Kinetic analysis of 4-nitrophenol hydrogenatioin catalyzed by bio-inspired shaped platinum nanoparticles

Xiaodi Li, Guozhu Li,* Wanting Zang, Li Wang, Xiangwen Zhang

Corresponding author. Tel & Fax:+86-22-27892340, Email: gzli@tju.edu.cn

Aqueous-phase hydrogenation of 4-nitrophenol (4-NP) was investigated in the presence of free-standing or supported Pt nanoparticles (NPs) of various shapes. Uniform cubic and pseudo-tetrahedral Pt NPs with sub-10-nm size were obtained by the direction of bio-inspired small molecules, 3-hydroxybutyric acid (3-HB) and tropic acid (TA), respectively. The catalytic activity was found to be strongly affected by the nanoparticle shape directed by the bio-inspired capping agent and the support of SBA-15. Pseudo-tetrahedral Pt NPs directed by TA have superior activity than the cubic ones with 3-HB. But when loaded on SBA-15, cubic Pt(3-HB) NPs show better performance than Pt(TA) NPs. The experimental data are fitted to the Langmuir-Hinshelwood (L-H) model involving a surface reaction controlling mechanism for 4-NP hydrogenation. We study the kinetic process of catalytic hydrogenation for 4-NP with computational simulation by the matrix laboratory to obtain the kinetic model most suitable for our system. This model follows a dual-site adsorption with molecular adsorption of substrate and dissociative adsorption of hydrogen. Results show that pseudo-tetrahedral Pt(TA) NPs have lower apparent activation energy than the cubic Pt(3-HB) NPs for 4-NP hydrogenation. But after loading these NPs onto SBA-15, apparent activation energy of Pt(3-HB)/SBA-15 decreases while that of Pt(TA)/SBA-15 increases.