Process and system for alkylation of aromatic compounds

Details Process and system for alkylation of aromatic compounds Process and system for alkylation of aromatic compounds

1997-06-20

2001-11-13

Knode, Marian C. (Department: 1764)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Including heat exchanger for reaction chamber or reactants...

C422S186220, C422S234000

Reexamination Certificate

active

06315964

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention generally relates to a reactive distillation process and system for the alkylation of aromatic compounds with olefins.
Alkylated aromatics, including linear alkyl benzenes (LAB's) having long chains (typically 10-14 carbons), are commonly used, commercial products. LAB's are commonly sulfonated to thereby produce surfactants.
Typically, alkylated aromatics are manufactured commercially using classic Friedal-Crafts chemistry, employing catalysts such as aluminum chloride, or using strong acid catalysts such as hydrogen fluoride, for example, to alkylate benzene with olefins. While such methods produce high conversions, the selectivity to the 2-phenyl isomer is low, generally being about 30% or less. LAB's with a high percentage of the 2-phenyl isomer are highly desired because such compounds when sulfonated have long “tails” which provide enhanced solubility and detergent properties.
Reactive distillation methods for producing short chain alkylated aromatics are known. These methods are typically directed toward reacting gaseous phase short chain olefins, such as ethylene or propylene, with benzene.
SUMMARY OF THE INVENTION
It has now been recognized that alkylation reactions using long chain olefins present peculiar problems. With longer chain liquid olefin reactants, lower space velocities may be necessary due to the low mutual solubilities of the feed components. Due to lower reaction temperatures, alkylation reactions involving long chain olefins may be prone to the accumulation of water brought into the alkylation unit with the feeds or formed as a by-product in the catalyst bed, leading to deactivation of the catalyst. Furthermore, because liquid olefins mix much less readily with liquid aromatics than do gaseous olefins, different mixing procedures are necessary in order to achieve high yields of desired LAB's. In addition, the use of longer chain liquid olefin reactants may lead to a greater tendency for the formation of carbonaceous deposits and heavy organics on the catalyst bed. The formation of carbonaceous deposits and heavy organics on the catalyst bed. By-product formation may generally be more difficult to control with the higher molecular weight olefin coreactants.
Therefore, a need exists for a method of alkylation of aromatics with long chain olefins that has high olefin conversion, high selectivity and having long catalyst lifetimes. In particular, a need exists for a method of producing alkylated aromatics from liquid industrial reactant feeds containing water that avoids water deactivation of the catalyst and which ensures adequate mixing of the liquid aromatic and olefin reactants. A need also exists for such a method having high substrate olefin conversion and long catalyst lifetimes. More particularly, a need exists for a method of LAB production having high substrate olefin conversion, high selectivity to 2-phenyl isomer LAB, and employing a catalyst having long lifetimes and easy handling. LAB is useful as starting material to produce sulfonated LAB, which itself is useful as a surfactant. This invention provides a solution to one or more of the problems and disadvantages described above.
This invention, in one broad respect, is a process useful for preparing alkylated aromatic compounds comprising introducing an aromatic compound having from about 6 to about 30 carbons and an olefin having from about 8 to about 30 carbons above a catalyst bed containing an alkylation catalyst under conditions such that the olefin and the aromatic compound react to form an alkylated aromatic compound; allowing the alkylated aromatic compound and unreacted aromatic compound to descend into a reboiler from the catalyst bed; withdrawing the alkylated aromatic compound from the reboiler; and heating contents of the reboiler such that the aromatic compound refluxes to contact the catalyst bed.
In a second broad respect, this invention is a system for manufacturing alkylated aromatic compounds, comprising a reactor containing an alkylation catalyst bed; one or more injectors in the reactor for introducing aromatic compound, olefin or a mixture of aromatic compound and olefin above the catalyst bed; a reboiler for collecting, heating and refluxing unreacted aromatic compound descending from the reactor, the reboiler positioned below and in communication with the reactor, the reactor and reboiler being generally in vertical alignment; and a means for withdrawing alkylated aromatic compound from the reboiler.
Use of the process and system of this invention for alkylation of aromatics with long chain olefins, particularly &agr;-olefins, or long chain olefin/paraffin mixed feed stocks advantageously achieves high conversion rates and long catalyst lifetimes by using the reactor configuration specified above. When the process and system of this invention is used for selective benzene monoalkylation by liquid olefin or liquid olefin/paraffin mixed feed stocks, high selectivity to 2-phenyl product isomers is advantageously obtained. Additional benefits may be derived from the process and system of this invention by utilizing a column of solid acid catalyst and a water condenser with water take-off above the catalyst bed as depicted, for instance, in FIG.
1
and
FIG. 2. A
process operated in accordance with the representative apparatus of this invention depicted in FIG.
1
and
FIG. 2
has the advantage that rising benzene vapor from the reboiler continuously cleans the catalyst of heavy organics to thereby increase lifetime of the catalyst. Improved catalyst life and performance during benzene alkylation is enhanced by continuous water removal from the catalyst bed (without the need for a predrying step) and by better mixing of the reactants and increased effective benzene concentration in the alkylation reaction zone. In addition, when used for selective benzene monoalkylation this invention advantageously produces only low amounts of dialkylated benzene, which is not particularly as useful for detergent manufacture, as well as only low amounts of tetralin derivatives.
Certain terms and phrases have the following meanings as used herein.
“Meq/g” means milliequivalents of titratable acid per gram of catalyst, which is a unit used to describe acidity of the catalysts. Acidity is generally determined by titration with a base, as by adding excessive base, such as sodium hydroxide, to the catalyst and then back titrating the catalyst.
“Conv.” and “Conversion” mean the mole percentage of a given reactant converted to product. Generally, olefin conversion is about 95 percent or more in the practice of this invention.
“Sel.” and “Selectivity” mean the mole percentage of a particular component in the product. Generally, selectivity to the 2-phenyl isomer is about 70 or more in the practice of this invention.


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