Indirect oxidative carbonylation of methanol to dimethyl carbonate on Pd/NaY: high stability by ethylenediamine as polydentate ligands

A series of Pd/NaY catalyst with different Pd complexes (Pd(NH 3 ) 4 /NaY, Pd(en) 2 /NaY, Pd(py) 2 /NaY and Pd(NH 2 CH 2 COO) 2 /NaY) were prepared as catalysts for the indirect oxidative carbonylation of methanol to dimethyl carbonate (DMC). The Pd complex ([Pd(en) 2 ] 2+ , [Pd(py) 2 ] 2+ and Pd(NH 2 CH 2 COO) 2 ) were produced as new active components. Among them, the Pd(en) 2 /NaY catalyst performed best with the CO conversion of 41.7 %, the DMC selectivity based on CO of 99.8 % for a 100 h test. On the other hand, the CO conversion decreased from 41.9 % (1 h) to 22 % on Pd(NH 3 ) 4 /NaY catalyst within 56 h reaction. It was found that the Pd(en) 2 /NaY catalyst had homogeneous and steady clusters, which can be attributed to interactions between the ethylenediamine ligands and Pd clusters. This work not only explained the deactivation of Pd/NaY catalyst, but also provide a useful method to stabilize catalysts.