Publication Catalysis 2011
F. Cardenas-Lizana, S. Gomez-Quero, N. Perret, M. A. Keane, Catal. Sci. Technol. 2011, 1, 652.
The catalytic gas phase hydrogenation of m-dinitrobenzene (1 atm, 423 K) over lab. synthesized (1 mol.%) Au supported on Al2O3, TiO2, Fe2O3, and CeO2 and a ref. Au/TiO2 (World Gold Council) has been investigated. The catalysts were prepd. by deposition-pptn. (DP) and impregnation (IMP), where the former route generated smaller (surface area weighted) mean Au particle sizes (1.5-2.8 nm) compared with the IMP synthesis (3.5-9.0 nm).
The catalysts have been characterized in terms of temp. programmed redn. (TPR), H2 chemisorption/temp. programmed desorption (TPD), BET area, powder x-ray diffraction, and high resoln. TEM (HRTEM) analyses. Hydrogen consumption over the T range 371-457 K during activation of Au on TiO2, Al2O3, and CeO2 can be assocd. with Au3+ Au0 redn. X-ray diffraction anal. demonstrated the presence of metallic gold in Au/Fe2O3pre-TPR. A partial and complete redn. of the hematite support to magnetite (Fe2O3 Fe3O4) was obsd. post-TPR to 423 and 673 K, resp.; H2-TPD results suggest the participation of spillover hydrogen in this step. Exclusive -NO2 group redn. and time invariant conversions were obsd. for all the catalysts considered in this study. An increase in the specific hydrogenation rate with a decrease in the mean Au size (from 9 to 3 nm) was obsd.
M-Nitroaniline was generated as the sole product over Au/TiO2 and Au/Fe2O3 whereas Au/CeO2 promoted the exclusive formation of m-phenylenediamine and a mixt. of both products was obtained over Au/Al2O3. Our findings establish a basis for the development of a sustainable (clean and continuous) process for the hydrogenation of m-dinitrobenzene where product compn. can be controlled through the choice of the oxide support.