Carbonization of coal tar pitch denitrogenated by metal sulfates

After adsorbtion removal of nitrogen compounds with dried metal sulfates, carbonization of extracted fractions from a coal tar pitch (CTP, N = 1.1 wt %) was studied for production of needle coke of low nitrogen content without puffing since nitrogen in the coke is believed to provoke puffing at rapid graphitization. A nitrogen-free coke (N, 0.01 wt%) with excellent flow texture was produced from the early two eluents of MI-TS (methanol-insoluble but toluene-soluble) by removing the basic nitrogen compounds through the sulfate column. Adsorbing denitrogenation through batch treatment with the supported sulfate also significantly reduced the nitrogen content of cokes produced from TS (toluene-soluble) without deterioration of their anisotropic texture. A low-nitrogen coke (N, 0.26 wt %) from the denitrogenated TS exhibited much smaller volume increase of micropores (< 0.1 μm) after rapid graphitization than coke from the original CTP, suggesting very little puffing. The efficiency of combining extractive fractionation for NH species with adsorbing separation of basic nitrogens is briefly discussed for practical application in order to minimize the amount of adsorbent.