Preparation Method And Application Of Environment-Friendly Asphalt

Due to its good performance,coal tar pitch is widely used in the manufacture of coatings,electrodes,etc.However,the content of carcinogenic polycyclic aromatic hydrocarbons(PAHs)in coal tar pitch far exceeds international standards,which greatly limits the development of coal tar pitch.At present,there is no mature technology in China to reduce PAHs in coal tar pitch in order to meet international standards.Therefore,the research work to reduce PAHs content in coal tar pitch is of great research significance.This paper studies three methods for reducing PAHs,including chemical modification,oxidation modification and oxidation-chemical modification.The modification effects and influencing factors of coal tar pitches with different modification methods were investigated,and the application of modified coal tar pitch in rubber was explored.The main contents are as follows:1.Influencing factors of modifying coal tar pitch by chemical modification method were discussed,the optimum process:P-toluenesulfonic acid(PTS)is the best catalyst,and p-xylylene glycol(PXG)is the best crosslinker for the modification of coal tar.The optimal reaction conditions were as follows:4%PTS,30%PXG(mass fraction of coal tar pitch),the reaction temperature was 130? and reaction time 2 hours.The PAHs content of the modified coal tar pitch was 2005ppm with a decrease of 62.08%.2.Influencing factors of modifying coal tar pitch by oxidation were discussed,the best process:dicumyl peroxide(DCP)as an oxidation modifier.The optimal reaction conditions were as follows:3%DCP(mass fraction of coal tar pitch),the reaction temperature was 175? and the reaction time was 3h.The PAHs content of the modified coal pitch was 574ppm with a decrease of 89.14%.3.The reaction mechanism of modifying coal tar pitch by chemical crosslinking and oxidation was explored through FT-IR analysis:The electrophilic substitution between PXG and PAHs was found;DCP was used as an oxidant to degrade the PAHs.According to the curve obtained from the TGA test,it could be seen that the weight loss of the coal tar pitch modified by oxidation at 400-600 ? was lower than that before the modification,indicating that no macromolecules were generated.And it could be further verified that the use of benzoyl peroxide(BPO)and DCP to modify the coal tar pitch caused the oxidative degradation of PAHs in the coal tar pitch,which reduced the PAHs content.4.In the study of modifying coal tar pitch by oxidation and chemical crosslinking,it was shown that the reactivity rules of different PAHs were the same,and the reactivity of PAHs was related to the number of its rings.As the number of PAHs rings increased,its reactivity increased and it was easier to remove.5.The content of PAHs in coal tar pitch could be further reduced by using oxidation-chemical crosslinking method for modification.The reaction conditions were as follows:First 3%DCP(mass fraction of coal tar pitch),the reaction temperature was 175? and the reaction time was 3h,then 4%PTS,30%PXG(mass fraction of coal tar pitch),reacted at 130? for 2h.The content of PAHs in the modified coal tar pitch was 386ppm with a decrease of 92.70%.6.The coal tar pitch modified with PXG could significantly improve the rubber adhesion.The coal tar pitch modified by oxidation could apparently reduce the PAHs content,but had little effect on rubber adhesion.The coal tar pitch modified with DCP-PXG could not only reduced PAHs content greatly,but also evidently improve the adhesion between rubber and steel wire,so that it could be used as a rubber adhesive.