Improvement Of Toluene Conversion And Tail Gas Absorption During Nitrification

The nitration of toluene is a very important and basic organic chemical reaction.The products of nitration are o-nitrotoluene,p-nitrotoluene and m-nitrotoluene.The application of these nitro compounds in fine chemicals,such as medicine,dye intermediates,coatings,pesticides,fiber additives and so on,has been further explored and developed,which greatly increases the market demand.At present,the nitration of toluene is more traditional in industrial production,and the nitration process of mixed acid of nitrate and sulfur is mostly adopted.In this process,sulfuric acid acts as a catalyst to provide an acidic environment,and nitric acid is more likely to form a strong oxidant nitryl cation in the acid environment,which can better attack the benzene ring and take place substitution reaction,thus improving the conversion of toluene;furthermore,sulfuric acid acts as a water absorbent for the nitration of toluene: that is,with toluene.Water from nitration reactions binds to form sulfuric acid hydrates,which can prevent nitric acid from being diluted along with the reaction and improve the utilization of nitric acid.In the process of mixed acid nitration of toluene,if the sulfuric acid dosage is too small,resulting in low acidity,slow reaction rate,toluene conversion does not do;but if the sulfuric acid dosage is too large,not only will cause serious pollution to the production environment,but also will affect the amount of alkali in the back sequence,increase production and operation costs,reduce the enterprise.The competitiveness of products in this industry.In this thesis,the nitration process of toluene was studied,with emphasis on the following analysis: 1.The content of nitric acid,sulfuric acid and nitrite in the maincomponents of waste acid in the nitration process;2.The content of toluene in nitrotoluene,the product of the reaction(mass percentage).Through analyzing the components of waste acid in the process of toluene nitration,adjusting the dosage of sulfuric acid and nitric acid in raw materials,optimizing the process conditions,increasing the toluene conversion rate in the nitration process,reducing the dosage of mononitrotoluene in the liquid alkali in the post-treatment(alkali washing process),thus reducing the production and operation costs.3.The influence of reaction conditions and factors(catalyst,reaction time,reaction temperature and feed ratio etc.)on the conversion of toluene;4.The subsequent absorption of nitrous fume tail gas(nitrogen oxide gas)produced by the process of toluene nitration and the concentrated production of waste acid,and the prospect of adiabatic nitration were studied.