H2SO4 alkylation by conversion of olefin feed to oligomers and sulfate esters

PATENT
H2SO4 alkylation by conversion of olefin feed to oligomers and sulfate esters
Patent number: 7977525
Issue date: Jul 12, 2011
Application number: 12/023,390
Inventors: Lawrence A. Smith, Jr., Abraham P. Gelbein, William M. Cross, Jr.
Original Assignee: Catalytic Distillation Technologies
A process for treating an alkylation feedstock comprising olefins, n-alkanes, and iso-alkanes, the process including: contacting at least a portion of the alkylation feedstock with sulfuric acid in a reaction zone under conditions to form sulfate esters of the olefins; separating the n-alkanes and the iso-alkanes from the sulfuric acid and the sulfate esters; recovering the n-alkanes and the iso-alkanes in a first product stream; and recovering the sulfate esters in a second product stream; wherein the sulfuric acid has a strength titrating as below 75 weight percent H2SO4/water mixtures.
BACKGROUND OF DISCLOSURE

1. Field of the Disclosure
Embodiments disclosed herein relate generally to the alkylation of paraflinic hydrocarbon feedstocks. More particularly, embodiments disclosed herein relate to a process for the preparation of an olefin-containing feed and an alkylation process using the prepared feed.

2. Background
Alkylation is the reaction of paraflins, usually isoparaflins, with an olefin in the presence of a strong acid which produces paraffins, e.g., of higher octane number than the starting materials and which boils in the range of gasolines. In petroleum refining, the alkylation reaction is generally the reaction of a C3 to C3 olefin with isobutane.

In refining alkylations, hydrofluoric or sulfuric acid catalysts are commonly used. For sulfuric acid catalyzed alkylation, low temperature or cold acid processes are favored, minimizing side reactions. In a typical process, the reaction is carried out in a reactor where the hydrocarbon reactants are dispersed into a continuous acid phase.

For example, U.S. Pat. No. 2,762,853 discloses an alkylation process including feeding isoparaflins, such as isobutane or isopentane and C2-C3 monoolefins to an alkylation reactor. The alkylation reaction is catalyzed with sulfuric acid in excess of 88 percent preferably in excess of 96 percent. The alkylation products are then separated into gasoline range components and heavier alkylate products among other finishing processes.

As another example, U.S. Pat. No. 2,859,260 discloses an alkylation process including reacting isoparaflins with olefins in the presence of a sulfuric acid catalyst. The reaction product is then separated to recover a hydrocarbon-rich phase and an acid-rich phase. The hydrocarbon-rich phase is further treated to remove catalyst esters from the hydrocarbon phase, among other downstream operations. Another example of a prior art alkylation process is disclosed in U.S. Pat. No. 3,013, 092.

Whereas the above alkylation reactions may occur in a single reactor, Albright et al. disclose a two-step alkylation process in which butyl sulfates or butyl fluorides are formed in the first step and alkylate is produced in the second step. See, for example, “Alkylation of Isobutane with C4 Olefins. 1 . First-Step Reactions Using Sulfuric Acid Catalyst,” Lyle F. Albright et al., Ind. Eng. Chem. Res. 1988, 27, 381-386 and “Alkylation of Isobutane with C4 Olefins. 3. Two-Step Process Using SulfuricAcid Catalyst,” Lyle F. Albright et al., Ind. Eng. Chem. Res. 1988, 27, 391-397.

Cold acid alkylation feedstocks generally contain both olefins and paraflins, typically in the C3-C3 range. The propane and n-butane in the feed are non-reactive, and build up in the alkylation process, requiring considerable fractionation energy to remove them. In addition, some C4 olefin feeds, such as those produced by dehydration of butanes, may contain aromatic compounds.

Accordingly, there exists a need for a process for decreasing the concentration of inert alkanes in alkylation feedstocks.

SUMMARY OF THE DISCLOSURE

In one aspect, embodiments disclosed herein relate to a process for treating an alkylation feedstock comprising ole

fins, n-alkanes, and iso-alkanes, the process including: contacting at least a portion of the alkylation feedstock with sulfuric acid in a reaction zone under conditions to fonn sulfate esters of the olefins; separating the n-alkanes and the iso-alkanes from the sulfuric acid and the sulfate esters; recovering the n-alkanes and the iso-alkanes in a first product stream; and recovering the sulfate esters in a second product stream; wherein the sulfuric acid has a concentration of less than 75 weight percent H2SO4.

In another aspect, embodiments disclosed herein relate to a process for treating a C4-rich alkylation feedstock comprising n-butenes, n-butanes, and iso-butanes, the process including: contacting at least a portion of the alkylation feedstock with sulfuric acid in a reaction zone under conditions to fonn sulfate esters of the n-butenes; separating the n-butanes and the iso-butanes from the sulfuric acid and the sulfate esters; recovering the n-butanes and the iso -butanes; and recovering the sulfate esters; wherein the sulfuric acid has a strength that titrates as below 75 weight percent H2SO4/water mixtures.

In another aspect, embodiments disclosed herein relate to a process for treating an alkylation feedstock comprising isoolefins, n-olefins, isoalkanes, and n-alkanes, the process including: feeding the alkylation feedstock to an oligomerization reaction zone under conditions of temperature and pressure to oligomerize at least a portion of the isoolefin; separating the oligomers from the unreacted isoolefin, olefins, n-alkanes, and iso-alkanes by fractionation; recovering at least a portion of the urlreacted isoolefin, olefins, n-alkanes, and iso-alkanes; and recovering the oligomers; contacting at least a portion of the recovered urlreacted isoolefin, olefins, n-alkanes, and iso-alkanes with sulfuric acid in a reaction zone under conditions to form sulfate esters of the olefins; separating the n-alkanes and the iso-alkanes from the sulfuric acid and the sulfate esters; recovering the n-alkanes and the iso-alkanes; and recovering the sulfate esters; wherein the sulfuric acid has a strength that titrates as below 75 weight percent H2SO4/water mixtures.

In another aspect, embodiments disclosed herein relate to a process for treating an alkylation feedstock comprising olefins, n-alkanes, and iso-alkanes, the process including: contacting at least a portion of the alkylation feedstock with hydrofluoric acid in a reaction zone under conditions to fonn alkyl fluorides of the olefins; separating the n-alkanes and the iso-alkanes from the hydrofluoric acid and the alkyl fluorides; recovering the n-alkanes and the iso-alkanes in a first product stream; and recovering the alkyl fluorides in a second product stream; wherein the hydrofluoric acid has a strength that titrates as below 75 weight percent HF/water mixtures.

Other aspects and advantages will be apparent from the following description and the appended claims.
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