Selective hydrogenation of nitroderivatives over Au/TiO2/UVM-7 composite catalyst

Hydrogenation of nitroderivatives (4-nitrostyrene or 7-nitro-1-tetralone) was performed using as support a silica mesoporous material with high specific surface area (1091 m2/g) and a bimodal pore size distribution (UVM-7). Gold and/or TiO2 were deposited inside the pores of this support with the aim to achieve high activity and selectivity for this reaction. The morphology and structure of the powders have been characterized by adsorption-desorption isotherms, XRD, TEM, STEM-HAADF, XPS and ATR-FTIR. Structural characterizations shown differences between the catalysts with and without titania. The presence of TiO2 provides a better size distribution of the spherical gold nanoparticles (in the range 3–30 nm) inside the mesopores. However, this distribution depends on the titania loading. Higher loadings of titania (20 versus 8%) induce an agglomeration of gold and generate a less selective catalyst for the hydrogenation of 4-nitrostyrene. For the same reaction, the unreduced catalyst showed an enhanced activity compared to the reduced one. The selectivity was not much influenced by the catalyst pre-reduction step. The 0.5% Au/Ti5/UVM-7 catalyst was also found to be active and selective for the hydrogenation of 7-nitro-1-tetralone to 7-amino-a-tetralone.