New Insight into the Antagonism Mechanism between Binary VOCs during Their Degradation over Pd/ZrO2 Catalysts

The catalytic oxidation technology has been extensively employed for the control of air pollution caused by the large emissions of volatile organic compounds (VOCs). However, compared with the widespread research on single-component VOC elimination over supported Pd catalysts, the control of miscellaneous VOCs simultaneously and the revelation of their mutual influence still need to be solved eagerly. Herein, a mutual influence different from mutual inhibition or mutual promotion was revealed during the typical VOC mixture (toluene and acetone) degradation over metal-organic frameworks-derived Pd/ZrO2 catalysts by a series of experiments and characterizations. The results showed that an antagonism effect was observed between toluene and acetone during their mixture degradation; namely, acetone suppressed toluene oxidation, whereas toluene did not inhibit acetone degradation but promoted its degradation weakly. The mechanism was proposed in which the competitive adsorption inhibited the occurrence of acetone adsorption polymerization reaction to form mesityl oxide (MSO) at low temperatures, which induced the release of surface-active sites to enhance acetone oxidation. However, the polarity of acetone molecules induced its strong adsorption on the catalyst surface, which greatly suppressed toluene adsorption and the ring-opening reaction to generate maleic anhydride, weakening its degradation. This work provides guidance for supported Pd catalyst design for multicomponent VOC elimination.