Study on ammonia poisoning of Pd system catalyst for CO coupling reaction to diethyl oxalate

The effect of ammonia of different contents on the activity of Pd system catalyst for CO coupling reaction to diethyl oxalate was experimentally studied. The deactivation rate of the catalyst was getting faster and faster with increasing ammonia contents. Ammonia, ≯ 0.54%, only caused the catalyst activity to decrease. However, the catalyst was rapidly poisoned until full loss of the catalytic activity when ammonia content was up to 1.16%. After removing ammonia from the reaction system, the activity of the poisoned catalyst could not be fully recovered. The mechanism of ammonia poisoning for Pd system catalyst and the reasons for irreversibility of ammonia poisoning under reaction conditions were discussed based on XPS and TEM measurement results of the catalyst.