The Study On Optimizing The Production Of 2-naphthol And Determination Of Solubility Data

2-naphthol(MF C₁₀H₈O,CAS No.135-19-3)is a critical material of fine chemicals in the production of organic dyes and dyeing intermediates,which is widely used in the synthesis of medicine,perfume,catalyst,rubber chemicals,et al.Its down-stream products also have extensive market foreground which are applied to the synthesis of photosensitive materials like 1-hydroxy-2-naphthoic acid and liquid crystals.China and India have become the main producers now.The sulfonation-alkali fusion process,as the most mature synthesis technology,is used in the production of 2-naphthol.The process consists of sulfonation,hydrolyzation,neutralization,alkali fusion and acidification procedures.Firstly,naphthalene is sulfonated by excess amount of concentrated sulfuric acid at about438.15 K.Then,sodium sulfite is introduced to the residue of sulfonation reaction to obtain sodium 2-naphthalenesulfonate?2-SNS?.Next,solid 2-SNS,which is separated after crystallization and filtration,is used to obtain sodium 2-naphthol by alkali fusion at around 598.15 K.Finally,2-naphthol is obtained from mother liquor of alkali fusion reaction by attenuation,acidification,washing,desiccation and distillation.There are two main products in the sulfonation of naphthalene,the target product 2-naphthalenesulfonic acid?2-NSA??about 0.85 mole fraction?and by-product 1-naphthalenesulfonic acid?1-NSA??about 0.15 mole fraction?.In the current industrial process,byproduct 1-NSA is removed by hydrolysis into naphthalene and sulfuric acid at 413.15⁴18.15 K.Naphthalene is blown out by pressurized steam and reused in sulfonation reaction.Extra concentrated sulfuric acid is consumed by repeated sulfonation and hydrolysis.Meanwhile,large amount of steam is consumed,and the working environment becomes worse because of blowing naphthalene.Therefore,further improvement in the process is needed.As we all know,there are many differences in properties between position isomers such as boiling point,solubility,toxicity et al.We hope to remove the by-product by solubility difference of position isomer.However,it is hard to separate 1-NSA and 2-NSA?1-and 2-NSA?in the sulfonation mixture.For this reason,we focus on separation them after neutralization reaction,that is,separation 1-SNS and 2-SNS.The feasibility of the new strategy depends on the solubility difference of 1-and 2-SNS in aqueous sodium hydroxide solutions.However,no relative solubility data can be found in popular reference books and databases.In this work,the solubility of 1-and 2-SNS in aqueous sodium hydroxide solutions has been measured by a dynamic method over the temperature range from276 to 337 K and concentrations of aqueous sodium hydroxide solutions range from0.00 to 0.09?solute-free mass fraction of sodium hydroxide?at atmospheric pressure.The experimental data were correlated with the new electrolyte nonrandom two-liquid?E-NRTL?model which could provide reliable results for mixed solvent electrolyte systems.According to the determined solubility data,a new method for optimizing the production of 2-naphthol is proposed and discussed.