Synthesis Of 1,5-dinitronaphthalene By The Catalytical Nitration Of Naphthalene Over Heteropoly Acid(salt)

1,5-dinitronaphthalene is a very important chemical intermediate which has been mainly used to prepare 1,5-diaminonaphthalene, as a intermediate for NDI, which is the raw materials of high-grade polyurethane materials that have many advantages, such as good heat-resistance, oil-resistance and wearing-resistance. Nowadays, the traditional production method for 1,5-dinitronaphthalene is a nitration process involved a mixture of nitric acid and sulfuric acid, although this method is actually improved, it suffer serious disadvantages, including low regioselectivity, undesirable byproducts, and huge amount of spent acid that are harmful to environment. In efforts to overcome these problems and speci?cally respond to market demand, researching a new and green approach to improve selective synthesis of the desired isomer has a practical significance. We use naphthalene as material preparing 1,5-dinitronaphthalene in one-step nitration, 65% nitric acid as the sole nitrating agent, report the results of catalytic reaction in the presence of heteropoly acid, zeolite catalysts and silica supported ammonium salt of molybdophosphoric acid catalysts.This paper firstly focus on the reaction conditions for nitration of naphthalene with phosphotungstic acid catalyst and nitric acid as nitrating agent in no solvent system were optimized from four aspects, molar ratio of nitric acid and naphthalene, catalyst dosage, reaction time and batch addition of nitric acid. The result shows phosphotungstic acid catalyst can promote the rate of reaction. With low molar ratio of nitric acid and naphthalene, the conversion of naphthalene is 100%, but the main product is 1-nitronaphthalene. The yield of dinitronaphthalene is increased with the increasing of molar ratio of nitric acid and naphthalene, However, the ratio of 1,5-:1,8-dinitronaphthalene is decreased. With low molar ratio of nitric acid and naphthalene, adding more catalyst and extend the reaction time, 1-nitronaphthalene is not able to convert completely. It gives the results of total dinitronaphthalene in 65.71 yield, 1,5-dinitronaphthalene in 30.78% selectivity, and with a 1,5-:1,8-dinitronaphthalene ratio of 0.88 under the conditions of 1.28 g naphthalene, 0.2g catalyst, 8h reaction time and 10 molar ratio of nitric acid and naphthalene.The zeolite supported heteropoly acid catalysts were prepared by impregnation method and were characterized. At the beginning, the catalytic performances of HZSM-5 and H-Beta with different Si/Al molar ratio were studied, the result shows that the performances of HZSM-5 is better than Hβ, and HZSM-5 with Si/Al=25 is the best. We used HZSM-5 with Si/Al=25 supported phosphotungstic acid and phosphomolybdic acid respectively. From the characterization result, we can see that heteropoly acid particles has been well dispersed on the zeolite. 5%PW/HZSM-5 has been developed to give naphthalene in 100% conversion, total dinitronaphthalene in 89% yield, 1,5-dinitronaphthalene in 38.95% selectivity, and with a 1,5-:1,8-dinitronaphthalene ratio of 0.77 under the conditions of 1.28 g naphthalene, 0.3g catalyst, 10 ml 1,2-dichloroethane, 18 h reaction time and 30 molar ratio of nitric acid and naphthalene.The supported ammonium salt of molybdophosphoric acid catalysts were prepared by sol-gel method and were characterized. The result shows catalysts exhibit a good catalytic performance and regioselectivity on nitration of naphthalene. After we optimized the catalyst preparation conditions, we found that when the loading reached 10 wt%, and the calcination temperatures was 573 K,(NH4)3PO4(Mo O3)12·4H2O particles has been well dispersed on the support and the catalyst has made the best performance. And over 10%PMo/SiO2 catalyst, 1.28 g naphthalene, 0.3g catalyst dosage, 30 molar ratio of nitric acid and naphthalene and 8h reaction time, it gives naphthalene in 100% conversion, total dinitronaphthalene in 91.81% yield, 1,5-dinitronaphthalene in 41.58% selectivity, and with a 1,5-:1,8-dinitronaphthalene ratio of 0.83. Moreover, the catalyst is reusable.