The Synthesis And Catalytic Activities Of Supported Nickel And Nickel-palladium Nanocatalysts

The preparation of aromatic amine substance compounds becomes more and more important in many domains such as chemicals,fuel and medicine.Catalytic synthesis of the aromatic amine materials over catalysts is one of the most common methods.Meanwhile,this catalytic reduction method is the focus of recent research because of its advantages such as easy operation and low environmental pollution. Among these, the preparation of4-aminphenol(4-AP) reducted from 4-nitrophenol(4-NP) is an representative reaction.So in this thesis,we synthesized two supported metal catalysts and studied them in the reduction of4-NP to 4-AP. Main researches are included as follows:(1) Ni Pd/N-r GO nanohybrids were synthesized via a facile co-reduction method using N doped reduced oxidized graphene as supports. The resultant Ni Pd/N-r GO nanohybrids were characterized using TEM, XRD, EDX, ICP-EOS, XPS and VSM, respectively. We studied catalytic performance of Ni Pd/N-r GO nanohybrids in the catalytic reduction of 4-nitrophenol experiment. The results show that many tiny Ni-Pd NDs with a diameter of ~5 nm deposit on the Nr GO nanosheets. Such nanohybrids exhibit a promising catalytic activity towards the reduction of 4-nitrophenol by sodium borohydride and show a high rate constants of 3.4mg-1s-1 when Ni-Pd nanodimers has a 40.6 wt% loading. The activation energy is estimated to be 29.1 k J·mol-1based on the Arrhenius equation, and the result show that the catalyst was not sensitive to changes in temperature. Taking the reaction rate and economic cost into consideration, and fixed its optimum value at 2 μg·m L-1. The reusability of the Ni Pd/Nr GO was also investigated with ten consecutive cycles. It shows the resultant catalyst can be recycled ten times without significant loss of the catalytic activity. The Ni Pd/Nr GO catalyst can be readily recovered by a magnet, and it provides a novel way for graphene based nanocatalysts of recycling use in industrial production.(2) A-Ni B/C nanohybrids were synthesized via a solution-phase synthesis using nanosized carbon spheres as supports. The resultant A-Ni B/C nanohybrids were characterized using TEM,XRD, EDX, ICP-EOS and XPS, respectively. We studied catalytic performance of A-Ni B/C nanohybrids in the catalytic reduction of 4-nitrophenol experiment. The results show Ni was amorphous among Ni B/C nanohybrids. Such nanohybrids exhibit a promising catalytic activity towards the reduction of 4-nitrophenol by sodium borohydride and show a high rate constants of 3.464 mg-1s-1 when Ni has a 23.5 wt% loading. Compared to the common noble metals and the literature of the same type catalyst, such A-Ni B/C nanohybrids have excellent catalytic performance. The activation energy is estimated to be 34.2 k J·mol-1 based on the Arrhenius equation, and the result show that the catalyst was not sensitive to changes in temperature. A-Ni B/C catalysts can be reused more than 5 times, and its catalytic activity has no obvious change. The result confirmed that the catalyst has the repeated use of the stability of the catalytic activity. It is a new choice for reduction of 4-NP in industrial production, due to its simple synthesis, low cost, high catalytic activity and cycle stability.