Highly stable Ni–Al 2 O 3 catalyst prepared from a Ni–Al layered double hydroxide for ethanol decomposition toward hydrogen
Highly stable Ni–Al 2 O 3 catalyst prepared from a Ni–Al layered double hydroxide for ethanol decomposition toward hydrogen
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DOI：
10.1016/j.apcata.2015.10.007
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发表时间：
2015-11
影响因子：
5.5
通讯作者：
K. Manukyan;A. Cross;A. Yeghishyan;S. Rouvimov;Jeffrey J. Miller;A. Mukasyan;E. Wolf
中科院分区：
文献类型：
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作者：
K. Manukyan;A. Cross;A. Yeghishyan;S. Rouvimov;Jeffrey J. Miller;A. Mukasyan;E. Wolf
本文报道了以Ni-Al层状双氢氧化物（LDH，Ni 6Al 2（OH）16（CO 3）0.75（OH）0.25·4 H2O）为前驱体，经还原制得的Ni-Al 2 O3催化剂的制备、表征、活性和稳定性。原位X-射线吸收光谱表明，从LDH前体中还原Ni以形成高负载量80%的Ni-Al_2 O_3催化剂（Ni-Al_2 O_3-LDH）比还原10%浸渍的Ni-Al_2 O_3氧化铝（Ni-Al_2 O_3-I）催化剂更快。还原后的Ni-Al_2 O_3-LDH催化剂表现出高度分散的Ni纳米颗粒（3-5 nm）分布在顶部，部分嵌入纳米颗粒，以及一些包裹在Al_2 O_3基质中。浸渍在氧化铝上的纳米颗粒（Ni-Al 2 O3-I）较大（0.7 -15 nm），出现在氧化铝载体的顶部。在250 °C下在Ni-Al 2 O3-LDH上乙醇分解期间的转化率与运行时间（TOS）的结果在100小时TOS期间仅表现出轻微的失活，而Ni-Al 2 O3-I催化剂在2小时TOS之后表现出快速失活而没有转化率。X射线光电子能谱表明，Ni-Al_2 O_3-LDH催化剂在100 h的停留时间后，碳含量增加了48%，TEM显示，在100 h TOS后，在氧化铝基质上的Ni上和部分嵌入Ni-Al_2 O_3-I上的Ni纳米颗粒上形成了无定形碳或碳纳米管的薄层。LDH催化剂。在TOS期间，Ni-Al 2 O3-LDH催化剂的总表面积增加，这可能是从包裹的Ni纳米颗粒中补充了新鲜的表面Ni，从而维持了高活性。
The preparation, characterization, activity, and stability of a Ni–Al2O3catalyst derived from reduction of a Ni–Al layered double hydroxide precursor (LDH, Ni6Al2(OH)16(CO3)0.75(OH)0.25·4H2O) are reported in this paper. In-situ X-ray adsorption spectroscopy shows that reduction of Ni from the LDH precursor to form a highly loaded 80% Ni–Al2O3catalyst (Ni–Al2O3–LDH) is faster than reduction of a 10% impregnated Ni–Al2O3alumina (Ni–Al2O3–I) catalyst. The reduced Ni–Al2O3–LDH catalyst exhibits highly dispersed Ni nanoparticles (3–5 nm) distributed on top, partially embedded nanoparticles, and some encapsulated in the Al2O3matrix. The nanoparticles impregnated on alumina (Ni–Al2O3–I) are larger (∼7–15 nm) and appear on top of the alumina support. Conversion vs time on stream (TOS) results during ethanol decomposition at 250 °C on Ni–Al2O3–LDH exhibits only a slight deactivation during 100 h TOS, while the Ni–Al2O3–I catalyst shows rapid deactivation with no conversion after 2 h TOS. X-ray photoelectron spectroscopy shows that the carbon content increases up to 48% after 100 h TOS on the Ni–Al2O3–LDH catalyst, while a similar increase occurs after 2 h TOS on the Ni–Al2O3–I catalyst.TEM shows that after 100 h TOS either a thin layer of amorphous carbon or carbon nanotubes forms on Ni on top of the alumina matrix and on partially embedded Ni nanoparticles on the Ni–Al2O3–LDH catalyst. Total surface area of the Ni–Al2O3–LDH catalyst increased during TOS, which may be suplying fresh surface Ni from the encapsulated Ni nanoparticles that sustain the high activity.