Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By alkyl or aryl transfer between molecules – e.g.,...
Reexamination Certificate
1998-06-05
2002-12-31
Silverman, Stanley S. (Department: 1754)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By alkyl or aryl transfer between molecules, e.g.,...
C502S064000, C502S073000, C502S078000, C502S065000
Reexamination Certificate
active
06500997
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to catalysts and processes for the conversion of aromatic hydrocarbons and uses thereof in the production of aromatic hydrocarbons. In particular, the present invention relates to a novel catalyst comprising a zeolite with metal bismuth or oxides thereof supported thereon for the conversion of aromatic hydrocarbons, processes for the conversion of aromatic hydrocarbons using the catalyst, and uses thereof in the production of aromatic hydrocarbons.
BACKGROUND OF THE INVENTION
A large quantity of aromatic hydrocarbons such as benzene, toluene, xylene and C
9
aromatic hydrocarbons (C
9
A) may be obtained from the reforming and cracking processes of the petroleum distillates. The contents of toluene and C
9
A generally range from 40 to 50% of the total amount of the aromatic hydrocarbons dependent on different boiling ranges of the distillate feedstock and different processing methods. Normally C
9
A, C
10
aromatic hydrocarbons (C
10
A) and aromatic hydrocarbons of more than ten carbon atoms are referred to as heavy aromatic hydrocarbons in the past. Heavy aromatic hydrocarbons are mainly derived from the side products of the cracking process of light oil for producing ethylene, the aromatic hydrocarbons extraction process in the catalytic reforming in refinery, as well as toluene disproportionation and transalkylation process. For various sources of the feedstock oil and different processing methods, an aromatic hydrocarbon combination unit of 225 thousand ton xylene output per year may produce 10 to 30 thousand tons of heavy aromatic hydrocarbons each year. C
10
A and aromatic hydrocarbons of more than ten carbon atoms are of little use due to their complicated compositions and high boiling points. These aromatic hydrocarbons are not suitable for use as additive components in gasoline or diesel. Only some of them may be used as solvent oil or as the feedstock for separating durene, and most of the rest are used as burning fuel, causing waste of the resources.
With the development of plastic, synthetic fiber and synthetic rubber industries in the recent years, demand for benzene and xylene increases, market prices of which are higher than that of toluene and C
9
A. It is an important research subject in many countries to increase the production of aromatic hydrocarbons of high value from less valuable aromatic hydrocarbons through conversion processes of aromatic hydrocarbons including hydrodealkylation, toluene disproportionation and transalkylation reactions, thus making full use of the aromatic hydrocarbon resources. Toluene disproportionation is a process in which one mole of benzene and one mole of xylene are produced from two moles of toluene. Toluene may undergo transalkylation reaction with C
9
A to form xylene. Toluene may undergo transalkylation reaction with C
10
A to form C
9
A. Alkyl aromatic hydrocarbons such as C
9
A and C
10
A may undergo hydrodealkylation reaction to form aromatic hydrocarbons of fewer carbon atoms. A series of catalysts and processes for such reactions have already been developed.
In the processes for toluene disproportionation and transalkylation of the aromatic hydrocarbon feedstock substantially comprising toluene and C
9
A, mordenite is frequently used as the catalyst. For example, U.S. Pat. Nos. 2,795,629, 3,551,510, 3,729,521; 3,780,122 and 3,849,340 disclose catalysts, feedstock compositions and reaction conditions for toluene disproportionation and transalkylation process, in which catalysts used are not mentioned to comprise bismuth. Japanese patent 49-46295 discloses a catalyst for preparing alkyl benzene, which comprises a mordenite with, supported thereon, a zirconium cocatalyst anid optionally one or more components selected from silver, bismuth, copper and lead. The catalysts in the above patents have restricted performances, thus can not resist stringent reaction conditions. Therefore, in the toluene disproportionation and transalkylation processes where the above catalysts are used, C
9
A and heavy aromatic hydrocarbons of more than nine carbon atoms are not convertted adequately, hence yields of desired products relatively low, energy and material consumption on industrial scale units relatively high. So they are not economical.
Catalysts for converting C
10
A and heavy aromatic hydrocarbons of more than ten carbon atoms have been reported. For example, Japanese patent publication 51-29131 discloses a catalyst, MoO
3
—NiO/Al
2
O
3
(13 wt % Mo, 5 wt % Ni) composition, and a process for treating C
9
A and C
10
A feedstock with this catalyst. U.S. Pat. No. 4,172,813 discloses a catalyst composition comprising 3 wt % WO
3
, 5 wt % MoO
3
and a support consisting of 60 wt % mordenite and 40 wt % Al
2
O
3
; over this catalyst selective hydrodealkylation and transalkylation reactions of heavy reformate are effected, among which the main reaction is the transalkylation reaction between toluene and trimethylbenzene. U.S. Pat. No. 4,341,914 discloses a process for the conversion of C
10
A. In these references no catalyst containing bismuth is mentioned, contents of C
10
A in the feedstock entering the reactor is relatively low, no more than 20%, and the main disproportionation and transalkylation reaction is between toluene and C
9
A.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a novel catalyst for the conversion of aromatic hydrocarbons. The catalyst can be used in (1) disproportionation and transalkylation of aromatic hydrocarbon reactants comprising substantially toluene and C
9
A and/or C
10
A as well as in (2) hydrodealkylation and transalkylation of heavy aromatic hydrocarbons containing C
9
A and/or aromatic hydrocarbons of more than nine carbon atoms. The catalyst has better catalytic capacity for various kinds of conversion reactions of aromatic hydrocarbons and can be employed under stringent reaction conditions. The catalyst increases the yields of desired products such as benzene and xylene. Thus, contents of heavy aromatic hydrocarbons in the aromatic reactants to be converted can be highly increased, allowing drying and pre-purifying procedures omitted or simplified. The catalyst can improve the conversion of heavy aromatic hydrocarbons, enhance the selectivity and yields of benzene and xylene, make full use of the C
9
A and heavy aromatic hydrocarbon resources, lower material and energy consumption, and decrease expense.
Another object of the present invention is to provide a process for the conversion of aromatic hydrocarbons. The process overcomes the disadvantages of conventional disproportionation, transalkylation and hydrodealkylation processes that heavy aromatic hydrocarbons are restricted under a low content in the aromatic hydrocarbon reactants and that they are not suitable under stringent reaction conditions.
Still another object of the present invention is to apply said catalyst and process to the production of aromatic hydrocarbons, mainly benzene, xylene and C
9
A.
The catalyst for the conversion of aromatic hydrocarbons according to the present invention comprises by weight 20 to 90 parts of a crystalline aluminosilicate zeolite with a SiO
2
/Al
2
O
3
molar ratio of 10 to 100, 0.05 to 10 parts of metal bismuth or oxides thereof supported on the zeolite, 0 to 5 parts of one or more types of metal(s) M or oxides thereof, M being selected from the group consisting of molybdenum, copper, zirconium, strontium, lanthanum, rhenium, iron, cobalt, nickel and silver, and 10 to 60 parts of alumina as an adhesive.
The present invention also provides a process for the conversion of aromatic hydrocarbons, in which the aromatic hydrocarbon reactants contact the catalyst of the present invention to effect the conversion reaction.
The present invention further relates to the use of the catalyst and process of the present invention for the conversion of aromatic hydrocarbons in the production of aromatic hydrocarbons such as benzene, xylene and C
9
A from toluene, C
9
A, C
10
A and aromatic hydrocarbons of more than ten car
Cheng Wencai
Kong Dejin
Li Huaying
Yang Deqin
Zhu Zhirong
China Petro-Chemical Corporation
Ildebrando Christina
Pennie & Edmonds LLP
Silverman Stanley S.
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