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Chapter 2
2.5.9 Oxidation with inorganic agents
[6, Ullmann, 2001, 16, Winnacker and Kuechler, 1982, 43, Chimia, 2000, 44, Hörsch, 2003]
Chemical oxidation with inorganic agents is still industrially important, due to the fact that
reactions with molecular oxygen are usually considerably less selective and generally require
much higher investment, thereby only becoming economically worthwhile for capacities above
about 10000 tonnes per year, depending on the product.
Overview
Table 2.13 gives an overview of the main aspects important in the selection of a suitable
oxidation agent, the related by-products and some other characteristics. In the case of CrO3 and
MnO2, the agent by-products are often regenerated [99, D2 comments, 2005].
Agent Target molecules Agent by-product
CrO3
“Chromic acid”
Benzoic acids, benzaldehydes Cr2O3
KMnO4 Benzoic acids, benzaldehydes MnO2
Typical solvents/
other aspects
Acetic acid, acetic
anhydrides
MnO2 Benzaldehydes Mn 2+ Aqueous H2SO4
HNO3 Benzoic acids NOX
In situ regeneration of NO
to HNO3 with oxygen
NaOCl Stilbenes NaCl
Cl2
Sulphones, sulphochlorides,
chloranil
HCl
Table 2.13: Overview of oxidations with inorganic agents
Environmental issues
Table 2.14 gives some example data for the waste streams from oxidations. The main
environmental issues are:
• exhaust gases, possibly containing VOCs, NOX or HCl
• solid agent by-product, containing heavy metals
• mother liquors, possibly containing high loads of organic by-products and heavy metals,
and high AOX loads when Cl2 or NaOCl are used.
Waste stream Properties
Oxidation of 3-picoline with chromic acid [43, Chimia, 2000]
Inorganic solid residues 1.7 to 2.0 tonnes Cr2O3 per tonne product
Oxidation of 3-picoline with KMnO4 [43, Chimia, 2000]
Inorganic solid residues 4.0 tonnes MnO2 per tonne product
Manufacture of 4,4’dinitrostilbene – 2,2’disulphonic acid [44, Hörsch, 2003]
Mother liquors
COD: 28400 mg/l
AOX: 230 mg/l
BOD28/COD: 0.04
Table 2.14: Example data for the waste streams from oxidations
54 Dezember 2005 OFC_BREF