JPH1143449A - Prevention of contamination in olefin production or purification process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing olefins, high in effect of preventing polymerization, excellent in effect of preventing contamination, and capable of operating continuously and stably for extended periods by reacting a stock oil incorporated with a piperidine-1-oxyl and N,N-di-substituted hydroxylamine. SOLUTION: This method gives olefins by reacting a stock oil incorporated with a combination of (A) at least one type of piperidine-1-oxyl compound shown by formula I (R<1> is a 1-3C alkyl; and R<2> is H or the like) (preferably 2,2,6,6-tetramethylpiperidine-1-oxyl or the like) or formula II (R<5> is a 1-3C alkyl) (preferably 2,2,6,6-tetramethyl-4-oxopiperidine-1oxylpiperidine-1-oxyl), preferably at 1 to 10 wt.ppm based on the stock oil, and (B) at least one type of N,N-di- substituted hydroxylamine (preferably N,Ndiethylhydroxylamine or the like), preferably at 1 to 10 wt.ppm based on the stock oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing fouling in an olefin production or refining step, and more particularly, the present invention prevents or suppresses the occurrence of fouling in an olefin production or refining step. And a method for smooth and easy continuous operation.

[0002]

2. Description of the Related Art Contamination in the process of producing or refining olefins includes the olefins in the process, especially the diene represented by butadiene, isoprene, cyclopentadiene and the like contained therein.
This is due to the fact that heat, a trace amount of oxygen or peroxide, metal ions, etc. act to promote radical polymerization and the polymer adheres to the inside of the apparatus. When these dirt accumulate and increase, the transfer of heat in the process is hindered, or the operation efficiency is deteriorated such as the flow of the process fluid is deteriorated, so that the normal operation becomes difficult, and the operation must be stopped urgently. It becomes a big problem in operation, such as not being able to obtain.

[0003] As a countermeasure, for example, phenols,
Hydroxylamines [see, for example, US Pat.
No. 7, specification (1984)], phenylenediamines,
Nitrosophenols (for example, see JP-A-5-15623)
No. 3) and a method using an antifouling agent such as piperidine-1-oxyl (Japanese Patent Publication No. 4-26639).

[0004]

However, phenols, hydroxylamines, nitrosophenols, phenylenediamines and the like are polymerization retarders and their actions are moderate, and a large amount is required to exhibit a sufficient stain-preventing effect. Must be used. Piperidine-1-oxyls have been proposed as an improvement, but they have the drawback that they are consumed by peroxides in the system and rapidly lose their effect, leaving a problem from the viewpoint of safe driving, and furthermore, the effect is not so good. Was expensive.

Therefore, the present invention overcomes the disadvantages of conventional antifouling agents in the production or purification process of olefins, has a high polymerization preventing effect, is excellent in antifouling effects, and enables long-term continuous stable operation. It is intended to provide a way.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have investigated the generation of soil in the olefin production or purification process in detail, and have conducted intensive studies to develop a preferable method for preventing soil. The present inventors have found that by applying a combination of oxyls and N, N-disubstituted hydroxylamines, it is possible to extremely effectively prevent contamination in the olefin production or purification step, and have accomplished the present invention.

That is, according to the first aspect of the present invention, in the olefin production or purification step, (A) the following general formula (I):
Wherein R ¹ is an alkyl group having 1 to 3 carbon atoms, R ² is H, O
An H group, an OR ³ group (R ³ is an alkyl group having 1 to ³ carbon atoms or a phenyl group) or a COOR ⁴ group (R ⁴ is H or an alkyl group having 1 to 3 carbon atoms)] and the following general formula (II) )
Wherein R ⁵ represents an alkyl group having 1 to 3 carbon atoms, and at least one of piperidine-1-oxyls represented by the formula:
(B) at least one of N, N-disubstituted hydroxylamines represented by the following general formula (III) (wherein R ⁶ represents an alkyl group having 1 to 18 carbon atoms, a benzyl group or a phenyl group)
A method for preventing fouling in an olefin production or purification step, characterized by adding an appropriate amount in combination with a seed.

[0008]

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[0009]

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[0010]

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[0011] The invention of claim 2 is the above-mentioned piperidine-1-.
Oxyls are 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-
Hydroxypiperidine-1-oxyl, 2,2,6,6
-Tetramethyl-4-oxopiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-methoxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-ethoxypiperidine-1 -Oxyl, 2,2
6,6-tetramethyl-4-phenoxypiperidine-1
-Oxyl and 2,2,6,6-tetramethyl-4-
At least one of hydrocarboxypiperidine-1-oxyl, and wherein the N, N-disubstituted hydroxylamine compound is N, N-diethylhydroxylamine, N, N-dibenzylhydroxylamine and N, N- 2. The method according to claim 1, which is at least one of diphenylhydroxylamine.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The piperidine-1-oxyl in the present invention is a compound represented by the aforementioned general formula (I) or (II). In the general formula (I), R ¹ has 1 to 3 carbon atoms.
, Specifically, a methyl group, an ethyl group, an n-propyl group, and an isopropyl group, preferably a methyl group. R ² is H, OH group, OR ³ group (R ³ has 1 to ³ carbon atoms)
And R ³ is specifically a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, or a COOR ⁴ group (R ⁴ is H or a carbon atom of 1).
To 3 alkyl groups, specifically, a methyl group, an ethyl group, an n-propyl group, and an isopropyl group).
Preferred specific compounds of the general formula (I) include, for example, 2,
2,6,6-tetramethylpiperidine-1-oxyl,
2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-
4-methoxypiperidine-1-oxyl, 2,2,6
6-tetramethyl-4-ethoxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-phenoxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-carboxypiperidine- 1-oxyl. In the general formula (II), R ⁵ is an alkyl group having 1 to 3 carbon atoms, specifically, a methyl group, an ethyl group, or a propyl group, and is preferably a methyl group. Preferred specific compounds of the general formula (II) include 2,2,6,6-tetramethyl-4-oxopiperidine-1oxylpiperidine-
1-oxyl. One of these piperidine-1-oxyls may be used alone, or two or more thereof may be used in combination.

The other N, N-disubstituted hydroxylamines in the present invention are compounds represented by the above general formula (III). In the general formula (III), R ⁶ has 1 to 1 carbon atoms.
An alkyl group of 18; a benzyl group or a phenyl group; specifically, an alkyl group having 1 to 18 carbon atoms of R ⁶ is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group; They are a sec-butyl group, a tert-butyl group, an n-hexyl group, an n-octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, a tetradecyl group, and an octadecyl group. Preferred specific compounds of the general formula (III) include N, N-diethylhydroxylamine, N, N-dibenzylhydroxylamine, N, N-
Diphenylhydroxylamine.

One of these N, N-disubstituted hydroxylamines may be used alone, or two or more of them may be used in combination.

In the present invention, both the piperidine-1-oxyl and the N, N-disubstituted hydroxylamine each independently function as a polymerization inhibitor.
In the present invention, piperidine-1-oxyls and N,
It is characterized in that it is used in combination with N-disubstituted hydroxylamines to exert a synergistic effect.

Although the mechanism of the synergistic effect of the piperidine-1-oxyls and the N, N-disubstituted hydroxylamine is not clear, the N, N-disubstituted hydroxylamine having a large polymerization delaying action and the peroxide-eliminating action having a large peroxide action. The combination of piperidine-1-oxyls produced a synergistically greater effect beyond simply the range of additivity. No substantial synergistic effect was found with piperidine-1-oxyls and other compounds such as phenols, nitrosophenols or phenylenediamines.

In order to expect a synergistic effect of piperidine-1-oxyl and N, N-disubstituted hydroxylamine, it is preferable that N, N-disubstituted hydroxylamine 1 to 10 parts by weight of piperidine-1-oxyl be used. It is 15 parts by weight, more preferably 5 to 10 parts by weight.

Piperidine-1 used for preventing contamination in the olefin production or purification process of the present invention.
-The amount of the oxyls added is 0.1-100
ppm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm, and the amount of the N, N-disubstituted hydroxylamine added is 0.1 to 100 p.
pm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm.

The olefin production or refining step of the present invention may be carried out specifically in a demethanizer tower, a deethane tower, an ethylene rectification tower, a depropane tower, a propylene rectification tower, a debutanizer, a depentane tower in the ethylene production step. Tower, reran tower,
Other processes such as a butadiene production process and an isoprene production process. The piperidine-1-oxyls and N, N-disubstituted hydroxylamines in the present invention are added to the upstream of a point where fouling is a problem in the process. These steps are usually carried out from a series of successive steps. If it is added to the first step in which the problem of contamination occurs, it flows sequentially to the bottom of the distillation column at the subsequent stage, and also acts as a contamination prevention in the subsequent stage. In particular, in a process of repeating distillation such as an ethylene production process, the concentration of a diene compound that greatly contributes to the generation of dirt increases as going to the subsequent stage,
At the same time, the piperidine-1-oxyls of the present invention and N, N-
Disubstituted hydroxylamines are also concentrated to a high concentration, which is advantageous because the effect of preventing contamination is increased.

The method of adding piperidine-1-oxyl and N, N-disubstituted hydroxyamine in the present invention is as follows.
Although not particularly limited, they can be dissolved individually in an organic solvent and added separately to the system, or both can be mixed and dissolved in the same organic solvent and added. As the solvent used, for example, toluene, xylene, hydrocarbon solvents such as ethylbenzene, ethanol, isopropanol, n-butanol, 2-ethylhexanol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, γ-butyrolactone, dioxane, methyl ethyl ketone, And dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, and the like. These organic solvents may use a mixed solvent in which two or more kinds are combined.For example, when a hydrocarbon-based solvent and an oxygen-containing solvent are used in combination, first dissolve in the oxygen-containing solvent and then add the hydrocarbon-based solvent thereto. Addition may result in a more uniform solution sooner. The concentration when dissolving is not particularly limited, but it is preferable to add it in a 0.1 to 50% by weight solution for convenience in use. The present invention does not limit the kind of the solvent used, the method of dissolution, the dissolution concentration, and the like.

In the present invention, a combination of a piperidine-1-oxyl and an N, N-disubstituted hydroxyamine is used. Other known polymerization inhibitors and antioxidants are used as long as the object of the present invention is not impaired. It does not impose any restrictions on the addition and use of a dispersant, a metal deactivator and the like.

[0023]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. [Example 1]

A 1% by weight xylene solution of piperidine-1-oxyls and N, N-disubstituted hydroxylamines as shown in Table 1 was placed in a stainless steel 100 L autoclave with respect to the olefins used in the test. And the autoclave was sealed. After the system was filled with nitrogen gas and purged under reduced pressure three times to remove oxygen in the system, 20 g of the bottom liquid of the depropanizer from the ethylene production apparatus [peroxide content 1 pp
m] was enclosed. After heating the autoclave at 100 ° C. for 3 hours, the autoclave was quenched, the content was taken out into a beaker, and 9 volumes of methanol was added. The precipitated polymer was subjected to suction filtration using a 1 μm membrane filter having a known weight, which was previously washed with methanol and dried at 105 ° C. for 2 hours, to obtain a polymer as a product on the filter. The filter was washed three times with methanol, dried at 105 ° C. for 2 hours, weighed, and the amount of polymer on the filter was determined from the value. Also, the polymer generation inhibition rate was determined by using the amount of polymer obtained by repeating the same operation without adding piperidine-1-oxyl and N, N-disubstituted hydroxylamine at all as a standard control. Table 1 collectively shows the results.

[0025]

[Table 1]

From the results shown in Table 1, piperidine-1-
It can be seen that the combined use of oxyls and N, N-disubstituted hydroxylamines is much more effective in suppressing polymer generation than the use of each alone. Further, the effect is even greater than conventionally used p-tert-butylcatechol and N, N-diisopropyl-p-phenylenediamine (alone).

[0027]

EFFECT OF THE INVENTION Piperidine-1-oxyls and N, N-
By using a combination of disubstituted hydroxylamines, the effect of suppressing the generation of polymer (antifouling effect) in the process of producing or purifying olefins is remarkably superior to that of using each of them alone. Can be performed smoothly.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C10G 9/12 C10G 9/12 29/20 29/20 (72) Inventor Norihiko Onishi Also known as 6-6-9 Hakuto, Yokkaichi City, Mie Prefecture (72) Inventor Motohiro Kawade Incorporated: Yokkaichi City, Mie Prefecture, aka 6-6-9 Hakuto Co., Ltd. Yokkaichi Research Center

Claims (2)

[Claims] 1. A olefins production or purification process, (A) the following general formula (I) [wherein, R ¹ is 1 to the number of carbon atoms
R ² is H, OH, OR ³ (R ³ is alkyl having 1 to ³ carbons or phenyl) or CO 2
An OR ⁴ group (R ⁴ represents H or an alkyl group having 1 to 3 carbon atoms)] and the following general formula (II) (wherein, R ⁵ represents 1 to 4 carbon atoms)
At least one of piperidine-1-oxyls represented by the following general formula (III):
[Wherein R ⁶ represents an alkyl group having 1 to 18 carbon atoms, a benzyl group or a phenyl group], and is added in an appropriate amount in combination with at least one of N, N-disubstituted hydroxylamines represented by the following formula: Method for preventing contamination in olefins production or purification process. Embedded image Embedded image Embedded image 2. The method of claim 2, wherein said piperidine-1-oxyl is 2,2.
2,6,6-tetramethylpiperidine-1-oxyl,
2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-
4-oxopiperidine-1-oxyl, 2,2,6,6
-Tetramethyl-4-methoxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-ethoxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-phenoxypiperidine-1 -Oxyl and 2,
At least one of 2,6,6-tetramethyl-4-hydrocarboxypiperidine-1-oxyl,
And the N, N-disubstituted hydroxylamine is N,
2. The method according to claim 1, wherein the method is at least one of N-diethylhydroxylamine, N, N-dibenzylhydroxylamine and N, N-diphenylhydroxylamine.