Refining Process For High-Purity Acetonitrile

With the increasingly widespread use of high-purity acetonitrile, people pay more attention to the refining high-purity acetonitrile from low-cost industrial acetonitrile or waste acetonitrile recently. Many factors can affect the quality of refined acetonitrile during industrial production, while the oxidants play a vital role. A suitable oxidant can not only effectively remove the impurities, enhance the purity and yield, lower the UV absorbance, and can also easily remove the stillage residue. The current domestic acetonitrile products can not meet the demands of various uses of high-purity acetonitrile, such as HPLC grade acetonitrile and VLSI （very large scale integrated circuit） grade acetonitrile. And the stillage residue of existing refining process of acetonitrile is hard to remove.The refining processes for high purity acetonitrile from industrial acetonitrile were studied in this paper. In order to select the most efficient refined process and adsorbent, ultraviolet-visible spectrometer was used to analyze the impact of different refining processes, different adsorbents, and different activated carbon on the quality of refined acetonitrile products. Ultraviolet-visible spectrometer and gas chromatograph were used to evaluate the influence of five different oxidants on the purity and yield of refined acetonitrile products. And the removal of stillage residue impacted by oxidant was also studied. Moreover, the mechanism of the impurity adsorption of acetonitrile by different types of activated carbons, and the mechanism of the twice distillation process and reaction process of oxidants were investigated by gas chromatography, infrared absorption spectrum, ultraviolet absorption spectrum and scanning electron microcopy （SEM） .The main results are summarized as following:（1） The refined acetonitrile with minimum UV absorption can be obtained by following process: firstly, industrial acetonitrile was treated with activated carbon; then impurities were removed further by chemical reaction based on oxidants; finally the twice distillation was applied to produce high purity acetonitrile. And the results show that the adsorption property of activated carbon is superior to molecular sieve and aluminum oxide. In addition, the adsorption property of coal cylindrical activated carbon is better than coconut shell activated carbon and nutshell activated carbon.（2） High-purity acetonitriles treated with oxidants sodium peroxide series exhibit lower UV absorption than the products treated with traditional oxidants series. UV absorption of high-purity acetonitrile products treated with sodium peroxide-concentrated sulfuric acid is significantly lower than domestic commercially available chromatographically pure acetonitrile at 190～205nm wavelengths and America Fisher Scientific chromatographically pure acetonitrile at 190～200nm wavelengths. Furthermore, UV absorption of high-purity acetonitrile products treated with sodium peroxide is much lower than domestic commercially available chromatographically pure acetonitrile at 190～300nm wavelengths and America Fisher Scientific chromatographically pure acetonitrile at 190～205nm wavelengths.（3） The purity of high-purity acetonitrile treated with oxidants sodium peroxide series is higher than domestic commercially available chromatographically pure acetonitrile. High-purity acetonitrile treated with sodium peroxide has the highest purity and yield. The purity was up to 99.9993%, and the yield was 90%. The yields of acetonitrile treated with sodium peroxide-concentrated sulfuric acid and sodium peroxide-potassium permanganate were 85% and 80% respectively. The yields of acetonitrile treated with traditional oxidants of sodium hydroxide-potassium permanganate and concentrated sulfuric acid were 80% and 70% respectively.（4） The stillage residue of high-purity acetonitrile treated with traditional oxidants or sodium peroxide-potassium permanganate or sodium peroxide-concentrated sulfuric acid were difficult to dissolve in water and to remove. On the contrary, the stillage residue of high-purity acetonitrile treated with sodium peroxide was easy to dissolve in water and to remove.（5） After being adsorbed by different types of activated carbon, part of aldehydes and ketones impurities were removed from industrial acetonitrile. Coal cylindrical activated carbon can adsorb carboxylic acids and amide impurities more effectively than coconut shell activated carbon and nutshell activated carbon. Compared with coconut shell and nutshell activated carbon, coal cylindrical activated carbon has more pores, functional groups and bigger specific surface area.（6） High-purity acetonitrile treated with sodium peroxide has fewer impurities than industrial acetonitrile. Gas chromatogram of high-purity acetonitrile treated with oxidant sodium peroxide eliminates the impurities at the retention time of 5.407min, 5.873min, 6.532min, 7.540min and 13.082min, which appear in the industrial acetonitrile gas chromatogram. Moreover, the infrared absorption spectra of high-purity acetonitrile treated with oxidant sodium peroxide not only removes the impurity peaks at wave number of 2359cm^-1 and 467cm^-1, also shows no evident differences with that of chromatographically pure acetonitrile.The study of refining process for high-purity acetonitrile shows that: The quality of high-purity acetonitrile treated with oxidants sodium peroxide series are obviously superior to that of acetonitrile treated with traditional oxidants of sodium hydroxide-potassium permanganate and concentrated sulfuric acid. Especially for high-purity acetonitrile treated with sodium peroxide exhibits not only the best quality, highest yield, but also are easiest to remove stillage residue.