Non-Noble Metal Ni Nanoparticles Supported on Highly Dispersed TiO2-Modified Activated Carbon as an Efficient and Recyclable Catalyst for the Hydrogenation of Halogenated Aromatic Nitro Compounds under Mild Conditions

TiO2-modified oxygen-functionalized activated carbon (TiO2@OAC)-loaded nickel-based catalysts (Ni/TiO2@OAC) were synthesized and applied in the hydrogenation of chloronitrobenzene (CNB) to chloroanilines (CANs). The characterization results indicate that introduction of TiO2 restrains nickel nanoparticles sintering and improves the stability of the catalysts by strong metal-support interaction. Additionally, the X-ray photoelectron spectroscopy results suggest that the electron donating effect of Ti3+ produces electron-rich Ni (Ni delta-), which inhibits C-Cl moiety adsorption. The formed Ni delta- species might induce electron-rich hydrogen (H-) generation which facilitates a nucleophilic attack on -NO2 rather than an electrophilic attack on the C-Cl bond. Furthermore, the electron-donating ability of -NH2 could be reduced because of the interaction between -OH in TiO2@OAC and -NH2 in CAN. Hence, the dechlorination is inhibited and the selectivity to m-CAN is up to 99.0%. The catalytic performance of Ni/TiO2@OAC could be maintained after five cycles.