| 摘要 |
Selenium is dissolved in an organic solvent and nitrogen dioxide is passed thereinto whilst maintaining the temperature above 100 DEG C., to precipitate selenium dioxide, nitric oxide being formed at the same time. Specified solvents are halogenated hydrocarbons having 1-6 chlorine atoms, e.g. chlorobenzene, homologues of the latter, chlorinated diphenyls and nitrobenzene. Undissolved selenium may be present initially, and dissolve as selenium already in solution is removed by oxidation; alternatively, additional selenium may be added as the oxidation proceeds. Temperatures up to and exceeding 200 DEG C. may be used; in the example, nitrogen dioxide is passed into a flask containing selenium in trichlorobenzene at 185 DEG C. at a point just above a down-draught propeller. Nitric oxide formed in the reaction may be dried, mixed with oxygen or air, passed through silica gel to regenerate nitrogen dioxide and recycled to the process. Selenium dioxide may be separated by centrifuging or filtering the mixture and washed with selenium-free solvent followed by benzene or naphtha.
|
