Insights into the Key Factor of Zeolite Morphology on the Selective Conversion of Syngas to Light Aromatics over a Cr2O3/ZSM-5 Catalyst

One-step conversion of syngas to aromatics (STA) over an oxide-zeolite bifunctional catalyst is promising as an alternative route for aromatic production. Control of aromatic distribution and enhancement of benzene, toluene, and xylene (BTX) selectivity are still a big challenge. Decoupling the complex reaction network, the relative activity of aromatization and alkylation on ZSM-5 determines the aromatic distribution. Herein, the STA reaction was studied over Cr2O3/ZSM-5 to reveal the influence of the zeolite morphology parameters on aromatic distribution. Using the substitution ratio of aromatic ring SC9+/A to reflect the relative rate of alkylation to aromatization, the linear dependence of SC9+/A on the morphology parameter (1/b) of ZSM5 was revealed. The methodology for control of aromatic distribution by altering the crystal size of ZSM-5 along the b-axis is then proposed. By further enhancing the aromatization activity via ion exchange of Zn to ZSM-5, a bifunctional catalyst showing a high BTX space time yield of 2.47 mmol g(-1) h(-1) (on carbon base) with 49.1% BTX fraction is developed.