Causes of deactivation of chromium-containing Y type zeolites in hydration of olefins

Hydration of Olefins into Alcohols

“…Data on olefin hydration over different zeolites by Minachev with co-authors are being published since 1976 [22][23][24][25][26][27][28]. Investigation was carried out in a flow unit at 473-673 K and pressure up to 20 MPa.…”

“…This productivity is close to that for industrial phosphorus acid catalyst. The increase of temperature up to 538 K and pressure up to 15 MPa increases conversion up to the equilibrium one (25%, figure 1,2) Use of zeolites with high content of silica with 5% Cr 2 O 3 additives (does not included in CVK zeolite structure, SiO 2 /Al 2 O 3 = 70 -90) and dealuminated faujasite increases the activity [24] and stability of the catalysts [27]. Introduction of chromium reduces formation of coke and aromatic compounds that are usual for zeolites with high content of silica [23][24][25] (figure 3,4,5).…”

“…Existence of such direct correlation between H 0 and reaction rate was known earlier for hydration of olefins in H 2 SO 4 , or HPA solutions. In paper [27] it was shown with H 2 O sorption that zeolites with high silica content are hydrophobic strong acids in water not only because of high acidity, but because of high surface activity towards organic indicators as compared to that for water. Zeolites with high silica content (Si/Al > 9.2) possess strong acidic centers (-8.2 < H 0 < -5.6), and for zeolites with Si/Al < 3.5 and 3.7 < Si/Al < 6.9 possess weak acidic centers (H 0 > +1.5), and for mordenite H 0 > -3.…”

“…Fig.11. Correlation between hydration on activity per protonic site and aluminum content in the various zeolites[27].…”