Bonding energy and methane amount at the open surface of metamorphic coal

Objective of the studies is to measure and determine regularities of changes in adsorption and methane energy bond with the open surface of mineral carbons within metamorphism series. Donbas mineral carbons have been used as the samples. Volumetric method has been applied in the range of room temperatures and pressures of free methane phase (i.e. 0.015 to 3.5 MPa) to measure methane amount at the open surface of the mineral carbons. Depending upon changes in carbon content, adsorption behaviour is close to parabolic one: adsorption is maximal on the peripheries of metamorphic series, and minimal within its central part. For the first time, methane energy bond with the open surface of mineral carbons has been determined. In the context of the metamorphic series, bonding energy varies from 2 to 10 kJ/mol. Direct linear dependence of adsorption from pressure takes place for coal where carbon content is less than 76 %. It is the result of effect of large area of open surface of low-metamorphized coal. Inversely, nonlinear dependence is observed as for anthracite. The authors connect the fact with filling of all spaces at the open surface when gas phase pressure is 0.1 MPa