Influence Of Group Maceral On Adsorption Of Sc-CO₂ Extracted Coal And Its Mechanism

Three sets of low-order coal samples from the Ordos Basin were chosen for this study,and rich vitrinite and rich inertinite samples were obtained by the heavy liquid separation method,and tests with supercritical extraction were conducted in a TC-2supercritical extraction device.The change of coal pore structure by Sc-CO₂ and its link to group maceral are being investigated based on the findings of samples’pressure mercury and cryogenic liquid nitrogen tests conducted before and after Sc-CO₂ extraction.Investigating the impact of Sc-CO₂ extraction on sample chemical structure and its connection to group maceral based on the findings of industrial analysis,elemental analysis,and Fourier infrared spectroscopy test results.In light of this,coupling study of samples’altered adsorption due to Sc-CO₂ extraction in relation to altered pore structure and altered chemical structure,and investigating potential control mechanisms of group mackerel on the adsorption of Sc-CO₂ coals were conducted.Research led to the conclusions that are presented below.（1）After Sc-CO₂ extraction,The micron pore volume and pore specific surface area overall increase at all phase for the rich vitrinite and rich inertinite coals,and the rich vitrinite coals has more significantly modified.The micropore volume and pore specific surface area of the rich vitrinite coals are more strongly modified than the rich inertinite coals,but the transitional,medium and large pore volumes and pore specific surface area modifications are weaker than for the rich inertinite coals.The nanometer pore volume and pore specific surface area of the rich vitrinite coals overall decrease at all phase,and the nanometer pore volume and pore specific surface area of the rich inertinite overall increase at all phase,but the rich inertinite coals are more significantly modified.The super microporous,micropore and transition pore volumes and pore specific surface area modification of the rich inertinite coals are stronger than the rich vitrinite coals.The pore connectivity of the rich vitrinite and rich inertinite coals are improved by Sc-CO₂ extraction.Considering that Sc-CO₂extraction has a significant modification effect on the pore structure of the rich vitrinite and rich inertinite coals,specifically in terms of pore enhancement and expansion effects.The rich vitrinite coals show a more significant porosity expansion effect,and the rich inertinite coals show both porosity increase and porosity expansion effects.（2）Sc-CO₂ extraction was found to have a significant modification effect on the water,carbon,oxygen,hydrogen,nitrogen,aliphatic hydrocarbons,aromatic hydrocarbons and oxygen-containing functional groups of the rich vitrinite coals than the rich inertinite coals,but the ash,volatile matter,fixed carbon,sulphur and hydroxyl functional group modifications are weaker than the rich inertinite coals.It was also found that the aromaticity,relative hydroxyl content,length of fatty side chains and relative content of oxygenated functional groups of the rich vitrinite coals are more strongly modified by Sc-CO₂ extraction than the rich inertinite coals,and the modification of the degree of polymerisation of aromatic rings is weaker than the rich inertinite coals.（3）The Langmuir equation is a good fit for isothermal sorption data before and after Sc-CO₂ extraction.The methane adsorption capacity of the coal is generally decrease after Sc-CO₂ extraction,and the decrease is more significant in the rich inertinite coals.By using Sc-CO₂ extraction,it was discovered that the adsorption of the the rich vitrinite coals decreased with increasing super microporous,microporous pore volumes and pore specific surface area,ash and relative oxygen-containing functional group content,and increased with increasing lipid side chain length.Through Sc-CO₂ extraction,the adsorption of the rich inertinite coals reduces with increasing super micropore,micropore pore volume and pore specific surface area and ash,and increases with increasing lipid side chain length and relative hydroxyl content.As can be seen,changes in ash,fat side chain length,and the relative content of oxygenated functional groups have the greatest impact on the change in adsorption of the rich vitrinite coals after Sc-CO₂ extraction,whereas changes in ash,fat side chain length,and the relative content of hydroxyl groups have the greatest impact on the change in adsorption of the rich inertinite coals after Sc-CO₂ extraction.The main factor influencing the alteration of the adsorption capacity of Sc-CO₂ extraction coals is thought to be structural functional group change.There are 56 figures,17 tables and 145 references in this thesis.