Effect of Fe modified Zr-based montmorillonites on the pyrolysis behavior of Xinjiang Hefeng coal

A serial of Fe modified Zr-based montmorillonites were prepared by mechanical ball milling and their characteristics were depicted by X-ray diffractometer (XRD), N₂ adsorption-desorption instrument (BET), temperature-programmed desorption of ammonia (NH₃-TPD, H₂-TPD), X-ray photoelectron spectrometer (XPS). The results show that compared with 24ZrAM, when FeCl₃·6H₂O and FeCl₂·4H₂O are used as iron sources, Fe–O–Zr structure appears on the 3Cl⁻-24ZrAM and 2Cl⁻-24ZrAM catalysts. In the presence of Fe sulfate, the specific surface area of the catalysts decreases markedly. With the introducing of Fe, the total acid content of catalysts reduces. Wherein, 3Cl⁻-24ZrAM has the highest acid content and strongest acid strength. H₂-TPR shows that the temperature for Fe₂O₃ reduced to Fe₃O₄ in 3Cl⁻-24ZrAM, 2Cl⁻-24ZrAM and 3\rmNO_3^ - -24ZrAM is lower than 500 ℃. Then, the effect of catalysts on the pyrolysis behavior of Xinjiang Hefeng coal and the bridge bond cleavage mechanism of different model compounds were investigated in a fixed bed reactor. It is noted that compared with 24ZrAM, the fraction of coal tar pitch all declines under the action of Fe species. Among them, 3Cl⁻-24ZrAM has the highest cracking activity with the light tar fraction of 63%, which is 18.9% higher than that of 24ZrAM. Meanwhile, the content of light oil and phenol oil are 1.3 times and 1.4 times higher than that of 24ZrAM, respectively. As for long-chain hydrocarbons, a further decline by 0.7% is observed. In addition, the conversion rates of benzyl phenyl ether (BPE), dibenzyl and biphenyl increase by 5%, 1.6% and 43.9%, respectively.