| Research Abstract |
The selective formation of 1,2,4,5-tetramethylbenzene(TeMB) via disproportination of 1,2,4-tramethebenzene(TrMB)was investigated using pillared clays as caralysts. Pillared montmorillionita was more selective to yield 1,2,4,5-%te%m%b than pillared saponite. The higher selectivity of pillared montmotillonite was attriduted to a well-ordered face to face lamellar structure, while the lower selectivity of pillared saponite was resulted from a delaminated of card-house structure.
The selectivity of 1,2,4,5-TeMB formation decreased with increasing conversion level of 1,2,4-TrMB, due ot isometization of 1,2,4,5-TeMB. However,the isomerization was remarkably suppressed when pillared montmotillonite was calcined at 500゜C or higher temperatures, and consequently a high 1,2,4,5-TeMBselectivity was attained at high levels of converstion. These results were explained by reduction of the Bronsted acidity caused by calcination.
The catalytic activity of pillared montmorillonite remakably decreased with time on stream, while pillared saponite was stable against deactivation. However, the catalyst deactivation of pillared montmorillonite was thoroughly suppressed by spilt-over hydrogen. It was founs that spilt-over hydrogen effectively prevented catalyst deactivation if the acidity was mainly lewis type regardlessly of the type of catalysts. These tesults indicatre that lewis acidity plays a very importnat role in the stabilization of catalytic activity by spilt-over hydrogen.
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