Method for preparing low-toxicity modified coal pitch for road building

Abstract

A method for preparing low-toxicity modified coal pitch for road building includes the steps that coal-tar pitch, terephthalaldehyde modifiers, p-toluenesulfonic acid catalysts and a cyclohexane solvent are fully dissolved, dispersed and continuously stirred for reaction; then, the cyclohexane solvent is recycled through pressure reduction distillation to obtain a coal pitch mixture, and the low-toxicity modified coal pitch for road building is prepared after vacuum drying. The method is simple in technology, low in modification temperature and little in modifier use amount, the solvent can be recycled, the content of 16 toxic polycyclic aromatic hydrocarbons detected by EPA in the modified coal pitch is greatly reduced, and the high-temperature coal pitch is modified into medium-temperature coal pitch.

Description

technical field [0001] The invention relates to a method for modifying coal tar pitch, in particular to a method for preparing low-toxicity modified coal tar pitch used for road construction. technical background [0002] Coal tar pitch is a bulk solid residual product obtained after deep processing of coal tar to extract useful components, accounting for 50-60% of the total amount of coal tar. At present, there is an overcapacity of coal tar pitch in my country, and the petroleum pitch used for road paving is relatively scarce. Considering that coal tar pitch has been widely used in road paving in foreign countries, its application has been greatly affected by the high content of toxic polycyclic aromatic hydrocarbons in coal tar pitch. limit. Therefore, the modification and detoxification of coal tar pitch before road construction application will solve the problem of excess coal tar pitch, make up for the shortage of petroleum pitch, and reduce the cost of road constructi...

AI Technical Summary

Problems solved by technology

Germany once used vacuum distillation (US5262043) to distill coal tar pitch under reduced pressure at a temperature of 300 to 380°C to obtain modified coal tar pitch containing 3,4-benzopyrene less than 50ppm, but the manufacturing cost of the process equipment is high and the consumption The energy is large, and the coal tar pitch is lost, and the performance is also deteriorated; the application of ultraviolet irradiation method is relatively seldom, Chinese scholar Li Ting once used UV-Fenton catalytic oxidation method to treat polycyclic aromatic hydrocarbons in oil extraction wastewater (Li Ting, Chen Bing, Ma Hong. Treatment effect of UV-Fenton catalytic oxidation method on polycyclic aromatic hydrocarbons in oil production wastewater [J]. Journal of Environmental Engineering, 2012, 6(10): 3475-3480.), under the irradiation of 254nm wavelength ultraviolet light, Fe 2+ dosage, H 2 o 2 The effect of dosage, pH value and light time on the treatment effect of polycyclic aromatic hydrocarbons phenanthrene and fluorene in water samples, the removal rate reached 71.9%. Considering the complex factors of ultraviolet irradiation method, it is not suitable for the removal of polycyclic aromatic hydrocarbons in coal tar pitch Treatment; the research on the treatment of polycyclic aromatic hydrocarbons by oxidation has also been reported. The oxidants used include ozone-containing air, Fenton’s reagent, potassium permanganate, etc., although they can be applied to the removal of polycyclic aromatic hydrocarbons in coal tar pitch. effect, but it may also cause coal tar pitch to oxidize and age in advance, affecting the performance of coal tar pitch; the number of literature and patents on coal tar pitch modification by polymer method is relatively large, and the modification effect either focuses on the improvement of asphalt performance, or has a certain detachment effect. For toxic purposes, most of them do not combine the two relatively comprehensively, and the types of polymers used are also very wide. They are mostly transplanted into rubbers and resins used in the modification of petroleum asphalt.

[0004] The publication number is CN103834421A and the name is "an environment-friendly modified coal tar pitch and its preparation method". The medium and low temperature coal tar pitch is used as the raw material, benzoic anhydride or maleic anhydride is used as the modifier, and the solvent uses a composite solvent cyclohexane alkane and toluene or cyclohexane and butyl acetate, the reduction rate of 3,4-benzopyrene in the prepared environmentally friendly modified coal tar pitch reaches more than 90%, but for the modification of high temperature coal tar pitch and the modified coal tar pitch Performance studies were not discussed stating

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