Adsorption, surface reactions and hydrodeoxygenation of acetic acid on platinum and nickel catalysts
Adsorption, surface reactions and hydrodeoxygenation of acetic acid on platinum and nickel catalysts
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DOI：
10.1016/j.jcat.2023.01.013
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发表时间：
2023-01-25
影响因子：
7.3
通讯作者：
Podkolzin, Simon G.
中科院分区：
文献类型：
--
作者：
Ezeonu, Lotanna;Tang, Ziyu;Podkolzin, Simon G.
用红外反射-吸收光谱（IRAS）和程序升温脱附研究了乙酸在Pt（111）和Ni（110）上的吸附和表面反应，并在同一个定义明确的单晶表面上用密度泛函理论进行了计算.为了与Pt（111）进行比较，对Ni（111）进行了额外的计算。在高乙酸暴露在90 K的给药温度下，乙酸形成由物理吸附的多层覆盖的化学吸附层。化学吸附层在90 K的Pt和Ni含有分子吸附的乙酸以及乙酸的混合物。物理吸附的多层膜在157-172 K下脱附。在200 K时，虽然分子乙酸和乙酸盐的混合物保留在Pt（111）上，但乙酸几乎完全分解成乙酸盐，而且在Ni（110）上产生了一些CO。由于乙酸在200 K时几乎完全分解，只有一小部分化学吸附的乙酸在220 K时脱附。与Ni（110）上不同，大部分化学吸附的乙酸在218 K的类似温度下从Pt（111）上以分子形式解吸。乙酸的解吸在Pt（111）的345 K处有一宽峰，在Ni（110）的220-300 K处有一尾峰。在450 K时，乙酸在两种金属上几乎完全分解。与其中Ni与Pt具有相同或甚至更高的反应性的乙酸表面反应相比，在473和573 K下，在气相乙酸加氢脱氧中，1.5 wt % Ni/SiO2催化剂的活性低于5 wt % Pt/SiO2催化剂。焙烧催化剂的氢温程序化还原测量表明，Ni的还原需要比Pt的564 K更高的温度622 K。因此，Ni在加氢脱氧反应中较低的催化活性可归因于Ni较低的还原性，而不是乙酸吸附或表面反应的差异。(c)2023爱思唯尔公司All rights reserved.
Acetic acid adsorption and surface reactions were studied on Pt(111) and Ni(110) with infrared reflec-tion-absorption spectroscopy (IRAS) and temperature programmed desorption as well as computation-ally on the same well-defined single-crystal surfaces with density functional theory calculations. Additional calculations were performed for Ni(111) for comparison with Pt(111). At high acetic acid exposures at the dosing temperature of 90 K, acetic acid forms a chemisorbed layer covered by a physi-sorbed multilayer. The chemisorbed layer at 90 K for both Pt and Ni contains a mixture of molecularly adsorbed acetic acid as well as acetate. The physisorbed multilayer desorbs at 157-172 K. At 200 K, while a mixture of molecular acetic acid and acetate remains on Pt(111), acetic acid almost completely decom-poses into acetate and, furthermore, produces some CO on Ni(110). Due to the almost complete decom-position of acetic acid on Ni at 200 K, only a small fraction of the chemisorbed acetic acid desorbs molecularly at 220 K. Unlike on Ni(110), most of the chemisorbed acetic acid desorbs molecularly from Pt(111) at a similar temperature of 218 K. Recombinative desorption of acetic acid is observed as a broad peak at 345 K for Pt(111) and as a tail peak at 220-300 K for Ni(110). At 450 K, the decomposition of acetic acid is almost complete on both metals. In contrast with acetic acid surface reactions where Ni is equally or even more reactive than Pt, a 1.5 wt % Ni/SiO2 catalyst is less active than a 5 wt % Pt/SiO2 catalyst in vapor-phase acetic acid hydrodeoxygenation at 473 and 573 K. Hydrogen temperature pro-grammed reduction measurements for calcined catalysts show that Ni requires a higher temperature of 622 K for its reduction than 564 K for Pt. Therefore, the lower catalytic activity of Ni in hydrodeoxy-genation can be attributed to the lower reducibility of Ni and not the differences in acetic acid adsorption or surface reactions.(c) 2023 Elsevier Inc. All rights reserved.