THERMAL-DECOMPOSITION OF NF3 WITH VARIOUS OXIDES

The thermal decomposition of NF3 by various oxides was investigated us ing gas chromatography, BET surface areas, and X-ray powder diffractio n. The decomposition of NF3 using alumina can occur at temperatures as low as 100 degrees C, with steady complete conversion for almost 4 h at 400 degrees C. The reaction is shown to be stoichiometric. Using Na -doped alumina, conversion of NF3 dropped off faster than conversion w ith the undoped alumina. Similarly, calcium oxide did not react with t he NF3 as completely or last as long as the alumina did; even at 400 d egrees C the conversion of NF3 was only briefly greater than 90%. HX z eolite was also reacted with NF3, with higher and more consistent conv ersion than occurred with calcium oxide and Na-doped alumina, but did not perform as well as the alumina. Over 98% conversion was maintained at 400 degrees C for more than 1 h. In all cases, nitrogen oxides and the corresponding metal fluorides were the only major products from t he reactions. The XRD patterns confirm the presence of metal fluorides for all of the materials investigated. On the basis of these investig ations, it has been concluded that of all the oxides studied, alumina is the best oxide getter for NF3.