RETAINED PRODUCT FROM REACTION OF 1-HEXENE ON SAPO-34 - FORMATION OF ADAMANTANES

Treatment of the microporous silico-alumino-phosphate SAPO-34 (similar in structure to chabazite) with 1-hexene at 513 K generates retained reaction product in which adamantanes (adamantane, 1-methyl, dimethyl, ethyl derivatives) are major constituents, together with cyclopentadienes, alkanes, and some alkylbenzenes. No adamantanes could be detected in the evolved gaseous products. Adamantanes are maximized at intermediate treatment times (4-28 h), while products related to naphthalene and anthracene/phenanthrene become important at very long times or higher temperatures. Evidence suggests that adamantanes are formed by acid-catalyzed reactions passing from cyclopentadienes (CPDs) via CPDs-dimer and tetrahydro-CPDs-dimer, while products in the naphthalene and anthracene/phenanthrene systems are produced by alternative acid-catalyzed pathways from CPDs and CPDs-dimer. Evidence shows that adamantanes are formed within the SAPO-34 cages, which appear to be uniquely active for this reaction for reasons possibly related to size/shape coincidence between host cage and transition state guest (analogous, it is suggested, to enzyme-substrate (transition state) complementarity in enzyme chemiStry). © 1990.