Regulating anisotropic diffusion in zeolite for reinforced para-xylene synthesis via CO2 hydrogenation in the presence of toluene

Abstract

The synthesis of valuable aromatics via CO transformation, especially -xylene (PX), is of paramount significance but still remains greatly challenging due to the low efficiency and poor selectivity. The present work utilized a composite catalyst based on ZnZrO with a modified H-ZSM-5 exhibiting nano-prism stacking to realize the selective synthesis of PX. Methoxy species generated from CO-derived formate produced as an intermediate over the ZnZrO were readily incorporated into the xylene products for effective alkylation, contributed to an enhanced aromatics-based cycle that provided a selectivity for xylenes among all C hydrocarbons of 91.1 %. The lengthened straight channels in the H-ZSM-5 along the -axis, derived from the crystal stacking pattern, increased differences in the diffusion properties of the xylene isomers, and thereby steering the movement of molecules toward a product shape-selective pathway, leading to 90.1 % selectivity for PX among all xylenes, and provided exceptional CO utilization efficiency of ∼60 %.