Tungsten carbide catalyst

Carbothermal synthesis of nano-sized tungsten carbide catalyst... 

Leclercq, L., Almazouari, A., Dufour, M., and Leclercq, G. 1996. Carbide-oxide interactions in bulk and supported tungsten carbide catalysts for alcohol synthesis. In Chemistry of transition metal carbides and nitrides, ed. S. T. Oyama, 345-61. Glasgow Blackie. 

Ji et al. have shown that nickel-promoted tungsten carbide catalysts can also directly convert cellulose to ethylene glycol in a one step process [52, 53]. These Ni-W2C/AC catalysts exhibited a remarkable higher selectivity for ethylene glycol than Pt/Al203 and Ru/C. Indeed, after 30 min of reaction at 518 K under 60 bar of H2, cellulose was completely converted into water-soluble polyols over a 2% Ni-30% W2C/AC-973 catalyst (61% yield in ethylene glycol). 

The role of complexes and modifiers in the reduction has been discussed in [20-24]. The investigation of the liquid phase catalytic hydrogenation of N03 , N02, and NH2OH at tungsten carbide catalyst furnished interesting information concerning the electrocatalytic properties of the latter [25]. 

The intrinsic nature of tungsten carbide catalyst in CO-H2 reactions is to form hydrocarbons. This property can be modified by oxidic promoters as for the case of noble metals like Pt or Rh or by the presence of carbon vacancies at the surface. To increase the production of alcohols in the Fischer-Tropsch reaction, the catalyst should be bifunctional, with oxidic and carbidic components as in the case of WC on Ti02. Overcarburization of WC on supports like Si02 or Zr02 where the W-O-metal interaction is weak leads to C/W ratios close to unity and does not result in alcohol formation. 

Figure 22.1 XRD pattern of the tungsten carbide catalyst after calcination at 750 K.

Dimethylsulfide was added to the n-heptane to give 1000 ppm S in the gas phase. Figure 22.3 shows the effect of sulfur on conversion. The platinum catalyst lost its activity in about 3 h, whereas the tungsten carbide catalyst was very slightly affected during the experiment. Sulfur tolerance is important in petroleum refineries, since it may allow the substitution of the costly noble metals with carbides in streams containing sulfur. 

Yang, X.G. and Wang, C.Y., Nano structured tungsten carbide catalysts for polymer electrolyte fuel cells, Appl. Phys. Lett., 86, 224104, 2005. 

Tungsten Carbide Catalysts in Fischer—Tropsch Synthesis [10.16]... 

The properties of tungsten carbide catalysts depend strongly on their surface chemistry, which can be clearly demonstrated when using them in FT synthesis. 

Fig.8 and Fig.9. Diagrams of catalyst conversion efficiency in CO, NO and propane removal plotted against temperature (R=1) (Fig.8) or against equivalence ratio at 465°C (Fig.9) on the tungsten carbide catalyst (WC/A1,0, K ).

JI 08] Ji N., Zhang T., Zheng M., et al, Direct Catalytic Conversion of Cellulose into Ethylene Glycol Using Nickel-Promoted Tungsten Carbide Catalysts , Angewandte Chemie International, vol. 47, no. 44, p. 8510,2008. 

Increasing selectivity towards EG production could render a more direct process towards bio-based EG. A direct route to produce EG from cellulose has, for example, been described by Ji et al, who reported the direct conversion of cellulose into EG with high yields (up to 60%) using nickel-promoted tungsten carbide catalysts [123]. 

Chhina H, Campbell S, Kesler O (2007) Thermal and electrochemical stability of tungsten carbide catalyst supports. J Power Sources 164(2) 431-440... 

A further rapid bimolecular reaction of HOSCN then probably takes place, although further oxidation of this intermediate by I2 cannot be eliminated. In the reaction of iodine monochloride with alcohols, the slow step is the attack of I+ on the alcohol to yield ROI. There is no evidence for any chlorinated product. An n,m.r. study of the exchange between Cl and Cl a in aqueous solution has been reported and comparisons have been made with other halogen exchange processes. The reduction of perchlorate to chloride by molecular hydrogen in the presence of tungsten carbide catalysts has also been described. ... 

Okamoto H, Kawamura G, Ishikawa A, Kudo T. Characterization of oxygen in tungsten carbide catalysts and its role in electrocatalytic activity for methanol oxidation. J Electrochem Soc 1987 134 1645-9. 

Chhina, H. et al. 2007b. Thermal and electrochemical stabihty of tungsten carbide catalyst supports. Journal of Power Sources 164 431-440. 

Huang, Y.-B., Chen, M.-Y., Yan, L., Guo, Q.X., Fu, Y., 2014. Nickel—Tungsten carbide catalysts for the production of 2,5-dimethylfuran from biomass-derived molecules. 

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