KR100685658B1 - Copper ferrite catalyst and decomposition of sulfur trioxide using the same - Google Patents

Abstract

A sulfur trioxide decomposing highly stable catalyst which exhibits higher activity than existing catalysts, and has high reaction activity at a temperature of 700 deg.C, more preferably at a high temperature of 800 deg.C or more is provided. A copper ferrite catalyst is represented by a formula of Fe(2+delta)Cu(1-delta)O4, wherein the delta is more than or equal to 0 and less than 1. The copper ferrite catalyst is supported on a support. The support is selected from silica, alumina, zirconia and titania. A decomposition process of sulfur trioxide is performed at a temperature of 500 to 1200 deg.C under a pressure of 0.1 to 40 atmospheric pressures. The decomposition process is performed at a temperature of 700 to 1000 deg.C under a pressure of 1 to 25 atmospheric pressures. The decomposition process is used in an IS(Iodine-Sulfur) cycle process for water decomposition.

Description

Copper ferrite catalyst and decomposition method for sulfur trioxide using same {COPPER FERRITE CATALYST AND DECOMPOSITION OF SULFUR TRIOXIDE USING THE SAME}

1 is a Mossbauer analysis of the copper ferrite catalyst of the present invention;

2 is a graph showing a comparison of sulfur trioxide conversion of various ferrite catalysts;

3 is a graph showing sulfur trioxide conversion of various Ni, Co, Fe supported catalysts.

The present invention relates to a copper ferrite catalyst, and more particularly to a catalyst which acts on a reaction for decomposing SO ₃ to produce SO ₂ and oxygen.

The Iodine-sulfur (IS) cycle process is disclosed in US Pat. No. 4,089,940 and occurs through the following reaction scheme.

H ₂ SO ₄ → SO ₂ + H ₂ O + 1/2 O ₂

SO ₂ + I ₂ + 2H ₂ O → 2HI + H ₂ SO ₄

2HI → I ₂ + H ₂

As shown in the above scheme, first, sulfuric acid decomposition reaction is performed at about 700 ° C. to generate sulfur dioxide and oxygen, and the produced sulfur dioxide reacts with iodine to be converted into iodic acid and sulfuric acid by Bunsen reaction, and the sulfuric acid produced is Circulated by sulfuric acid decomposition. The separated iodic acid is divided into hydrogen and iodine through a decomposition reaction in the iodic acid reactor, and the generated iodine is circulated back to the Bunsen reactor. Eventually, it constitutes a waste cycle that breaks down water to produce water and oxygen.

In connection with the reaction, US Pat. No. 3,888,750 suggests that sulfuric acid reacts at 400 to 950 ° C. by catalytic reaction and the supported platinum catalyst can be used in the temperature range of 750 ° C.

In addition, U.S. Patent No. 4,314,982 suggests that the sulfuric acid decomposition reaction is divided into two reactions below to use a different catalyst for each reaction.

H ₂ SO ₄ → SO ₃ + H ₂ O

SO ₃ → SO ₂ + 1 / 2O ₂

For example, at 427 to 697 ° C, a catalyst in which platinum is supported on TiO ₂ (Titania) or barium sulphate, and at higher temperatures, an iron catalyst supported on titania and a copper catalyst supported on zirconia are presented.

Cr₂O₃>Fe₂O₃>CuO >CeO₂>NiO>Al₂O₃의 순으로 촉매활성의 강약을 기술하였고, 도키야(Bull. of The Chemical Society of Japan, 50(10) (1977) 1657 참고)등은 Fe₂O₃>Cr₂O₃>CuO>CeO₂ >NiO>Al₂O₃의 순으로 촉매활성을 기술하였다.Subsequently, a study on sulfuric acid decomposition catalysts was carried out for each catalyst oxide, and Tagawa / endo (see Int. J. Hydrogen Energy, 14 (1) (1989) 11) was Pt.

The strength and weakness of catalytic activity were described in order of Cr ₂ O ₃ > Fe ₂ O ₃ >CuO> CeO ₂ >NiO> Al ₂ O ₃ , and Tokiya (Bull. Of The Chemical Society of Japan, 50 (10) (1977) 1657) described the catalytic activity in the order of Fe ₂ O ₃ > Cr ₂ O ₃ >CuO> CeO ₂ >NiO> Al ₂ O ₃ .

Therefore, recently, the sulfuric acid decomposition reaction has been tended to be divided into a reaction of converting sulfuric acid into sulfur trioxide and water and a reaction of converting sulfur trioxide into sulfur dioxide, as shown in US Pat. No. 4,314,982. Therefore, in the above method, there has been a need to develop a low cost, high stability catalyst other than a noble metal as a catalyst for decomposition reaction of sulfur trioxide which is usually performed at 700-950 ° C. Conventional single-phase catalysts have problems in terms of long-term stability due to sintering at high temperatures, and catalysts optimized for direct decomposition of sulfuric acid are not suitable for decomposition of sulfur trioxide.

Accordingly, an object of the present invention is to provide a catalyst for decomposition of sulfur trioxide having high activity at high temperatures of 700 ° C. or higher, more preferably 800 ° C. or higher while showing higher activity than conventional catalysts.

The present invention provides a copper ferrite catalyst having the following general formula (1) to achieve the above technical problem:

Fe _{(2 + δ)} Cu _(1-δ) O ₄

δ〈1, 바람직하게는 0.1

δ

0.9의 범위이다. Wherein δ is 0

δ <1, preferably 0.1

δ

It is in the range of 0.9.

The copper ferrite catalyst according to the present invention can be manufactured by various methods such as a solid phase method, a coprecipitation method, a spray method, a sol gel method, a microwave method, and the activity thereof is higher than that of a copper oxide, an iron oxide catalyst or a mixture thereof. Outstanding in

The catalyst according to the present invention may be used in the form of being supported on a carrier, but may be molded and used directly into pellets without being supported. In the case of supporting, the supporting body may be silica, alumina, zirconia, titania, and the like, and it is most stable when supported on titania.

The catalyst of the present invention has sulfur trioxide decomposition activity, and has excellent activity and stability in the temperature range of 500-1200 ° C., in particular, in the range of 700-1000 ° C., 0.1-40 atm, especially in the range of 1-25 atm. The space velocity of the reactants fed to the reaction can be used in the range of 100-500,000 mL / gcat · h, in particular in the space velocity range of 500-100,000 mL / gcat · h.

Most catalysts at high temperatures cause sintering to reduce the surface area, making it difficult to maintain the activity of the catalyst. Therefore, the ferrite-structured catalyst according to the present invention also has a small surface area that is difficult to measure when subjected to prolonged treatment at a high temperature, but the specific surface area Compared with the supported iron oxide or copper oxide catalyst of 10 m ² / g or more, the activity is very high and the long-term stability is also very high. It is interpreted that the copper oxide having high activity while maintaining a stable structure is well distributed on the iron oxide having high activity, so that the high activity and high temperature stability of the catalyst are simultaneously secured.

Hereinafter, an Example is given and this invention is demonstrated more concretely.

Preparation of the catalyst

<Example 1>

8.067 g of CuCl ₂ was dissolved in 100 mL of distilled water, and 19.4652 g of FeCl ₃ was dissolved in 100 mL of distilled water. After the two solutions were mixed for 5 minutes in a 1000 mL three-necked flask, an alkali solution in which 20 g of NaOH was dissolved in 100 mL of distilled water was added thereto, followed by a coprecipitation reaction. The pH of the solution was adjusted to 10, followed by stirring for 5 hours, and the co-precipitate was filtered and washed, dried in a drier for 12 hours, and then ground. The milled solid was then calcined at 900 ° C. for 16 hours to produce the desired copper ferrite.

Mossbauer analysis of the prepared copper ferrite is shown in Figure 1 and Table 1.

As a result of the analysis, the catalyst of the present invention shows that the iron content of the A site is higher than that of the B site when expressed in the form of ABO ₂ , indicating that the copper is a typical inverted spinel structure mainly distributed in the B site. .

<Example 2>

In the same manner as in Example 1, copper ferrite (Fe _{(2 + δ)} Cu _(1-δ) O ₄ ) was prepared by varying the content of copper (δ: 0.3, 0.5, 0.7), which was obtained from Mossbauer. The results of the analysis also confirmed that it has a reverse spinel structure.

Comparative Example 1

Cobalt manganese ferrite, nickel ferrite and strontium ferrite were prepared in the same manner as in Example 1 using nickel, cobalt, manganese and strontium compounds instead of copper compounds, and the structure thereof was confirmed by XRD and Mossbauer analysis.

Comparative Example 2

Similar to Example 1, cobalt, copper, nickel, and iron oxides were supported on Al ₂ O ₃ or TiO ₂ by coprecipitation to form CoO / Al ₂ O ₃ , CoO / TiO ₂ , NiO / TiO ₂ , NiO / Al _2. O ₃ , CuO / Al ₂ O ₃ , CuO / TiO ₂ , Fe ₂ O ₃ / Al ₂ O ₃ , Fe ₂ O ₃ / TiO ₂ catalysts were prepared. At this time, the catalyst component and the supporting alumina or titania were prepared in a 1: 1 molar ratio, ammonia was used as a precipitant, and the catalyst was calcined at 800 ° C. for 3 hours.

Sulfur trioxide decomposition performance evaluation

<Example 3>

The activity of the catalyst on the decomposition of sulfur trioxide in a fixed bed reactor was evaluated. Sulfur trioxide was supplied to the reactor at a flow rate of 20 mL / min and nitrogen at 40 mL / min, and the experiment was carried out while varying the amount of catalyst to 0.5 g, 0.2 g, and 0.05 g. The product was passed through 250 ml of 0.4 N iodine solution and also through 500 mL dilute sulfuric acid. In iodine solution, sulfur trioxide was converted to sulfuric acid and sulfur trioxide, which was not collected in iodine solution, was mostly collected in dilute sulfuric acid solution. The amount of sulfur dioxide in the product was analyzed by the remaining amount of iodine, and the unreacted sulfur trioxide was calculated by measuring the amount of acid by acidic titration of iodine solution and the weight change of the diluted solution.

In FIG. 2, when the amount of the catalyst is 0.05 g, the reaction activity of the catalysts prepared in Example 1 and Comparative Example 1 (GHSV: 72,000 mL / gcat.h) was measured according to temperature.

It can be seen from FIG. 2 that the copper ferrite catalyst according to the present invention has the highest decomposition activity of sulfur trioxide.

<Example 4>

The same experiment as in Example 3 was carried out using the catalyst prepared in Example 2. The results are shown in Table 2 below.

From Table 2, it can be seen that in the copper ferrite structure according to the present invention, the change in conversion according to the content of δ is not large.

<Example 5>

The reaction activity of the catalyst obtained in Comparative Example 2 was measured by the method of Example 3, in which case 0.5 g of a catalyst was used.

The measured results are shown in FIG. 3 and Table 3 below.

It can be seen from the above Table 3 and FIG. 3 that the copper ferrite catalyst according to the present invention shows an excellent catalytic activity compared to other catalysts.

The catalyst of the present invention can be usefully used in sulfuric acid decomposition reactions, particularly in sulfur trioxide decomposition processes.

Claims (8)

Copper ferrite catalyst of formula Fe _{(2 + δ)} Cu _(1-δ) O ₄ Where δ is 0

δ <1. The method of claim 1, δ is 0.1

δ

Copper ferrite catalyst, characterized in that 0.9. The method of claim 1, Copper ferrite catalyst, characterized in that supported on the support. The method of claim 3, wherein Copper ferrite catalyst, characterized in that the support is selected from silica, alumina, zirconia and titania. A method of decomposing sulfur trioxide in the presence of the catalyst of claim 1. The method of claim 5, The process is characterized in that it is carried out at a temperature of 500 to 1200 ℃ and 0.1 to 40 atm. The method of claim 6, The process is characterized in that it is carried out at a temperature of 700 to 1000 ℃ and 1 to 25 atm. The method of claim 5, Characterized in that it is used in the Iodine-Sulfur (IS) cycle process for water decomposition.

Images