Thermocatalytic decomposition of dimethyl methylphosphonate on activated carbon

Activated carbon was used for the catalytic decomposition of dimethyl methy lphosphonate (DMMP), a simulant of nerve gases, at various temperatures. Un der the same conditions, activated carbon exhibited better longevity than a platinum catalyst, which has been widely chosen for this reaction. Nitroge n adsorption measurements at 77 K indicated that the majority of pores in t he activated carbon were micropores, which could be transformed to macropor es at 723 K in air. During the course of the reaction, large amounts of pho sphorus species and coke occupied the pores, resulting in a sharp decrease in pore volume and surface area. Experimental results showed that the decom position of DMMP involved two stages. In the first stage, activated carbon behaved as an initiator, converting DMMP into CO2, methanol, and P2O5. This reaction required oxygen supplied from air. In the second stage, P2O5 that had accumulated in the reactor was able to catalyze the decomposition of D MMP. The second stage was actually an autocatalytic process. A two-stage re action model of DMMP decomposition on activated carbon and other catalysts is proposed. (C) 2001 Academic Press.