Nanocrystallites-forming hierarchical porous Ni/Al_2O_3-TiO_2 catalyst for dehydrogenation of organic chemical hydrides

摘要

Dehydrogenation of organic chemical hydrides has been improved by reconstructing the catalyst in the form of hierarchical porous structure nanocatalyst, in which the economical Ni was adopted as catalytic component and nano Al_2O_3-TiO_2 hybrid composite as support. The Al_2O_3-TiO_2 composite was prepared by spontaneous self-assembly of nano A12O3 and TiO_2 aggregates by hydrolysis of tetra-n-butyl-titanate under continuous agitation. The multi-scaled distribution of Al_2O_3—TiO_2 aggregates with hierarchy could be observed in dynamic light scattering spectrometer. The aggregates are comprised of nano-sized y-Al_2O_3 and anatase TiO_2 crystallites with sizes of about S and 7 nm, respectively. The surface modulation by TiO_2 could be verified in FTIR Spectra. The migration of Ti species and crystallite growth were hindered by the Al_2O_3 skeleton and the hierarchical porous structure was sustained during the thermal related process. The multi-scaled distributed pores were confirmed by both TEM analysis and N_2 adsorption results. The results of dehydrogenation experiments showed that the hierarchical porous structure nano Ni/ Al_2O_3-TiO_2 exhibited superior catalytic performance to Ni/Al_2O_3 with the optimum conversion of 99.9% at 400℃, while the catalyst of Ni/Al_2O_3 exhibited only 16.5% under the same condition.