Ring opening of cis-decalin on bifunctional Ir/- and Pt/La-X zeolite catalysts

Zeolite La-X was loaded with iridium or platinum by ion exchange with cationic complexes of the noble metals, their thermal decomposition in air and reduction with hydrogen. The resulting bifunctional catalysts were used for the hydroconversion of cis-decalin in a high-pressure flow-type apparatus at temperatures between 200 and 255 °C and a hydrogen pressure of 5.2 MPa. Both Ir/La-X and Pt/La-X showed a high tendency for skeletal isomerization of decalin. An important isomer was formed by type A rearrangement, namely spiro[4.5]decane. For a safer peak assignment of the most desired products, the open-chain decanes, n-decane was catalytically isomerized, and the iso-decanes thereby generated were co-injected into the gas chromatograph with a liquid product from the hydroconversion of decalin. Open-chain decane yields of up to 12% were achieved. The molar carbon number distributions of the hydrocracked products were M-shaped indicating mainly C–C bond cleavage of the ring opening products with one remaining naphthenic ring via carbocations and the paring reaction.

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► We studied the isomerization and ring opening of decalin at pH2=5.2 MPapH2=5.2 MPa.
► The performance of Ir/La-X and Pt/La-X as catalysts was evaluated.
► Improved analyses enabled a safer quantitative analysis of open-chain decanes.
► Skeletal isomerization appears to follow the known rules of carbocation chemistry.
► The yields of open-chain decanes are higher than reported so far in the literature.