Sorption and Reduction of NO₂ on Microporous Ammonium 12-Tungstophosphate

Abstract

The sorption and reduction of NO2 have been studied on ammonium 12-tungstophosphate, a microporous derivative of 12-tungstophosphoric acid. NO2 penetrates into the bulk structure, where reduction by NH4 + occurs. Nitrogen, oxygen, and nitrous oxide are produced. Nitrogen is desorbed into the gas phase while oxygen apparently participates in a surface oxidation process. Since N2O is produced at higher temperatures, it appears to result from the decomposition of ammonium nitrate formed during the aforementioned processes.

Identification of Neutral and Charged NxOySurface Species by IR Spectroscopy

“…Adsorbed NO 2 is produced after NO [101,136,164,168,217,223,249], NO 2 [43,65,71,90,107,111,209], or NO ϩ O 2 [24,28,41,42,46,51,53,57,58,71,257] adsorption on SiO 2 [58], H-ZSM-5 [53], Me-ZSM- 5 [41,42,46,51,53,57,249], other exchanged zeolites [24,168,209], TS-1 [65], TiO 2 [257], Co/SiO 2 [58], Fe 2 O 3 [90], Cr/AlPO 4 [28], Ru/ZnO [217], bulk and supported V 2 O 5 [257] [71,111], and Pd/Al 2 O 3 [223]. In general, NO 2 is removed from the surface during evacuation at ambient temperature.…”

“…In addition, bands at 2263 cm Ϫ1 [111], 1920 cm Ϫ1 [217], 1728 cm Ϫ1 [71], 1570 cm Ϫ1 [64], and 1520 cm Ϫ1 [24,64] have also been proposed to be due to adsorbed NO 2 . On the contrary, a band at 1680 cm Ϫ1 has been interpreted as due to N 2 O 4 [102].…”

In Situ Infrared Study of the Absorption of Nitric Oxide by 12-Tungstophosphoric Acid

“…A large body of work has been performed in the past few decades concerning the sorption and reaction of NO x . Recently, there have been reports in the literature of the interaction of NO and NO 2 with various heteropoly acids that, under some conditions, catalyze the decomposition of the absorbed NO x …”

Synthesis and Characterization of Tungstophosphoric Acid/Pentaethylenehexamine/ZrSBA‐15 and Its Use in the Selective Oxidation of Benzyl Alcohol under Solvent‐Free Conditions

“…Pioneering studies by Misono,16,17 Mizuno,18 Kozhevnikov,19 Moffat,20,21 and others have spurred efforts towards the development of heteropolyacid‐based heterogeneous catalysts. In particular, Keggin‐type tungstophosphoric acid (H 3 PW 12 O 40 , HPW), with tunable oxidation capability, thermal stability, and environmental compatibility, has garnered the interest of academic and industrial researchers.…”

“…To address this drawback, efforts have been directed towards the generation of suitably functionalized SBA‐15 (grafting SBA‐15 with organic molecules containing the required functionality). Accessible amines on the surface of amino‐functionalized SBA‐15, for example, can facilitate the loading of HPW species and generate a supported catalyst for oxidation reactions 11,21,36–40…”