KR100530954B1 - Adsorbent and method for desulfurization of city gas - Google Patents

Abstract

The present invention is to provide a desulfurization adsorbent and desulfurization method using the same to effectively remove the organic sulfur compound in order to utilize the city gas to which the organic sulfur compound is added as a fuel for fuel cells.

The present invention relates to an adsorbent prepared by supporting one or more transition metals selected from Fe, Co, Ni, Cu, and Zn in a zeolite and calcining in a reducing atmosphere, and a method for removing sulfur compounds using the prepared adsorbent.

By passing the city gas into contact with the adsorbent described above, sulfur compounds which are odorants in the city gas can be removed with high efficiency by adsorption.

Description

Adsorbent and method for desulfurization of city gas {Adsorbent and method for desulfurization of city gas}

The present invention relates to an adsorbent for removing organic sulfur compounds in city gas and a desulfurization method using the same.

More particularly, the present invention relates to a method for adsorbent for desulfurization of city gas prepared by supporting one or two or more kinds of transition metals selected from Fe, Co, Ni, Cu, and Zn in a zeolite and firing in a reducing atmosphere.

Conventionally, city gas, which is mainly used as a fuel, has t-butylmercaptan (TBM), tetrahydrothiophene (THT), isopropyl mercaptan (Isopropyl) to prevent the risk of leakage during use. organic sulfur compounds such as mercaptan and IPM) are contained in trace amounts as odorants.

At present, the city gas supplied from Korea is mixed with organic sulfur compound odorant of THT and TBM at a ratio of about 7: 3, and the concentration of the odorant is known to be about 4 ppm (15 mg / m 3).

The organic sulfur compound odorant is necessary in order to prevent accidents due to gas leakage, but when using the city gas for the purpose of producing hydrogen or syngas, it causes a problem of poisoning of the catalyst in the reforming process.

A typical example thereof is the case of producing hydrogen, which is a fuel of a fuel cell, using city gas.

The fuel cell has been studied in advanced countries such as the United States, Japan, and Europe because of its high efficiency and cleanliness.

There are many kinds of fuel cells such as phosphate fuel cell, polymer electrolyte fuel cell, molten carbonate fuel cell, solid oxide fuel cell, etc. However, most of them can use only hydrogen as fuel or even if not, hydrogen is used as the most advantageous fuel for power generation efficiency. have.

In a fuel cell system which usually uses city gas as a primary raw material, it can be said that the specific gravity of the fuel processing process for producing hydrogen is about one third of the total.

The fuel treatment process is to produce hydrogen from raw city gas, a desulfurization process to remove sulfur contained in natural gas, a reforming process to convert hydrocarbons into H ₂ and CO, and a water gas conversion to convert CO into CO ₂ . (WGS) process, and optionally a selective oxidation (PROX) process that lowers residual CO in ppm.

The desulfurization process removes sulfur contained in a small amount of city gas. If the sulfur is not properly removed, the catalyst of the reforming process may be deactivated, which may adversely affect the life.

It also adversely affects the WGS process, the PROX process, and the fuel cell anode after the reforming process, resulting in increased fuel cell costs due to reduced catalyst life due to catalyst deactivation.

Therefore, a desulfurization process is essential in the fuel treatment process and it is required to lower the concentration of sulfur to at least 0.1 ppm or less after the fuel treatment.

Desulfurization techniques fall into two broad categories. In the case of large-scale steam reforming processes, which are most commonly used for hydrogen production, high-temperature hydrodesulfurization (HDS) is commonly used to desulfurize raw materials.

In Korea, most foreign desulfurization catalysts are bought and used for hydrodesulfurization.

This technique involves mixing natural gas with a small amount of hydrogen and converting sulfur into H ₂ S through a desulfurization catalyst layer at a temperature of 350 to 400 ° C, usually used by a Co-Mo catalyst supported on gamma-alumina. do.

(C ₂ H ₅ ) ₂ S + 2H ₂ = 2C ₂ H ₆ + H ₂ S

The H ₂ S produced here is adsorbed and removed by the ZnO adsorption layer.

H ₂ S + ZnO = ZnS + H ₂ S

By the above HDS process, the concentration of sulfur can be reduced to 0.1 ppm. However, sulfur compounds at 0.1 ppm concentration also adversely affect the process after HDS treatment.

Therefore, deep sulfurization is also required to extend the catalyst life or to remove the low sulfur content of less than 0.1 ppm for efficient reforming.

In addition, when used for fuel cells, in order to perform HDS, the temperature of the reactor must be raised to 350 ° C., which is necessary for desulfurization, so that the start-up time cannot be shortened, and hydrogen produced through the reformer is partially refluxed. The need to feed into the HDS reactor is complicated and the unreacted methane and by-product gases such as carbon dioxide are refluxed together, thereby reducing the overall reformer efficiency.

In addition, in situations where the reformer is not fully operational at initial start-up, this creates an additional problem of supplying pure hydrogen separately.

Therefore, desulfurization for fuel cells inevitably requires simple and efficient desulfurization technology than HDS.

Due to this necessity, desulfurization technology by adsorption has been considered in fuel reformers for fuel cells.

This technology has the advantage of being suitable for fuel cells because it can be used at room temperature or low temperature without using hydrogen.

Currently, due to the importance of this technology in foreign countries, it has been widely studied in the United States, Japan, Europe, etc., and the results have been applied for patents to protect intellectual property rights.

Osaka Gas Ltd. of Japan has been researching this field for more than 10 years, and they invented Cu-Zn manufactured by coprecipitation as a desulfurization adsorbent (US 6,042,798).

Tokyo Gas of Japan has invented activated carbon fiber adsorbents with significantly improved adsorption capacity of malodorants in fuel gas (Japanese Laid-Open Patent Publication 2001-19984).

The Phillips Peteroleum Company of the United States invented a desulfurization adsorbent consisting of ZnO, SiO ₂ , Al ₂ O ₃ , Ni and the like and applied to desulfurization of gasoline or diesel (US 6,254,766).

Tokyo Gas of Japan invented an adsorbent in which transition metals such as Ag, Fe, Co, Ni, Cu, and Zn, which have good adsorption ability of odorous dimethyl sulfide (DMS) in Japanese city gas, were supported on a hydrophobic zeolite ( Japanese Laid-Open Patent Publication 2001-286753).

However, these adsorbents are focused on the adsorption of DMS, which is a representative odorant of Japanese city gas, and thus there is a problem that the adsorption of THT and TBM which is used as odorant in domestic city gas is not efficient.

In addition, when Ag is used as a metal, the highest adsorption capacity is shown, and the adsorption capacity is lower than 2%. When low-cost Fe or Cu is used, the adsorption capacity is only 0.24% and 1.1%. There is a problem.

This problem is due to the fact that the metal component is used in the oxidized ion state, and thus the coordination bond, which is a principle of adsorption of sulfur compounds, cannot be efficiently achieved.

In order to solve such a problem, the present invention has been conducted as a result, the Fe, Co, Ni, Cu, Zn transition metals, when present in the reduced state effectively achieves the coordination bond with the sulfur compound of the odorant component significantly It was found that it can increase the sulfur compound removal technology of the domestic city gas to be achieved in the present invention.

The present invention uses a desulfurized adsorbent prepared by supporting one or more transition metals selected from Fe, Co, Ni, Cu, and Zn transition metals in a zeolite, and then calcining in a reducing atmosphere. It can be effectively removed by adsorption.

An object of the present invention is to provide a desulfurization adsorbent which can remove organic sulfur compounds in city gas by adsorption and a desulfurization method using the same.

Adsorption method for the desulfurization of city gas according to the present invention is selected from Fe, Co, Ni, Cu, Zn one or two or more transition metals are selected from the impregnation method, melting method, ion exchange method After supporting by either method, using a desulfurization adsorbent produced by firing at 300 to 800 ° C. in a reducing atmosphere using hydrogen gas, a gauge pressure of 0.01 to 10 atm and a space velocity of 100 to 50,000 at a range of -20 to 200 ° C. The sulfur compound of the city gas is removed by adsorption under the condition of h ⁻¹ .

In addition, the adsorbent for desulfurization of the city gas according to the present invention is selected from the impregnation method, melting method, ion exchange method of one or more transition metals selected from Fe, Co, Ni, Cu, and Zn. After supporting by any one method, it is characterized in that it is produced by baking at 300 ~ 800 ℃ in a reducing atmosphere using hydrogen gas. Here, the zeolite is preferably any one zeolite selected from Beta, mordenite (MOR), X, Y, ZSM-5 zeolite.

Hereinafter, a method for preparing the desulfurized adsorbent for removing organic sulfur compounds according to the present invention will be described in more detail.

In the case of the desulfurization adsorbent presented in the present invention, it can be prepared by the impregnation method, the melting method, and the ion exchange method which are used in general.

First, a metal solution is made using a source of metal. In this case, as the source material of the metal, ordinary water-soluble salts such as nitrate and sulfate acetate may be used.

The zeolite is impregnated with a solution of a source material of one or more transition metals selected from Fe, Co, Ni, Cu, and Zn.

At this time, the melting method may be used. In case of using the ion exchange method, the mixture is stirred at 80 ° C. for 24 hours, filtered and washed.

The prepared adsorbent is dried in an oven at 120 ° C. and calcined at 600 ° C. for 12 hours. At this time, firing conditions are performed in the atmosphere in which hydrogen exists.

The method for producing the desulfurized adsorbent according to the present invention described above is just one example, and other known production methods may be appropriately applied as necessary in addition to the above-described methods.

In addition, the desulfurization method using the above-described desulfurization adsorbent for city gas is as follows.

Adsorption experiments use a conventional fixed bed adsorption desulfurization apparatus manufactured by a laboratory.

First, the adsorbent is molded and pulverized to have a particle size of 1 to 2 mm, and then filled into the adsorption tube as necessary to produce a desulfurizer.

By adjusting the flow rate of the city gas so that the space velocity is 100 to 50,000 per hour, it is injected into the desulfurizer to adsorb the organic sulfur compound contained by contacting the city gas to the adsorbent so that the gas from which the sulfur component is removed flows out of the desulfurizer.

The outflow gas was measured for desulfurization ability by measuring the concentration of residual sulfur compound using on-line GC equipped with PFPD (Pulsed Flame Photometric Detector).

The city gas used in the experiment contains 2.8 and 1.2 ppm of THT and TBM as odorants, respectively.

A breakthrough curve was obtained by measuring the concentration of sulfur compounds in the effluent gas, and the time from the time when the city gas was flowed into the desulfurizer to the sulfur compound concentration was 10 ppb or more was measured as the saturation time.

The present invention will be described in more detail based on the following examples, but the present invention is not limited thereto.

Example 1

NH ₄ -Beta (SiO ₂ / Al ₂ O ₃ = 25) was prepared by impregnating a zeolite into 10% Co / Beta using a cobalt nitrate solution, and then dried at 120 ° C. for 12 hours and 12 hours at 600 ° C. Firing in a 5% H ₂ / N ₂ atmosphere finally yielded an adsorbent.

The 10% Co / Beta was formed in a pelletizer to a size of 60 to 80 mesh, and then 1 ml was taken and filled into the fixed bed adsorption tube.

At room temperature and atmospheric pressure, city gas containing 2.8 and 1.2 ppm of odorant THT and TBM, respectively, was passed through the adsorption tube at a space velocity of GHSV 6,000 h ⁻¹ , and the obtained adsorption performance is shown in Table 1 below. It was.

Example 2

NH ₄ -Beta (SiO ₂ / Al ₂ O ₃ = 25) zeolite was added to a 100 ml aqueous solution of 0.1 N iron nitrate, stirred at 80 ° C. for 24 hours, filtered, washed with distilled water, and dried at 120 ° C. for 12 hours. And calcined at 600 ° C. for 12 hours in a 5% H ₂ / N ₂ atmosphere to obtain 3% Fe / Beta by ion exchange.

In addition, the adsorption desulfurization experiment was conducted in the same manner as in Example 1, and the obtained desulfurization performance is shown in Table 1 below.

Example 3

After physically mixing the iron nitrate and the nickel nitrate reagent to the NH ₄ -Y zeolite so as to be 5% Fe-5% Ni / Y, the mixture was dried at 120 ° C. for 12 hours using a melting method and 12 hours at 600 ° C. for 5 hours. Firing in a% H ₂ / N ₂ atmosphere finally yielded an adsorbent.

In addition, the adsorption desulfurization experiment was conducted in the same manner as in Example 1, and the obtained desulfurization performance is shown in Table 1 below.

Example 4

NH ₄ -ZSM-5 (SiO ₂ / Al ₂ O ₃ = 30) zeolite was added to 100 ml of 0.1N zinc nitrate aqueous solution, stirred at 80 ° C for 24 hours, filtered, washed with distilled water, and then 12 at 120 ° C. time drying and firing at 600 ℃ in 12 hours 5% H ₂ / N ₂ atmosphere by the ion exchange method to obtain a 3% Zn / ZSM-5.

In addition, the adsorption desulfurization experiment was conducted in the same manner as in Example 1, and the obtained desulfurization performance is shown in Table 1 below.

Example 5

NH ₄ -MOR (Mordenite) zeolite was prepared by impregnation using a cobalt nitrate solution and a copper nitrate solution to 2% Co-3% Cu / MOR, and then dried at 120 ° C for 12 hours and 12 hours at 600 ° C. The adsorbent was obtained by baking in a 5% H ₂ / N ₂ atmosphere.

In addition, the adsorption desulfurization experiment was conducted in the same manner as in Example 1, and the obtained desulfurization performance is shown in Table 1 below.

Example 6

Physically mix the copper nitrate reagent with NH ₄ -Beta (SiO ₂ / Al ₂ O ₃ = 25) zeolite to 10% Cu / Beta, and then dry at 120 ° C. for 12 hours using a melting method, followed by 600 ° C. It was calcined at 5% H ₂ / N ₂ atmosphere for 12 hours at to obtain an adsorbent finally.

In addition, the adsorption desulfurization experiment was conducted in the same manner as in Example 1, and the obtained desulfurization performance is shown in Table 1 below.

Comparative Example 1

NH ₄ -Beta (SiO ₂ / Al ₂ O ₃ = 25) Prepared by impregnating zeolite to 10% Co / Beta using a cobalt nitrate solution, dried at 120 ° C. for 12 hours and 12 hours at 600 ° C. It calcined in air atmosphere and finally obtained the adsorbent.

In addition, the adsorption desulfurization experiment was conducted in the same manner as in Example 1, and the obtained desulfurization performance is shown in Table 1 below.

Comparative Example 2

NH ₄ -Beta (SiO ₂ / Al ₂ O ₃ = 25) zeolite was added to a 100 ml aqueous solution of 0.1 N iron nitrate, stirred at 80 ° C. for 24 hours, filtered, washed with distilled water, and dried at 120 ° C. for 12 hours. And calcined at 600 ° C. for 12 hours in an air atmosphere to obtain 3% Fe / Beta by ion exchange.

In addition, the adsorption desulfurization experiment was conducted in the same manner as in Example 1, and the obtained desulfurization performance is shown in Table 1 below.

Comparative Example 3

NH ₄ -Beta (SiO ₂ / Al ₂ O ₃ = 25) zeolite was dried at 120 ° C. for 12 hours and calcined at 600 ° C. for 12 hours in a 5% H ₂ / N ₂ atmosphere.

In addition, the adsorption desulfurization experiment was conducted in the same manner as in Example 1, and the obtained desulfurization performance is shown in Table 1 below.

[Comparative Example 4]

Adsorption desulfurization experiments were carried out in the same manner as in Example 1 using activated carbon (surface area: 1200 m 2 / g) as an adsorbent, and the obtained desulfurization performance is shown in Table 1 below.

division Adsorption performance TBM THT Saturation time ^a (hours) Adsorption Capacity (TBM) Saturation time ^a (hours) Adsorption Capacity (THT) Total adsorption capacity (TBM + THT) Example 1 1009.7 6.7 667.0 10.0 16.7 Example 2 1030.7 6.8 845.4 12.7 19.5 Example 3 1109.7 7.3 729.5 11.0 18.3 Example 4 935.9 6.2 648.9 9.8 15.9 Example 5 1006.6 6.6 688.7 10.4 17.0 Example 6 1102.8 7.3 828.2 12.4 19.7 Comparative Example 1 524.7 3.5 334.2 5.0 8.5 Comparative Example 2 431.2 2.8 305.6 4.6 7.4 Comparative Example 3 150.4 1.0 278.7 4.2 5.2 Comparative Example 4 32.1 0.4 41.7 1.3 1.7 ^a time when the concentration of sulfide in exhaust gas is 10ppb or more ^b adsorption capacity = weight of adsorbed sulfur compound / weight of adsorbent × 100 (%)

As shown in Table 1, in the desulfurization experiment using the adsorbent according to the present invention, all of the odorant TBM exhibited an adsorption capacity of 6% or more, and the city gas containing 1.2 ppm TBM per volume of the adsorbent at 6,000 h ⁻¹ space velocity. It showed the ability to adsorb and remove TBM for about 1,000 hours.

In the case of the odorant THT, the adsorption capacity was over 9.8%, and the city gas containing 2.8 ppm THT per volume of the adsorbent was capable of adsorbing and removing THT for 600 to 800 hours at a space velocity of 6,000 h ⁻¹ .

This is because the adsorbent according to the present invention exhibits excellent adsorption performance to THT, which accounts for 70% of the malodorants of urban gas in Korea.

In consideration of both TBM and THT, the adsorbents according to the present invention can all be found to exhibit very good adsorption performance by showing an adsorption capacity of 15% or more.

On the other hand, Comparative Examples 1 and 2, which were prepared in the same manner as in Examples 1 and 2, but fired in an air atmosphere, showed that the adsorption performance of TBM and THT fell less than half compared to Examples 1 and 2.

In addition, when using a zeolite that does not carry a transition metal as an adsorbent, TBM was saturated in only 150 hours, THT also showed only the ability to adsorb and remove about 300 hours (Comparative Example 3).

In the case of commercially used activated carbon, the desulfurization adsorption performance was lower than that of zeolite, so TBM was saturated in 30 hours, and THT showed only the ability to adsorb and remove about 40 hours (Comparative Example 4).

Therefore, it can be seen that the adsorbent according to the present invention exhibited better adsorption desulfurization performance of the city gas than conventionally used zeolites and activated carbon, and it was confirmed that there is a large difference in adsorption performance according to the firing conditions of the adsorbent. there was.

As described above, the desulfurization adsorbent produced by the above method can effectively adsorb and desulfurize organic sulfur compounds in city gas to treat city gas used for special purposes such as fuel for fuel cells.

According to the present invention, by adsorbing a city gas to an adsorbent, sulfur compounds, which are odorants in city gas, can be removed with high efficiency by adsorption.

The present invention is capable of removing sulfur compounds using a desulfurized adsorbent prepared by firing one or more transition metals selected from Fe, Co, Ni, Cu, and Zn in a zeolite and firing in a reducing atmosphere. will be.

Claims (8)

One or more transition metals selected from Fe, Co, Ni, Cu, and Zn are supported on the zeolite by any method selected from impregnation, melting, and ion exchange. Sulfur compounds of city gas by adsorption under conditions of gauge pressure of 0.01 to 10 atm and space velocity of 100 to 50,000 h ^-1 using a desulfurized adsorbent prepared by firing at 300 to 800 ° C. in a reducing atmosphere. Adsorption method for desulfurization of city gas, characterized in that to remove. One or more transition metals selected from Fe, Co, Ni, Cu, and Zn are supported on the zeolite by any method selected from impregnation, melting, and ion exchange. An adsorbent for desulfurization of urban gas, which is produced by firing at 300 to 800 ° C. in a reducing atmosphere. The adsorbent for desulfurization of a city gas according to claim 2, wherein the zeolite is any one zeolite selected from beta, mordenite (MOR), X, Y, and ZSM-5 zeolite. delete delete delete delete delete