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Direct synthesis of H2O2 over Pd/C catalysts prepared by the incipient wetness impregnation method: Effect of heat treatment on catalytic activity
Korean Journal of Chemical Engineering ( IF 2.7 ) Pub Date : 2020-01-01 , DOI: 10.1007/s11814-019-0417-5
Vu Thi Thuy Hang , Young-Min Chung

Although various Pd/C catalysts have been applied in the direct synthesis of H2O2, unsatisfactory H2O2 yields have been achieved. We systematically investigated the effect of heat treatment on the physicochemical properties of Pd/C catalyst, and thereby on the catalytic performance in the direct synthesis of H2O2. Pd/C catalysts prepared by the incipient wetness method were subjected to different heat treatments and applied in H2O2 synthesis. The calcination temperature was found to have a key role in determining the Pd nanoparticle (NP) size; calcination at 523 K yielded highly oxidized and small Pd NPs corresponding to the sub-nano domain (1.4–2.5 nm). This Pd/C catalyst is superior not only in promoting H2O2 formation, but also in suppressing the subsequent unfavorable H2O2 decomposition and hydrogenation, which explains its excellent H2O2 productivity (as high as 4,443 mmol H2O2/g Pd·h) and selectivity (94.5%). On the other hand, the reaction performance of the Pd/C catalysts calcined at a higher temperature (673 K) or reduced under hydrogen was sharply reduced owing to the formation of larger Pd NPs or the enhancement of the metallic nature of Pd, respectively The amount of residual Cl ion on Pd/C catalyst after heat treatment also had an impact on the catalytic activity as it affected the pH of reaction solution. These results clearly demonstrate that an efficient Pd/C catalyst can be realized by fine tuning the conditions of heat treatment during catalyst preparation.

中文翻译:

用初湿浸渍法制备的 Pd/C 催化剂直接合成 H2O2:热处理对催化活性的影响

尽管各种 Pd/C 催化剂已应用于 H2O2 的直接合成,但 H2O2 的产率并不令人满意。我们系统地研究了热处理对 Pd/C 催化剂理化性质的影响,从而影响了直接合成 H2O2 的催化性能。通过初湿法制备的 Pd/C 催化剂经过不同的热处理并应用于 H2O2 合成。发现煅烧温度在确定 Pd 纳米颗粒 (NP) 尺寸方面具有关键作用;在 523 K 下煅烧产生了对应于亚纳米域 (1.4-2.5 nm) 的高度氧化和小的 Pd NP。这种 Pd/C 催化剂不仅在促进 H2O2 形成方面具有优越性,而且在抑制随后不利的 H2O2 分解和加氢方面,这解释了其出色的 H2O2 生产率(高达 4,443 mmol H2O2/g Pd·h)和选择性(94.5%)。另一方面,由于形成较大的 Pd NPs 或 Pd 金属性质的增强,在较高温度(673 K)下煅烧或在氢气下还原的 Pd/C 催化剂的反应性能分别急剧降低。热处理后Pd/C催化剂上残留的Cl离子量也对催化活性有影响,因为它影响了反应溶液的pH值。这些结果清楚地表明,通过微调催化剂制备过程中的热处理条件,可以实现高效的 Pd/C 催化剂。在较高温度(673 K)下煅烧或在氢气下还原的 Pd/C 催化剂的反应性能分别由于形成较大的 Pd NPs 或 Pd 金属性质的增强而急剧降低 残留 Cl 离子的量热处理后的 Pd/C 催化剂对催化活性也有影响,因为它影响了反应溶液的 pH 值。这些结果清楚地表明,通过微调催化剂制备过程中的热处理条件,可以实现高效的 Pd/C 催化剂。在较高温度(673 K)下煅烧或在氢气下还原的 Pd/C 催化剂的反应性能分别由于形成较大的 Pd NPs 或 Pd 金属性质的增强而急剧降低。热处理后的 Pd/C 催化剂对催化活性也有影响,因为它影响了反应溶液的 pH 值。这些结果清楚地表明,通过微调催化剂制备过程中的热处理条件,可以实现高效的 Pd/C 催化剂。
更新日期:2020-01-01
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