Process and Apparatus for Alkylation of Aromatic with Olefin Using Impure Aromatic Recycle

Abstract

Processes and apparatus for the alkylation of aromatic compound with mono-olefin aliphatic compound in the presence of solid alkylation catalyst use a lights distillation for obtaining desired selectivities to arylalkane in a energy efficient manner. The processes and apparatus offer the potential for debottlenecking existing arylalkane production facilities and reducing the size and energy requirements for a new arylalkane production facility.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application is a Division of prior copending application Ser. No. 11 / 042,587, filed Jan. 25, 2005, which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION [0002] This invention relates to processes and apparatus for the alkylation of aromatic compound with aliphatic mono-olefin compound in which the aromatic compound is provided in a stoichiometric excess and unreacted aromatic compound is recycled. BACKGROUND TO THE INVENTION [0003] Alkylation of aromatic compounds produces arylalkanes that may find various commercial uses, e.g., alkylbenzenes that can be sulfonated to produce detergents. In the alkylation process, aromatic compound is reacted with olefin of the desired molecular weight to produce the sought arylalkane. The alkylation conditions comprise a catalyst such as aluminum chloride, hydrogen fluoride, or zeolitic catalysts and elevated temperature. [0004] The alkylation, however, is not selective a...

AI Technical Summary

Benefits of technology

[0010] In accordance with this invention, it has been found that viable aromatic alkylation processes can be provided wherein a portion of the aromatic compound recycled is impure. In the processes and apparatus of this invention, a lights distillation is used to recover a portion of the unreacted aromatic compound contained in the effluent from an alkylation reaction zone. The aromatic compound recovered by the lights distillation is recycled to the alkylation reaction zone, and the remaining portion of the unreacted aromatic compound is recovered in a subsequent distillation. The column size and energy requirements for the subsequent distillation are thus reduced. Because the lights distillation need not provide a relatively pure aromatic stream, the energy requirements and size of the lights distillation can be commercially viable. Often, the lights distillation is effected using less than 5 theoretical distillation trays, especially a flash distillation. Thus, the overhead can contain appreciable amounts of arylalkane product as well as paraffins, if paraffins are present in the alkylation reactor effluent. Although arylalkane can be reacted to produce heavies under alkylation conditions, the processes of this invention can still provide an alkylation reaction effluent without an undue amount of heavies.

[0027] Thus, the processes of this invention can reduce the amount of aromatic compound passing to a refining system for the arylalkane. Therefore, for instance, the size of the aromatic compound distillation for an existing facility can readily be debottlenecked, and for a grass roots facility, the aromatic compound distillation can be designed to be smaller and require less reboiler demand. Advantageously the distillation of step b does not need to achieve a high degree of separation of the aromatic compound from the arylalkane to achieve these advantages or to achieve desirable arylalkane product quality.

Problems solved by technology

The alkylation, however, is not selective and can produce dimers, dialkylaryl compounds and diaryl compounds (“heavies”) and can affect skeletal isomerization of the olefin, resulting in a loss of selectivity to the sought arylalkane structure.

The formation of dialkylaryl compounds is particularly problematic as the reaction approaches complete conversion of the olefin and the greater concentration of the arylalkane since the likelihood has increased that an olefin molecule will react with an arylalkane molecule rather than a molecule of the aromatic compound in the feed.

The capacity of a distillation column, at a given degree of separation, can thus be limited by the availability of thermal fluid.

Similarly, the size of the benzene column itself can pose a bottleneck.

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