Ultralow Rh Bimetallic Catalysts with High Catalytic Activity for the Hydrogenation of N-Ethylcarbazole

Abstract

Liquid organic hydrogen carrier (LOHC) has attracted a great deal of attention in recent years for its use in hydrogen storage. Supported Rh catalyst has been widely used in the hydrogenation reaction of the N-ethylcarbazole (NEC), one of the most promising LOHCs. However, the high Rh content is challenging because of its high cost. Herein, we successfully developed a γ-Al 2 O 3 -supported Rh-Ni bimetallic catalyst with only 0.1 wt % Rh, which showed excellent catalytic performance in the hydrogenation of NEC with a high conversion of 99% and high selectivity of 98% in 2 h. Various characterizations such as highangle annual dark-field scanning transmission electron microscopy images with phase mappings, X-ray photoelectron spectroscopy, H 2 temperature-programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy confirmed that the excellent catalytic performance was ascribed to the following factors: (i) electron transfer between the bimetallic Rh-Ni nanoparticles (NPs) structure on the catalyst support; (ii) formation of smaller Ni NPs on the bimetallic Rh-Ni catalyst, which was promoted by Rh; (iii) increased reducibility of the loaded NiO during the catalyst preparation process as a result of the highly dispersed single Rh atom. Thus, the prepared catalyst with ultralow Rh content in this work still has outstanding catalytic activity and sheds light on a fruitful strategy for developing low-cost hydrogenation catalysts of NEC for hydrogen storage.

Recent Advances in Hydrogenation Reactions Using Bimetallic Nanocatalysts: A Review

“…This, along with the presence of greater active sites, led to the greater catalytic activity of the catalyst. The enhanced catalytic activity of the bimetallic catalyst as compared to a physical mixture of Rh and Ni catalysts was attributed to the hydrogen spillover between Rh and Ni particles [140] . Table 2 gives a summary of different bimetallic catalysts used in the hydrogenation of unsaturated hydrocarbons.…”

Ultrasound-assisted green synthesis of Ru supported on LDH-CNT composites as an efficient catalyst for N-ethylcarbazole hydrogenation

“…However, the emerging liquid organic hydrogen carrier (LOHC) has the advantages of low cost, large hydrogen storage capacity, and compatibility with existing infrastructure equipment. It is considered as a green, safe, controllable hydrogen storage technology with great social and economic benefits [6] . The LOHC system is composed of a pair of hydrogen-poor and hydrogen-rich organic compounds, which can store and release hydrogen through reversible hydrogenation and dehydrogenation between them [7] , [8] .…”

“…Ru-, Pt-, Rh- and Ni-based catalysts have been widely studied in the hydrogenation of NEC [6] , [9] , [10] , [11] , [12] , among which Ru metal has the appropriate d-band center value and shows the highest catalytic activity [13] . In addition, Ru-based catalysts can also be used in a variety of different hydrogenation reactions [14] and exhibit excellent hydrogenation performance, such as the hydrogenation of nitroarenes to produce aniline [15] , the carbonyl compound reduction amination to produce primary amines [16] , etc.…”

Alloying effect of Ni-Mo catalyst in hydrogenation of N-ethylcarbazole for hydrogen storage

“…The same doping method was used in the research of Yu et al (2020) , and they also focused on the hydrogenation activity caused by the crystal form of TiO 2 . In contrast, Liu et al (2021) prepared high-performance Rh-Ni/γ-Al 2 O 3 catalysts by doping very small amounts of Rh in Ni. Ding et al (2021) prepared Ni 70 /AlSiO-1/1 catalysts by using a new carrier AlSiO-1, which could weaken the metal-carrier interaction and reduce the formation of NiAl 2 O 4 species to facilitate the reduction of Ni.…”