Calcination and graphitization behaviour of cokes from Ql-free coal-derived pitches

Abstract

Coal tars and coal liquefaction products are possible feedstocks for anisotropic carbon material production. Semi-coke samples were produced from coal tar pitch, CTP 101 and coal hydrogenation pitch, CHP 88, prepared in a laboratory scale from QI-free parent liquids. Changes in the structure and properties of the semi-cokes, during two stage calcination and graphitization treatment up to 2700 °C, were evaluated. Both pitches produced highly anisotropic semi-cokes, slightly differing in the distribution of microconstituents revealed by optical texture. The calcined coke from coal tar pitch CTP 101 was distinguished by higher real density and porosity, lower heteroatom (N + O) content and microstrength and slightly higher graphitizability. The increase of heating rate in the temperature range 500–850 °C from 5 to 100 K min −1 induced negligible alteration in the properties of calcined cokes. The more intensive evolution of nitrogen on heating between 1300 and 1700 °C of the CHP 88 coke was associated with larger development of porosity in the coke grains, corresponding to greater puffing. The lower extent of puffing favours the QI-free coal tar rather than the coal hydrogenation product as a feedstock for electrode coke production.