Elsevier

Catalysis Communications

Volume 27, 5 October 2012, Pages 105-108
Catalysis Communications

Short Communication
Removal of phosgene by metalloporphyrin-functionalized porous organosilicates

https://doi.org/10.1016/j.catcom.2012.07.010Get rights and content

Abstract

This study sought to characterize the removal of phosgene by functionalized porous organosilicate sorbents. Metalloporphyrin variants were generated based on a Deuteroporphyrin IX 2,4 bis-ethylene glycol functionalized sorbent. The copper(II) variant removed phosgene at rates significantly higher than that of the bare sorbent. It was further demonstrated that the sorbent was reusable and that illumination resulted in additional target removal. The column effluent from the Cu(II) functionalized sorbent was shown to contain chloride; however, the levels were significantly less than would be expected based on a mass balance.

Graphical abstract

Highlights

► Removal of phosgene using a porphyrin functionalized sorbent is characterized. ► Illumination of the sorbent was found to increase phosgene removal. ► Chloride recovery was less than that expected for mass balance. ► Other acid products were not detected.

Introduction

In 2009, the Toxic Industrial Chemical/Toxic Industrial Material Task Force [2] released a document focusing on ocular and inhalation hazards in an operational environment. Phosgene, one of the identified compounds, is well known as a chemical warfare agent also used in industrial and pharmaceutical chemical processes. Cartridge-based air purifying respirators are utilized for protection of the warfighter against chemical exposure. Improvements in cartridge based systems including active residual life indicators and regenerable or catalytic cartridge materials are of ongoing interest. Porphyrins offer spectrophotometric and interaction characteristics that may offer some advantages to these applications. Varying the coordinated metal ion or the molecular structure of the porphyrin has been shown to significantly impact the sensitivity of spectrophotometric characteristics to the presence of ammonia, for example, as well as the reversibility of the response [3], [4], [5]. Evidence of the potential for photoreactivity between a metalloporphyrin and a light gas target has been demonstrated with nitrogen dioxide [6], [7].

The high surface area and a large interconnected pore volume of mesoporous organosilicates offer an ideal scaffold for immobilization of porphyrin moieties. They have been utilized in a wide range of catalysis and sensing applications [8], [9], [10] including in the capture and detection of gases [11], [12]. The materials utilized in the current study, combine controlled mesoporosity (2-50 nm) with macroscale texture (> 50 nm) to improve access to the mesopore volume [13], [14], [15]. We have previously reported on our efforts directed at combining the materials characteristics provided by organosilicate scaffolds with the optical and catalytic properties of porphyrins [5], [16], [17], [18]. This study details the development of sorbent materials directed toward adsorption and catalytic removal of phosgene.

Section snippets

Experimental

Synthesis of materials and porphyrin incorporation have been described in detail elsewhere [14], [19]. A description and complete characterization data are supplied in the Supplementary Material [5]. The fully functionalized sorbent utilized in these studies had a surface area of 425 m2/g, a pore volume of 0.31 cm3/g, and an average pore diameter of 62 Å.

Results and discussion

Sorbent variants were prepared using Deuteroporphyrin IX 2,4 bis-ethylene glycol (DIX) with differing metal incorporation. Based on previous studies [5], this porphyrin is known to provide interactions with some light gases. Metals were selected for evaluation as a result of their use in air purification applications [3], [21], [22], [23] or catalysis [24]. Selection of a candidate from the metal variants was accomplished based on comparison of phosgene capture from a single exposure. Air (50 

Conclusions

This study sought to characterize the removal of phosgene by a metalloporphyrin functionalized porous organosilicate sorbent. The Cu(II)DIX functionalized material was shown to remove phosgene at rates significantly higher than that expected based on interaction of the target with the surface of the sorbent. The sorbent was reusable and performance could be improved through illumination. The column effluent was shown to contain chloride, probably from the hydrochloric acid product; however, the

Acknowledgements

This research was sponsored by the U.S. Defense Threat Reduction Agency (BA08PRO015). The views expressed here are those of the authors and do not represent those of the U.S. Department of Defense or the U.S. Government.

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