JP2009062373A - Method for preventing polymerization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing polymerization of an unsaturated compound such as acrylamide in a stagnation part of a process liquid in an apparatus, in a production process of the unsaturated compound. <P>SOLUTION: The method for preventing polymerization of a 3-20C amide compound in a process for producing the compound is provided. The method for preventing polymerization of the 3-20C amide compound comprises compulsive moving of the process liquid stagnating inside the apparatus used in the production process from the place of stagnation by completely discharging the process liquid remaining in a liquid pool inside of the apparatus used in the production process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to stabilization of monomers having an unsaturated bond, particularly amide compounds such as acrylamide and methacrylamide. Amide compounds such as acrylamide are useful as raw materials for polymers having many uses such as flocculants, thickeners, petroleum recovery agents, paper strength enhancers in the paper industry, and papermaking thickeners.

  Amide compounds such as acrylamide include sulfuric acid hydrolysis method that includes heating nitrile compound such as acrylonitrile with sulfuric acid and water to obtain acrylamide sulfate, and presence of nitrile compound as catalyst (metal copper, copper oxide, copper salt, etc.) It is industrially produced by a method of producing a corresponding amide compound by hydration under the method, a method of producing acrylamide by hydrating a nitrile compound with a nitrile hydratase derived from a microorganism.

  Amide compounds such as acrylamide are extremely easily polymerized, and the polymerization proceeds in each step of each production method or when crystals and aqueous products are stored and stored, resulting in deterioration of quality and collection of amide compounds. This causes problems such as a decrease in rate, obstructing the flow of liquid in the apparatus and piping, and poor heat conduction.

For this reason, various compounds have been proposed as polymerization inhibitors for acrylamide.
For example, Japanese Examined Patent Publication No. 39-10109 describes a method for inhibiting polymerization by allowing a compound belonging to the group consisting of thiourea, rhodaammon, nitrobenzol, O-tolidine, phenothiazine and nitroso R salt to coexist with acrylamide. Japanese Patent No. 2548051 describes a method for stabilizing an aqueous acrylamide solution in which a water-soluble monocarboxylate having 2 or more carbon atoms is added.

  However, these polymerization prevention methods mainly improve the stability of the product, and are not necessarily effective for general-purpose polymerization prevention of process liquids in manufacturing processes that contain different impurities depending on the process and have different conditions. I can't say there is.

  Japanese Patent Publication No. 49-16845 discloses that the wall surface of the gas phase inside the apparatus used in the acrylamide manufacturing process is coated with a synthetic resin material to prevent the polymerization of acrylamide that tends to occur on the wall surface of the gas phase. Is described.

By the way, in a pipe for transferring a process liquid containing acrylamide, a polymer is hardly generated when the process liquid flows smoothly.
Further, in the reactor and the inside of the post-treatment tank, usually, the process liquid is smoothly stirred, introduced or discharged, so that a polymer is hardly generated.

  However, in the apparatus used in the manufacturing process, there is a place where the process liquid easily accumulates (liquid reservoir). Here, the process liquid is not substantially stirred, moved, or exchanged over a long period of time. A polymer is easily formed. These liquid pools cannot be eliminated by design ingenuity.

When the polymer is generated, the flow of the pipe is blocked or detached and mixed into the process liquid, which causes polymerization in the downstream tanks.
Japanese Examined Patent Publication No. 39-10109 Japanese Patent No. 2548051 Japanese Patent Publication No.49-16845

  An object of the present invention is to prevent polymerization of a compound in a process liquid pool in a process for producing a compound having an unsaturated bond.

That is, the present invention is the following polymerization prevention method.
A method for preventing the polymerization of a compound having 3 to 20 carbon atoms in the production process of the amide compound, and compulsorily ejecting the process liquid staying in the liquid pool inside the apparatus used in the production process from the staying position. A method for preventing polymerization of an amide compound having 3 to 20 carbon atoms, wherein

  According to the invention, it is possible to prevent polymerization during the production of monomers having an unsaturated bond, particularly amide compounds, and to construct a production process capable of stable operation.

  The polymerization prevention method of the present invention can be carried out in the production process of a compound having an unsaturated bond. Examples of the compound having an unsaturated bond include amide compounds, carboxylic acids, and carboxylic acid esters.

As the amide compound, an amide compound having about 3 to 20 carbon atoms is preferable, and examples thereof include unsaturated aliphatic amides such as acrylamide, methacrylamide, and crotonamide.
Examples of carboxylic acids include acrylic acid and methacrylic acid.

Examples of carboxylic acid esters include methyl acrylate and methyl methacrylate.
The method of the present invention is particularly preferably applied to a process for producing an amide compound.

  The amide compound of the present invention can be industrially produced by hydrating a corresponding nitrile compound by a method such as a sulfuric acid hydration method, an acetone cyanohydrin method, a copper catalyst method, an enzyme method or the like. Of these, the copper catalyst method and the enzyme method are preferred.

The copper catalyst method is a method for producing an amide compound by directly hydrating a nitrile compound in the presence of a copper catalyst such as metallic copper, reduced copper, Raney copper, etc., for example, as described in JP-B-52-33092 and the like. A method can be mentioned. The enzymatic method is a method for producing a corresponding amide compound by hydrating a nitrile by the action of an enzyme derived from a microorganism having an ability to hydrate a nitrile to produce a corresponding amide. For example, JP-A-11-89575 No., WO01 / 53253, and the like.

  The prevention of polymerization of the unsaturated compound of the present invention is that the process liquid containing the compound tends to accumulate, and the movement, stirring, and exchange of the accumulated liquid are not substantially performed for a long period of time, and the portion where polymerization is likely to occur (liquid accumulation). It is performed by forcibly moving the process liquid staying in the area from the staying place.

  Examples of devices that are liable to cause liquid pooling include pipes branched from the main pipe (sampling pipes, bypasses, etc.), valves, safety valves, flange joints, outlets provided in towers, heat exchangers A tube, a plate, a pump, etc. are mentioned.

  As an operation method for forcibly moving the staying liquid, when the staying liquid is discharged, for example, discharge by opening the latest valve, suction of the staying liquid by a pump, or the like may be performed. Further, the staying liquid may be diluted and replaced by passing a diluting liquid such as water through the staying part. These methods may be performed manually or automatically using a control device such as an automatic valve or a timer. The operation interval is arbitrary, but it is preferable to operate every 1 to 240 hours.

  A compound having an unsaturated bond such as the amide compound described above becomes more unstable under acidic conditions, and the possibility of occurrence of polymerization in the residence portion is increased. For example, the process liquid containing a compound such as acrylamide is purified by treatment with a strongly acidic ion exchange resin or activated carbon under acidity, and then transferred by piping.

  However, by carrying out the operation as described above and forcibly moving the staying liquid, polymerization does not easily occur in the liquid pool.

Example 1
Using the apparatus shown in FIG. 1, the acrylamide aqueous solution was treated.
The treatment tank 1 was charged with a 50% -acrylamide aqueous solution, then activated carbon was added under acidic conditions (pH 5), and the mixture was continuously stirred and mixed. The treatment liquid was transferred to the next step through the pipe 4. At that time, sampling was performed every 8 hours using the sampling pipe 5 and the sampling valve 6 branched downward from the pipe 4 for transferring the processing liquid, and the staying liquid was discharged.
As a result, no polymer was formed in the sampling pipe and the valve even after 2 weeks from the start of operation.

(Reference Example 1)
The operation was carried out using the same apparatus as in Example 1. Instead of sampling every 8 hours, water was injected from the valve 10 every 8 hours to wash the sampling pipe 5 and the valve 6.
As a result, no polymer was formed in the sampling pipe and the valve even after 2 weeks from the start of operation.

(Comparative Reference Example 1)
The operation was performed using the same apparatus as in Example 1, but no sampling or water injection was performed.
As a result, it was confirmed that the sampling pipe 5 and the sampling valve 6 were blocked by the polymer after two weeks.

It is the schematic of the processing apparatus of acrylamide aqueous solution.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing tank 2 Stirring blade 3 Motor 4 Piping 5 Sampling piping 6 Sampling valve 7 Pump 8 Pump inlet valve 9 Stirring tank lower valve 10 Water injection valve

Claims (1)

  A method for preventing the polymerization of a compound having 3 to 20 carbon atoms in the production process of the amide compound, and compulsorily ejecting the process liquid staying in the liquid pool inside the apparatus used in the production process from the staying position. A method for preventing polymerization of an amide compound having 3 to 20 carbon atoms, wherein

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