Preparation Of Carbon Nanotubes Supported Pt-based Catalysts And Their Performance In O-Chloronitrobenzene Hydrogenation

As a novel catalyst support, carbon nanotubes(CNTs) have attracted great attention in the nanocatalytic fields due to their superb physical and chemical properties. In this thesis, the preparation of CNTs supported Pt-based catalysts and their catalytic performances have been investigated. Pt/CNTs and PtM/CNTs(M=Co, Ni) catalysts were synthesized by polyol process, and their catalytic properties were tested in o-chloronitrobenzen (o-CNB) hydrogenation reaction. The catalysts were characterized by XRD, TEM, ICP-AES and other techniques, from which the relation between catalytic properties and physical or chemical properties can be revealed.A mixture of H₂SO₄/HNO₃ acid was used for chemical modification of CNTs and SDS was used for physical modification of CNTs. It was found that both chemical and physical modifications could result in active sites that are beneficial to the nucleation and the dispersion of Pt particles, leading to improved catalytic properties of Pt/CNTs catalysts. In the case of SDS modification, micellar structure of SDS affects the nucleation and growth of Pt particles, which leads to the controllable morphology of Pt particles. The catalyst Pt/oCNTs-SDS, which is preparated from the physical and chemical modification of the CNTs, exhibit good catalytic activity, but could not inhibit dechlorination, and selectivity of o-CAN is only 77.8 %. The Pt/CNTs with different morphology and properties were synthesized by physical modification with different surfactants, including SDBS, CTAB, Tween80 and PVP, due to the electrical property and the space steric of surfactants (polymer) effect. Some of the surfactants(polymer) such as CTAB and PVP are unfavorable to the metal loading and dispersion.The catalyst Pt/oCNTs-pH was synthesized by modified polyol process, which gets high catalytic activity, but can't inhibit dechlorination. The selectivity of o-CAN is only 73.2 %. The core-shell catalysts M@Pt/oCNTs(M=Co,Ni) were synthesized by sequential modified polyol process. Besides the high catalytic activity, dechlorination could be inhibited to a certain degree, and the selectivity of o-CAN are 89.4 % and 81.4 % respectively. The alloy catalysts PtM/oCNTs(M=Co,Ni) were synthesized by simultaneous modified polyol process which still get high catalytic activity, and can inhibit dechlorination. The selectivity of o-CAN are 84.2 % and 79.2 % respectively. After the calcination of the alloy catalysts, PtM/oCNTs-600 were synthesized with expanding metal particle sizes, decreasing catalytic activities and obvious inhibitory of dechlorination comparing with PtM/oCNTs. The selectivity of o-CAN are 92.8 % and 96.5 %, respectively.