ChemInform Abstract: Switching Off Hydrogen Peroxide Hydrogenation in the Direct Synthesis Process.

Abstract

Catalysts H 2000Switching Off Hydrogen Peroxide Hydrogenation in the Direct Synthesis Process.-Whereas all catalysts so far identified for direct H 2 O 2 synthesis are equally effective for its sequential hydrogenation or decomposition to water, acid-pretreated Au-Pd/C catalysts give high yields of H2O2 with hydrogen selectivities greater than 95%. The acid treatment decreases the size of the alloy nanoparticles, and these smaller nanoparticles presumably decorate and inhibit the sites for the decomposition reaction. It is expected that the process using powdered catalysts in a small-scale batch autoclave reactor can be scaled up using continuous flow reactors to produce H2O2 at the 3 to 8% concentration levels required in most chemical and medical applications. In particular, the process lends itself to small-scale generation of H2O2, which could be of great value for the production of medical antiseptics. -(EDWARDS, J. K.; SOLSONA, B.; NTAINJUA N, E.; CARLEY, A. F.; HERZING, A. A.; KIELY, C. J.; HUTCHINGS*, G.

Pd nanoparticles supported on N-doped nanocarbon for the direct synthesis of H2O2 from H2 and O2

“…In other words, these results pointed out the potential applicability of this type of catalysts for microchanneled-type continuous reactors, although further tests are necessary. In agreement with the absence of deactivation, the analysis of the reaction solution after the catalytic tests by atomic absorption spectroscopy evidences the absence of detectable leaching of Pd, differently from recent literature results [14] showing a large metal leaching over carbon-based catalysts. After filtration and drying, the catalyst could be reused with reproducible results.…”

Revealing the role of bromide in the H2O2 direct synthesis with the catalyst wet pretreatment method (CWPM)

“…So far, in order to solve the selectivity dilemma, different approaches have been tried in order to modify the catalytic properties of the palladium based catalysts: 1) addition of halides and mineral acids in the reaction mixture 3 , 2) addition of a second metal to the palladium catalyst 6,9,10 , 3) pretreatment of the support with nitric acid [11][12][13] , 4) functionalization of different supports 14 , 5) fine-tuning of the reaction conditions [15][16][17][18][19] and 6) reactor design 16,[20][21][22][23][24][25][26] . All these aspects are important but if applied simultaneously, will not lead to a real understanding of the process since each and every of these parameters are correlated and will influence each other (positively or negatively).…”

Enhanced H2O2 production over Au-rich bimetallic Au–Pd nanoparticles on ordered mesoporous carbons

“…Additionally, the surface properties of the support can be modified to tune the final reactivity of the catalytic system. Specifically, pre-treatment of the support using nitric acid has been demonstrated to be beneficial in the direct synthesis of hydrogen peroxide [25][26][27]. In AuPd bimetallic systems, the acid treatment of carbon supports increases the hydrogen peroxide formation as it decreases the amount of active sites for nonselective hydrogenation due to an improvement in the dispersion of the Au-Pd alloy particles [25].…”

“…Using titania as a support for AuPd, the formation rate of hydrogen peroxide also increases with acid pre-treatments but in this case, the switch-off of the sequential H2O2 hydrogenation/decomposition reaction does not take place. In this case, the enhanced hydrogen peroxide formation is linked to an improvement of the dispersion of gold within the catalyst, leading to an increased proportion of smaller Au-Pd-nanoparticles, [26].…”