TiO<Subscript>2</Subscript> Photocatalytic Oxidation: II. Gas-Phase Processes

The results of studies on the TiO₂ photocatalytic oxidation of model air pollutants are summarized. The kinetics of photocatalytic oxidation of CO and the vapors of a number of simple organic substances was studied in detail. It was found that, in the course of reaction, all of the test substances underwent complete mineralization. Gaseous substrates were converted with the participation of several types of reaction centers. The photocatalytic oxidation of sulfur- and phosphorus-containing substances resulted in gradual deactivation of the photocatalyst; however, its activity can be restored by washing the photocatalyst with water. It was found that, along with oxidation, the steps of hydrolysis play an important role in the photocatalytic degradation of air pollutants, such as dimethyl methylphosphonate and 2-chloroethyl sulfide.__________Translated from Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 450–465.Original Russian Text Copyright © 2005 by Vorontsov, Kozlov, Smirniotis, Parmon.     

Palladium pincer complexes Pd(BH4)[{2,5-(R2PCH2)2C5H2}Fe(C5H5)] (R = Pri,But) with unidentate borohydride ligand

Russian Chemical Bulletin -     

Synthesis of mono-, di-, tri-, and tetraethyl-o-carboranes by electrophilic alkylation ofo-carborane with ethyl bromide in the presence of AICl3 and their transformations

Optimal conditions for the preparation of 9-ethyl-, 9,12-diethyl, 8,9,12-triethyl-, and 8,9,10,12-tetraethyl-o-carboranes under the action of EtBr on o-carborane in the presence of AICl₃ were determined. The behavior of these o-carborane derivatives towards electrophilic and nucleophilic reagents was studied. The presence of four ethyl groups in positions 8, 9, 10, and 12 of the carborane polyhedron increases the electron density on the boron atoms in positions 4, 5, 7, and II to the point where they are able to enter into reactions of electrophilic substitution, and in positions 3 and 6 to the point that they become resistant to the action of nucleophilic reagents. Reactions of 1,2-dilithium-8,9,10,12-tetraethyl-o-carborane with various electrophilic reagents were studied.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp 2755–2763, November, 1996.     

Strong intramolecular hydrogen bond N—H...O in 2-(2-acyl-1-phenylethenyl)-5-phenylpyrroles

The molecular structure of 2-(2-benzoyl-1-phenylethenyl)-5-phenylpyrrole and 2-(2-furoyl-1-phenylethenyl)-5-phenylpyrrole was studied by X-ray diffraction analysis at 110 K and quantum chemistry methods (B3LYP/6-31G*). In the crystalline state, both compounds have cyclic structures closed by strong intramolecular hydrogen bond N—H...O. Canonic zwitterionic structure contributes largely to the ground state of the molecules. This is probably due to synergism of the H-bonding and -electron interactions.     

Experimental study of dimethyl methylphosphonate decomposition over anatase TiO2

Removal from air and decomposition of dimethyl methylphosphonate (DMMP) over high surface area anatase TiO(2) at ambient temperature have been quantitatively studied by employing Fourier transform infrared (FTIR) technique under static conditions. In the first scenario of air purification, DMMP underwent reactive adsorption that upon completion was followed by photocatalytic oxidation. DMMP was captured over the TiO(2) surface at the speed of external diffusion. Hydrolysis of adsorbed DMMP led to methanol and methyl methylphosphonate (MMP). At low DMMP coverage quantity, it hydrolyzed completely with the formation of completely surface-bound methanol at 1% relative humidity (RH) and mostly gaseous methanol at 50% RH. Photocatalytic oxidation generated CO(2) as the only carbonaceous gaseous product and bidentate formates as the intermediate surface product. At high DMMP coverage quantity, it was captured incompletely and hydrolyzed partially with CH(3)OH in the gas phase only, 50% RH enhancing both processes. Photocatalytic oxidation generated gaseous HCOOH, CO, and CO(2) and was incomplete due to catalyst deactivation by nonvolatile products. In the second scenario of air purification, DMMP underwent adsorption, hydrolysis, and photooxidation at the same time. It resulted in the quickest removal of DMMP from the gas phase and completion of oxidation in 30 min, suggesting this process for practical air decontamination. At least 0.8 nm(2) of TiO(2) surface per each DMMP molecule should be available for complete purification of air.