Hydrogenation of Unsaturated Carbonyl Compounds on non-Calcined LDHs. I. Synthesis and Characterization of ZnNiCuAl Hydrotalcite-like Materials.

Several Zn/Ni/Cu/Al layered double hydroxides (LDH) with variable Ni/Cu ratios but constant Zn/Al, as well as M2+/M3+ ratios, were synthesized by coprecipitation method with CO32- as compensating anion. The main goal of the study was to investigate the influence of the catalysts composition, especially Ni/Cu ratio, on the physical and catalytic properties of these materials. The XRD results show that all the LDHs samples are well crystallized and contain only pure phases. Moreover, the spectral techniques (FT-IR and DR-UV-VIS) indicated that both Ni and Cu species are present in the brucite-like layers of LDHs. The shape of the nitrogen physisorption isotherms obtained at -196 °C indicates a predominantly mesoporous materials; the surface areas and pore volumes are in the specific ranges between 37-86 m2.g-1 and 0.31-0.75 cm3.g-1, respectively. Three characteristic weight losses between 30 and 400 °C are identified by TG analysis for the hydrotalcite-like materials synthesized in this study. Moreover, an influence of the Ni/Cu ratios on the amount of the physisorbed water was noticed. The preliminary catalytic test revealed unusual catalytic properties of the non-calcined samples in the liquid phase hydrogenation of trans-cinnamaldehyde.