Research On The Free Radicals In The Coal And Pyrolysis Products

Analysis on coal pyrolysis products is useful to understand the relationship between the pyrolysis conditions and the pyrolysis products, it is very helpful to establish a method of controlling free radical reaction in coal pyrolysis, and to improve the oil and gas yield and quality, it also can provide theoretical basis for the further study of coal pyrolysis mechanism. Due to the lower sensitivity and the longer testing time, the more precise test results for some unstable products would be not obtained by using 13NMR or 13CP/MAS that the methods were usually adopted in previous studies. In this paper, the solid, liquid and gas products in coal pyrolysis process were studied by using EPR.Using the standard curve method established by our lab, the changes of the free radicals from coal pyrolysis solid products which generated under different conditions, eg. temperature (350℃-600℃), holding times (0-30min), atmospheres (N2 and CO2), place the coal formed in (Xinjiang and Shengli), and pretreatments with hydrogen donor reagent (H2O and 1,2,3,4-Tetrahydronaphthalene) were compared and researched. In addition, the methods of qualitative and quantitative analysis of the free radicals from coal pyrolysis liquid products by EPR were initially established.The results showed that the EPR method was rapid and direct; the determination of free radical concentration in coal based on standard curve method was more accurate; the changes of the free radicals from Xinjiang long flame coal pyrolysis solid products were the same as Shengli lignite's; but in the behaviors of pyrolysis there were some differences between them; after the pretreatment, the yield of oil and gas of Xinjiang long flame coal was decreased, the condensation reaction among the free radicals had been restrained to a certain degree; the higher temperature in pretreatment, the more heteroatoms were removed; the yield of oil and gas of Shengli lignite in N2 atmosphere was lower than the yield of oil and gas in CO2 atmosphere, but the Ng in N2 atmosphere was higher than the Ng in CO2 atmosphere; the free radicals from coal pyrolysis liquid products were probably N-O radicals;by using capsules, the problem of weighing liquid sample was solved.