Synthesis of solid superacids and their activities for reactions of alkanes

Highly Active Mesoporous Nb–W Oxide Solid‐Acid Catalyst

“…The very high catalytic performance of mesoporous Nb 3 W 7 oxide was attributed to a high surface area mesoporous structure, strong acid sites which are comparable in strength to those of strongly acidic zeolites (HZSM-5 and HMOR), and the formation of strong Brønsted acid sites by the isomorphous replacement of Nb 5+ ions by higher-valence W 6+ ions in tungsten-enriched samples, as observed in WO 3 /ZrO 2 (H 0 = À14.6). [22] In that case it is reported that replacement of ZrO 2 by WO 3 forms strong acid sites similar to that of SO 4 /ZrO 2 (H 0 = À16.1). [22] The highest activity of WO 3 /ZrO 2 was obtained at surface tungsten densities, which maximize the quantity of amorphous surface polytungstate species relative to the isolated surface WO x and crystallized WO 3 .…”

“…[22] In that case it is reported that replacement of ZrO 2 by WO 3 forms strong acid sites similar to that of SO 4 /ZrO 2 (H 0 = À16.1). [22] The highest activity of WO 3 /ZrO 2 was obtained at surface tungsten densities, which maximize the quantity of amorphous surface polytungstate species relative to the isolated surface WO x and crystallized WO 3 . [23] Similar to WO 3 /ZrO 2 , strong acid sites in the mesoporous Nb 3 W 7 oxide could have formed leading to the high surface tungsten densities in the niobium matrix with no crystallized WO 3 .…”

Effects of calcination temperature and water-washing treatment on n-hexane hydroisomerization behavior of Pt-promoted sulfated zirconia based catalysts

“…It is generally believed that the high isomerization activity of SZ and PSZ could be obtained only when amorphous zirconium hydroxide acted as the precursor of sulfation. In the preparing process of SZ and PSZ, the high calcination temperature was considered to be indispensable [7] and it strongly affected the catalytic activity of SZ and PSZ to a great extent [8][9][10][11][12][13]. The results from Arata et al [12] and Sun et al [13] indicated that the calcination temperature effect on the isomerization activity of SZ depended on the preparation method to some extent.…”

“…In the preparing process of SZ and PSZ, the high calcination temperature was considered to be indispensable [7] and it strongly affected the catalytic activity of SZ and PSZ to a great extent [8][9][10][11][12][13]. The results from Arata et al [12] and Sun et al [13] indicated that the calcination temperature effect on the isomerization activity of SZ depended on the preparation method to some extent. Comelli et al [8] examined the effect of calcination temperature on n-hexane isomerization catalytic performance of Pt-promoted SZ, and these authors considered that the isomerization activity reached maximum at the calcination temperature of 550-600 • C.…”

Styrene and styrene dimer derivatives, cyclohexene, tert-butylbenzene and cumene as test reactions for acid strength measurements of crystalline and amorphous silica-aluminas, sulfated oxides and Amberlyst

“…Then the authors conclude that it is more reliable to compare the acid strength of solids experimentally with that of acid solutions like H 2 SO 4 -H 2 O or HSO 3 H-SbF 5 rather than use the H O function values obtained from indicator adsorption experiments. For these reasons, the application of correlation of cumene dealkylation results [11] and energy of Ar desorption [12] with H O values based on indicator adsorption measurements should be used with care.…”