Xylene isomerization
AssigneeExxon Research & Engineering Co.
InventorsWicher T. Koetsier, Johannes P. Verduijn
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Abstract
Reduced downgrading in xylene isomerization of ethylbenzene-depleted feeds is achieved by carrying the process out over gallosilicate or borosilicate zeolites, preferably in the form of compositions comprising a core of catalytically-inactive crystalline silica with an overlying zeolite layer. The composites are prepared by introducing preformed silica particles, preferably with a crystallite size greater than 0.1.mu., into a reaction mixture comprising a silicon source, a source of the modifying element, and preferably an organic template such as a tetraalkylammonium compound. The weight ratio of the silica core to SiO.sub.2 in the reaction mixture is preferably 0.5:1 to 25:1.
Claims6
A process for obtaining ethylbenzene and para-xylene and/or ortho-xylene from a mixed C.sub.8 feed, which process comprises recovering ethylbenzene from the mixed C.sub.8 feed to leave an ethylbenzene-depleted feed containing mixed xylenes and less than 5 wt.% ethylbenzene, thereafter contacting the ethylbenzene-depleted feed under isomerization conditions with a catalyst comprising a gallosilicate zeolite having a mole ratio of SiO.sub.2 :Ga.sub.2 O.sub.3 greater than 5 and a consistent index of from 1 to 12, said gallosilicate zeolite overlying a silica core, the silica core and the zeolite having substantially the same crystalline structure, to give an isomerate enriched in para-xylene and ortho-xylene, and recovering para-xylene and/or ortho-xylene from the isomerate which is thereafter recycled to the ethylbenzene recovery step.
Dependencies are inferred from the claim text.