The catalytic effects of five metal chlorides, including CaCl2, KCl, NiCl2, CoCl2, and ZnCl2, on the pyrolysis
of lignite were investigated by thermogravimetry Fourier transform infrared (TG-FTIR) analysis. The results
showed that CaCl2 and ZnCl2 inhibited the conversion of organic matters into light species during pyrolysis
of lignite samples, while KCl, NiCl2, and CoCl2 promoted the conversion. The catalytic effectiveness of these
metal chlorides on the conversion of organic matters in lignite samples decreased in the following order:
CoCl2 > KCl > NiCl2 > CaCl2 > ZnCl2. The yields of light species from lignite pyrolysis can be decreased
by CaCl2. The effect of NiCl2 was similar to that of CaCl2 except it increased the yield of CO2. When CoCl2
or ZnCl2 was impregnated into lignite samples, the yields of monocyclic aromatic hydrocarbon, phenol, and
carboxylate increased but the yield of aliphatic hydrocarbon decreased. The effect of KCl was opposite to that
of CoCl2 and ZnCl2. These chlorides were analyzed by X-ray diffraction (XRD) before and after pyrolysis.
The XRD results indicated that the catalytic active sites of alkali or alkaline earth metal (AAEM) chlorides
catalysts were the interactions between the AAEM species and oxygen-bearing anions. However, the catalytic
activities of transition metal chlorides might be in their metallic state. In addition, the effects of CoCl2 on the
pyrolysis of raw lignite have also been investigated with a spout-entrained reactor. The results suggest that
impregnating 15% CoCl2 to lignite can increase the yields of total volatile matters more than 2-fold. The
catalytic effect of CoCl2 impregnated to zeolite is lower than that directly impregnated to lignite. However,
catalytic pyrolysis of lignite with Co-zeolite should be feasible in an industrial setting because it is easy to
separate and recycle.
The hollow porous MgO microspheres have been synthesized through a simple in situ chemical vapor deposition method, and the investigations reveal that Zn in raw source is key and possibly acts as an interim template in the formation of MgO hollow-sphere morphology.
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