Production of alkylated aromatic compounds using...

Details Production of alkylated aromatic compounds using... Production of alkylated aromatic compounds using...

2001-03-20

2004-06-08

Dang, Thuan D (Department: 1764)

Chemistry of hydrocarbon compounds

Aromatic compound synthesis

By condensation of entire molecules or entire hydrocarbyl...

C585S455000

Reexamination Certificate

active

06747182

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the production of alkylated aromatic compounds such as, for example, alkyl naphthalenes and substituted alkyl naphthalenes.
BACKGROUND OF THE INVENTION
Alkylaromatic fluids have been proposed for use as certain types of functional fluids where good thermal and oxidative properties are required. For example, U.S. Pat. No. 4,714,794 describes the monoalkylated naphthalenes as having excellent thermal and oxidative stability, low vapor pressure and flash point, good fluidity and high heat transfer capacity and other properties which render them suitable for use as thermal medium oils. The use of a mixture of monoalkylated and polyalkylated naphthalenes as a base for synthetic functional fluids is described in U.S. Pat. No. 4,604,491. U.S. Pat. Nos. 4,211,665 and 4,238,343 describe the use of alkylaromatics as transformer oils.
The alkylated naphthalenes are usually produced by the alkylation of naphthalene or a substituted naphthalene in the presence of an acidic alkylation catalyst such as a Friedel-Crafts catalyst, for example, an acidic clay as described in U.S. Pat. Nos. 4,714,794 or 4,604,491, or a Lewis acid such as aluminum trichloride as described in U.S. Pat. Nos. 4,211,665 and 4,238,343. The use of a collapsed silica-alumina zeolite for the catalytic alkylation of aromatic compounds such as naphthalene is disclosed in U.S. Pat. No. 4,570,027. The use of various zeolites including intermediate pore size zeolites such as ZSM-5 and large pore size zeolites such as zeolite L and ZSM-4 for the alkylation of various monocyclic aromatics such as benzene is disclosed in U.S. Pat. No. 4,301,316.
In the formulation of functional fluids based on the alkyl naphthalenes, it has been found that the preferred alkyl naphthalenes are the mono-substituted naphthalene since they provide the best combination of properties in the finished product. Because the mono-alkylated naphthalenes posses fewer benzylic hydrogens than the corresponding di-substituted or polysubstituted versions, they have better oxidative stability and therefore form better functional fluids and additives. In addition, the mono-substituted naphthalenes have a kinematic viscosity in the desirable range of about 5-8 cSt (at 100° C.) when working with alkyl substituents of about 14 to about 18 carbon atoms chain length. Although the mono-alkylated naphthalenes may be obtained in admixture with more highly alkylated naphthalenes using conventional Friedel-Crafts catalysts such as those mentioned above, or by the use of zeolites such as USY, the selectivity to the desired mono-alkylated naphthalenes is not as high as desired.
Several recent advances have been made in this area which improve the yields of the desired mono-alkylated naphthenes.
U.S. Pat. No. 5,034,563 to Ashjian et al., which is incorporated herein by reference in its entirety, teaches use of a zeolite containing a bulky cation. The use of, e.g., USY with cations having a radius of at least about 2.5 Angstroms increases selectivity for desired products. Taught as suitable were zeolites containing hydrated cations of metals of Group IA, divalent cations, especially of Group IIA, and cations of the Rare Earths. The patent had examples in which H+, NH4+, and Na+ were added to USY zeolite by a procedure involving forming a slurry of zeolite and liquid, 1 hour of stirring, decantation, and a repeat of the exchange procedure.
U.S. Pat. No. 5,177,284, which is incorporated herein by reference in its entirety, discusses the desirable properties of alkylated naphthalene fluids with higher alpha:beta ratios, including improved thermal and oxidative stability. Le et al. found that several parameters influenced the alpha:beta ratio of the alkylated naphthalene products, including steaming the zeolite, lowering the alkylation temperature, or the use of acid-treated clay. Steamed USY catalyst gave excellent results in the examples. The patentees also mentioned use of zeolites with reduced activity due to base exchange, alkaline earth ion exchange, and use of boron-zeolite beta.
U.S. Pat. No. 5,191,135, which is incorporated herein by reference in its entirety, discloses the effect of co-feeding water for this reaction when using a large pore zeolite catalyst, such as zeolite Y. Adding from 1-3 wt % water to the feed improved the alkylation reaction, a result attributed to suppression of zeolite acid site activity.
U.S. Pat. No. 5,191,134, which is incorporated herein by reference in its entirety, disclosed a similar alkylation process using MCM-41.
U.S. Pat. No. 5,457,254 to Ardito et al., which is incorporated herein by reference in its entirety, discloses a naphthalene alkylation process whereby the presence of both ammonium and protonic species increases selectivity for production of long chain mono-alkyl substituted naphthalenes.
The present inventors did additional work to see if they could further improve this alkylation process. They wanted to increase the efficiency of the reaction both in terms of conversion and yields.
The present inventors have discovered that an alkylation catalyst comprising a large pore zeolite which has been dealuminated to remove non-framework aluminum by selective ion exchange in acidic conditions, provides unexpectedly superior activity over a corresponding catalyst without the dealumination treatment. The inventors also discovered that the catalyst of the invention is effective in alkylation of other compounds containing two aromatic rings including, but not limited to, diphenyl oxide, diphenyl sulfide, diphenyl methane, and biphenyl.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a process for preparing alkyl substituted aromatic compounds, including long chain alkyl substituted aromatic compounds, which comprises alkylating an aromatic compound with an alkylating agent possessing an alkylating aliphatic group having at least six carbon atoms under alkylation reaction conditions in the presence of an alkylation catalyst comprising a porous crystalline zeolite which has been selectively dealuminated, under acidic conditions, to remove non-framework aluminum.
DETAILED DESCRIPTION
The starting materials for the production of the alkylated aromatic compounds include the aromatic compounds themselves. The term “aromatic compound” is understood by those of ordinary skill in the art to refer to any compound having at least one aromatic ring, such as, for example, benzene, pyridine, naphthalene. The aromatic compound may be unsubstituted or substituted with, by way of non-limiting example, halogen, alkyl, alkenyl, nitro, amino, amido, carboxyl, carboxamido, etc. Naphthalenes include naphthalene itself as well the substituted naphthalenes which may contain, for example, one or more short chain alkyl groups containing up to about eight carbon atoms, such as methyl, ethyl or propyl. Suitable alkyl-substituted naphthalenes include, for example, alpha-methylnaphthalene, dimethylnaphthalene and ethylnaphthalene. Naphthalene itself is preferred since the resulting mono-alkylated products have better thermal and oxidative stability than the more highly alkylated materials for the reasons set forth above.
Various other aromatic chemical compounds containing one or two aromatic rings in the structure can also be alkylated by this process. Such compounds include, but are not limited to, alkylbenzenes such as benzene, toluene, xylenes, ethyl benzene, methylethyl benzene, trimethyl benzene, and propyl benzene. Also included are other two-ring aromatic compounds such as, for example, diphenyl oxide, diphenyl sulfide, diphenyl methane, biphenyl, and alkyl-substituted derivative compounds.
The alkylating agents which are used to alkylate the naphthalene include, but are not limited to, any aliphatic or aromatic organic compound having one or more available alkylating aliphatic groups capable of alkylating the naphthalene. The alkylating group itself should have at least about 6 carbon atoms, preferably at least about 8, and still more preferably at least about 12 carbon atom

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