The Synthetic Technology Optimization For Safranine T And The The Application In Measurement For Trace As

Safranine T is a kind of phenazine dye, which is widely used in printing, dyeing, bio-dyeing, electroplating, analytical chemistry, and other fields. The current mainstream synthesis method uses 2-methyl aniline as raw material, by the four step process of diazotization, coupling, reduction, oxidation, condensation for synthesis of safranine T, but due to some problems existing in the synthesis technology, it did not realize large-scale production in our country. In this article, we use 2-amino toluene as raw material, by improving the original process, we developed a promising technology.First of all, the existing process uses iron powder reduction of 2-aminoazo toluene to generate 2,5-diaminotoluene. In the industrial production, the iron powder are easily sedimentation, resulting in low utilization rate of raw materials, and the iron mud will pollute the environment. This article used catalytic hydrogenation reaction to take the place of iron powder reduction, solved the easily sedimentation of iron powder. We investigated the influence of solvent, reaction temperature, reaction time, hydrogen pressure, catalyst, and other factors on the yield of 2,5-diaminotoluene through experiments. Results showed that the optimum technological conditions are: solvent of 50% ethanol solution; dosage of solvent for 4 times of the quality of raw materials; hydrogen pressure of 1.1 MPa; rainie nickel catalyst of 5%; reaction temperature of 70 ℃; reaction time of 6h. Under this condition, the yield of 2,5-diaminotoluene is about 94.5%.Secondly, on the reaction of 2,5-diaminotoluene and 2-methyl aniline oxidative condensation to generate safranine T, the existing process uses dichromate salts as oxidizer, but the toxicity of wastewater containing Cr(VI) is huge and difficult to handle. This article uses TS-1/H2O2 catalytic oxidation system instead of dichromate salts, solved the pollution problems of waste water containing Cr(VI). It investigated the influence of material ratio, p H value, catalyst, reaction time, temperature and other factors on the yield of safranine T through experiments. Results showed that the optimum technological conditions are: material ratio of 2,5-diaminotoluene, 2-amino toluene, aniline and hydrogen peroxide are 1:1:1.2:9; p H value of 6; 5% dosage of TS-1 molecular sieve; temperature of 30℃, reaction time of 3h in the first stage reaction; temperature of 60℃, reaction time of 4h in the second stage reaction. Under this condition, the yield of safranine T is about 93.0%.After each step of the best reaction conditions were determined,We use 2-methyl aniline as raw material and use one kettle way on the synthesis of safranine T, intermediate product don’t need to be separated,then the final product yield is 85.7%, higher than the existing synthetic methods. The improved technology has advantages such as simple operation, high selectivity, low pollution, and it meets the requirement of green chemistry, so it is expected to be put into large-scale industrial production.On the other hand, it was found that under acidic condition, potassium iodate could oxidize safranine T and discolor the system with fluorescence quenching phenomenon, and trace amounts of As(Ⅲ) can significantly inhibit the reaction, it also has inhibitory effects on fluorescence quenching of the system. This paper established a new method to measure the trace As(III) by using the inhibition fluorescence quenching. In this paper, the experimental conditions of this system were studied in detail, under the best conditions, the linear range is 0.5 ~ 50μg /L, the detection limit is 0.24μg /L. Using this method for the measurement of trace As(III) in environmental water samples, it achieved a good result and it is of high practical value.