Research On The New Catalyst Systems For Direct Amination Of Benzene To Aniline

Single-step amination of benzene to aniline by the activation of C-H bond of benzene attracts much attention recently. Direct amination of benzene to aniline can make multi-step processes change into single-step process, which can improve atom utilization. However, how to carry out activation of C-H bond, furthermore, the introduction of-NH2into benzene, still is a challenging topic in the field of synthetic chemistry and green chemistry. Therefore looking for direct amination of benzene under mild conditions is still the researchers’study focus.In this dissertation, Three different types of non-homogeneous catalysts have been prepared and utilized as catalysts for single-step amination of benzene to aniline. The influences of these catalysts on the activity and selectivity for amination were studied. Specific contents are as follows:1. In this paper, MCM-41and a series of ordered mesoporous composite materials V-MCM-41have been prepared for single-step amination of benzene to aniline using NH2OH as aminating agent under mild conditions. The composite materials were well characterized by FT-IR, X-ray diffraction analysis, and nitrogen adsorption analysis. The results confirm that V-MCM-41with the appropriate amount of V still had highly ordered mesoporous structure. Compared with MCM-41prepared, as the amounts of V in the catalytic samples increased, the pore structure of the V-MCM-41samples changed. This may be the result that a part of V species wasn’t able to be incorporated into the molecular sieve skeleton, but was introduced onto the inner surface of the molecular sieve, they occupied more pore volume, leading to narrows in pore channel, reductions in pore size,pore volume and specific surface area.These materials were subsequently utilized as the catalysts for direct amination of benzene to aniline with NH2OH as an aminating agent under mild conditions. The influences of key reaction parameters, including loadings of V, solvents, media acidity, reaction temperature, the molar ratios of raw materials, reaction time and the catalyst amount on the activity and selectivity for the amination, were also studied. Based on the extensive literatures, the reaction mechanism was studied, thus the free-radical mechanism has been proposed for the amination of benzene, the protonated amino radical NH3+is the active aminating species for the amination of benzene.2. Using combustion method, a series of SO42-/MxOy solid super acid have been prepared for single-step amination of benzene to aniline with NH2OH as an aminating agent under mild conditions. The prepared materials doped and undoped by Nd were characterized by means of TG-DTG, XRD, FT-IR, NH3-TPD and TEM techniques. The results showed that the samples kept the typical covalence S=O bond structure of SO42-/MxOy (SM) solid acids, and both Lewis and Br(?)nsted acid sites existed; SFTN exhibited higher activity for the amination of benzene to aniline. TEM and HRTEM observation indicate that the introduction of Nd made the grains size considerably smaller, down to30nm.These materials were subsequently utilized as the catalysts for direct amination of benzene to aniline with NH2OH as an aminating agent. The influences of key reaction parameters, including catalytic preparation conditions, reaction temperatures, the molar ratios of raw materials, reaction time and the catalyst amount on the activity and selectivity for the reaction were also studied, the optimum conditions were determinded3.Gold nanoparticles (AuNPs) have been prepared by a modified colloidal deposition method, SEM and XPS analysis showed that the coverage of alumina particles by AuNPs increased as the amount of alumina decreased; AuNPs onto alumina particles by the conventional colloidal deposition method were also prepared, whose TEM showed that the coverage of AuNPs was evidently smaller than that in the case of modified colloidal deposition method, although the AuNPs were spread almost uniformly over the surface of alumina particles.Au-immobilized alumina particles (Alumina=200mg) were subsequently utilized as the catalysts for direct amination of benzene to aniline with NH3H2O as an aminating agent and H2O2as an oxidant under mild conditions. The influences of key reaction parameters, including reaction temperatures, NH3H2O amount, H2O2amount, feed motheds and reaction time on the activity and selectivity for the reaction were also studied, the reaction conditions were optimized.