Research On The Synthesis And Application Of Iron-doped Nitrogen-carbon Materials

Because of large specific surface area,ordered pore structure and good stability,porous materials are often used as catalyst or catalyst carriers.Non-noble metal nitrogen-carbon composites(M-N-C)are carbon materials doped with metal elements and nitrogen element.Compared with noble metal catalysts,M-N-C have lower cost and high catalytic activity and have a very wide range of applications in the fields of catalysis.Aromatic amines are important chemical intermediates and raw materials.They are widely used in medicine,dyes,fine chemicals,rubbers,pesticides and other important fields.They play an important role in the development of national economy.Aromatic amines are usually prepared by reducing nitro-aromatics.Hydrazine hydrate reduction method is one of the most important methods,which has attracted wide attention due to its low cost,green environmental protection and simple operation.In this thesis,firstly Fe-N-C-A porous material was prepared and then applied as catalyst to the reduction of aromatic nitro compounds.This thesis includes several research contents as follows.(1)Using F127 as template and/p-phenylenediamine,glyoxal and anhydrous ferric chloride as raw materials,a long chain Schiff base doped with ferric chloride was synthesized by one-step method.After carbonization at 877?,Fe-N-C-A porous material was prepared.Meanwhile some other Fe-N-C and N-C materials were also prepared by changing the preparation conditions.The Fe-N-C-A material was characterized by X-ray photoelectron spectroscopy,atomic absorption spectrometry X-ray diffraction,transmission electron microseopy and nitrogen adsorption-desorption.The results show that the main elements of Fe-N-C-A material are N and C and the Fe-N-C-A material has a small amount of Fe element and Fe-N-C-A material has a disordered worm-like internal structure and the specific surface area of Fe-N-C-A material is 607 m2/g and the main pore size of Fe-N-C-A material is 0.6 nm.(2)All kinds of porous materials were used to catalyze the reduction of nitrobenzene by hydrazine hydrate.The products from the reduction of nitrobenzene were qualitatively analyzed by gas chromatography-mass spectrometry(GC-MS)and gas chromatography(GC).Using 1,3,5-trimethoxybenzene as internal standard,the working curves of nitrobenzene and aniline were established by GC for the quantitative analysis of the reduction of nitrobenzene.(3)The effects of various porous materials and reaction conditions on the conversion of nitrobenzene and the yield of aniline were investigated by GC.The experimental results show that Fe-N-C-A porous material has the highest catalytic activity in all obtained porous materials.Under refluxing temperture,reducing 5 mmol nitrobenzene with 0.08 g Fe-N-C-A and 40 mmol hydrazine hydrate is the optimum reaction conditions.Under these conditions,the conversion of nitrobenzene could up to 100%and the yield of aniline could reach 99%in 40 minutes.(4)Under the optimum conditions,the recycling of Fe-N-C-A catalyst and the expansion of substrates were carried out.The experimental results show that the Fe-N-C-A material has still high catalytic activity in the second recycling.However,longer reaction time and the decreased yield were found in the third recycling.In the fourth recycling,the reaction time need to be prolonged to 360 minutes,and the yield of aniline was also reduced to 80%.The results from the expansion of substrates indicate that Fe-N-C-A material also has high catalytic reduction activity for other nitro-aromatics.The conversions of various nitro-aromatics could up to 100%and the yields of aromatic amines were above 83%in the presence of Fe-N-C-A catalyst.