Study On Preparation And Performance Of Ni-based Structured Catalyst For Synthesis Of M-Phenylenediamine By Catalytic Hydrogenation

m-Phenylenediamine is an important organic intermediate for the synthesis of some polymers, dyestuff and other materials. With the increasing application of engineering materials, especially aromatic polyamide fibers and polyurethane, the demand for MPD is growing. Compared with the iron-acid reduction method, the catalytic hydrogenation of MDNB in liquid phase is an attractive process due to its advantages, such as high product yield, mild reaction conditions, less pollution to the environment, and so on.Recently, the relatively mature reactor for hydrogenation is the stainless steel autoclave equipped with a magnetically driven agitator reactor. The conversion of MDNB and the selectivity of MPD can reach 90%, but the catalytic system has some shortcomings, such as, difficulty to separate the catalyst and the reactants, intermittent operation, the low rate of total production; Another kind of trickle-bed reactor is able to maintain continuous production, but because its use is still the catalyst particles, resulting in a larger concentration of poor, low selectivity. In recent years, the cordierite structured catalysts has caused the gas-liquid-solid reaction more and more attention for the parallel vertical channels with a regular, low pressure drop, high efficiency catalyst and a better effect of heat and mass transfer characteristics and easy to replace.Raney nickel and supported noble metals(such as Pd,Pt) are usually used as hydrogenation catalysts. However, the rather rare occurrence and high price of noble metals restrict their application. As to Raney nickel, the severe corrosion and pollution resulted from its preparation process, and the safety problem during its storage and application make its use less attractive. Recently, It is well known that the supported nickel catalyst is the most important catalyst for its cost and excellent hydrogenation properties, whereas the active component nickel usually combines with support Al₂O₃ easily and forms NiAl₂O₄ of spinel structure, deactivating the catalyst. Thus, the development of new catalysts is really essential. Although some reports have ever expressed that the La₂O₃ is an ideal promoter for hydrogenation process, the modified mechanism of La for nickel catalyst is still incompletely known. In this thesis,the structured nickel catalysts have been used for the hydrogenation of m-Dinitrobenzene in order to develop a catalyst with high activity, selectivity and long service life.The catalytic hydrogenation of m-dinitrobenzene (MDNB) to m-phenylenediamine (MPD) was tested over Ni-La/γ-Al₂O₃/cordierite structured catalyst in a structured reactor. Effects of the reaction conditions, such as temperature, pressure, space velocity of hydrogen and MDNB, and catalyst dosage on the catalyst were systematically investigated. Based on the experimental results of BET, TPR, XRD, TEM, XPS and activity evaluation, the additives and catalytic performance of the catalyst were investigated. The results show that when w(Ni) =5wt%, the activity was the best. The activity and the selectivity of the samples decreased with the increase in nickel content. Adding a certain amount of additives La could improve the activity and selectivity of hydrogenation reaction, TPR characterization results the introduction of La additives improve the reduction of the catalyst performance. For Hydrogenation reaction conditions were further optimized, the reaction pressure is 3Mpa, temperature 363K, the solvent ratio of 4:1, the hydrogen flow rate of 100ml/min, liquid flow rate of 5ml/h, the catalyst activity is better. The maximum conversion rate of 83.5% and the selectivity was 90.2%.The experimental research results obtained for the future structure of the reaction of catalytic hydrogenation in the catalytic reactor for further applications in the field of useful information.