Influence of demineralization on minerals and organic structure in Huadian oil shale

Effect of demineralization on minerals and organic structure of Huadian oil shale treated by HCl and HF/HCl sequentially was examined using FT-IR and XRD technology. The results show that HCl/HF treatment can effectively remove minerals except pyrite, but HCl can damage the space frame structure of kaolinite. Organic matter structure with the form of disordered amorphous polymers are mainly composed of aliphatic structure in lower metamorphic grade. Acid treatment effect on shale organic macromolecular structure is very low, but has certain influence on the organic structure. HCl treatment mainly influences oxygen containing functional group and benzene ring structure, generates a large amount of carboxylic acid and destroys the polycyclic structure of benzene ring, but has less effect on aliphatic compounds. HF treatment main affects aliphatic compounds, it can destroy the fat chain bridge bond structure fracture, makes fat chain length shorter and decreases content of aliphatics in the samples. Both HF and HCl treatment can destroy the hydroxyl groups of shale, especially for the associated hydroxyl hydrogen bond.