2768724-A1 is referenced by 43 patents and cites 4 patents.

A method for the separation of para-xylene from an 8C aromatic charge by means of an adsorption stage, a liquid phase isomerization stage without addition of hydrogen and a vapor phase isomerization of ethylbenzene.- DETAILED DESCRIPTION - The initial charge contains ortho, meta and para-xylenes and ethylbenzene. The adsorption stage (18) comprises a mobile bed containing zeolite with a charge from which ethylbenzene has been separated by distillation (3) or adsorption. A liquid phase isomerization without hydrogen (26) is carried out on the raffinate after which the isomerate is distilled (27) to recover the toluene (29) which is re-cycled. The separated isomerate passes to a xylene distillation column (9) then re-cycled to the adsorption stage.; The ethylbenzene, separated in column (2) is separately isomerized (40) with hydrogen at a higher temperature then stabilized and distilled (5,2,9) and re-cycled to the adsorption stage. The residue from (5) is mixed with incoming fresh 8C charge (1). Pure para-xylene is recovered as extract (22) which can then be further purified by crystallization (7).TF - TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The ethylbenzene content of the second fraction from the adsorption stage (depleted in para-xylene and containing toluene, meta and ortho xylenes and ethylbenzene) is preferably 5 - 8% wt. The first, liquid phase isomerization, is carried out at 200 - 260degreesC., 20 - 30 bar and toluene/isomerization charge less than 15%, preferably 10 - 12%.; The zeolite catalyst is ZSM5 and the VVH is less than 10h-1, preferably 2 - 4h-1 The column (2) contains a mixture of xylenes and ethylbenzene and is regulated so that at least 75% of ethylbenzene is recovered as distillate : the residue passes to a column (9) and a distillate containing the xylenes is returned to the adsorption stage and a second residue (containing C9+ hydrocarbons and ortho-xylene) passes to a rerun column (12) from which a distillate of ortho-xylene is re-cycled to the first isomerization zone. The distillate from (2) is isomerized in the vapor phase with H2 and the isomerate obtained is distilled in a stabilization column (5) to eliminate light fractions, then re-cycled to (2). The isomerization is effected at 350 - 480degreesC., 5 - 20 bar and a VVH less than 10h-1, preferably 0.5 - 4 h-1.; The catalyst contains an acid phase and a group VIII metal and the H2/hydrocarbons ratio is less than 10, preferably 3 - 6.Alternatively, a catalytic dealkylation can be carried out at 420 - 460degreesC., 10 - 25 bar, preferably 14 - 20 bar, VVH of 10 - 12, and with a zeolite catalyst having an acid function and a hydro-dehydrogenating metal, preferably of group VIII. The H2/hydrocarbons ratio is 1.2 - 2.2, preferably 1.5 - 2.0. The mobile adsorption bed comprises a zeolite containing an element from K, Rb, Cs, Ba,Ca and Sr, and optionally water. The distillate from (2) or the fraction from adsorption contains at least 85% ethylbenzene, preferably 90%

Title
A new process for the production of para-xylene
Application Number
FR19970011920 19970923
Publication Number
2768724 (A1)
Application Date
September 23, 1997
Publication Date
March 26, 1999
Inventor
Alario Fabio
Minkkinen Ari
Assignee
Inst Francais Du Petrole
FR
IPC
C07C7/13
C07C 07/13
C07C15/08
C07C 15/08
C07C63/26
C07C 63/26
C07C15/00
C07C 15/00
C07C7/00
C07C 07/00
C07C5/00
C07C 05/00
C07C4/00
C07C 04/00
C07C15/08
C07C 15/08
C07C7/13
C07C 07/13
C07C7/04
C07C 07/04
C07C5/27
C07C 05/27
C07C4/18
C07C 04/18
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