Photoassisted Decomposition of Dimethyl Methylphosphonate over Amorphous Manganese Oxide Catalysts

Abstract

The gas-phase decomposition of dimethyl methylphosphonate (DMMP) has been studied over amorphous manganese oxide (AMO) catalysts in the presence of light (∼200-800 nm). The reaction was studied under oxidizing conditions using air at low temperatures (40-70 °C). DMMP and gas-phase products were studied using gas chromatography (GC). DMMP was found to adsorb strongly to the AMO surface and produce small amounts of methanol (MeOH) even in the absence of light. When AMO was irradiated with light of ∼200-800 nm, large amounts of MeOH and CO 2 were initially formed. Following the initial period of high activity, strong deactivation was observed. After the reactions were performed, aqueous extracts from spent AMO were analyzed using ion chromatography (IC). The IC analyses indicated that several products accumulate on the AMO surface. These products include methyl methylphosphonate (MMP) and methylphosphonic acid (MPA). Greater amounts of MMP and MPA are produced after irradiation. Fourier transform infrared (FTIR) spectroscopy was used to examine adsorbed DMMP species on spent AMO. The IR results indicate that DMMP bonds to Mn Lewis acid sites on the AMO surface via the phosphoryl oxygen. On the basis of these results a mechanism is proposed for the adsorption and photoassisted decomposition of DMMP over AMO.

Fourier Transform Microwave Spectrum and ab Initio Study of Dimethyl Methylphosphonate

“…There is significant interest in the catalytic activity and decomposition mechanisms of DMMP on a number of different catalytic surfaces (12)(13)(14)(15). Now that the conformational geometry of DMMP and the relative magnitudes of the dipole moment components are known, this information could be useful in aiding the understanding of the catalytic interactions and decomposition mechanisms of DMMP on these surfaces.…”

Synthesis of V2O5 Nanoflakes on PET Fiber as Visible-Light-Driven Photocatalysts for Degradation of RhB Dye

“…Furthermore, narrow band gap semiconductor such as manganese oxide (MnO 2 ) nanoparticles [16,17] and vanadium dioxide (VO 2 ) nanoparticles [18] could also be used as visible-light-driven photocatalysts. Normally, H 2 O 2 chemical was required to improve the photodegradation efficiency of these semiconductor photocatalysts in degradation of organic compounds under visible light irradiation [19].…”

Removal of high concentration dimethyl methylphosphonate in the gas phase by repeated-batch reactions using TiO2

“…Several studies have been conducted in order to investigate the effects of temperature conditions on adsorption and decomposition of DMMP on TiO 2 surface [11][12][13][14][15][16]. Rusu and Yates [15] reported that at the temperature lower than −113 • C, DMMP condenses as an ice layer on the outer surface of TiO 2 .…”

“…Most studies on the photocatalytic decomposition have been carried out at room temperature [3][4][5][6][7]. Segal and Suib [14] reported that the advantages of photocatalysis are that benign products such as CO 2 and H 2 O can be produced, high temperatures can be avoided, and that it may be possible to utilize solar energy for reactions. Furthermore, photoassisted decomposition and thermal decomposition of DMMP over amorphous manganese oxide catalysts were carried out at low temperature (70 • C).…”