Rational design of Ga-substituted NaY zeolites with controllable acidity for remarkable carbonylation of methyl nitrite to dimethyl carbonate

Lack of high performance and stability catalysts remains a technical bottleneck for the industrialization of methyl nitrite (MN) carbonylation to dimethyl carbonate (DMC). Lewis acidity is crucial for catalytic performance in MN carbonylation reaction, but the regulation of Lewis acid sites and the effects of Lewis acid strength on catalytic performance have not been clarified. Thus, rational design of NaY zeolites with controllable acidity is an effective strategy to promote their catalytic performance. Herein, we substituted Ga for partial framework Al to produce a series of NaGaY-x (x = 0 similar to 2) zeolites with different Ga content via direct hydrothermal method and applied in this reaction. The results showed that the Lewis acid strength increased upon an appropriate amount of Ga incorporation, thereby the electron density of Pd2+ could be regulated. The optimal electron density of Pd2+ promotes the carbon monoxide (CO) adsorption and activation, which contribute to the formation of the critical intermediate species *COOCH3. Eventually, the Ga-modified PdCu/NaY catalyst exhibited remarkable catalytic activity for MN carbonylation to DMC with the weight-time yields (WTYDMC) of 1251 g.kg(cat)(1).h (1), and the CO conversion to DMC (C-CO) of 69.2 % as well as the DMC selectivity based on CO (S-DMC/CO) up to 100 %. Our work paves the way to further understand the synergistic effect between Pd2+ and Lewis acid, assists in the devel-opment of high-performance MN carbonylation catalysts.

Automated summary

The lack of high performance and stability catalysts has hindered the industrialization of methyl nitrite (MN) carbonylation to dimethyl carbonate (DMC). In this study, NaGaY-x (x=0 to 2) zeolites with different Ga content were designed and applied in the reaction. The incorporation of Ga was found to increase the Lewis acid strength and regulate the electron density of Pd2+. The optimized electron density promoted CO adsorption and activation, leading to high catalytic activity for MN carbonylation to DMC.