Conversion of low temperature coal tar into high value-added chemicals based on the coupling process of fast pyrolysis and catalytic cracking

Abstract

To convert the Xinjiang low temperature coal tar (XJ-CT) into high value-added chemicals, the coupling process of fast pyrolysis and catalytic cracking (FP-CC process) is proposed, and the related fundamental data is collected in this research. First, the composition of XJ-CT is analyzed by GC-GC/MS, and the result shows that the relative contents of alkanes, alkenes, aromatics, and the oxygen compound are 13.16%, 4.85%, 48.38%, and 29.29%, respectively. Then, the performance of XJ-CT fast pyrolysis is evaluated under different reaction temperature. The results show that aromatics is predominant among the pyrolysis vapor, whereas the yield of aliphatic products enhances with the increase of temperature. And the aliphatic products are mainly formed from the deep cleavage of long-chain aliphatics and alkyl side chains (alkyl bridge chain) of aromatics. Meanwhile, the relative content of oxygen-containing compounds decrease with the increase of temperature. Furthermore, molecular distributions of the major groups in pyrolysis vapor with different temperatures are summarized to gain insight into the pyrolysis process. Finally, the ZSM-5 (40), ZSM-5 (200), and USY zeolite are used to catalyze the pyrolysis vapor. It is demonstrated that the maximum light olefin yield of 31.79% is obtained over ZSM-5 (40), while converting XJ-CT to liquid fuels can be realized on USY zeolite.