Thermal Hazard and Kinetics of Naphthalene Nitration

• Main Authors: Ming-Chang Hung, 洪明璋
• Other Authors: James-I Chang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/79248163649458397758

碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程所 === 92 === Traditional aromatic nitration carried out in a large volume of concentrated nitric and sulfuric acids is highly dangerous and produces a large amount of waste acids difficult to recover. In the past, numerous efforts have been made to search for a safer and alternative process for the replacement of the traditional process. Fierz-David process that uses a stoichemetric concentration of nitric acid and acetic anhydride to react with naphthalene in the solution of acetic acid has several advantages over the traditional method. The conversion is high and it produces less waste acid. The by-product is acetic acid, which can be recovered and reused easily. However, an unstable intermediate of acetyl nitrate that decomposes at a temperature of 50 ℃ or higher has to be formed as the nitrating agent. That a large amount of unstable acetyl nitrate in the reactor is definitely a safety hazard. To minimize the formation of acetyl nitrate and to improve the process safety, alternative order of reagent feeding should be tested. The purpose of this research are to study the thermal hazard of the Fierz-David process, to study the feasibility of an alternative semi-batch process that titrates nitric acid into the solution of the other reagents in a reaction calorimeter, and finally to study the feasibility of adding a zeolite catalyst to improve the reaction rate. The results from TGA and DSA studies showed that all chemicals except acetyl nitrate were very stable when the temperature was under 150 ℃.Acetyl nitrate that was formed by the reaction of nitric acid and acetic anhydride would be decompose when the temperature was over 55 ℃. The yields of 1-nitronaphthalene and 2-nitronaphthalene of the new semi-batch process with an alternative order of reagent feeding tested in this research were similar to those of the original process. The overall reaction order was 2, and the orders of nitric acid, naphthalene, and acetic anhydride were 0.9, 0.55, and 0.55, respectively. The reaction rate dropped when a zeolite catalyst (5%) was added to the reaction, but the yield of the high priced 2-nitronaphthalene increased. However, the reaction rate and the overall naphthalene conversion increased, when acetic acid was replaced with 5% zeolite catalyst. To improve the reaction rate, the selectivity of the high priced 2-nitronaphthalene, and process safety, we suggest the following: acetic anhydride is first mixed with 5% zeolite catalyst in the reactor, and nitric acid and naphthalene are fed into the reactor simultaneously in a semi-batch mode. This new and alternative process may have a potential for the replacement of both Fierz-David and the traditional processes.