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Enhanced thermal stability of palladium oxidation catalysts using phosphate-modified alumina supports

机译：增强的热稳定性氧化钯催化剂使用phosphate-modified氧化铝支持

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摘要

A group of phosphate-modified alumina materials with enhanced thermal stability was developed in this work. Using these oxides, supported Pd catalysts experienced much less deterioration after aging at 1050 degrees C for 10 h. The CO oxidation kinetic results showed that the phosphate additives did not change the intrinsic activity of the Pd catalytic centers and the larger population of sinter-resistant Pd species anchored on the phosphate-stabilized alumina was the direct reason behind this improved catalytic performance. Combining the analyses of NMR, IR, pyridine adsorption and DFT simulations, the phosphate adsorption and evolution behaviors on the alumina surface were explored at different phosphorus contents. The effective phosphate stabilizers prefer to coordinate with the surface coordinatively unsaturated -Al sites (CUS Al) and substitute the weakly adsorbed hydroxyls nearby. Such an interaction suppressed the phase transformation and grain growth of the alumina. Compared with the phosphate-free Pd catalyst, alumina with similar to 5.0 mu mol m(-2) phosphorus additives is able to retain 1.9 times higher Pd dispersion after aging, resulting in much higher CO oxidation activity. Further increase of the phosphorus content induced the formation of long-chain polyphosphate and harmed the stability of Pd, bringing no more benefits to the performance of the catalysts.
机译：一群phosphate-modified氧化铝材料与增强的热稳定性是发达这项工作。催化剂有经验更恶化老化后在1050摄氏度10 h。有限公司氧化动力学结果表明磷酸盐添加剂改变不了本质钯催化中心和活动更大的人口sinter-resistant Pd的物种固定在phosphate-stabilized氧化铝直接原因改善催化的性能。吡啶吸附和DFT模拟,磷酸吸附和演化行为氧化铝表面在不同的探索磷含量。稳定剂更愿意配合表面协调(CUS)和不饱和状态”网站替代附近的弱吸附氢氧根。这种交互抑制阶段转换和氧化铝的晶粒生长。与不含磷酸盐钯催化剂相比,氧化铝与类似于5.0μm摩尔(2)磷添加剂能够保留1.9倍更高的Pd分散后老化,导致更高的CO氧化活性。增加磷含量引起的形成长链多磷酸盐和伤害Pd的稳定性,将没有更多的好处催化剂的性能。

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