INFLUENCE AND MODIFICATION OF THE POROUS TEXTURE OF COALS DURING HYDROGENATION

A series of coals ranked from lignite to bituminous were hydrogenated at 300, 350 and 400 degrees C in the absence of a solvent and with a hydrogen pressure of 5 or 10 MPa. Conversion percentages and yields of reaction products (oils and asphaltenes) were related to coal textural characteristics. Changes in the textural parameters during hydrogenation were determined with the object of studying the reaction mechanism from a textural viewpoint. The results indicate that an increase in both macropore and micropore volume favours reaction development. Under mild conditions, or at the start of the reaction, conversions are low, but the process provokes an increase in pore size which favours reaction development towards the narrower pores. Repolymerization occurs at 5 MPa, increasing with temperature and leading to increased macroporosity.