Production of aromatic hydrocarbons from catalytic pyrolysis of Huadian oil shale using ZSM-5 zeolites as catalyst

Abstract

Aromatic hydrocarbons (AHs) are used extensively as industrial raw materials. In this study, ZSM-5 zeolites with different silicon/aluminum ratios (SAR = 25, 38, 50, and 70, denoted as Z5-25, Z5-38, Z5-50, and Z5-70), were used for the catalytic pyrolysis of Huadian oil shale to explore their potential for producing aromatic hydrocarbons. The pyrolysis experiments were performed in an aluminum retort with or without added ZSM-5 (10 wt.%). AHs production was evaluated through gas chromatography‒mass spectrometry analysis of the derived shale oil samples. The results showed that ZSM-5 catalysis decreased the shale oil yield from 9.33 wt.% to ∼6 wt.%, and increased the AHs content of shale oil from 2.88% to greater than 20%. Z5-25 and Z5-38 appeared to be suitable catalysts for catalytic pyrolysis, producing AHs contents of 59.39% and 56.46%, respectively. Furthermore, Z5-25 catalysis produced fewer monocyclic aromatic hydrocarbons and more polycyclic aromatic hydrocarbons than Z5-38 catalysis. A brief lumped reaction scheme was proposed for AHs formation from the catalytic pyrolysis of oil shale. The cracking of long-chain aliphatic hydrocarbons at the ZSM-5 surface followed by aromatization of small aliphatic hydrocarbons within the ZSM-5 microporous channel was assumed to be the main pathway for the formation of AHs from the catalytic pyrolysis of oil shale.