Research On The Content Change Of Polycyclic Aromatic Hydrocarbons During The Mixing Process Of Petroleum Pitch And Coal Tar Pitch

The rapid development of the road transport industry in China was increasingly demanding road asphalt materials,China produces more than8 million tons of coal tar pitch?CTP?every year,which has excellent adhesion and wettability to various types of gravel materials and good oil corrosion resistance when used in road construction,and the price was only 60⁷0%of petroleum pitch.However,the utilization rate was low except for a few of carbon black and electrode materials,other CTP is used for waste treatment.The main reason was that CTP contains a large number of polycyclic aromatic hydrocarbons?PAHs?,which were prioritily monitored by EPA.Petroleum pitch was used instead of traditional modifier.CTP and petroleum pitch were blended under acidic conditions to reduce PAHs in CTP.PAHs were quantitatively determined by gas chromatography.The types of petroleum pitch,blending ratio and catalysts were screened by single factor and multi-variable test method.T50-3D petroleum pitch?hereinafter referred to as T50-3D?was determined as the base asphalt,and the blending ratio of Jinyao coal tar asphalt?hereinafter referred to as JYCTP?was 25wt%.The PAHs in blended asphalt was extracted by cyclohexane.The reaction conditions were optimized as follows:the quantity of KHSO₄ or p-toluene sulfonic acid?P-TA?was 3wt%,the stirring temperature was 50 ^oC,and the reaction time was 2 h,under this condition,the reduction rates of 16 PAHs detected by coal tar pitch were73.97%and 70.49%,respectively.Secondly,the environmental effects of modified asphalt were tested,the content and release rule of 16 PAHs in fume and water soluble before and after modification were analyzed.The PAHs in fume catalyzed by KHSO₄ and P-TA decreased by 84.46%and 85.21%respectively,after heating for 1 h at 160 ^oC in air atmosphere.The PAHs decrease rate in water soluble catalyzed by KHSO₄ and P-TA was 85.97%and 95.22%,respectively.Finally,column chromatography was used to analyze the composition of petroleum asphalt.Combined with the extraction theory,the phenomenon that the amount of PAHs detected was reduced due to the change of asphalt structure was called“cage-like effect”.Under the asphalt system,any type of molecule was surrounded by surrounding molecules,as if it was locked in a cage composed of surrounding molecules.It was the inter-molecular force that forms the"cage".The strength of the inter-molecular forces affects the stability of the"cage"and affects the amount of PAHs detected.By analyzing the content and composition changes of modified asphalt,it was concluded that the cage stability of P-TA catalytic modified asphalt was greater than that of KHSO₄ catalytic modified asphalt.The modified Brown-Ladner method?B-L method?has used to calculate the average structural parameters of asphalt before and after modification.Through the changes of aromaticity,alkyl carbon ratio,average length of side chain and methyl number,the change of average structure of asphalt was inferred.It was determined that KHSO₄ had higher catalytic activity than P-TA.Petroleum pitch was used in this paper instead of traditional modifier to modify coal tar pitch,which solved the problems of poor compatibility between traditional modifier and coal tar pitch and high cost of modifier.It has positive effects on the application of low toxicity and high performance coal tar pitch for road use.