Olefinic hydrocarbon separation process

Details Olefinic hydrocarbon separation process Olefinic hydrocarbon separation process

1999-09-28

2001-05-01

McAvoy, Ellen M. (Department: 1764)

Chemistry of hydrocarbon compounds

Purification, separation, or recovery

By contact with solid sorbent

C585S802000, C585S809000, C585S820000, C585S822000, C585S827000, C585S829000, C208S31000R

Reexamination Certificate

active

06225518

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a process for the adsorptive separation of hydrocarbons from a feed mixture comprising the hydrocarbons and a different type of hydrocarbons such as the separation of olefins from paraffins. The invention more specifically relates to a method for the regeneration of a molecular sieve used either as a guard bed or as the main adsorbent in such a process.
RELATED ART
Molecular sieves are widely used to separate different structural types of hydrocarbons. For instance, it is known in the art that adsorptive separation using a molecular sieve adsorbent is an effective method to separate linear olefinic hydrocarbons from a feed mixture comprising the olefinic hydrocarbons and another class of hydrocarbons having a similar volatility such as paraffins of the same general molecular weight. This process is described in a paper entitled Olex:
A Process for Producing High Purity Olefins
presented by J. A. Johnson, S. Raghuram and P. R. Pujado at the August 1987 Summer national meeting of the American Institute of Chemical Engineers in Minneapolis, Minn. This paper describes a simulated moving bed (SMB) countercurrent adsorptive separation process for the separation of light straight chain olefins from similar paraffins.
U.S. Pat. No. 5,276,246 issued to B. McCulloch et al. describes a process for the adsorptive separation of normal olefins from a mixture of normal olefins and branched chain olefins using a low acidity silica molecular sieve such as a silicalite or ZSM molecular sieve.
U.S. Pat. No. 5,292,990 issued to E. Kantner et al. describes an adsorptive separation process for the recovery of linear olefins or paraffins from a mixture which also contains branched aliphatic hydrocarbons. The process employs an adsorbent comprising a low acidity high silica to alumina ratio zeolite. U.S. Pat. No. 5,300,715 issued to B. V. Vora describes an overall process for the conversion of paraffins to olefins. The process includes dehydrogenation of the paraffins and adsorptive separation of the olefins from a paraffin/olefin mixture recovered from the effluent of the dehydrogenation zone. The patent describes a zone used to selectively remove aromatic hydrocarbons from the paraffin/olefin mixture to prevent the aromatic hydrocarbons from deactivating a molecular sieve used in an adsorptive separation of the paraffin/olefin mixture. The removal of the aromatics also aids the performance of the dehydrogenation zone of the process. The aromatics removal zone is taught as possibly containing a molecular sieve, which is regenerated as needed.
BRIEF SUMMARY OF THE INVENTION
The invention is a process for the adsorptive separation of olefinic hydrocarbons from other hydrocarbons characterized in that a molecular sieve used in the process is regenerated in a novel multistep procedure which comprises purging the feed stream from the molecular sieve, contacting the molecular sieve with alkaline water under conditions effective to remove adsorbent poisons such as aromatic hydrocarbons from the molecular sieve, and removing water from the molecular sieve by contacting the molecular sieve with a vapor comprising a superheated C
2
to C
9
hydrocarbon. Preferably the adsorbent poisons are removed using liquid phase alkaline water containing sodium chloride.


REFERENCES:
patent: 3878128 (1975-04-01), Rosback
patent: 3888939 (1975-06-01), Rosback
patent: 3929669 (1975-12-01), Rosback et al.
patent: 4473657 (1984-09-01), Tse et al.
patent: 5276246 (1994-01-01), McCulloch et al.
patent: 5292990 (1994-03-01), Kantner et al.
patent: 5300715 (1994-04-01), Vora
patent: 6106702 (2000-08-01), Sohn et al.
“Olex: A Process for Producing High Purity Olefins,” by J.A. Johnson, S. Raghuram and P.R. Pujado, presented at the American Institute of Chemical Engineers, Aug. 16-19, 1987.

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