KR101270093B1 - Cr-free catalysts for water gas shift reaction comprising alkali metals - Google Patents

Abstract

The present invention relates to a catalyst for non-chromium-based water gas shift reaction containing alkali metal, and more particularly, to a catalyst for water gas shift reaction, in which a catalyst composed of iron and nickel is supported with alkali metal and does not contain chromium. It relates to a catalyst for water gas shift reaction, characterized in that the complex catalyst.
According to the present invention, the catalyst composed of iron, nickel and alkali metals has a higher carbon monoxide removal effect than the conventional chromium-based catalysts in water gas shift for the removal of carbon monoxide produced through the steam reforming reaction of hydrocarbon fuels. It is safe and economical because it does not contain chromium and precious metals in the catalyst. In addition, it is also effective to suppress the production of methane that can be generated in the water gas shift reaction.

Description

Catalysts for non-chromium water gas shift reaction containing alkali metals {Cr-free catalysts for water gas shift reaction comprising alkali metals}

The present invention relates to a catalyst for non-chromium-based water gas shift reaction containing alkali metal, and more particularly, to a catalyst for water gas shift reaction, in which a catalyst composed of iron and nickel is supported with alkali metal and does not contain chromium. It relates to a catalyst for water gas shift reaction, characterized in that the complex catalyst.

The water gas shift reaction, which was originally used in ammonia synthesis processes, refers to the reaction of carbon monoxide and water (steam) on a catalyst to produce carbon dioxide and hydrogen. The biggest advantage of the water gas shift reaction is that it can be applied not only to the ammonia synthesis process but also to other fields. In particular, since it is known that the water gas shift reaction can be applied to the field of energy development technology, in recent years, research on the water gas shift reaction has been actively conducted in the field of alternative energy development technology. Many researchers have been conducting a study on the conversion of water gas to remove carbon monoxide in the product gas after hydrogen production reactions based on hydrocarbons (natural gas, natural liquefied gas, etc.) and biomaterials. In addition, the application of the gas liquefaction (GTL), biomass liquefaction (BTL), coal liquefaction (CTL) process, that is, a clean energy synthesis process.

On the other hand, the catalyst for the water gas conversion reaction may include an iron-chromium catalyst, a noble metal catalyst and the like. Iron-chromium catalysts are known to contain 1% by weight of hexavalent chromium in the catalyst after use [K. Kochloefl, "Handbook Of Heterogeneous Catalysis", Vol. 4, 1831-1843, 1997], Hexavalent chromium is very harmful to humans. Hexavalent chromium is regarded as a toxic substance in developed countries such as Europe and the United States. The use of chromium-containing electrical and electronic equipment is prohibited [Official Journal of the European Union, 46, 19-37, 2003]. In addition, in the field of catalysts, the arrival of regulations similar to those of the above-mentioned environmental regulations is expected, and it can be said that it is time to develop excellent catalysts using components that are considered to be environmentally sound. Carson and C. Mumford, "Hazardous Chemicals handbook", Vol. 2, 148-151, 2002, E. Furimsky, Catalysis Today, 30, 223-286, 1996]. Therefore, the development of a catalyst for non-chromium-based water gas shift reaction with excellent performance is very meaningful.

In the case of the noble metal catalyst which is known to exhibit high activity in the water gas conversion reaction in recent years, it is also required to develop an economical catalyst having high activity without containing a noble metal because the noble metal is very expensive.

The inventors have previously reported a three-component catalyst composed of iron, nickel, zinc or cobalt in Korean Patent No. 10-0847443 as a catalyst for removing carbon monoxide through previous studies. The catalysts disclosed in this patent have the advantage of exhibiting high activity without containing chromium as a composite catalyst in which the metals are mixed. However, there is still a need for non-chromium catalysts with higher activity and research is ongoing to improve them.

Accordingly, the present inventors have made intensive efforts to overcome the problems of the prior art, and as a result, the catalyst having an alkali metal impregnated with a catalyst made of iron and nickel has a higher removal rate of carbon monoxide than a conventional iron-chromium catalyst. It was confirmed that economic and practicality can be improved by using non-noble metals instead of expensive precious metals, and completed the present invention.

Accordingly, a main object of the present invention is to provide a catalyst for non-chromium water gas shift reactions composed of iron, nickel and alkali metals, which has a high effect on the removal of carbon monoxide and the suppression of methane production in the water gas shift reaction. .

Another object of the present invention is to provide a method for removing carbon monoxide using the catalyst for non-chromium-based water gas shift reaction containing the alkali metal.

Another object of the present invention is to provide a method for preparing a catalyst for non-chromium water gas shift reaction containing the alkali metal.

According to an aspect of the present invention, the present invention is a catalyst for water gas shift reaction, the catalyst for water gas shift reaction, characterized in that the catalyst composed of iron and nickel is an alkali metal supported and does not contain chromium To provide.

In the present invention, hydrocarbon fuels, such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), etc. are input to the reforming reaction with water, steam reforming reaction proceeds by using heat supplied through a burner or an electric furnace It is converted into reformed gas (water gas) containing a large amount of hydrogen, CO2 and CO. The catalyst of the present invention is used to remove CO from the water gas after this reforming process.

The term 'aqueous gas' used in the present invention refers to a reformed gas after the reforming reaction, and a gas mainly composed of water and carbon monoxide. Of course, this water gas contains a large amount of hydrogen, a small amount of carbon dioxide, methane, and the like, and since the gas is a reforming reaction, the expression of reformed gas is often used. In addition, the term 'water gas conversion reaction' means a reaction represented by the reaction formula [H ₂ O + CO → CO ₂ + H ₂ ], where the temperature range in which the conventional water gas conversion reaction occurs is 200-500 ℃.

In the present invention, the catalyst consisting of iron and nickel may be composed of 55-85% by weight of iron and 15-45% by weight of nickel, more preferably 60-80% by weight of iron, 20-40% by weight of nickel, Even more preferably, it may be composed of 66% by weight of iron and 34% by weight of nickel.

In the present invention, the composite catalyst is prepared by first preparing a catalyst consisting of iron and nickel and then loaded with an alkali metal, wherein the final composite catalyst is composed of 60-80% by weight of iron, 15-35% by weight of nickel, And alkali metal 1-10% by weight.

In an embodiment of the present invention, the alkali metal supported on the catalyst consisting of iron and nickel is to add the precursor of the alkali metal (eg, K ₂ CO ₃ , Cs ₂ CO ₃ ) itself to the Fe / Ni catalyst, for example In the case of a catalyst containing 5 wt% of alkali metals relative to Fe / Ni, K ₂ CO ₃ and Cs ₂ CO ₃ may be prepared by adding 5 g to 100 g of Fe-Ni. As such, it can be seen that the catalyst prepared by adding 5 g of the alkali metal precursor is about 2.82837 g for K and about 2.03943 g for Cs. That is, when looking at the metal content, iron / nickel / potassium = 63.53 / 32.73 / 3.74 (wt%) for K and iron / nickel / cesium = 64.20 / 33.07 / 2.73 (wt%) for Cs.

In the present invention, the alkali metal-supported composite catalyst is expected to be present in the surface of the alkali metal in a very small amount on the surface of the iron-nickel catalyst.

In the present invention, the alkali metal, except for hydrogen (H), alkali metal (Group 1) including lithium (Li), sodium (Na), potassium (K), rubinium (Rb), cesium (Cs) Or alkaline earth metal (Group 2), including beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba), preferably alkali metals, more preferably potassium or Cesium.

In the present invention, the metal content weight percentage of the catalyst represents the weight ratio of the respective metals in the metal catalyst to be finally obtained, and calculate the amount of precursor material based on the weight% range to use the metal precursor in the preparation of the catalyst Can be. Thus, in the case of a two-component catalyst, for example, the Fe / Ni catalyst is 66/34 (wt%), and in the case of a three-component catalyst, for example, the Fe / Ni / K catalyst is 63.53 / 32.73 / 3.74 ( wt%).

In the present invention, the catalyst may be used after steam reforming of any fuel capable of producing hydrogen by reforming fuel such as gasoline, alcohol, natural gas, kerosene, and preferably liquefied petroleum gas (LPG) and liquefied natural gas. (LNG), more preferably, is used to remove carbon monoxide produced after steam reforming of liquefied natural gas or to suppress the production of methane.

In a preferred embodiment of the present invention, when the water gas shift reaction is performed using a two-component catalyst composed of iron-nickel, the carbon monoxide reduction activity is very good, but the methanation reaction occurs to produce methane (Fig. 1). However, in the case of the iron-nickel catalyst on which the alkali metal of the present invention is supported, carbon monoxide is also reduced while suppressing the production of methane (see FIG. 2).

In a specific embodiment of the present invention, the catalytic effect of the present invention was verified by removing carbon monoxide generated after steam reforming reaction for LNG containing methane as a main component or suppressing the production of methane.

In the LNG steam reforming reaction, it is preferable that all the reaction gases produce a water gas consisting of hydrogen and carbon monoxide only through steam reforming reaction, but a small amount of methane, carbon dioxide, and water are included in the water gas undergoing the steam reforming reaction. The reaction may also be carried out by adding water in an amount based on the molar ratio of the steam reforming reaction. In this case, since the activity of the catalyst is lowered due to the generation of unwanted carbon (C), excess water may be added to the steam reforming reaction relative to the molar ratio, and this ratio is generally expressed as a C / H ₂ O ratio.

Therefore, the steam reforming reaction using LNG gas (C / H ₂ O = 1/3) composed of methane, ethane, propane, and the like may contain unreacted methane, carbon dioxide produced by water, and side reactions. Water gas is produced, which is composed of 10.0% by volume carbon monoxide, 6.7% by volume carbon dioxide, 56.7% by volume hydrogen, and 26.7% by volume water vapor (International Journal of Hydrogen Energy 28 (2003) 1387-. 1392). In Example 4 of the present invention, the carbon monoxide conversion rate of the catalyst of the present invention was measured using the reaction gas having the above composition. As a result, as shown in FIG. 2, the carbon dioxide removal effect was higher than that of the commercial catalyst (chromium-containing catalyst). In addition, as shown in FIG. 1, in the case of the conventional iron-nickel two-component catalyst, more than 1.2% of methane is produced after the conversion reaction, and when the methane is produced, the amount of hydrogen generated is reduced by that amount. On the other hand, in the case of the catalyst containing the alkali metal of the present invention, as shown in Figure 2, the concentration of methane is close to 0% can suppress the production of methane.

According to another aspect of the present invention, the present invention administers water gas to a reactor comprising the catalyst and at a temperature of 150-500 ° C. at a space velocity of 2,000 to 100,000 ml-water gas / g-catalyst time. It provides a method for removing carbon monoxide comprising performing a water gas shift reaction.

In the present invention, the carbon monoxide in the reaction gas (aqueous gas) is converted to carbon dioxide and hydrogen by reacting with water on the catalyst packed in the reactor, the carbon monoxide is removed through this reaction process.

According to another aspect of the present invention, the present invention provides a method for preparing a catalyst for a water gas shift reaction, comprising the following steps:

a) mixing the iron precursor and the nickel precursor in distilled water;

b) adding and leaving an aqueous solution mixed with distilled water and sodium hydroxide until the mixture reaches pH 8-9;

c) separating the precipitate produced after the standing with a vacuum separator and washing with distilled water;

d) heat treating the resultant at 200 to 800 ° C. to produce an iron-nickel catalyst;

e) supporting 1 to 10% by weight of potassium or cesium precursor with respect to the iron-nickel catalyst by impregnation; And

f) heat treating at 200 to 800 ° C. after the supporting to obtain a complex catalyst loaded with potassium or cesium.

In an embodiment of the present invention, the metals used in the preparation of the catalyst were used as precursor forms, and the preparation of metal catalysts using metal precursors is a common catalyst preparation method in the art (Catalyst Introduction, Transfer Agent, Seogon, Fourth) Edition, Book Publishing Hallym). The reason for using these metal precursors is that the metals in the oxide form are not easy to mix, so they are prepared using the metal precursor form to facilitate the mixing in the aqueous solution. And relatively inexpensive.

The precursor in the form of the nitrate used in the present invention is a preferred precursor in the preparation of a catalyst because it is well soluble in H ₂ O (distilled water), and mixing them in an aqueous solution is for mixing the precursor. The reason for the pH control (using sodium carbonate and sodium hydroxyde) in particular is to obtain a solid material in the form of an oxide catalyst. At this time, a precipitate (sink solid material) is generated in the aqueous solution, and not only the desired catalytic material but also sodium (Sodium, Na) is present. Therefore, the sediment is separated and obtained, and the precipitate is washed with distilled water. The reason for drying the solid material obtained through this process at 110 ° C. is to completely remove H ₂ O in the solid material. Finally, the reason for the calcination at 500 ° C. is to obtain a metal catalyst in the form of a stable oxide and to remove unwanted substances.

In the present invention, the impregnation method may be a method of impregnating an iron-nickel catalyst in an aqueous solution in which potassium or cesium precursors are dissolved according to a method known in the art.

As described above, the catalyst composed of iron, nickel and alkali metal prepared according to the present invention is conventional in the water gas shift reaction for the removal of carbon monoxide generated through the steam reforming reaction of liquefied natural gas or liquefied petroleum gas It shows higher carbon monoxide removal effect than iron-chromium catalyst and is safe and economical because it does not contain chromium and precious metals. In addition, in the case of the iron-nickel catalyst, which is a non-chromium catalyst, a small amount of methane may be produced in the water gas shift reaction. The iron-nickel catalyst containing the alkali metal of the present invention is effective in suppressing the production of methane.

1 is a graph showing the volume% of carbon monoxide and methane in the product gas of a commercial catalyst and an iron-nickel catalyst under conditions of 400 ° C. and 25,000 ml-reaction gas / g-catalyst time.
2 shows a commercial catalyst at 400 ° C., 25,000 ml-reaction gas / g-catalyst time, and potassium / iron-nickel and cesium / iron at 400 ° C., 30,000-37,500 ml-reaction gas / g-catalyst time. -Graph showing volume percentage of carbon monoxide and methane in the product gas of nickel catalyst.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and the scope of the present invention is not to be construed as being limited by these examples.

Metal Precursors Used in Catalysis

The metals used in the catalyst preparation were used in the form of metal precursors. Precursors in the form of iron (Fe (NO ₃ ) ₃ 9H ₂ O), nickel (Ni (NO ₃ ) ₂ 6H ₂ O), potassium (K ₂ CO ₃ ) and cesium (Cs ₂ CO ₃ ) were used. The product was used.

Example 1 Preparation of Iron-Nickel (66-34 wt.%) Catalyst

Iron nitrate nonahydrate (Iron (III) nitrate nonahydrate, manufactured by Aldrich) was used as the iron precursor, and nickel nitrate hexahydrate (Nickel (II) nitrate hexahydrate, manufactured by Aldrich) was used as the nickel precursor. After mixing 390 ml of distilled water, 53.9 g of the iron precursor, and 19.4 g of the nickel precursor, an aqueous solution of 200 ml of distilled water and 20 g of sodium hydroxide (manufactured by Aldrich) was added until the pH was 8.5. It was left for hours. The precipitate produced in the mixed solution was separated using a vacuum separator, and the precipitate was washed three times or more with distilled water in order to remove sodium ions remaining in the precipitate. The precipitate thus obtained was dried in an 110 ° C. oven for 24 hours, and the dried solid was heat-treated in a 500 ° C. electric furnace for 5 hours to prepare an iron-nickel (66-34 wt%) catalyst.

Example 2 Preparation of Iron-Nickel (66-34 wt.%) Catalysts Containing Potassium

Potassium carbonate (Potassium carbonate, manufactured by Aldrich) was used as the potassium precursor. 1 g of the iron-nickel (66-34 wt%) catalyst prepared by the method of Example 1 was loaded with 0.5 ml of an aqueous solution in which 0.05 g of the potassium precursor was dissolved using an impregnation method. It was dried in an oven at 24O < 0 > C for 24 hours, and the dried solid was heat-treated for 5 hours at a 500C electric furnace to prepare an iron-nickel (66-34 wt%) catalyst containing potassium.

Example 3 Preparation of Iron-Nickel (66-34 wt.%) Catalysts Containing Cesium

Cesium carbonate (Cesium carbonate, manufactured by Aldrich) was used as the cesium precursor. Prepared in the same manner as in Example 2, 1 g of the iron-nickel (66-34% by weight) catalyst prepared in Example 1 and 0.5 g of an aqueous solution in which 0.05 g of cesium carbonate was dissolved were used.

Example 4 Water Gas Conversion Reaction to Remove Carbon Monoxide after Steam Reforming of Liquefied Natural Gas

Using catalysts prepared in Examples 1, 2 and 3 and commercially available catalysts (Johnson Matthey, Model: 71-5M, Fe / Cr / Cu = 90/8/2 (wt%)) A water gas shift reaction was performed using a reaction gas mixed with carbon monoxide, carbon dioxide, hydrogen, and water vapor. The composition of the gas used in the reaction consists of 10.0 vol% carbon monoxide, 6.7 vol% carbon dioxide, 56.7 vol% hydrogen, and 26.7 vol% water vapor.

A water-type stainless steel reactor was installed in the electric furnace for the water gas conversion reaction, and the reaction temperature was kept constant through the temperature controller. The reaction proceeded continuously while passing the catalyst layer in the reactor. The amount of carbon monoxide, carbon dioxide and hydrogen used in the reaction was controlled using a mass flow controller, and the amount of water vapor was controlled by adjusting the injection rate of the syringe pump containing water. The gas hourly space velocity (GHSV) of the reactants was set at 25,000-37,500 ml-reaction gas / g-catalyst time. The water vapor is injected in the form of water, and the reaction device is designed so that the water is directly vaporized with water vapor at 100 ° C. or higher to be completely mixed with other reactant gases and introduced into the reactor. Water gas shift reaction was carried out at 400 ℃.

Product type and amount were analyzed by gas chromatography (Gas Chromatography), Porapak Q was used as an analysis column. The conversion rate of carbon monoxide was calculated using the formula (moles of CO removed / moles of supplied CO) * 100.

1 is a graph showing the volume% of carbon monoxide and methane in the product gas of a commercial catalyst and an iron-nickel catalyst under conditions of 400 ° C. and 25,000 ml-reaction gas / g-catalyst time.

In Figure 1, looking at the content of carbon monoxide in the product gas using the catalyst of the present invention, the iron-nickel (66-34% by weight) catalyst containing no chromium is lower than that of the commercial catalyst (chromium-containing catalyst) It can be seen that it provides a carbon monoxide content. However, it can be seen that methane is contained 1.0 vol% or more in the product gas. These methanes are produced from hydrogen, meaning that the amount of hydrogen is reduced when methane is produced.

2 shows a commercial catalyst at 400 ° C., 25,000 ml-reaction gas / g-catalyst time, and potassium / iron-nickel, 37,500 ml-reaction gas at 400 ° C., 30,000 ml-reaction gas / g-catalyst time. It is a graph showing the volume% of carbon monoxide and methane in the product gas of the cesium / iron-nickel catalyst under the condition of / g-catalyst time.

In Figure 2, looking at the contents of carbon monoxide and methane in the product gas using the catalyst of the present invention, the iron-nickel (66-34 wt%) catalyst containing 5 wt% of potassium or cesium is a commercial catalyst (chrome) It can be seen that in addition to providing a lower carbon monoxide content as compared to the (containing catalyst), the volume% content of methane in the product gas is almost zero.

In the above results, the iron-nickel composite catalyst containing potassium or cesium according to the present invention is more effective in removing carbon monoxide than conventional commercial catalysts containing chromium, and generates almost methane as compared to iron-nickel catalysts. It can be seen that there is an advantage that does not.

Claims (7)

A catalyst for water gas shift reaction, wherein the catalyst for water gas shift reaction is a complex catalyst in which potassium or cesium is supported on a catalyst composed of iron and nickel and does not contain chromium.
The catalyst of claim 1 wherein the catalyst consisting of iron and nickel is comprised of 55-85 weight percent iron and 15-45 weight percent nickel.
The catalyst of claim 1, wherein the composite catalyst comprises 60-80 wt% iron, 15-35 wt% nickel, and 1-10 wt% potassium or cesium.
delete The catalyst according to claim 1, wherein the catalyst is used to remove carbon monoxide generated after steam reforming of liquefied natural gas or to suppress the production of methane.
A water gas is administered to a reactor comprising the catalyst according to any one of claims 1 to 3 and 5 and a space velocity of 2,000 to 100,000 ml-water gas at a temperature of 150-500 ° C. A method for removing carbon monoxide, comprising performing a water gas shift reaction with a / g-catalyst time.
Method for producing a catalyst for water gas shift reaction comprising the following steps:
a) mixing the iron precursor and the nickel precursor in distilled water;
b) adding and leaving an aqueous solution mixed with distilled water and sodium hydroxide until the mixture reaches pH 8-9;
c) separating the precipitate produced after the standing with a vacuum separator and washing with distilled water;
d) heat treating the resultant at 200 to 800 ° C. to produce an iron-nickel catalyst;
e) supporting 1 to 10% by weight of potassium or cesium precursor with respect to the iron-nickel catalyst by impregnation; And
f) heat treating at 200 to 800 ° C. after the supporting to obtain a complex catalyst loaded with potassium or cesium.

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