Directional preparation of naphthalene oil-rich tar from Beisu low-rank coal by low-temperature catalytic pyrolysis

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Low-rank coal (LRC) can be converted to high value-added naphthalene and its alkylated derivatives through low-temperature catalytic pyrolysis. In this paper, the catalytic pyrolysis of Beisu LRC in a fixed-bed at low temperature was investigated. And the catalytic effects of HZSM-5, low-temperature carbocoal (LtC), and LtC-HZSM-5 on the content and yield of naphthalene oil were examined. The results showed that the generation of naphthalene oil in low-temperature LRC pyrolysis (LT-LP) process could be improved when LtC (prepared at 550 °C) or HZSM-5 was individually used as a catalyst. Compared with sole pyrolysis of raw LRC, the addition of the LtC-HZSM-5 catalyst increased the content of naphthalene oil from 11.19 wt.% to 31.49 wt%. And the yield of naphthalene oil was increased from 1.07 wt% to 5.31 wt%. The reactions of micromolecular hydrogen-containing radicals (·MHCR) were optimized by LtC. ·MHCR could be captured in relatively low-temperature region (200–400 °C) and released at high temperature by LtC. The generation of phenolics was inhibited by HZSM-5. As a result, the naphthalene oil-rich tar was obtained through low-temperature LtC-HZSM-5 catalytic pyrolysis of Beisu LRC.