Alkylation process

Details Alkylation process Alkylation process

2000-10-31

2003-04-22

Dang, Thuan D. (Department: 1764)

Chemistry of hydrocarbon compounds

Saturated compound synthesis

By condensation of a paraffin molecule with an olefin-acting...

C585S709000, C585S723000, C585S724000, C585S730000

Reexamination Certificate

active

06552241

ABSTRACT:

The present invention relates to a method and/or system for the alkylation of an olefin with an isoparaffin utilizing a catalyst mixture comprising a volatility reducing additive, hydrogen fluoride and water. More specifically, the invention relates to a method and/or system for removing water from the catalyst mixture to avoid water buildup therein.
BACKGROUND OF THE INVENTION
The use of catalytic alkylation processes to produce branched hydrocarbons having properties that are suitable for use as gasoline blending components is well known in the art. Generally, the alkylation of olefins by saturated hydrocarbons, such as isoparaffins, is accomplished by contacting the reactants with an acid catalyst to form a reaction mixture, settling the reaction mixture to separate the catalyst from the hydrocarbons, thereby forming a catalyst mixture phase and an alkylation reactor effluent, and further separating the alkylation reactor effluent, for example, by fractionation, to recover the separate product streams. Normally, the alkylation reactor effluent of the alkylation process contains hydrocarbons having five to ten carbon atoms per molecule. In order to have the highest quality gasoline blending stock, it is preferred for the alkylate hydrocarbons formed in the alkylation process to be highly branched and contain seven to nine carbon atoms per molecule.
Recent efforts to improve conventional hydrogen fluoride catalyzed alkylation processes have resulted in the development of new catalyst compositions that contain hydrogen fluoride and a volatility reducing additive. These new catalyst compositions have been found to be quite effective as an alkylation catalyst and to provide many other favorable benefits.
In such processes which include a volatility reducing additive in the catalyst, the regeneration of the catalyst mixture typically includes stripping a slip stream of the circulating catalyst mixture with an isoparaffin producing an overhead stream containing isoparaffin, hydrofluoric acid and water (preferably substantially absent of water) and a bottoms stream containing hydrofluoric acid (preferably in very small quantities), volatility reducing additive, and an acid soluble oil (ASO) produced as a by-product in the alkylation reaction. Because of the azeotrope formed between HF and water, it is often not possible to provide dry HF as the overhead stream. Thus, as described in U.S. Pat. No. 5,759,937 issued to Keith W. Hovis and Richard L. Anderson, a stripper side-draw stream is often required to remove water from the system by removing the HF/water azeotrope material from the sidedraw and allowing substantially water free HF to pass overhead. However, during certain upset conditions wherein excess water enters the system, either with the makeup HF or from feed contaminant upsets which can generate water, the sidedraw stream often cannot remove enough of the excess water. Excess water in the catalyst mixture can result in lower alkylation quality and can have other non-beneficial effects on the alkylation process, including corrosion problems. Therefore, development of an efficient process and/or system for removing water from a circulating alkylation catalyst mixture would be a significant contribution to the art.
BRIEF SUMMARY OF THE INVENTION
It is, thus, an object of the present invention to provide an improved process for removing water from an alkylation catalyst mixture.
A further object of the present invention is to provide an improved system to be used in removing water from an alkylation catalyst mixture which is economical in construction and reliable and efficient in operation.
A yet further object of the present invention is to provide a method and/or system for preventing the accumulation of water in the catalyst mixture of an alkylation process.
Still another object of the present invention is to provide a method and/or system for preventing the accumulation of water in the catalyst mixture of an alkylation process while minimizing the loss of HF with the water removed from the system.
A yet further object of the present invention is to provide an improved system to be used in preventing the accumulation of water in the catalyst mixture of an alkylation process which includes means for controlling the concentration of water in the catalyst mixture.
According to a first embodiment of the present invention, an alkylation process is provided and comprises the steps of:
a) contacting a hydrocarbon mixture comprising at least one olefin and at least one isoparaffin with a catalyst mixture comprising HF, a volatility reducing additive and water within a reaction zone to thereby produce a reaction zone effluent;
b) passing the reaction zone effluent to a settler wherein the reaction zone effluent is separated into a hydrocarbon phase and a catalyst mixture phase comprising HF, water and volatility reducing additive;
c) removing at least a portion of the hydrocarbon phase from the settler to form a settler effluent stream;
d) passing the settler effluent stream to a first separator;
e) removing an overhead stream from the first separator;
f) condensing at least a portion of the overhead stream to form an HF/water stream comprising HF, water and volatility reducing additive; and
g) passing the HF/water stream to a second separator for separation into a modified HF stream comprising HF and volatility reducing additive and into an HF/water azeotrope stream comprising HF and water.
According to a second embodiment of the present invention, an alkylation process is provided and comprises the steps of:
a) contacting a hydrocarbon mixture comprising at least one olefin and at least one isoparaffin with a catalyst mixture comprising HF, a volatility reducing additive and water within a reaction zone to thereby produce a reaction zone effluent;
b) passing the reaction zone effluent to a settler wherein the reaction zone effluent is separated into a hydrocarbon phase and a catalyst mixture phase comprising HF, water, volatility reducing additive and acid soluble oil;
c) removing at least a portion of the hydrocarbon phase from the settler to form a settler effluent stream;
d) passing the settler effluent stream to a first separator;
e) removing a first separator overhead stream from the first separator;
f) condensing at least a portion of the first separator overhead stream to form an HF/water stream comprising HF, water and volatility reducing additive;
g) passing the HF/water stream to a second separator for separation into a modified HF stream comprising HF and volatility reducing additive and into an HF/water azeotrope stream comprising HF and water; and
h) passing at least a portion of the catalyst mixture phase to a third separator for separation into a third separator overhead stream comprising HF and water and into a third separator bottoms stream comprising HF, water, ASO and volatility reducing additive.
According to a third embodiment of the present invention, an alkylation process is provided and comprises the steps of:
a) contacting a hydrocarbon mixture comprising at least one olefin and at least one isoparaffin with a catalyst mixture comprising HF, a volatility reducing additive and water within a reaction zone to thereby produce a reaction zone effluent;
b) passing the reaction zone effluent to a settler wherein the reaction zone effluent is separated into a hydrocarbon phase and a catalyst mixture phase comprising HF, water, volatility reducing additive and acid soluble oil;
c) removing at least a portion of the hydrocarbon phase from the settler to form a settler effluent stream;
d) passing the settler effluent stream to a first separator;
e) passing at least a portion of the catalyst mixture phase to a second separator for separation into a second separator overhead stream comprising HF and water and separation into a second separator bottoms stream comprising HF, water, ASO and volatility reducing additive;
f) blocking the passing of the at least a portion of the catalyst mixture phase to the second separator in step e;
g) removing a first separator overh

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