Study On Preparation And Application Of The Structured Catalyst By The Vacuum Extraction Impregnation Method

Because of the structured catalyst owe an monolithic structure and have many parallelstraight channel，the structured reactor can easily separate the catalyst from the products、low content of target product. However, itself has incomparable advantages to otherreactors, such as amplification effect is small. As a result, it is practically significant todevelop the catalytic hydrogenation m-dinitrobenzene to m-phenylenediamine in structuredreactor. Due to the coated structured catalyst specific surface area of²0m2/g, the dispersityof active component is lower, reducing the catalytic activity, how to improve thedispersion is an important problem of current concern. In this thesis, the structured catalystof Ni/γ-Al₂O₃/cordierite was prepared by excessive impregnation and vacuum suctionmethods. And then applied in m-dinitrobenzene（MDNB） catalytic hydrogenation tom-phenylenediamine（MPDA） in structured reactor to evaluate the catalyst performance.The structured catalyst have been prepared excessive impregnation and vacuumsuction methods, Effects of the preparation conditions，such as suction vacuum degreeand time, impregnating solution concentration and time as well as the calcinationtemperature on the catalyst dispersion were systematically investigated. The configuration andcatalytic performance were characterized by BET, H₂-TPD and activity evaluation. Theresults show that degree of vacuum and vacuumizing time increase, catalyst dispersityincreased; As the concentration of impregnation solution and dipping time increased, thedispersion was first increased and then decreased; Improve the calcination temperatureexhibited a similar law. This method can regulate the degree of dispersion of the catalyst,when the concentration of the impregnating solution was0.5M, and the immersion time is1h, the degree of vacuum of0.095Mpa, vacuum time of1min calcination temperature of673K catalyst dispersity increased to38.4. In addition, an appropriate dispersity canremarkably promoted the reaction, under the experimental conditions the proper dispersitywas26.4%, the conversion of MDNB is88.0%, the selectivity of MPDA is87.8%. Thereason why there are a suitable dispersion are discussed and analyzed.This article also examines the influence of additives of La on catalyst performance, set a certain amount of La can effectively restore the phase of NiAl2O4, Moreover weakenthe interaction between active component and carrier, improves the reduction properties ofthe catalyst, thus effectively improve the performance of hydrogenation. Meet the catalystin the case of having a certain surface area, with more channels, more conducive to thedispersion of the active ingredient Ni, improve the reduction performance of the catalyst.When the additives content of La is5%in mass fraction, the highest conversion rate can reachof91.6%and the selectivity is90.9%.