Surface acid functionalization of activated carbons and its influence in the copper-support interactions.†

NAILA GÓMEZ GONZÁLEZ; FERNANDO PEREIRA; LUIS E. CADÚS; MARIA R. MORALES

Conferencia; 17. 2nd International Electronic Conference on Catalysis Sciences.; 2021

Two sets of commercial activated carbon (AC) were surface functionalized by an acid treatment using a) strong acid HNO3 (AC80 y AC90) and b) a weak acid C6H8O7 (ACC). The effect of the functionalization on the surface chemistry and structure of the AC samples was studied by means of TGA-DSC, XRD, FT-IR, N2 adsorption, TPD and tested in the de-composition of isopropanol. The catalysts were synthesized by the deposition of copper using a recirculation impregnation method. Metal dispersion, average size of metallic do-mains and metal-support interactions were correlated with the surface functionalization by using XRD, SBET, SEM-EDS, AAS, N2O. The acid treatments showed no effect on the crystal structure, however, increments in the acid/basic site concentration and the surface oxy-gen-containing functional groups (OFGs) content were observed, mainly in the AC80 and AC90 samples. BET surface measurements show a small decrease due to OFG and/or copper incorporation. Copper distribution was uniform and its content shows a direct correlation with the OFG concentration. XRD reveals the presence of Cu° and Cu2O in the Cu/AC80 and Cu/AC90 samples, possibly associated with an auto-reduction process assisted by the OFGs near the metallic centers. Cu/AC and Cu/ACC XRD patterns show no evidence of copper phases, due to low content and high dispersion. The HNO3 treated supports showed the higher dispersions and the smallest metallic domain sizes (30% - 3.3 nm Cu/AC80 and 22% - 4.5 nm Cu/AC90) while Cu/ACC showed a 17% dispersion and an average metallic domain size of 5.8 nm. The presence of surface OFGs promotes: selective adsorption of Cu, increase in the metal dispersion, decrease of domain size and the presence of alternative cop-per-derived phases, showing an increased metal-support interactions.