Analysis And Purification Of Polyacrylonitrile-based Carbon Fiber Raw Materials

Polyacrylonitrile-based(PAN)carbon fiber accounts for 90%of total carbon fiber production.To obtain high-performance PAN carbon fiber,it is necessary to ensure the purity of each raw material.The polymerization raw materials used in the synthesis of PAN-based carbon fiber spinning stock solution are mainly polymerization solvent dimethyl sulfoxide and polymerization monomer acrylonitrile.They all contain a large amount of organic and inorganic impurities,which have a great influence on the performance of the polymerization reaction itself and the final product carbon fiber.The presence of impurities will destroy the regularity of the polymer chain,cause pore defects in the fiber,destroy the continuity of the carbon fiber crystal,and reduce the performance of the carbon fiber.Therefore,the analysis and purification of polymerization raw materials are very important for the industrial production of PAN-based carbon fibers.The first polymerized monomer of PAN carbon fiber is acrylonitrile.Methyl acrylate and itaconic acid as comonomers can effectively improve the catalytic cyclization in the production process of PAN carbon fiber.Dimethyl sulfoxide is used as the solvent to synthesize PAN copolymer.This thesis mainly studies the types of organic matter in acrylonitrile,methyl acrylate,dimethyl sulfoxide,itaconic acid,types and contents of metal elements,and the moisture content in them Purify raw materials such as methyl sulfoxide,and compare and analyze the degree of improvement of raw material purity before and after purification.Establish an analytical method for the content of p-hydroxyanisole(MEHQ)in acrylonitrile and methyl acrylate.This method uses a SH-RXI-5MS(30 m × 0.25 mm× 0.25 μm)chromatographic column,which does not require analysts to be exposed to a large amount of acrylonitrile And methyl acrylate,the safety has been greatly improved.The retention time of MEHQ is 3.22 min,which can reduce the detection limit to 0.024 mg/L.A gas chromatography-mass spectrometry method for qualitative analysis of acrylonitrile was established.A DB-5MS(60 m × 0.32 mm × 0.25 μm)chromatographic column was used.This method analyzed the organic impurities in acrylonitrile as propionitrile,methacrylonitrile,Isobutyronitrile,2-butenenitrile,3-aminopropionitrile,3-hydroxypropionitrile benzene,3,3’-oxydipropionitrile,3,3’-imine dipropionitrile,p-hydroxyanisole.Optimized the quantitative analysis method of acrylonitrile,in which the column model is DB-624(60 m×0.32 mm × 1.8μm),and the analysis and purification of organic impurities in acrylonitrile after gas purification using the normalized area calibration method in gas chromatography,the content from 0.1674%Reduced to 0.0354%.The Karl Fischer volumetric method was used to analyze the water content of acrylonitrile from 4740.4 ppm to 673.6 ppm.The sample size required for this analysis method can be as low as 0.2 mL,which is simple and fast.Inductively coupled plasma emission spectrometry(ICP-AES)was used to analyze seven trace metal elements in potassium,sodium,calcium,magnesium,iron,zinc and nickel in acrylonitrile.The gas chromatography-mass spectrometry method for the qualitative analysis of methyl acrylate using a chromatographic column of Rtx-5MS(30 m × 0.25 mm ×0.25 μm).The organic impurities in methyl acrylate obtained by this method are methyl acetate and ethyl acrylate,Toluene,methyl 3-methoxypropionate,butyl acrylate,p-hydroxyanisole,iso-zinc acrylate.The quantitative analysis method of methyl acrylate was optimized,in which the column was DB-624(60 m ×0.32 mm × 1.8×m).The area normalization method in gas chromatography was used to analyze methyl acrylate.After purification,the main component content was 99.885%Increased to 99.909%,and this method improves the resolution between the impurity peaks in methyl acrylate to 1.5.The Karl Fischer volumetric method was used to analyze the moisture content of methyl acrylate from 5166.4 ppm to 260.2 ppm.The ICP-AES method was used to analyze eight metal elements such as potassium,sodium,calcium,magnesium,aluminum,zinc,iron,and nickel in methyl acrylate.A gas chromatography-mass spectrometry method for qualitative analysis of dimethyl sulfoxide was established,using a DB-17MS(30 m × 0.25 mm × 0.25 μm)chromatographic column.The organic impurity in dimethyl sulfoxide was methylmercaptan by this method,Dimethyl sulfide,dimethyl disulfide,ethyl mercaptan,dimethyl sulfone,methyl methyl thio sulfonate,methyl(2-hydroxyethyl)sulfoxide.The quantitative analysis method of dimethyl sulfoxide was optimized.The DB-17(30 m × 0.25 mm × 0.25 p.m)column was analyzed and purified by area normalization method in gas chromatography.The content of dimethyl sulfoxide was 99.885%was increased to 99.909%,and th,e method improved the resolution between the impurity peaks in dimethyl sulfoxide to 1.5.The Karl Fischer volumetric method was used to analyze the water content in dimethyl sulfoxide from 12952.5 ppm to 448.8 ppm.The ICP-AES method was used to analyze the sodium,magnesium and calcium in dimethyl sulfoxide,Aluminum,iron,potassium,nickel and other seven elements.The content of the main component in itaconic acid after purification was analyzed by potentiometric titration from 98.31%to 98.51%.The analysis time of this method is shorter and it is more environmentally friendly.The Karl Fischer volumetric method was used to analyze the water content of itaconic acid from 1209.0 ppm to 68,5 ppm.The NH4+ content in itaconic acid was determined to be below 0.02%by Nessler’s reagent colorimetric method.The ICP-AES method was used to analyze itaconic acid for six elements including potassium,sodium,calcium,magnesium,aluminum,iron,and zinc.