Catalyst of mixed fluorosulfonic acids

Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing

Reexamination Certificate

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C502S168000, C502S169000, C502S170000, C502S216000

Reexamination Certificate

active

06395673

ABSTRACT:

BACKGROUND OF THE INVENTION
In the oil refining industry, the term “alkylation” is used to describe processes in which isoparaffins (e.g., isobutane) are reacted with olefins (e.g., 1-butene) to form the “alkylate” or higher molecular weight branched paraffins (typically isooctane or 2,2,4-trimethylpentane in the isobutane/1-butene case). The higher molecular weight branched paraffins produced have desirable high research octane numbers, making the product an excellent blending component for gasoline. Typically, in the example reaction described, a large excess of the 1-butene is used to drive olefin conversion, and the excess isobutane is recovered and recycled.
An important alkylation method is an acid-catalyzed process. Concentrated sulfuric acid and more recently, hydrofluoric acid have been used as the catalyst. However, there has been continuing interest in the development of a solid catalyst to replace sulfuric and hydrofluoric acids.
A solid-supported liquid catalyst in a moving catalyst zone, through which the alkane/alkene stream can pass, has been reduced to practice by, for instance, Hommeltoft and Topsoe in U.S. Pat. No. 5,245,100, who describe a catalyst of trifluoromethanesulfonic acid (triflic acid CF
3
SO
3
H)adsorbed on, inter alia, silica. As the loading is reduced with the Hommeltoft and Topsoe catalyst system, the useful lifetime of the catalyst system decreases sharply to impracticably short time periods.
Clerici, et al., in U.S. Pat. No. 5,659,105, describe an alkylation catalyst composed of a silica-based material having surface Si-OH groups esterified with a linear perfluorosulfonic acid of the formula CF
3
(CF
2
)
n
SO
3
H, where n is 0-11. Clerici, et al., asserted the catalyst showed higher activity than the triflic acid adsorbed on silica described by Hommeltoft and Topsoe. However, the esterified —Si—OH groups are not stable and are removed from the silica in use.
A further problem is the tendency for the acid catalysts to become deactivated or passified, a process believed to be associated with the formation of stable esters between the strong acid and the feedstock olefin. While such passivation occurs with stationary acid catalysts, the effect is minimized by the flow-through, recovery, and recycle associated with mobile catalysts. Hommeltoft, et al., in Ind. Eng. Chem. Res. 1997, 36, 3491-3497, provide a discussion of such passivation mechanisms. Hommeltoft, et al., report that while the addition of a mobile Lewis acid such as boron trifluoride, antimony pentafluoride, or aluminum chloride does improve the lifetime of the stationary catalyst, it also introduces handling problems with the volatile and hazardous Lewis acid. It is desirable to minimize the mobile acid throughput and recycle.
The catalyst of the present invention provides economies over the sulfuric acid process and a marked reduction in process hazards over the hydrofluoric acid process. Additionally, the catalyst of this invention provides a longer catalyst life over both the acid modified silica and the mobile acid supports of the prior art. By comparison with the mobile acid treated supports of the prior art, the amount of mobile acid required is substantially reduced.
SUMMARY OF THE INVENTION
The present invention comprises a catalyst comprising A) a stationary acid component selected from the group consisting of a perfluorinated ion exchange polymer on an inert support, a silane modified perfluorosulfonic acid, and a sulfated metal oxide; and B) a mobile acid component selected from the group consisting of chlorosulfonic acid, fluorosulfonic acid, a fluorinated monosulfonic acid of Formula 1a, a fluorinated sulfonimide of Formula 1b or 1c, a fluorinated disulfonic acid of Formula 2, and an adjunct acid mixture; wherein
Formula 1a is R
1
—CF
2
—SO
3
H,
Formula 1b is (R
1
—CF
2
—SO
2
)
2
NH,
Formula 1c is R
1
—CF
2
—SO
2
—NH—R
2
,
wherein each R
1
is independently Cl; F; H; branched or straight chain C
1
to C
10
alkyl optionally interrupted by oxygen atoms and optionally substituted with Cl or F; C
6
to C
12
aryl; or C
6
to C
12
aryl substituted with up to two groups selected from the group consisting of Cl, F, C
1
to C
10
alkyl, and C
1
to C
10
alkoxy;
each R
2
is independently branched or straight chain C
1
to C
10
alkyl optionally interrupted by oxygen atoms and optionally substituted with Cl or F; C
6
to C
12
aryl; or C
6
to C
12
aryl substituted with up to two groups selected from the group consisting of Cl, F, C
1
to C
10
alkyl, and C
1
to C
10
alkoxy; and
Formula 2 is HSO
3
—CF
2
—R
3
—CF
2
—SO
3
H
wherein R
3
is a divalent C
1
to C
10
alkylene optionally interrupted by oxygen atoms and optionally substituted with Cl or F; a C
6
to C
12
arylene; or C
6
to C
12
arylene substituted with up to two groups selected from the group consisting of Cl, F, C
1
to C
10
alkyl, and C
1
to C
10
alkoxy.
The present invention further comprises an improved alkylation process wherein the improvement comprises reacting an olefin with an alkane in the presence of a catalyst as described above.
The present invention further comprises an improved process for isomerization of at least one alkene wherein the improvement comprises conducting the isomerization in the presence of a catalyst as described above.
The present invention further comprises an improved process for oligomerization of an olefin wherein the improvement comprises conducting the oligomerization in the presence of a catalyst as described above.
DETAILED DESCRIPTION
The present invention is directed toward an improved catalyst that comprises a new combination of a fixed solid strong acid (hereinafter the “stationary acid”, “stationary acid component”, “heterogeneous acid” or “heterogeneous acid component”) and a mobile strong acid (hereinafter the “mobile acid”, “mobile acid component”, “homogeneous acid” or “homogeneous acid component”), and the use of the catalyst in alkylation, oligomerization, and isomerization processes. The catalyst of this invention substantially reduces the concentration of mobile acid required in the stationary acid component, thus minimizing the amount of eluted mobile acid requiring recovery and recycle.
Specifically, the stationary acid component of this invention comprises (a) a highly fluorinated polymeric sulfonic acid fixed on or entrapped within a porous silica or metal oxide support, (b) a silane-modified perfluorosulfonic acid on silica or metal salts, or (c) a sulfated metal oxide.
In the first embodiment, the stationary acid is a perfluorinated ion-exchange polymer containing pendant sulfonic acid, groups dispersed and entrapped within a silica or metal oxide support. Examples of such stationary acid components are a solid acid component such as the NAFION perfluorinated ion-exchange polymer in a silica nanocomposite, as described by Harmer and Sun in U.S. Pat. No. 5,824,622, or a perfluorosulfonic acid grafted on silica as described by Harmer et al. in U.S. Pat. No. 5,958,822 in which the graft is
HO
3
S—(CF
2
)
2
—O—(CF
2
)
2
—CH
2
)
3
—Si—[—O—]
3
—{silica}.
Perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid, carboxylic acid, or sulfonic acid and carboxylic acid groups used in the present invention are well known compounds. See, for example, Waller et al., Chemtech, July 1987, pp. 438-441, and references therein, and U.S. Pat. Nos. 5,094,995 and 5,824,622. Perfluorinated ion-exchange polymers (PFIEP) containing pendant carboxylic acid groups also have been described in U.S. Pat. No. 3,506,635. Polymers discussed by J. D. Weaver et al., in Catalysis Today, 14 (1992) 195-210, are also useful in the present invention. Polymers that are suitable for use in the present invention have structures that include a substantially fluorinated carbon chain that may have attached to it side chains that are substantially fluorinated. In addition, these polymers contain sulfonic acid groups or derivatives of sulfonic acid groups, carboxylic acid groups or derivatives of carboxylic acid groups and/or mixtures of these groups. F

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