Mixed manganese ferrite coated catalyst, method of preparing the same, and method of preparing 1,3-butadiene using the same

Abstract

This invention relates to a method of preparing a mixed manganese ferrite coated catalyst, and a method of preparing 1,3-butadiene using the same, and more particularly, to a method of preparing a catalyst by coating a support with mixed manganese ferrite obtained by co-precipitation at 1040 C. using a binder and to a method of preparing 1,3-butadiene using oxidative dehydrogenation of a crude C4 mixture containing n-butene and n-butane in the presence of the prepared catalyst. This mixed manganese ferrite coated catalyst has a simple synthetic process, and facilitates control of the generation of heat upon oxidative dehydrogenation and is very highly active in the dehydrogenation of n-butene.

Claims

1. A method of preparing a mixed manganese ferrite coated catalyst for use in preparing 1,3-butadiene, comprising: a) co-precipitating a precursor aqueous solution comprising a manganese precursor and an iron precursor while being mixed in a basic solution, thus forming a co-precipitated solution; b) washing and filtering the co-precipitated solution, thus obtaining a solid sample of mixed manganese ferrite which is then dried at 70200 C.; c) mixing the dried solid sample of mixed manganese ferrite, a binder of alumina, distilled water and an acid at a weight ratio of 1:11,5: 810:0.40.6 at room temperature, thus obtaining a mixture, wherein said alumina is boehmite and the acid is selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid and phosphoric acid; and d) adding a support to the mixture obtained in c) and then performing blending and drying, wherein said drying is performed at 5080 C., and the support is silicon carbide.

2. The method of claim 1, wherein amounts of the manganese precursor and the iron precursor are adjusted so that an atom ratio of iron/manganese is 2.02.5.

3. The method of claim 1, wherein the precursor aqueous solution is co-precipitated while being mixed in a 1.54,0 M basic solution at 1040 C.

4. The method of claim 1, further comprising heat treating the solid catalyst dried in d) at 350800 C.

5. The method of claim 1, wherein the support is a spherical or cylindrical support having a size of 110 mm.

6. The method of claim 1, wherein the support is used in an amount 515times the weight of the dried solid sample.

7. The method of claim 1, wherein the alumina has a specific surface area of 70250m.sup.2/g.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustrates the reaction results of Test Example 1 as shown in Table 3 according to the present invention.

MODE FOR THE INVENTION

(2) Hereinafter, a detailed description will be given of the present invention.

(3) The present invention pertains to the preparation of a mixed manganese ferrite coated catalyst for use in the oxidative dehydrogenation of n-butene, by synthesizing mixed manganese ferrite using co-precipitation at 1040 C., particularly 1530 C., and then coating a support with the mixed manganese ferrite using a binder, and to a method of preparing 1,3-butadiene via the oxidative dehydrogenation of n-butene using the catalyst thus prepared. As such, 1,3-butadiene can be prepared from a C4 mixture which was not subjected to additional n-butane separation.

(4) The mixed manganese ferrite coated catalyst according to the present invention for preparing 1,3-butadiene in high yield using the oxidative dehydrogenation of n-butene is obtained by coating a support having high heat conductivity with mixed manganese ferrite which is an active material, so that the amount of mixed manganese ferrite per the unit volume of the catalyst is small, thus facilitating control of the generation of heat and exhibiting higher activity and productivity for the oxidative dehydrogenation of n-butene.

(5) A manganese precursor and an iron precursor for synthesizing the manganese ferrite include a chloride precursor or a nitrate precursor, which dissolves well in distilled water which is useful as the solvent. Specifically, the iron precursor is selected from the group consisting of ferrous chloride tetrahydrate, ferrous chloride hexahydrate, ferrous chloride dihydrate, ferric chloride hexahydrate, ferrous nitrate hexahydrate, ferrous nitrate nonahydrate, ferric nitrate hexahydrate, and ferric nitrate nonahydrate.

(6) The manganese precursor is selected from the group consisting of manganous chloride, manganous chloride tetrahydrate, manganic chloride, manganese tetrachloride, manganese nitrate hexahydrate, manganese nitrate tetrahydrate, and manganese nitrate monohydrate.

(7) The amounts of the manganese precursor and the iron precursor are adjusted so that the atom ratio of iron/manganese is 2.02.5, and these precursors in such amounts are respectively dissolved in distilled water, and then mixed together. If the atom ratio of iron/manganese falls outside of 2.02.5, manganese is difficult to interpose into iron lattices, or the activity of the catalyst decreases drastically.

(8) In order to co-precipitate the manganese precursor and the iron precursor at room temperature, a 1.54 M basic solution, for example, a 3 M sodium hydroxide aqueous solution, is separately prepared. If the concentration of the basic solution is less than 1.5 M, it is difficult to form a mixed manganese ferrite catalyst structure. In contrast, if the concentration thereof is higher than 4 M, in the case of a metal ion combined with a hydroxyl group, for example, sodium hydroxide, it is difficult to remove a Na ion upon washing, undesirably decreasing the activity. The case where the molar concentration of the basic solution is adjusted to within the range of 23 M is useful in terms of forming a mixed manganese ferrite structure and performing post-treatment. The basic solution used for co-precipitating the manganese precursor and the iron precursor may include another type of basic solution including ammonia water, in addition to sodium hydroxide. The pH of the basic solution may fall in the range of 914.

(9) To obtain the mixed manganese ferrite from the manganese precursor and the iron precursor, the aqueous solution in which the manganese precursor and the iron precursor were dissolved is introduced into the basic solution at 1040 C. Stirring is performed for 212 hours, in particular 612 hours so that the introduction rate is maintained uniform and sufficient co-precipitation takes place.

(10) If the co-precipitation is carried out at a temperature lower than 10 C., it becomes insufficient thus forming very unstable bonds, undesirably causing side-reactions which are difficult to control upon using a catalyst. If the temperature is higher than 40 C., the catalytic activity may deteriorate. The co-precipitation may be carried out at 1530 C., particularly 1525 C.

(11) The stirred co-precipitation solution is phase separated for a sufficient period of time so that the solid catalyst precipitates, after which washing and filtering under reduced pressure are performed, after which a precipitated solid sample is obtained.

(12) The solid sample thus obtained is dried at 70200 C., particularly 120180 C. for 24 hours, thus preparing mixed manganese ferrite.

(13) The binder used to coat a support with the dried mixed manganese ferrite may include alumina having a specific surface area of 70250 m.sup.2/g. This alumina may use boehmite or alumina sol as a precursor, and boehmite is particularly useful.

(14) In the coating of the support with the mixed manganese ferrite, an acid is added to gel boehmite, and may be selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and acetic acid.

(15) The support which will be coated with the mixed manganese ferrite may be selected from the group consisting of silicon carbide, alumina or silica. Particularly useful is silicon carbide. The size and the shape of the support may vary depending on the size of a reactor used for the reaction, and are not limited but a spherical or cylindrical support having a size of 110 mm may be used.

(16) The mixed manganese ferrite, boehmite, distilled water and nitric acid are mixed at a weight ratio of 1:0.52:612:0.30.8, particularly 1:11.5:810:0.40.6. To this mixture, the support is added in an amount 515 times, particularly 1012 times the weight of mixed manganese ferrite, and blended using a roll mixer and dried at 5080 C., thus obtaining a mixed manganese ferrite coated catalyst.

(17) The dried mixed manganese ferrite coated catalyst is placed in an electric furnace and heat treated at 350800 C., particularly 500700 C.

(18) In the present invention, the X-ray diffraction peaks of the mixed manganese ferrite used as the active material have the 2-theta range of 18.7818.82, 24.1824.22, 33.233.24, 35.6435.68, 40.940.94, 45.2245.26, 49.5649.6, 54.2254.26, 55.2455.28, 57.9257.96, 62.5662.6, 64.0464.08, 66.0266.06, 72.1672.2, and 75.7875.82. The most remarkable peak is observed in the 2-theta range of 33.233.24.

(19) In addition, the present invention provides a method of preparing 1,3-butadiene using a C4 mixture, which was not subjected to additional n-butane separation, as the supply source of n-butene via oxidative dehydrogenation in the presence of the mixed manganese ferrite coated catalyst which was co-precipitated at room temperature. The C4 mixture is selected from the group consisting of 1-butene, 2-butene, and C4 raffinates-1, 2, 2.5, 3.

(20) In Test Example 1 according to the present invention, a powder of the catalyst is fixed to a straight type stainless steel reactor for the catalytic reaction, and the reactor is placed in an electric furnace so that the reaction temperature of the catalyst bed is maintained constant, after which the reactants are reacted while continuously passing through the catalyst bed of the reactor.

(21) The reaction temperature for oxidative dehydrogenation is maintained at 300600 C., particularly 350500 C., more particularly 400 C. The amount of the catalyst is set so that the WHSV (Weight Hourly Space Velocity) as the flow rate of reactants, is 15 h.sup.1, particularly 23 h.sup.1, more particularly 2.5 h.sup.1, based on n-butene. The reactants include the C4 mixture and the air and the steam at a ratio of 1:0.510:150, particularly 1:24:1030. If the mixing ratio of the gas mixture falls outside of the above range, a desired butadiene yield cannot be obtained, or problems may occur due to drastic heat generation when the reactor is operated.

(22) In the present invention, n-butene and oxygen which are reactants for the oxidative dehydrogenation are supplied in the form of a gas mixture, and the amounts of the C4 mixture or the C4 raffinate-3 which is the supply source of n-butene and the air which is another reactant are precisely controlled and supplied using a piston pump and a mass flow rate regulator, respectively. In order to supply steam which is known to alleviate the reaction heat of oxidative dehydrogenation and to increase the selectivity for 1,3-butadiene, water in a liquid phase is gasified while being introduced using a mass flow rate regulator, so that the steam is supplied into the reactor. The temperature near the inlet through which the water is introduced is maintained at 300450 C., particularly 350450 C., whereby the introduced water is instantly gasified and mixed with other reactants (C4 mixture and air), and then passes through the catalyst bed.

(23) Among the reactants which react in the presence of the catalyst according to the present invention, the C4 mixture includes 0.550 wt % of n-butane, 4099 wt % of n-butene, and 0.510 wt % of a C4 admixture which does not contain any n-butane and n-butene. The C4 admixture without the n-butane and n-butene includes for example isobutene, cyclobutane, methyl cyclopropane, isobutene, etc.

(24) When an inexpensive C4 mixture or C4 raffinate-3, including n-butene, is subjected to oxidative dehydrogenation using the mixed manganese ferrite coated catalyst according to the present invention, 1,3-butadiene can be produced in high yield from n-butene contained in the reactant.

(25) Also when the support is used in the form of being coated with the mixed manganese ferrite in the present invention, the amount of mixed manganese ferrite which is the active material per the unit volume of the catalyst is small thus making it easy to control the generation of heat upon oxidative dehydrogenation, and the composition and the synthetic route of the catalyst are simple, advantageously ensuring reproducibility.

(26) A better understanding of the present invention may be obtained in light of the following examples which are set forth to illustrate, but are not to be construed as limiting the present invention.

(27) Preparative Example 1

(28) Preparation of Tabletted Mixed Manganese Ferrite Catalyst

(29) In order to prepare a tabletted mixed manganese ferrite catalyst, manganese chloride tetrahydrate (MnCl.sub.2.4H.sub.2O) as a manganese precursor, and iron chloride hexahydrate (FeCl.sub.3.6H.sub.2O) as an iron precursor were used, both of which were well dissolved in distilled water. 198 g of manganese chloride tetrahydrate and 541 g of iron chloride hexahydrate were dissolved in distilled water (1000 ml), mixed and stirred. After sufficient stirring, the complete dissolution of precursors was confirmed, and the precursor aqueous solution was added in droplets to a 3 M sodium hydroxide aqueous solution (6000 ml) at 20 C. at a predetermined rate. This mixture solution was stirred at room temperature for 12 hours using a stirrer so as to be sufficiently stirred, and then allowed to stand at room temperature for 12 hours so as to achieve phase separation. The precipitated solution was washed with a sufficient amount of distilled water, and filtered using a filter under reduced pressure thus obtaining a solid sample which was then dried at 160 C. for 24 hours. The produced solid sample was heat treated in an electric furnace at 650 C. in an air atmosphere for 3 hours, thereby preparing a manganese ferrite catalyst having a mixed phase. The prepared catalyst phase was analyzed using X-ray diffraction under the following conditions. The results are shown in Table 1 below. As shown in Table 1, the catalyst prepared at room temperature was confirmed to be mixed manganese ferrite containing iron oxide (-Fe.sub.2O.sub.3) and manganese iron oxide (MnFeO.sub.3). In order to evaluate the activity thereof, the completed mixed manganese ferrite catalyst was prepared into pellets using tabletting, and milled to a size of 0.91.2 mm.

(30) <Conditions for X-ray Diffraction>

(31) X-ray generator: 3 kW, CuK ray (=1.54056 )

(32) Tube voltage: 40 kV

(33) Tube current: 40 mA

(34) 2-theta measurement range: 5 deg90 deg

(35) Sampling width: 0.02 deg

(36) Injection rate: 5 deg 2-theta/min

(37) Divergence slit: 1 deg

(38) Scattering slit: 1 deg

(39) Receiving slit: 0.15 mm

(40) TABLE-US-00001 TABLE 1 X-ray Diffraction Results of Mixed Manganese Ferrite Catalyst 2-Theta 18.8 MnFeO.sub.3 24.2 -Fe.sub.2O.sub.3 33.22 MnFeO.sub.3 35.66 MnFe.sub.2O.sub.4 40.92 MnFeO.sub.3 45.24 MnFeO.sub.3 49.58 MnFeO.sub.3 54.24 -Fe.sub.2O.sub.3 55.26 MnFeO.sub.3 57.94 MnFe.sub.2O.sub.4 62.58 MnFe.sub.2O.sub.4 64.06 MnFeO.sub.3 66.04 -Fe.sub.2O.sub.3 72.18 MnFe.sub.2O.sub.4 75.8 MnFe.sub.2O.sub.4
Preparative Example 2

(41) Preparation of Extruded Mixed Manganese Ferrite Catalyst

(42) Before the heat treatment was performed in Preparative Example 1, 5 g of dried mixed manganese ferrite, 50 g of boehmite, 30 g of distilled water, and 3 g of nitric acid (60%) were mixed at room temperature. This mixture was placed into an extruder and extruded into a cylindrical form (diameter: 1 mm, length: 10 cm). The extruded mixed manganese ferrite catalyst was placed in an electric furnace, dried at 120 C. for 2 hours, and then heat treated at 650 C. for 3 hours, thus completing a catalyst. The completed catalyst was milled to a size of 0.91.2 mm as in Preparative Example 1.

(43) Preparative Example 3

(44) Preparation of Mixed Manganese Ferrite Coated Silicon Carbide Catalyst

(45) Before the heat treatment was performed in Preparative Example 1, 5 g of dried mixed manganese ferrite, 5 g of boehmite, 50 g of distilled water, and 3 g of nitric acid (60%) were mixed at room temperature. This mixture was added with 50 g of spherical silicon carbide having a diameter of 1 mm, and blended using a roll mixer and dried at 60 C. The dried mixed manganese ferrite coated silicon carbide catalyst was placed in an electric furnace, and then heat treated at 650 C. for 3 hours, thus completing a catalyst.

(46) Example 1

(47) Oxidative Dehydrogenation of C4 Raffinate-3 or C4 Mixture Using Mixed Manganese Ferrite Coated Silicon Carbide Catalyst

(48) Using the mixed manganese ferrite coated silicon carbide catalyst of Preparative Example 3, oxidative dehydrogenation of n-butene was carried out. The specific reaction conditions are described below.

(49) The reactant used for the oxidative dehydrogenation of n-butene was a C4 mixture. The composition thereof is shown in Table 2 below. The C4 mixture was supplied in the form of a gas mixture along with air and steam, and a straight type fixed-bed reactor made of stainless steel was used.

(50) The ratio of reactants was set based on n-butene in the C4 mixture, so that the ratio of n-butene:air:steam was 1:3:20. The steam was obtained by gasifying water in a liquid phase at 350 C., mixed with the other reactants including C4 mixture and air, and then fed into the reactor. The amount of C4 mixture was controlled using a pump, and the amounts of air and steam were regulated using a mass flow rate regulator.

(51) The amount of the catalyst was set so that the WHSV as the flow rate of the reactants was 2.5 h.sup.1 based on n-butene in the C4 mixture. The reaction temperature was maintained so that the temperature of the catalyst bed of the fixed-bed reactor was 400 C. The reaction product was composed of, in addition to the desired 1,3-butadiene, carbon dioxide which is a byproduct of complete oxidation, a cracking byproduct, and an isomerization byproduct, and n-butane contained in the reactant, and was separated and analyzed using gas chromatography. When using the mixed manganese ferrite catalyst for oxidative dehydrogenation of n-butene, the conversion of n-butene, and the selectivity and yield of 1,3-butadiene were calculated according to Equations 1, 2 and 3 below.

(52) $\begin{array}{cc}\mathrm{Conversion}\left(\%\right)=\frac{\mathrm{moles}\mathrm{of}\mathrm{reacted}n\text{-}\mathrm{butene}}{\mathrm{moles}\mathrm{of}\mathrm{fed}n\text{-}\mathrm{butene}}100& \mathrm{Equation}1\\ \mathrm{Selectivity}\left(\%\right)=\frac{\mathrm{moles}\mathrm{of}\mathrm{produced}1,3\text{-}\mathrm{butadiene}}{\mathrm{moles}\mathrm{of}\mathrm{reacted}n\text{-}\mathrm{butene}}100& \mathrm{Equation}2\\ \mathrm{Yield}\left(\%\right)=\frac{\mathrm{moles}\mathrm{of}\mathrm{produced}1,3\text{-}\mathrm{butadiene}}{\mathrm{moles}\mathrm{of}\mathrm{fed}n\text{-}\mathrm{butene}}100& \mathrm{Equation}3\end{array}$

(53) TABLE-US-00002 TABLE 2 Composition of C4 Mixture used as Reactant Composition Molecular Formula Weight % i-Butane C.sub.4H.sub.10 0 n-Butane C.sub.4H.sub.10 26.8 Methyl Cyclopropane C.sub.4H.sub.8 0.1 trans-2-Butene C.sub.4H.sub.8 44.1 Butene-1 C.sub.4H.sub.8 6.6 Isobutylene C.sub.4H.sub.8 0 cis-2-Butene C.sub.4H.sub.8 21.9 Cyclobutane C.sub.4H.sub.8 0.5 i-Pentane C.sub.5H.sub.12 0 Total 100

(54) Test Example 1

(55) Reaction Activities of Mixed Manganese Ferrite Coated Silicon Carbide Catalyst, Extruded Mixed Manganese Ferrite Catalyst and Tabletted Mixed Manganese Ferrite Catalyst

(56) The catalysts of Preparative Examples 13 were applied to the oxidative dehydrogenation of a C4 mixture according to the reaction of Example 1. The results are shown in Table 3 below and FIG. 1. The case where the mixed manganese ferrite coated silicon carbide catalyst was used could result in an 80% conversion of n-butene, a 95.5% selectivity for 1,3-butadiene, a 76.4% yield of 1,3-butadiene, and also changes in temperature of the catalyst bed were 10 C. or less, from which the generation of heat was evaluated to have been efficiently controlled.

(57) TABLE-US-00003 TABLE 3 Preparative n-Butene 1,3-Butadiene 1,3-Butadiene T Example Conversion (%) Selectivity (%) Yield (%) ( C.) 1* 70 91.5 64.1 100 2* 59 92.8 54.8 11 3 80 95.5 76.4 7 *Comparative Preparative Example

(58) As is apparent from Table 3, the extruded mixed manganese ferrite catalyst had low changes in temperature, but exhibited comparatively low conversion and yield because of the small number of active sites of the mixed manganese ferrite exposed so as to function efficiently as an actual catalyst.

(59) In the case of the mixed manganese ferrite coated silicon carbide catalyst obtained by coating silicon carbide having a small specific surface area and a small pore volume with mixed manganese ferrite, the mixed manganese ferrite that is the active material is entirely exposed near the surface of the catalyst and thus can exclusively function as the active sites of the catalyst. Whereas, in the case of the extruded catalyst, active sites are combined with alumina having a large specific surface area and a large pore volume and are present not only on the surface of the catalyst but also in the pores and thus are not exposed and cannot act as active sites. Even when extrusion is performed using manganese ferrite of the same amount, the activity is not exhibited as in the coated catalyst. Therefore, the mixed manganese ferrite coated silicon carbide catalyst can manifest higher conversion or selectivity and can very efficiently control the generation of heat, compared to the mixed manganese ferrite catalysts of comparative preparative examples.

(60) Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that a variety of different modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Accordingly, such modifications, additions and substitutions should also be understood as falling within the scope of the present invention.