Process for alkylation of isoparaffin with olefin

Details Process for alkylation of isoparaffin with olefin Process for alkylation of isoparaffin with olefin

2000-07-20

2002-12-10

Dang, Thuan D. (Department: 1764)

Chemistry of hydrocarbon compounds

Saturated compound synthesis

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

C585S704000, C585S721000, C585S722000, C585S726000, C585S730000

Reexamination Certificate

active

06492571

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for alkylation of an isoparaffin with an olefin, especially alkylation of isobutane with butene over the solid acid catalysts.
BACKGROUND OF THE INVENTION
In petroleum-chemical industry, as well known in the art, concentrated sulfuric acid and hydrofluoric acid catalysts are widely used in the process of isoparaffin-olefin alkylation, especially in alkylation of isobutane with butene, in order to produce higher molecular weight alkylates with high octane rating, as valuable gasoline blending components. However, both sulfuric acid and hydrofluoric acid share inherent drawbacks including equipment corrosion problem, serious environment and safety concerns. A lot of efforts have been directed to developing solid acid alkylation process to substitute for sulfuric acid or hydrofluoric acid processes.
In the past, new solid acid catalysts for the above alkylation process have been widely investigated and reported. For example, JP 01, 245, 853, U.S. Pat. Nos. 3,962,133 and 4,116,880, GB 1,432,720 and GB 1,389,237, etc. disclose SO
4
2−
enhanced super acid catalysts; U.S. Pat. Nos. 5,220,095, 5,731,256, 5,489,729, 5,364,976, 5,288,685 and EP 0,714,871A, etc. disclose CF
3
SO
3
H/silica catalysts; U.S. Pat. Nos. 5,391,527, and 5,739,074, etc. disclose Pt—AlCl
3
—KCl/Al
2
O
3
catalysts; U.S. Pat. Nos. 5,157,196, 5,190,904, 5,346,676, 5,221,777, 5,120,897, 5,245,101, 5,012,033, 5,157,197, CN 1,062,307A and WO 95,126,815, etc. disclose Lewis acid catalysts, such as SbF
5
, BF
3
and AlCl
3
; CN1, 184,797A, U.S. Pat. Nos. 5,324,881 and 5,475,178, etc. disclose supported heteropoly acid catalysts; U.S. Pat. Nos. 3,917,738 and 4,384,161, etc. disclose molecular sieve catalysts.
The most serious problem existing in the solid acid alkylation process is that the catalysts deactivate very quickly during the reaction. For example, the deactivation of some molecular sieve catalysts and SO
4
2−
/oxide catalysts occurs very quickly, in a few hours or even less than an hour, and the activity and selectivity of catalysts reduce dramatically resulting in the decline in the octane number of alkylate. Therefore, the regeneration of the solid acid alkylation catalysts has become a problem demanding prompt solution in the development of the solid acid alkylation process.
Presently, some kinds of hydrocarbon conversion reaction using solid acid catalysts, such as alkylation, isomerization, oligomerization and hydro-isomerization, are carried out at lower temperatures, wherein the macromolecular paraffins or olefins deposited on the surface of catalysts due to certain the side reactions, such as polymerization of olefin and hydride transference. These heavy hydrocarbons are organic compounds with a C/H ratio of less than 1, known as coke precursors, which are different from those coke substances with a C/H ratio of more than 1 originating in the reactions of hydrocarbon conversion at higher temperature, such as catalytic reforming and fluid catalytic cracking.
U.S. Pat. No. 5,365,010 discloses a process for regeneration of solid acid alkylation catalysts by calcination at high temperatures. In this process, Lewis acid catalysts, especially the BF
3
supported on alumina (BF
3
/AI
2
O
3
), are calcinated at 600° C. in order to burn out the heavy hydrocarbons deposited on the surface of the catalysts. High temperature regeneration is only applicable to the catalysts having good high temperature stability.
U.S. Pat. No. 5,326,923 and CN 1,076,386A disclose a process for regeneration of hydrocarbon conversion catalysts comprising contacting supported Lewis acid catalysts with solvent SO
2
in order to remove the reaction deposits from the surface of the catalysts, and to reactivate the catalysts.
JP 8-281,118 discloses a method for regeneration of solid heteropoly acid catalysts, comprising extracting the solid heteropoly acid or salt alkylation catalysts outside the reactor at normal temperature and pressure with polar or non-polar solvents in order to reactivate the catalyst partly. The non-polar solvents of C
4
-C
10
saturated fatty hydrocarbons are stated in the claims, but only polar solvents are used in the examples.
U.S. Pat. No. 3,855,343 discloses an isoparaffin-olefin alkylation process carried out in a slurry-phase reactor, comprising contacting isoparaffin with olefin in the presence of a BF
3
-containing cation-exchange resin catalyst and regenerating the catalyst by extraction with polar solvents.
U.S. Pat. No. 5,489,732 discloses a moving-bed alkylation process in which the catalysts are regenerated by the following method: dividing the exhausted catalyst equally into two parts, regenerating one part of the catalysts with the liquid-phase isoparaffin feedstock containing dissolved H
2
and regenerating the other part of the catalysts with H
2
at high temperature, then combining the two parts of used catalysts and separating hydrogen out, then mixing with the feedstock and recycling into the reactor for alkylation.
U.S. Pat. No. 5,523,503 discloses a solid acid catalyst alkylation process using the cocurrent simulated moving-bed. The process is carried out in several beds divided into reaction zone and regeneration zone; in which the position of reaction zone and regeneration zone is changed by controlling the inlet points of the feedstocks and regeneration stream, thus the purpose of continuous reaction-and-regeneration is realized by the cycle of such switching-over. Wherein the feedstock in reaction zone passes through at least two catalyst beds, that is, the reaction effluent containing unreacted feedstock and products from the first reaction bed enters the second bed, or then enters the third bed. The solvent for regeneration of the catalyst is the liquid-phase isoparaffin feedstock containing dissolved H
2
. In the process hydrogen needs to be separated. Moreover, there is at least one bed undergoing regeneration at any one time.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an isoparaffin-olefin alkylation process to produce alkylated oils with high octane number, wherein the continuous alkylation reaction can be realized and at the same time the catalyst can be regenerated effectively to resume its alkylation activity and selectivity by a simple operational process without a regeneration zone undergoing regeneration at any one time.
The present invention provides a process for alkylation of isoparaffin with olefin using a solid acid catalyst, comprising:
Feeding an alkylation feedstock comprising isoparaffin and C
3
~C
6
mono-olefins into at least two parallel reactors the reaction under conditions for alkylation in presence of a solid acid catalyst;
When the selectivity and activity of the catalyst in one or more of said reactors or the octane number of alkylate from the bottom descends due to macromolecular hydrocarbons deposited on the surface of the catalyst, switching said one or more reactors over to feed a solvent stream for regeneration of the catalyst to carry out the solvent extraction for regeneration of the catalyst in situ, and after the regeneration transferring the used solvent stream to the solvent-recovery unit for reuse;
Switching said one or more reactors over after the completion of the regeneration to feed said alkylation feedstock to continue the alkylation again;
Wherein the alkylation is being carried out in at least one of all reactors during the process.
DETAILED DESCRIPTION OF THE INVENTION
The invention provides a process for alkylation of isoparaffin with olefin over a solid acid catalyst. In the present process, the catalyst is regenerated in situ with a solvent, and at least two parallel reactors are used at the same time, each of which is charged with said catalyst and can be used for alkylation. Either the alkylation feedstock or the solvent for regeneration can pass through the inlet of each reactor by switching over the valves, and either the reaction effluent or the used solvent can pass through the outlet of each reactor to the fractionating t

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