How Lennard-Jones potential drives gas desorption and compositional fractionation in pore networks: insights from experimental work

In this study, mesopore and micropore character of asphaltites, chemical nature and their relations with desorption of gas compounds were investigated. It is understood that micropores, which act as desorption channels, connect the mesopores, where majority of the gas content exist within, like bridges. This labyrinthine network is mostly connected. Relationship between compositional fractionation and Lennard-Jones potential are shown. Being less heterogeneous and with absence of coal-like cleat or fracture system, insights on the pore structure not only reveal character of asphaltites but also pave the way to understand desorption tendency of gas compounds from bituminous materials. The essential pore parameters were obtained by producing N₂ and CO₂ isotherms at low pressure. By using transmitting electron microscopy, images of pore structures were examined. Chemical character of the organic part and pore surfaces is revealed that organic radicals on the asphaltite pore surface exhibit similarities to other geological hydrocarbons. The gas content, composition data of the samples previously reported in a study (Soylu & Fişne, 2025) are used and their relations with pore structures are discussed.