Regenerating spent sulphuric acid from nitration of aromatic cpds. - esp. alkyl-aromatic cpds. by vacuum evapn. and oxidn. of organic cpds., then concn. at higher temp. using nitric acid for decolourisation

摘要

Regeneration of spent H2SO4 from nitro-aromatics prodn. by concn. of 65-80 (wt.)% H2SO4 (I) to 94-97% H2SO4 (I') with oxidative decomposition of organic cpds., opt. with HNO3, is carried out in 2 stages, comprising: 1) concn. of (I) to 85-93% H2SO4 (I'') in vacuo at 165-190 deg. C; then 2) concn. to (II) and decolorisation at 220-330 deg. C, with addn. of HNO3. Stage (I) is carried out at 175-190 deg. C, so that involatile organic cpds. are decomposed to insol. black prods. Pref. (I) is heated to 120-200 deg. C at 1.5-4 bar with (I') and then exposed to flash evaporation at 220-330 deg. C. Stage (2) is carried out in Pauling plant or vacuum evaporator. USE/ADVANTAGE - The process is used for regenerating (I) for the nitration of alkylaromatics (claimed). The process avoids the build-up of coke-like deposits, which reduce the operating time to a few days when Pauling plant is used.