Tungstate-promoted zirconia

Tungstate-promoted zirconia (W0 /Zr02) has been established as an efficient and eco-friendly solid acid catalyst for the S5mthesis of 2-arylbenzimidazoles [50]. Both benzimidazoles and quinoxalines have been prepared using nanosulfated zirconia, nanostructured ZnO, nano-y-alumina, and nano-ZSM-5 zeolites, as the catalyst [51] (Scheme 30). Ethanol was found to be the most effective solvent in this case. 

R.V. Shingalapm, K.M. Hosamani, An efficient and eco-friendly tungstate promoted zirconia (WO,./ZrQ2) solid acid catalyst for the synthesis of 2-aryl benzimidazoles, Catal. Lett 137 (2010) 63-68. 

In addition to this, solid acid catalysts can also be used in the hydroisomerization cracking of heavy paraffins, or as co-catalysts in Fischer-Tropsch processes. In the first case, it could also be possible to transform inexpensive refinery cuts with a low octane number (heavy paraffins, n-Cg 20) to fuel-grade gasoline (C4-C7) using bifunctional metal/acid catalysts. In the last case, by combining zeolites with platinum-promoted tungstate modified zirconia, hybrid catalysts provide a promising way to obtain clean synthetic liquid fuels from coal or natural gas. 

Keywords alkanes-isomerization iron-promoter n-pentane-isomerization platinum-promoter selectivity tungsten oxide zirconia-tungstated-acidity zirconia-tungstated-redox properties... 

Furuta et al. tested a series of strong solid acids (alumina promoted sulfated zirconia, alumina promoted tungstated zirconia and sulfated tin oxide) for the transesterification of soybean oil with methanol at 200-300°C. Reaction yields over 90% were obtained for the alumina promoted tungstated zirconia at reaction times of 20 h using a flow reactor T = 250°C). The activity of the same catalyst was maintained for up to 100 h. 

Addition of FeS04 to Pt-promoted tungstated zirconia catalysts results in increased activity and selectivity (>98% selectivity at 50-70% conversion at... 

Abstract. Tungstated zirconia catalysts are stable and highly selective catalytic materials for the isomerization of alkanes when promoted by platinum and a transition metal oxide and when dihydrogen is present in the feed. Physical properties and the catalytic performance of these solids for the isomerization of n-pentane are discussed. 

Table 2. Comparison of the catalytic performance of Pt-promoted tungstated zirconia and...

S. Ruba, B. C. Gates, P. Vijayanand, R. R. Grasselli, and H. Rnozinger, An active and selective alkane isomerization catalyst iron - and platinum - promoted tungstated zirconia, J. Chem. Soc. Chem. Commun. 321-322 (2001). 

S. Kuba, M. Che, R. K. Grasselli, and H. Knozinger, Evidence for the Formation of W5+ Centers and OH Groups upon Hydrogen Reduction on Platinum - Promoted Tungstated Zirconia Catalysts, J. Phys. Chem. B 107, 3459-3463 (2003). 

X. Carrier, P. Lukinskas, S. Kuba, L. Stievano, F. E. Wagner, M. Che, and H. Knozinger, The State of the Iron Promoter in Tungstated Zirconia Catalysts, Chem. Phys. Chem. 5, 1191-1199 (2004). 

Kuba, S., Gates, B.C., Grasselli, R.K., and KnSzinger, H. An active and selective alkane isomerization catalyst Iron- and platinum-promoted tungstated zirconia. 

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