Heterogeneous catalysis nitro compounds

An important point, difficult in many cases to be clarified, is related to the nature o-f the catalytic system, that is which is the real catalytical 1y active species and moreover in which cases we can clearly distinguish between homogeneous and heterogeneous catalysis. For these reasons, the subdivision between heterogeneous(4,2.5.1., 4.2.6.1.) and homogeneous (4.2.5.2., 4.2,5.3., 4.2.6.2.) catalysts is in some cases somewhat arbitrary and uncertain. This unsatisfactory situation is primarily due to the fact that with few exceptions the catalytic carbonylation reactions of nitro compounds proceed at high pressures and temperatures, and these are reaction conditions which interfere with studies on the mechanism of these reactions. 

Blaser HU, Siegrist U, Steiner H, Studer M (2001) Aromatic nitro compounds. In Sheldon RA, van Bekkum H (eds) Fine chemicals through heterogeneous catalysis. Wiley-VCH, Weinheim, pp 389-406... 

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