JP6331995B2 - Method for producing free carbon from carbonate - Google Patents

Description

  The present invention relates to a method for producing free carbon by separating carbon from a carbonate.

Carbon dioxide is often used as various additives or various raw materials. Sodium carbonate is used as a raw material for detergents, bath additives, and soda glass, and is also approved for use as a food additive. Calcium carbonate is used as a raw material for baby powder, chalk, rubber additives, bath additives, toothpaste and cosmetics.
However, no attempt has been made to produce free carbon from carbonates and use it as a carbon source, for example, fuel, additive, and the like.

As a general carbon production method, Patent Documents 1 to 4 include a method of heating and manufacturing organic substances such as pitch and tar, and Patent Documents 5 and 6 include a method of manufacturing by burning acetylene gas. It is disclosed. Quick lime CaO is known to efficiently absorb CO ₂ and produce calcium carbonate CaCO _{3. When} carbon in calcium carbonate can be separated into free carbon, CO ₂ is converted into C as a total. Can be converted. However, no such attempt has been made.

Japanese Patent Laid-Open No. 2002-083595 Japanese Unexamined Patent Publication No. 2011-168671 JP 2006-236842 A JP 2012-246215 A JP 2009-227552 A JP 2007-091495 A

  In view of the above circumstances, an object of the present invention is to provide a novel utilization method of a carbonate in which free carbon that can be used as a normal carbon source such as a fuel and an additive is produced from a carbonate. .

  Therefore, the present inventors diligently studied a method for solving the above problems. As a result, water glass or alkali silicate and carbonate were mixed and heated to find a technique for producing free carbon from carbonate, and the present invention was completed.

The gist of the present invention is as follows.
(1) Free carbon production characterized by mixing water glass or alkali silicate and carbonate and heating to 700 ° C to 1600 ° C in a non-oxidizing atmosphere to separate carbon from the carbonate. Method.
(2) The method for producing free carbon as described in (1) above, wherein the carbonate is at least one of an alkali element carbonate and an alkaline earth element carbonate.
(3) The method for producing free carbon as described in (2) above, wherein the alkali element carbonate is sodium carbonate, and the alkaline earth element carbonate is calcium carbonate.
(4) The method for producing free carbon according to any one of (1) to (3), wherein the alkali silicate is sodium silicate.

According to the present invention, free carbon that can be used as a normal carbon source for fuels, additives and the like can be produced from carbonates, and the range of utilization of carbonates can be expanded.
Furthermore, quick lime CaO is known to efficiently absorb CO ₂ and produce calcium carbonate CaCO _{3. When} carbon in calcium carbonate is separated into free carbon by using the method of the present invention, CO ₂ as a total is obtained. Can be converted to C.

Further, instead of CaO, to generate _Na 2 CO ₃ was absorbed CO ₂ to Na ₂ O, using the method of the present invention, when the carbon in the sodium carbonate to separate free carbon, CO ₂ as the total C Can be converted. The same reaction can also be applied to the case where carbon dioxide is produced by absorbing CO ₂ in other oxides, particularly alkaline earth and alkali metal oxides.

Hereinafter, the method for producing free carbon of the present invention will be sequentially described.
First, raw materials will be described.

Water glass is an aqueous solution of sodium silicate, and sodium silicate is described by a molecular formula of Na ₂ O · nSiO ₂ . Here, the coefficient n can be continuously changed. Generally, n = 0.5 to 4 in many cases, but in the present invention, n is not particularly limited. The ratio of sodium silicate which is a solid content in water glass is generally about 10 to 60% by mass, but this is not particularly limited. However, if the solid content concentration is high, that is, if the water content is small, the viscosity of the water glass becomes high, and handling becomes difficult when mixing with the carbonate. As what is easy to handle, the thing of n = 1-3 and solid content concentration of about 30-50 mass% can be mentioned, for example.

When the alkali element is described as A, the alkali silicate can be described as A ₂ O · nSiO ₂ · mH ₂ O, and A = Na has the same chemical formula as water glass. However, in the alkali silicate, H ₂ O is coordinated water or crystal water, or an anhydride, that is, m = 0. As a result, water glass is a liquid or a highly viscous liquid, whereas alkali silicate is usually a solid. As a normal distribution | circulation form of an alkali silicate, it is a solid powder with a particle size of 1 micrometer-1 mm, or a lump solid with a particle size of 5-several tens mm.

  The carbonate is not particularly limited. For example, carbonates of alkaline elements and carbonates of alkaline earth elements can be used, and specific examples include sodium carbonate and calcium carbonate. Although the form can use the thing of a general powder, it is not necessarily limited, For example, an average particle diameter of 1 micrometer-1 mm, Preferably, a 50-500 micrometer thing can be used.

Next, mixing will be described.
The mixing method of carbonate and water glass or alkali silicate may be a general mixing method, and mixing in a mortar or various mixers such as a rotary mixer can be used. The mixing ratio of the carbonate and water glass or alkali silicate is not particularly limited, but for example, a mass ratio of carbonate / water glass or alkali silicate can be selected from 0.05 to 5. This ratio is based on the ease of mixing of the carbonate and water glass or alkali silicate, and if the difficulty of mixing is allowed, the mass ratio of carbonate / water glass or alkali silicate is 0. 01-20 may be sufficient.

  As described above, carbonates are mostly powders having an average particle size of about 1 μm to 1 mm, and alkali silicates are generally powders having a particle size of about 1 μm to 1 mm or massive solids having a particle size of about 5 to several tens of mm. However, for these mixing, it is sufficient to mix for 1 to 10 minutes, preferably 2 to 5 minutes at 60 rpm, for example, if it is a rotary mixer.

Next, heating will be described.
Various heating furnaces can be used as the heating method. In addition, exhaust heat exhausted from various high-temperature processes can be used if the temperature is suitable, and a heating device using exhaust heat can also be used. Moreover, the heating apparatus which condenses sunlight can also be used. In general, a heating device that collects sunlight is difficult to use because the temperature control is rough, but in the present invention, it can be used because the temperature window of the reaction is wide, which is a feature of the present invention. is there.

  What is necessary is just to insert the crucible which put the above-mentioned mixture in these heating apparatuses, and to heat in a non-oxidizing atmosphere. The crucible material is not particularly limited, but a material having heat resistance to the heating temperature should be selected. For example, a crucible made of silica alumina, alumina, quartz or the like can be used.

  A non-oxidizing atmosphere is selected as the atmosphere. This is to prevent the generated free carbon from being oxidized. For example, an inert gas atmosphere such as an argon atmosphere, and a nitrogen atmosphere can also be selected. As the purity of the atmospheric gas, the purity of a general gas cylinder, for example, 99.99% is sufficient. With this degree of purity, oxidation of the generated free carbon can be substantially ignored in a general reaction apparatus. The flow rate of the atmospheric gas is not particularly limited and may be small from an economic point of view. If the present invention is carried out in a gas flow system for the purpose of preventing the pressure inside the reaction vessel from rising or breaking due to heating, the exhaust pipe As long as the flow rate is such that the gas does not flow backward. Examples of the flow rate include a flow rate of several tens of mL to several tens of L / min, preferably 100 mL to 2 L / min.

  The heating temperature is preferably 700 ° C. or higher and 1600 ° C. or lower, more preferably 850 ° C. or higher and 1300 ° C. or lower. As can be seen from the examples, 700 ° C. or higher is necessary in order to produce free carbon from the carbonate according to the present invention. Furthermore, when heating at a temperature of 700 ° C. or higher and about 850 ° C. or lower, the mixture often does not enter a molten state by heating, and the generated free carbon is often widely distributed in solids. When the mixture is heated to about 850 ° C. or higher, the mixture often becomes a molten state by heating, and the generated free carbon is likely to collect on the crucible wall surface or the upper surface of the melt, which is convenient for recovery of free carbon.

  Further, when the heating temperature is higher than 1600 ° C., only a small amount of free carbon is recognized, so the heating temperature is preferably 1600 ° C. or less. At temperatures higher than 1600 ° C., it is assumed that the free carbon once generated is reduced by oxidation with alkali silicate, but the details are unknown. Furthermore, considering the heat resistance of a general crucible, 1300 ° C. or lower is more preferable.

  There is no restriction | limiting in particular in the temperature increase rate of heating, For example, 1-40 degree-C / min which is the temperature increase rate of a normal heating furnace, Preferably, 10-20 degree-C / min can be selected. The holding time at the maximum temperature is not particularly limited, and a short time may be selected from an economical viewpoint. For example, 1 to 20 minutes, preferably 5 to 10 minutes is sufficient. There is no particular restriction on the cooling rate, and after the holding time at the maximum temperature, the heating can be terminated immediately and left to natural cooling of the device. If the cooling rate is limited due to the structure of the device, You may follow.

By these production methods, the generated free carbon is crushed and separated if the free carbon is segregated after the temperature decreases, and if the free carbon is widely distributed in the solid, hydrofluoric acid The solid matter can be dissolved in and the remaining free carbon can be separated.
The free carbon obtained as described above can be used as a normal carbon source such as fuel.

Although little is known about the reaction mechanism of the present invention, the following mechanism is presumed.
Both water glass and alkali silicate have the maximum amount of oxygen atoms, and neither can act as a reducing substance. Therefore, it is considered that the reducing substance is not involved in the progress of the reaction, and water glass or alkali silicate acts as a catalyst to generate free carbon from the carbonate. The presumed mechanism is that oxygen atoms of carbonate diffuse in alkali silicate and carbon is left behind. In this mechanism, oxygen atoms must be released from molten alkali-based oxides as oxygen molecules, but this phenomenon has not been confirmed so far, but is estimated.

  However, if estimated from this mechanism, the oxygen diffusion rate in the alkali silicate is not sufficient at 700 ° C. or lower, and therefore it is considered that 700 ° C. or higher is necessary in the present invention. Further, as described above, the free carbon once generated at a temperature higher than 1600 ° C. is estimated to be oxidized by the alkali silicate. The mixing ratio of the above-mentioned carbonate and alkali silicate is also considered to have an effect of effectively transferring oxygen atoms in the carbonate to the alkali silicate by diffusing well, but the details are unknown.

  The free carbon production efficiency according to the present invention is about 60% as described in Invention Example 5 described later. The reason why the free carbon production efficiency is considerably lower than 100% is that carbon dioxide is released from the carbonate, and the remaining part of the reaction to produce the alkali silicate and the compound proceeds simultaneously with the reaction of the present invention. It is considered that the efficiency does not reach 100%.

(Invention Example 1)
Commercial No. 3 water glass (Na ₂ O: SiO ₂ ratio is about 1: 3, water content is about 61%) and commercially available sodium carbonate powder are mixed, put into a silica alumina crucible, and predetermined in an Ar atmosphere heating furnace The temperature was raised to 10 ° C./min until the temperature was maintained for 5 minutes, and then naturally cooled to room temperature. After cooling, the inner wall of the silica alumina crucible turned black and a black product was deposited. The above experimental conditions and results are shown in Table 1.

  The crucible wall was roughly crushed and washed with diluted hydrofluoric acid. As a result, a powdery black product separated and floated on the surface of the cleaning solution, which was separated by filtration, washed with pure water, and then dried. About all the experiments of Table 1, carbon analysis of the dried powdery black matter by the combustion infrared absorption method revealed that it was almost 100% carbon. Furthermore, No. 1 in Table 1 When the black precipitate of No. 8 was analyzed by XPS (X-ray photoelectron spectroscopy), it was graphite type carbon.

  Since the only carbon source in the experimental system was sodium carbonate, it was found that free carbon was produced from sodium carbonate. The produced carbon is almost 100% pure free carbon and can be used as a carbon source for fuel and the like.

(Comparative Example 1)
Comparative Example 1 was the same as Example 1 of the present invention except that the temperature conditions were changed. In Comparative Example 1, no black matter was visible after the experiment. The experimental conditions and results are shown in Table 2.

(Invention Example 2)
Invention Example 2 was different from the commercially available No. 3 water glass except that a commercially available No. 1 water glass (Na ₂ O: SiO ₂ was about 1: 2 and the water content was about 52%) was used. The same experiment as in Example 1 of the present invention was performed. Table 3 shows the experimental conditions and results.

About all the experiments of Table 3, when the carbon analysis was carried out for the dried powdery black thing by the combustion infrared absorption method, it was about 100% carbon. Further, in Table 3, No. About 20 black deposits, when it analyzed by XPS (X-ray photoelectron spectroscopy), it was graphite type carbon.
Since the only carbon source in the experimental system was sodium carbonate, it was found that free carbon was produced from sodium carbonate.

(Comparative Example 2)
In Comparative Example 2, an experiment similar to that of Inventive Example 2 was performed except that the temperature condition was changed. In Comparative Example 2, no black matter was visible after the experiment. Table 4 shows the experimental conditions and results.

(Invention Example 3)
Inventive Example 3 was subjected to the same experiment as Inventive Example 1 except that a commercially available calcium carbonate powder was used instead of the commercially available sodium carbonate powder. Table 5 shows the experimental conditions and results.

About all the experiments of Table 5, when the carbon analysis was carried out for the dried powdery black thing by the combustion infrared absorption method, it was almost 100% carbon. Furthermore, when the black precipitate of No. 27 in Table 5 was analyzed by XPS (X-ray photoelectron spectroscopy), it was graphite type carbon.
It was found that free carbon was produced from calcium carbonate because the only carbon source in the experimental system was calcium carbonate.

(Comparative Example 3)
In Comparative Example 3, an experiment similar to that of Inventive Example 3 was performed except that the temperature condition was changed. In Comparative Example 3, no black matter was visible after the experiment. The experimental conditions and results are shown in Table 6.

(Invention Example 4)
Inventive Example 4 except that a commercially available sodium silicate powder (Na ₂ O: SiO ₂ contains about 1: 2 and about 19.5% water) was used instead of the commercially available No. 3 water glass. Then, the same experiment as in Example 1 of the present invention was performed. Table 7 shows the experimental conditions and results.

About all the experiments of Table 7, when the carbon analysis was carried out for the dry powdery black thing by the combustion infrared absorption method, it was about 100% carbon. Further, when the black precipitate No. 33 in Table 7 was analyzed by XPS (X-ray photoelectron spectroscopy), it was graphite type carbon.
Since the only carbon source in the experimental system was sodium carbonate, it was found that free carbon was produced from sodium carbonate.

(Comparative Example 4)
In Comparative Example 4, an experiment similar to that of Inventive Example 4 was performed except that the temperature condition was changed. In Comparative Example 4, no black matter was visible after the experiment. Table 8 shows the experimental conditions and results.

(Invention Example 5)
Invention Example 5 was carried out for the purpose of determining free carbon production efficiency.
0.7 g of commercially available sodium silicate powder (Na ₂ O: SiO ₂ is about 1: 2, containing about 19.5% water) and 0.07 g of commercially available sodium carbonate powder are mixed, and this is about 10 times the amount. The silica alumina particles (particle size of about 0.6 to 1 mm) are mixed for the purpose of securing a gas flow path, and the whole is charged into a quartz cell having a diameter of about 10 mm and a length of about 60 mm. It set to the gas analyzer which can be heated. The quartz cell was heated to 1100 ° C. at 10 ° C./min under helium gas flow, held for 5 minutes, and then naturally cooled to room temperature. During this time, the generated carbon dioxide gas was quantified by a gas analyzer, but the amount of carbon dioxide gas generated during 1100 ° C. holding and natural cooling is negligible compared to the amount generated during temperature rising. It was a great amount. Since the amount of carbon dioxide gas generated during 1100 ° C. holding was negligible, it is considered that the reaction was completed while the temperature was raised to 1100 ° C.

  The gas analyzer incorporates a quadrupole mass spectrometer manufactured by Microtrac Bell Co., Ltd. To correct the carbon dioxide quantification of the quadrupole mass spectrometer, 1% carbon dioxide and 99% helium mixed gas, 2% carbon dioxide and 98% helium mixed gas, 10% carbon dioxide and 90% helium mixed Performed using gas. Carbon dioxide, helium, and the like were analyzed at intervals of about once per second, and the amount of carbon dioxide was quantified from the sum of these analysis values and the helium flow rate.

  From the phase diagram etc., it is suggested that when sodium carbonate is reacted with about 10 times the amount of sodium silicate, carbon dioxide is released and becomes sodium oxide, which is completely taken into sodium silicate. A consistent amount of carbon dioxide should be measured. In contrast, in Example 5 of the present invention, only the amount of carbon dioxide corresponding to 41% of the number of moles of sodium carbonate was measured. Therefore, the free carbon production efficiency according to Invention Example 5 was calculated to be 59%. In addition, in the quartz cell after this experiment, free carbon was deposited in various ways.

  According to the present invention, free carbon that can be used as a normal carbon source such as fuel and additives can be produced from a carbonate. Therefore, the present invention has high industrial applicability.

Claims (4)

  A method for producing free carbon, comprising mixing water glass or alkali silicate and carbonate and heating in a non-oxidizing atmosphere to 700 ° C. to 1600 ° C. to separate carbon from the carbonate.   The method for producing free carbon according to claim 1, wherein the carbonate is at least one of an alkali element carbonate and an alkaline earth element carbonate.   The method for producing free carbon according to claim 2, wherein the alkali element carbonate is sodium carbonate, and the alkaline earth element carbonate is calcium carbonate.   The method for producing free carbon according to any one of claims 1 to 3, wherein the alkali silicate is sodium silicate.