Technology Research On Preparation Of Tetramethylammonium Hydroxide By Tri-chambers And Bi-membranes Electrolysis

High-purity tetramethylammonium hydroxide(TMAH)is mainly used in LCD screen and printed circuit board,the demand quantity of which is increasing year by year with the rapid development of electronic industry.Due to the disadvantages of the traditional methods of preparing TMAH such as no high purity of the product and environmental contamination,a new method of preparing TMAH was studied in this paper and an efficient and green technology was obtained.In this paper,aiming at the problems in traditional methods and through the comparative study of two typical processes,TMAH was prepared using tetramethyl-ammonium hydrocarbon(TMAC)as raw material by electrolysis with tri-chambers and bi-membranes.Firstly,scale-up experiments of synthesis of TMAC were carried out.Under the conditions obtained from the results of previous small scale experiments in our study team,scale-up pre-experiments were conducted with the characterization of the products by IR and NMR.The conversion rate of DMC reached83.6%and the hydrolysis conversion reached92.8%.On the basis,the effects of the molar ratio of raw material,the reaction temperature,the reaction time and the reaction pressure on the conversion rate of DMC were investigated.The appropriate control conditions are listed as follows,the molar ratio of raw material1:1.3,the reaction temperature130℃,the reaction time6h,the reaction pressure2.6MPa.Under these conditions the conversion rate of DMC has reached90.7%which was close to the results of small scale experiments.Then the pre-experiments of the preparation of TMAH by electrolysis with tri-chambers and bi-membranes were conducted.Based on the results of pre-experiments,Aciples-F4602was determined as cation exchange membrane.And the product was characterized by IR and NMR.The fact that the atlas obtained was consistent with standard atlas indicated the product was TMAH.Finally,optimize the process of the preparation of TMAH by electrolysis with tri-chambers and bi-membranes with the index of the current efficiency.The effects of the concentration of raw material,the electrolysis temperature and the current density on the current efficiency were studied by parameters and orthogonal test.The appropriate control conditions are as follows,Aciples-F4602cation exchange membrane.Nepem417anion exchange membrane,the concentration of TMAC2.5mol/L,the reaction time50min,the concentration of sodium sulfate0.2mol/L,the current density1600A/m2,the electrolysis temperature35-50℃.At these conditions the current efficiency was up to87.4%and the content of metal ion in the product was less than5ppb.The result that the current efficiency of parallel experiment was consistent indicated the electrolysis process would be stable.Meanwhile the effects of the concentration of raw material and the current density on cell voltage and the energy consumption were studied.The results showed that under the current density1600A/m2cell voltage and the energy consumption decreased with the increase of the concentration of TMAC,under the concentration of TMAC2.5mol/L cell voltage and the energy consumption increased with the increase of the current density.