Conversion of Dimethyl Ether to Triptane-Rich Liquid Hydrocarbons on Pd-LaHY with a Hierarchical Porous Structure

Abstract

To obtain from dimethyl ether (DME) a mixture of liquid hydrocarbons enriched in isoalkanes, including triptane, catalysts based on HYh zeolite with a micro-meso-macroporous structure modified with lanthanum and palladium were used. The process was carried out under conditions typical for producing gasoline from synthesis gas (10 MPa, 340 °C, off-gas recirculation). Despite the rather harsh conditions for the synthesis of triptane, a mixture of hydrocarbons with a high content of isoalkanes (≥83 wt %, including triptane up to 17 wt %) is formed on the Pd-LaHYh/Al2O3 catalyst with high selectivity (≥88 wt %). The resulting product has a research octane number (RON) of 87, quite high for a product with low aromatics (4 wt %); is nontoxic; does not contain benzene, sulfur, and nitrogen oxides; and can be considered as a basic component of motor fuel. Features of the hierarchical porous structure determine the high C5+selectivity and stable operation of the catalyst for 72 h, which favorably distinguishes it from its analogue based on traditional microporous HY. The results obtained showed the prospects of zeolite HY with a hierarchical pore system in obtaining a triptane-rich hydrocarbon mixture from DME and will be used to develop new catalysts for the production of gasoline-range hydrocarbons from CO x and H2 in one stage and via the oxygenate synthesis.