Revisiting the Mukaiyama-type epoxidation for the conversion of styrene into styrene carbonate in the presence of O2 and CO2

Alkene epoxidation using the Mukaiyama process involving O2 and a sacrificial aldehyde, as the first step of the global alkene oxidative carboxylation, does not necessarily require a metal catalyst.

Al2O3-Supported W–V–O bronze catalysts for oxidative dehydrogenation of ethane

Vanadium-containing hexagonal tungsten bronze (HTB) structures supported on Al₂O₃ are more selective to ethylene during ethane ODH than supported vanadium oxides.

Functional Enzyme Mimics for Oxidative Halogenation Reactions that Combat Biofilm Formation

Transition-metal oxide nanoparticles and molecular coordination compounds are highlighted as functional mimics of halogenating enzymes. These enzymes are involved in halometabolite biosynthesis. Their activity is based upon the formation of hypohalous acids from halides and hydrogen peroxide or oxygen, which form bioactive secondary metabolites of microbial origin with strong antibacterial and antifungal activities in follow-up reactions. Therefore, enzyme mimics and halogenating enzymes may be valuable tools to combat biofilm formation. Here, halogenating enzyme models are briefly described, enzyme mimics are classified according to their catalytic functions, and current knowledge about the settlement chemistry and adhesion of fouling organisms is summarized. Enzyme mimics with the highest potential are showcased. They may find application in antifouling coatings, indoor and outdoor paints, polymer membranes for water desalination, or in aquacultures, but also on surfaces for food packaging, door handles, hand rails, push buttons, keyboards, and other elements made of plastic where biofilms are present. The use of natural compounds, formed in situ with nontoxic and abundant metal oxide enzyme mimics, represents a novel and efficient "green" strategy to emulate and utilize a natural defense system for preventing bacterial colonization and biofilm growth.

Synthesis of Vanadium Oxide Nanofibers with Variable Crystallinity and V5+/V4+ Ratios

Tailoring the morphological, chemical, and physical properties of vanadium oxides (VOx) is crucial to optimize their performance in current and future applications. The present contribution proposes a new route to obtain VOx nanofibers with different V⁴⁺/V⁵⁺ ratios and crystallinity. The method involves the exclusive electrospinning of water-free NH₄VO₃-saturated solutions including a reductant. Subsequent air-annealing under suitable conditions yields vanadium oxide fibers of 20-90 nm diameter and 10-50 m²/g surface area. The presence of the reductant gives rise to VOx nanofibers with a considerable proportion of V⁴⁺. Then, the right choice of the calcination heating rate and temperature permits to modify the V⁴⁺/V⁵⁺ ratio as well as the crystalline phase and crystallite size of the fibers. With the proposed methodology, long-range continuous single-phase orthorhombic V₂O₅ and monoclinic V₃O₇ nanofibers are obtained.

Oxidative dehydrogenation of n-butane to butenes on Mo-doped VMgO catalysts

A small amount of Mo-doping in a VMgO catalyst significantly results in an increase in the total butene selectivity.

Ru/TiO2-catalysed hydrogenation of xylose: the role of the crystal structure of the support

Lattice matching holds the secret to the Ru-catalysed hydrogenation of xylose to xylitol, a key reaction in practical biomass conversion.

Semimetal-functionalised polyoxovanadates

Polyoxovanadates (POVs), known for their wide applicability and relevance in chemical, physical and biological sciences, are a subclass of polyoxometalates and usually self-assemble in aqueous-phase, pH-controlled condensation reactions. Archetypical POVs such as the robust [VO42](12-) polyoxoanion can be structurally, electronically and magnetically altered by heavier group 14 and 15 elements to afford Si-, Ge-, As- or Sb-decorated POV structures (heteroPOVs). These main-group semimetals introduce specific chemically engineered functionalities which cause the generally hydrophilic heteroPOV compounds to exhibit interesting reactivity towards organic molecules, late transition metal and lanthanoid ions. The fully-oxidised (V(V)), mixed-valent (V(V)/V(IV) and V(IV)/V(III)), "fully-reduced" (V(IV)) and "highly-reduced" (V(III)) heteroPOVs possess a number of intriguing properties, ranging from catalytic to molecular magnet characteristics. Herein, we review key developments in the synthetic and structural chemistry as well as the reactivity of POVs functionalised with Si-, Ge-, As- or Sb-based heterogroups.

The epoxidation of limonene over the TS-1 and Ti-SBA-15 catalysts

Limonene belongs to a group of very important intermediates used in the production of fine chemicals. This monoterpene compound can be obtained from peels of oranges or lemon which are a (biomass) waste from the orange juice industry. Thus, limonene is a renewable, easy available and a relatively cheap compound. This work presents preliminary studies on the process of limonene epoxidation over zeolite type catalysts such as: TS-1 and Ti-SBA-15. In these studies methanol was used as a solvent and as an oxidizing agent a 60 wt % hydrogen peroxide solution was applied. The activity of each catalyst was investigated for four chosen temperatures (0 °C, 40 °C, 80 °C and 120 °C). The reaction time was changed from 0.5 to 24 h. For each catalyst the most beneficial conditions (the appropriate temperature and the reaction time) have been established. The obtained results were compared and the most active catalyst was chosen. These studies have also shown different possible ways of limonene transformation, not only in the direction of 1,2-epoxylimonene and its corresponding diol, but also in direction of carveol, carvone and perillyl alcohol-compounds with a lot of applications. The possible mechanisms of formation of the allylic oxidation products were proposed.