Tuning the Catalytic Performance of Cobalt Nanoparticles by Tungsten Doping for Efficient and Selective Hydrogenation of Quinolines under Mild Conditions

Abstract

Non-noble bimetallic CoW nanoparticles (NPs) partially embedded in a carbon matrix (CoW@C) have been prepared by a facile hydrothermal carbon-coating methodology followed by pyrolysis under an inert atmosphere. The bimetallic NPs, constituted by a multishell core–shell structure with a metallic Co core, a W-enriched shell involving Co 7 W 6 alloyed structures, and small WO 3 patches partially covering the surface of these NPs, have been established as excellent catalysts for the selective hydrogenation of quinolines to their corresponding 1,2,3,4-tetrahydroquinolines under mild conditions of pressure and temperature. It has been found that this bimetallic catalyst displays superior catalytic performance toward the formation of the target products than the monometallic Co@C, which can be attributed to the presence of the CoW alloyed structures.

Selective Conversion of HMF into 3‐Hydroxymethylcyclopentylamine through a One‐Pot Cascade Process in Aqueous Phase over Bimetallic NiCo Nanoparticles as Catalyst

“…The lattice spacing of monometallic Co@C and Ni@C catalysts is 0.20 nm (Figure 2b,f, respectively), which is attributed to the (111) plane of metallic cobalt and nickel species. Moreover, some Co 3 O 4 patches can also be found in the Co@C NPs, while NiO is observed in the Ni@C NPs, which should come from re‐oxidation of the surface of metallic NPs after preparation and exposure to air (see Figure 2b,f) [31,32] …”

“…Moreover, some Co 3 O 4 patches can also be found in the Co@C NPs, while NiO is observed in the Ni@C NPs, which should come from re-oxidation of the surface of metallic NPs after preparation and exposure to air (see Figure 2b,f). [31,32] On the other hand, HRTEM images of Ni 0.5 Co 0.5 @C sample (Figure 2d) show a lattice spacing of 0.21 nm, which corresponds to the interplanar space between (111) facet of NiÀ Co. [43] The interplanar space of 0.21 nm was also found in samples Ni 0.75 Co 0.25 @C and Ni 0.25 Co 0.75 @C (Figures S2), indicating that alloyed species are also formed on these samples.…”

“…In addition, the carbon coating promotes the in-situ reduction of oxide species on the surface of the metal nanoparticle under reaction conditions, while protecting the non-noble metal from agglomeration, overoxidation, and metal leaching. [12,[31][32][33] These catalysts showed excellent activity and selectivity for the chemoselective reduction of nitroarenes into anilines, reduction of levulinic acid into γ-valerolactone, [32,33] hydrogenation of quinolines, [31] as well as for the selective reduction of HMF to BHMF. [12] Considering the high stability and good performance of these nanoparticles in hydrogenation reactions, as well their simple and green preparation method, we thought to adapt the catalysts for the hydrogenative ring-rearrangement of HMF.…”

“…The carbon layers present cracks that allow diffusion of the reactants to the metal. In addition, the carbon coating promotes the in‐situ reduction of oxide species on the surface of the metal nanoparticle under reaction conditions, while protecting the non‐noble metal from agglomeration, overoxidation, and metal leaching [12,31–33] . These catalysts showed excellent activity and selectivity for the chemoselective reduction of nitroarenes into anilines, reduction of levulinic acid into γ‐valerolactone, [32,33] hydrogenation of quinolines, [31] as well as for the selective reduction of HMF to BHMF [12] …”

Exploring the Zn-regulated function in Co–Zn catalysts for efficient hydrogenation of ethyl levulinate to γ-valerolactone

“…It has been reported in the literature that H 2 dissociation occurs at the active sites on the catalyst surface. 47 Compared with the single metal catalyst, the total amount of H 2 desorbed by the Co 3 Zn 1 @NPC-600 catalyst is greatly increased, which proves that Co 3 Zn 1 @NPC-600 has a higher concentration of active H species than Co@NPC-600. And this result confirms that the addition of Zn can increase the H 2 adsorption and activation capacity of the catalyst, so Co 3 Zn 1 @NPC-600 exhibits better catalytic activity.…”