Highly efficient Friedel-Crafts acylation of veratrole over TiO2-SnOx solid solution catalyst

Production of renewable toluene from biomass-derived furans via Diels-Alder and dehydration reactions: A comparative study of Lewis acid catalysts

A family of gyroidal metal-organic frameworks composited with transition-metal ions and bi-imidazolate ligands (BIm) was prepared and used as both Lewis base and acid catalysts. Benefiting from the intrinsic basicity of the ligands and the Lewis acidic sites of the open metal centers, the frameworks show excellent catalytic activities as Lewis base for the Knoevenagel condensation reaction between various aldehydes and malononitrile, and as Lewis acid for cyanosilylation reactions, providing advanced materials for both Lewis base and Lewis acid catalysis. More information can be found in the Full Paper by Xiao-Ping Zhou, Tianfeng Chen, Dan Li et al. on page 3682 in Issue 20, 2019 (DOI: 10.1002/asia.201900853).

Application of activated bentonite impregnated with PdO as green catalyst for acylation reaction of aromatic compounds

Sol–gel preparation of TiO 2–ZrO 2 thin films supported on glass rings: Influence of phase composition on photocatalytic activity

Eighteen binary metal oxides consisting of TiO2–MmOn, ZnO–MmOn and Al2O3–MmOn (MmOn: metal oxide) were prepared by the usual co-precipitation method, their acid amounts and strengths being determined by n-butylamine titration using various acid-base indicators. The acid strengths of fourteen of the tested binary oxides of molar ratio 1 : 1 were found to be remarkably higher than those of the component single oxides. High acid strengths were as follows: H0≤−8.2 for TiO2–SiO2, H0≤−5.6 for TiO2–Al2O3 and Al2O3–ZrO2 and H0≤−3 for TiO2–CdO, TiO2–SnO2 and ZnO–SiO2. The acid amounts of sixteen binary oxides were larger than those of the component oxides. The effect of the composition of binary oxides on acidity was examined for TiO2–Al2O3, ZnO–Al2O3 and Al2O3–ZrO2. The acidity maxima appearing for TiO2–Al2O3 and ZnO–Al2O3 were found to be of molar ratio\simeq9:1 and for Al2O3–ZrO2\simeq3:2. A fairly good correlation has been demonstrated between the observed highest acid strengths and the average electronegativities of metal ions of binary oxides.

Phase-vanishing (PV) method was applied to Friedel-Crafts acylations of aromatic compounds with tin tetrachloride as a Lewis acid. The reaction proceeded smoothly and acylation products were obtained in good yield. Parallel, four different Friedel-Crafts acylation reactions were carried out successfully based on the present PV method.

Highly volatile dimethylamine vapour sensing studies using titanium-vanadium mixed oxide thin films

Major intrinsic causes of cathode degradation in Li-ion batteries include instability against irreversible phase transformations, for example, layered to spinel transformation in LiMO2 type cathodes, and dissolution of the redox-active transition metal ions into the electrolyte. Corrosive species are known to attack the cathode particles and accelerate transition metal dissolution, which often leads to a significant capacity loss upon cycling. Hydrofluoric acid (HF), for example, forms in the presence of only trace amount of water in the common LiPF6 based electrolytes. A strong correlation was observed between HF content in the electrolyte and transition metal loss for common battery cathode materials including the layered LiCoO2, spinel LiMn2O4 and similar cathodes. For LiMn2O4, in particular, disproportionation of surface Mn3+ to Mn2+ and Mn4+, and subsequent dissolution of Mn2+ into the electrolyte is triggered by the H+ ion (that is, acidic environments), and is a primary reason for capacity fade in this material. This dissolved Mn deposits at the anode surface and further contributes to degradation. Cathode–electrolyte reactions can further cause formation of a resistive solid–electrolyte interface, as a byproduct of the electrolyte breakdown. While alternative strategies such as doping, tailoring the particle morphology or core–shell structures have been suggested, a common approach to suppressing cathode degradation has been applying protective coatings on cathode particles. Stable binary oxides, such as Al2O3, MgO, ZnO, ZrO2, SiO2 and TiO2 may reduce the HF-content in the electrolyte, but their performance in suppressing the transition metal-loss from the cathode or the capacity fade can vary significantly. However, the complex nature of reactions between the cathode, coating and electrolyte prohibited the design of generic guidelines to find effective coatings beyond such simple binary oxides. Recently, we introduced a density functional theory (DFT)-based materials design approach considering the thermodynamic aspects of binary metal oxide cathode coatings, which reproduced the known effective coatings such as Al2O3, and predicted trivalent transition metal oxides as a promising class of under-explored cathode coatings. This framework was limited to only binary metal oxides, because the description of HF-reactivity and electrochemical stability of coatings were described by hypothesized reactions based on ‘chemical intuition’ (that is, reactions that had predefined forms) and could not be extended to other more complex materials. In recent years, high-throughput (HT) computational methods have significantly accelerated the search for new and better battery components. Here we introduce a comprehensive HT materials design framework to discover cathode coatings by combining the Open Quantum Materials Database (OQMD), a large collection of HT DFT calculations of ~500,000 inorganic materials, with reaction models to describe thermodynamic stability, electrochemical stability and HF-reactivity for any oxygen-bearing coating with non-intuitive, fully automated prediction of reaction products. With this framework, we design coatings with various functionalities geared towards specific battery chemistries; namely, (1) physical barriers for acid-free electrolytes, (2) HF-barriers for cathode particles fully covered with coatings and (3) HF-scavengers for particles with patchy coatings requiring active protection from HF-attack. We screen more than 130,000 oxygen-bearing materials (oxides and oxyanion compounds) available in the OQMD, and use multiobjective optimization methods, namely weighted-sum and rank aggregation, to select the best candidates for several distinct coating categories based on desired function of the coating (HF scavenger, physical barrier, or HF barrier) . We further show that coatings optimized for a particular cathode material (here, for layered- LiCoO2 and spinel-LiMn2O4) can be designed by incorporating the cathode material itself into the chemical space; that is, considering the cathode-coating reactivity and including the cathode in all chemical reactions of the framework. Screening more than 130,000 oxygen-bearing materials, we suggest physical and hydrofluoric-acid barrier coatings such as WO3, LiAl5O8 and ZrP2O7 and hydrofluoric-acid scavengers such as Sc2O3, Li2CaGeO4, LiBO2, Li3NbO4, Mg3(BO3)2 and Li2MgSiO4. Using a design strategy to find the thermodynamically optimal coatings for a cathode, we further present optimal hydrofluoric-acid scavengers such as Li2SrSiO4, Li2CaSiO4 and CaIn2O4 for the layered LiCoO2, and Li2GeO3, Li4NiTeO6 and Li2MnO3 for the spinel LiMn2O4 cathodes. These coating materials have the potential to prolong the cycle-life of Li-ion batteries and surpass the performance of common coatings based on conventional materials such as Al2O3, ZnO, MgO or ZrO2.

For Abstract see ChemInform Abstract in Full Text.

Core-shell structured Ni6MnO8@carbon nanotube hybrid as high-performance pseudocapacitive electrode material

ABSTRACTThe overall goal of this research is to explore techniques for the development of novel binary magnetic oxide nanoclusters uniformly distributed within a polymer matrix. These CoFe2O4 nanoclusters were synthesized at room temperature, and are confined within the self-assembled nanoscale structure exhibited by block copolymers templates. The diblock copolymers were synthesized by ring opening metathesis polymerization of norbornene and norbornene trimethylsilane and the binary magnetic oxide was introduced through a nanoreaction scheme using wet chemical methods. Transmission electron micrographs of microtomed thin sections of these nanocomposites show that the metal oxide nanoclusters are ellipsoidal in shape and are uniformly distributed within the polymer matrix. A SQUID magnetometer was used to study the magnetic properties of the polymeric nanocomposites at applied fields up to 5 Tesla and at a temperature range between 300 °K and 5 °K. Mössbauer spectroscopy was used to study the structure of the nanoconfined metal oxide, and confirmed the synthesis of CoFe2O4 nanoclusters exhibiting an inverse spinel structure. This study provided a better understanding of the nucleation, growth and distribution of metal oxide nanoclusters within block copolymers and indicated ways to control the magnetic properties of polymeric based nanocomposite materials. The development of such binary metal oxide - block copolymer nanocomposites is targeting the functionalization of such nanostructures into magnetic device technologies.

An efficient and green procedure for the synthesis of raloxifene has been developed by using Suzuki couplings, Friedel-Crafts acylation, and copper catalyzed coupling reactions in an ionic liquid. Keywords: Raloxifene, ionic liquids, Suzuki coupling, Friedel-Crafts acylation

Crystal chemistry and thermodynamic modelling of the Al13(Fe,TM)4 solid solutions (TM = Co, Cr, Ni, Pt)

Crystallization behavior of zirconium oxide gels

Liquid phase benzylation (by benzyl chloride) and acylation (by benzoyl chloride) of benzene and toluene over a Ga–Mg hydrotalcite (which is a basic anionic clay) with or without HCl gas pretreatment and also over the hydrotalcite used earlier in the toluene benzylation (at 110 °C) have been investigated. The fresh, used and HCl-gas-pretreated hydrotalcite catalysts were characterized for their surface area, basicity, crystalline structure and phases and also for their surface composition. The fresh hydrotalcite showed no catalytic activity for both the benzylation and benzoylation reactions for a long period. However, after a long induction period (2.7 h), the catalyst showed a very high activity in the toluene benzylation (at 110 °C). Whereas, the catalyst after its use in the toluene benzylation or after its HCl gas pretreatment showed very high activity for both the reactions with a much shorter induction period. The hydrotalcite-derived catalyst consists essentially highly dispersed gallium and magnesium chlorides on MgO. The presence of moisture in the reaction mixture has beneficial effects on the acylation reactions over the used catalyst.