Phosgene-Free Method for Diphenyl Carbonate Synthesis at the Pd⁰/Ketjenblack Anode

Electrocarbonylation of phenol (PhOH) with CO to diphenyl carbonate (DPC) at a Pd⁰-supported Ketjenblack electrocatalyst (Pd/KB) was studied at <i>P</i>(CO) = 1 atm and 25 °C. Electrocarbonylation was conducted by galvanostatic electrolysis at 1 mA in an electrolyte containing PhOH, sodium phenoxide (PhONa), LiCl, and CH₃CN. The electrocatalytic activity of DPC formation was strongly affected by the reduction temperature of a PdCl₂/KB electrocatalyst with H₂. The Pd/KB electrocatalyst reduced at 393 K showed the highest electrocatalytic activity, while that reduced at 673 K showed less activity. Pd/KB was characterized by X-ray diffraction, transmission electron microscopy–energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Pd particle sizes are strongly related to the electrocatalytic activity of DPC formation. Pd⁰ particles less than 2 nm were active, whereas those greater than 6 nm were inactive. To reveal the electrocarbonylation mechanism, electrocarbonylations using <i>p</i>-cresol, <i>p</i>-chlorophenol, and sodium phenoxides were studied. Cyclic voltammetry studies were conducted using a palladiumized palladium-wire electrode. These results strongly indicated that sodium phenoxides did not incorporate into diaromatic carbonates and also functioned as proton acceptors during electrocarbonylation

Seed-Assisted Synthesis of Crystalline Mo₃VO_<i>x</i> Oxides and Their Crystal Formation Mechanism

The effects of the addition of crystalline Mo₃VO_<i>x</i> oxides (MoVO) seeds on an assembly of pentagonal [Mo₆O₂₁]^6– building units with Mo and V octahedra for forming MoVO were investigated. In the absence of the seeds, the crystal phase of formed MoVO depended on the pH of the preparative solution, while the crystal phase of the formed MoVO was decided by the phase of the MoVO seeds used irrespective of the pH. Interestingly, MoVO were formed even in the pH condition where no crystals were formed in the absence of the seeds. It was shown by X-ray diffraction, scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy, and scanning electron microscopy that MoVO crystals were grown from the cross-section of the rod-shaped crystals of the MoVO seeds

Preparation, Structural Characterization, and Ion-Exchange Properties of Two New Zeolite-like 3D Frameworks Constructed by ε‑Keggin-Type Polyoxometalates with Binding Metal Ions, H_11.4[ZnMo₁₂O₄₀Zn₂]^1.5– and H_7.5[Mn_0.2Mo₁₂O₄₀Mn₂]^2.1–

Two new ε-Keggin-type polyoxometalate-based 3D frameworks, Na_1.5H_11.4[ε-Zn^IIMo^V_10.9Mo^VI_1.1O₄₀{Zn^II}₂] and (NH₄)_2.1H_7.5[ε-Mn^II_0.2Mo^V₆Mo^VI₆O₄₀{Mn^II}₂], are prepared, and their structures are determined by powder X-ray diffraction, Fourier transform infrared, Raman spectroscopy, and elemental analysis. ε-Keggin-type polyoxomolybdate units, [ε-ZnMo₁₂O₄₀] and [ε-Mn_0.2Mo₁₂O₄₀], are linked with Zn²⁺ and Mn²⁺, respectively, in a tetrahedral fashion to form 3D frameworks. They show zeolite-like ion-exchange properties and redox properties. The ε-Keggin-based 3D framework shows high chemical composition diversity and can incorporate different elements in the framework

Synthesis of Novel Orthorhombic Mo and V Based Complex Oxides Coordinating Alkylammonium Cation in Its Heptagonal Channel and Their Application as a Catalyst

The effects of several alkylammonium cations on the synthesis of orthorhombic Mo₃VO_11.2 complex oxides (MoVO) were investigated. First, we synthesized various alkylammonium isopolymolybdates as precursors for the synthesis of MoVO. Methylammonium heptamolybdate, dimethylammonium trimolybdate, ethylammonium trimolybdate, and ethylenediammonium trimolybdate were obtained as pure materials in new crystalline structures. Orthorhombic MoVO complex oxides were synthesized under hydrothermal conditions when (CH₃NH₃)₆Mo₇O₂₄ and ((CH₃)₂NH₂)₂Mo₃O₁₀·H₂O were used. It was found for the first case that methylammonium cations and dimethylammonium cations were incorporated into the orthorhombic MoVO structure, forming compounds of Mo_32.3V_7.7O₁₁₂(CH₃NH₃)_4.0·9.7H₂O and Mo_30.2V_9.8O₁₁₂((CH₃)₂NH₂)_2.5·8.5H₂O, respectively. These alkylammonium cations play an important role as a stabilizer in the synthesis of MoVO and act as a structure-directing agent for the orthorhombic phase

Synthesis of crystalline Mo–V–W–O complex oxides with orthorhombic and trigonal structures and their application as catalysts

<p>Crystalline Mo–V–W–O complex oxides with the orthorhombic or trigonal structure were synthesized by a hydrothermal method. Those Mo–V–W–O samples with various amounts of tungsten were characterized by inductively coupled plasma atomic emission spectroscopy, TEM, STEM–EDX, X-ray diffraction, Rietveld analysis, and a N₂ adsorption method. It was found for the first case that an additional metal such as W can be successfully incorporated into the trigonal Mo–V–O structure by using (CH₃CH₂NH₃)₂Mo₃O₁₀.The alkylammonium cation acted as a structural stabilizer that was requisite for the formation of a trigonal structure when additional metal ions were present. For the orthorhombic Mo–V–W–O structure, introduction of W into the orthorhombic structure caused a rod segregation effect by which nanoscale crystals formed and the external surface area greatly increased. Additionally, these Mo–V–W–O materials were applied as catalysts for the gas phase selective oxidation of acrolein to acrylic acid. The best catalyst was assigned to the orthorhombic Mo–V–O–W7.5, which possessed an ordered arrangement of heptagonal and hexagonal channels and a large external surface area.</p

Transesterification of Ethyl-10-undecenoate Using a Cu-Deposited V₂O₅ Catalyst as a Model Reaction for Efficient Conversion of Plant Oils to Monomers and Fine Chemicals

Transesterification of ethyl-10-undecenoate (derived from castor oil) with 1,4-cyclohexanedimethanol over a recyclable Cu-deposited V2O5 catalyst afforded 1,ω-diene, the corresponding cyclohexane-1,4-diylbis­(methylene) bis­(undec-10-enoate), a promising monomer for the synthesis of biobased polyesters, in an efficient manner. Deposition of Cu plays an important role in proceeding the reaction with high selectivity, and both the activity and the selectivity are preserved for five recycled runs by the addition of the substrates. The present catalyst was effective for transesterification with other alcohols, especially primary alcohols, demonstrating a possibility of using this catalyst for efficient conversion of plant oil to various fine chemicals

Long-Alkyl-Chain Phosphonium Surfactant Molecular Wrapping to Block Oxygen Impurities in n‑Type Carbon Nanotubes for Thermoelectric Applications

In several electronics applications, the instability of components containing n-type carbon nanotubes (CNTs) to atmospheric oxidation in harsh environments or high temperatures is a significant concern. Here, we reported that a dense molecular wrapping of n-type CNTs with phosphonium salts reduced the exposed CNT surface by 79% and suppressed the electrophilic reaction of oxygen on the CNT surface. After aging at 353 K for 28 days, 89% of its initial thermoelectric power factor was retained (290.3 μW m–1 K–2). This opens new avenues for the use of n-type materials in high-temperature electronics

Tetrahedral Connection of ε‑Keggin-type Polyoxometalates To Form an All-Inorganic Octahedral Molecular Sieve with an Intrinsic 3D Pore System

A new type of polyoxometalate-based porous material was successfully synthesized. The new material is the first fully inorganic Keggin-type polyoxometalate-based microporous material with intrinsically ordered open micropores and is the third member of the small family of octahedral molecular sieves (OMSs). Twelve MoO₆ or VO₆ octahedra surround a central VO₄ tetrahedron to form ε-Keggin polyoxometalate building blocks (ε-VMo_9.4V_2.6O₄₀) that are linked by Bi^III ions to form crystalline Mo–V–Bi oxide with a diamondoid topology. The presence of a tetrahedral shape of the ε-Keggin polyoxometalate building block results in arrangement of microporosity in a tetrahedral fashion which is new in OMSs. Owing to its microporosity, this Mo–V–Bi oxide shows zeolitic-like properties such as ion-exchange and molecule adsorption

Understanding the Distinct Effects of Ag Nanoparticles and Highly Dispersed Ag Species on N₂ Selectivity in NH₃–SCO Reaction

Ag-based catalysts, especially Ag/Al2O3, show high NH3 oxidation activity in NH3-selective catalytic oxidation (NH3–SCO). However, the low N2 selectivity limits their further application. To improve N2 selectivity, herein, a series of Ag/Al2O3-X catalysts (X = calcination temperature) are designed by simple calcination. Only Ag nanoparticles (Ag NPs) were observed on the Ag/Al2O3-400 catalyst, while highly dispersed Ag species (Ag HDs) were dominated on the Ag/Al2O3-800 catalyst. NH3–SCO results showed that Ag NPs/Al2O3 forms much N2O by-products, whereas Ag HDs/Al2O3 achieves >99% N2 selectivity over the Ag/Al2O3-800 catalyst at <200 °C. More importantly, various intermediates (NO3 ads, NH2 ads, NN–M, and NN–O–M) and their internal transformations were detected, and the reaction pathways for the formation of N2O and N2 are evidenced by in situ NH3-Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). This study not only provides a convenient and effective approach to obtain excellent N2 selectivity in NH3–SCO but also affords a systematic insight into the reaction pathways over Ag/Al2O3 catalysts