Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By condensation of entire molecules or entire hydrocarbyl...
Reexamination Certificate
1998-04-08
2002-11-26
Silverman, Stanley S. (Department: 1754)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By condensation of entire molecules or entire hydrocarbyl...
C585S475000, C502S064000, C502S066000, C502S074000, C502S078000
Reexamination Certificate
active
06486372
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a catalyst for transforming aromatic hydrocarbons. More precisely, it relates to a catalyst for dismutation of toluene to produce benzene and xylenes, and transalkylation of alkylaromatic hydrocarbons, preferably transalkylation of toluene and aromatic compounds containing at least 9 carbon atoms per molecule, preferably trimethylbenzenes, to produce xylenes.
SUMMARY OF THE INVENTION
The catalyst of the present invention contains a mordenite with a high silicon content and in a large proportion with respect to a binder. At least part of this mordenite is present in its acid form, generally in a proportion of 40% to 90% by weight, preferably 75% to 85% by weight, and the binder, preferably alumina, is generally present in a proportion of 10% to 60% by weight, preferably 15% to 25% by weight. The mordenite contains less than 0.1% by weight, preferably less then 0.05% by weight, of sodium, and has an SiO
2
/A
2
O
3
molar ratio of over 70, preferably in the range 80 to 120. The catalyst also contains at least one metal from the group formed by elements from groups VI, VII and VUI of the periodic table, preferably palladium, platinum, rhenium and/or nickel, more preferably platinum and/or nickel, and most preferably nickel, in an amount, expressed with respect to the mordenite, in the range 0.01% to 5% by weight, preferably in the range 0.1% to 3% by weight. Finally, the catalyst optionally additionally contains at least one metal from the group formed by elements from groups III and IV of the periodic table in an amount, expressed with respect to the mordenite, which is in the range 0.01% to 5%, preferably 0.1% to 3% by weight. The present invention also concerns the use of the catalyst for dismutation and/or transalkylation of alkylaromatic hydrocarbons.
BACKGROUND OF THE INVENTION
A number of dismutation and transalkylation catalysts have already been described in the prior art, some being based on mordenite and metals. U.S. Pat. No. 3,281,483 mentions mordenites exchanged essentially with silver or nickel ions and U.S. Pat. No. 3,780,121 describes a mordenite exchanged with metals from group IB of the periodic table characterized by an SiO
2
/Al
2
O
3
molar ratio in the range 12 to 80. Further, U.S. Pat. No. 3,629,351 also describes a mordenite containing ions of metals from groups IB, VA, VIA, IIA and VIII of the periodic table.
More recently, Japanese patent JP-A-63301834 describes a catalyst comprising a mordenite comprising a metal which can, inter alia, be nickel and can be introduced during synthesis of the zeolite. In U.S. Pat. Nos. 4,151,120, 41,180,693 and 4,210,770, the catalyst comprises mordenite with a SiO
2
/Al
2
O
3
ratio in the range 10 to 100 and at least one metal selected from the group formed by Ni, Co, Ag and Pd, the mordenite undergoing at least one calcining treatment in the presence of steam. Finally, in U.S. Pat. No. 5,475,180, the Ni on mordenite catalyst is modified in the presence of a heavy reformate.
DETAILED DESCRIPTION
We have discovered that, surprisingly, a catalyst for transforming aromatic hydrocarbons containing a mordenite zeolite with an SiO
2
/Al
2
O
3
molar ratio of over 70, preferably in the range 80 to 120, and at least one metal from the group formed by elements from groups VI, VII and VIII, preferably palladium, platinum, rhenium and/or nickel, more preferably platinum and/or nickel, and most preferably nickel, in an amount, expressed with respect to the mordenite, in the range 0.01% to 5% by weight, preferably 0.1% to 3% by weight, the catalyst also optionally comprising at least one metal from the group formed by elements from groups III and IV, results in substantially improved performances, principally in terms of toluene conversion and stability over time, over the catalysts described in U.S. Pat. Nos. 4,151,120, 41,180,693 and 4,210,770 where the catalyst comprises mordenite in an SiO
2
/Al
2
O
3
ratio in the range 10 to 100 and at least one metal selected from the group formed by Ni, Co, Ag and Pd, for the dismutation of toluene to produce benzene and xylenes, and for the transalkylation of toluene and AC9(+) compounds to produce xylenes.
The present invention concerns a catalyst for dismutation and/or transalkylation of toluene and/or alkylaromatic compounds containing at least 9 carbon atoms per molecule which contains:
40% to 90% by weight, preferably 75% to 85% by weight, of at least one zeolite with a mordenite structure which is at least partially in its acid form, characterized in that its Si/Al molar ratio is over 35, preferably in the range 40 to 60, said mordenite containing at most 0.1% by weight (expressed with respect to zeolite) of sodium, preferably at most 0.05% by weight of sodium;
0.01% to 5%, preferably 0.1% to 3% by weight, with respect to the zeolite, of at least one metal from the group formed by elements from groups VI, VII and VIII of the periodic table, i.e., selected from the group formed by chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium and platinum, preferably selected from the group formed by platinum, palladium, rhenium and nickel, preferably again platinum or nickel and most preferably nickel;
10% to 60% by weight, preferably 15% to 25% by weight, of at least one binder, preferably alumina.
The catalyst preferably also contain 0.01% to 5%, preferably 0.1% to 3% by weight, with respect to the zeolite, of at least one metal from the group formed by elements from groups III and IV of the periodic table, i.e., selected from the group formed by germanium, tin, lead, boron, gallium, indium, thallium and silicon, preferably selected from the group formed by tin and indium.
The present invention also concerns a process for dismutation and/or transalkylation of toluene and/or alkylaromatic compounds containing at least 9 carbon atoms per molecule, preferably for dismutation of toluene to produce benzene and xylenes and/or transalkylation of toluene with AC9(+) compounds to produce xylenes from toluene-AC9(+) mixtures generally containing at most 50 mole % of AC9(+), the process being characterized in that the catalyst of the invention is used.
Any zeolite with a mordenite structure which is known to the skilled person is suitable for the present invention. Thus, for example, the zeolite used as a base to prepare the catalyst of the present invention is “large pore” mordenite in its sodium form, or “small pore” mordenite in its sodium form. When a commercially available zeolite is used which has the required specifications concerning the Si/Al ratio, at least one ion exchange step is generally carried out in at least one NH
4
NO
3
solution to obtain a zeolite with a sodium content of less than 0.1%, preferably less then 0.05% by weight, and in its NH
4
+
form.
It is also possible to start from a mordenite with a molar Si/Al ratio which is lower and generally in the range 5 to the desired value. Thus at least one dealumination step will be required to reach the desired Si/Al molar ratio. Within this context, any dealurnination technique known to the skilled person can be used.
Using the operating method described in U.S. Pat. No. 4,780,436 in particular, calcining is carried out in a stream of dry air, then at least one ion exchange step using at least one NH
4
NO
3
solution is carried out, to eliminate practically all of the alkaline cations, in particular sodium, present in the cationic position in the zeolite, then at least one framework dealumination cycle, steaming followed by an acid attack step, is carried out, comprising at least one cacining step carried out in the presence of steam, at a temperature which is generally in the range 550° C. to 850° C., followed by at least one acid attack step. The framework dealumination cycle, comprising at least one calcining step carried out on the mordenite in steam and at least one attack step carried out in an acid medium, can be repeated as many times as is necessary to obtain the desi
Alario Fabio
Merlen Elisabeth
Ildebrando Christina
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Silverman Stanley S.
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