calculations presented that oxygen species have strong affinity into Pt1/TiN, possibly acting as surface poisoning species, and Pt1/TiC preserves oxygen–oxygen bonds more with higher selectivity toward H₂O₂ production. This work clearly shows that the support in SACs actively participates in the surface reaction and does not just act as anchoring sites for single atoms

Effects of miR-494 on the insulin signaling pathway.

<p>The mimic form of miR-494 was overexpressed in cells. Cells were starved for 4 h before treatment with 0, 10, 100 nM of insulin for 20 min, and the levels of p-Akt (Ser473 and Thr308), p-AS160, p-p70S6K, and p-GSK-3α/β were measured in C₂C₁₂ myoblasts (A) and CHO_IR/IRS-1 cells (D). Bars show densitometric quantitation of phosphorylations of Akt, GSK-3α/β, AS160 and p70S6K in C₂C₁₂ myoblasts (B) and CHO_IR/IRS-1 cells (E). (C) The level of p-IRS1 (Tyr608) was measured in insulin-treated C₂C₁₂ myoblasts. GAPDH and actin were used as loading controls. Levels of phospho-proteins between miR-494 transfected cells and control were compared at each concentration of insulin. The values are expressed as the means ± SEM. *P<0.05; **,P<0.01. (F) RT-PCR analysis of genes regulated by miR-494. Total RNA from cells transfected with miR-494-mimic or ASO was prepared from C₂C₁₂ cells and subjected to reverse transcription and PCR. The three lanes represent the same sample with triplicate loading. Fold induction indicates the ratio of expression levels of mRNA in mimic- or ASO-transfected cells compared to control. The glyceraldehyde-3-phosphate dehydrogenase gene (Gapdh) was used as a loading control.</p

Effects of miR-494 on the inflammatory signaling.

<p>C₂C₁₂ myoblasts were transfected with miR-494 mimic oligonucleotides. (A) After 48 h of transfection, cells were starved and then treated with TNF-α at the indicated time and dose. Cell lysates were subjected to immunoblot analysis with antibodies to phospho-NF-κB and IκB. (B) Bars show densitometric quantitation of phosphorylations of NF-κB and IκB. </p

Selective Activation of Methane on Single-Atom Catalyst of Rhodium Dispersed on Zirconia for Direct Conversion

Direct methane conversion into value-added products has become increasingly important. Because of inertness of methane, cleaving the first C–H bond has been very difficult, requiring high reaction temperature on the heterogeneous catalysts. Once the first C–H bond becomes activated, the remaining C–H bonds are successively dissociated on the metal surface, hindering the direct methane conversion into chemicals. Here, a single-atom Rh catalyst dispersed on ZrO₂ surface has been synthesized and used for selective activation of methane. The Rh single atomic nature was confirmed by extended X-ray fine structure analysis, electron microscopy images, and diffuse reflectance infrared Fourier transform spectroscopy. A model of the single-atom Rh/ZrO₂ catalyst was constructed by density functional theory calculations, and it was shown that CH₃ intermediates can be energetically stabilized on the single-atom catalyst. The direct conversion of methane was performed using H₂O₂ in the aqueous solution or using O₂ in gas phase as oxidants. Whereas Rh nanoparticles produced CO₂ only, the single-atom Rh catalyst produced methanol in aqueous phase or ethane in gas phase

MicroRNA-494, Upregulated by Tumor Necrosis Factor-α, Desensitizes Insulin Effect in C₂C₁₂ Muscle Cells

<div><p>Chronic inflammation is fundamental for the induction of insulin resistance in the muscle tissue of vertebrates. Although several miRNAs are thought to be involved in the development of insulin resistance, the role of miRNAs in the association between inflammation and insulin resistance in muscle tissue is poorly understood. Herein, we investigated the aberrant expression of miRNAs by conducting miRNA microarray analysis of TNF-α-treated mouse C₂C₁₂ myotubes. We identified two miRNAs that were upregulated and six that were downregulated by a >1.5-fold change compared to normal cells. Among the findings, qRT-PCR analysis confirmed that miR-494 is consistently upregulated by TNF-α-induced inflammation. Overexpression of miR-494 in CHO_IR/IRS1 and C₂C₁₂ myoblasts suppressed insulin action by down-regulating phosphorylations of GSK-3α/β, AS160 and p70S6K, downstream of Akt. Moreover, overexpression of miR-494 did not regulate TNF-α-mediated inflammation . Among genes bearing the seed site for miR-494, RT-PCR analysis showed that the expression of <i>Stxbp5</i>, an inhibitor of glucose transport, was downregulated following miR-494 inhibition. In contrast, the expression of PTEN decreased in the cells analyzed, thus showing that both positive and negative regulators of insulin action may be simultaneously controlled by miR-494. To investigate the overall effect of miR-494 on insulin signaling, we performed a PCR array analysis containing 84 genes related to the insulin signaling pathway, and we observed that 25% of genes were downregulated (P<0.05) and 11% were upregulated (P<0.05). These results confirm that miR-494 might contribute to insulin sensitivity by positive and negative regulation of the expression of diverse genes. Of note, PCR array data showed downregulation of <i>Slc2A4</i>, a coding gene for Glut4. Altogether, the present study concludes that the upregulation of miR-494 expression by TNF-α-mediated inflammation exacerbates insulin resistance. Therefore, we suggest that miR-494 could prove an important target for the diagnosis and therapy of inflammation-mediated insulin resistance in muscle.</p> </div

qRT-PCR analysis of miRNAs dysregulated in TNF-α treated C₂C₁₂ myotubes.

<p>Cells were treated with 2 or 20 ng/ml of TNF-α for 2 h or 4 days and the expression of miR-494, miR-690, miR-101b, miR-467b, miR-467f and miR-331 was measured by qRT-PCR. U6 RNA was used as a normalization control. The values are expressed as the means ± SEM. *,P<0.05; **,P<0.01; ***,P<0.001 versus vehicle-treated control. </p

Regulation of genes related to the insulin signaling pathway by miR-494.

<p>(A) The sequences of mature form of miR-494 were compared between species. The sequences of miR-494 were obtained from miRbase (release 20; <a href="http://mirbase.org" target="_blank">miRbase.org</a>). (B) Human HeLa cells were overexpressed with the mimic form of miR-494. Cells were starved for 4 h before treatment with 100 nM of insulin for 20 min. The levels of p-Akt (Ser473 and Thr308), p-AS160, p-p70S6K, and p-GSK-3α/β were measured (C). Bars show densitometric quantitation of phosphorylations of Akt, GSK-3α/β, AS160 and p70S6K. GAPDH and actin were used as loading controls. (C-E) PCR array analysis of genes related to insulin signaling pathway by miR-494 in HeLa cells. Real-time PCR was carried out using Human Insulin Signaling Pathway PCR, after transfection of miR-494-mimic oligonucleotide. (C) Intensity scatter plot comparing the mRNA profiles of miR-494 transfected cells and control cells. The 11 mRNAs that were up- or downregulated more than 1.3-fold are highlighted and labeled. (D) Genes that changed more than 1.5-fold or with significance (P<0.05) were clustered. Gene names are denoted on the left. Fold changes and p-values are denoted on the right side of the panel. (E) The percentages of significantly (P<0.05) up- or downregulated genes are compared to the control in each metabolic category. The number of genes are described inside the bar in each group. (F) RT-PCR analysis was performed in miR-494 mimic transfected HeLa cells for 9 genes; <i>Slc2A4, Slc2A1, Insr, Grb2, Gab1, Ptpn1, Jun</i> and <i>Ldlr</i> with <i>Gapdh</i> as the loading control. The three lanes indicate the same sample with triplicate loading. Fold induction indicates the ratio of expression levels of mRNA in mimic transfected cells compared to control. Gene abbreviations: <i>Slc2A4</i>, solute carrier family 2 member 4; <i>Slc2A1</i>, solute carrier family 2 member 1; <i>Insr</i>, insulin receptor; Grb2, growth factor receptor-bound protein 2; <i>Gab1</i>, Grb2-associated binding protein 1; <i>Ptpn1</i>, protein tyrosine phosphatase, non-receptor type 1; <i>Jun</i>, jun proto-oncogene and <i>Ldlr</i>, low density lipoprotein receptor. (G) Immunoblot analysis of Glut1 and Glut4 was performed in miR-494 mimic transfected HeLa cells. GAPDH was used as a loading control.</p