Hydrocarbons catalysts, silicophosphoric acid

CgHi2 bicycloolefin isomerizations are summarized in Fig. 2. At 260°, over a silicophosphoric acid catalyst, bicyclo[2.2.2]-2-octene (4) is converted to the bicyclo[3.3.0]-2-octene (6), with intermediate formation of bicyclo[3.2.1]-2-octene (5). The yield of hydrocarbon 5 passes through a maximum and then vanishes when the conversion of 4 increases 8-10, 18a). This isomerization also slowly forms a mixture... 

Knotnerus and Schilling (22) have recently reinvestigated these reactions at 260-280° in the presence of the silicophosphoric and silica-alumina acid catalysts. Typical yields in the isomerization of 9 (silicophosphoric acid catalyst, HLSV = 0.25 hr-i) are shown in the tabulation. These figures are based on the hydrocarbon injected (40%... 

Finally, the cycloisomerization of 4-vinylcyclohexene (a butadiene dimer) to bicyclo[3.3.0]-2-octene (6) was found to occur at 250° over a silicophosphoric acid catalyst (11), along with a very large amount of hydrogen transfer (ethylcyclohexenes, methylethylcyclopentenes, ethylbenzene) and polymerization, a reaction closely related to that of limonene (5). A much better yield of the same hydrocarbon (6) was obtained from 1,5-cyclooctadiene (72% at 200°) with the same catalyst (25). 

Fio, 6. Composition of isomer mixture (mole %) versus contact time (wt catalyst/wt of hydrocarbon injected per hour) in the reaction of 2-methylenebicyclo[2.2.2]octane (18) at 195°, vapor phase, in the presence of silicophosphoric acid catalyst. 

His first major discovery in the U.S. was the development of silicophosphoric acid (solid phosphoric acid) as a catalyst for hydrocarbon conversion. 

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