JP2003105361A - Gas hydrate formation control agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas hydrate formation control agent having the effect of promoting gas hydrate in its formation and/or stabilizing the thus formed gas hydrate, to provide a method of controlling its formation, a method for transporting the thus formed gas hydrate, and a method for storing the thus formed gas hydrate, and to provide a composition including gas hydrate. SOLUTION: This gas hydrate formation control agent consists of a gel-like polymer including hydrophilic monomer unit and/or amphipathic monomer unit. The 2nd objective method for controlling gas hydrate formation comprises putting the above agent in a system where gas hydrate is present or can be formed. The 3rd objective method for dispersing the above agent in water and/or a water-miscible solvent and adding it to gas hydrate, and the 4th objective method for transporting gas hydrate and the other objective method for storing gas hydrate, each using the 2nd objective method, are provided, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas hydrate such as methane hydrate, and more particularly, to a production control agent that contributes to promotion and / or stabilization of production of gas hydrate, production control method of gas hydrate, and transportation. A method, a storage method and a composition comprising a gas hydrate.

[0002]

2. Description of the Related Art Water molecules surround dissolved gas molecules by placing an aqueous medium in which various gas molecules such as hydrocarbons such as methane and ethane and carbon dioxide are dissolved under a specific temperature and pressure. It is known that ice-like crystals, that is, gas hydrates are produced.

On the other hand, LNG (liquefied natural gas) is usually used for transportation and storage of fuel gas, especially methane gas. However, this method is not suitable for LNG base construction and L
The cost of NG transport tanker construction is enormous, so it is suitable for large gas fields where long-term depreciation period can be expected, but it is not suitable for small gas fields, which hinders development of small gas fields. Has become.

Furthermore, when natural gas or the like is used in a moving object such as a vehicle, it is common to store the natural gas or the like in a high pressure tank. However, the method of storing using a high-pressure tank has a problem that there are many cases where a sufficient amount cannot be stored due to pressure limitation due to legal regulations, and a tank having high pressure resistance is required.

For these reasons, a technique for transporting or storing a gas for fuel containing natural gas or a gas capable of generating a gas hydrate such as carbon dioxide in the form of a gas hydrate is being developed.

[0006] For example, as a method for storing natural gas using gas hydrate, JP-A-4-316795 and JP-A-4-316797 disclose a gas hydrate formation promoting additive together with water in a natural gas storage tank. Describes a method of adding an aliphatic amine or the like. Further, JP-A-6-17069 and JP-A-9-4960.
Similarly, Japanese Patent Laid-Open No. 0-05819 discloses a method of adding a low molecular weight compound such as alcohols and ketones in order to accelerate the formation of hydrate. These methods have a function of promoting the production of gas hydrate by shifting the equilibrium production equilibrium condition to the high temperature and low pressure side, but generally it is necessary to add a large amount of additives,
Further, there is a problem that the effect of the generated gas hydrate on the stability is low. Furthermore, these methods also have a problem that the vapor pressure is low because the molecular weight of the additive is low, and the additive is easily mixed when the gas to be used is taken out from the gas hydrate.

Japanese Unexamined Patent Publication (Kokai) No. 10-216505 discloses a method in which a silicone resin-containing surfactant is added to water to grow a gas hydrate in a bubble-free state at a "gas-liquid (water in this case)" interface. Has been done. This technology focuses on the fact that gas hydrate formation occurs near the interface, and its purpose is to increase the contact efficiency between gas molecules and water by lowering the surface tension of water, thereby promoting the formation of gas hydrate. The effect of stabilizing the generated gas hydrate is low.

Japanese Unexamined Patent Publication No. 10-238695 discloses a technique relating to a small gas tank for a moving body using a gas hydrate. However, in order to continue to store the hydrate, the tank is cooled at 0 to 1 ° C. There is a problem that needs to be continued and requires extra energy.

[0009]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to produce a gas hydrate which has the effect of promoting production of the gas hydrate and / or stabilizing the produced gas hydrate. It is to provide a control agent. The present invention also provides a method for controlling the production of gas hydrate, a transportation method, a storage method, and a composition containing the gas hydrate.

[0010]

DISCLOSURE OF THE INVENTION The present inventors have prepared a gas hydrate by using at least a part of a conventional gas hydrate formation control agent consisting of a chain polymer alone as a gel polymer. The inventors have found that the controllability is remarkably improved and have reached the present invention.

That is, the present invention is a gas hydrate production control agent comprising a gelled polymer containing a hydrophilic monomer unit and / or an amphipathic monomer unit. The gelled polymer has a proportion of hydrophilic monomer units in all monomer units of 20 mol% or more and 100 mol% or less,
The proportion of amphipathic monomer units in all monomer units is 20 mol% or more and 100 mol% or less, and the total proportion of hydrophilic monomer units and amphiphilic monomer units in all monomer units is 20 mol% or more. It is preferably 100 mol% or less.

Further, the present invention provides a method for controlling production of gas hydrate, characterized in that these gas hydrate production control agents are present in a system in which gas hydrate is present or in a system capable of producing gas hydrate. Is. As a method of addition at that time, it is preferable to add the gas hydrate production control agent by dispersing it in water and / or a solvent miscible with water. Such a gas hydrate production control method is suitable for transportation of gas hydrate and storage of gas hydrate. When storing the gas hydrate, the gas hydrate should be stored at a pressure of 5 MPa or less and 0
It is preferable to hold at a temperature of -20 ° C.

Further, the present invention is a composition containing the gas hydrate production control agent of the present invention and a gas hydrate.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The gas hydrate production controlling agent of the present invention comprises a gelled polymer containing a hydrophilic monomer unit and / or an amphipathic monomer unit. What is a gel-like polymer? "New edition polymer dictionary, p.129, Asakura Shoten, 19
88 ”and a polymer having a three-dimensional network structure insoluble in a solvent and a swollen body thereof. The term "gas hydrate production control agent" is a general term for agents having a gas hydrate production promoting and / or stabilizing effect.

The gelled polymer contained in the gas hydrate production control agent of the present invention can be produced, for example, by the following method.

(1) One or more hydrophilic monomers (co)
Polymerize or copolymerize one or more hydrophilic monomers and one or more hydrophobic polymers.

(2) Copolymerize at least one hydrophilic monomer and at least one amphipathic monomer.

(3) (Co) polymerizing one or more amphipathic monomers, or copolymerizing one or more amphipathic monomers and hydrophobic monomers.

The gel-like polymer produced by the method (1) is preferably a copolymer containing a hydrophilic monomer unit and a hydrophobic monomer unit, but a polymer containing only a hydrophilic monomer unit and a hydrophobic monomer unit. It may be a mixture of polymers consisting of only. During (co) polymerization, the proportion of hydrophilic monomers in all monomers is 20 mol% or more 1
It is preferably less than 00 mol%. The higher the ratio of the hydrophilic monomer, the stronger the hydrophilicity of the gelled polymer obtained, and the more easily water molecules enter the gelled polymer. Therefore, when such a gel polymer is added to a system capable of generating gas hydrate, gas hydrate is generated from gas molecules taken into the gel and water molecules entering the gel by the Van der Waals force. Easier to form,
The stability of the system is improved. On the other hand, the lower the proportion of the hydrophilic monomer, the stronger the force of attracting the hydrophobic gas molecules, and the more efficiently the gas hydrate can be formed, so that the gas hydrate generation rate becomes faster. For this reason, the proportion of the hydrophilic monomer in all the monomers is more preferably 30 mol% or more and less than 90 mol%, and particularly preferably 50 mol% or more and less than 90 mol%.

The gel polymer produced by the method (2) is preferably a copolymer containing at least a hydrophilic monomer unit and an amphipathic monomer unit, but the polymer and the amphipathic polymer consisting of only the hydrophilic monomer unit. It may be a mixture containing a polymer composed of only a monomer unit. During (co) polymerization, the total proportion of hydrophilic monomers and amphipathic monomers in all monomer units is 20 mol% or more 1
It is preferably not more than 00 mol%. The higher the total ratio of the hydrophilic monomer and the amphipathic monomer, the stronger the hydrophilicity of the gelled polymer obtained, and the more easily water molecules enter the gelled polymer. Therefore, when such a gel polymer is added to a system capable of generating gas hydrate, gas hydrate is generated from gas molecules taken into the gel and water molecules entering the gel by the Van der Waals force. It is easy to form and the stability of the system is improved. For this reason, the total ratio of the hydrophilic monomer and the amphipathic monomer in all the monomer units is 3%.
0 mol% or more and 100 mol% or less is more preferable, and 50 mol% or more and less than 100 mol% is particularly preferable. The ratio of the hydrophilic monomer to the amphipathic monomer is arbitrary, but a molar ratio of 20:80 to 80:20 is preferable.

The gel polymer produced by the method (3) is preferably a polymer containing only amphipathic monomer units or a copolymer containing amphipathic monomer units and hydrophobic monomer units. At the time of (co) polymerization, the proportion of the amphipathic monomer in all the monomer units is preferably 20 mol% or more and 100 mol% or less. The higher the proportion of the amphipathic monomer, the stronger the hydrophilicity of the gelled polymer obtained, and the more easily water molecules enter the gelled polymer. Therefore, when such a gel polymer is added to a system capable of generating gas hydrate, gas hydrate is generated from gas molecules taken into the gel and water molecules entering the gel by the Van der Waals force. It is easy to form and the stability of the system is improved. For this reason, the proportion of amphipathic monomers in all monomers is 30 mol% or more and 1
00 mol% or less is more preferable, and 50 mol% or more and 100
Less than mol% is especially preferred.

The hydrophilic monomer is a water-soluble compound having "a property of having a large interaction with water and a large affinity" and having a polymerizable group, and is referred to as a hydrophilic monomer unit. Is a repeating unit of a polymer obtained by polymerizing such a hydrophilic monomer. In addition, hydrophilic polymers have the property of having a large interaction with water and a large affinity.
It is a polymer having a "new edition polymer dictionary, p.216,
Asakura Shoten, 1988 ”, is a generic term for polymers that dissolve in water.

As the hydrophilic monomer, for example, N-
(Meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N
-(Meth) acryloylmethylhomopiperazine, N-
(Meth) acryloylmethylpiperazine, N-2-hydroxyethyl-N- (meth) acrylamide, N-3-
Hydroxypropyl (meth) acrylamide, N-2-methoxyethyl (meth) acrylamide, N-3-morpholinopropyl (meth) acrylamide, N- (meth) acryloylmorpholine, N-2-methoxyethyl-N-
Methyl (meth) acrylamide, (meth) acrylic acid and salts thereof, 2-hydroxyethyl (meth) acrylate, ethylene glycol (meth) acrylate, diethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol (meth) acrylate , Butanediol (meth) acrylate, trimethylolpropane (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylamidopropyl (meth) acrylamide, vinyl acetate, vinyl propionate, methyl vinyl ether, ethyl vinyl ether, 2-vinyl-2 -Oxazoline, 2
-Vinyl-4-methyl-2-oxazoline, 2-isopropyl-2-oxazoline, N-vinylacetamide,
N-vinyl-N-methylacetamide, N-vinylformamide, N-vinyl-N-methylformamide, N-
Vinyl-N-n-propylpropionamide, N-vinyl-N-methylpropionamide, N-vinyl-N-i
-Propylpropionamide, N-vinylpropionamide, vinyl butyrate, N-allylamide, maleic acid, vinylimidazole, dimethylaminoethyl (meth) acrylate methyl chloride salt, dimethylaminoethyl (meth) acrylate benzyl chloride salt, 2
-(Meth) acrylamido-2-methylpropanesulfonic acid and its salts, (meth) acrylamidomethanesulfonic acid and its salts, (meth) acrylamidoethanesulfonic acid and its salts, 2- (meth) acrylamido-n-butanesulfonic acid And salts thereof, glycosyloxyethyl acrylate, glycosyloxyethyl methacrylate, glycosyloxyethyl-α-ethyl acrylate, glycosyloxyethyl-β-methyl acrylate, glycosyloxyethyl-β, β-dimethyl acrylate, glycosyloxyethyl-β-ethyl. Acrylate, glycosyloxyethyl-β, β-diethyl acrylate, ethylene glycol, propylene glycol and the like can be mentioned.

Among these hydrophilic monomers, N-
(Meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N
-(Meth) acryloylmorpholine, N-2-methoxyethyl-N-methyl (meth) acrylamide, (meth)
Acrylic acid and its salts, 2-hydroxyethyl (meth) acrylate, ethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol (meth) acrylate, dimethylaminoethyl (meth) acrylate, vinyl acetate,
2- (meth) acrylamido-2-methylpropanesulfonic acid and salts thereof are preferred.

The amphiphilic monomer means "new edition polymer dictionary, p.486, Asakura Shoten, 1988", "physical chemistry dictionary".
5th edition, p. 1474, Iwanami Shoten, 1998 ”, which is a compound having both a hydrophilic group and a hydrophobic group,
It has a polymerizable group. In other words, it is a monomer that is soluble in both water and a solvent that is immiscible with water (generally called a non-aqueous solvent). Further, a monomer that does not show a clear amphipathic property but exhibits an amphipathic property when it becomes a polymer is included in the amphipathic monomer. What is an amphipathic monomer unit?
It is a repeating unit of a polymer obtained by polymerizing such an amphipathic monomer.

As the amphipathic monomer, for example, N-
Ethyl (meth) acrylamide, N-cyclopropyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-methyl-N-ethyl (meth) acrylamide,
N, N-diethyl (meth) acrylamide, N-methyl-N-isopropyl (meth) acrylamide, N-methyl-Nn-propyl (meth) acrylamide, N-
(Meth) acryloylpyrrolidine, N- (meth) acryloylpiperidine, N-2-ethoxyethyl (meth) acrylamide, N-3-methoxypropyl (meth) acrylamide, N-3-ethoxypropyl (meth) acrylamide, N-3 -Isopropoxypropyl (meth) acrylamide, N-3- (2-methoxyethoxy) propyl (meth) acrylamide, N-3- (2-methoxyethoxy) propyl (meth) acrylamide, N-tetrahydrofurfuryl (meth) acrylamide , N-1-
Methyl-2-methoxyethyl (meth) acrylamide,
N-1-methoxymethylpropyl (meth) acrylamide, N- (2,2-dimethoxyethyl) -N- (meth)
Acrylamide, N- (1,3-dioxolan-2-ylmethyl) -N- (meth) acrylamide, N-2-methoxyethyl-N- (meth) acrylamide, N-2-
Methoxyethyl-N-n-propyl (meth) acrylamide, N-2-methoxyethyl-N-isopropyl (meth) acrylamide, N, N-di (2-methoxyethyl) (meth) acrylamide, N-vinylpyrrolidone,
Examples thereof include N-vinylcaprolactam, N-isopropenylpyrrolidone and N-isopropenylcaprolactam.

Among these, N-ethyl (meth) acrylamide, N-cyclopropyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn
-Propyl (meth) acrylamide, N-methyl-N-
Ethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methyl-N-isopropyl (meth) acrylamide, N-methyl-Nn-propyl (meth) acrylamide, N- (meth) acryloylpyrrolidine, N- (meth) acryloylpiperidine, N
-Vinylpyrrolidone and N-vinylcaprolactam are preferred.

The hydrophobic monomer is a compound which has a property of "small interaction with water and a low affinity with water" and is hardly dissolved in water, and has a polymerizable group, and is hydrophobic. The monomer unit is a repeating unit of a polymer obtained by polymerizing such a hydrophobic monomer. The hydrophobic polymer is a polymer obtained from a hydrophobic monomer and is a general term for polymers that are only slightly soluble in water as described in "New Edition Dictionary of Polymers, p.254, Asakura Shoten, 1988".

Examples of the hydrophobic monomer include alkyl (meth) acrylates, alkyl (meth) acrylamides, heterocyclic (meth) acrylates, heterocyclic (meth) acrylamides, and lower alkyl as a substituent on the benzene ring. Examples thereof include vinylbenzenes which may have a group or a halogen atom.

Among these, in order to solve the problems of the present invention, in consideration of interaction due to intermolecular force with gas molecules in water, alkyl (meth) acrylates, alkyl (meth) acrylamides, heterocycles (Meth) acrylates and heterocyclic (meth) acrylamides are particularly preferable.

Specific examples of the alkyl (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate,
Isobutyl (meth) acrylate, t-butyl (meth)
Examples thereof include acrylate, lauryl (meth) acrylate, n-stearyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate and isobornyl (meth) acrylate.

Specific examples of the alkyl (meth) acrylamides include Nn-propyl (meth) acrylamide, Nt-butyl (meth) acrylamide and Ns-.
Butyl (meth) acrylamide, Nn-butyl (meth) acrylamide, N, N-diisopropyl (meth)
Examples thereof include acrylamide and N, N-di-n-propyl (meth) acrylamide.

Specific examples of the heterocyclic (meth) acrylates include tetrahydrofurfuryl (meth) acrylate, glycidyl (meth) acrylate, mevalonic lactone (meth) acrylate, γ-butyrolactone (meth) acrylate, and caprolactone-modified tetrahydro. Furfuryl (meth) acrylate, (meth) acryloylpiperidine, (meth) acryloylhexamethyleneimine and the like can be mentioned.

Specific examples of the heterocyclic (meth) acrylamides include N-furfuryl (meth) acrylamide.

The method for producing the gelled polymer containing the hydrophilic monomer unit and / or the amphipathic monomer unit is not particularly limited and can be produced by a known polymerization method.
For example, “Nagata, Kajiwara,“ Gel Handbook ”,
p. 56-67, NTT Corporation, 1999
It can be easily manufactured by the method described in “Year”.

As a method for obtaining a gelled polymer,
A method of adding a crosslinking agent at the time of polymerization is preferable. As the cross-linking agent used at that time, for example, a plurality of N, N'-methylenebisacrylamide, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, pentaethritol tri (meth) acrylate, etc. A compound having a (meth) acrylic group, N, N ′
-Butylenebis (N-vinylacetamide), N, N '
-N, N'-alkylenebis (N-vinylcarboxylic acid amide) compounds such as diacetyl-N, N'-divinyl-1,4-bisaminomethylcyclohexane, diethylene glycol diallyl ether, trimethylolpropane triallyl ether, tetraallyl Compounds having two or more allyl groups such as oxyethane, pentaerythritol triallyl ether, diallyl adipate and diallyl terephthalate, compounds having two or more vinyl groups such as divinylbenzene, divinyl oxalate, divinyl succinate, malonic acid Examples thereof include compounds having two or more vinyl ester structures such as divinyl, divinyl adipate, divinyl maleate, trivinyl citrate, and tetravinyl pyromellitic acid. The crosslinking agent may be used alone or in combination of two or more as required.

On the other hand, the gel polymer can also be produced by crosslinking an uncrosslinked chain polymer.

When a gelled polymer is produced by radical polymerization by heat, the solvent used is appropriately selected from water, alcohol and the like depending on the polymerization conditions. As the polymerization initiator, a conventionally known peroxide, organic peracid, inorganic peracid or a salt thereof, an azobis compound alone, or a redox compound in which a peroxide and a reducing agent are combined may be used. it can.

The method for controlling the production of gas hydrate according to the present invention is capable of producing the system in which gas hydrate is present or the gas hydrate from the gel polymer which is the above-mentioned agent for controlling production of gas hydrate according to the present invention. It is meant to exist in the system. Here, "a system capable of generating gas hydrate" means, for example, J. Long, A. Lederhos, A. Sum, R.
Christiansen, ED Sloan; Prep. 73rd Ann. GPA Con
v., 1994, pp. 1-9, a system in which a substance forming a gas hydrate is dissolved in an aqueous solvent. In such a system, gas hydrate precipitates as a crystalline substance under specific pressure and temperature conditions.

Examples of the substance that forms a gas hydrate include gases such as carbon dioxide, nitrogen, oxygen, hydrogen sulfide, argon, xenon, methane, ethane and propane, and liquids such as tetrahydrofuran.

As a system capable of producing gas hydrate, for example, in a natural gas well or an oil well, an aqueous phase in which a gas such as ethane or propane is dissolved in an aqueous solvent such as water or seawater is liquefied gas or crude oil. Examples thereof include systems that exist in the oil phase in a suspended / dispersed state, systems in which a gas phase such as natural gas exists in the aqueous phase, and the like. Further, naturally, a system artificially created conditions under which gas hydrate can be produced is also included.

The method for allowing the gas hydrate production controlling agent of the present invention to be present in a system in which a gas hydrate is present or a system capable of producing a gas hydrate is not particularly limited,
In the present invention, since it is a gelled polymer, for example, one side is 1
Examples include a method in which a gel-like polymer cut into a cubic shape of about cm is added to such a system. The gelled polymer to be added may have any size and shape, and may be cut to a granular form or conversely a larger block-shaped one. The gelled polymer is preferably present so as not to impair the fluidity in water in order to improve the contact efficiency with the gas that produces gas hydrate and the gas hydrate.

As a method for allowing the gelled polymer to exist in a system in which a gas hydrate is present or a system capable of producing a gas hydrate, the gelled polymer is dispersed in water and / or a solvent miscible with water. The method of adding one is preferable. The water-miscible solvent is a solvent that mixes with water at an arbitrary ratio, and examples thereof include methanol, ethanol, and acetone.

The amount of the gelled polymer to be present in the system containing the gas hydrate or the system capable of producing the gas hydrate is not particularly limited, but as described above, it does not impair the fluidity of the gelled polymer in water. Is preferred.

By allowing the gelled polymer to exist in a system in which a gas hydrate is present or a system in which a gas hydrate can be produced, a milder condition, that is, a pressure lower than the pressure normally produced by a gas hydrate, or ,
The gas hydrate can be transported or stored at high temperature. Further, when the gas hydrate is transported or stored, the produced gas hydrate can be used as a gel polymer unit. This is because the gas hydrate is preferentially produced in the gel-like polymer according to the present invention, and the fluidity of the entire water containing the gel-like polymer is not lowered even after the gas hydrate is produced, and This is because the polymer having gas hydrate formed inside the polymer can be selectively taken out.

The reason why the gas hydrate is preferentially formed in the gelled polymer is considered as follows. That is,
It is considered that the normally hydrophobic gas molecules are in a supersaturated state under the condition that the gas molecules forming the gas hydrate are dissolved in water. Here, by raising the system pressure or lowering the temperature, gas hydrate nuclei are formed by the gas molecules dissolved in water and the surrounding water molecule clusters, and the gas hydrate is gradually formed from such nuclei. It is thought to grow. Since the polymer that constitutes the gelled polymer has amphipathic properties, it is considered that the hydrophobic part in the polymer attracts gas molecules by the dispersive force (van der Waals force), and the hydrophilic part attracts water molecules. . In addition, it is considered that water molecules other than those in the immediate vicinity of the polymer chain in the gel-like polymer have almost the same properties as ordinary bulk water, and the cluster structure that is the starting point of gas hydrate formation is considered. Thought to form.

The gelled polymer containing gas hydrate or water containing the same can be stored even at room temperature and atmospheric pressure, but when stored as gas hydrate for a longer period of time, 5
A temperature condition of 20 ° C. or lower under a pressure of MPa or lower is preferable.

When the storage pressure is 5 MPa or more, a pressure vessel for storage having higher pressure resistance is required, so that the cost advantage of hydrated gas storage is reduced. For this reason, the more preferable storage pressure is 3MP.
It is a or less. As the gas for pressurization, air, nitrogen, or the same gas as that for forming the gas hydrate can be preferably used, but an inert gas such as nitrogen or argon is more preferable from the viewpoint of safety.

When the storage temperature exceeds 20 ° C., the decomposition of gas hydrate is promoted, so that the storage temperature is preferably 20 ° C. or lower, more preferably 15 ° C. or lower. Further, if the storage temperature is set to be lower than 0 ° C, the cooling energy becomes large, which is disadvantageous in cost. Therefore, the storage temperature is more preferably 0 ° C or higher and 15 ° C or lower, and particularly 2 ° C or higher and 15 ° C or lower.
C. or less is preferable.

When the gas hydrate production-accelerating and / or stabilizing agent of the present invention is used, for example, a rust inhibitor, a lubricant, a dispersant, a scale adhesion inhibitor, a corrosion inhibitor, a surfactant, etc. Various additives may be used in combination.

[0051]

EXAMPLES The present invention is described in detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

<Gas Hydrate Generator> FIG. 1 is a schematic view of a gas hydrate generator. The gas hydrate production start temperature, which is an index for promoting the production and / or stabilizing performance of the gas hydrate production control agent, was measured using this apparatus.

In FIG. 1, a pressure vessel 125 (hereinafter, also referred to as a cell) has an internal volume of 200 ml and a normal pressure of 15 M.
Pa or less. In this cell, a gas inlet pipe 111 having a valve 109, a gas exhaust pipe 113, an in-cell gas phase thermometer and thermocouple 105, an in-cell liquid phase thermometer and thermocouple 101, an in-cell stirring blade 123, and a stirring rod. 115 are provided. The entire cell can be immersed in the constant temperature bath 117, and the temperature inside the cell can be adjusted by the temperature of the constant temperature bath 117.

<Evaluation Method of Gas Hydrate Production Accelerating Performance> The gas hydrate production promoting performance was evaluated as follows. That is, distilled water was placed in the pressure vessel 125, and a gas hydrate production control agent to be evaluated, which was dispersed in distilled water, was added so that the concentration of the polymer solid content was 1% by mass. The cell was sealed and immersed in a constant temperature bath 117, methane gas was introduced from the gas introduction pipe 111 to make the internal pressure of the cell 11.5 MPa, and the internal cell temperature (liquid phase) was determined from the equilibrium temperature of methane hydrate formation at that pressure. Was set to 25 ° C, which is obviously high. Then, when the temperature inside the cell is gradually lowered at −4 ° C./hour while stirring inside the cell, methane hydrate is generated inside the cell at a certain temperature. Due to the formation of methane hydrate, the pressure inside the cell is lowered, and at the same time, since the formation of gas hydrate is an exothermic reaction, the temperature inside the cell is slightly increased. It was evaluated that the higher the temperature in the cell at the time when the pressure started to decrease greatly, that is, the higher the methane hydrate production temperature, the greater the gas hydrate production promotion performance.

Further, by confirming whether the produced methane hydrate is directly ignited and burned,
The suitability of the obtained methane hydrate for fuel applications was judged.

<Evaluation Method of Stabilizing Performance of Gas Hydrate> The stabilizing performance of gas hydrate was evaluated as follows. That is, using the apparatus shown in FIG. 1, methane hydrate was generated by maintaining the temperature inside the cell at 5 ° C. and the pressure inside the cell at 5 MPa for 1 hour, and then the methane hydrate was taken out from the cell at room temperature (25 ° C.). Then, the sample was left under atmospheric pressure, and the time until the end of decomposition by visual observation, that is, the time until bubbles of methane gas disappeared was measured. It was evaluated that the longer the time, the greater the stabilizing effect.

When the produced methane hydrate could not be taken out as a solid, the decomposition end time of the gas hydrate and the storage and transportation of the gas hydrate were not evaluated.

<Apparatus for storing and transporting gas hydrate> FIG. 2 is a schematic view of an experimental apparatus for storing and transporting gas hydrate. The pressure-resistant container 207 (hereinafter also referred to as a cell) in FIG. 2A is for generating gas hydrate by the same principle as the cell in FIG. 1, and 209 in FIG. 2B is a gas hydrate taken out from the cell. The rate. This gas hydrate is put in the storage and transportation tank 211 shown in FIG. The gas hydrate 209 is put in the storage and transportation tank 211, and after sealing, nitrogen gas is introduced as an inert gas from the gas supply and extraction line 213, and the tank internal pressure is set to 2 MPa, and the storage is carried out under an environment of 7 ° C. Tank 211 after 24 hours
After the internal pressure was returned to atmospheric pressure, the inside of the tank was checked to see if the gas hydrate was kept in a solid state, thereby judging the suitability of storage and transportation.

The evaluation results of all Examples and Comparative Examples are shown in Table 1 and Table 2, respectively.

<Example 1> In a 300 ml separable flask equipped with a nitrogen introducing tube, a thermometer and a cooling tube, t-
180 g of butanol, 20 g of N-isopropylmethacrylamide (manufactured by Mitsubishi Rayon Co., Ltd.) as an amphiphilic monomer,
After adding 0.2 g of ethylene glycol dimethacrylate (manufactured by Mitsubishi Rayon Co., Ltd.) as a cross-linking agent, nitrogen bubbling was performed at a flow rate of 200 ml / min to remove dissolved oxygen.
Then, the temperature in the flask was raised to 70 ° C., and 0.02 g of 2,2′-azobis (2-methylbutyronitrile) (Wako Pure Chemical Industries, Ltd., V-59) was added as a polymerization initiator to carry out polymerization. The polymerization was started for 6 hours under a nitrogen stream. The obtained gel polymer was taken out and dried under reduced pressure at 60 ° C. overnight to remove t-butanol, and dried gel polymer 20 g
Got After this, put the dry gel polymer in distilled water,
It was allowed to absorb water sufficiently and then left overnight. The gel polymer was taken out and cut into a cube having a side length of 1 cm to obtain a gas hydrate production control agent.

When the gas hydrate production promoting agent was evaluated for the obtained gas hydrate production control agent, the methane hydrate production temperature was 15.1 ° C. Methane hydrate was obtained in a state of being contained in a cubic production control agent. It was confirmed that methane burns when the obtained methane hydrate is directly ignited. Further, the time until the completion of the decomposition of methane hydrate contained in one cubic production control agent was 20 minutes.

Further, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate contained in the cubic production control agent was preserved in the state of starting storage, and methane was obtained by direct ignition. Was confirmed to have burned.

<Example 2> 20 g of N-isopropylacrylamide (manufactured by Kojin Co., Ltd.) as an amphipathic monomer and 0.2 g of N, N'-methylenebisacrylamide (manufactured by Wako Pure Chemical Industries, Ltd.) as a crosslinking agent were used. In the same manner as in Example 1, a cubic N-isopropylacrylamide polymer, which is a gas hydrate production control agent, was obtained.

When the gas hydrate formation promoting agent was evaluated for the obtained gas hydrate formation control agent, the methane hydrate formation temperature was 14.7 ° C. Methane hydrate was obtained in a state of being contained in a cubic production control agent. It was confirmed that methane burns when the obtained methane hydrate is directly ignited. Further, the time until the decomposition of methane hydrate contained in one cubic control agent was 18 minutes.

Further, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate contained in the cubic production control agent was preserved in the state of starting the storage, and the methane hydrate was directly ignited. Was confirmed to have burned.

<Example 3> N-as an amphipathic monomer
10 g of isopropylacrylamide (manufactured by Kojin Co., Ltd.), 10 g of N-acrylamide (manufactured by Mitsubishi Rayon Co., Ltd.) as a hydrophilic monomer, and 0.2 g of N, N′-methylenebisacrylamide (manufactured by Wako Pure Chemical Industries, Ltd.) as a crosslinking agent were used. Other than that, the same operation as in Example 1 was carried out to obtain a gas hydrate production control agent comprising an N-isopropylacrylamide / acrylamide copolymer.

When the gas hydrate production promoting agent was evaluated for the obtained gas hydrate production control agent, the production temperature of methane hydrate was 14.5 ° C. Methane hydrate was obtained in a state of being contained in a cubic production control agent. It was confirmed that methane burns when the obtained methane hydrate is directly ignited. Further, the time until the decomposition of methane hydrate contained in one cubic control agent was 18 minutes.

Further, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate contained in the cubic production control agent was preserved in the state of starting storage, and methane was obtained by direct ignition. Was confirmed to have burned.

Example 4 10 g of N-vinylcaprolactam (manufactured by Aldrich) as an amphiphilic monomer, 10 g of dimethylaminoethyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd.) as a hydrophilic monomer, and N, N'- as a crosslinking agent.
Methylenebisacrylamide (manufactured by Wako Pure Chemical Industries, Ltd.)
The same operation as in Example 1 was carried out except that 2 g was used to obtain a gel polymer composed of an N-vinylcaprolactam / dimethylaminoethyl methacrylate copolymer.

When the gas hydrate production-controlling agent thus obtained was evaluated for promoting gas hydrate production, the methane hydrate production temperature was 15.5 ° C. Methane hydrate was obtained in a state of being contained in a cubic production control agent. It was confirmed that methane burns when the obtained methane hydrate is directly ignited. Further, the time until the decomposition of methane hydrate contained in one cubic control agent was 21 minutes.

Further, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate contained in the cubic production control agent was preserved in the state of starting the storage, and methane was obtained by direct ignition. Was confirmed to have burned.

Example 5 In a 300 ml separable flask equipped with a nitrogen introducing tube, a thermometer and a cooling tube, 180 g of distilled water, 20 g of N, N-diethyl acrylamide (manufactured by Kojin Co., Ltd.) as an amphiphilic monomer, and a crosslinking agent were used. N,
N'-methylenebisacrylamide (manufactured by Wako Pure Chemical Industries)
After adding 1 g, nitrogen bubbling was performed at a flow rate of 200 ml / min to remove dissolved oxygen. Then, while maintaining the flask internal temperature at 20 ° C., 4% by mass as a polymerization initiator
Concentration ammonium persulfate (manufactured by Wako Pure Chemical Industries) aqueous solution 5
ml and a 4 mass% concentration N, N, N ′, N′-tetramethylethylenediamine (manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution (5 ml) were added to initiate polymerization, and polymerization was carried out under a nitrogen stream for 6 hours. The obtained gel polymer was taken out and dried under reduced pressure at 60 ° C. overnight to remove water, thereby obtaining 20 g of a dried gel polymer. Then, the dried gel polymer was put in distilled water to absorb water sufficiently, and then left overnight. Take out the gel polymer,
A cube cut to a side of 1 cm was used as a gas hydrate production control agent.

When the gas hydrate formation promoting evaluation was conducted on the obtained gas hydrate formation control agent,
The production temperature of methane hydrate was 15.8 ° C.
Methane hydrate was obtained in a state of being contained in a cubic production control agent. It was confirmed that methane burns when the obtained methane hydrate is directly ignited. Further, the time until the completion of decomposition of methane hydrate contained in one cubic production control agent was 24 minutes.

Further, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate contained in the cubic production control agent was preserved in the state of starting storage, and methane was obtained by direct ignition. Was confirmed to have burned.

Example 6 300 g of pure water was placed in a 300 ml separable flask equipped with a nitrogen introduction tube, a thermometer, a cooling tube and a stirrer, and 6 g of N-isopropylmethacrylamide (manufactured by Mitsubishi Rayon Co., Ltd.) as an amphiphilic monomer.
After adding 0.48 g of N, N'-methylenebisacrylamide (manufactured by Wako Pure Chemical Industries, Ltd.), nitrogen bubbling was carried out at a flow rate of 200 ml / min to remove dissolved oxygen. Then 7
The temperature in the flask was raised to 0 ° C., and 0.06 g of potassium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) which is a persulfate initiator as a polymerization initiator was added in a powder form to start polymerization. 1
Polymerization was carried out while stirring under nitrogen flow at a flow rate of 00 ml / min, and the reaction was continued at 70 ° C. for 6 hours. After cooling, a white turbid liquid containing polymer fine particles of N-isopropylmethacrylamide having an average particle diameter in water of 800 nm (measured by a Coulter counter) was obtained.

66 g of a 50% by mass aqueous acrylamide solution (manufactured by Mitsubishi Rayon Co., Ltd.) as a hydrophilic monomer was added to the resulting aqueous solution containing polymer fine particles, and N, N'as a crosslinking agent.
-Methylenebisacrylamide (manufactured by Wako Pure Chemical Industries, Ltd.)
After adding 1.65 g, nitrogen bubbling was performed at a flow rate of 200 ml / min to remove dissolved oxygen. After adjusting the liquid temperature to 20 ° C., the solution was transferred to a Dewar bottle having a capacity of 800 ml, and 8.25 ml of a 4 mass% ammonium persulfate (manufactured by Wako Pure Chemical Industries) aqueous solution as a polymerization initiator and 4 mass% N, N,
Polymerization was initiated by adding 8.25 ml of an aqueous solution of N ', N'-tetramethylenediamine (manufactured by Wako Pure Chemical Industries, Ltd.). Polymerization was carried out for 6 hours in a nitrogen stream to obtain a gel polymer composed of poly N-acrylamide in which fine particles of N-isopropylmethacrylamide were dispersed. This gel polymer was dried under reduced pressure at 60 ° C. overnight to obtain 32 g of dried gel polymer. Then, the dried gel polymer was put in distilled water to absorb water sufficiently, and then left overnight. Take out the gel-like polymer and put it on one side 1c
What was cut into a cube of m was used as a gas hydrate production control agent.

When the gas hydrate formation accelerating evaluation was carried out on the obtained gas hydrate formation control agent,
The production temperature of methane hydrate was 14.8 ° C.
Methane hydrate was obtained in a state of being contained in a cubic production control agent. Combustion of methane was confirmed when the obtained methane hydrate was directly ignited. In addition, the time required to complete the decomposition of methane hydrate contained in one cubic production control agent was 23 minutes.

Further, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate contained in the cubic production control agent was preserved in the state of starting storage, and methane was obtained by direct ignition. Was confirmed to have burned.

Example 7 In a 300 ml separable flask equipped with a nitrogen introducing tube, a thermometer, a cooling tube and a stirrer, 126 g of pure water and tetrahydrofurfuryl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd.) 54 as a hydrophobic monomer were used.
g, and 1 g of sodium polyacrylate (manufactured by Aldrich) as a dispersant were added, and nitrogen bubbling was performed at a flow rate of 200 ml / min to remove dissolved oxygen. Then, the temperature in the flask was raised to 80 ° C., and benzoyl peroxide (manufactured by NOF CORPORATION), which was a peroxide-based initiator, was used as a polymerization initiator.
Polymerization was initiated by adding 0.54 g. Polymerization is carried out while stirring under nitrogen flow at a flow rate of 100 ml / min.
The reaction was continued at 8 ° C for 8 hours. After standing to cool, average particle size 10μ
An aqueous solution in which the polytetrahydrofurfuryl methacrylate particles of m were dispersed was obtained.

In the aqueous solution containing the obtained polymer fine particles, 17 g of 2-hydroxyethyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd.) as a hydrophilic monomer, 16 g of polyethylene glycol methacrylate (manufactured by Aldrich), and triethylene glycol dimethacrylate (manufactured by Aldrich) as a crosslinking agent. 2 g), and nitrogen bubbling was performed at a flow rate of 200 ml / min to remove dissolved oxygen. Liquid temperature 2
After adjusting to 0 ℃, transfer to an 800 ml Dewar bottle,
As a polymerization initiator, 8.25 ml of a 4 mass% concentration ammonium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution and a 4 mass% tetramethylene diamine (manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution 8.
25 ml was added to initiate polymerization. Polymerization was performed for 6 hours in a nitrogen stream to obtain a gel polymer composed of a 2-hydroxyethyl methacrylate / polyethylene glycol methacrylate copolymer in which polytetrahydrofurfuryl methacrylate fine particles were dispersed. This gel polymer is 60 ℃
After drying under reduced pressure overnight, 32 g of a dried gel polymer was obtained. Then, the dried gel polymer was put in distilled water to absorb water sufficiently, and then left overnight. Take out the gel-like polymer and put it on one side 1c
What was cut into a cube of m was used as a gas hydrate production control agent.

Gas hydrate production acceleration evaluation was carried out on the obtained gas hydrate production control agent.
The production temperature of methane hydrate was 15.2 ° C.
Methane hydrate was obtained in a state of being contained in a cubic production control agent. Combustion of methane was confirmed when the obtained methane hydrate was directly ignited. In addition, the time required to complete the decomposition of methane hydrate contained in one cubic production control agent was 22 minutes.

Furthermore, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate contained in the cubic production control agent was preserved in the state of starting the storage, and the methane hydrate was directly ignited. Was confirmed to have burned.

<Comparative Example 1> When a hydrate was produced under the same conditions as in the examples without adding a gas hydrate production control agent, the methane hydrate production temperature was 12.
It was 0 ° C. Methane hydrate was foamy and could not be taken out as a solid.

Comparative Example 2 When methane hydrate was produced under the same conditions as in the example using tetrahydrofuran as a gas hydrate production control agent, the production temperature of methane hydrate was 14.1 ° C. . Combustion of methane was confirmed when the obtained methane hydrate was taken out and directly ignited. In addition, the time until the decomposition of about 1.2 g of this methane hydrate was completed was 4.5 minutes.

Further, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate was completely decomposed and that the water containing tetrahydrofuran remained as a liquid.

<Comparative Example 3> When methane hydrate was produced under the same conditions as in Example by using acetone as a gas hydrate production control agent, the methane hydrate production temperature was 13.1 ° C. Combustion of methane was confirmed when the obtained methane hydrate was taken out and directly ignited. Further, the time until the decomposition of about 1.2 g of this methane hydrate was 3.8 minutes.

Further, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate was completely decomposed and the water containing acetone remained only as a liquid.

<Comparative Example 4> When methane hydrate was produced under the same conditions as in Example using polyvinyl alcohol as a gas hydrate production control agent, the methane hydrate production temperature was 12.5 ° C. . Combustion of methane was confirmed when the obtained methane hydrate was taken out and directly ignited. The time required to complete the decomposition of about 1.2 g of methane hydrate was 9.9 minutes.

Further, when the storage and transportation of the obtained methane hydrate were evaluated, it was found that the methane hydrate was completely decomposed and only the water containing polyvinyl alcohol remained.

<Comparative Example 5> A methane hydrate was produced under the same conditions as in the example using a silicone resin-containing surfactant (KM-72, manufactured by Shin-Etsu Chemical Co., Ltd.) as a gas hydrate production control agent. However, the methane hydrate production temperature was 12.5 ° C. Methane hydrate was foamy and could not be taken out as a solid.

[0091]

INDUSTRIAL APPLICABILITY The gas hydrate production controlling agent of the present invention can efficiently produce a gas hydrate by promoting the production of the gas hydrate, and / or the produced gas hydrate. It has the effect of stabilizing the rate. By using such a gas hydrate production control agent of the present invention, it is possible to control the production of gas hydrate (production promotion and / or stabilization). Moreover, according to the transportation method and the storage method of the present invention, the gas hydrate can be efficiently or stably transported or stored. Further, the composition containing the gas hydrate of the present invention is suitable for efficient and stable transportation or storage of the gas hydrate.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus for producing gas hydrate.

FIG. 2 is a schematic configuration diagram of an apparatus for storing and transporting gas hydrate.

[Explanation of symbols]

101 Thermometer and Platinum Thermocouple (Liquid Phase Section) 103 Pressure Meter 105 Thermometer and Platinum Thermocouple (Gas Phase Section) 107 Distilled Water 109 Valve 111 Gas Introducing Pipe 113 Gas Discharging Pipe 115 Stirring Bar 117 Constant Temperature Bath 119 Water Surface 121 Gel Polymer 123 Stirrer 125 Pressure-resistant container 201 Gel-like polymer 203 Distilled water 205 Gas phase part 207 Pressure-resistant container 209 Gel-like polymer 211 taken out after gas hydrate formation and gas hydrate storage and transportation tank 213 Gas supply and Extraction line 215 Valve 217 Gel polymer containing gas hydrate

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F17C 11/00 C10L 3/00 AF term (reference) 3E072 EA10 4G075 AA03 AA22 AA62 BA10 BB10 CA03 CA51 DA01 DA18 4H006 AA02 AA05 AD15 BA51 4J100 AB16S AE03P AE04P AE69S AE71S AG02P AG63S AJ02P AK08P AK32P AL03R AL04R AL05R AL08P AL08R AL09P AL10R AL62P AL62S AL63P AL63S AL66S AM15P AM17P AM17Q AM17R AM19P AM19Q AM19R AM21P AM21Q AM24S AN04P AQ06P AQ06Q AQ08Q AR09R BA01Q BA03P BA04P BA04Q BA08P BA13P BA14P BA31P BA35P BA55P BC02Q BC43R BC53Q BC53R BC79P BC80P CA04 CA05 CA06 CA23 EA03 FA03 JA15

Claims (10)

[Claims] 1. A gas hydrate production control agent comprising a gelled polymer containing a hydrophilic monomer unit and / or an amphipathic monomer unit. 2. The proportion of hydrophilic monomer units in all monomer units of the gelled polymer is 20 mol% or more and 100.
2. The gas hydrate production control agent according to claim 1, wherein the content is less than or equal to mol% and the balance is a hydrophobic monomer unit. 3. The proportion of amphipathic monomer units in all monomer units of the gelled polymer is 20 mol% or more and 10 or more.
The gas hydrate production control agent according to claim 1, wherein the content is 0 mol% or less and the rest is a hydrophobic monomer unit. 4. The ratio of the total of hydrophilic monomer units and amphipathic monomer units in all the monomer units of the gelled polymer is 20 mol% or more and 100 mol% or less. Gas hydrate production control agent. 5. A gas comprising the gas hydrate production control agent according to claim 1 in a system in which gas hydrate is present or a system in which gas hydrate can be produced. Hydrate generation control method. 6. The method for controlling production of gas hydrate according to claim 5, wherein the agent for controlling production of gas hydrate is dispersed in water and / or a solvent miscible with water and added. 7. A method for transporting gas hydrate, which comprises using the method for controlling production of gas hydrate according to claim 5 or 6. 8. A method for storing gas hydrate, which comprises using the method for controlling production of gas hydrate according to claim 5 or 6. 9. A gas hydrate containing a gas hydrate production control agent is added to the gas hydrate at a pressure of 5 MPa or less at 0-2.
The method for storing gas hydrate according to claim 8, characterized in that the method is maintained at a temperature of 0 ° C. 10. A composition comprising a gas hydrate production control agent according to claim 1 and a gas hydrate.