Effect of boron incorporation in MOR zeolite on the carbonylation of dimethyl ether to methyl acetate

The incorporation of boron(B) into MOR zeolite offers a promising avenue for enhancing the catalytic performance in the carbonylation of dimethyl ether (DME) to methyl acetate (MA), a pivotal step in coal-to-ethanol processes. In this study, different contents of H₃BO₃ were introduced during the synthesis of MOR zeolites to develop H-MOR(nB) catalysts with tailored acidic properties. Comprehensive characterization techniques, including XRD, ICP-AES, FTIR, Raman, NH₃-TPD, NH₃-IR,¹¹B MAS NMR and ²⁷Al MAS NMR, revealed that B incorporation didn’t alter the crystal structure of MOR zeolite but significantly influenced the acidic sites distribution. Specifically, the introduction of B enhanced the proportion of active T3 sites within the eight-membered ring side pockets (8-MRS) while reduced deactivation-prone T4 sites in the twelve-membered rings(12-MR). These modifications increased the Brönsted acid site (BAS) content and strength in the 8-MRS, improving catalytic performance. Among the tested samples, H-MOR(7.8B) achieved the highest DME conversion (43%) and MA selectivity (97.5%), with better stability than that of H-MOR(0B) under reaction conditions. These findings were further supported by density functional theory (DFT) calculations. This work provides valuable insights for optimizing MOR zeolite acidity in DME carbonylation processes.