The Photooxidative Degradation of N-Methylpyrrolidinone in the Presence of Cs₃PW₁₂O₄₀ and TiO₂ Colloid Photocatalysts

Abstract

The mechanisms of the heterogeneous photocatalytic behavior of TiO2 and Cs3PW12O40 for the oxidative destruction of N-methylpyrrolidinone (NMP) in water are discussed. Both photocatalysts generate N-methylsuccinimide (NMS) and succinimide as the main intermediates from oxidation at the α-carbon and methyl positions. 2-Pyrrolidinone (2P) and 5-hydroxy-N-methylpyrrolidinone (5-HNMP) have also been identified as primary intermediates. These intermediates are all broken down under further photooxidation. However, differences in product distribution indicate the possibility of several mechanistic pathways. Hydroxyl radical-like attack predominates for TiO2-photocatalyzed degradation, whereas the polyoxotungstate appears to oxidatively destroy NMP by both OH radical attack and direct oxidation. For TiO2, the relative quantum yields for NMP oxidation (0.5 g L-1 TiO2, pH 3, 254 nm, 7 × 10-6 ein sec-1) increase from <0.01 at 10 ppm NMP to near 0.03 at 60−100 ppm. For Cs3PW12O40 under the same conditions, the apparent quantum yield is nearly invariant (0.005−0.009) over the concentration range 10−1000 ppm.

Formamide Chemistry and the Origin of Informational Polymers

“…In this latter case, formamide first condenses to uracil, probably by the mechanism reported in Scheme 4. The newly formed uracil then reacts with formaldehyde (H 2 CO), generated in situ by TiO 2 -catalyzed degradation of formamide [61], by addition to the C(5)¼C(6) bond to afford 5-hydroxymethyluracil (HMU; 10), which was detected in the reaction mixture by GC/ MS analysis [62]. Finally, thymine was obtained by the known hydride-shift mechanism involving formic acid as a product of formamide hydrolysis [63].…”

Bi2S3 nanostructures: A new photocatalyst

“…As a result, many methods for the degradation of water contaminants have been developed. Photocatalytic degradation that uses visible or ultraviolet (UV) light as irradiating source is considered as a key method of water decontamination as it can bring fast and complete mineralization of pollutants without leaving any harmful residues and has recently become a vital technology [1][2][3]. Up to now, most photocatalysts have been based on metal oxides such as TiO 2 and ZnO.…”

A visible-light-driven photocatalyst of cesium vanadate Cs 2 V 4 O 11 nanowires by hydrothermal method

“…The decrease in band gap of Cs 2 V 4 O 11 could be induced the hybridized orbitals of Cs 6s and O 2p in the conduction band. For example, the red shifts of the band gap band are observed with various contents of Cs in Cs x H 3 À x PW 12 O 40 /TiO 2 resulting enhancement of catalysts activity [11]. The photocatalytic degradation of MB by Cs 2 V 4 O 11 nanowires under visible light is shown in Fig.…”