Organic Reactions Catalyzed by Sheet Silicates

Sheet silicates like montmorillonite have been utilized as catalysts for many organic reactions, which are carried out either in the vapor phase or in the liquid phase. The following are some typical reactions catalyzed by sheet silicates. For the complete list, readers should refer to recent reviews and references cited therein.  

Montmorillonite was used as the initial catalyst for the catalytic cracking of gas oil as early as 1930. Various efforts were made to modify the days in order to improve the yield of gasoline fractions and the life of the catalysts. The catalytic activity and the thermal stability of natural montmorillonite was improved by hot acid treatment. This treatment was considered to leach out almost half of the oct2thedral aluminum 

Dehydration from primary alcohols over Al(III)-exchanged montmorillonite at 473 K gives mainly di-(tJk-I-yl) ethers with little alkene production, whereas secondary and tertiary alcohols, other than propan-2-ol, undergo facile intramolecular dehydration exclusively to the corresponding alkenes.  

Diethyleneglycol is cyclised to yield 1,4-dioxane in addition to oligomerization.  

Primary amines and thiols undergo similar elimination with Al(III)-exchanged montmorillonites. Primary amines are converted at 473 K to di-alk-l-ylamine by loss of ammonia. Likewise, hydrogen sulfide is eliminated from thiols to form di-alk-l-yl thioethers.  

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