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Liquid-phase hydrogenation of N-nitrosodimethylamine over Pd-Ni supported on CeO2-TiO2: The role of oxygen vacancies A Physicochemical and engineering aspects

Tan, Ling, Li, Ting, Zhou, Juan, Chen, Huan, Jiang, Fang
Colloids and surfaces 2018 v.558 pp. 211-218
N-nitrosodimethylamine, adsorption, catalysts, catalytic activity, ceric oxide, colloids, hydrogenation, intermediate product, oxygen, particle size, solid solutions, titanium, titanium dioxide
Catalytic liquid-phase hydrogenation of N-nitrosodimethylamine (NDMA) over CeO2, TiO2 and CeO2-TiO2 (CexTi, x referred to the molar ratio of Ce to Ti) supported Pd-Ni bimetallic catalysts (Pd-Ni/CexTi) was investigated. Characterization results indicated that Ce-O-Ti solid solutions formed through the incorporation of Ti⁴⁺ into the CeO2 lattice, resulting in increased specific surface areas and reduced average crystal sizes of CexTi. Ti doping also promoted the generation of oxygen vacancies (Ov) on the surface of CexTi. For Pd-Ni/CexTi, the amount of oxygen vacancies first increased and then decreased with the increasing of Ti content, and the maximum content of Ov was observed on Pd-Ni/Ce4Ti. Consequently, Pd-Ni/Ce4Ti had the smallest metal particle sizes, due to the strong metal-support interaction formed between Pd-Ni and Ov. Pd-Ni/CexTi exhibited much higher catalytic activities than that of Pd/CeO2 and Pd/TiO2 for NDMA reduction, and the Pd-Ni/Ce4Ti had the highest activity. The catalytic activity of Pd-Ni/CexTi was relevant to the oxygen vacancies on the support, which influenced the metal dispersion and the adsorption of intermediate product of NDMA reduction.