Preferential oxidation of carbon monoxide over Pt–FeOx/CeO2 synthesized by two-nozzle flame spray pyrolysis
Preferential oxidation of carbon monoxide over Pt–FeOx/CeO2 synthesized by two-nozzle flame spray pyrolysis
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DOI：
10.1016/j.jcat.2015.05.003
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发表时间：
2015-09
影响因子：
7.3
通讯作者：
Jochen A. H. Dreyer;Henrike K. Grossmann;Jinfan Chen;T. Grieb;Bill Gong;P. Sit;L. Mädler;W. Y. Teoh
中科院分区：
文献类型：
--
作者：
Jochen A. H. Dreyer;Henrike K. Grossmann;Jinfan Chen;T. Grieb;Bill Gong;P. Sit;L. Mädler;W. Y. Teoh
采用双喷嘴火焰喷雾热解法制备了具有可控分凝的Pt-FeOx-CeO2催化剂，用于CO(CO-prox)的优先氧化。这是通过在两个界面火焰中单独火焰喷涂两种活性成分来实现的。通过调整两个气溶胶火焰之间的相交距离，可以调节催化剂的形貌和还原能力。在最大的火焰距离下，铂/FeOx2和CeO2之间的亲密相互作用(两组分没有过烧)在最低温度下提供了还原能力，这对应于在铂周围形成氧空位(来自H溢出)。在90℃以下，双喷嘴合成催化剂的最大CO转化率(>；99.5%)比机械混合的铂/FeOxCeO2催化剂低30℃。虽然在较低的温度下获得了较高的CO2选择性，但它受到了活性氧吸附的限制。由于未消耗氧气，催化剂上的氧空位在低温下逐渐被氧化，导致CO转化率随投产时间的延长而下降。相反，O2的完全消耗和过量的游离H_2在高温下保持了高的氧空位含量，因此获得了高活性(尽管不是选择性的)。我们进一步确定了在高温下二氧化碳选择性的丧失是由于在氧空位存在的情况下，与H_2的吸附相比，CO的吸附减弱。
Pt–FeOx–CeO2catalysts for the preferential oxidation of CO (CO-PROX) with controllable segregation between the Pt/FeOxand CeO2components were synthesized by two-nozzle flame spray pyrolysis. This was achieved by flame-spraying the two active components independently in two interfacing flames. By adjusting the intersection distance between the two aerosol flames, it was possible to tune the morphology and the reducibility of the catalysts. Intimate interactions between Pt/FeOxand CeO2(without oversintering the two components) achieved at the greatest flame distance gave reducibility at the lowest temperature, as corresponding to the formation of oxygen vacancies around the Pt (from H-spillover). Maximum CO conversion (>99.5%) for the two-nozzle synthesized catalysts was achieved below 90 °C, which is 30 °C lower than for mechanically mixed Pt/FeOxand CeO2. While high CO2selectivity was attained at lower temperatures, it was limited by the adsorption of reactive oxygen. The oxygen vacancies on the Pt–FeOx–CeO2catalyst were gradually oxidized at low temperatures due to unconsumed O2, and this led to a decrease in CO conversion with time on stream. In contrast, complete consumption of O2and excess of dissociated H2sustained the high oxygen vacancies content at high temperatures and hence high activity (although nonselective) was achieved. We further identified the loss of CO2selectivity at high temperature as originating from the weakened CO adsorption compared to that of H2in the presence of oxygen vacancies.