STUDIES ON WO3 ZRO2 AND MOO3/ZRO2 SOLID S UPERACID SYSTEMS/

The dispersion and crystal phase changes of tungsten end molybdenum co mpounds on samples prepared by impregnating ammonium metatungstate and ammonium paramolybdate on amorphous ZrO2 during the calcination have been investigated in detail. It was found that after the calcination a t 350 degrees C tungsten and molybdenum existed in the form of isopoly acidic anions so that the apparent dispersion thresholds determined by XRD method were much greater than the calculated monolayer dispersion capacities of WO3 and MoO3 on ZrO2. After calcination at 800 degrees C the W and Mo dispersed on ZrO2 transformed into the form of WO3 on Z rMo2O8, and the experimental apparent dispersion thresholds became app roximate to the monolayer dispersion capacities of WO3 and ZrMo2O8 on ZrO2. The results of measurements by Hammett indicator and n-pentane i somerization methods showed that H-o of the WO3/ZrO2 systems reached - 13-8-14.5 and that of the MoO3/ZrO2 systems -12.0-12.7, and the sample s containing the amounts of WO3 and MoO3 close to their monolayer disp ersion capacities and calcined at 800 degrees C displayed stronger sup eracidity.