To investigate the effect of demineralization on Longkou oil shale

the oil shale was acid demineralised in three steps with HCl→HF→HNO3

XRD and FT-IR was respectively used to analysis the compounds of minerals the change of chemical structure information before and after acid-treatment. The results show that oil shale mainly contains four oxygen-containing function groups

ether oxygen

carboxyl

hydroxyl and carbonyl

organic matter made by acid-treatment is really pure

the ash weight percentage is less than 1% after acid-treatment. acid-treatment has effect on the chemical structure in oil shale

hydrolysis reaction is occurred during the acid-treatment

alkyl ether and aromatic ether in the oil shale is decreased after acid-treatment; Carboxylic acid and phenolic hydroxyl are obviously increased

this is because acid-treatment breaks the ion exchange interaction between oxygen-containing groups and inorganic salts

then organic salts convert into organic acid; Hydroxyl structure both mainly contains structures of ring hydroxyl

OH-O and OH-OH before and after the acid-treatment

The acid-treatment has obvious effect on ring hydroxyl

OH-O

and has little effect on OH-OH; To the aliphatic structure

Acid-treatment makes the CH stretching vibration and CH3 asymmetric stretching vibration convert to CH2 asymmetric stretching vibration

the aliphatic chain is becoming longer.