Dimethyl ether carbonylation over pyridine-modified MOR: Enhanced stability influenced by acidity

The stability of MOR zeolite in DME carbonylation is a primary constraint in the industrialization of ethanol synthesis from syngas. Pyridine adsorption is recognized as an efficient technique to improve stability and as such, this study focuses on the influence of Bronsted acid density and strength on the stability of H-MOR saturated with pyridine in the DME carbonylation process. The acid properties of H-MOR catalysts was adjusted by a simple but efficient procedure. The methods employed to generate quantitative results of the acid properties include FTIR for the O-H region, IR spectra for pyridine adsorption, as well as Pyr-TPD (to monitor the quantity and strength of acid sites). The results indicated that the concentration of Bronsted acid site strongly influences the stability of pyridine adsorption, which was further expounded by DFT calculations. In addition, the deactivation behavior of the catalyst with respect to Bronsted acid site strength in 12-MR channels was also explored by use of the DFT modelling method. It suggested that the coke intermediate formed in the 12-MR will lead to the desorption of neighboring adsorbed pyridine due to the steric effect, which contribute to an accelerated deactivation.