To reveal the soot formation characteristics of lignite and the role of Na in coal-derived soot formation

inductively coupled plasma emission spectrometer

X-ray photoelectron spectroscopy

fourier transform infrared absorption spectrometer and other methods were used to study the yield

surface and overall chemical properties of soot produced by the pyrolysis of acid-washed Yimin lignite loaded with blank

physically adsorbed Na (ANa) and ion-exchangeable Na (INa) under different residence time in a drop-tube reactor. The results show that during the surface growth stage of lignite derived soot

the increase of soot yield is far more than the decrease of tar yield. When the residence time is long enough

soot yield decreases and oxygen-containing functional groups content increases. Loading Na can reduce soot yield

but INa has much stronger inhibitory effect on soot than ANa

and INa also can increase ether and sulfone content in pyrolysis aerosol. These phenomena indicate that during lignite secondary pyrolysis

small molecular aromatic compounds

aliphatic substances and light gases would also increase soot yield through surface growth. Oxygen-containing substances in lignite pyrolysis gas can exhibit oxidation of soot when the residence time is long enough. INa can maintain the organic binding state with char or volatiles

reduce primary tar release in primary pyrolysis

and promote the combination of volatiles and oxygen-containing substances in secondary pyrolysis. But ANa has no obvious effect in primary pyrolysis. In the second pyrolysis

gasified ANa and INa have the same mechanism of inhibiting soot formation.