Mineral oils: processes and products – Chemical conversion of hydrocarbons – With prevention or removal of deleterious carbon...
Reexamination Certificate
2000-04-18
2001-10-16
Yildirim, Bekir L. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
With prevention or removal of deleterious carbon...
C208S04800Q, C205S696000, C585S834000
Reexamination Certificate
active
06303019
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
The present invention relates to a process to reduce the fouling of equipment for processing petroleum feedstreams. In particular, the fouling is due to the presence of peroxides and hydroperoxides in the petroleum feedstream.
All crude oils contain wppm levels of peroxides and hydroperoxides that were formed by exposure of some crude components, e.g., olefins, conjugated dienes, hydrocarbons containing tertiary hydrogens, pyrroles and indoles, etc. to oxygen in the air. Oxygen, a biradical at room temperature, reacts with these components in minutes (conjugated dienes), to hours (olefins) to weeks (tertiary hydrogens). The presence of even sub-ppm levels of peroxides will lead to fouling of fractionators, heat exchangers, furnaces, etc., and other refinery equipment upon heating. Reaction of peroxides on heating (~100-200° C.) initiates molecular weight growth chemical reactions, such as oligomerizations, polymerizations in pure component feeds, inter- and intramolecular alkylation reactions, etc. For example, a peroxide formed from a conjugated diene can react with other conjugated dienes, with pyrroles, indoles, carbazoles, most phenols, naphthols, thiophenols, naphthalene thiols, etc. An indole peroxide can react with another indole, a conjugated diene, etc., along the path to molecular weight growth reactions. When a feed containing a peroxide is mixed with another feed containing, e.g., conjugated dienes, the molecular weight growth reaction can continue. When the level of molecular weight growth exceeds the solubility of the growth products in solution they precipitate out on metal and other surfaces and foul the surfaces forming coke (thermal coking). The oligomerization and polymerization reactions are chain reactions. So, one molecule of a peroxide can react with hundreds of molecules of olefins or conjugated dienes (of same or varying structure). Oligomerization vs alkylation reactions will depend on the relative concentrations of species in a feed (e.g., of conjugated dienes vs. aromatics, especially 2
+
ring aromatics, and phenols, thiophenols, etc.). When there are no peroxides in the feed, no chain reaction initiators, most of these molecular weight growth reactions will be inhibited.
SUMMARY OF THE INVENTION
The present invention is a process to reduce the fouling of equipment for processing petroleum feedstreams. The steps of the process include mixing the feedstream with an aqueous electrolyte forming an oil-in-water dispersion, passing the dispersion through an electrochemical cell, passing a low voltage current through the dispersion, and separating the phases of the dispersion. The oil phase can then be further processed with minimum fouling of the equipment. The water phase is recycled for dispersing fresh petroleum.
REFERENCES:
patent: 4654450 (1987-03-01), Miller
patent: 5529684 (1996-06-01), Greaney et al.
patent: 5817228 (1998-10-01), Greaney et al.
patent: 5879529 (1999-03-01), Greaney et al.
patent: 5965008 (1999-10-01), Greaney et al.
Greaney Mark A.
Phillips Glen E.
Siskin Michael
Exxon Research and Engineering Company
Hantman Ronald D.
Yildirim Bekir L.
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