Preparation Of Solid Acid Catalyst And Its Preparation Of Aromatic Nitro Compounds From Catalytic Nitration Of Aromatic Hydrocarbons With Nitrogen Dioxide

Aromatics nitration is one of the most basic and important organic substitution reactions and it provides key organic intermediates and functional materials.It should be noted that,so far,the aromatic nitrification reaction still relies on the early developed technology to synthesize nitroaromatic compounds by using a mixture of nitric acid and sulfuric acid.However,this method has various shortcomings,such as large amount of waste acid,equipment corrosion,environment pollution,and poor product selectivity.In order to solve these problems,this work intends to use NO₂ as the nitration reagent to replace nitric acid and recyclable solid acid to replace sulfuric acid.The catalytic nitration of two aromatic hydrocarbons（benzene and1-nitronaphthalene）to prepare nitrobenzene and 1,5-dinitronaphthalene（1,5-DNN）was studied at room temperature.This article first explored a new method for preparing nitrobenzene by liquid phase catalytic nitration of benzene under low temperature and oxygen atmosphere.After testing a variety of catalysts,the experimental results show that the immobilized Lewis acid catalyst Fe Cl₃-H₂Si O₃ prepared by the chemical bonding method exhibits good catalytic performance.Under the optimized the reaction conditions,the conversion of benzene was 98.5%,and the selectivity of nitrobenzene was 99.6%.At the same time,the immobilized Lewis acid catalyst Fe Cl₃-H₂Si O₃ showed very good stability.The conversion of benzene and selectivity of nitrobenzene can maintain at relative high values of 97.2%and 99.4%,respectively,after 5 runs.The microstructure of the catalyst was characterized by XPS,NH₃-TPD and pyridine adsorption infrared.Based on the experimental and the characterization results,a possible catalytic nitration reaction mechanism of Fe Cl₃-H₂Si O₃ catalyst was proposed.At the same time,this article uses 1-nitronaphthalene as the raw material and NO₂ as the nitrating agent to catalyze nitration to obtain 1,5-dinitronaphthalene（1,5-DNN）.Firstly,the effects of various acid catalysts were investigated.The experiment showed that the solid acid WO₃-Zr O₂ catalyst prepared by hydrothermal method had better effects.The effects of the molar ratio of reactants,reaction temperature,reaction time and oxygen pressure on the nitration of 1-nitronaphthalene were also investigated.The results showed that under the optimized reaction conditions,the conversion of 1-nitronaphthalene was 90.2%,and the monoselectivity of 1,5-DNN was 49.5%.After 5 cycles,the conversion of 1-nitronaphthalene and the selectivity of 1,5-DNN can maintain stable.Using NH₃-TPD,XRD,XPS and other methods to conduct microscopic research on the catalyst.A possible reaction mechanism of the nitration process of 1-nitronaphthalene was preliminarily speculated.In order to further improve the selectivity of 1,5-DNN,several typical solid superacid catalysts were designed and prepared by the impregnation method,and the performance of the liquid phase catalytic nitration reaction was investigated.The results show that the SO₄^2-/Fe₂O₃ catalyst has a good catalytic effect,under optimized reaction conditions,the conversion of 1-nitronaphthalene was 92.3%,and the selectivity of 1,5-DNN was 51.9%.The repeated use performance was investigated,and the results showed that the conversion of 1-nitronaphthalene and the selectivity of1,5-DNN remained at a high level after repeated use for 5 times and had good stability.