Ligand effect of gold colloid in the preparation of Au/Nb2O5 for CO oxidation
Ligand effect of gold colloid in the preparation of Au/Nb2O5 for CO oxidation
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DOI：
10.1016/j.jcat.2020.05.014
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发表时间：
2020-09-01
影响因子：
7.3
通讯作者：
Murayama, Toru
中科院分区：
文献类型：
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作者：
Lin, Mingyue;Mochizuki, Chihiro;Murayama, Toru
采用配体保护金胶体前驱体Au-n(SC12H25)(m)的溶胶固定化方法，在典型固体酸Nb2O5上沉积金。研究了硫酸盐配体对Au/Nb2O5制备及CO氧化活性的影响。虽然在300℃的焙烧过程中，大部分硫酸盐配体被去除，但仍有少量硫元素残留在催化剂上，这对阻止金纳米颗粒聚集起了重要作用，其平均直径约为2.8 nm，金的负载量在0.9 wt%至4.2 wt%之间。在较低的温度（250℃）下煅烧比在300℃下煅烧产生更多的硫种，降低了CO氧化的催化活性。50% CO转化（T-50%）的温度为3℃，为0.9 wt% Au/Nb2O5，在20,000 mL h(-1) g(cat)（-1）下，在空气中使用1 vol% CO。随着金负载量的增加，催化活性逐渐提高。4.2 wt% Au/Nb2O5的T-50%为-41℃，基于周长金原子数的转换频率（TOF）在20℃时为8.7 s(-1)，而不含硫酸盐配体的沉积还原法制备Au/Nb2O5的TOF值为5.0 s（-1）。结果表明，催化剂上残留的硫对CO氧化没有抑制作用。(C) 2020爱思唯尔公司版权所有。
Sol immobilization method by using a ligand protected gold colloid precursor, Au-n(SC12H25)(m), was applied for the deposition of gold on Nb2O5 which is a typical solid acid. The effects of the thiolate ligand on the preparation of Au/Nb2O5 and on the catalytic activity for CO oxidation were investigated. Although most of the thiolate ligands were removed during the calcination at 300 degrees C, a small amount of sulfur species still remained on the catalyst, which played an important role for preventing the aggregation of the gold nanoparticles to give ca. 2.8 nm in a mean diameter with the gold loading amounts in the range from 0.9 wt% to 4.2 wt%. Calcination at a lower temperature (250 degrees C) gave a larger amount of the sulfur species than did the calcination at 300 degrees C, lowering catalytic activity for CO oxidation. The temperature for 50% CO conversion (T-50%) was 3 degrees C for 0.9 wt% Au/Nb2O5 under 20,000 mL h(-1) g(cat)(-1), using 1 vol% CO in air. With an increase in the loading amount of gold, the catalytic activity became higher. The T-50% of 4.2 wt% Au/Nb2O5 was -41 degrees C and turnover frequency (TOF) based on a number of the perimeter gold atom was calculated to be 8.7 s(-1) at 20 degrees C. The TOF value obtained by Au/Nb2O5 prepared by deposition-reduction without thiolate ligands was 5.0 s(-1). This result suggests that the sulfur remained on the catalyst did not inhibit CO oxidation. (C) 2020 Elsevier Inc. All rights reserved.