Production of tetralin by the hydrogenation of naphthalene-containing fractions
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Naphthalene can be hydrogenated (mainly to tetralin) to the extent of 75–80% on hydrogenating it at a hydrogen pressure of 20 atm, a temperature of 350–370dgC, and a crude feed of 0.25–1.0 kg/liter · h, on using Al2O3 + CoO + MoO3 catalyst. The hydrogenation conversion level of 2-methylnaphthalene is 1.5 times less. Naphthalene can be hydrogenated to the extent of 90–95% at a pressure of 40 atm on using a tungsten— nickel—sulfide catalyst. A significant fraction of the tetralin formed is, however, hydrogenated further to the decalins.
Naphthalene can be converted to the extent of 75–80% into tetralin and decalin on hydrogenating naphthalene fractions containing 42–76% naphthalene at 350° C, under a pressure of 40 atm, and crude feed of 0.3 kg/liter · h. Decalin formation can be reduced by cutting down the hydrogen pressure to 20 atm. To obtain a hydrogenizate which is suitable as a crude for isolating tetralin by narrow cut fractionation, the naphthalene concentration of the crude should be greater than 60% and that of the tetralin in the hydrogenizate should not be less than 45–50%.
By using a column with an efficiency of 20 theoretical plates it is possible to recover 80% of the potential amount of tetralin, in terms of the naphthalene present in the crude, from the hydrogenizate obtained at a pressure of 40 atm and which contains about 75% of tetralin and decalin. Decalin in amounts of 10–12% is obtained at the same time. By fractionating a hydrogenizate obtained at a lower pressure, the yield of tetralin can be increased to 90–95% in terms of the naphthalene present in the crude to be hydrogenated.
KeywordsSulfide Al2O3 Tungsten Fractionation Naphthalene
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