Catalytic H2O2 Decomposition studied by NMR Techniques. Episode II

L. BULJUBASICH

Workshop; 2nd Transylvanian NMR Workshop; 2009

Hydrogen peroxide (H2O2 ) possesses outstanding importance as  a chemical  compound.  Its  uses  cover  a  wide  range  of manufacturing  and  industrial  applications  throughout  the world. Among its most widespread uses, one may mention its participation in the elimination of organic and inorganic contaminants  in  many  environmental  applications,  where waste-water   treatment   possibly   is   the   most   common. Depending  on  the  pollutant,  H2O2 can  be  used  alone  or activated  with  catalysts  such  as  iron  (Fenton’s  reaction), ultraviolet light, ozone, etc. It is employed as a reactant in chemical synthesis and as a bleaching agent for pulp and paper, textiles and minerals, due to its oxidation capabilities.   In  a  similar  way,  it  is  also  employed  in  the  treatment  of pollutants such as iron, sulfides, organic solvents, gasolines and pesticides. Pollutants that are more difficult to oxidize may require its use in conjunction with catalysts such as iron, copper,  manganese,  or  other  transition  metal  compounds. Such a combination is used, for example, in the synthesis of conjugated polymers.   In a botanic context, H2O2 is produced naturally by leaves, where the identification of a measure of the extent to which H2O2 is allowed to accumulate is of central research interest. Since its primary decomposition products are water and oxygen, it is not a source of pollution by itself, and the use as a ‘‘green’’ propellant for space propulsion has grown in the last decade.   In this contribution, we exploit the T 2 dependence, at fixed echo  time  t E ,  in  combination  with  pH  measurements  to determine absolute H 2 O 2 concentrations. We have found a region in the T 2 -pH parameter space where the transformation (T 2 ,pH) - C is unambiguous, and allows us to obtain C with a relatively good accuracy. We  provide,  as  an  example  of  technical  applications, experimental results that were obtained applying the technique to  the  case  of  heterogeneously  catalyzed  decomposition  of H 2 O 2 based on combined NMR and pH measurements.