Studies On The Liquid Nitration Of Naphthalene To 1,5-dinitronaphthalene

1,5-dinitro-naphthalene,the nitrates of naphthalene has been mainly used to prepare NDI and 1,5-diamino-naphthalene.1,5-diamino-naphthalene was an extremely important intermediates in fine chemical industry,and NDI is the raw materials of high-grade polyurethane materials because of its high melting point,high elastic,and many other advantages,the market demand is very huge.However,the direct nitration of naphthalene produces 1,5-dinitro-naphthalene and 1,8-dinitro-naphthalene in a ratio of about 1:2,the unfavorable selectivity of the reactions means that a high and undesirable proportion of 1,8-dinitro-naphthalene is preferential formed in the production of 1,5-dinitro-naphthalene.In addition,it cause to serious environmental problem.Thus,the cost of the production of NDI is so expensive that the practical application in the industry and daily life is very limited.In order to improve the selectivity of 1,5-dinitro-naphthalene,this article will focus on the nitration of naphthalene to explore a route of less environment pollution and higher the selectivity of the purpose product.It will have important theoretical and practical significance for the preparation of high-grade polyurethane materials.In this paper,the nitration of naphthalene were studied,in order to meet the need of the research of the nitration product from liquid nitration of naphthalene,a quantitative analysis for naphthalene and nitration products was established.The PW with keggin structure was supported on HY and HZSM-5 by wetness impregnation method.Their physicochemical properties such as the dispersion of PW,surface area,pore structure and acidity were characterized by X-ray diffraction(XRD),N2 adsorption isotherm,infrared-ray spectrum(IR),and ultra visible spectroscopic(ORS).Based on the characterizations,the catalytic behavior was tested in the nitration of naphthalene,and the correlation of the surface properties of the catalysts and their activity and selectivity has been discussed in detail.It was found that the pore structure and acidity of catalysts are the key factors that influence the catalytic performances.XRD results indicate that PW/HY with various PW loading content retain the high specific surface area and micropore structure of HY with abundant secondary pore system.When the PW loading content is 30%,PW could highly disperse on the surface of HY because of the interaction of molecular PW and secondary pore walls of HY.In the nitration of naphthalene catalyzed by 30%PW/HY,under the reaction conditions of 338 K and naphthalene/nitric acid molar ratio of 40 gave 96%selectivity of 1,5-dinitro-naphthalene and 1,8-dinitro-naphthalene,of which the selectivity to 1,5-dinitro-naphthalene is 38.5%.XRD results show that when the loading content of PW reaches to 30%,PW has been formed microcrystalline in the surface of HZSM-5.However,PW/HZSM-5 retain the high specific surface area and micropore structure of HZSM-5 with lower loading content of PW,PW could highly disperse on the surface of HZSM-5 because of the interaction of molecular PW and pore walls of HZSM-5.FT-IR spectra observed that the acidity of PW/HZSM-5 was improved with the increase of PW loadings.under the reaction conditions of 338 K and naphthalene/nitric acid molar ratio of 30,the most active catalyst,5%PW/HZSM-5 calcined at 773 K gave 97%total selectivity of 1,5-dinitro-naphthalene and 1,8-dinitro-naphthalene,of which the selectivity to 1,5-dinitro-naphthalene is 48.5%.Finally,the catalyst SO42-/ZrO2 was prepared by precipitation method and characterized by IR.X-ray diffraction(XRD)and N2 adsorption isotherm.The catalytic performance of the solid super acid calcinated at different temperature were studied.The result shows that the catalyst calcinated at 550? gives better result.Then,the catalysts calcinated at 550 ? were used in the nitration of naphthalene.Under the reaction conditions of 338 K and naphthalene/nitric acid molar ratio of 30,the most active catalyst,SO42-/ZrO2 calcined at 823 K gave 97%total selectivity to 1,5-dinitro-naphthalene and 1,8-dinitro-naphthalene with 35.1%selectivity to 1,5-dinitro-naphthalene.The different loading content of PW/ZrO2 were prepared and the 10%PW/ZrO2 exhibits excellent activity and selectivity for 1,5-dinitro-naphthalene.In the nitration of naphthalene catalyzed by 10%PW/ZrO2,under the reaction conditions of 338 K and naphthalene/nitric acid molar ratio of 30,it gave 97%total selectivity to 1,5-dinitro-naphthalene and 1,8-dinitro-naphthalene with 46.2%selectivity of 1,5-dinitro-naphthalene.