Dispersed Pd/alumina catalyst with finite iodine entry for boosted CO purification and dimethyl carbonate synthesis
Sintering caused catalyst deactivation resulting from the agglomeration of active metal sites. CH 3 I/CO based approaches are attractive owing to their effectiveness and mildness in rejuvenating sintered catalysts. However, few investigations have been reported for their application in oxides-supported catalysts. Herein, a landscape of reversible structural transformation of Pd/γ-Al 2 O 3 catalyst is depicted. The scenario of Pd redispersion in γ-Al 2 O 3 is significantly different from previously reported activated carbon-supported metal catalysts. Time-controlled CH 3 I/CO treatment facilitates the rapid redispersion of aggregated Pd particles on γ-Al 2 O 3 surface. The redispersion of Pd promotes the reactivity of Pd/γ-Al 2 O 3 catalyst. For dimethyl carbonate synthesis, the space-time yield increases from 556.9 g DMC ·kg cat. −1 ·h −1 to 1008.9 g DMC ·kg cat. −1 ·h −1 . For CO purification, 100% conversion of H 2 impurities and the rise of 27.4% in selectivity are achieved. The intrinsic oxidation rate is elevated from 607.8 mmol H2 ·g Pd −1 ·h −1 to 1166.5 mmol H2 ·g Pd −1 ·h −1 . However, complete oxidation and atomic dispersion of Pd cannot be achieved through further treatments. Combined characterizations verify the particle reconstruction of Pd and the evolution of anchoring sites on γ-Al 2 O 3 via strong metal-iodine binding. It reveals a double-edged-sword character of CH 3 I for Pd redispersion, wherein the excessive treatment results in re-aggregated Pd particles and inferior reactivity.
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