JPH05156233A - Agent for preventing staining of distillation tower in ethylene-producing facility - Google Patents

Abstract

PURPOSE:To provide a stain-preventing agent containing a specific nitrosophenol compound as an active ingredient, preventing the production of stain-forming polymers in the distillation tower of an ethylene-producing facility when applied to the distillation tower, permitting the smooth continuous operation of the distillation tower without requiring the cleansing of the tower, and effective for a long period. CONSTITUTION:A stain-preventing agent contains a nitrosophenol compound of the formula (R is H, 1-7C alkyl) as an active ingredient. The compound is preferably p-nitrosophenol, 4-nitroso-m-cresol, etc., and added to a naphtha- cracked gas fraction in an amount of 10ppb-500ppm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel soil polymerization inhibitor for a distillation tower of an ethylene production apparatus. More specifically, the present invention relates to an antifouling agent having a long-term effect in order to smoothly realize continuous operation of an ethylene production apparatus.

[0002]

2. Description of the Related Art Generally, in a purification separation step of an ethylene production apparatus, as shown in FIG.
There are deethanizer tower, ethylene tower, depropanizer tower, propylene tower, debutane tower, depentane tower, rerun tower, etc., but during operation, the inner surface of the distillation tower becomes dirty and the thermal efficiency deteriorates. The distillation column may be blocked. In order to prevent this, the bottom surface of the distillation column is made to have a smooth surface finish, and a polymerization inhibitor, an antioxidant, a dispersant or the like is used as an antifouling agent. Conventionally, as such an antifouling agent, a polymerization inhibitor such as p-t-butylcatechol, N, N-p-phenylenediamine, a dispersant such as an alkenylsuccinimide, a styrene-maleic acid copolymer, and these, Was used. Usually, large equipment such as ethylene production equipment is continuously operated for a long period of time because fixed expenses and operating expenses (shutdown and start-up) are enormous if the operation is stopped due to periodic repairs in a short period. Regular repair once a year (shutdown maintenance)
At, we will perform maintenance repairs including cleaning of the equipment. However, since the conventional antifouling agents that have been conventionally used are insufficient in the antifouling ability of the distillation column for ethylene production equipment (which correlates with the antipolymerization ability), the thermal efficiency may decrease or the bottom of the column may be clogged. Because there is
It is necessary to stop the distillation column in 6 to 12 months to wash dirt in the column. Therefore, the operation rate of the ethylene production apparatus is reduced, and one series of distillation columns, which are usually two series, are stopped and washed, resulting in a significant decrease in production efficiency.

[0003]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional antifouling agents and enables continuous distillation operation without washing during the continuous operation period of an ethylene plant. An object of the present invention is to provide an antifouling agent that improves the production efficiency of a plant.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies conducted by the present inventors to develop an antifouling agent having the above-mentioned preferable properties, the drawbacks of conventional antifouling agents are that they occur in the presence of oxygen. It was confirmed that it was effective in stabilizing oxy radicals, but was ineffective in stabilizing alkyl radicals generated in the anoxic state. Also,
In many distillation towers of ethylene equipment, after cooling the gas fraction to be purified by naphtha pyrolysis, it is the process of withdrawing from the top of each tower by sequential distillation from the one with the smallest carbon number, and the dirt is removed from each tower up to the debutane tower. Especially, a large amount is generated at the bottom, and the fractions having 4 or 5 carbon atoms always pass through the bottom of each distillation column. It was concluded that the main cause of bottom fouling was due to polymerization of butadiene or isoprene. Therefore, in the absence of oxygen of these dienes, as a result of studying what has a particularly effective polymerization termination ability, by adding a specific nitrosophenol-based compound into the distillation column,
It has been found that the object can be achieved, and the present invention has been completed based on this finding. That is, the present invention has the general formula

[0005]

[Chemical 2]

The present invention provides an antifouling agent for a distillation tower of an ethylene production apparatus, which comprises a nitrosophenol compound represented by the formula (wherein R is hydrogen or an alkyl group having 1 to 7 carbon atoms) as an active ingredient. Hereinafter, the present invention will be described in detail.
The general formula [1] used as the antifouling agent of the present invention
R in the nitrosophenol compound represented by
Hydrogen or an alkyl group having 1 or more carbon atoms, which may be linear, branched, or cyclic. Examples thereof include methyl group, ethyl group, n-propyl group, isopropyl group, n
-Butyl group, sec-butyl group, tert-butyl group,
Examples thereof include an isobutyl group, various pentyl groups, various hexyl groups, cyclohexyl groups, various heptyl groups, and the like. In the case of the compound of the present invention, the case where R is a methyl group is most effective and preferable.

Preferred specific examples of the nitrosophenol compound include p-nitrosophenol, 4-nitrosometacresol, 4-nitrosoorthocresol and 2
-Ethyl-4-nitrosophenol, 2-n-propyl-4-nitrosophenol, 2-isopropyl-4-nitrosophenol, 2-n-butyl-4-nitrosophenol, 2-sec-butyl-4-nitrosophenol, 2-tert-butyl-4-nitrosophenol,
2-isobutyl-4-nitrosophenol, 2-pentyl-4-nitrosophenol, 2-hexyl-4-nitrosophenol, 2-cyclohexyl-4-nitrosophenol, 2- (1,1-dimethylpropyl) -4-nitroso Phenol, 2- (2-methylpentyl) -4-nitrosophenol, 2- (2-ethylbutyl) -4-nitrosophenol, 2- (3,3-dimethylbutyl) -4-nitrosophenol, 2-n-heptyl -4-nitrosophenol etc. are mentioned. These nitrosophenol-based compounds may be used alone or in combination of two or more, and may be a conventionally known polymerization inhibitor, if desired, within a range not impairing the object of the present invention.
For example, p-tert-butylcatechol may be used in combination with 2,4-dinitrophenol. The present invention is characterized in that it strictly selects the one having the best polymerization inhibition effect on dienes under the conditions of the above-mentioned distillation column, and the difference in the polymerization inhibition effect under the condition of a normal period allows at least long-term operation. From a gender perspective, it makes a big difference.

When using the antifouling agent of the present invention,
10 ppb to 5000 ppm of the nitrosophenol-based compound of the present invention may be added to the fraction obtained by cooling the naphtha decomposition gas. The antifouling agent of the present invention contains p-nitrosophenols alone or in a solution such as a saturated hydrocarbon solvent,
For example, it can be added in the form of a solution of 0.1% by weight or more in pentane, hexane, heptane or the like. If the antifouling agent of the present invention is added to the first fraction of a column group in which a problem of fouling occurs, the antifouling agent sequentially flows to the bottom of each distillation column, which is the most fouled in the purification and separation process of the ethylene unit, and fouls. Exerts a preventive effect. Moreover, in the latter half of the distillation step, the concentration of the diene compound, which is the cause of the stain, increases, but as this concentration increases, the concentration in the fraction of the stain inhibitor of the present invention is also concentrated, and the stain prevention effect also increases. Therefore, it is preferable.

[0009]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 and Comparative Example 1 A 200 ml autoclave made of stainless steel was mixed with a 1 wt% hexane solution of each antifouling agent shown in the left column of Table 1 so that the amount of the net antifouling agent was 100 g. And the autoclave was sealed, and nitrogen gas filling and vacuum purging were repeated 5 times to make the interior of the autoclave oxygen-free. 100 g of a distillate collected from the bottom of the depropanizer of the ethylene production apparatus was put into an autoclave under a nitrogen stream and heated at 105 ° C. for 3 hours while stirring. After rapidly cooling the autoclave, the contents were taken out into a beaker, the autoclave was washed with 20 ml of hexane, and the washing liquid was taken into the above beaker. This liquid was completely removed of low-boiling components with a rotary evaporator, the residue was collected in a weighing bottle, dried at 100 ° C. for 2 hours, and weighed. The results are shown in Table 1.

[0010]

[Table 1]

Example 2 and Comparative Example 2 With respect to the antifouling agent in the left column of Table 2, the same operation as in Example 1 and Comparative Example 1 was performed except that the heat treatment temperature was changed to 120 ° C. The results shown in Table 2 were obtained.

[0012]

[Table 2]

[0013]

INDUSTRIAL APPLICABILITY The antifouling agent of the present invention has a very excellent polymerization inhibiting effect on dienes in the absence of oxygen and has a remarkable antifouling effect in the distillation step of an ethylene production apparatus. Since the efficiency is improved and energy is saved, the operation for cleaning the distillation column can be continuously operated without stopping the operation of all ethylene equipment (SDM), so that the production efficiency of the ethylene production equipment can be improved. There is an advantage that can be improved. When the antifouling agent of the present invention is applied to the distillation of an ethylene device,
If it is added to the fraction of the column group in which the problem of fouling occurs, the concentration will gradually increase, and there is an advantage that it can favorably cope with the increase in the concentration of dienes, which is the main cause of fouling.

[0014]

[Brief description of drawings]

FIG. 1 is a flow sheet diagram of an ethylene production apparatus using the stain preventive agent of the present invention.

[Procedure amendment]

[Submission date] March 3, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Generally, in a purification separation step of an ethylene production apparatus, as shown in FIG.
There are deethanizer tower, ethylene tower, depropanizer tower, propylene tower, debutane tower, depentane tower, rerun tower, etc., but during operation, the inner surface of the distillation tower becomes dirty and the thermal efficiency deteriorates. The distillation column may be blocked. In order to prevent this, the bottom surface of the distillation column is made to have a smooth surface finish, and a polymerization inhibitor, an antioxidant, a dispersant or the like is used as an antifouling agent. Conventionally, as such an antifouling agent, a polymerization inhibitor such as pt-butylcatechol, N, N-p-phenylenediamine, a dispersant such as an alkenylsuccinimide, a styrene-maleic acid copolymer, and these Was used. Usually, large equipment such as ethylene production equipment is continuously operated for a long period of time because fixed expenses and operating expenses (shutdown and start-up) are enormous if the operation is stopped due to periodic repairs in a short period. Regular repair once a year (shutdown maintenance)
At, we will perform maintenance repairs including cleaning of the equipment. However, since the conventional antifouling agents that have been conventionally used are insufficient in the antifouling ability of the distillation column for ethylene production equipment (which correlates with the antipolymerization ability), the thermal efficiency may decrease or the bottom of the column may be clogged. Because there is
In 6 to 12 months, it becomes necessary to switch to a spare reboiler or a distillation column to wash the dirt in the column. This is a factor that hinders the stable operation of the ethylene production equipment, and in the worst case, the production efficiency is lowered and the equipment is stopped.

Claims (1)

[Claims] 1. A general formula: An ethylene production apparatus distillation tower antifouling agent comprising a nitrosophenol compound represented by the formula (wherein R is hydrogen or an alkyl group having 1 to 7 carbon atoms) as an active ingredient.