KR20110094766A - Removal method of carbon dioxide in syngas using adsorbent for low temperature applications - Google Patents

Abstract

PURPOSE: A method for eliminating carbon dioxide in synthetic gas using a low temperature carbon dioxide absorber is provided to selectively eliminate carbon dioxide from the synthetic gas containing hydrogen and the carbon dioxide and separate pure hydrogen. CONSTITUTION: An absorber carries 10 to 50 weight% of sodium carbonate in alumina. 20 weight% of absorber is used for eliminating carbon dioxide from synthetic gas containing hydrogen and carbon dioxide. The carbon dioxide is absorbed to be converted hydrogen carbonate salt and is eliminated from the synthetic gas at low temperature. A reverse reaction is generated at high temperature.

Description

Removal method of carbon dioxide in syngas using adsorbent for low temperature applications}

The present invention relates to a hydrogen separation method by separating carbon dioxide from a mixed gas of hydrogen and carbon dioxide, and more particularly to selectively remove carbon dioxide using a sodium carbonate adsorbent supported on alumina.

In the case of the carbon dioxide adsorption process, a PSA process and a carbon dioxide removal method using a separator have been developed. The PSA process is a process for selectively adsorbing one or similar components of the feed gas mixture to the solid adsorbent to achieve an adsorption composition different from that of the feed mixture. This process not only has the advantage of separating high purity hydrogen with low energy and equipment cost, but also uses it to recover carbon dioxide, separate oxygen and nitrogen from air, recover carbon dioxide from steel mill exhaust gas, purify natural gas, etc. It is used. Separation of the mixed gas is a periodic process involving repeated adsorption at high pressure and desorption at low pressure. In addition, the process starts a new cycle from low pressure to high pressure and includes many technical steps to improve separation efficiency. The separator refers to a material that selectively passes or suppresses two different materials through obstacles, and the materials passing through are generally determined by a pressure gradient and an electrical potential difference. The membrane is defined by the size of the pores or the size of the material. Ceramic separators are prepared by chemical leaching, solid state sintering, and sol-gel methods, and are made of inorganic materials such as palladium-based elements, alumina, zeolite, zirconia, stainless steel, and glass. Since the ceramic separator is thermally stable at high temperatures, the separation process can be performed at high temperatures without changing the microstructure. In addition, because of its excellent chemical stability, it has a long service life and does not corrode or corrode even when experimenting with organic solvents or acid-alkaline solutions. However, the ceramic separator is relatively expensive to manufacture compared to the organic membrane, and there is a technical difficulty in industrial use because of the fragile nature. Accordingly, there is a demand for developing a powder type adsorbent having a small number of experimental variables and relatively simple removal of carbon dioxide. Accordingly, carbon dioxide can be adsorbed and removed using an adsorbent such as calcium oxide and lithium zirconate. However, calcium oxide or lithium zirconate not only exhibits carbon dioxide adsorption capacity at high temperatures of 700 ^° C. or more, but also has a small adsorption capacity. Therefore, there is a need for developing an adsorbent capable of removing carbon dioxide at a relatively simple method at low temperatures.

Thus, the present inventors have solved the above problems, to develop an adsorbent having a large adsorption capacity using an alkali-based carbonate that can be easily removed by adsorbing carbon dioxide at low temperatures. Alkaline carbonate adsorbs carbon dioxide along with the surrounding water and converts it into a form of hydrogen carbonate. At high temperatures, the reverse reaction proceeds, allowing rapid regeneration. In addition, the purpose of the present invention is to prepare an adsorbent that can maximize the carbon dioxide removal ability by supporting sodium carbonate in the alumina manufactured by itself to separate the carbon dioxide in the synthesis gas.

As described above, carbon dioxide can be removed using an adsorbent such as calcium oxide, lithium zirconate and alkali carbonate. However, calcium oxide or lithium zirconate not only exhibits carbon dioxide adsorption capacity at a high temperature of 700 ^° C. or higher, but also has a small adsorption capacity, which makes it difficult to remove carbon dioxide. Accordingly, research on the separation of carbon dioxide in syngas through the development of an adsorbent having a high adsorption capacity using an alkali carbonate that can easily remove and absorb carbon dioxide at low temperatures is required. Alkaline carbonate adsorbs carbon dioxide together with the surrounding water and converts it into the form of hydrogen carbonate. At high temperatures, the reverse reaction proceeds and rapid regeneration is possible. In addition, it is possible to maximize the adsorption capacity by supporting the alumina carrier.

The present invention is characterized in that in the selective removal of carbon dioxide in the hydrogen and carbon dioxide mixed gas using a carbon dioxide adsorbent, to prepare a 10 to 50% by mass of the adsorbent to react with water in the reactor to remove the carbon dioxide. The reaction apparatus for carbon dioxide adsorption used in the present invention used a vacuum glass trap having a diameter of 25 mm and a height of 200 mm. At this time, in order to provide the minimum moisture required in the adsorption reaction, the target gas was prepared to enter the reactor through the water layer. In order to prevent the adsorbent from directly reacting with excess moisture, the adsorbent was sequestered and filled using rock wool. The same amount of carbon dioxide and hydrogen was flowed into the reactor, where the flow rate ratio was supplied in the same amount. In order to control the temperature of the reactor, the reactor was installed in a thermostat and experimented in the range of 20-40 ^o C. The amount of carbon dioxide removed after the reaction was analyzed by gas chromatography by collecting 20 μl from a sampling unit installed in the reactor by time using a syringe. In case of sodium carbonate adsorbent for carbon dioxide adsorption reaction, the reaction experiment was performed while flowing carbon dioxide and hydrogen. At this time, in order to maximize the reactivity of the adsorbent was prepared alumina carrier having nano pores. Structural derivatives, lactic acid and precursor aluminum trisec butoxide were added to butanol and stirred for 2 hours. Distilled water to induce hydration and condensation reaction was stirred for 24 hours while supplying 0.5 ml per hour using a pump. The prepared alumina was dried in a drier, and the dried carrier was calcined in an electric furnace to provide gamma alumina crystallinity with structural derivative removal, thereby providing mechanical strength. In impregnating sodium carbonate in the prepared alumina, an impregnation method was used to prevent the reaction between sodium carbonate particles and distilled water, and an adsorbent of 10-50 mass% was prepared based on alumina. The adsorbent thus prepared was stored in a desiccator to suppress the reaction with moisture in the air.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by Examples.

Example 1

As the amount of sodium carbonate supported in the alumina increases to 10 to 50% by mass, carbon dioxide in the reactor may be removed, and thus the content of sodium carbonate in the reactor may drop slowly. That is, it can be seen that the formation of sodium bicarbonate occurs through the adsorption reaction. In addition, although the amount of carbon dioxide removed according to the amount of sodium carbonate is increased, the optimum amount can be found by calculating the number of adsorption moles per gram of the supported sodium carbonate of alumina. At 10, 20, 30, 40 and 50% by mass, the amount of carbon dioxide adsorbed was 2.38, 3.27, 2.94, 2.69 and 2.37 mmol per gram, indicating that the adsorbent's performance was rather deteriorated at 20% or more by mass. Can be.

Example 2

As in Example 1, the adsorption performance was examined at a reaction temperature of 20 to 40 ^° C. using an optimum loading of 20% by mass adsorbent. At the reaction temperatures of 20, 30 and 40 ^o C, the adsorption amount of carbon dioxide was 3.27, 3.12 and 2.83 mmol per gram. That is, it can be seen that the low temperature adsorbent shows the best adsorption capacity at the reaction at room temperature. This indicates that when the temperature in the reactor rises, the adsorption of carbon dioxide due to the exothermic reaction is suppressed and the desorption reaction, which is the reverse reaction, occurs. This shows the adsorbent regeneration performance in the following examples.

Example 3

As shown in the adsorption performance evaluation, it can be seen that the highest carbon dioxide adsorption capacity is obtained when 20 ^° C. and 20 mass% adsorbent are used. However, because the adsorbent is discarded after use, it is uneconomical and produces secondary environmental pollutants. The heat treatment induced a reverse reaction to regenerate the adsorbent. The adsorbent was reacted in a thermostat chamber after completely removing the water in the vacuum trap to prevent the reaction with other substances during regeneration. Regeneration temperature while flowing argon gas to 200 ml per minute in order to export the desorbed carbon dioxide while maintaining the 100 ^o C and held for 3 hours. As the number of regeneration was increased, the adsorption amount of carbon dioxide was 3.27, 3.01, 2.67 per gram.

Claims (2)

A method of removing carbon dioxide by using the most economical 20 mass% adsorbent among the adsorbents in which 10 to 50 mass% of sodium carbonate is supported on alumina in selectively adsorbing and removing carbon dioxide in a mixture of hydrogen and carbon dioxide.
     The method according to claim 1, wherein the produced 20 mass% is used to remove carbon dioxide at a low temperature, and a reverse reaction is generated to regenerate and repeat the use at a high temperature.