CuO/TiO2-ZrO2 washcoated wire meshs for phenol wet oxidation: calcination temperature effect on copper leaching

BRUSSINO, P.; BANÚS, E.D.; ULLA, M.A.

Conferencia; 6th International Conference on Structured Catalysts and Reactors (ICOSCAR 6); 2019

Introduction. Phenolic compounds are typically found in wastewater. They are highly toxic and poorly biodegradable. Consequently, catalytic oxidation processes are often applied. Structured catalysts offer an important advantage compared to powder ones, since the catalyst separation from the reaction media is quite simple. Experimental and goals. In this work Cu(5%)/TiO2-ZrO2 wire mesh (WM) structured catalysts were prepared by washcoating of a TiO2-ZrO2 suspension and the later impregnation of CuO using Cu(NO3)2.3H2O, calcined at two temperatures: 500 °C (WM-500) and 900 °C (WM-900). For comparison, powder formulations were prepared by wet impregnation and characterized, using the same suspension dried and milled. The aims of this work are to obtain homogeneous, well-adhered films and test them in phenol wet oxidation with H2O2 as an oxidizing agent and to study the effect of the calcination temperature on the copper leaching. Results and discussion. The prepared catalytic wire meshs were active in the reaction with almost no loss of catalytic coating (up to 3 h of reaction), reaching a 100% of conversion at  7 min the WM-500 catalyst and a 98% at 3 h the WM-900 catalyst. Cu leaching was found to be 65.6 times lower for WM-900 compared to WM-500. Nevertheless, its XTOC was very low compared to WM-500. The Cu/Ti and Cu/Zr ratios obtained by SEM-EDX were very similar to those theoretical, 0.11 and 0.20 respectively. LRS and XRD showed the presence of TiO2 anatase, tetragonal ZrO2 and CuO in WM-500 (as the powder), whereas when calcined at 900 °C there was a phases change, presenting the WM-900 catalyst TiO2 rutile and monoclinic ZrO2, apart from the CuO diffractions (as the powder). Also, XPS showed Cu2+ species with high interaction with the support in both cases, but higher for WM-900. Conclusions. The increment in the calcination temperature lowered, in a very high degree, the Cu leaching. This could be related to the higher interaction of the Cu species to the support, but also, to the change in the support nature.