KR100950373B1 - Method of Preparing Zinc Ferrite Catalysts using Buffer Solution and Method of Preparing 1,3-Butadiene Using Said Catalysts - Google Patents

Abstract

The present invention relates to a method for preparing a zinc ferrite catalyst using a buffer solution and a method for preparing 1,3-butadiene using the catalyst thus prepared, and more specifically, to adjusting the pH of a coprecipitation solution for preparing a zinc ferrite catalyst. In the process, the acid and base are not added separately to adjust the pH, but a zinc ferrite catalyst is prepared using a buffer solution as a co-precipitation medium, and normal-butene and normal are prepared using the catalyst thus prepared. A method for producing 1,3-butadiene by oxidative dehydrogenation of a C4 mixture comprising butane.

Zinc ferrite catalyst, buffer, normal-butene, 1,3-butadiene, oxidative dehydrogenation, C4 raffinate, C4 mixture, oxide catalyst

Description

Method for preparing zinc ferrite catalyst using buffer solution and method for preparing 1,3-butadiene {Method of Preparing Zinc Ferrite Catalysts using Buffer Solution and Method of Preparing 1,3-Butadiene Using Said Catalysts}

The present invention relates to a method for preparing a zinc ferrite catalyst using a buffer solution and a method for preparing 1,3-butadiene using the same. Specifically, a pH of a coprecipitation solution is desired by using a buffer solution as a coprecipitation medium. A zinc ferrite catalyst was prepared by coprecipitation while keeping the value constant, and an inexpensive C4 mixture containing impurities such as normal-butene or normal-butane was used as a reactant for oxidative dehydrogenation reaction. It relates to a method for producing a zinc ferrite catalyst and a method for producing 1,3-butadiene using the same, which can produce high value-added 1,3-butadiene.

The production of 1,3-butadiene with increasing demand in the petrochemical market includes naphtha cracking, direct dehydrogenation of normal-butenes, and oxidative dehydrogenation of normal-butenes. Most of 1,3-butadiene is mainly made by naphtha cracking process. It is known that the 1,3-butadiene supply ratio by the naphtha cracking process is responsible for more than 90% of the total supply, so the ability of the naphtha cracker equipment capacity in the butadiene supply situation is very significant. However, the naphtha cracking process cannot be an effective alternative to solve the supply-demand imbalance caused by the recent increase in butadiene demand, because a new naphtha cracker was created to meet the increasing demand for 1,3-butadiene by the naphtha cracking process. In addition, since the naphtha cracking process is not a sole process for producing butadiene alone, when the naphtha cracker is expanded to increase 1,3-butadiene production, other basic oils other than 1,3-butadiene are produced in excess. Because it has.

As a method for producing 1,3-butadiene by the naphtha cracking process is difficult to cope with the recent market situation as described above, by removing hydrogen from normal-butene as an alternative to 1,3-butadiene production 1 The dehydrogenation reaction to obtain, 3-butadiene has attracted attention. The dehydrogenation reaction of normal-butene includes direct dehydrogenation and oxidative dehydrogenation reaction. The direct dehydrogenation reaction of normal-butene is highly endothermic, requiring high temperature reaction conditions and thermodynamically low pressure conditions. Very low yield of 1,3-butadiene is not suitable for commercialization processes [LM Madeira, M.F. Portela, Catal. Rev., Vol. 44, p. 247 (2002)].

The oxidative dehydrogenation reaction of normal-butene is a reaction of normal-butene with oxygen to obtain 1,3-butadiene and water. After the reaction, stable water is produced, which is not only thermodynamically advantageous but also water is present. By lowering the temperature of the catalyst layer can be prevented from abrupt. Therefore, unlike naphtha cracking or direct dehydrogenation, if a catalytic process is developed to produce 1,3-butadiene with high efficiency through oxidative dehydrogenation of normal-butene, this process is performed by a single process. It can be an effective alternative to produce butadiene. In addition, when developing a catalyst that does not reduce activity even when a C4 mixture containing impurities such as normal-butane is used as a reactant, a C4 raffinate-3 or C4 mixture containing impurities such as normal-butane as a source of normal-butene Therefore, it is possible to utilize the high value of cheap surplus C4 oil. The reactant C4 raffinate-3 mixture used in the present invention is a low-cost C4 fraction remaining after sequentially separating 1,3-butadiene, isobutylene and 1-butene from a C4 mixture produced by naphtha cracking. It consists of butenes (trans-2-Butene and cis-2-Butene), normal-butane (n-Butane) and residual 1-butene (1-Butene).

It was noted that the oxidative dehydrogenation of normal-butene in the production of 1,3-butadiene is the reaction of producing 1,3-butadiene and water from oxygen and normal-butene. The oxidative dehydrogenation reaction is thermodynamically advantageous over the direct dehydrogenation of normal-butenes, so that even in mild reaction conditions, a higher yield of 1,3-butadiene can be obtained, but it is a complete oxidation reaction in that oxygen is used as a reactant. Many side reactions are expected. Therefore, the most important core technology is to develop a catalyst that can suppress such side reactions as much as possible and increase the selectivity of 1,3-butadiene. Although the reaction mechanism of the oxidative dehydrogenation reaction of normal-butene is not yet known precisely, it is known that the first step is to break the CH bond from normal-butene and the oxidation / reduction reaction of the catalyst itself occurs. Catalysts in the form of complex oxides with specific crystal structures, including metal ions with states, have been used in oxidative dehydrogenation reactions [WR Cares, J.W. Hightower, J. Catal., Vol. 23, 193 (1971)]. Until now, a catalyst known to be effective for preparing 1,3-butadiene by oxidative dehydrogenation of normal-butene is a ferrite-based catalyst [M.A. Gibson, J.W. Hightower, J. Catal., Vol. 41, p. 420 (1976) / W.R. Cares, J.W. Hightower, J. Catal., Vol. 23, p. 193 (1971) / R.J. Rennard, W. L. Kehl, J. Catal., Vol. 21, p. 282 (1971)], tin-based catalyst [Y.M. Bakshi, R.N. Gur'yanova, A.N. Mal'yan, A.I. Gel'bshtein, Petroleum Chemistry U.S.S.R., Vol. 7, pp. 177 (1967)], Bismuth Molybdate Series Catalysts [A.C.A.M. Bleijenberg, B.C. Lippens, G.C.A. Schuit, J. Catal., Vol. 4, p. 581 (1965) / Ph.A. Batist, B.C. Lippens, G.C.A. Schuit, J. Catal., Vol. 5, p. 55 (1966) / W.J. Linn, A.W. Sleight, J. Catal., Vol. 41, p. 134 (1976) / R.K. Grasselli, Handbook of Heterogeneous Catalysis, 5, 2302 (1997).

Among the complex oxide catalysts used for the oxidative dehydrogenation of normal-butene, the ferrite-based catalyst has a spinel structure at room temperature, specifically, AFe ₂ O ₄ (A = Zn, Mg, Mn, Co, Cu, etc.). ) Has a crystal structure in which O forms a cubic crystal and A and Fe are bonded to a part of the vacancy between O particles. Bid, SK Pradhan, Mater. Chem. Phys., 82, 27 (2003)]. Ferrite with spinel crystal structure has two states of oxidation and dihydration of iron ions, and from normal-butene through interaction of oxidation-reduction of iron ions with oxygen ions and gaseous oxygen, Can be used as a catalyst for oxidative dehydrogenation of 3-butadiene [MA Gibson, JW Hightower, J. Catal., Vol. 41, p. 420 (1976) / RJ Rennard, WL Kehl, J. Catal. , 21, 282 (1971)]. Generally, ferrite catalysts have different activities as oxidative dehydrogenation catalysts depending on the type of metal constituting the divalent cation site in the spinel structure, among which zinc ferrite, magnesium ferrite and manganese ferrite are oxidative dehydration of normal-butene. It is known to show good activity in the digestion reaction, in particular zinc ferrite is reported to show a higher 1,3-butadiene selectivity than other metal ferrite catalysts [F.-Y. Qiu, L.-T. Weng, E. Sham, P. Ruiz, B. Delmon, Appl. Catal., 51, 235 (1989)].

Several patents and literature have reported on the use of zinc ferrite series catalysts in connection with the oxidative dehydrogenation of normal-butenes. Specifically, it was reported that oxidative dehydrogenation of 2-Butene was carried out with a zinc ferrite catalyst present in pure spinel made by coprecipitation to obtain 1,3-Butadiene at 41% yield at 375 ° C. [ RJ Rennard, W. L. Kehl, J. Catal., 21, p. 282 (1971)]. It was also reported that 1% of 1,3-Butadiene was obtained at 420 ° C. using Zinc Ferrite catalyst using 5 mol% (5 mol% oxygen, 90 mol% helium) as a reactant using Zinc Ferrite catalyst [J.A. Toledo, P. Bosch, M.A. Valenzuela, A. Montoya, N. Nava, J. Mol. Catal. A, vol. 125, 53 (1997)].

In addition, patents and documents relating to a method for preparing a zinc ferrite catalyst that can obtain 1,3-butadiene in high yield through pretreatment and aftertreatment of a zinc ferrite catalyst have been reported [F.-Y. Qiu, L.-T. Weng, E. Sham, P. Ruiz, B. Delmon, Appl. Catal., Vol. 51, p. 235 (1989) / L.J. Crose, L. Bajars, M. Gabliks, U.S. Patent No. 3,743,683 (1973) / J.R. Baker, U.S. Patent No. 3,951,869 (1976), physically mixing other metal oxides as cocatalysts in a zinc ferrite catalyst to select normal-butene conversion and 1,3-butadiene in the oxidative dehydrogenation of normal-butene A catalyst preparation method has also been reported which increases the degree [W.-Q. Xu, Y.-G. Yin, G.-Y. Li, S. Chen, Appl. Catal. A, 89, 131 (1992)].

The catalysts reported in the literature and patents for the zinc ferrite catalyst system used in the oxidative dehydrogenation reaction are single phase zinc ferrites or mixed phase catalysts based on them, which are central to the oxidative dehydrogenation of normal-butene. Zinc ferrite, which acts as a component, is mainly produced by coprecipitation. The method of preparing zinc ferrite by coprecipitation is somewhat different according to the literature, but a method of adding a zinc precursor and an iron precursor aqueous solution to an aqueous solution of excess basic reducing agent is typical [L.J. Crose, L. Bajars, M. Gabliks, US Patent No. 3,743,683 (1973) / J.R. Baker, US Pat. No. 3,951,869 (1976).

In addition to the method of enhancing the activity of the zinc ferrite catalyst by post-firing of the catalyst, such as the preparation of the catalyst through the pretreatment, aftertreatment, and physical mixing described in the above documents, an attempt to increase the activity of the catalyst itself is performed. It has been reported in the literature that zinc, which is a cationic component, or iron, which is a trivalent cationic component, is partially substituted with other metal cations to enhance catalytic activity through modification of the spinel structure. In particular, it has been reported in the literature that catalytic activity increases when a catalyst in which iron, which is a trivalent cation component, is partially substituted with chromium or aluminum, is increased [J.A. Toledo, P. Bosch, M.A. Valenzuela, A. Montoya, N. Nava, J. Mol. Catal. A, vol. 125, p. 53 (1997) / R.J. Rennard Jr., R.A. Innes, H.E. Swift, J. Catal., 30, 128 (1973)].

In carrying out the oxidative dehydrogenation of normal-butene, when a multi-component catalyst such as a zinc-substituted zinc ferrite catalyst or a mixed phase catalyst is used, the yield of 1,3-butadiene is higher than that of the conventional zinc ferrite catalyst. However, since the constituents of the catalyst are complicated and it is difficult to secure the reproducibility of the catalyst production, it is difficult to apply as a catalyst for a commercial process. In addition, since the C4 mixture, which is a reactant used in the present invention, contains various C4 components in addition to the normal-butene, in the catalyst system having various constituents of the catalyst, side reactions due to various catalyst phases may occur, and thus the catalyst activity may be increased. Butadiene selectivity may have negative consequences.

One of the problems that can occur in the oxidative dehydrogenation process of normal-butene is that when a certain amount of normal-butane is contained in the reactants passing through the catalyst layer, the catalytic activity is lowered and the yield of 1,3-butadiene is lowered. [LM Welch, L.J. Croce, H.F. Christmann, Hydrocarbon Processing, p. 131 (1978)]. Therefore, in order to prevent such a problem, the above-mentioned prior arts use only pure butane-butene (1-butene or 2-butene) as a reactant to separate the C4 mixture, and normal-butane is also used in a commercial process using ferrite catalyst. Removed reactant is used. As such, literature or patents relating to catalysts and processes for preparing 1,3-butadiene from normal-butene via oxidative dehydrogenation reactions use pure normal-butene in a C4 mixture to use pure normal-butene as reactant. An additional separation step is required to separate and thus the economic efficiency of the 1,3-butadiene manufacturing process is greatly reduced.

In order to overcome the limitations of the prior art, the present inventors can prepare a pure single-phase zinc ferrite catalyst by coprecipitation in a coprecipitation solution having a fixed pH using a buffer solution. It has been found that low yields of 1,3-butadiene can be produced through oxidative dehydrogenation using a low cost C4 mixture comprising normal-butane and normal-butene as a reactant without a separate normal-butene separation process. On the basis of this, the present invention has been completed.

Accordingly, an object of the present invention is to provide a method for producing a zinc ferrite catalyst having a simple component, a simple synthesis route, and excellent reproducibility as a catalyst for producing 1,3-butadiene.

It is another object of the present invention to provide a method for preparing 1,3-butadiene by oxidative dehydrogenation on the catalyst using a C4 mixture directly as a reactant without a separate separation process.

The zinc ferrite catalyst for preparing 1,3-butadiene for achieving the object of the present invention is composed of pure single phase zinc ferrite prepared using a buffer solution having a pH of 6-12 as a coprecipitation medium.

Method for producing a zinc ferrite catalyst for producing 1,3-butadiene for achieving the object of the present invention, a) adjusting the amount of zinc precursor and iron precursor dissolved in distilled water; b) preparing or preparing a buffer in the desired pH range; c) coprecipitation of zinc ferrite by injecting a precursor aqueous solution into the buffer solution, d) filtering the solid precipitate from the mixed solution of the buffer solution, the precursor aqueous solution and the solid precipitate, and then drying it at 70 to 200 ° C; e) heat treating the dried catalyst at 350 to 800 ° C. to obtain a zinc ferrite catalyst.

A method for preparing 1,3-butadiene for achieving another object of the present invention includes a normal-butane on a zinc ferrite catalyst prepared by coprecipitation by injecting a precursor into a buffer solution having a pH range of 6 to 12. Consisting of producing 1,3-butadiene via oxidative dehydrogenation using a C4 mixture as reactant.

According to the present invention, a zinc ferrite catalyst having a simple composition and a synthetic route and excellent reproducibility can be prepared, and a catalyst can be prepared by a simple process of injecting a precursor aqueous solution into a buffer solution. The catalyst can be prepared easier and faster than the method.

Using the zinc ferrite catalyst prepared according to the present invention, a C4 mixture containing a high concentration of normal-butane as a reactant of an oxidative dehydrogenation reaction without a separate process of removing normal-butane (separating normal-butene) is used. High normal-butene conversions and high 1,3-butadiene yields can also be obtained by direct use, and 1,3-butadiene production by reducing the additional expenditure in the removal of normal-butane (separation of normal-butenes). The economics of the process can be improved.

According to the present invention, 1,3-butadiene having a high value in utilization in the petrochemical industry can be prepared directly from a low value C4 mixture or C4 raffinate-3, thereby achieving high value of C4 fraction. In addition, since it is possible to produce 1,3-butadiene alone without establishing a naphtha cracker, it is possible to obtain economic benefits by meeting the increasing demand for 1,3-butadiene and to actively cope with future market changes.

Hereinafter, the technical details of the present invention for achieving the above effect will be described in more detail.

As described above, the present invention provides a single phase zinc ferrite catalyst for application to the oxidative dehydrogenation reaction of normal-butene without using the process of separately adjusting the pH of the coprecipitation solution, and using a buffer solution having a fixed pH. The present invention relates to a method for preparing 1,3-butadiene by oxidative dehydrogenation of normal-butene using a catalyst prepared as described above. According to the present invention, a C4 mixture containing normal-butane is reacted with a reactant. 1,3-butadiene can be produced in high yield even when used as.

The catalyst of the present invention used to prepare 1,3-butadiene through oxidative dehydrogenation of normal-butene is a single-phase zinc ferrite catalyst, and the properties of metal cations and oxygen in the lattice vary depending on the crystal structure of the catalyst. In other words, the catalyst activity can be changed by changing the preparation conditions of the catalyst. Accordingly, the present inventors have found a method of preparing a catalyst while changing the pH of the coprecipitation solution in the process of coprecipitation of zinc ferrite, and by adjusting the pH of the coprecipitation solution by using a buffer solution for more efficient pH control, Zinc ferrite catalysts having high activity in the oxidative dehydrogenation of normal-butene were prepared.

Any zinc precursor and iron precursor for preparing the zinc ferrite catalyst may be used as long as they are commonly used precursors, and in general, it is preferable to use a chloride precursor or a nitrate precursor. Zinc chloride and zinc chloride were used as precursors of zinc and iron.

The zinc precursor and the iron precursor were quantitatively mixed so as to have an iron / zinc atomic ratio of 2, dissolved, and prepared by preparing or purchasing a buffer solution having a predetermined pH as a medium to co-precipitate zinc ferrite. When the precursor aqueous solution is injected into the prepared buffer solution using a syringe pump, zinc ferrite begins to co-precipitate. At this time, the precursor aqueous solution is injected into a sufficient amount of buffer solution so that the pH does not change. After all of the precursor aqueous solution is injected, the solution is stirred for 2 to 12 hours, preferably 6 to 12 hours, so that coprecipitation is sufficiently achieved. The phases were separated for a sufficient time so that the solid catalyst dispersed in the stirred coprecipitation solution was precipitated, and the precipitated solid sample was obtained through a vacuum filter or the like. The obtained solid sample was dried at 70 to 200 ° C., preferably at 120 to 180 ° C. for 12 to 16 hours, and the dried catalyst was placed in an electric furnace, and then 3 to 6 at a temperature of 350 to 800 ° C., preferably 500 to 700 ° C. Time heat treatment produced a pure single phase zinc ferrite catalyst.

According to the present invention, in the oxidative dehydrogenation reaction, the zinc ferrite catalyst separates hydrogen from normal-butene by the interaction of iron ions and oxygen ions in the catalyst lattice and gaseous oxygen adsorbed on the surface, and then gaseous oxygen and iron 1,3-butadiene and water are produced by further removing hydrogen through the oxidation / reduction reaction of ions. Therefore, the nature of the iron ions and oxygen and the surface of the catalyst in the catalyst lattice have a very important influence in determining its activity in the oxidative dehydrogenation of normal-butene, and according to the present invention coprecipitation solutions of different pH The zinc ferrite catalysts prepared in have different activities.

The zinc ferrite catalysts prepared in buffers of different pHs according to the preparation method of the present invention were confirmed by X-ray diffraction analysis to have different phase characteristics depending on the conditions. In the case of the catalyst co-precipitated at pH 6, zinc ferrite was formed as the main phase, but in addition, alpha-iron oxide (α-Fe ₂ O ₃ ) (III), which is known to be relatively inactive in the oxidative dehydrogenation of normal-butene, was also used. Formed (see FIG. 1). However, in the case of the catalyst co-precipitated at pH 7-12, it can be seen that the single phase zinc ferrite is formed (see FIGS. 1, 2 and 3), and the crystal phase of zinc ferrite is consistently changed with pH. have. In addition, despite the fact that the buffer solution used to achieve the desired pH was changed according to the pH, the phase structure change was consistent with pH. Therefore, the use of the buffer solution as a coprecipitation solution did not negatively affect the crystal phase formation of zinc ferrite. It was confirmed that it does not.

However, it was also confirmed that zinc ferrite was not formed and alpha-iron oxide (α-Fe ₂ O ₃ ) (III) was produced in the coprecipitation solution having a pH of 3-5. Therefore, the catalyst for preparing 1,3-butadiene of the present invention was prepared using a buffer solution having a pH range of 6 to 12 of the coprecipitation solution. However, judging from the catalytic activity, it is preferable to prepare the catalyst in the state where the pH of the coprecipitation solution is 6-10 (see Fig. 4).

Next, the present invention provides an oxidative dehydrogenation reaction on a zinc ferrite catalyst prepared in the above buffer using a C4 mixture or C4 raffinate-3 which has not been subjected to a separate normal-butane removal process as a source of reactant normal-butene. It provides a method for producing 1,3-butadiene through.

 According to the experimental examples, examples and comparative examples of the present invention, the catalyst powder is fixed in a straight pyrex reactor for catalytic reaction, and the reactor is installed in an electric furnace to maintain a constant reaction temperature of the catalyst bed. The reaction was allowed to proceed while continuously passing through the catalyst layer inside.

The reaction temperature for advancing the oxidative dehydrogenation reaction was maintained at 300-600 ° C., preferably 350-500 ° C., more preferably 420 ° C., and the injected amount of the reactants was a space velocity (GHSV: Gas Hourly Space Velocity) is 50~5000h ^-1, preferably is made to 100~1000h ^-1, more preferably the catalyst was set so that the amount 300~600h ^-1. The reactant is a mixture of C4 mixture and air and steam, the composition ratio of which is normal-butene based on normal-butene: 1: 0.5 to 10: 1 to 50, preferably 1: 3 to 4 : 10-30 were set. When the volume ratio of the mixed gas does not exceed or fall within the range of air (0.5 to 10) or steam (1 to 50) based on the normal-butene, butadiene yield of a desired degree may not be obtained, or a rapid exotherm when the reactor is operated. This is undesirable because it may cause safety problems.

In the present invention, the reaction product of the oxidative dehydrogenation reaction, normal-butene (C4 mixture or C4 raffinate-3) and oxygen, is supplied to the reactor in the form of a mixed gas, the amount of which is controlled by using a mass flow controller. In order to supply steam known to be effective in eliminating the heat of reaction of oxidative dehydrogenation reaction and improving the selectivity of 1,3-butadiene, the temperature of the water inlet portion is injected using a syringe pump with liquid water. The vapor was supplied to the reactor by vaporization by maintaining at 150 to 300 ° C, preferably 180 to 250 ° C. Steam was injected into the reactor prior to entering the furnace and allowed to pass through the catalyst bed after complete mixing with the other reactants (C4 reactant and air).

The reactant C4 mixture used in the present invention comprises 0.5-50% by weight of normal-butane, 40-99% by weight of normal-butene and 0.5-10% by weight of other C4 compounds. Such small amounts of other C4 compounds include isobutane, cyclobutane, methyl cyclopropane, isobutene and the like.

Using the zinc ferrite catalyst according to the present invention, a low-cost C4 mixture containing a high concentration of normal-butane or C4 raffinate-3, which is known to inhibit the oxidative dehydrogenation of normal-butene, is reacted with High catalytic activity and high 1,3-butadiene yields can also be obtained when used directly as a source of butene.

In addition, the present invention is a synthesis technology of a direct catalyst, rather than an assistive technology based on a conventional substitution or catalyst treatment method, and the catalyst component and the synthesis route are simple, and thus the reproducibility of the catalyst is excellent. There is an advantage that a high yield of 1,3-butadiene can be obtained from C4 mixture or C4 raffinate-3 containing impurities.

Hereinafter, the present invention will be described in more detail with reference to Preparation Examples, Experimental Examples, and Examples, but the scope of the present invention is not limited thereto.

Production Example

Precursor Aqueous Solution for Zinc Ferrite Catalyst Preparation

Zinc chloride (ZnCl ₂ ) was used as the zinc precursor, and iron chloride hexahydrate (FeCl _{3 ′} 6H ₂ O) was used as the iron precursor. Both precursors are very well dissolved in distilled water, and the respective precursors were quantified so that the Fe / Zn ratio was 2, mixed, and dissolved in water. At this time, the mixture was stirred for about 2 hours using a magnetic stirrer to obtain a sample having a uniform composition.

Preparation of buffer for the preparation of zinc ferrite catalyst

In the present invention, for the coprecipitation of zinc ferrite, a buffer solution capable of maintaining a constant pH as a coprecipitation medium was used. The buffer for preparing the zinc ferrite catalyst was prepared directly or a commercially available buffer.

The buffer solution used in the present invention can be used as long as the buffer solution has a constant pH value and does not form a precipitate other than zinc ferrite, but in the present invention, a buffer solution containing sodium tetraborate and hydrochloric acid (Borax, pH = 6, 7), a commercial buffer solution (Samjeon Chemical Co., Ltd., pH = 8, 9, 10) and a buffer solution (pH = 11, 12) mixed with sodium hydrogen carbonate and sodium hydroxide were used.

In order to co-precipitate zinc ferrite in a buffer solution having a pH of 6-7, a buffer system in which an aqueous sodium tetraborate solution and hydrochloric acid were mixed was prepared. Specifically, 57.2 grams (0.15 mol) of sodium tetraborate pentahydrate was dissolved in distilled water to prepare 1 liter of an aqueous solution of sodium tetraborate at a concentration of 0.15 mol, and hydrochloric acid was added thereto so that the pH of the solution was 6 or 7. Stir for about 2 hours to get one solution.

A commercially available buffer solution of Samjeon Chemical Co., Ltd. was used to co-precipitate zinc ferrite in a buffer solution having a pH of 8-10.

A mixed buffer solution of an aqueous sodium bicarbonate solution and an aqueous sodium hydroxide solution is used to co-precipitate zinc ferrite in a buffer solution having a pH of 11 to 12. 21.0 grams (0.25 mole) of sodium bicarbonate is dissolved in distilled water and 0.5 mole of hydrogen carbonate 0.5 liter of aqueous sodium solution was prepared, and thereto was added an aqueous sodium hydroxide solution so that the pH of the solution was 11 or 12, followed by stirring for about 2 hours to obtain a uniform solution.

Zinc ferrite ( ZnFe ₂ O ₄ ) Preparation of Catalyst

To prepare a zinc ferrite catalyst, 1.42 grams of zinc chloride and 5.61 grams of ferric chloride hexahydrate were dissolved in distilled water (250 ml), mixed, and stirred. After fully dissolving the zinc and iron precursors through sufficient stirring, the zinc ferrite was coprecipitated dropwise dropwise into a sufficient amount of buffer solution having a pH of 6-12 previously prepared. After stirring for 12 hours at room temperature using a magnetic stirrer so that the mixed solution is sufficiently stirred, it was left for 12 hours at room temperature again for phase separation. The precipitated solution was filtered through a vacuum filter and the obtained solid sample was dried at 175 ° C. for 16 hours. The resulting solid samples were heat treated for 6 hours at 650 ° C. in an electric furnace in an air atmosphere to prepare zinc ferrite catalysts at each coprecipitation pH. Phase of the prepared catalyst was confirmed by X-ray diffraction analysis, and the results are shown in FIGS. 1, 2 and 3. As shown in FIG. 1, the catalyst co-precipitated in Borax buffer at pH 6 showed zinc ferrite as the main phase but also formed part of the alpha-iron oxide (α-Fe ₂ O ₃ ) phase. However, in the case of the catalyst co-precipitated at pH 7 to 12, it was confirmed that zinc ferrite was formed in all phases regardless of the pH value (FIGS. 1, 2, and 3).

Experimental Example 1

On zinc ferrite catalyst C4 Raffinate -3 or C4  Of mixture Oxidative  Dehydrogenation reaction

The oxidative dehydrogenation of normal-butene was carried out using a zinc ferrite catalyst prepared by the method of Preparation Example, and specific reaction experimental conditions are as follows.

The reactants used in the oxidative dehydrogenation of normal-butene in the present invention are shown in Table 1 below as a composition of C4 mixture. The reactant C4 mixture was injected in the form of a mixed gas with air and steam, and the reactor was a straight fixed bed reactor made of Pyrex.

The composition ratio of the reactants was set based on the amount of normal-butene in the C4 mixture, and the volume ratio of normal-butene: air: steam was set to 1: 3.75: 15. At this time, the ratio of normal-butene: oxygen: steam is 1: 0.75: 15. Steam is a liquid water vaporized at 200 ℃ mixed with other reactants C4 mixture and air and then introduced into the reactor, the amount of C4 mixture and air is controlled through a mass flow controller, the amount of steam using a syringe pump By controlling the rate at which the liquid water is injected.

The injection rate of the reactants was reacted by setting the catalyst amount such that the space velocity (GHSV) was 475 h ⁻¹ based on the normal-butene in the C4 mixture, and the reaction temperature was maintained such that the catalyst bed temperature of the fixed bed reactor was 420 ° C. In the product after the reaction, in addition to 1,3-butadiene, which is the main product of the reaction, by-products such as carbon dioxide due to complete oxidation, cracking byproducts, and byproducts of isomerization reaction, and unreacted substances such as normal-butane contained in the reaction product Since it is included, gas chromatography was used to separate and analyze it. The conversion of normal-butene, 1,3-butadiene selectivity and 1,3-butadiene yield by oxidative dehydrogenation of normal-butene on zinc ferrite catalyst was calculated by the following equations (1), (2) and (3). .

Example 1

pH  Reaction Activity of Catalysts Prepared Using Buffers 6 and 7

X-ray diffraction analysis of the catalyst prepared using Borax buffer solution prepared at pH 6 and 7 showed that a mixed phase of zinc ferrite and alpha-iron oxide was formed in the catalyst co-precipitated at pH 6. In the catalyst co-precipitated at pH 7, a single phase zinc ferrite was formed (see FIG. 1). Table 2 shows the results of the oxidative dehydrogenation of the C4 mixture by the reaction test method of Experimental Example 1 using a catalyst co-precipitated in Borax buffer.

In the catalytic activity experiment conducted by the mixed-phase catalyst prepared at pH 6, the conversion rate of normal-butene was 71.4%, the selectivity of 1,3-butadiene was 95.2%, and the yield of 1,3-butadiene was 68.0%. Catalysts composed of a mixed phase of ferrite and alpha-iron oxide were shown to exhibit relatively good activity in oxidative dehydrogenation. In particular, the selectivity of 1,3-butadiene was found to be relatively high, because the selectivity of 1,3-butadiene was increased in the oxidative dehydrogenation reaction due to the synergy effect of each phase in the mixed-phase catalyst. .

In the catalytic activity experiment conducted with a catalyst prepared at pH 7, the conversion of normal-butene was 79.1%, 1,3-butadiene selectivity was 91.2%, and 1,3-butadiene yield was 72.1%. In the case of the catalyst, the selectivity was slightly lower than that of the mixed phase catalyst prepared at pH 6, but the conversion was greatly increased, resulting in an increased 1,3-butadiene yield.

 Example 2

pH  Reaction Activity of Zinc Ferrite Catalysts Prepared Using 8-10 Buffers

X-ray diffraction analysis of the catalyst prepared using a commercial buffer solution having a pH of 8 to 10 by the above preparation showed that all catalysts had a single phase zinc ferrite phase (see FIG. 2). Table 3 shows the results of oxidative dehydrogenation of the C4 mixture using three catalysts prepared at pH 8-10. The catalysts co-precipitated at pH 8-10 had a high normal-butene conversion of at least 78% and a high 1,3-butadiene selectivity of at least 92% and a high 1,3-butadiene yield of at least 72%, thus aiming at the present invention. It can be seen that it is preferable to use a buffer solution in the pH range of 8 to 10 for the production of high efficiency zinc ferrite catalyst.

Comparative example

pH  Reaction Activity of Zinc Ferrite Catalysts Prepared Using Buffers 11 and 12

X-ray diffraction analysis of the catalyst prepared in the sodium hydrogen carbonate-based buffer solution prepared at pH 11 and 12 in Preparation Example showed that the two catalysts prepared had a single phase zinc ferrite phase (Fig. 3). The results of oxidative dehydrogenation of the C4 mixture using two catalysts prepared using sodium hydrogen carbonate buffer solution are shown in Table 4. As shown in Table 4, although the catalysts prepared at pH 11 and 12 consisted of single phase zinc ferrite, the catalysts co-precipitated in strong basic atmosphere showed very poor catalytic activity.

Experimental Example 2

Of coprecipitation solution pH Changes in Reaction Activity of Zinc Ferrite Catalysts According to

Through Examples 1, 2 and Comparative Examples, the phase formation and catalytic properties of the zinc ferrite catalyst are determined according to the pH of the coprecipitation solution, and the fact that the activity of the oxidative dehydrogenation of normal-butene is changed is Same as one. In order to directly compare the reaction activity of the zinc ferrite catalyst according to the pH of the coprecipitation solution, the reaction results of Examples 1 and 2 and Comparative Examples are shown in FIG. 4. The yield of 1,3-butadiene showed a volcanic curve according to the pH of the coprecipitation solution and showed excellent catalytic activity in the pH range of 6-10. However, in the case of the zinc ferrite catalyst co-precipitated at pH 11-12, the zinc ferrite phase was well formed, but the reaction activity was poor, indicating that coprecipitation under basic conditions did not show a positive effect on the catalytic activity.

1 is a graph showing the results of X-ray diffraction analysis of two zinc ferrite catalysts used in Example 1 of the present invention.

2 is a graph showing the results of X-ray diffraction analysis of three zinc ferrite catalysts used in Example 2 of the present invention.

3 is a graph showing the results of X-ray diffraction analysis of two zinc ferrite catalysts used in Comparative Examples of the present invention.

Figure 4 is a graph showing the change in the activity of the oxidative dehydrogenation of C4 raffinate-3 with respect to the pH of the buffer solution during the coprecipitation of seven zinc ferrite catalysts according to Experimental Example 2 of the present invention.

Claims (7)

delete delete delete a) providing a gas mixture of C4 mixture, air and steam as a reactant; b) an oxidative dehydrogenation reaction step in which the reactant is continuously passed through a catalyst layer to which a zinc ferrite catalyst is fixed (the zinc ferrite catalyst is i) a zinc precursor having an atomic ratio of zinc to iron of 1: 2 and iron. Dissolving the precursor in distilled water; ii) coprecipitating zinc ferrite by dropwise addition of the precursor aqueous solution to a buffer solution having a pH range of 6 to 10; iii) filtering the solution mixed in step ii) to obtain a solid sample; And iv) drying the solid sample at 70 to 200 ° C. and heat treating at 350 to 800 ° C.). And, c) a method for producing 1,3-butadiene, comprising the step of obtaining 1,3-butadiene. The method of claim 4, wherein the C4 mixture comprises 0.5 to 50% by weight of normal-butane, 40 to 99% by weight of normal-butene and 0.5 to 10% by weight of the C4 mixture excluding the normal-butane and normal-butene Method for producing 1,3-butadiene, characterized in that. The method of claim 4, wherein the reactant of step a) comprises normal-butene: air: steam in a ratio of 1: 3 to 4:10 to 30. The method for preparing 1,3-butadiene according to claim 4, wherein the reaction of step b) is performed at a reaction temperature of 300 to 600 ° C. and a space velocity of 50 to 5000 h ⁻¹ based on normal-butene. .

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