Chemistry of hydrocarbon compounds – Product blend – e.g. – composition – etc. – or blending process... – With nonhydrocarbon additive
Reexamination Certificate
1998-11-23
2002-01-08
Mulcahy, Peter D. (Department: 1713)
Chemistry of hydrocarbon compounds
Product blend, e.g., composition, etc., or blending process...
With nonhydrocarbon additive
C526S236000
Reexamination Certificate
active
06337426
ABSTRACT:
The present invention pertains to novel methods and compositions for inhibiting polymerization in industrial plant streams which contain reactive light olefins, thereby preventing fouling of processing equipment and of product in storage tanks. Particularly, the invention pertains to the use of a combination of phenylenediamines and nitroxides to prevent undesired polymerization in reactive light olefins.
BACKGROUND OF THE INVENTION
Industrial plant streams and processes which contain reactive light olefins are plagued with fouling problems due to unwanted polymerization. Examples of such plant streams and processes are hydrocarbon cracking processes in which light olefins are generated, industrial distillation processes of light olefin monomers, hydrogenation of light olefins and acetylenic compounds, and the like. Particular examples of such plant streams are depropanizer and debutanizer bottoms, light olefins typically generated in ethylene crackers. Such processes employ elevated temperatures which results in unwanted polymerization of the light olefin monomers. This unwanted polymerization results in the formation of deposits, or fouling, in distillation columns and other equipment such as heat transfer surfaces, reactor beds, reboilers, process lines, compressors, etc.
Fouling of the equipment or product during the stages of handling, processing, purification, and storage results in significant economic loss. Formation of deposits on heat transfer surfaces reduces process efficiency, and the unwanted polymerization also results in a loss of the desired product. Eventually the process must be stopped to clean the affected equipment.
To minimize fouling, commercial antifoulants are often added at 1-100 ppm levels at some point in the industrial process. Many classes of antifoulants are known, including phenylenediamines, hydroxylamines, nitroxides, and hindered phenols. However, fouling problems in reactive light olefin plant streams are not completely solved and industry continues to search for better solutions as well as for more cost effective ways to attack this problem.
Unexpectedly, the combination of phenylenediamines with nitroxides is found to be synergistic in its ability to prevent fouling in reactive light olefin streams. The activity of this combination exceeds that of state-of-the-art antifoulants. The state-of-the-art is described in the patents below, the relevant parts of which are incorporated herein by reference.
U.S. Pat. No. 4,670,131 discusses the use of any stable free radical to prevent polymerization in unsaturated organic feed streams. Specifically claimed is the prevention of fouling in olefinic feed streams by incorporation of a nitroxide at less than 700 ppb.
U.S. Pat. No. 5,282,957 discloses the use of hydroxyalkylhydroxylamine compounds to inhibit polymerization of hydrocarbon fluids containing dissolved oxygen.
U.S. Pat. No. 5,396,005 discloses the combination of a methoxyphenol, either eugenol or 2-t-butytl-4-hydroxyanisole, with a phenylenediamine to prevent polymerization of ethylenically unsaturated monomers.
U.S. Pat. No. 5,416,258 discusses the method of inhibiting polymerization of a butadiene-containing stream by the addition of a combination of a phenylenediamine and a hydroxytoluene compound.
The following patents teach the use of nitroxides as inhibitors in combination with coadditives to prevent polymerization in various systems. The coadditives include phenylenediamines.
JP 93/320217 discloses the use of nitroxides with coadditives in methacrylic acid. The coadditives are phenothiazines, aromatic amines, and phenols.
DE 19609312 A1 and related WO 97/32833 disclose the use of nitroxides as inhibitors for monomers in which the vinyl group is attached to a heteroatom. The compositions may additionally contain one or more costabilizers of the group of phenothiazines, quinones, hydroquinones and their ethers, hydroxylamines or phenylenediamines.
U.S. Pat. No. 5,711,767 discloses the use of nitroxides to prevent oxidative degradation and gum or deposit formation in gasoline. A costabilizer may also be employed which is selected from the group consisting of an aromatic amine, a phenolic antioxidant or a mixture of an aromatic amine and a phenolic antioxidant.
The synergistic activity of the combination of phenylenediamines with nitroxides towards preventing fouling in reactive light olefins is unknown. The superior performance of this particular combination to prevent premature polymerization in light olefins is not disclosed or suggested in the prior art.
DETAILED DESCRIPTION OF THE INVENTION
The present invention pertains to novel methods and compositions for preventing premature polymerization in industrial plant streams and processes containing reactive light olefins. The use of these novel methods and compositions prevents fouling of equipment and product during handling, processing, purification, and storage.
The novel compositions of this invention, stabilized against premature polymerization, comprise
a) a light olefin monomer, and
an effective polymerization inhibiting amount of
b) at least one phenylenediarnine of the formula I
wherein R
1
, R
2
, and R
3
are the same or different and are hydrogen, straight or branched chain alkyl of 1 to 20 carbon atoms, straight or branched chain alkyl of 1 to 20 carbon atoms which is substituted by one to three aryl groups, aryl of 6 to 12 carbon atoms, or aryl of 6 to 12 carbon atoms which is substituted by one to three alkyl groups of 1 to 6 carbon atoms; and
c) at least one nitroxide of the formula II
wherein R
4
and R
5
are independently alkyl of 1 to 4 carbon atoms or are together pentamethylene; and Z
1
and Z
2
are each methyl or Z
1
and Z
2
together form a linking moiety which may or may not contain heteroatoms or carbonyl groups and which additionally may be substituted by hydroxy, cyanohydrin, amino, alkoxy, amido, ketal, carboxy, hydantoin, carbamate, or a urethane group.
The novel method of this invention comprises
adding to a reactive light olefin an effective polymerization inhibiting amount of
b) at least one phenylenediamine of the formula I
wherein R
1
, R
2
, and R
3
are as defined previously; and
c) at least one nitroxide of the formula II
wherein R
4
, R
5
, Z
1
, and Z
2
are as defined previously.
The phenylenediamines of this invention have at least one N—H group. Preferred examples of phenylenediamines of this invention include N-phenyl-N′-methyl-1,4-phenylediamine, N-phenyl-N′-ethyl-1,4-phenylediamine, N-phenyl-N′-n-propyl-1,4-phenylediamine, N-phenyl-N′-isopropyl-1,4-phenylediamine, N-phenyl-N′-n-butyl-1,4-phenylediamine, N-phenyl-N′-iso-butyl-1,4-phenylediamine, N-phenyl-N′-sec-butyl-1,4-phenylediamine, N-phenyl-N′-t-butyl-1,4-phenylediamine, N-phenyl-N′-n-pentyl-1,4-phenylediamine, N-phenyl-N′-n-hexyl-1,4-phenylediamine, N-phenyl-N′-(1-methylhexyl)-1,4-phenylediamine, N-phenyl-N′-(1,3-dimethylbutyl)-1,4-phenylediamine, N-phenyl-N′-(1,4-dimethylpentyl)-1,4-phenylediamine, N-phenyl-N′,N′-dimethyl-1,4-phenylenediamine, N-phenyl-N′,N′-diethyl-1,4-phenylenediamine, N-phenyl-N′,N′-di-n-butyl-1,4-phenylenediamine, N-phenyl-N′,N′-di-sec-butyl-1,4-phenylenediamine, N-phenyl-N′-methyl-N′-ethyl-1,4-phenylenediamine, N,N′-dimethyl-1,4-phenylenediamine, N,N′-diethyl-1,4-phenylenediamine, N,N′-di-isopropyl-1,4-phenylenediamine, N,N′-di-iso-butyl-1,4-phenylenediamine, N,N′-di-sec-butyl-1,4-phenylenediamine, N,N′-bis(1,4-dimethylpentyl)-1,4-phenylenediamine, N,N′-bis(1,3-dimethylbutyl)-1,4-phenylenediamine, N,N′-diphenyl-1,4-phenylenediamine, N,N,N′-trimethyl-1,4-phenylenediamine, and N,N,N′-triethyl-1,4-phenylenediamine.
Particularly preferred examples of phenylenediamines of this invention include N,N′-di-sec-butyl-1,4-phenylenediamine, N,N′-bis(1,4-dimethylpentyl)-1,4-phenylenediamine, N,N′-di-iso-butyl-1,4-phenylenediamine, N,N′-bis(1,3-dimethy
Breininger Thomas M.
Martin Michael B.
Mulcahy Peter D.
Nalco/Exxon Energy Chemicals L.P.
LandOfFree
Antifoulant compositions and processes does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Antifoulant compositions and processes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Antifoulant compositions and processes will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2843419