Revealing the Hydrogenation Performance of RuMo Phosphide for Chemoselective Reduction of Functionalized Aromatic Hydrocarbons

Abstract

Bimetallic transition metal phosphide catalysts are promising materials for low-temperature, liquid-phase hydrogenation reactions. This work explores the chemoselective hydrogenation ability of RuMoP using various functionalized aromatic hydrocarbons to provide insight into how the functional groups compete for reduction on the surface of RuMoP. Using molecular hydrogen as the reductant, high selectivity (∼99%) to reduction of the substituent is achieved for the hydrogenation of electron withdrawing functionalities such as nitrobenzene, benzaldehyde, and benzophenone with RuMoP to yield aniline, benzyl alcohol, and diphenylmethanol, respectively. In contrast, aromatics with electron donating groups such as phenol, anisole, and toluene, show high ring hydrogenation selectivity (∼99%) to form cyclohexanol, methoxycyclohexane, and methyl cyclohexane, respectively, although the reaction proceeded slowly with RuMoP. Pyridine adsorption was studied via diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), which provided evidence of surface electron deficient sites (i.e., Lewis acids) that are responsible for targeting the electron-rich portion of the substrate. Additional DRIFTS experiments were performed using nitrobenzene, anisole, and a mixture of the two. From these experiments, features associated with −NO2 adsorption in nitrobenzene and ring adsorption in anisole were observed, which correlated well with the observed reaction results. Finally, a solvent study provided evidence for the competitive adsorption of isopropanol and the π-electrons from the aromatic ring of phenol with the former being more favorable on RuMoP surface.

Bimetallic Ru–Mo Phosphide Catalysts for the Hydrogenation of CO2 to Methanol

“…Computational and experimental evidence revealed that changing bulk composition can alter the surface charge and Lewis acid character, which influenced the C–O bond cleavage ability of the catalyst. Additionally, a similar synergy between heteroatoms in bimetallic phosphides was observed in Co–Ni and Fe–Ni bimetallic phosphides, where a different metal composition enhanced the HDS activity through modification of the active sites. − Recent studies have also shown that a Ru 1 Mo 1 P bimetallic catalyst results in a strong promotional effect for the selective hydrogenation of substituted aromatic hydrocarbons. , For furfural hydrogenation, the synergistic effect in Ru 1 Mo 1 P increases the adsorption energy of the carbonyl O on surface active sites and accelerates hydrogenation of furfural to furfural alcohol . Similarly, this interaction may be important for methanol synthesis, as CO 2 must adsorb on surface active sites and hydrogenate to form methanol. ,,,, Therefore, the adsorption strength of CO may improve activation of CO 2 , stabilize CO species, and facilitate the hydrogenation steps toward methanol. , …”

“…Unsupported monometallic (MoP, Mo 3 P, RuP, and Ru 2 P) and bimetallic phosphide catalysts (Ru x Mo 2– x P) were synthesized through a previously reported temperature-programmed reduction (TPR) method. , Monometallic phosphides were synthesized by dissolving the appropriate amount of citric acid (0.7 × mol of metal) in 50 mL of deionized water (18 MΩ·cm). The metal precursor (Mo, (NH 4 ) 6 Mo 7 O 24 ·4H 2 O; Ru, RuCl 3 · x H 2 O) was added into the solution followed by addition of (NH 4 ) 2 HPO 4 which served as the P source.…”

“…As a widely used modification strategy, incorporation of a second metal to form bimetallic phosphides has been investigated for many hydrogenation reactions, resulting in a wide range of phase-pure materials whose hydrogenation ability can be optimized by changing the catalyst composition. − ,− For example, Rensel et al synthesized Fe x Mo 2– x P and discovered that the C–O bond cleavage selectivity in phenol hydrodeoxygenation strongly depends on the Fe/Mo ratio. Computational and experimental evidence revealed that changing bulk composition can alter the surface charge and Lewis acid character, which influenced the C–O bond cleavage ability of the catalyst.…”

Ethane dehydrogenation performance and high temperature stability of silica supported cobalt phosphide nanoparticles

“…P-Containing catalysts, also known as metal phosphides, are known particularly for hydrodesulfurization, hydrodeoxygenation, and hydrogenation reactions. [8][9][10][11][12][13] Additionally, many metal phosphides are made from earth abundant metals, such as Ni, Co, Mo, and Fe, and have been identified as promising alternatives to noble metal based catalysts for many industrially relevant reactions. 14,15 For light alkane dehydrogenation reactions, P promotion of Ni results in improved selectivity to the desired alkene as well as improved stability over monometallic Ni nanoparticles.…”

P‐doped Carbon as the Efficient Support of Nickel Catalysts for Hydrodechlorination of Chlorodifluoromethane

“…), [7][8][9][10] supported transition metal (Ni, Mo, Fe, etc.) [11][12][13][14][15][16] and heteroatom doped carbon-based materials (eg., N, S, P or B), [17,18] which exhibited metal-like catalytic properties. Noble metal catalysts present good catalytic performance, but they experience poor stability due to severely deposition of carbonaceous species and high cost, which both limit the large-scale application of these catalysts.…”