Simple and large-scale synthesis of β-phase molybdenum carbides as highly stable catalysts for dry reforming of methane

Abstract

The catalytic stability of monometallic β-Mo2C/CNTs was found to be superior to that of bimetallic Ni/β-Mo2C under similar reaction conditions.

Renewable Cyclopentanol From Catalytic Hydrogenation-Rearrangement of Biomass Furfural Over Ruthenium-Molybdenum Bimetallic Catalysts

“…For comparison, an XRD pattern of a high metal loading catalyst (5%Ru-20%Mo/CNT) is shown in the inset of Figure 5B, which suggested that the catalyst reduced at 500 • C displayed an amorphous character, diffraction peaks at 26.0, 36.9 and 53.4 • appeared at a reduction temperature of 600 • C, which are attributed to MoO 2 (JCPDS 78-1070), and molybdenum carbide crystal phases (α-MoC (JCPDS 65-0280, 2θ =36.4, 42.4, and 61.6 • ) and β-Mo 2 C 2θ =34.4,38.0,39.4,52.1,61.5,and 69.6 • ) were detected on the support at the temperature above 700 • C (Liang et al, 2017;Posada-Pérez et al, 2017;Wang et al, 2017). These results indicated the transformation of Mo species from molybdenum oxide to molybdenum carbide during the reduction and carburization process (Iida et al, 2017;Liang et al, 2017;Posada-Pérez et al, 2017;Gao et al, 2018;Kou et al, 2018). XPS was carried out to identify the surface chemical state of the 1%Ru−2.5%Mo/CNT catalyst reduced at 600 • C. As shown in Figure 5C, it was deconvoluted into three doublets: at 228, 230, and 232 eV, which can be attributed to different Mo species of MoC, MoO 2, and MoO x , respectively (Chen et al, 2015;Zhang et al, 2017).…”

Metal (Mo, W, Ti) Carbide Catalysts: Synthesis and Application as Alternative Catalysts for Dry Reforming of Hydrocarbons—A Review

“…A carbon source may also be in solid form, and it acts as a reducing agent and support. Biochar [77], biomass [24], resins [78], and carbon nanotubes [79] have been investigated. Liang et al [78] investigated the effect of the preparation procedure on the formation of α-Mo 1-x C and β-Mo 2 C, and the solid mixture of α-Mo 1-x C and β-Mo 2 C. Molybdenum carbide was prepared by ion exchange, impregnation, and mechanical mixing of molybdate salt with a strong alkali anion exchange resin and heated under a hydrogen or argon atmosphere in a temperature range of 350 to 900 • C. They found that annealing under H 2 promotes the formation of the beta phase.…”

“…The physicochemical properties and resulting catalytic activity of molybdenum carbide catalysts are influenced by the molybdenum-to-carbon ratio. Gao et al [79] reported a series of molybdenum carbide catalysts that differ in the weight content of Mo in order to use carbon nanotubes as a carbon source (Mo 0, 5, 10, 15, 30, 60, and 100 wt.%). Along with an increasing proportion of molybdenum in the catalyst, a decrease in the specific surface area, diameter, and pore volume was observed.…”

“…However, in the case of molybdenum carbide supported nickel catalysts, the ratio of Ni/Mo to the size of nickel particles plays a predominant role [51,226]. The nickel-to-molybdenum ratio affects the morphology and catalytic activity of Mo 2 C. Moreover, too high a dissociation of CH 4 promotes the formation of coke on the surface of the catalysts [79,222]. Zhang et al [222] observed that with an increasing nickel content in nickel-modified Mo 2 C supported on carbon nanotubes, the crystallite size of Mo 2 C for Ni/Mo ratios = 0.5, 1, 1.5, and 2 was equal to 53, 38, 35, and 28 nm, respectively.…”

Molybdenum and tungsten carbides can shine too

“…The use of Mo and W carbides in the decarboxylation and hydrodeoxygenation of vegetable oils is another example. 67 Both the hydrogenation of pyrolysis oil 68 and reforming of methane [69][70][71][72][73] with Mo 2 C and W 2 C have been demonstrated. To evaluate the true potential of Mo and W carbides, the effect of the S and N content in these feed sources needs to be taken into account.…”