| 摘要 |
<PICT:0743080/III/1> A nitrating acid is obtained by dissolving the crystalline nitronium hydrogen pyrosulphate or nitronium hydrogen disulphate (NO2+)(HS2O7-) in at least 40 per cent nitric acid in amount insufficient to reduce the proportion of nitric acid in the mixture below 30 per cent. Sulphur trioxidecontaining gas is passed at 4 into packed absorption column 1 countercurrent to an absorption liquor having a molar ratio of SO3 : N2O5 of about 4, e.g. 3.8, and kept at over 100 DEG C. The absorption liquor is continously circulated from buffer tank 2 at 110-120 DEG C. by pump 3. Liquor is withdrawn in amount corresponding to the amount of supplied ingredients absorbed, from tank 2 at 6 to a vessel having a drum cooler 7 whereon the (NO2 +)(HS2O7-) crystallizes. The crystals may be divided into two parts and passed by conveyers 8 to reservoirs 9, 11 wherein they are dissolved in conc. nitric acid to form make-up liquor and nitrating acid respectively. The liquor in reservoir 9 is adjusted to have a composition 0-2 parts H2O, 35-50 parts SO3, and 65-50 parts HNO3, and is returned to tank 2 by pump 10. The proportions of make-up liquor and absorbed sulphur trioxide are such that the molar ratio of SO3 : N2O5 in the absorption liquor is maintained at about 4. Part of the crystals from 7 may be withdrawn as product and all the crystals may be passed to one reservoir. Specification 524,531 is referred to. |
