Partially hydrophobized catalyst particles for aqueous nitrite hydrogenation

The aim of this work is to synthesize catalysts support particles that are partly hydrophobic and partly hydrophilic, with the ultimate goal to manipulate the performance of Pd supported catalysts on these supports for hydrogenation of nitrite in water. Partly hydrophobic alumina supports were successfully prepared via physically mixing of hydrophobic a-alumina and hydrophilic gamma-alumina, and via varying the amount of perfluorinated-octyltrichlorosilane (FOTS) on pure gamma-alumina. The results from elemental analysis, SEM-EDX, XRD and contact angle measurements confirmed that the materials indeed contained hydrophobic and hydrophilic domains. Pd catalysts on supports produced via the mixing method resulted in a slightly increased turnover frequency as compared to the original supported Pd catalyst. Remarkably, Pd supported on partially hydrophobic alumina exhibited increased selectivity to ammonia instead of N-2, which is attributed to enhanced transfer of H-2 to the active sites, via interaction of the catalyst particles with gas bubbles. (C) 2014 Elsevier B.V. All rights reserved.