JP4195932B2 - Control method of clathrate formation using trehalose - Google Patents

Description

  The present invention relates to a method for suppressing the formation of an inclusion compound from water and a liquid such as a gas body and / or a solvent by adding trehalose, and transportation of a liquid such as a gas body and / or a solvent to which the method is applied. The present invention relates to a method for preventing clogging of a pipe and a method for transporting and storing a liquid such as a gas body and / or a solvent to which the method is applied.

  Inclusion compounds include hydrocarbon gases such as methane and propane, acidic gases such as carbon dioxide and hydrogen sulfide, rare gases such as neon and krypton, fluorocarbons such as HFC-32 and HFC-134a, tetrahydrofuran and acetone, etc. A solid containing guest molecules at a high concentration far exceeding the solubility in water (or ice) when molecules such as organic solvents (called guest molecules) react with water (also called host molecules) under low-temperature and high-pressure conditions. Say that. This material was discovered at the end of the 18th century, but in the 1950s, an accident occurred in a high-latitude petrochemical plant where a transportation pipe was blocked, and it attracted much attention as the causative agent. Thereafter, in order to prevent such accidents, research has been progressed mainly on technology that inhibits generation (see, for example, Non-Patent Document 1). In addition, guest molecules with a relatively large molecular size such as organic solvents such as methylcyclohexane and isopentane and liquid hydrocarbons do not generate inclusion compounds by themselves, but do not contain inclusion compounds in the presence of the aforementioned gaseous guest molecules. It is also known to generate.

  As fossil fuels gradually develop in the polar regions and deep water regions, the clathrate compound formation suppression technology is an old and new technology that is still a subject of research (see Non-Patent Document 2, for example). In addition, it is known that natural gas not only associated with these fossil fuels is present in the form of clathrate compounds in sediments on the seabed and in the permafrost in the polar region. Development research for developing natural gas as a natural gas resource has been started (see, for example, Non-Patent Document 3).

  Furthermore, industrially utilized techniques have begun to be studied using the unique properties of the inclusion compound, such as high density guest molecule inclusion and guest molecule selectivity during generation and decomposition reactions. For example, as a natural gas storage / transport technology using an inclusion compound, “Gas hydrate cargo handling method and apparatus” (Patent Document 1) and “Natural gas hydrate production method and system” (Patent Document 2) , “Method and apparatus for producing gas hydrate” (Patent Document 3), “Transport and utilization method of gas hydrate” (Patent Document 4), “Method for transporting natural gas hydrate and its container” (Patent Document 5) Some of these approaches involve processes involving slurry fluids containing inclusion compounds in their transport form.

  In these technological developments, it is extremely important to control the formation, growth and decomposition behavior of inclusion compounds. In particular, as described above, the technology for suppressing the formation of clathrate compounds has a wide range of applications.

  As a technique for suppressing the formation of the wrapping theory compound, a method using mainly the following two additives is mainly used. One is to use an additive (such as seawater or alcohol) that shifts the equilibrium condition of the clathrate compound to the inhibitory side, and the other is an additive that suppresses the crystals that are formed (almost no change in the equilibrium condition) PVP and other chemicals). Although both methods are used in actual production, the former additive does not suppress the growth of the clathrate compound. It cannot be suppressed. The latter additive is still under development, but the environmental impact assessment has not been conducted sufficiently and there are many economic problems.

  Uchida et al. (1999) conducted an experiment to produce a carbon dioxide clathrate compound and investigated the growth rate of the film clathrate compound produced at the pure water-carbon dioxide interface. As a result, it has been found that the growth rate of the carbon dioxide clathrate compound is expressed as a function of the deviation from the equilibrium temperature (supercooling degree DT) when the generation starts under the pressure (non-patent document 4). ). Uchida et al. (2002) conducted a similar experiment with an aqueous solution containing NaCl, and the inclusion compound produced at the NaCl aqueous solution-carbon dioxide interface has a slower growth rate than pure water and has a higher NaCl concentration. It was found that the growth rate suppression effect was so great (Non-patent Document 5).

  It has become clear that trehalose, a natural carbohydrate that can be mass-produced from starch in recent years, is effective as a technology to suppress the formation of ice, which is a hydrogen compound crystal similar to clathrate compounds. 6). Since it is a natural carbohydrate, the environmental load is very small, and since it is used as an aqueous solution, it can be considered to have the advantage of being less contaminated with guest molecules. However, its function has so far been limited to the crystal structure of ice.

Japanese Patent Laid-Open No. 2003-171678 Japanese Patent Laid-Open No. 2003-105362 JP 2003-055677 A Japanese Patent Laid-Open No. 2002-161288 JP 2000-304196 A Sloan, E.D.Jr., Clathrate Hydrates of Natural Gases 2nd Ed. Revised and Expanded, Marcel Dekker Inc., 1998 Carroll, J.J., Natural Gas Hydrates: A Guide for Engineers, Butterwort-Heinemann, 2002 Paull, C.K and Dilloin, W.P. Eds., Natural Gas Hydrates: Occurrence, Distribution, and Detection Uchida et al., J. Crystal Growth, 204, p. 348, (1999) Uchida et al., J. Crystal Growth, 237-239, p. 383, 2002 Sei et al., J. Crystal Growth, 240, p. 218, 2002

  The object of the present invention is to produce a gas body such as natural gas or a liquid such as petroleum or an organic solvent in a transport pipe or to grow an industrially produced clathrate slurry in a transport pipe. To provide a method for adding and dissolving saccharides such as trehalose, which are naturally produced and have high environmental harmony, in an aqueous solution in order to suppress the formation of clathrate compounds that cause a blockage accident of the transport pipe. .

  As a result of earnest research on the formation process of the formed clathrate compound with the aqueous solution and guest molecules used for the clathrate compound generation, the present inventor has reported that the trehalose aqueous solution is effective in controlling the formation of ice. Finding that when forming an clathrate compound, the rate of growth after the clathrate phase crystals are generated is slower than when pure water is used, and the effect varies depending on the concentration of trehalose in the aqueous solution. Based on this, the present invention has been completed.

  That is, the present invention is a method for suppressing the formation of an inclusion compound by adding trehalose when the inclusion compound is formed from water and a liquid such as a gas body and / or a solvent.

  Furthermore, the present invention relates to the transportation and storage of a gas body and / or liquid characterized by adding trehalose to suppress the formation of an inclusion compound when transporting and storing a liquid such as a gas body and / or a solvent. Is the method.

  Furthermore, the present invention is a method for preventing clogging of a transport pipe by adding trehalose to suppress the formation of an inclusion compound in a method of transporting a liquid such as a gas body and / or a solvent by a transport pipe.

In each of the above methods, examples of the gas body include hydrocarbon gases such as methane and propane, acidic gases such as carbon dioxide and hydrogen sulfide, and rare gases such as neon and krypton, and examples of the solvent include HFC-32 and Examples include fluorocarbons such as HFC-134a, organic solvents such as tetrahydrofuran and acetone, or organic solvents such as methylcyclohexane and isopentane that form an inclusion compound in the presence of the above gas body, and liquid hydrocarbons. The trehalose to be used has a concentration in an aqueous solution of trehalose of 10% or more, preferably 40% or more.

  According to the present invention, when an clathrate compound is formed from water and a liquid such as a gas body and / or a solvent, the formation of the clathrate compound can be suppressed by adding trehalose thereto. By applying this method to a method of transporting a liquid such as a gas body and / or a solvent through a transport pipe, it was possible to prevent the transport pipe or the like from being blocked due to the formation of an inclusion compound.

  Conventionally, trehalose has a size specific to the average structure of water, and therefore a mechanism has been proposed that suppresses the progress of crystallization in an aqueous solution. However, there is no report that trehalose suppresses the growth rate of the inclusion compound between water and a gas body such as carbon dioxide, and the present inventors have obtained such knowledge for the first time. Trehalose itself is a naturally-occurring substance, and therefore has high environmental harmony, unlike production control / inhibitors synthesized with chemicals. In addition, unlike NaCl, which has been known as a substance that suppresses the growth rate of clathrate compounds, there is an advantage that there is little risk of corroding the reaction vessel or the transport pipe.

  In the method of the present invention, the clathrate compound is produced after the formation reaction has occurred by adding trehalose when the guest molecular phase (gas phase or liquid phase) capable of producing the clathrate compound is reacted with water as described above. It consists of a technology that suppresses the growth of the inclusion compound by reducing the growth rate of the.

  The trehalose used in the present invention is a non-reducing saccharide in which two butter sugar molecules are linked by α, α-1, 1 and commercially available products can be used (manufactured by Hayashibara Shoji Co., Ltd.). Normally, trehalose may contain trace amounts of moisture and impurities, but the trehalose used in the present invention includes water-containing crystals that contain 98% or more, preferably 99% or more of trehalose.

As guest molecules capable of generating an inclusion compound used in the present invention, in addition to methane gas, hydrocarbon gas or carbon dioxide gas, which is a main component of natural gas such as ethane gas, propane gas, nitrogen gas, oxygen gas, sulfide Examples include small molecules such as hydrogen, and rare gases such as xenon gas, argon gas, and krypton gas. Also, fluorocarbons such as HFC-32 (difluoromethane (CH ₂ F ₂ )) and HFC-134a (1,1,1,2-tetrafluoroethane (CH ₂ FCF ₃ )), organic solvents such as tetrahydrofuran and acetone The guest molecules such as ammonium salt aqueous solution and the like can form an inclusion compound under normal pressure conditions, unlike the above guest molecules. In addition, guest molecules such as organic solvents such as methylcyclohexane and isopentane, which are relatively large in molecular size, and liquid hydrocarbons, do not form inclusion compounds by themselves, but they do not form inclusion compounds in the presence of the aforementioned gaseous guest molecules. It is also known to generate. Although carbon dioxide gas was used here, the method used in the present invention is generally valid for guest molecules as described above.

  The water used in the present invention is usually deionized / degassed distilled water, but generally holds even if some impurities such as salts and bases are contained. However, since the formation equilibrium condition of the clathrate compound may shift depending on the type and concentration of impurities contained, the component ratio in the obtained gas or clathrate compound may differ.

  The reaction conditions are lower temperature and higher pressure conditions than the equilibrium conditions expected from the reaction between the guest molecules used and pure water. For example, when carbon dioxide gas is used, the equilibrium pressure of the clathrate compound produced by reaction with pure water is about 1.2 MPa at 273.2K. Therefore, experiments using this gas are performed in the range of 1.2 MPa or more. The temperature range is arbitrary depending on the pressure conditions, but trehalose is hardly dissolved in ice, so it is preferable to perform the reaction under the reaction conditions with an aqueous solution, and it is performed at 273.2K or higher.

  FIG. 1 shows a clathrate compound production observation apparatus used in the present invention. This apparatus is used to measure the rate of clathrate formation in a carbon dioxide gas-pure water (or salt water) system (Non-Patent Document 5), and is suitable for quantitatively comparing the effects of trehalose aqueous solutions. A fixed amount of water sample is put in a high-pressure vessel HV, and the whole is put in a thermostat TB to a predetermined temperature. After that, the air in the HV is exhausted, and the guest molecule sample is introduced into the HV from the cylinder B, and is set to a predetermined pressure. Then, the setting of the thermostatic chamber is lowered and brought to the inclusion compound generation conditions. The time when the temperature / pressure reaches the inclusion compound generation condition is set to zero, and the temperature / pressure is measured with the thermocouple TC and the pressure gauge PG, and is recorded with the recorder R.

  Confirmation of the generation of the clathrate compound is performed by visual observation from the observation window W and by the temperature rise of the system accompanying the generated heat release. The growth rate of the clathrate compound was measured by observing the inside of the system with a microscope MS through an observation window and analyzing the image obtained by recording the change with a video camera VTR.

In addition, after the measurement experiment of the production | generation rate, the temperature in a system was raised, the inclusion compound was decomposed | disassembled, and the change of the equilibrium conditions by the trehalose aqueous solution was confirmed by measuring the decomposition | disassembly temperature.
In addition to the systems shown in the following examples, the present invention includes methane clathrate compounds having the same crystal structure, propane clathrate compounds having different crystal structures, many fluorocarbon clathrate compounds, and ammonia salts referred to as quasi clathrate compounds It was shown that it can be used as a production inhibitor for clathrate compounds and the like. Therefore, the production control method according to the present invention can also be applied to the technology using these clathrate compounds.

  In addition, the present invention provides an aqueous clathrate-forming aqueous solution and a feature that nucleation occurs almost without changing the equilibrium condition between the gas body and the clathrate compound, and the growth of the clathrate compound after nucleation is remarkably suppressed. Even if crystals are generated, it does not grow greatly and is considered to be in a slurry state mixed with an aqueous solution. Therefore, by setting the temperature and pressure conditions to make use of these characteristics, it is possible to prevent clogging by inclusion compounds such as transport pipes.

  Hereinafter, the present invention will be specifically described by way of examples. However, the technical scope of the present invention is not limited to these examples.

One drop (about 0.5 cm ³ ) of an aqueous solution of trehalose (2 water-containing crystal powder) dissolved in a deionized / degassed distilled water sample at a predetermined concentration is added to the high-pressure reaction vessel HV (internal volume of about 10 cm ³⁾ ) Enclose in and put in a thermostatic chamber TB. At that time, the air remaining in the HV is deaerated by the vacuum pump VP by opening the valve V2. The valve V2 is closed after deaeration.

  Thereafter, the valve V1 is opened, a carbon dioxide gas sample is introduced into the HV from the cylinder B, the pressure is increased to a predetermined pressure, and then the valve V1 is closed. Then, after confirming that the temperature and pressure are in a predetermined condition, the setting of the thermostatic chamber TB is lowered to bring the temperature to a predetermined temperature. After reaching the clathrate generation temperature at the set pressure, observe the clathrate compound formation on the interface.

  In the experiment for producing the carbon dioxide clathrate compound, an aqueous solution in which 50 wt% of trehalose was dissolved was used. The thermostatic chamber temperature was set to 263.2K, and the internal pressure was set to about 5 MPa. The equilibrium temperature at this time was about 279.4K, which is 3K lower than the equilibrium temperature of the clathrate compound obtained in the pure water-carbon dioxide system as a result of the decomposition experiment. This is understood as a result of the molar freezing point effect due to the dissolution of trehalose.

In the same experimental system, the growth rate v _f of the film clathrate compound determined from the video image of the growth process of the carbon dioxide clathrate compound was determined to be about 0.3 mm sec ⁻¹ . The growth rate in pure water-carbon dioxide system at the same supercooling degree DT = 7 K is about 11 mm sec ^-1 , and the concentration of 10 wt% NaCl aqueous solution-carbon dioxide system was found to be greatly suppressed The growth rate with the same degree of supercooling is estimated to be about 1.7 mm sec ⁻¹ (Non-patent Document 5). Compared with these results, it was suggested that the growth rate in the 50 wt% trehalose aqueous solution-carbon dioxide system has a greater growth-inhibiting effect than the NaCl aqueous solution with a concentration three times that of seawater.

In the same manner as in Example 1, an experiment was conducted using an aqueous solution and carbon dioxide gas having trehalose concentrations of 1 wt% and 10 wt% as samples. As a result of measuring the growth rate of the carbon dioxide clathrate compound under the same conditions, an inhibitory effect on the growth rate was observed in all cases. When an aqueous solution having a trehalose concentration of 10 wt% was used, the growth rate was about 4 mm sec ⁻¹ at a supercooling degree DT = 18 K. This value is equivalent to or slightly smaller than the growth rate (about 6.9 mm sec ^-1 ) at the same supercooling degree in a 10 wt% NaCl aqueous solution-carbon dioxide system, and the growth rate in pure water-carbon dioxide system (about 45 mm sec ^-1 ). In the case of an aqueous solution having a trehalose concentration of 1 wt%, the growth rate was about 8.5 mm sec ⁻¹ at DT = 15 K. This value is almost the same as the growth rate (about 5 mm sec ^-1 ) at the same supercooling degree in a 10 wt% NaCl aqueous solution-carbon dioxide system, and the growth rate (about 34 mm in pure water-carbon dioxide system). It is estimated to be significantly smaller than sec ^-1 ). These results are shown in Table 1.

  Therefore, it was found that the change in the clathrate growth rate suppressing effect due to the trehalose concentration was larger as the concentration was higher.

  Compared to the test results on ice growth rate (Sei et al., 2002), it has been reported that the growth rate is suppressed as the trehalose concentration increases to 20.8 wt%, 41.7 wt%, and 52.1 wt%. . Further, the growth rate suppression effect at a trehalose concentration of 20.8 wt% is equivalent to that of an aqueous solution to which 41.5 wt% of saccharose, which is the same saccharide, is added, indicating the high effect.

The figure which shows the outline of the production | generation observation apparatus structure used in the Example

Explanation of symbols

B: High-pressure cylinder for gas
V1, V2: Valve
HV: High-pressure reactor
TB: Thermostatic bath
SM: Aqueous solution (sample)
PG: Pressure gauge
TC: Thermometer
R: Recorder
VP: Vacuum pump
W: Observation window
MS: Microscope
VHS: Video camera

Claims (12)

Upon inclusion compounds from a liquid comprising water and a body of gas and / or solvent is formed, the method of preventing formation該包abutment compound characterized by the addition of trehalose. 2. The formation suppressing method according to claim 1, wherein the gas body is a hydrocarbon gas composed of methane or propane, an acidic gas composed of carbon dioxide gas or hydrogen sulfide, and a rare gas composed of neon or krypton. An organic solvent consisting of fluorocarbon consisting of HFC-32 or HFC-134a, an organic solvent consisting of tetrahydrofuran or acetone, or an organic solvent consisting of methylcyclohexane or isopentane that forms an inclusion compound in the presence of a gas body according to claim 2, or 2. The production suppression method according to claim 1, which is a liquid hydrocarbon.   2. The formation inhibiting method according to claim 1, wherein the trehalose concentration in the aqueous solution is 10% or more. When transportation and storage of liquid consisting of a gas material and / or Solvent, gas body and / or methods transportation and storage of liquid, characterized in that to suppress the formation of the addition of trehalose clathrate. Hydrocarbon gas gas body is methane or propane, acid gases, and rare gas scan a body of gas and / or process transportation and storage of liquid according to claim 5, wherein comprising a neon, or krypton comprising a carbon dioxide gas or hydrogen sulfide. An organic solvent consisting of fluorocarbon consisting of HFC-32 or HFC-134a, an organic solvent consisting of tetrahydrofuran or acetone , or an organic solvent consisting of methylcyclohexane or isopentane that forms an inclusion compound in the presence of a gas body according to claim 6 , or 6. The method for transporting and storing a gas body and / or liquid according to claim 5, wherein the method is a liquid hydrocarbon.   6. The method for transporting and storing a gas body and / or liquid according to claim 5, wherein the trehalose concentration in the aqueous solution is 10% or more. A method of transporting a transport pipe of the liquid consisting of the gas body and / or Solvent A method of preventing clogging of the transport tube, characterized in that to suppress the formation of the addition of trehalose clathrate. 10. The method for preventing clogging of a transport pipe according to claim 9, wherein the gas body is a hydrocarbon gas composed of methane or propane, an acidic gas composed of carbon dioxide gas or hydrogen sulfide, and a rare gas composed of neon or krypton. An organic solvent consisting of fluorocarbon consisting of HFC-32 or HFC-134a, an organic solvent consisting of tetrahydrofuran or acetone , or an organic solvent consisting of methylcyclohexane or isopentane that forms an inclusion compound in the presence of a gas body according to claim 6 , or 10. The method for preventing clogging of a transport pipe according to claim 9, which is a liquid hydrocarbon.   10. The method for preventing clogging of a transport pipe according to claim 9, wherein the trehalose concentration in the aqueous solution is 10% or more.

Images