NH3_{3}-SCR over V-W/TiO2_{2} Investigated by Operando X-ray Absorption and Emission Spectroscopy

V–W/TiO$_{2}$-based catalysts, which are used for the removal of NO$_{x}$ from the exhaust of diesel engines and stationary sources via selective catalytic reduction with NH$_{3}$ (NH$_{3}$-SCR), were studied by operando X-ray absorption spectroscopy (XAS) and emerging photon-in/photon-out techniques. In order to minimize the influence of highly X-ray absorbing tungsten and the fluorescence of titanium, we used a high-energy-resolution fluorescence setup that is able to separate efficiently the V Kβ$_{1,3}$ emission lines and additionally allows to record valence-to-core (vtc) X-ray emission lines. High-energy resolution fluorescence-detected XAS (HERFD-XAS) and vtc X-ray emission spectroscopy (vtc-XES) proved to be the only way to perform an operando V K edge X-ray spectroscopic study on industrially relevant V–W/TiO$_{2}$ catalysts so far. The V–W/TiO$_{2}$ and V/TiO$_{2}$ samples synthesized by incipient wetness impregnation and grafting exhibited high activity toward NH$_{3}$-SCR. Raman spectroscopy showed that they mainly contained highly dispersed, isolated, and polymeric V-oxo species. HERFD-XAS and XES identified redox cycling of vanadium species between V$^{4+}$ and V$^{5+}$. With respect to most of the potential NH$_{3}$ adsorption complexes, density functional theory calculations further showed that vtc-XES is more limited than surface-sensitive techniques such as infrared spectroscopy; hence, a combination of X-ray techniques with IR or similar spectroscopies is required to unequivocally identify the mechanism of NH$_{3}$-SCR over vanadia-based catalysts

Some New Reactions and Properties of Xanthane Hydride (5-Amino-1,2,4-dithiazole-3-thione)

Aminomethylation of xanthane hydride (5-amino-1,2,4-dithiazole-3-thione) with the RNH2–HCHO system has resulted in the formation of the derivatives of new heterocyclic system (3,7-dihydro-5H-[1,2,4]-dithiazolo[4,3-a][1,3,5]triazine) in low yields. The reaction of xanthane hydride with dicyandiamide has led to thioammeline [4,6-diamino-1,3,5-triazine-2(5Н)-thione]. Some practically important properties of xanthane hydride and its derivatives have been investigated. Xanthane hydride has efficiently exhibited carbon steel corrosion in neutral aqueous media. The prepared compounds have not exhibited growth-regulating or antidote activity to herbicide 2,4-D

A water-soluble, bay-functionalized perylenediimide derivative-correlating aggregation and excited state dynamics

The aggregation and the photophysics of a water soluble perylenediimide (PDI) derivative that features two bromine substituents in the bay positions has been probed. Non-fluorescent aggregates were found to be present at concentrations of 1.0 7 10-5 M. In situ small-angle X-ray scattering (SAXS) measurements and complementary molecular modeling showed the presence of PDI aggregates. In their singlet excited states, the PDI aggregates are characterized by distinct transient fingerprints and rapid deactivation, as revealed by pump-probe experiments on the femto-, pico-, nano-, and microsecond timescales. The product of this deactivation is a PDI triplet excited state. The efficiency of the triplet formation depends on the concentration, and hence on the degree of aggregation. Notably, for PDI concentrations in the range of the critical micelle concentration, the efficiency of intersystem crossing is close to zero. In short, we have demonstrated, for the first time, aggregation-induced formation of triplet excited states for PDI derivatives