Silicophosphoric acid, catalyst

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. S. Isomerization of 2-methylenebicyclo[2.2.2]octane (18) at 196-250°, vapor phase, in the presence of silicophosphoric acid catalyst. 

When passed over the silicophosphoric acid catalyst at 250 , this mixture is readily converted to 24, 25, and 26, as expected. Apparently,... 

The remarkably consistent pattern outlined in the reactions of the CgHi2 and C9H14 series should also appear in the CioHie series, and in particular, for bicyclic terpenes. Camphene (37) (Fig. 12), closely related to isosantene (27), was reacted at 250° in the vapor phase in the presence of silicophosphoric acid catalyst (18). A rather complicated monomer fraction (30 chromatographic peaks), steam-distilled from... 

Fig. 13. Composition of isomer mixture (mole %) versus contact time (wt catalyst/wt of hydrocarbon injected per hour) in the reaction of camphene at 250°, vapor phase, in the presence of silicophosphoric acid catalyst. I, Camphene 2, dimethylbicyclo-[3.2.1]-3-octene 3, a-terpinene 4, p-cymene 5, dimethylbicyclo[3.3.0]-2-octene 6, dimethylethylbenzenes 7, tetramethylbenzenes 8, methylhexahydroindenes 9, methylindan.

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

The hydration of oleflns is important for the direct synthesis of alcohols from olefins in the pietroleum industry and has been extensively studied over various solid acid catalysts. In the case of ethanol synthesis from ethylene and water, silicotungstic acids, silicophosphoric acids, solid phosphoric acids, metal sulfates, " and metal oxides have been studied as solid acid catalysts. In its industrial process, a solid phosphoric acid catalyst (Shell patent) is widely used throughout the world. The nature of the active (acidic) sites which exhibit high catalytic activity and selectivity is discussed below together with the hydration mechanism involving the catalytic behavior. 

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